Language：English   Publishing type：Research paper (international conference proceedings)  

The current thermal recovery processes of bitumen consume tremendous amounts of water and energy and even emit greenhouse gases (GHGs). As a solution, this study proposes a cold bitumen recovery that adapts the CO2 huff-n-puff process combined with horizontal wells and gravity drainage on the premise that CO2 gas is more soluble in bitumen at lower temperatures. This process generates CO2-based foamy bitumen, introduces swelling phenomenon in the huff stage due to CO2 dissolution in the bitumen phase, and provides foam expansion in the puff stage because of CO2 liberation. Due to pressure differences, gravity, and foam expansion, foamy bitumen is drained into the production well. Therefore, the current study aims to evaluate the potential of this method after the impacts of important parameters on the foam expansion such as temperature, pressure, viscosity, and solubility are investigated. The studied conditions are 2, 3, and 4 MPa of CO2 injection pressure under temperatures of 25, 35, 45, and 55 °C. The results from the adapted CO2 huff-n-puff experiment show that the solubility of CO2 in bitumen increases at higher injecting pressures and lower temperatures. The highest expansion factors which are about 9 were obtained at the highest injecting pressure at 25 and 35 °C followed by the expansion from 3 MPa injecting pressure at 45 and 55 °C. The third place is shared by the injecting pressure of 3 MPa at 25 and 35 °C and injecting pressure of 4 MPa at 45 and 55 °C. The lowest expansion factor was obtained at the lowest injecting pressure at the highest temperature. These peculiar results indicate that temperature, pressure, viscosity, and solubility possess unique roles and strongly influence each other in a certain manner that can either benefit or hinder the foam expansion. It also depicts that with a harmonious and optimal combination of all these parameters, a high expansion of CO2-based foamy bitumen is achievable. Besides, the current highest expansion factor of this study proves that this cold production is theoretically capable of driving bitumen out of the pore spaces even without the assistance of gravity drainage or any form of heating.

DOI： https://doi.org/10.2118/217325-MS

Language：English   Publishing type：Research paper (scientific journal)  

Understanding the inhibitory factors affecting the adsorption of CO2 on low-rank coal from shallow-depth coal seams is essential to identify potential coal seams for CO2 sequestration. The CO2 adsorption capacity of shallow-depth coals was measured at a low pressure on raw and dry coals. The samples were also prepared for organic analyses, scanning electron microscopy analyses, and low-temperature nitrogen adsorption analyses to evaluate the CO2 adsorption and identify the inhibitory factors. An investigation was conducted to determine how CO2 adsorption occurs on coal by fitting experimental data to adsorption isotherm models, followed by analyzing the results based on the statistical analysis. In addition, this study used Henry's law, surface potential, and Gibbs free energy to identify the adsorption inhibitor between CO2 and coal. The CO2 adsorption experiment was conducted on raw coal with a moisture content of 15.18–20.11% and dry coal with no moisture. The experimental data showed that the CO2 adsorption capacity in dry coal was 1.6–1.8 times greater than that in raw coal. A fitting graph between the adsorption data and the isotherm model indicated that CO2 adsorption on coal occurred on monolayers and multilayers under raw and dry conditions. Statistical evaluation of the adsorption isotherm models showed that the Langmuir and Freundlich models aligned more closely to the experimental data. According to this result, low-pressure adsorption of CO2 on coal occurred in monolayers and multilayers under raw and dry conditions. Coal containing a high huminite content had a higher potential for CO2 adsorption, and the drying increased the positive relationship. On the other hand, coal containing high inertinite content inhibited CO2 adsorption onto the coal, but the drying process did not adversely affect CO2 adsorption. Furthermore, coal with high moisture and inertinite content inhibited the affinity, accommodation, and spontaneous CO2 adsorption onto the coal. CO2 adsorption could lead to swelling, but moisture loss opened more sites and micropores, resulting in the swelling effect not closing all micropores in dry coal. Based on these results, coal seams with low moisture and inertinite content are the most promising for CO2 adsorption. Altogether, this study provides an understanding of the percentage of inhibitor factors that affects CO2 adsorption on low-rank coal from shallow depths, which may lead to different CO2 adsorption capacities.

DOI： https://doi.org/10.1021/acsomega.3c04615

Language：English   Publishing type：Research paper (scientific journal)  

To accomplish the net-zero goal, Japan intends to increase its reliance on renewable energies such as solar power (36–38 % in 2030). However, considering the intermittent nature of solar power, the resulting energy must be transformed to a secondary energy carrier such as H2. Japan, on the other hand, is expected to import 20 × 106 tons of H2 each year by 2050. Because of these large volumes, new H2 storage techniques must be developed, in particular underground hydrogen storage (UHS). This paper ranks eight gas reservoirs out of 106 oil and gas fields in four Japanese prefectures regarding their suitability for UHS, and then suggests a H2 injection and withdrawal scheme based on the history of electricity consumption and solar power curtailment. Then, a reservoir simulation study was performed to investigate the effects of factors such as hysteresis, repeated cycles and cushion gas on the performance of these fields. The outcomes for water-drive and volumetric gas reservoirs were compared to better understand the effects of an aquifer on the long-term performance of a gas reservoir when used for UHS. Finally, it was demonstrated that the technology sought for the conversion of H2 back to electricity after withdrawal from a UHS site governs the overall efficiency of a power-H2-power process.

DOI： https://doi.org/10.1016/j.est.2023.107679

Language：English   Publishing type：Research paper (international conference proceedings)  

A method for reducing power peak is to store hydrogen (H2) underground in depleted gas reservoirs (hereafter UHS). In contrast to alternative solutions, like salt caverns or aquifers, the availability of depleted gas reservoirs gives a greater storage capacity. But choosing the right gas field for the UHS and carrying it out are tricky. As a result, the goal of this work is to characterize the UHS in the chosen field and rank Japanese gas fields for it.
To begin with, we ranked and screened potential H2 storage locations in Japan using the Analytical Hierarchy Process (AHP). The best locations for UHS, according to our calculations using the AHP approach, are Sekihara, Kumoide, Katakai, Nakajo, Kubiki, Shiunji, Iwafune-oki (gas), and Minami-Nagaoka. These fields’ high flow capacity, depth, current reservoir pressure, and dip angle are the causes of their elevated position. Then, based on a volumetric reservoir, we studied the H2 injection, storage, and withdrawal capacity at the chosen site in the Niigata Prefecture using the CMG reservoir simulator.
For the first time in Japan, this work offers a framework for evaluating and ranking potential depleted gas reservoirs as a UHS option. It also includes a reservoir simulation study to comprehend the impact of various parameters such as hysteresis trapping, number of injection and withdrawal cycles, and type of cushion gas on the efficiency of H2 storage and withdrawal in a volumetric gas reservoir.

DOI： https://doi.org/10.2118/216987-MS

Language：English   Publishing type：Research paper (scientific journal)  

Underground hydrogen storage (UHS) in depleted hydrocarbon reservoirs is a prospective choice to store enormous volumes of hydrogen (H2). However, these subsurface formations must be able not only to store H2 in an effective and secure manner, but also to produce the required volumes of H2 upon demand. This paper first reviews the critical parameters to be considered for geological analysis and reservoir engineering evaluation of UHS. The formation depth, the interactions of rock-brine-H2, the caprock (seal) and well integrity are the most prominent parameters as far as UHS is concerned. In respect of these critical parameters, tentative H2 storage is screened from the existing gas storage fields in the Niigata prefecture of Japan, and it was revealed that the Sekihara gas field is a suitable candidate for UHS with a storage capacity of 2.06 × 108 m3 and a depth of 1000 m. Then, a series of numerical simulations utilizing CMG software was conducted to find out the extent to which critical parameters alter H2 storage capacity. The results demonstrated that this field, with a recovery factor of 82.7% in the sixth cycle of production is a prospective site for H2 storage.

DOI： https://doi.org/10.1016/j.ijhydene.2022.12.108

Language：English   Publishing type：Research paper (international conference proceedings)  

The foam improves heterogeneity of permeability in oil reservoir and contributes to enhancing oil recovery. Both surfactant and gas are alternatingly injected into oil reservoir in foam EOR, therefore, it has several challenges: high cost of surfactant, formation of precipitation with bivalent cations, adsorption of surfactant on reservoir rock, etc. This study proposes the microbial foam EOR which overcomes those challenges by having microorganism generate foam in-situ. We have found an ability of a microorganism belonging to Pseudomonas aeruginosa to generate foam under anaerobic conditions. This study investigated the source materials constructing the foam and capacity of the foam to improve the heterogeneity of the permeability.
The challenges of our study are the reproducibility of the foam generation and the foam stability. This study therefore examined the source materials of the foam to understand the mechanisms of the foam generation. We focused on protein, which has been suggested as a possible component of the foam in our previous studies, and examined the relationship between the amount of foam generated by P. aeruginosa and the concentration of protein in its culture solution. As a result, a positive correlation was found between them. This result indicates that the foam generated by P. aeruginosa is composed of the protein produced by the microorganism.
Next, the performance of the foam decreasing permeability of high permeability porous media was evaluated through sand pack flooding experiment. P. aeruginosa was injected into a sand pack and cultivated in-situ. The post-flush water was injected into the sand pack after three days’ in-situ cultivation to measure the permeability. As a result, the permeability of the sand pack was successfully decreased to half after the cultivation. The permeability of a sand pack in which P. aeruginosa was injected with culture medium and in-situ cultivated was successfully decreased to half of initial . The efflux of bacterial cells of P. aeruginosa was detected after injecting 1.3 pore volumes of postflush water, which shows that the postflush water flowed through areas other than the area where P. aeruginosa grew and produced the foam. These results indicate that the foam produced in-situ by P. aeruginosa is effective for improving the heterogeneity of permeability in oil reservoir.
This EOR can be operated at low cost without expensive chemicals. Because the foam produced by P. aeruginosa is induced by proteins, the precipitation will not be formed in oil reservoir. The stability of protein-induced foam is higher than that of surfactant-induced foam in the presence of oil or high saline conditions. The microbial foam EOR therefore has high potential improving the heterogeneity of permeability in oil reservoir more effectively than the conventional foam EOR.

DOI： https://doi.org/10.2118/210696-MS

Language：English   Publishing type：Research paper (international conference proceedings)  

Swelling control is an elaborated balancing of solid-liquid ratios in the mud, influencing crucial physio-chemical features. Mechanical swelling control methods showing limitations drove recent researchers to consider chemical agents, including polyvinyl alcohol (PVOH). PVOH is known to have a swelling ability to improve mud rheology. The present study investigates the synergy of PVOH and Bentonite in an aqueous environment by analyzing the effluents samples. Three types of PVOH were selected: a standard PVOH and two modified PVOHs (a non-ionic group PVOH and a cationic group PVOH-3 attached to the carbon backbone. Except for the control sample (sample without polymer), PVOHs were added to different mud samples at ranging concentrations of 0.1 wt.% to 0.5 wt.%; each has a bulk volume of 400 ml. Each mud sample was filtrated at room temperature under an applied pressure of 1.28 MPa for 5 hours. The samples' effluents were then analyzed for polymer adsorption. Preliminary filtration tests revealed further effluent production reduction with increased PVOH concentration. Compared to the control sample, samples containing standards PVOH-1, Non-ionic PVOH-2, and Cationic PVOH-3, respectively, had their mud cake mass increase of 48%, 36%, and 38%, while respectively having filtrate recovery reduction of 21%, 19%, and 43%. Adsorption tests showed mud swelling owes primarily to hydrogen bonding which is counteracted by the presence of a charged group. Mud swelling is, therefore, dependent on the rate of hydrogen bounding in a system.

DOI： https://doi.org/10.2118/210694-MS

Language：English   Publishing type：Research paper (scientific journal)  

In this study, the CO2 adsorption capacity was measured on Indonesian low-rank coals in the raw and dry conditions in powder and block states using different coal sample preparation to estimate CO2 sequestration and storage potential. Coal sample specimens were taken from three different areas in the South Sumatra Basin, Indonesia. The adsorption experiments were performed using the volumetric method at a temperature of 318.15 K and pressure up to 3 MPa. The CO2 excess adsorption capacity of powder coal is always higher than block coal. Moreover, decreasing moisture content by the drying process increases CO2 adsorption capacity on coal. Based on fitted CO2 adsorption experimental data with the Langmuir and Freundlich isotherm model, the adsorption occurs on monolayer and multilayer at various conditions. Langmuir volume capacity and pressure show drying and crushing process increased adsorption capacity. However, the drying process affects more the capability of coal to adsorb CO2 than the powdered sample, especially in low-rank coal. It was also observed adsorption capacity is directly proportional to huminite content in the coal. Due to lower moisture and higher huminite contents, the dried WB coal powder had the highest CO2 adsorption capacity over the other coal samples in similar sample conditions. Altogether, this study may provide a better understanding in CO2 adsorption on low-rank coal with different coal sample preparation resulting in different CO2 adsorption capacity.

DOI： https://doi.org/10.1007/s13202-022-01569-z

Language：English   Publishing type：Research paper (international conference proceedings)  

Carbon dioxide (CO2) gas injection into depleted oil reservoirs is a promising approach to achieve the goal of a neutral carbon society. However, the heterogeneity of formation generally challenges the oil recovery efficiency. The CO2 gas injection preferably flows in the high permeability zone and leaves behind the remaining oil in the lower permeability region. This study presented a new CO2-Colloidal Gas Aphrons fluid to restrict fluid flow in the high permeability zone, and increase swept volume in the low permeability zone. We conducted dual parallel sandpacks with different permeabilities models to evaluate the plugging ability and oil recovery improvement of CO2-CGAs injection in heterogeneous porous media. The results reveal that CO2-CGAs can block the pore throat in the high permeability sandpack and change the flow direction to the low permeability sandpack. Overall, the sweep efficiency in the low permeability region was increased significantly, which led to an improvement in the total oil recovery factor by 39 %.

DOI： https://doi.org/10.3997/2214-4609.202210546

Language：English   Publishing type：Research paper (scientific journal)  

To further improve carbon dioxide enhanced oil recovery CO2-EOR efficiency in heterogeneous reservoirs, the use of CO2 microbubbles as a temporary blocking agent is attracting widespread interest due to their significant stability. This study aims to investigate the plugging performance of CO2 microbubbles in both homogeneous and heterogeneous porous media through a series of sandpack experiments. First of all, CO2 microbubble fluids were generated by stirring CO2 gas diffused into polymer (Xanthan gum (XG)) and surfactant (Sodium dodecyl sulfate (SDS)) solution with different gas: liquid ratios. Then, CO2 microbubbles fluids were injected into single-core and dual-core sandpack systems. The results show that the rheological behaviors of CO2 microbubble fluids in this study were followed the Power-law model at room temperature. The apparent viscosity of CO2 microbubble fluid increased as the gas: liquid ratio increased. CO2 microbubbles could block pore throat due to the “Jamin effect” and increase the resistance in porous media. The blocking ability of CO2 microbubbles reached an optimal value at the gas:liquid ratio of 20% in the homogeneous porous media. Moreover, the selective pugging ability of CO2 microbubbles in dual-core sandpack tests was significant. CO2 microbubbles exhibited a good flow control profile in the high permeability region and flexibility to flow over the pore constrictions in the low permeability region, leading to an ultimate fractional flow proportion (50%:50%) in the dual-core sandpack model with a permeability differential of 1.0:2.0 darcy. The fractional flow ratio was considerable compared with a polymer injection. At the higher heterogeneity of porous media (0.5:2.0 darcy), CO2 microbubble fluid could still establish a good swept performance. This makes CO2 microbubble fluid injection a promising candidate for heterogeneous reservoirs where conventional CO2 flooding processes have limited ability. This finding would be helpful in developing the utilization of CO2 microbubbles in EOR operation by better understanding their plugging mechanism in porous media.

DOI： https://doi.org/10.1016/j.petrol.2022.110187

Repository Public URL： http://hdl.handle.net/2324/4785198

Language：English   Publishing type：Research paper (scientific journal)  

This study proposed a novel foam EOR technique using Pseudomonas aeruginosa to generate the foam and investigated the potential of the microbial foam EOR to modify the permeability of a high-permeability porous system. We investigated oxygen nanobubble, carbon dioxide nanobubble and ferrous sulfate concentrations to discover the optimal levels for activating the foam generation of the microorganism through cultivation experiments. We also clarified the behavior of the microbial foam generation and the bioproducts that contribute to the foam generation. The potential of the foam to decrease the permeability of high-permeability porous systems was evaluated through flooding experiments using sand pack cores. The foam generation became more active with the increase in the number of nanobubbles, while there was an optimal concentration of ferrous sulfate for foam generation. The foam was identified as being induced by the proteins produced by the microorganism, which can be expected to bring about several advantages over surfactant-induced foam. The foam successfully decreased the permeability of high-permeability sand pack cores to half of their initial levels. These results demonstrate that the microbial foam EOR has the potential to decrease the permeability of high-permeability porous systems and improve the permeability heterogeneity in oil reservoirs.

DOI： https://doi.org/10.3390/en15072344

Repository Public URL： http://hdl.handle.net/2324/4785194

Language：English   Publishing type：Research paper (scientific journal)  

Enhanced coal bed methane recovery using gas injection can provide increased methane extraction depending on the characteristics of the coal and the gas that is used. Accurate prediction of the extent of gas adsorption by coal are therefore important. Both experimental methods and modeling have been used to assess gas adsorption and its effects, including volumetric and gravimetric techniques, as well as the Ono–Kondo model and other numerical simulations. Thermodynamic parameters may be used to model adsorption on coal surfaces while adsorption isotherms can be used to predict adsorption on coal pores. In addition, density functional theory and grand canonical Monte Carlo methods may be employed. Complementary analytical techniques include Fourier transform infrared, Raman spectroscopy, XR diffraction, and 13C nuclear magnetic resonance spectroscopy. This review summarizes the cutting-edge research concerning the adsorption of CO2, N2, or mixture gas onto coal surfaces and into coal pores based on both experimental studies and simulations.

DOI： https://doi.org/10.3390/gases2010001

Language：English   Publishing type：Research paper (scientific journal)  

The leakage of methane from the subsurface on the coalfield or natural gas field invariably becomes an important issue nowadays. In notable addition, materials such as activated carbon, zeolites, and Porapak have been successfully identified as adsorbents. Those adsorbents could adsorb methane at atmospheric pressure and room temperature. Therefore, in this scholarly study, a new method using adsorbents to detect points of methane leakage that can cover a wide-scale area was developed. In the beginning, the most capable adsorbent should be determined by quantifying adsorbed methane amount. Furthermore, checking the possibility of adsorption in the column diffusion and desorption method of adsorbents is equally necessary. The most capable adsorbent was activated carbon (AC), which can adsorb 1.187 × 10−3 mg-CH4/g-AC. Hereinafter, activated carbon successfully can adsorb methane through column diffusion, which simulates the situation of on-site measurement. The specific amount of adsorbed methane when the initial concentrations of CH4 in a bag were 200 ppm, 100 ppm, and 50 ppm was found to be 0.818 × 10−3 mg-CH4/g-AC, 0.397 × 10−3 mg-CH4/g-AC, 0.161 × 10−3 mg-CH4/g-AC, respectively. Desorption of activated carbon analysis shows that methane concentration increases during an hour in the temperature bath under 80 °C. In conclusion, soil methane leakage points can be detected using activated carbon by identifying the observed methane concentration increase.

DOI： https://doi.org/10.3390/methane1010003

Repository Public URL： http://hdl.handle.net/2324/4785191

Language：English   Publishing type：Research paper (international conference proceedings)  

This study proposed a novel foam EOR technique using Pseudomonas aeruginosa to generate the foam and investigated the potential of the microbial foam EOR to modify the permeability of a high-permeability porous system. We investigated oxygen nanobubble, carbon dioxide nanobubble and ferrous sulfate concentrations to discover the optimal levels for activating the foam generation of the microorganism through cultivation experiments. We also clarified the behavior of the microbial foam generation and the bioproducts that contribute to the foam generation. The potential of the foam to decrease the permeability of high-permeability porous systems was evaluated through flooding experiments using sand pack cores. The foam generation became more active with the increase in the number of nanobubbles, while there was an optimal concentration of ferrous sulfate for foam generation. The foam was identified as being induced by the proteins produced by the microorganism, which can be expected to bring about several advantages over surfactant-induced foam. The foam successfully decreased the permeability of high-permeability sand pack cores to half of their initial levels. These results demonstrate that the microbial foam EOR has the potential to decrease the permeability of high-permeability porous systems and improve the permeability heterogeneity in oil reservoirs.

Language：English   Publishing type：Research paper (scientific journal)  

Fluids incorporating carbon dioxide (CO2) microbubbles have been utilized to promote enhanced oil recovery from hydrocarbon reservoirs. The performance of such fluids in porous media is greatly affected by both the bubble size and stability. On this basis, the present study evaluated the effects of varying the concentrations of a xanthan gum (XG) polymer, a surfactant (sodium dodecyl sulfate: SDS) and sodium chloride (NaCl) on both the stability and bubble size distribution (BSD) of CO2 microbubbles. CO2 microbubble dispersions were prepared using a high-speed homogenizer in conjunction with the diffusion of gaseous CO2 through aqueous solutions. The stability of each dispersion was ascertained using a drainage test, while the BSD was determined by optical microscopy and fitted to either normal, log-normal or Weibull functions. The results showed that a Weibull distribution gave the most accurate fit for all experimental data. Increases in either the SDS or XG polymer concentration were found to decrease the microbubble size. However, these same changes increased the microbubble stability as a consequence of structural enhancement. The addition of NaCl up to a concentration of 10 g/L (10 g/1000g) decreased the average bubble size by approximately 2.7%. Stability was also reduced as the NaCl concentration was increased because of the gravitational effect and coalescence

DOI： https://doi.org/10.1080/01932691.2021.1974873

Repository Public URL： http://hdl.handle.net/2324/4785197

Language：English   Publishing type：Research paper (scientific journal)  

The effect of nanobubbles on anaerobic growth and metabolism of Pseudomonas aeruginosa was investigated. P. aeruginosa grew earlier in the culture medium containing nanobubbles and the bacterial cell concentration in that culture medium was increased a few times higher compared to the medium without nanobubbles under anaerobic condition. Both gas and protein, which are the metabolites of P. aeruginosa, were remarkably produced in the culture medium containing nanobubbles whereas those metabolites were little detected in the medium without nanobubbles, indicating nanobubbles activated anaerobic growth and metabolism of P. aeruginosa. The carbon dioxide nanobubbles came to be positively charged by adsorbing cations and delivered ferrous ions, one of the trace essential elements for bacterial growth, to the microbial cells, which activated the growth and metabolism of P. aeruginosa. The oxygen nanobubbles activated the activities of P. aeruginosa as an oxygen source

DOI： https://doi.org/10.1038/s41598-021-96503-4

Repository Public URL： http://hdl.handle.net/2324/4705310

Language：English   Publishing type：Research paper (scientific journal)  

Residual Oil Zones (ROZs) become potential formations for Carbon Capture, Utilization, and Storage (CCUS). Although the growing attention in ROZs, there is a lack of studies to propose the fast tool for evaluating the performance of a CO2 injection process. In this paper, we introduce the application of artificial neural network (ANN) for predicting the oil recovery and CO2 storage capacity in ROZs. The uncertainties parameters, including the geological factors and well operations, were used for generating the training database. Then, a total of 351 numerical samples were simulated and created the Cumulative oil production, Cumulative CO2 storage, and Cumulative CO2 retained. The results indicated that the developed ANN model had an excellent prediction performance with a high correlation coefficient (R2) was over 0.98 on comparing with objective values, and the total root mean square error of less than 2%. Also, the accuracy and stability of ANN models were validated for five real ROZs in the Permian Basin. The predictive results were an excellent agreement between ANN predictions and field report data. These results indicated that the ANN model could predict the CO2 storage and oil recovery with high accuracy, and it can be applied as a robust tool to determine the feasibility in the early stage of CCUS in ROZs. Finally, the prospective application of the developed ANN model was assessed by optimization CO2-EOR and storage projects. The developed ANN models reduced the computational time for the optimization process in ROZs.

DOI： https://doi.org/10.1038/s41598-020-73931-2

Language：English   Publishing type：Research paper (scientific journal)  

CO2 microbubbles have recently been used in enhanced oil recovery for blocking the high permeability zone in heterogeneous reservoirs. Microbubbles are colloidal gas aphrons stabilized by thick shells of polymer and surfactant. The stability of CO2 microbubbles plays an important role in improving the performance of enhanced oil recovery. In this study, a new class of design of experiment (DOE)—definitive screening design (DSD) was employed to investigate the effect of five quantitative parameters: xanthan gum polymer concentration, sodium dodecyl sulfate surfactant concentration, salinity, stirring time, and stirring rate. This is a three-level design that required only 11 experimental runs. The results suggest that DSD successfully evaluated how various parameters contribute to CO2 microbubble stability. The definitive screening design revealed a polynomial regression model has ability to estimate the main effect factor, two-factor interactions and pure-quadratic effect of factors with high determination coefficients for its smaller number of experiments compared to traditional design of experiment approach. The experimental results showed that the stability depend primarily on xanthan gum polymer concentration. It was also found that the stability of CO2 microbubbles increases at a higher sodium dodecyl sulfate surfactant concentration and stirring rate, but decreases with increasing salinity. In addition, several interactions are presented to be significant including the polymer–salinity interaction, surfactant–salinity interaction and stirring rate–salinity interaction.

DOI： https://doi.org/10.3390/colloids4020026

Language：English   Publishing type：Research paper (scientific journal)  

This paper examined the reservoir souring induced by the sulfate-reducing bacteria (SRB) inhabiting the reservoir brine of an oilfield in Japan. Although the concentration of sulfate of the reservoir brine was lower than that of seawater, which often was injected into oil reservoir and induced the reservoir souring, the SRB inhabiting the reservoir brine generated hydrogen sulfide (H2S) by using sulfate and an electron donor in the reservoir brine. This paper therefore developed a numerical simulator predicting the reservoir souring in the reservoir into which the reservoir brine was injected. The results of the simulation suggested that severe reservoir souring was not induced by the brine injection; however, the SRB grew and generated H2S around the injection well where temperature was decreased by injected brine whose temperature was lower than that of formation water. In particular, H2S was actively generated in the mixing zone between the injection water and formation water, which contained a high level of the electron donor. Furthermore, the results of numerical simulation suggested that the reservoir souring could be prevented more surely by sterilizing the SRB in the injection brine, heating up the injection brine to 50 °C, or reducing sulfate in the injection brine.

DOI： https://doi.org/10.3390/su12114603

Language：English   Publishing type：Research paper (scientific journal)  

Surfactin, which is an anionic bio-surfactant, can be effective for enhanced oil recovery because it decreases interfacial tension between oil and water. However, it forms precipitation by binding with divalent cations. This study examined the countermeasure to prevent surfactin from forming precipitation for applying it to enhanced oil recovery. Alcohols, chelating agents, a cationic surfactant and an ion capturing substance were selected as the candidates for inhibiting surfactin from forming precipitation. Citric acid and trisodium citrate were selected as promising candidates through the measurements of turbidity of the mixture of the candidate, surfactin and calcium ions. Those chemicals also had a function as a co-surfactant for surfactin. However, the permeability of the Berea sandstone core into which the solution containing surfactin and trisodium citrate was injected was decreased significantly, whereas citric acid could be injected into the core without significant permeability reduction. Citric acid was therefore selected as the best inhibitor and subjected to the core flooding experiments. High enhancement of oil recovery of 9.4% (vs. original oil in place (OOIP)) was obtained and pressure drop was not increased during the injection of surfactin and citric acid. Those results suggest that citric acid has a dual role as the binding inhibitor and co-surfactant for surfactin.

DOI： https://doi.org/10.3390/en13102430

Language：English   Publishing type：Research paper (scientific journal)  

This study presents a robust optimization workflow to determine the optimal water alternating gas (WAG) process for CO₂ sequestration in a heterogeneous fluvial sandstone reservoir. As depicted in this study, WAG injection could enhance CO₂ residual and solubility trapping based on an integrated modeling workflow. First, continuous CO₂ injection and WAG were compared to demonstrate the efficiency of the WAG process for CO₂ trapping enhancement. To achieve this while highlighting the impact of reservoir heterogeneity, 200 geological realizations were generated considering a wide range of plausible geological conditions. The ranking of these realizations was performed by quantifying the CO₂ cumulative injection (P10, P50, and P90 realizations) that represent the overall geological uncertainties. Then, an innovative robust workflow was used Artificial Intelligence optimizer to determine the optimal solution for CO₂ trapping. For comparison, a nominal optimization workflow of P50 realization was also conducted. The proposed robust optimization workflow resulted in higher CO₂ trapping than the nominal optimization workflow. Thus, this study demonstrates a fast and reliable workflow that can accurately represent for optimization the cycle length injection in the WAG process under geological uncertainties.

DOI： 10.1016/j.jngse.2020.103208

Repository Public URL： http://hdl.handle.net/2324/4354920

Language：English   Publishing type：Research paper (scientific journal)  

This study is intended to expand the scope of microbial enhanced oil recovery (MEOR) simulation studies from 1D to field scale focussing on fluid viscosity variation and heterogeneity that lacks in most MEOR studies. Hence, we developed a model that incorporates: (1) reservoir simulation of microbe-induced oil viscosity reduction and (2) field-scale simulation and robust geological uncertainty workflow considering the influence of well placement. Sequential Gaussian simulation, co-kriging and artificial neural network were used for the petrophysical modelling prior to field-scale modelling. As per this study, the water viscosity increased from 0.5 to 1.72 cP after the microbe growth and increased biomass/biofilm. Also, we investigated the effect of the various component compositions and reaction frequencies on the oil viscosity and possibly oil recovery. For instance, the fraction of the initial CO₂ in the oil phase (originally in the reservoir) was varied from 0.000148 to 0.005 to promote the reactions, and more light components were produced. It can be observed that the viscosity of oil reduced considerably after 90 days of MEOR operation from an initial 7.1–7.07 cP and 6.40 cP, respectively. Also, assessing the pre- and post-MEOR oil production rate, we witnessed two main typical MEOR field responses: sweeping effect and radial colonization occurring at the start and tail end of the MEOR process, respectively. MEOR oil recovery factors varied from 28.2 to 44.9% OOIP for the various 200 realizations. Since the well placement was the same for all realizations, the difference in the permeability distribution amongst the realizations affected the microbes’ transport and subsequent interaction with nutrient during injection and transport.

DOI： 10.1007/s13202-020-00852-1

Language：English   Publishing type：Research paper (scientific journal)  

Carbon dioxide (CO₂) capture, utilization, and storage (CCUS) have been proposed as a possible technique to mitigate climate change. In this vein, CO₂ storage through enhanced oil recovery (EOR) in depleted hydrocarbon reservoirs is touted as a most effective approach because it synergistically increases oil production and enables permanent sequestration into the reservoirs. However, the construction of a reasonable 3D geological model for this storage reservoir is a major challenge. Thus, this study presents an efficient workflow for constructing an accurate geological model for the evaluation of CO₂ storage capacity in a fractured basement reservoir in the Cuu Long Basin, Vietnam. Artificial neural network (ANN) has been used to predict porosity and permeability values through seismic attributes and well log data. The predicted values were selected using high correlation factors with well log data. Subsequently, the Sequential Gaussian Simulation and co-kriging methods were applied to generate a 3D static geological model by using azimuth and dip parameters. Finally, drill stem test matching was performed to validate the accuracy of the porosity and permeability models through dynamic simulation. A validation 3D reservoir model, which integrates geophysical, geological, and engineering data from fractured basement formation in Cuu Long Basin, was further constructed to calculate theoretical CO₂ storage capacity. As a result, the calculated storage capacity for the fractured basement reservoir ranged from 7.02 to 99.5 million metric tons. These estimated results demonstrate that fractured basement reservoir has a combined potential for CO₂ storage and EOR in the Cuu Long Basin.

DOI： 10.1016/j.ijggc.2019.102826

Repository Public URL： http://hdl.handle.net/2324/4354919

Language：English   Publishing type：Research paper (scientific journal)  

The CO₂ is regarded to be an excellent solvent for miscible flooding. However, it is still facing a main problem which is the high mobility. Microbubbles with their unique characters offer some advantages for CO₂ EOR application. Different pore throat size filters were used to generate different dominant sizes of microbubbles that were injected into sandpacks under tertiary condition. Microscopic analysis was carried out to visualize the presence, stability and behavior of microbubbles inside the solution and porous media. The microbubbles with a dominant size of 10–50 µm showed additional 26.38% of oil recovery, showing their advantages over a larger dominant size of microbubbles up to 5.28% of oil recovery. The injection with larger microbubbles with a dominant size of 70–150 µm showed 27.5% of higher injection pressure than with a smaller dominant size of microbubbles, showing their advantage in gas blocking ability. In the heterogeneous porous media experiment, the recovery volume ratio between low- and high-permeability sandpacks was increased from 1:57 during water flooding to 1:4 during the CO₂ microbubble injection with 74.65% of additional recovery from a low-permeability zone, showing the microbubble gas blocking capability to change the flow pattern inside heterogeneous porous media.

DOI： https://doi.org/10.1007/s13202-019-0680-3

Language：English   Publishing type：Research paper (scientific journal)  

Iodide-oxidizing bacteria (IOB) oxidize iodide into iodine and triiodide which can be utilized for gold dissolution. IOB can be therefore useful for gold leaching. This study examined the impact of incubation conditions such as concentration of the nutrient and iodide, initial bacterial cell number, incubation temperature, and shaking condition on the performance of the gold dissolution through the experiments incubating IOB in the culture medium containing the marine broth, potassium iodide and gold ore. The minimum necessary concentration of marine broth and potassium iodide for the complete gold dissolution were determined to be 18.7 g/L and 10.9 g/L respectively. The initial bacterial cell number had no effect on gold dissolution when it was 1×10⁴ cells/mL or higher. Gold leaching with IOB should be operated under a temperature range of 30–35 °C, which was the optimal temperature range for IOB. The bacterial growth rate under shaking conditions was three times faster than that under static conditions. Shaking incubation effectively shortened the contact time compared to the static incubation. According to the pH and redox potential of the culture solution, the stable gold complex in the culture solution of this study could be designated as gold (I) diiodide.

DOI： https://doi.org/10.3390/min9050274

Language：English   Publishing type：Research paper (scientific journal)  

This study proposed a new geological modelling procedure for CO₂ storage assessment in offshore Vietnam by integrating artificial neural networks, cokriging and object-based methods. These methods could solve the limitations of well data that have not been addressed by conventional modelling. Petrel software was used to build a geological model for comparing conventional and new modelling workflows. Moreover, the Eclipse simulator was used for CO₂ injection scenarios on the geological model of two workflows. The simulation results of CO₂ flow response corroborated that the new modelling workflow by showing better performance than the traditional modelling workflow. Thus, in the selected CO₂ storage sites, the new modelling workflow is preferred because it strongly enhances the CO₂ storage evaluation.

DOI： https://doi.org/10.1080/15567036.2019.1604865

Language：English   Publishing type：Research paper (scientific journal)  

Gold leaching from ore using iodide-iodine mixtures is an alternative to gold cyanidation. this study evaluated the ability of iodide-oxidising bacteria to solubilise gold from ore that was mainly composed of gold, pyrite, galena, and chalcopyrite. eight bacterial strains were successfully isolated from brine. Those strains were incubated in a liquid culture medium containing ore with a gold content of 0.26 wt.% and pulp density of 3.3 w/v% to evaluate their abilities to mediate the dissolution of gold. The gold was solubilised completely within 30 days of incubation in the iodine-iodide lixiviant solution generated by three bacterial strains. One strain, in particular, completed the dissolution of gold within 5 days of incubation and was identified as a member of the genus Roseovarius. thus, the possibility of bacterial gold leaching using iodide-oxidising bacteria was successfully demonstrated. Bioleaching gold with iodide would likely be more environmentally sustainable than traditional cyanide leaching. Further research is required to evaluate the techno-economic feasibility of this approach.

DOI： https://doi.org/10.1038/s41598-019-41004-8

Language：English   Publishing type：Research paper (scientific journal)  

The present study investigated the ability of a thermophilic anaerobic microbe (herein coded as AR80) for MEOR with the further objective to quantify the uncertainty of production forecast in terms of the cumulative probability distribution. A series of core flood experiments conducted in water-flooded Berea sandstone showed that up to 51% of initial oil-in-place was recovered when the plugs were treated with AR80 and shut-in for 14 days. Mainly, the oil recovery mechanisms were attributed to viscosity enhancement, wettability changes, permeability and flow effects. Matching the laboratory data using artificial intelligence: the optimized cumulative oil recovery could be achieved at an enthalpy of 894.2 J/gmol, Arrhenius frequency of 8.3, residual oil saturation of 20%, log of capillary number at microbe flooding stage of −1.26, and also depicted a history match error less than 3%. Therefrom, a sensitivity analysis conducted on reservoir shut-in period effect on oil recovery revealed that a relatively shorter shut-in period is recommended to warrant early incremental oil recovery effect for economical purposes. In addition, MEOR could enhance the oil recovery significantly if a larger capillary number (between 10⁻⁵ and 10^−3.5) is attained. Per probabilistic estimation, MEOR could sustain already water-flooded well for a set period of time. This study showed that there is a 20% frequency of increasing the oil recovery by above 20% when a mature water-flooded reservoir is further flooded with AR80 for 2 additional years. Lastly, it was demonstrated herein that increasing the nutrient (yeast extract) concentration (from 0.1 to 1% weight) had less or no significant effect on the oil viscosity and subsequent recovery.

DOI： 10.1016/j.petrol.2018.08.005

Repository Public URL： http://hdl.handle.net/2324/1937165

Language：English   Publishing type：Research paper (scientific journal)  

We performed kinetic studies of the growth of sulfate-reducing bacteria (SRB) indigenous to the water in an oilfield in Japan. The SRB growth was most active in injection water supplemented with ethanol; therefore, the SRB inhabiting the injection water of the reservoir were assumed to grow predominantly by assimilating sulfate and ethanol and generating H2S. Based on this mechanism and the results of incubation experiments in the injection water, we derived numerical models that calculate the growth rate and H2S generation of the SRB under three variables (temperature, sulfate concentration, and ethanol concentration).

DOI： https://doi.org/10.1080/10916466.2018.1496102

Language：English   Publishing type：Research paper (scientific journal)  

Primarily, most oil wells in the West Africa transform region are produced using water or water alternating gas. This is believed to be unsustainable going forward. Also, though the region contributes less to global greenhouse emission, global warming effects in the region cannot be undermined. Microbial enhanced oil recovery (MEOR) has been proven worldwide to be environmentally friendly as well as less costly to develop. Despite the advantages of MEOR over other oil recovery methods, operating companies in the region are yet to apply this bespoke technology. Therefore, this study reviews the potential applicability of MEOR process to West African oil fields comparing the geology and physiochemical properties to major oil fields in South America (where MEOR has been previously applied). Applying MEOR in the region could be a major step towards improving production of new oil wells and enhancing sustainability of old oil wells.

DOI： http://dx.doi.org/10.1504/IJPE.2018.093164

Language：English   Publishing type：Research paper (scientific journal)  

This research simulated oil recovery with emphasis on oil viscosity reduction by direct microbe action and metabolites; predicted hydrogeochemical reactions involved with nutrient – brine interaction in reservoirs. PHREEQC was used to simulate reactions between the reservoir brine and nutrient minus microbe. Hitherto, UTCHEM was employed for the enhancement of oil viscosity by assuming production of gases and by the direct microbe action. The model depicted the precipitation of calcite plus dissolution of k-feldspar combined with the evolution of CO2 and CH4 influenced by temperature and pH. Oil recovery was directly proportional to salinity reduction and increasing nutrient concentration.

DOI： 10.1080/10916466.2018.1463253

Language：English   Publishing type：Research paper (scientific journal)  

Nutrition injection in Microbial Enhanced Oil Recovery (MEOR) process might stimulate not only desirable microorganisms but also the undesirable ones. Therefore, studying the properties of bacterial community in reservoir prior to field test is a critical step in MEOR process. In this study, bacterial communities from high thermic and low salinity reservoirs located in Japan, China and Indonesia were characterized by 16S rDNA sequence analysis. Bacterial genomic DNAs were extracted from produced water samples and their sequences were evaluated by genetic fingerprinting based approach. PCR-DGGE analyses showed multiple bands in all produced water samples which indicated high bacterial diversities. Sequences identified in this study were mainly related to only five phyla, i.e., Bacteroidetes, Thermotogae, Defferibacteres, Firmicutes and Proteobacteria, suggesting that phylotype richness is low in oil reservoirs. One sequence of Bacteriodetes-affiliated bacteria which showed 99% similarity with Bacteriodales bacterium 5bM was retrieved from DGGE results of all oilfields. This result showed that, Bacteriodetes can grow well in Indonesia, Japan and China oilfield, making it the best bacterial candidate for MEOR field test. Results showed in this study revealed that finger printing is a considerable technique for microbial screening prior to MEOR field test application.

DOI： 10.3923/jeasci.2018.4104.4112

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

We studied on the availability of residue of squeezed beer yeast whose principal component is yeast cell wall for enhanced oil recovery as an interfacial tension reducer. The cell wall solution was hydrothermally treated in order to elute amphiphilic substances such as phospholipids, proteins, and fatty acids from the cell wall to the solution under different conditions such as concentration of the cell wall, temperature and time of the hydrothermal treatment, and salinity. The cell wall solution which was hydrothermally treated with crude oil was also applied to the measurement of interfacial tension between the solution and crude oil. The interfacial tension was reduced with decrease in salinity and increase in concentration of the cell wall and temperature of the hydrothermal treatment. The time of hydrothermal treatment didn't have much influence on the interfacial tension reduction. The capability of the cell wall solution which had been hydrothermally treated with crude oil to reduce the interfacial tension became larger than that of the cell wall solution which had been hydrothermally treated without crude oil. It was suggested that those interfacial tension reductions were brought by phospholipids and proteins eluted from the cell wall. Core flooding experiments were carried out by injecting the cell wall solution which had been hydrothermally treated with and without crude oil after the water flooding as the primary oil recovery. 2.0% and 1.2% of original oil in place was additionally recovered by injecting the cell wall solution which had been hydrothermally treated with and without crude oil respectively. These results support an advantage of process injecting the cell wall solution without hydrothermal treatment into high temperature oil reservoir. The injection of the cell wall solution can be a promising EOR which has both high cost performance and low environmental load.

DOI： 10.4172/2157-7463.1000329

Language：English   Publishing type：Research paper (scientific journal)  

The Rembang area is a well-known prospective region for oil and gas exploration in Northeast Java, Indonesia. In this study, the reservoir characteristics of the Ngrayong Sandstone were investigated based on outcrops in the Rembang area. Petrological, mineralogical, petrophysical and sedimentological facies analyses were conducted. These sandstones are grain- and matrix supported, and composed of very fine to medium, sub-angular to poorly-rounded, moderately to very well-sorted sand grains. These sandstones are mainly composed of quartz, orthoclase, plagioclase, and micas with minor amounts of clay minerals, and therefore are predominantly classified as sub-lithic arenite and sub-felds pathicarenite. Petrographic observations and grain size data indicate that these sandstones are texturally quite mature, based on their good -sorting and the occurrence of minor amounts of matrix clays. Common clays in the samples include illite, smectite, kaolinite, and gibbsite. The porosity of the Ngrayong sandstones ranges from 25.97% to 40.21%, and the permeability ranges from 94.6 to 3385 millidarcies. Thus, these sandstones exhibit well to excellent reservoir qualities. Eight lithofacies were identified from five measured stratigraphic sections, and are dominated by foreshore and tide-dominated shoreface facies. The Ngrayong sequence shows a single transgressiveregressive cycle. Cross-bedded sandstone and massive sandstone are identified as the most promising potential reservoir facies based on their characteristics in outcrops, their lateral and vertical distributions, their sedimentological characteristics and their petrophysical properties.

DOI： 10.4236/ojg.2017.75042

Language：English   Publishing type：Research paper (international conference proceedings)  

The EOR potential of a biosurfactant was evaluated through core flooding experiments and numerical simulation in this study. The biosurfactant which was called surfactin was generated by a microorganism belonging to Bacillus species. The EOR potential of surfactins has been already reported by previous papers, however, that of surfactins can be different depending on their making process such as the conditions of incubation, extraction, purification, etc. This study used a surfactin which was made by Kaneka corporation's original techniques.
Core flooding experiments were carried out under ambient temperature and pressure to evaluate the EOR potential of the surfactin. Berea sandstone cores whose permeability was 50 md were used in this study. The surfactin solution was injected into cores after water flooding. 3 experiments were carried out by injecting surfactin solution whose surfactin concentration was 0.3 %, 0.03 % and 0.003 % respectively. An experiments were carried out by injecting the culture solution which had been diluted so that the surfactin concentration was 0.3 %. 4 experiments were carried out by injecting sodium dodecyl sulfate (SDS) solution which had been supplemented with a slight amount of surfactin or the culture solution. An injection was continued until oil was not produced completely.
Higher oil recovery was obtained by injecting higher concentration of surfactin. 13.6 % of original oil in place (OOIP) was recovered by injecting 0.3 % of pure surfactin solution, whereas 6.3 % of OOIP was recovered by injecting 0.3 % of pure SDS solution. 0.27 % of SDS solution which was supplemented with surfactin whose concentration was 0.03 % could recover 14.7 % of OOIP. 23.9 % of OOIP could be recovered by injecting the culture solution which was diluted by 16 times so that the surfactin concentration was 0.3 %. Enhancement of oil recovery which was obtained by injecting SDS solution supplemented with the culture solution was a little lower than that with pure surfactin.
The EOR potential of surfactin is quite higher than that of SDS. It was shown that the surfactin can be useful as a cosurfactant for SDS. Culture solution of the microorganism demonstrated much higher EOR potential than pure surfactin, therefore, it may include effective components other than the surfactin. Utilization of the culture solution is economically advantageous.

Language：English   Publishing type：Research paper (international conference proceedings)  

Surfactant injection is one of the most effective EOR techniques. Chemical surfactants however pose a few problems such as their high cost and low-degradability. We study on the utilization of biomass such as agricultural fertilizer mainly comprising the residue of squeezed beer yeast for EOR as an alternative of chemical surfactants because crude oil can be completely miscible with the fertilizer solution. The fertilizer can be stably supplied at a low cost because it is a waste of beer brewing industry and is only used for an animal feed additive so far. Its retail price is approximately 1 USD/kg in Japan.
We semi-quantitatively estimated the interfacial tension (IFT) between the fertilizer solution and crude oil by the oil displacement test. Concentration of the fertilizer was varied between 10 to 50 g/L. The fertilizer solution to which sodium chloride was added at a concentration of 10 to 40 g/L was hydrothermally treated at 60, 80, 100 or 120 ºC for 10, 20, 30, 45 or 60 minutes respectively before the tests. The fertilizer solution to which crude oil was added at a ratio of 1 % was also hydrothermally treated at 120 ºC for 20 minutes. Solution of surfactin which was a commercial biosurfactant was used as a
standard of the IFT.
The IFT was reduced with the decrease in salinity and increase in concentration of the fertilizer and temperature of the hydrothermal treatment. Time of the hydrothermal treatment was preferably 30 minutes or less for the IFT reduction. The capability of 50 g/L of fertilizer solution to reduce the IFT was almost same as the capability of 0.2 g/L of the surfactin solution. Because the fertilizer solution comes into contact with residual oil under high temperature in oil reservoir, IFT between the solution and crude oil can be expected to be reduced in-situ.
Core flooding experiments were carried out by injecting the fertilizer solution after the water flooding as the primary oil recovery. 1.2 % of original oil in place was additionally recovered by injecting 50 g/L of the fertilizer solution after the water flooding. The fertilizer should be biodegradable because it is a microbially-derived substance. In addition, because the IFT reduction was observed after the hydrothermal treatment of the fertilizer solution, the fertilizer should be effective even in the reservoir whose temperature is high such as 120 ºC at which chemical surfactants may be deactivated. From those results, the injection of the fertilizer solution can be a promising EOR which has both high cost performance, low environmental load and high versatility.

Language：English   Publishing type：Research paper (scientific journal)  

In geologic CO2 sequestration, the pH of formation water may be decreased due to CO2 dissolution, which may cause the change of porosity and permeability of reservoir rock. The pH changes of formation water are widely varied depending on CO2 pressure and the content of substances having pH buffering action, therefore, it is important to determine the wide range of pH change of various types of formation water under the various CO2 pressure conditions.
We considered a determination method of pH change of various types of formation water under the various CO2 pressure conditions based on the spectrophotometry using a windowed high-pressure cell and a mixed pH indicator consisting of 4 single pH indicators. The well-defined absorption peaks were found at the wavelength of 614 nm or 444 nm when the pH of the solution was ≥5.6 or <5.6 respectively, therefore, two different calibration curves were derived from the absorbance of standard pH buffer solutions at each wavelength. The validity of this method was confirmed by an experimental result that the pH change of deionized water under 0.1 MPa CO2 pressure had been determined accurately by this method.
We carried out experiments on this method using the real formation water samples which contained bicarbonate ion having pH buffering action with different concentration under various CO2 pressure. The results of the experiments demonstrated that this method is capable of determining the pH change of various types of formation water under various CO2 pressure conditions.

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

We investigated the decrease in oil viscosity caused by the biodegradation of crude oil by a bacterium (AR80) isolated from an oil reservoir, and estimated the potential for this bacterium for use in microbial enhanced oil recovery (MEOR). AR80 degraded long-chain n-alkanes preferentially, and anaerobically increased the ratio between the short-chain and long-chain n-alkane concentrations in the crude oil. The long-chain n-alkane metabolism by AR80 decreased the oil viscosity. AR80 grew well in a reservoir of brine supplemented with yeast extract, and decreased the oil viscosity to approximately 60% of its original value. Adding a small amount of yeast extract (0.05 g/L) was necessary to stimulate the AR80 activity. MEOR can, therefore, be achieved using AR80 without incurring excessive costs. AR80 can grow at temperatures up to 80 °C, and it grows well at between 50 °C and 70 °C. AR80 can grow at a salinity of up to 90 g/L, and it grows well at a salinity of less than 30 g/L. The AR80 activity was not affected very much by high pressures (such as 6.0 MPa). Core flooding experiments were performed by injecting AR80 (in brine supplemented with yeast extract) into Berea sandstone cores. Gas chromatography analysis of the effluent oil suggested that long-chain n-alkanes in the residual oil were preferentially degraded by the AR80 in the porous rocks. The core flooding experiments showed that the AR80 activity in the porous rocks caused the oil recovery to be enhanced, so AR80 could be a suitable candidate for MEOR.

DOI： 10.1007/s13202-013-0095-5

Language：English   Publishing type：Research paper (international conference proceedings)  

DOI： 10.2118/169629-MS

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1007/s00203-014-0972-4

Language：English   Publishing type：Research paper (scientific journal)  

Oil swelling is an important phenomenon in CO2–EOR. According to various studies in the past, the degree of oil swelling depends on the partial pressure of CO2, temperature, and oil composition. However, we expect that other factors, such as oil saturation, capillary pressure, and grain size of reservoir rock must be also considered in evaluating oil swelling because they may influence the interfacial area between oil and CO2, which affects the dissolubility of CO2 in oil. Therefore, we had made clear the effect of the interfacial area on oil swelling in this study.
Oil and CO2 were injected into a small see–through windowed high–pressure cell and oil swelling was observed under a microscope. The swelling factor increased with the increase of the specific interfacial area between oil and CO2. Moreover, oil swelling in porous media was observed by using micro–models which had been made of 2 different diameter glass beads. Swelling factor in fine beads micro–model became larger than that in coarse beads micro–model whose interfacial area between oil and CO2 was smaller than that of fine beads micro–model. Therefore, the swelling factor is expected to be larger with an increase in the interfacial area in porous media. These results suggest that the oil swelling should be expressed as a function of oil saturation, capillary pressure, and grain size of reservoir rock which are related to the interfacial area as well as the partial pressure of CO2, temperature, and oil composition.

DOI： 10.1007/s13202-013-0085-7

Language：English   Publishing type：Research paper (scientific journal)  

The successful enrichment, isolation, and cultivation of prokaryotes are considerably dictated by the selection of appropriate growth media and incubation conditions. In this study, the utilization of natural reservoir brine to enrich and isolate anaerobic thermophilic bacteria from an oil reservoir was observed. The genetic diversity of the bacterial population present in the brine water was subsequently evaluated using polymerase chain reaction (PCR)-denaturing gradient gel electrophoresis (DGGE). In addition, indigenous bacteria that grew in high CO2 concentrations were isolated for examination. We compared the effects of two sterilization methods (filtration and autoclaving) and three gas combinations (pure N2, CO2/N2 (1:9), and pure CO2) injected into the headspace of the medium solution on the cultures. The result demonstrated that the diverse gas composition of the headspace of enrichment culture medium consisting of filtered brine could be one approach to stimulating the growth of physiologically distinct types of microorganisms.

DOI： 10.1080/10916466.2011.615365

Repository Public URL： http://hdl.handle.net/2324/4354918

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Brine produced from water-dissolved natural gas reservoirs should be returned to the reservoirs after the resources are recovered to prevent land subsidence. However, the ability to re-inject the brine gradually decreases and is only rectified by carrying out backwashing treatment of re-injection wells. Because the brine contains high levels of iodine also, it is also recovered from the brine using sulfuric acid and oxidizing agents. These chemicals may stimulate the growth of microorganisms that may cause the clogging. In this study, we used column experiments to investigate the possibility of the microbial clogging.
Significant clogging was observed on the columns that were treated by the brine containing both indigenous microorganisms and dissolved oxygen. In particular, iodide-oxidizing bacteria were detected from the columns and original brine dominantly; therefore, it was assumed to have an important influence on the clogging. Iodine that was produced by iodide-oxidizing bacteria corroded iron in the sand under the presence of dissolved oxygen. Eluted Iron formed ferric hydroxide colloid in the brine and it caused the clogging of the pore spaces.
We also demonstrated that deoxidized brine inhibited the iodide-oxidizing bacteria from becoming dominant and the column from the clogging through the column experiments. From these results, we can suggest removing dissolved oxygen as the most feasible countermeasures for the clogging.

DOI： http://dx.doi.org/10.1016/j.ibiod.2012.10.003

Language：English   Publishing type：Research paper (scientific journal)  

Throughout the world, schemes for putting to use abandoned underground spaces are being pursued. We describe one such pilot scheme involving the utilization of a disused tunnel of an uncompleted railway line that has been revamped as a facility housing temperature-controlled multi-purpose rooms. In all, four rooms were constructed and installed with both indoor and outdoor air conditioning units. Testing of the facility was conducted over a 1-year period to establish operating criteria and to monitor for operating stability. The four rooms were finally maintained at different constant-temperature regimes: cold (5ºC), cool (13ºC), mild (21ºC), and warm (32ºC) with such low power consumption of 0.80 kW because of the nature of the subterranean site. Compared with typical surface facilities, this facility offers an obvious advantage in lower energy consumption. Monitoring of the humidity in the rooms revealed that preventing evaporation from the bare soil surface in the tunnel was the more important factor in controlling humidity in this facility.
The heat transfer analysis of this facility was carried out through the computational analysis using a computational model constructed in this study. Computational analysis showed that the heat insulation property of the tunnel wall was reinforced by prolonged operation and the cost of operating facility became lower with the operation time. In addition, we demonstrated the procedure to estimate the overall heat transmission coefficients of the tunnel wall which was a great help in the design of similar facilities in underground spaces.
The different rooms in the facility are expected to be used for manufacturing fermented foods and drinks depending on temperature and humidity requirements. Not only running costs but also initial costs are expected to be lower than those for surface facilities; for this reason, our system has been demonstrated to be economically viable as well as environment friendly.

DOI： 10.1016/j.tust.2012.06.009

Repository Public URL： http://hdl.handle.net/2324/4354912

Language：English   Publishing type：Research paper (international conference proceedings)  

We investigated the microbial conversion of CO2 into CH4 in depleted oil reservoirs by the interaction between indigenous oil-degrading hydrogen-producing bacteria and indigenous hydrogenotrophic methanogens that have been found in oil reservoirs universally. In this study, we investigated the influence of crude oil, yeast extract, bicarbonate and CO2 on the growth and gas production of those bacteria through the incubation experiments of isolated strains under reservoir conditions. The yeast extract was estimated to be the most influential factor on the growth and gas production of oil-degrading hydrogen-producing bacteria. Methanogen was unaffected by the crude oil, the yeast extract and bicarbonate, however, both CO2 and H2 are assumed to be the influential factors on it because they are the energy sources of methanogen.
In addition, we also investigated their growth kinetics that were needed to construct a numerical simulator of the microbial conversion of CO2 into CH4 in depleted oil reservoirs. The specific growth rate of oil-degrading hydrogen-producing bacteria was increased as the yeast extract concentration increased while that of the methanogen was constant regardless of the yeast extract concentration. These results indicate that the growth of methanogens is unaffected by the yeast extract that is injected into reservoirs to stimulate the growth of ODHPB. The growth yield of HYH-8 and HYH-10 was 5.5x1010 cells/g-(yeast extract) and 3.5x1011 cells/g-(yeast extract) respectively.

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Sequestration of carbon dioxide (CO2) into depleted oil reservoirs may be a method of reducing CO2 emissions. We focus on microbial restoration of natural gas deposits with CO2 sequestration via in situ microbial conversion of CO2 into methane (CH4) by hydrogenotrophic methanogens (HM) that universally inhabit oil reservoirs. The means of supplying HM with H2 for their CH4 production is central to this process. This study considers the potential of this process by evaluating the H2 productivity of hydrocarbon-degrading and hydrogen-producing bacteria (HD–HPB) that inhabit oil reservoirs.
Reservoir brine was extracted from 10 producing wellheads in the Yabase Oilfield of Japan. Indigenous bacteria in the brine samples were incubated with sterile oil under anaerobic conditions with 10%-CO2 (N2 balanced) at 50 °C and 75 °C. Production of H2 and CH4 and consumption of CO2 were observed in almost all the brine at both temperature, especially, larger amount of gases were produced at 50 °C. Those gases production was significantly stimulated with the additional yeast extract, on the other hand, it became lower under high pressure condition.
Nutrient agar inoculated with raw brine was incubated under anaerobic conditions at 50 °C and 75 °C. Microbial single colonies formed in the nutrient agar media after 2 weeks were selected and inoculated into sterile brine including sterile oil. More than 20 isolates were isolated and incubated in the brine media and 14 strains were observed to produce H2 after 3 months incubation. The maximum rate of H2 production by HD–HPB was 0.38 NmL/L-medium/day.
These results suggest that in situ microbial conversion of sequestrated CO2 and H2 generated by HD–HPB into CH4 using HM can be expected in many oilfields universally. Moreover, the most capable HD–HPB isolated in this study can be injected into reservoirs to stimulate the restoration of natural gas deposits with CO2 sequestration.

DOI： 10.1016/j.jngse.2012.01.011

Language：English   Publishing type：Research paper (international conference proceedings)  

The brine that has been produced from water-dissolved natural gas reservoirs should be returned into reservoirs after the resources have been extracted to prevent the subsidence. However, the re-injectivity of the brine declines gradually; therefore, re-injection wells should be maintained by backwashing treatments. Colloidal materials like biofilms can be observed in solid materials that have been produced by the backwashing from the re-injection wells.
Because the brine contains not only dissolved natural gas but also high levels of iodine, the iodine is also extracted from the brine chemically using sulfuric acid and oxidizing agent; therefore, re-injected brine contains sulfate and dissolved oxygen abundantly. These chemicals may stimulate the metabolites of microorganisms that have influences on the clogging; therefore, we considered the influences of these materials on microorganisms that may cause the clogging in this study.
Column experiments were carried out using sand and brine that were collected in the gas field. The columns that the brine including indigenous microorganisms, dissolved oxygen and sulfate was injected into were clogged significantly. Iodide-oxidizing bacteria, iron-oxidizing bacteria and sulfate-reducing bacteria were found specifically in clogged columns, suggesting these microorganisms had influences on the clogging. In particular, Iodide-oxidizing bacteria were also found in original brine; therefore, it was assumed to have an important influence on the clogging.
Iodide-oxidizing bacteria convert iodide into iodine that corrodes iron in the sand under the presence of dissolved oxygen. Iron (II) ion that has been eluted from the sand is oxidized to iron (III) ion by iron-oxidizing bacteria under the presence of dissolved oxygen. Iron (III) ion forms ferric hydroxide colloid in the brine and it causes the clogging of the porous media.
From these mechanisms of the clogging, we can suggest removing dissolved oxygen as the most feasible countermeasures for the clogging.

Language：English   Publishing type：Research paper (international conference proceedings)  

We investigated the in situ microbial conversion of CO2 into CH4 by oil-degrading and H2-producing bacteria and hydrogenotrophic methanogens. CO2 is injected into depleted oil reservoirs as a method of carbon capture and storage (CCS). The bacteria involved in CO2 conversions are affected by high CO2 conditions, which cause a reduction in the pH level of the reservoir brine. Therefore, we assessed the efficacy of this microbial conversion process under high partial CO2 pressure by investigating the microbial communities present in high/low CO2 content reservoirs, the pH reduction of brine under high partial pressure of CO2, and the production of H2 and CH4 by indigenous bacteria in high CO2 content reservoirs. Thermotoga sp. and　Thermoanaerobacter sp., which have previously been shown to produce hydrogen from crude oil by Fujiwara et al.1), were found to be the dominant species in the high CO2 content reservoir. Moreover, Methanobacterium sp. and Methanothermobacter sp., which are well-known hydrogenotrophic methanogens, were also detected in the reservoir. These results indicate that the microorganisms needed for this microbial conversion process can inhabit reservoirs where CO2 has been injected for CCS.
The pH of brine with bicarbonate levels > 0.1 mol/L was found to be maintained at pH 7.0–8.0, which is a favorable pH for the growth of a variety of microorganisms. Neutral pH levels were maintained even under CO2 partial pressure as high as 5.0 MPa, suggesting that the microbial conversion process could easily be applied in reservoirs whose brine is abundant in bicarbonate.
Enrichment culture experiments in brine were carried out under high CO2 partial pressure (3.0 MPa) at 75°C. Production of both H2 and CH4 was detected in brine with pH buffering action, as well as in brine with significantly reduced pH levels due to high CO2 partial pressure. Therefore, the microbial conversion process may also be expected to occur in normal reservoirs with poor acid neutralizing capacity.

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Characteristics of Functional Wall Material Containing a Green Tuff, Yuichi SUGAI, Kyuro SASAKI, Shigeyuki TAKAHATA and Hideo NAKA, Transactions of the Society of Heating, Air-Conditioning and Sanitary Engineers of Japan, No.123, 2007

Language：Japanese   Publishing type：Research paper (scientific journal)  

Possibility of the Towada-Stone Dust for the Deodorizer and the Compost Accelerator, Journal of Japan Institute of Aggregate Technology, No.147, pp.153-161, 2005

Language：Japanese   Publishing type：Research paper (scientific journal)  

The Abilities of Hinai-Green Tuff to Adjust pH and Activate Microorganisms, SUGAI Yuichi, SASAKI Kyuro, MATSUBAYA Osamu, NAKA Hideo and TANAKA Fujio, Journal of the Mining and Materials Processing Institute of Japan, Vol.121, No.10 (20051125) pp. 513-520

Language：Japanese   Publishing type：Research paper (scientific journal)  

Laboratory Investigation on Profile Modification of Oil Reservoir Fluids by Water-insoluble Polymer Producing Microorganism CJF-002, SUGAI Yuichi, KISHITA Atsushi, YUMOTO Tetsuya, ENOMOTO Heiji, HONG Chengxie, FUJIWARA Kazuhiro and ONO Kenji, Journal of the Japanese Association for Petroleum Technology, Vol.70, No.4 (20050701) pp. 315-327

Language：Japanese   Publishing type：Research paper (scientific journal)  

Numerical Experiments of MEOR with the microbe producing water-soluble polymer, SUGAI Yuichi, HONG Chengxie, CHIDA Tadashi and ENOMOTO Heiji, Journal of the Japanese Association for Petroleum Technology, Vol.69, No.5 (20040901) pp. 563-573

Language：English   Publishing type：Research paper (scientific journal)  

Application of Membrane Separation Method to Concentrate Products on the Process Producing Environmentally Adaptable Deicer by means of Wet Oxidation of Organic Wastes, Y.SUGAI, J.FANGMING, H.ENOMOTO and T.MORIYA, RESOURCES PROCESSING, Vol.51、No.3、148－157, 2004

Language：Japanese   Publishing type：Research paper (scientific journal)  

Simulation study on the performance and mechanism of MEOR with a water-soluble polymer producing microbe, SUGAI Yuichi, HONG Chengxie, CHIDA Tadashi and ENOMOTO Heiji, Journal of the Japanese Association for Petroleum Technology, Vol.69, No.4 (20040701) pp. 335-347

Language：Japanese   Publishing type：Research paper (scientific journal)  

Numerical model for MEOR with a microbe producing water-soluble polymer, SUGAI Yuichi, HONG Chengxie, CHIDA Tadashi and ENOMOTO Heiji, Journal of the Japanese Association for Petroleum Technology, Vol.69, No.3 (20040501) pp. 262-271

Language：Japanese   Publishing type：Research paper (scientific journal)  

Laboratory investigation on oil recovery with a Water-Soluble Polymer producing microorganism TU-15A, SUGAI Yuichi, HONG Chengxie, CHIDA Tadashi, ENOMOTO Heiji and YAZAWA Nintoku, Journal of the Japanese Association for Petroleum Technology, Vol.67, No.5 (20020901) pp. 491-500

Language：Japanese   Publishing type：Research paper (scientific journal)  

Screening of water-soluble polymer producing microorganisms for MEOR, SUGAI Yuichi, HONG Chengxie, IKEDA Shuichiro, CHIDA Tadashi, ENOMOTO Heiji and YAZAWA Nintoku, Journal of the Japanese Association for Petroleum Technology, Vol.67, No.3 (20020501) pp. 277-286

Language：English   Publishing type：Research paper (international conference proceedings)  

Laboratory Investigation of Polymer Producer TU-15A for MEOR Field Tests, Y.SUGAI, A.KISHITA, C.X.HONG, H.ENOMOTO, T.CHIDA and S.C.ZHOU, SPE Asia Pacific Oil and Gas Conference and Exhibition, SPE54381, 1999

Publisher：Fuel  

Hydrogen's high energy efficiency and environmental cleanliness position it as a key solution for sustainable energy systems. However, its high diffusivity and flammability pose significant safety risks in confined spaces, where leaks may lead to hazardous accumulations of gas. This study presents a comprehensive framework that integrates advanced data augmentation and multitask learning to address these challenges, bridging gaps in conventional risk assessment methods. By leveraging augmented data, which shows a 92.3 % increase in diversity, along with a multitask model, the framework achieves exceptional predictive performance, with R2 values reaching 0.999 and F1-scores exceeding 0.99. It also demonstrates resilience to noise, significantly surpassing conventional methods while reducing computational demands. Key findings highlight the critical influence of factors such as orifice dimensions, building area, and operating pressure on hydrogen accumulation risks, suggesting actionable strategies for safer hydrogen facility design and management. The proposed data-driven and interpretable framework offers a transformative approach to enhancing safety and reliability in hydrogen energy systems, tackling critical challenges in clean energy deployment.

DOI： 10.1016/j.fuel.2025.135056

Scopus

Publisher：Journal of Energy Storage  

Underground hydrogen (H2) storage in depleted oil and gas reservoirs is a viable option to address supply-demand mismatches in the renewable energy sector. Depleted reservoirs, however, offer challenges when injection of H2 is of concern. One of the most important areas that need to be addressed is the biochemical reactions that can occur when H2 is introduced into the reservoir. Within oil and gas reservoirs, hydrocarbon-degrading organisms are ubiquitous, with some exhibiting the capacity to utilize H2 as a source of energy. By affecting H2 availability, causing corrosion, altering the reservoir's fluid and geological properties, and contributing to biofilm formation, these bacteria can reduce storage efficiency. Hence, prior to the conversion of a depleted reservoir into a H2 storage site, it is imperative to thoroughly characterize the reservoir's microbiome and investigate its impact on H2 recovery. Consequently, it is recommended to undertake an integrated study of bioreactions spanning from laboratory scale investigation to reservoir scale simulations calibrated by experimental data. In the first part of this paper, we discuss six main groups of microorganisms and their sub-categories that can be active during underground H2 storage, highlighting their properties. Each sub-category proposes suitable candidates that can be used for laboratory studies of underground H2 storage. In the second part, we have a review of mathematical models capable of describing microbial growth in porous media and how to couple them with fluid flow in porous media. Finally, we elaborate on how to calculate and extract the experimental coefficients required to calibrate the models to consider the effect of microbial growth on the reservoir scale. This study's workflow could crosslink the microbiological and reservoir-engineering aspects of underground H2 storage.

DOI： 10.1016/j.est.2025.115519

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Scopus

Language：English   Publisher：Environmental Science and Technology  

Nondispersive infrared (NDIR) sensors offer high sensitivity, selectivity, and low operational costs, making them particularly well-suited for environmental gas monitoring, where accurate detection of gases such as CH4 and CO2 is essential. However, these sensors are highly sensitive to environmental conditions, including temperature and humidity, which can significantly affect detection accuracy. This study characterizes the effects of these conditions and applies machine learning models to correct signal biases caused by multiple environmental factors. Experiments simulating natural environmental conditions for CH4 monitoring were conducted in the laboratory across a temperature range of 10-40 °C, relative humidity levels of 10-70%, and CO2 concentrations ranging from 0 to 1000 ppm, revealing significant signal variability under these conditions. The simulations and their results were comprehensively validated at the Ito Natural Analogue Site (INAS), a real-world field-testing location dedicated to investigating environmental impacts. Using machine learning regression algorithms for comprehensive compensation of environmental influences, we successfully mitigated signal biases caused by environmental factors. This offers a cost-effective solution for improving detection accuracy and reliability while reducing system complexity and operational costs.

DOI： 10.1021/acs.est.4c11110

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PubMed

Publisher：Geomechanics and Geophysics for Geo-Energy and Geo-Resources  

Abandoned coal mine goaf is affected by air leakages and prone to spontaneous combustion, resulting in environmental pollution and geological disasters. Haizhou Open-pit Mine adopts both underground and open-pit mining methods. During the long-term mining process, the original stable stratum structure is constantly destroyed, and the slope slides, increasing cracks and severe air leakage around the goaf and roadway. The spontaneous combustion of coal is particularly prominent after the mine shut down. At present, there is no suitable indirect monitoring method to effectively explore the spontaneous combustion area in goaf. The study developed an all-weather monitoring plan and conducted multi-point continuous long-term measurements of the spontaneous combustion state in one abandoned coal mine goaf located in the eastern part of the Haizhou Open-pit Mine. We evaluated the dynamic correlation between surface CO2 flux (SCF) and changes in the underground fire areas, determined the scope and evolution trend of the fire areas, and identified the distribution and change laws of SCF. The results show a significant positive correlation between SCF and soil temperature; moreover, the SCF value was found to reflect the CO2 emission intensity of the goaf. The high SCF in the test area showed month-wise expansion and increase, while the CO2 emission gradually increased monthly, and the calculated annual total emission was approximately 7017 t. Hence, the study can further provide guidance for the monitoring of spontaneous combustion in shallow coal seams, goaf and the assessment of CO2 emissions from underground coal fires through the on-site monitoring and analysis results.

DOI： 10.1007/s40948-024-00867-6

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Scopus

Publisher：Current Applied Physics  

Doping is one of the effective strategies to modulate the optoelectronic properties and photocatalytic activity of photocatalysts. In this study, the effect of Fe doping (0–10 %) on morphology, optical and electronic properties, and photocatalytic activity of ZnO nanostructures is studied. The X-ray diffraction analysis shows that >5 % Fe doping, ZnFe2O4 is segregated as a secondary phase. The crystalline size decreases from 50.8 nm to 21.4 nm and the micro-strain increases with increasing the Fe concentration. The Fe doping-induced electronic restructuring facilitates visible light absorption through the O 2p → Fe 3d transition and the suppression of charge recombination by efficiently trapping conduction band electrons. Density functional theory (DFT) calculations are employed to unravel the underlying electronic changes induced by Fe doping in ZnO. The formation of shallow donor levels below the conduction band originates from the Fe 3d state. Photoluminescence spectra of pristine and Fe-doped ZnO nanostructures show characteristic emission peaks at approximately 384 nm and 570 nm, indicating the recombination of free excitons and oxygen interstitial defects, respectively. The results of the photocatalytic activity tests confirm that the 1 % Fe-doped ZnO nanostructures can exhibit the highest efficiency compared to the heavily doped ZnO nanostructures. The high efficiency in photocatalytic activity of 1 % Fe-doped ZnO nanostructures is ascribed to the modulated electronic structure and defect density. The adsorption affinity of methylene blue and water molecules to the surfaces of pristine and Fe-doped ZnO is simulated using the Monte-Carlo method. This study emphasizes the importance of controlling the dopant concentration to enhance the photocatalytic activity of various photocatalysts.

DOI： 10.1016/j.cap.2024.07.009

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Language：Japanese   Publisher：The Mining and Materials Processing Institute of Japan  

We evaluated the absorption characteristics and phase state of a biphasic CO₂ absorbent using 2-amino-2-methyl-1-propanol (AMP), diethylene glycol diethyl ether (DEGDEE), and water (H₂O). We set the AMP concentration at 30 wt%, and adjusted the H₂O and DEGDEE weight fractions. It was experimentally confirmed that phase separation of the absorbents occurred due to the progress of CO₂ absorption. As the concentration of water decreased, it was separated into a lower phase, which consisted almost entirely of AMP, H₂O and absorbed CO₂, and an upper phase, which consisted of mostly DEGDEE. In the experiment, an absorbent composition of 30 : 20 : 50 wt.% (AMP:DEGDEE : H₂O) was maintained in the liquid state at 313 K and a CO₂ partial pressure of 0.1 atm in the absorption step and at ≥ 343 K and a CO₂ partial pressure of 1.0 atm in the regeneration step. Under CO₂ capture conditions, this adsorbent was separated into two-liquid states in the absorption step, whereas it exhibited a uniform single phase in the regeneration step. Therefore, it could operate under CO₂ capture conditions as a biphasic absorbent. The amount of CO₂ cyclic absorption of this absorbent was twice that of conventional monoethanolamine (MEA) absorbents when the regeneration temperature was set at 363 K.

DOI： 10.2473/journalofmmij.mmij-2023-024

CiNii Research

Publisher：Energy Reports  

Geological storage of carbon dioxide (CO2) is a promising technique to reduce large-scale greenhouse gas emissions. There are some candidates for geological storage formation while deep saline aquifers have attracted tremendous attention because they have the largest potential of all possible subsurface storage sites. CO2 injected into deep saline aquifers migrates upward until it reaches a sealing formation due to its buoyancy effect, which causes poor storage efficiency. Over the past few years, some novel research has been published to utilize nanoparticles for CO2 geological storage. The addition of nanoparticles to injecting super-critical CO2 (scCO2) changes its physical properties, such as the density and viscosity, which could mitigate gravity segregation and viscous fingering. However, the studies related to these techniques are still extremely limited, and the potential advantages or their impacts are poorly understood. In this paper, we investigated the effects of the physical properties of scCO2 containing nanoparticles on storage efficiency by using a versatile commercial simulator (CMG-GEM). In particular, the effects of nanoparticle types (aluminum oxide, silicon dioxide, titanium oxide, and zinc oxide) and concentration on CO2 storage efficiency were presented quantitatively by considering possible operation scenarios. The results showed the migration of CO2 to the upper part of the aquifer was suppressed, and the storage of CO2 in the lower part of the aquifer was promoted when scCO2 was injected with nanoparticles. It also showed some effects in delaying breakthrough time and mitigating breakthrough amount when we assumed the pressure control well. It was indicated that the cumulative breakthrough amount after 30 years was reduced by 8.2% in the minimum case and by 79.3% in the maximum case. Although the proposed method still has economic challenges, the innovation in the production processes of nanoparticles or combining with added value will lead to improving feasibility.

DOI： 10.1016/j.egyr.2024.05.009

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Language：English   Publisher：Scientific Reports  

Biosurfactants, as microbial bioproducts, have significant potential in the field of microbial enhanced oil recovery (MEOR). Biosurfactants are microbial bioproducts with the potential to reduce the interfacial tension (IFT) between crude oil and water, thus enhancing oil recovery. This study aims to investigate the production and characterization of biosurfactants and evaluate their effectiveness in increasing oil recovery. Pseudoxanthomonas taiwanensis was cultured on SMSS medium to produce biosurfactants. Crude oil was found to be the most effective carbon source for biosurfactant production. The biosurfactants exhibited comparable activity to sodium dodecyl sulfate (SDS) at a concentration of 400 ppm in reducing IFT. It was characterized as glycolipids, showing stability in emulsions at high temperatures (up to 120 °C), pH levels ranging from 3 to 9, and NaCl concentrations up to 10% (w/v). Response surface methodology revealed the optimized conditions for the most stable biosurfactants (pH 7, temperature of 40 °C, and salinity of 2%), resulting in an EI24 value of 64.45%. Experimental evaluations included sand pack column and core flooding studies, which demonstrated additional oil recovery of 36.04% and 12.92%, respectively. These results indicate the potential application of P. taiwanensis biosurfactants as sustainable and environmentally friendly approaches to enhance oil recovery in MEOR processes.

DOI： 10.1038/s41598-024-61096-1

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PubMed

Language：English  

DOI： 10.1021/acsomega.3c08317

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PubMed

Language：English   Publisher：ACS Omega  

An optical sensing approach that balances portability with cost efficiency has been designed for the reliable monitoring of fugitive methane (CH4) emissions. Employing a LiTaO3-based pyroelectric detector integrated with micro-electro-mechanical systems and a broad infrared source, the developed gas sensor adeptly measured CH4 concentrations with a low limit of detection of about 5.6 ppmv and showed rapid response times with t90 consistently under 3 s. Notably, the novelty of our method lies in its precise control and reduction of CH4 levels, enhanced by wavelet denoising. This technique, optimized through meticulous grid search, effectively mitigated noise interference noticeable at CH4 levels below 10 ppmv. Postdenoising, nonlinear regression analyses based on the modified Beer-Lambert equation returned R2 values of 0.985 and 0.982 for the training and validation sets, respectively. In conclusion, this gas sensor has been shown to be able to meet the requirements for early warning of CH4 leakage on the surface in various carbon capture, utilization, and storage projects such as enhanced oil or gas recovery projects using CO2 injection.

DOI： 10.1021/acsomega.3c09769

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PubMed

Language：English   Publisher：The Japan Institute of Metals and Materials  

Increasing global temperatures due to high atmospheric carbon dioxide (CO₂) concentrations may cause an imbalance in the carbon circulation on earth. It has been reported that CO₂ emissions from natural soils in all terrestrial areas on Earth account for about 25% of atmospheric CO₂ emissions in the global carbon cycle. A tendency is well known that the higher the soil temperature with the higher the metabolic activity of microorganisms in the soil. Furthermore, since the global soil CO₂ emissions are huge amount that approximately seven times the total atmospheric CO₂ emissions from human origin, it is necessary to investigate the increasing rate of soil CO₂ emission rate per unit area and unit time on a global scale (global soil CO₂ efflux) that is affected by soil temperature rise due to global warming expected in the coming decades.

In this paper, we modeled soil CO₂ efflux vs. diurnal and seasonal variation in soil temperature at a measurement point using a formula that is an exponential function of soil temperature and then evaluated the effect of increasing average soil temperature due to surface air temperature rise by global warming. We have proposed a method to analogically evaluate the potential of increasing the rate of soil CO₂ efflux against a change of 1°C in soil temperature based on the model equation. The power index b (°C⁻¹) just indicates the potential of increasing the rate of soil CO₂ efflux to soil temperature rise in any land area with different soil temperatures on earth. Finally, the values of b were obtained from the published literature with field measurement data at 71 locations in 10 countries including our data measured at the Ito campus, Kyushu University. The average rate of potential increase in soil CO₂ efflux is 0.10°C⁻¹ regardless of vegetation, annual rainfall (precipitation), soil type, and soil components (carbon and nitrogen content). In conclusion, assuming the average soil temperature rises by 1°C and ignoring any effects reducing soil CO₂ reduction due to global warming, the potential increase in annual global soil CO₂ efflux is roughly estimated at 22 billion tons-CO₂/year.

DOI： 10.2320/matertrans.m-m2024801

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CiNii Research

Publisher：Journal of Energy Storage  

To achieve the net-zero target, hydrogen (H2) will emerge as an essential cornerstone within the energy supply chain of the future. To effectively attain such a target for an integrated and sustainable large-volume economy based on H2 on a global scale, proper H2 storage is imperative. This is where the significance of Underground H2 Storage comes to the fore. However, there are many concerns that should be addressed before using underground structures including the interactions between rock, H2, and liquid within the pore spaces. In this study, we simulated the process of an H2 bubble hitting reservoir rock samples and measured the contact angles for rock–H2–distilled water systems using the Navier–Stokes equations for mass and momentum conservation. The phase-field method was utilized for tracking the free surface. Since the phase-field method is essentially a coupling set of equations, we used the commercial finite element software COMSOL, which excels at solving Multiphysics coupling problems, to solve the Navier–Stokes equations and the phase-field method. The predicted contact angles were validated with the experimental results of basalt, shale, and calcite substrates. The simulated and experimental contact angles differed by <2° in most cases exhibiting favorable agreement. Additionally, the simulation was able to replicate the same behavior of the change in contact angle caused by variations in temperature and pressure during the experiments. It is noteworthy that the findings from this study are helpful to better understand and predict the wettability of different minerals during underground H2 storage.

DOI： 10.1016/j.est.2024.110475

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Scopus

Language：English   Publishing type：Research paper (scientific journal)  

The adsorption refrigerator system with HFO-1234yf refrigerant (2,3,3,3-tetrafluoropropene) has a global warming potential of less than 4 and activated carbons (MaxsorbIII, MH-00), mesoporous silica (TMPS-2), and metal organic frameworks (MOF-177). We measured the adsorption isotherm under diverse temperature and pressure conditions experimentally, and evaluated the adsorption characteristics of these adsorbents. In this study, we designed an experimental apparatus using a volumetric method and measured the adsorption equilibrium uptake. The MaxsorbIII/HFO-1234yf pair has an adsorption uptake as high as 1.30 g-HFO-1234yf/g-ads at 40 °C and 300 kPa. The adsorption uptake is approximately equivalent to that of the MaxsorbsIII/HFC-134a pair. The experimental data of the adsorption/desorption isotherms show that there is no hysteresis for the studied pair. The experimental results were reproduced using the Dubinin–Astakhov model (D–A model). The D–A model fits the experimental results precisely within 7%. A diagram of the relationship between HFO-1234yf and MaxsorbsIII also generated the D–A model, and the adsorption uptake capacity between the adsorption and desorption steps was obtained as 0.07 kg-HFO-1234yf/kg-ads at 40 and 80 °C. The adsorption capacities of MOF-177, MaxsorbIII, TMPS-2, and MH-00 were evaluated under similar operating conditions to be 0.19, 0.08, 0.11, and −0.03 kg/kg respectively.

DOI： https://doi.org/10.1080/01430750.2024.2315486

Publisher：International Petroleum Technology Conference, IPTC 2024  

Carbon dioxide (CO2) geological storage has a large potential to achieve a net-zero target of CO2 emissions. CO2 injected into the storage formation typically becomes a super-critical state under the underground temperature and pressure conditions. The injected super-critical CO2 (scCO2) tends to migrate upwards within the reservoir due to its lower density compared to the formation brine even though the density of scCO2 is quite higher than that of gaseous phase CO2. Moreover, injected CO2 is affected by not only the gravity segregation but also the viscous fingering. These phenomena are expected to cause poor storage efficiency in carbon storage projects. In this study, we investigated the potential of adding common metal oxide nanoparticles to scCO2 to improve the storage efficiency utilizing the properties of scCO2 as a solvent under subsurface conditions. This paper presents the pseudo-fluid modeling of scCO2 containing nanoparticles and the results of numerical simulation considering the effects of nanoparticle types and concentrations on the CO2 storage efficiency. In particular, the effect of density alteration on CO2 storage efficiency was investigated in this study. Some pseudo-fluid models of scCO2 containing four types of nanoparticles, such as aluminum oxide, silicon dioxide, titanium oxide, and zinc oxide with different concentration were created, respectively. Furthermore, numerical simulations of scCO2 injection with and without nanoparticles were performed using a two-dimensional radially symmetric model. The results from this work showed the migration of CO2 to the upper part of the formation was suppressed and the storage of CO2 in the lower part of the formation was promoted when scCO2 was injected with nanoparticles. Furthermore, CO2 breakthrough time was delayed several months or years and total breakthrough quantities were also decreased as the density and concentration of nanoparticles in scCO2 became higher in the case of installing an imaginary production well for pressure control. These results suggest that the injection of nanoparticle-dispersed CO2 improves the storage efficiency of CO2 geological storage compared to the injection of CO2 alone. Furthermore, this study showed that the concept has possibility of improving the safety of CO2 geological storage, which may play an important role when considering the long-term CO2 sequestration as well.

DOI： 10.2523/IPTC-23852-MS

Scopus

Publisher：International Petroleum Technology Conference, IPTC 2024  

Supercritical CO2 injected into the aquifer in CCS may migrate upward in the aquifer because its density is lower than the density of formation water. As a result, CO2 cannot be stored widely throughout the aquifer, which may reduce CO2 storage efficiency. The objective of this study is to increase the apparent density of supercritical CO2 by dispersing nanoparticles in itself and to improve CO2 storage efficiency by injecting CO2 widely in the aquifers. The n-hexane, which has a similar solubility parameter to supercritical CO2, was used as an alternative solvent to supercritical CO2 in this study. The nanoparticles such as SiO2, Al2O3, TiO2, and ZnO were added and stirred in n-hexane respectively, and their dispersibility was observed after stirring with a magnetic stirrer or ultrasonication for 30 minutes. The dispersibility of nanoparticles in n-hexane was qualitatively evaluated by irradiating the sample with green laser light after stirring and observing the scattered light. The effect of surfactants on improving the dispersibility of nanoparticles was also evaluated using nanoparticles modified with those surfactants. All the nanoparticles were precipitated after 30 minutes of stopping stirring with a magnetic stirrer. The dispersibility of those nanoparticles was improved by ultrasonication and the dispersion was maintained up to about 3 hours. Similar experiments were conducted using nanoparticles modified with surfactants. As a result, improved dispersibility of Al2O3 and ZnO modified with anionic surfactants was obviously observed and laser light scattering was clearly observed for about 2 hours after the stirring was stopped. Finally, it was demonstrated that the dispersion of Al2O3 nanoparticles modified with anionic surfactant was maintained even after 48 hours in n-hexane by ultrasonication. These results indicate that Al2O3 nanoparticles modified with anionic surfactant have high dispersibility in n-hexane, especially with ultrasonication. Anionic surfactants make the surface of nanoparticles hydrophobic, which enhances their dispersibility in nonpolar solvents such as supercritical CO2. Ultrasonication is effective for eliminating agglomeration among nanoparticles and improves their dispersibility in nonpolar solvents.

DOI： 10.2523/IPTC-23962-EA

Scopus

Publisher：International Journal of Ambient Energy  

The adsorption refrigerator system with HFO-1234yf refrigerant (2,3,3,3-tetrafluoropropene) has a global warming potential of less than 4 and activated carbons (MaxsorbIII, MH-00), mesoporous silica (TMPS-2), and metal organic frameworks (MOF-177). We measured the adsorption isotherm under diverse temperature and pressure conditions experimentally, and evaluated the adsorption characteristics of these adsorbents. In this study, we designed an experimental apparatus using a volumetric method and measured the adsorption equilibrium uptake. The MaxsorbIII/HFO-1234yf pair has an adsorption uptake as high as 1.30 g-HFO-1234yf/g-ads at 40 °C and 300 kPa. The adsorption uptake is approximately equivalent to that of the MaxsorbsIII/HFC-134a pair. The experimental data of the adsorption/desorption isotherms show that there is no hysteresis for the studied pair. The experimental results were reproduced using the Dubinin–Astakhov model (D–A model). The D–A model fits the experimental results precisely within 7%. A diagram of the relationship between HFO-1234yf and MaxsorbsIII also generated the D–A model, and the adsorption uptake capacity between the adsorption and desorption steps was obtained as 0.07 kg-HFO-1234yf/kg-ads at 40 and 80 °C. The adsorption capacities of MOF-177, MaxsorbIII, TMPS-2, and MH-00 were evaluated under similar operating conditions to be 0.19, 0.08, 0.11, and −0.03 kg/kg respectively.

DOI： 10.1080/01430750.2024.2315486

Scopus

Language：English   Publisher：ACS Omega  

Understanding the inhibitory factors affecting the adsorption of CO2 on low-rank coal from shallow-depth coal seams is essential to identify potential coal seams for CO2 sequestration. The CO2 adsorption capacity of shallow-depth coals was measured at a low pressure on raw and dry coals. The samples were also prepared for organic analyses, scanning electron microscopy analyses, and low-temperature nitrogen adsorption analyses to evaluate the CO2 adsorption and identify the inhibitory factors. An investigation was conducted to determine how CO2 adsorption occurs on coal by fitting experimental data to adsorption isotherm models, followed by analyzing the results based on the statistical analysis. In addition, this study used Henry's law, surface potential, and Gibbs free energy to identify the adsorption inhibitor between CO2 and coal. The CO2 adsorption experiment was conducted on raw coal with a moisture content of 15.18-20.11% and dry coal with no moisture. The experimental data showed that the CO2 adsorption capacity in dry coal was 1.6-1.8 times greater than that in raw coal. A fitting graph between the adsorption data and the isotherm model indicated that CO2 adsorption on coal occurred on monolayers and multilayers under raw and dry conditions. Statistical evaluation of the adsorption isotherm models showed that the Langmuir and Freundlich models aligned more closely to the experimental data. According to this result, low-pressure adsorption of CO2 on coal occurred in monolayers and multilayers under raw and dry conditions. Coal containing a high huminite content had a higher potential for CO2 adsorption, and the drying increased the positive relationship. On the other hand, coal containing high inertinite content inhibited CO2 adsorption onto the coal, but the drying process did not adversely affect CO2 adsorption. Furthermore, coal with high moisture and inertinite content inhibited the affinity, accommodation, and spontaneous CO2 adsorption onto the coal. CO2 adsorption could lead to swelling, but moisture loss opened more sites and micropores, resulting in the swelling effect not closing all micropores in dry coal. Based on these results, coal seams with low moisture and inertinite content are the most promising for CO2 adsorption. Altogether, this study provides an understanding of the percentage of inhibitor factors that affects CO2 adsorption on low-rank coal from shallow depths, which may lead to different CO2 adsorption capacities.

DOI： 10.1021/acsomega.3c04615

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Scopus

PubMed

Publisher：Journal of Energy Storage  

To accomplish the net-zero goal, Japan intends to increase its reliance on renewable energies such as solar power (36–38 % in 2030). However, considering the intermittent nature of solar power, the resulting energy must be transformed to a secondary energy carrier such as H2. Japan, on the other hand, is expected to import 20 × 106 tons of H2 each year by 2050. Because of these large volumes, new H2 storage techniques must be developed, in particular underground hydrogen storage (UHS). This paper ranks eight gas reservoirs out of 106 oil and gas fields in four Japanese prefectures regarding their suitability for UHS, and then suggests a H2 injection and withdrawal scheme based on the history of electricity consumption and solar power curtailment. Then, a reservoir simulation study was performed to investigate the effects of factors such as hysteresis, repeated cycles and cushion gas on the performance of these fields. The outcomes for water-drive and volumetric gas reservoirs were compared to better understand the effects of an aquifer on the long-term performance of a gas reservoir when used for UHS. Finally, it was demonstrated that the technology sought for the conversion of H2 back to electricity after withdrawal from a UHS site governs the overall efficiency of a power-H2-power process.

DOI： 10.1016/j.est.2023.107679

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Scopus

Publisher：Energy Science and Engineering  

In deep coal mining, the high temperature and humidity environment are one of the main disasters threatening workers and equipment. To predict the temperature and humidity of airflow in the airway accurately, this study establishes a numerical calculation model of the surrounding rock temperature, airflow temperature, and humidity under the conditions of considering the moisture evaporation and heat absorption of the airway wall, the condensation and heat release of supersaturated water vapor in the airflow, and the influence of air compression or expansion. Combined with the two-dimensional (2D) heat conduction model (considering the influence of the axial surrounding rock heat conduction of the airway), the axial strip partial moisture calculation model of the airway is proposed, and then the uniform moist wall model and the axial strip partial moist wall model are established. The influence of different parameters on the temperature and humidity of airflow is discussed by analyzing the results of numerical simulation of the uniform wet surface model (UWSM) and partly wet surface model (PWSM) of the airway wall. The results show that the surrounding rock temperature, especially the temperature distribution of the airway wall, calculated by using the 2D heat conduction model under the local humid airway conditions, is more realistic. The increment of airflow temperature decreases with the increase of wet area ratio, airflow temperature at the entrance and airway radius, and increases with relative humidity at the entrance. The calculation accuracy of temperature and humidity prediction for large ventilation networks can be further improved by using the equivalent humidity of the UWSM to replace the correction coefficient of the wet area ratio of the PWSM.

DOI： 10.1002/ese3.1431

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Scopus

Publisher：Journal of Dispersion Science and Technology  

Fluids incorporating carbon dioxide (CO2) microbubbles have been utilized to promote enhanced oil recovery from hydrocarbon reservoirs. The performance of such fluids in porous media is greatly affected by both the bubble size and stability. On this basis, the present study evaluated the effects of varying the concentrations of a xanthan gum (XG) polymer, a surfactant (sodium dodecyl sulfate: SDS) and sodium chloride (NaCl) on both the stability and bubble size distribution (BSD) of CO2 microbubbles. CO2 microbubble dispersions were prepared using a high-speed homogenizer in conjunction with the diffusion of gaseous CO2 through aqueous solutions. The stability of each dispersion was ascertained using a drainage test, while the BSD was determined by optical microscopy and fitted to either normal, log-normal or Weibull functions. The results showed that a Weibull distribution gave the most accurate fit for all experimental data. Increases in either the SDS or XG polymer concentration were found to decrease the microbubble size. However, these same changes increased the microbubble stability as a consequence of structural enhancement. The addition of NaCl up to a concentration of 10 g/L (10 g/1000g) decreased the average bubble size by approximately 2.7%. Stability was also reduced as the NaCl concentration was increased because of the gravitational effect and coalescence.

DOI： 10.1080/01932691.2021.1974873

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Scopus

Publisher：International Journal of Hydrogen Energy  

Underground hydrogen storage (UHS) in depleted hydrocarbon reservoirs is a prospective choice to store enormous volumes of hydrogen (H2). However, these subsurface formations must be able not only to store H2 in an effective and secure manner, but also to produce the required volumes of H2 upon demand. This paper first reviews the critical parameters to be considered for geological analysis and reservoir engineering evaluation of UHS. The formation depth, the interactions of rock-brine-H2, the caprock (seal) and well integrity are the most prominent parameters as far as UHS is concerned. In respect of these critical parameters, tentative H2 storage is screened from the existing gas storage fields in the Niigata prefecture of Japan, and it was revealed that the Sekihara gas field is a suitable candidate for UHS with a storage capacity of 2.06 × 108 m3 and a depth of 1000 m. Then, a series of numerical simulations utilizing CMG software was conducted to find out the extent to which critical parameters alter H2 storage capacity. The results demonstrated that this field, with a recovery factor of 82.7% in the sixth cycle of production is a prospective site for H2 storage.

DOI： 10.1016/j.ijhydene.2022.12.108

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Scopus

Publisher：Journal of Petroleum Exploration and Production Technology  

In this study, the CO2 adsorption capacity was measured on Indonesian low-rank coals in the raw and dry conditions in powder and block states using different coal sample preparation to estimate CO2 sequestration and storage potential. Coal sample specimens were taken from three different areas in the South Sumatra Basin, Indonesia. The adsorption experiments were performed using the volumetric method at a temperature of 318.15 K and pressure up to 3 MPa. The CO2 excess adsorption capacity of powder coal is always higher than block coal. Moreover, decreasing moisture content by the drying process increases CO2 adsorption capacity on coal. Based on fitted CO2 adsorption experimental data with the Langmuir and Freundlich isotherm model, the adsorption occurs on monolayer and multilayer at various conditions. Langmuir volume capacity and pressure show drying and crushing process increased adsorption capacity. However, the drying process affects more the capability of coal to adsorb CO2 than the powdered sample, especially in low-rank coal. It was also observed adsorption capacity is directly proportional to huminite content in the coal. Due to lower moisture and higher huminite contents, the dried WB coal powder had the highest CO2 adsorption capacity over the other coal samples in similar sample conditions. Altogether, this study may provide a better understanding in CO2 adsorption on low-rank coal with different coal sample preparation resulting in different CO2 adsorption capacity.

DOI： 10.1007/s13202-022-01569-z

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Scopus

Publisher：Fuel  

Evaporation and condensation of moisture affect dramatically the spontaneous combustion of lignite with high moisture content at low temperatures. Moisture migration between the lignite and the external environment of coal stockpile encompasses the scales of individual particles and stockpile. The cyclic moisture evaporation/condensation test was applied to investigate moisture migration of individual lignite particles at different particle sizes and temperatures. The wire-mesh basket test was selected primarily to analyze the heating process and critical self-ignition temperature of lignite stockpile. Results of the cyclic moisture evaporation/condensation test reveal that the moisture content of re-saturated lignite is much lower than that of the original one. Moisture content versus time showed a tendency to overlap in repeated moisture evaporation processes, and so did the repeated moisture evaporation processes. Therefore, a model of moisture migration of individual particles was built to describe the repeated moisture evaporation and condensation processes. The time factor determines the speed of moisture evaporation and condensation of individual lignite particles, being inversely proportional to ambient temperature and proportional to particle size, respectively. In the wire-mesh basket test, the heating process of the lignite stockpile can be divided into four stages, but the influence of moisture was more pronounced in stage II. Critical self-ignition temperature is proportional to particle size and increases linearly with moisture content. According to Frank-Kamenetskii theory, an increase in either particle size or moisture content can restrain the tendency of spontaneous combustion of Baiyinhua lignite stockpile.

DOI： 10.1016/j.fuel.2022.126774

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Scopus

Publisher：SPE Western Regional Meeting Proceedings  

Wellbore instability is a major preoccupation during drilling operations and is highly dependent of the physiochemical features of the drilling mud. The hydrophilic clays are used in making drilling mud as they provide extensive viscosity and gel strength, and other rheological properties important for optimum drilling mud performance. However, the segregation of the suspended particles of the once optimum mud to create mud cake against the wellbore formation leads to phases imbalance in the mud system, degrading the physiochemical characteristics of the now worn-out mud after several cycling in and out of the well. Although it is crucial to consider the influence of bottomhole conditions in mud rheological alteration, it is necessary to highlight the direct correlation of most mud physiochemical features with the swelling index of the mud. Therefore, optimization of drilling mud is still up to date mostly about swelling control of the mud thus solid-liquid balancing. Overtime, research papers addressing drilling mud enhancement transitioned from mechanical means such as Loss Circulation Materials (LCM) to chemical additives including polymers which as economically profitable and have swelling abilities. Polyvinyl alcohol one most desirable polymers for future drilling fluid designing as it has proved to influence mud rheology and cake filtration positively. Therefore, this study is an attempt to assess the impact of polyvinyl alcohol on wellbore isolation of a water-based drilling mud. The experiment included two types of Polyvinyl Alcohol (PVOH): Non-ionic PVOH and Cationic PVOH. Each PVOH was added to a set of 3 samples at concentrations 0.1, 0.3, and 0.5 wt.%. An additional sample with no polymer was used as a reference sample. The samples were each subjected to 5h of static pressurized filtration at atmospheric temperature. After which Spectral analysis where performed, and Permeability estimated using Darcy's Law. The results show significant influence on Polyvinyl Alcohol on mud phases distribution. Major dehydration of samples was observed as the sample without PVOH recorded the highest filtrate production while the samples with Cationic, Non-Ionic, and Conventional PVOH had average reduction of 21%,38%, and 43% respectively. The mud cake permeability of samples drastically drops at the least concentration of PVOH with a noticeable difference in permeability despite having the same PVOH concentrations. Those differences are attributed to PVOH-specific structural compositions. This study provides evidence of Polyvinyl Alcohol being responsible for improving mud thermal stability while helping any industry applying drilling activities to expand the range of polymer types that can be used to attain the desired drilling mud for a particular formation.

DOI： 10.2118/213014-MS

Scopus

Publisher：Society of Petroleum Engineers - Asia Pacific Unconventional Resources Symposium, APUR 2023  

The current thermal recovery processes of bitumen consume tremendous amounts of water and energy and even emit greenhouse gases (GHGs). As a solution, this study proposes a cold bitumen recovery that adapts the CO2 huff-n-puff process combined with horizontal wells and gravity drainage on the premise that CO2 gas is more soluble in bitumen at lower temperatures. This process generates CO2 -based foamy bitumen, introduces swelling phenomenon in the huff stage due to CO2 dissolution in the bitumen phase, and provides foam expansion in the puff stage because of CO2 liberation. Due to pressure differences, gravity, and foam expansion, foamy bitumen is drained into the production well. Therefore, the current study aims to evaluate the potential of this method after the impacts of important parameters on the foam expansion such as temperature, pressure, viscosity, and solubility are investigated. The studied conditions are 2, 3, and 4 MPa of CO2 injection pressure under temperatures of 25, 35, 45, and 55 °C. The results from the adapted CO2 huff-n-puff experiment show that the solubility of CO2 in bitumen increases at higher injecting pressures and lower temperatures. The highest expansion factors which are about 9 were obtained at the highest injecting pressure at 25 and 35 °C followed by the expansion from 3 MPa injecting pressure at 45 and 55 °C. The third place is shared by the injecting pressure of 3 MPa at 25 and 35 °C and injecting pressure of 4 MPa at 45 and 55 °C. The lowest expansion factor was obtained at the lowest injecting pressure at the highest temperature. These peculiar results indicate that temperature, pressure, viscosity, and solubility possess unique roles and strongly influence each other in a certain manner that can either benefit or hinder the foam expansion. It also depicts that with a harmonious and optimal combination of all these parameters, a high expansion of CO2 -based foamy bitumen is achievable. Besides, the current highest expansion factor of this study proves that this cold production is theoretically capable of driving bitumen out of the pore spaces even without the assistance of gravity drainage or any form of heating.

DOI： 10.2118/217325-MS

Scopus

Publisher：Society of Petroleum Engineers - ADIPEC, ADIP 2023  

A method for reducing power peak is to store hydrogen (H2) underground in depleted gas reservoirs (hereafter UHS). In contrast to alternative solutions, like salt caverns or aquifers, the availability of depleted gas reservoirs gives a greater storage capacity. But choosing the right gas field for the UHS and carrying it out are tricky. As a result, the goal of this work is to characterize the UHS in the chosen field and rank Japanese gas fields for it. To begin with, we ranked and screened potential H2 storage locations in Japan using the Analytical Hierarchy Process (AHP). The best locations for UHS, according to our calculations using the AHP approach, are Sekihara, Kumoide, Katakai, Nakajo, Kubiki, Shiunji, Iwafune-oki (gas), and Minami-Nagaoka. These fields' high flow capacity, depth, current reservoir pressure, and dip angle are the causes of their elevated position. Then, based on a volumetric reservoir, we studied the H2 injection, storage, and withdrawal capacity at the chosen site in the Niigata Prefecture using the CMG reservoir simulator. For the first time in Japan, this work offers a framework for evaluating and ranking potential depleted gas reservoirs as a UHS option. It also includes a reservoir simulation study to comprehend the impact of various parameters such as hysteresis trapping, number of injection and withdrawal cycles, and type of cushion gas on the efficiency of H2 storage and withdrawal in a volumetric gas reservoir.

DOI： 10.2118/216987-MS

Scopus

Publisher：Petroleum Science and Technology  

The dissolution of fine particles into flowing and stranded fluids is not only one of the most prominent formation damage problems but also, is prejudicial to economic viability of oil-bearing matrices. To this end, the present paper investigates the effect of fine particles dissolution on rheological properties of heavy crude oil (API 16.6°). Because of the siliceous nature of the candidate formation, fine particles were modeled by nanoparticles. Considerations were given to silica oxide (Si-NP), alumina oxide (Al-NP) and iron oxide (Fe- NP). NPs were mixed into the dead heavy oil. Both thermogravimetric and rheological studies were used to evaluate the effect of fine migration on crude oil properties. The former revealed that the dissolution of Si-NP has the most prominent effect on physical properties compared to Al-NP and Fe-NP. The dissolution of Si-NP increased the oil viscosity up to 26 cP which was 22% larger than the oil without Si-NP. Increasing the load in Si-NP enhanced the stripping of the heaviest fractions of the crude oil (asphaltenes) from the bulk. The study attributed these results to the decrease in activation energy. The findings of this study can help for better understanding of crude oil upgrading using NP dissolution.

DOI： 10.1080/10916466.2022.2049817

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Scopus

Publisher：Journal of Environmental Chemical Engineering  

In this study, the crystal structures of the 2-amino-1-methyl-1H-benzimidazol-3-ium(O,O-di-isopropylphosphorodithioate) ionic liquid - [C8H10N3]+ [C6H14O2P1S2]- [(MAB+H)DIPDTP] and bis(1-methyl-1 H-benzimidazol-2-amine)-bis(O,O-di-isopropyl phosphorodithioato)-cadmium(II) - C28H46Cd1N6O4P2S4 [Cd(MAB)2(DIPDTP)2]) are characterized by X-ray diffraction analysis. Organic ligands - O,O-di-isopropylphosphorodithioate (DIPDTP), 1-methyl-1 H-benzimidazol-2-amine (MAB), and new acid-base bi-functional protonic ionic liquid ([(MAB+H)DIPDTP]) - are immobilized into commercial polymeric crosslinked polystyrene-divinylbenzene sorbent (PAD600) and their sorption capacity for Cd2+ from aqueous solution is evaluated. The successful immobilization of DIPDTP and MAB into macroporous polystyrene is confirmed by means of scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), Fourier-transform infrared spectroscopy (FTIR), and N2-BET analysis. The Cd2+ sorption efficiency of PAD600-MAB-DIPDTP sorbent increases due to the combination of physical adsorption and extraction, surface complexation, and formation of metal complexes, chelates, and poorly soluble compounds. The adsorption equilibrium data are better fitted to the Freundlich isotherm models. The overall sorption is exothermic and spontaneous and follows a pseudo-second-order kinetic model. This indicates a complex sorption mechanism, including both physical adsorption and strong chemical interaction, dissociation constant, acid-base properties, and reaction condition (pH, temperature, concentration, etc.). The novel composite material can be a promising adsorbent for Cd2+ removal from contaminated water.

DOI： 10.1016/j.jece.2022.108900

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Scopus

Web of Science

Web of Science

Publisher：Combustion Science and Technology  

This study presents a novel cross-linked gel to prevent coal spontaneous combustion. Complex Water-Solution (C-WS) of sodium metasilicate nonahydrate (SMN) and polyvinyl alcohol (PVA) was used to wet coal particles and reacted with CO2 from coal oxidation and natural atmospheric air to form the cross-linked gel (SMN/PVA gel), which was examined by measuring critical self-ignition temperature (CSIT) through the wire-mesh basket test. Baiyinhua lignite coal excavated from Inner Mongolia was used to investigate the inhibitory effect of SMN/PVA gel. Wire-mesh basket test results indicated the fire-prevention effectiveness of the SMN/PVA gel from C-WS was superior to those of pre-formed SMN/PVA gels. It snugly covered the coal particle surface and inlets of micropores to prevent oxygen ingress and water emission, and thus exhibited excellent performance in stability and compatibility. Based on the present tests, the concentrations of SMN-16 wt% and PVA-0.5 wt% in C-WS were best and increased the CSIT of raw coal by 26°C. The effect of wetting C-WS on CSIT for different including coal pile volume and particle size has been presented as an empirical equation to estimate the CSITs for SMN and PVA concentrations to consider field applications.

DOI： 10.1080/00102202.2020.1867544

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Scopus

Publisher：Energies  

This study proposed a novel foam EOR technique using Pseudomonas aeruginosa to generate the foam and investigated the potential of the microbial foam EOR to modify the permeability of a high-permeability porous system. We investigated oxygen nanobubble, carbon dioxide nanobubble and ferrous sulfate concentrations to discover the optimal levels for activating the foam generation of the microorganism through cultivation experiments. We also clarified the behavior of the microbial foam generation and the bioproducts that contribute to the foam generation. The potential of the foam to decrease the permeability of high-permeability porous systems was evaluated through flooding experiments using sand pack cores. The foam generation became more active with the increase in the number of nanobubbles, while there was an optimal concentration of ferrous sulfate for foam generation. The foam was identified as being induced by the proteins produced by the microorganism, which can be expected to bring about several advantages over surfactant-induced foam. The foam successfully decreased the permeability of high-permeability sand pack cores to half of their initial levels. These results demonstrate that the microbial foam EOR has the potential to decrease the permeability of high-permeability porous systems and improve the permeability heterogeneity in oil reservoirs.

DOI： 10.3390/en15072344

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Scopus

Language：English   Publisher：Elsevier  

To further improve carbon dioxide enhanced oil recovery CO_2-EOR efficiency in heterogeneous reservoirs, the use of CO_2 microbubbles as a temporary blocking agent is attracting widespread interest due to their significant stability. This study aims to investigate the plugging performance of CO_2 microbubbles in both homogeneous and heterogeneous porous media through a series of sandpack experiments. First of all, CO_2 microbubble fluids were generated by stirring CO_2 gas diffused into polymer (Xanthan gum (XG)) and surfactant (Sodium dodecyl sulfate (SDS)) solution with different gas: liquid ratios. Then, CO_2 microbubbles fluids were injected into single-core and dual-core sandpack systems. The results show that the rheological behaviors of CO_2 microbubble fluids in this study were followed the Power-law model at room temperature. The apparent viscosity of CO_2 microbubble fluid increased as the gas: liquid ratio increased. CO_2 microbubbles could block pore throat due to the “Jamin effect” and increase the resistance in porous media. The blocking ability of CO_2 microbubbles reached an optimal value at the gas:liquid ratio of 20 % in the homogeneous porous media. Moreover, the selective pugging ability of CO_2 microbubbles in dual-core sandpack tests was significant. CO_2 microbubbles exhibited a good flow control profile in the high permeability region and flexibility to flow over the pore constrictions in the low permeability region, leading to an ultimate fractional flow proportion (50%:50%) in the dual-core sandpack model with a permeability differential of 1.0:2.0 darcy. The fractional flow ratio was considerable compared with a polymer injection. At the higher heterogeneity of porous media (0.5:2.0 darcy), CO_2 microbubble fluid could still establish a good swept performance. This makes CO_2 microbubble fluid injection a promising candidate for heterogeneous reservoirs where conventional CO_2 flooding processes have limited ability. This finding would be helpful in developing the utilization of CO_2 microbubbles in EOR operation by better understanding their plugging mechanism in porous media.

CiNii Research

Publisher：Journal of Petroleum Science and Engineering  

To further improve carbon dioxide enhanced oil recovery CO2-EOR efficiency in heterogeneous reservoirs, the use of CO2 microbubbles as a temporary blocking agent is attracting widespread interest due to their significant stability. This study aims to investigate the plugging performance of CO2 microbubbles in both homogeneous and heterogeneous porous media through a series of sandpack experiments. First of all, CO2 microbubble fluids were generated by stirring CO2 gas diffused into polymer (Xanthan gum (XG)) and surfactant (Sodium dodecyl sulfate (SDS)) solution with different gas: liquid ratios. Then, CO2 microbubbles fluids were injected into single-core and dual-core sandpack systems. The results show that the rheological behaviors of CO2 microbubble fluids in this study were followed the Power-law model at room temperature. The apparent viscosity of CO2 microbubble fluid increased as the gas: liquid ratio increased. CO2 microbubbles could block pore throat due to the “Jamin effect” and increase the resistance in porous media. The blocking ability of CO2 microbubbles reached an optimal value at the gas:liquid ratio of 20% in the homogeneous porous media. Moreover, the selective pugging ability of CO2 microbubbles in dual-core sandpack tests was significant. CO2 microbubbles exhibited a good flow control profile in the high permeability region and flexibility to flow over the pore constrictions in the low permeability region, leading to an ultimate fractional flow proportion (50%:50%) in the dual-core sandpack model with a permeability differential of 1.0:2.0 darcy. The fractional flow ratio was considerable compared with a polymer injection. At the higher heterogeneity of porous media (0.5:2.0 darcy), CO2 microbubble fluid could still establish a good swept performance. This makes CO2 microbubble fluid injection a promising candidate for heterogeneous reservoirs where conventional CO2 flooding processes have limited ability. This finding would be helpful in developing the utilization of CO2 microbubbles in EOR operation by better understanding their plugging mechanism in porous media.

DOI： 10.1016/j.petrol.2022.110187

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Scopus

Language：English   Publisher：MDPI (Multidisciplinary Digital Publishing Institute)  

This study proposed a novel foam EOR technique using Pseudomonas aeruginosa to generate the foam and investigated the potential of the microbial foam EOR to modify the permeability of a high-permeability porous system. We investigated oxygen nanobubble, carbon dioxide nanobubble and ferrous sulfate concentrations to discover the optimal levels for activating the foam generation of the microorganism through cultivation experiments. We also clarified the behavior of the microbial foam generation and the bioproducts that contribute to the foam generation. The potential of the foam to decrease the permeability of high-permeability porous systems was evaluated through flooding experiments using sand pack cores. The foam generation became more active with the increase in the number of nanobubbles, while there was an optimal concentration of ferrous sulfate for foam generation. The foam was identified as being induced by the proteins produced by the microorganism, which can be expected to bring about several advantages over surfactant-induced foam. The foam successfully decreased the permeability of high-permeability sand pack cores to half of their initial levels. These results demonstrate that the microbial foam EOR has the potential to decrease the permeability of high-permeability porous systems and improve the permeability heterogeneity in oil reservoirs.

CiNii Research

Publisher：Gases  

Enhanced coal bed methane recovery using gas injection can provide increased methane extraction depending on the characteristics of the coal and the gas that is used. Accurate prediction of the extent of gas adsorption by coal are therefore important. Both experimental methods and modeling have been used to assess gas adsorption and its effects, including volumetric and gravimetric techniques, as well as the Ono–Kondo model and other numerical simulations. Thermodynamic parameters may be used to model adsorption on coal surfaces while adsorption isotherms can be used to predict adsorption on coal pores. In addition, density functional theory and grand canonical Monte Carlo methods may be employed. Complementary analytical techniques include Fourier transform infrared, Raman spectroscopy, XR diffraction, and 13C nuclear magnetic resonance spectroscopy. This review summarizes the cutting-edge research concerning the adsorption of CO2, N2, or mixture gas onto coal surfaces and into coal pores based on both experimental studies and simulations.

DOI： 10.3390/gases2010001

Scopus

Language：English   Publishing type：Research paper (scientific journal)  

In this study, we evaluated the SrBr2 hydration reaction rate on repeated cycling. It was estimated that hydrated SrBr2 particles were expanded by hydration and condensed to form secondary particles; thus, the hydration reaction was reduced by repeated cycles. Using volumetric methods, we examined the effect of repetition on the reaction rate for 900 cycles during hydration and dehydration and analyzed the reaction rate using the unreacted core-shell model. From the experimental and calculated results, we confirmed that reaction rate decreased and the sample particles formed secondary particles after 900 repeated cycles. By analyzing the unreacted core-shell model, we found that the coefficient of H2O diffusion in the particles exponentially decreased with increasing repeated cycles. The value of the diffusion coefficient after 900 cycles was five times lower than that of the first cycle. To achieve stable repeated hydration cycles, technology to control the formation of secondary particles must be investigated.

DOI： https://doi.org/10.4236/msce.2022.102005

Language：English   Publisher：MDPI (Multidisciplinary Digital Publishing Institute)  

Enhanced coal bed methane recovery using gas injection can provide increased methane extraction depending on the characteristics of the coal and the gas that is used. Accurate prediction of the extent of gas adsorption by coal are therefore important. Both experimental methods and modeling have been used to assess gas adsorption and its effects, including volumetric and gravimetric techniques, as well as the Ono–Kondo model and other numerical simulations. Thermodynamic parameters may be used to model adsorption on coal surfaces while adsorption isotherms can be used to predict adsorption on coal pores. In addition, density functional theory and grand canonical Monte Carlo methods may be employed. Complementary analytical techniques include Fourier transform infrared, Raman spectroscopy, XR diffraction, and C^^<13> nuclear magnetic resonance spectroscopy. This review summarizes the cutting-edge research concerning the adsorption of CO_2, N_2, or mixture gas onto coal surfaces and into coal pores based on both experimental studies and simulations.

CiNii Research

Publisher：Society of Petroleum Engineers - SPE Asia Pacific Oil and Gas Conference and Exhibition 2022, APOG 2022  

Swelling control is an elaborated balancing of solid-liquid ratios in the mud, influencing crucial physiochemical features. Mechanical swelling control methods showing limitations drove recent researchers to consider chemical agents, including polyvinyl alcohol (PVOH). PVOH is known to have a swelling ability to improve mud rheology. The present study investigates the synergy of PVOH and Bentonite in an aqueous environment by analyzing the effluents samples. Three types of PVOH were selected: a standard PVOH and two modified PVOHs (a non-ionic group PVOH and a cationic group PVOH-3 attached to the carbon backbone. Except for the control sample (sample without polymer), PVOHs were added to different mud samples at ranging concentrations of 0.1 wt.% to 0.5 wt.%; each has a bulk volume of 400 ml. Each mud sample was filtrated at room temperature under an applied pressure of 1.28 MPa for 5 hours. The samples' effluents were then analyzed for polymer adsorption. Preliminary filtration tests revealed further effluent production reduction with increased PVOH concentration. Compared to the control sample, samples containing standards PVOH-1, Non-ionic PVOH-2, and Cationic PVOH-3, respectively, had their mud cake mass increase of 48%, 36%, and 38%, while respectively having filtrate recovery reduction of 21%, 19%, and 43%. Adsorption tests showed mud swelling owes primarily to hydrogen bonding which is counteracted by the presence of a charged group. Mud swelling is, therefore, dependent on the rate of hydrogen bounding in a system.

DOI： 10.2118/210694-MS

Scopus

Publisher：Society of Petroleum Engineers - SPE Conference at Oman Petroleum and Energy Show, OPES 2022  

The effect of kaolinite fine particles migration and wettability alteration during low salinity water-flooding (LSW-flooding) has been investigated for Omani sandstone reservoirs. Water flooding by re-injecting the reservoir brine is currently operated in the subjected Omani oil fields, and LSW is one of the operations to improve the oil production. However, relatively large amount of precipitated oil sludge was observed in the production and surface facilities along with the produced crude oil. In present experimental study, Omani intermediate oil (API gravity of 30°) and oil sludge were sampled from a skimming tank in the production facility. The physical and chemical characteristics of the clay particles were analyzed by a laser particle size distribution analyzer, SEM, XRD, and SQX after separated from oil. Furthermore, water-flooding tests by brine and LSW were carried out using Berea sandstone cores saturated by three different conditions of the Omani oil and kaolinite fine particles to simulate clay particles in the reservoir conditions. The kaolinite-particles slurry of 0.4μm in average size were used for the tests. The first core was saturated with oil only, the second one was filled up with kaolinite fine particles slurry then saturated with the oil, and the third one was saturated with the mixture of kaolinite-particles slurry and the oil. The results of LSW flooding after brine flooding showed that 30 % increase of oil recovery was obtained in the cases including kaolinite fine particles compared to that of oil only. In addition, the wettability of the cores contained kaolinite fine particles showed stronger water-wettability than the core without kaolinite. Zeta potential was measured to investigate the surface charge of kaolinite-particles in brine and water. The kaolinite fine particles were negatively charged as -15 mV in the brine, while it was -50 mV in the LSW used for the LSW flooding test. This difference has explained that the increase of oil recovery ratio in the water-flooding test was induced by kaolinite fine particles in the cores. The ions were traced in the effluents in LSW flooding, and it was found that the concentration of Ca2+ and Mg2+ reduced sharply from their initial concentration of 722 and 788 ppm to 34 and 26 ppm respectively with pH increasing from 6.8 to below 9.0.Those results indicate clearly that the kaolinite fine particles have a function to reduce the Sor and shift the wettability to water-wet that attributed to the interactions between oil, water and kaolinite-particles in the process of LSW flooding.

DOI： 10.2118/200253-MS

Scopus

Publisher：Society of Petroleum Engineers - SPE Asia Pacific Oil and Gas Conference and Exhibition 2022, APOG 2022  

The foam improves heterogeneity of permeability in oil reservoir and contributes to enhancing oil recovery. Both surfactant and gas are alternatingly injected into oil reservoir in foam EOR, therefore, it has several challenges: high cost of surfactant, formation of precipitation with bivalent cations, adsorption of surfactant on reservoir rock, etc. This study proposes the microbial foam EOR which overcomes those challenges by having microorganism generate foam in-situ. We have found an ability of a microorganism belonging to Pseudomonas aeruginosa to generate foam under anaerobic conditions. This study investigated the source materials constructing the foam and capacity of the foam to improve the heterogeneity of the permeability. The challenges of our study are the reproducibility of the foam generation and the foam stability. This study therefore examined the source materials of the foam to understand the mechanisms of the foam generation. We focused on protein, which has been suggested as a possible component of the foam in our previous studies, and examined the relationship between the amount of foam generated by P. aeruginosa and the concentration of protein in its culture solution. As a result, a positive correlation was found between them. This result indicates that the foam generated by P. aeruginosa is composed of the protein produced by the microorganism. Next, the performance of the foam decreasing permeability of high permeability porous media was evaluated through sand pack flooding experiment. P. aeruginosa was injected into a sand pack and cultivated in-situ. The post-flush water was injected into the sand pack after three days' in-situ cultivation to measure the permeability. As a result, the permeability of the sand pack was successfully decreased to half after the cultivation. The permeability of a sand pack in which P. aeruginosa was injected with culture medium and in-situ cultivated was successfully decreased to half of initial. The efflux of bacterial cells of P. aeruginosa was detected after injecting 1.3 pore volumes of postflush water, which shows that the postflush water flowed through areas other than the area where P. aeruginosa grew and produced the foam. These results indicate that the foam produced in-situ by P. aeruginosa is effective for improving the heterogeneity of permeability in oil reservoir. This EOR can be operated at low cost without expensive chemicals. Because the foam produced by P. aeruginosa is induced by proteins, the precipitation will not be formed in oil reservoir. The stability of protein-induced foam is higher than that of surfactant-induced foam in the presence of oil or high saline conditions. The microbial foam EOR therefore has high potential improving the heterogeneity of permeability in oil reservoir more effectively than the conventional foam EOR.

DOI： 10.2118/210696-MS

Scopus

Publisher：83rd EAGE Conference and Exhibition 2022  

Carbon dioxide (CO2) gas injection into depleted oil reservoirs is a promising approach to achieve the goal of a neutral carbon society. However, the heterogeneity of formation generally challenges the oil recovery efficiency. The CO2 gas injection preferably flows in the high permeability zone and leaves behind the remaining oil in the lower permeability region. This study presented a new CO2-Colloidal Gas Aphrons fluid to restrict fluid flow in the high permeability zone, and increase swept volume in the low permeability zone. We conducted dual parallel sandpacks with different permeabilities models to evaluate the plugging ability and oil recovery improvement of CO2-CGAs injection in heterogeneous porous media. The results reveal that CO2-CGAs can block the pore throat in the high permeability sandpack and change the flow direction to the low permeability sandpack. Overall, the sweep efficiency in the low permeability region was increased significantly, which led to an improvement in the total oil recovery factor by 39 %.

Scopus

Language：English   Publishing type：Research paper (scientific journal)  

The underlying effect of preflush salinity and silica nanofluid (Si-NF) on oil production is examined. The influence of salinity on the stability of Si-NFs is studied. A series of sand-pack floodings evaluating oil production was conducted at different concentrations of preflush salinity (0 to 4 wt.%), followed by the injection of a Si-NF (0.5 wt.%) at the trail of which postflush water was injected. The effluent water and solids were collected and analyzed using X-ray fluorescence (XRF). Interfacial tension (IFT) and contact angle measurements were conducted on the Si-NF in the presence of salinity to confirm the effect. The Si-NF became unstable and formed precipitate in the presence of salinity. The sand-pack flooding showed that when the preflush salinity was increased, the displacement efficiency (ED) using the Si-NF and postflush injection was increased (ED = 44%). The XRF of the precipitated effluent revealed that the preflush salinity and Si-NF caused mineral leaching, which triggered pore clogging. The IFT value reduced from 13.3 to 8.2 mN/m, and the wettability was altered to be more strongly water-wet when the salinity increased. The primary mechanisms of oil recovery using the Si-NF after preflush salinity is attributed mainly to the clogging mechanism. This clogging helps block the high-perm area, shift the fluid flow to the oil-trapped zone, and free the oil out. Other contribution mechanisms are IFT reduction and wettability alteration.

DOI： https://doi.org/10.3390/en14216922

Language：English   Publishing type：Research paper (scientific journal)  

DOI： https://doi.org/10.1021/acs.energyfuels.1c02333

Language：English   Publishing type：Research paper (scientific journal)  

The present work highlights the capacity of disparate lattice Boltzmann strategies in simulating natural convection and heat transfer phenomena during the unsteady period of the flow. Within the framework of Bhatnagar-Gross-Krook collision operator, diverse lattice Boltzmann schemes emerged from two different embodiments of discrete Boltzmann expression and three distinct forcing models. Subsequently, computational performance of disparate lattice Boltzmann strategies was tested upon two different thermo-hydrodynamics configurations, namely the natural convection in a differentially-heated cavity and the Rayleigh-Bènard convection. For the purposes of exhibition and validation, the steady-state conditions of both physical systems were compared with the established numerical results from the classical computational techniques. Excellent agreements were observed for both thermo-hydrodynamics cases. Numerical results of both physical systems demonstrate the existence of considerable discrepancy in the computational characteristics of different lattice Boltzmann strategies during the unsteady period of the simulation. The corresponding disparity diminished gradually as the simulation proceeded towards a steady-state condition, where the computational profiles became almost equivalent. Variation in the discrete lattice Boltzmann expressions was identified as the primary factor that engenders the prevailed heterogeneity in the computational behaviour. Meanwhile, the contribution of distinct forcing models to the emergence of such diversity was found to be inconsequential. The findings of the present study contribute to the ventures to alleviate contemporary issues regarding proper selection of lattice Boltzmann schemes in modelling fluid flow and heat transfer phenomena.

DOI： https://doi.org/10.3390/computation9060065

Language：English   Publishing type：Research paper (scientific journal)  

DOI： https://doi.org/10.1021/acsomega.1c00079

Language：English   Publishing type：Research paper (scientific journal)  

DOI： https://doi.org/10.1016/j.colsurfa.2021.126688

Language：Japanese   Publishing type：Research paper (scientific journal)  

In this study, pressure response at A monitoring well in early stage of CO2 geological storage were predicted against pressure build-up at CO2 injector after starting CO2 injection into a deep saline aquifer to design the monitoring well distance from the injector and resolution or sensitivity of a pressure transmitter installed in the monitoring well. The numerical simulations on pressure distributions and expanding CO2 plume front were carried out using a reservoir simulator, CMG-STARS, for the aquifer (10 km in radius, 50m in height) with open boundary under 1,000 m from the ground or seabed level. The ratio of pressure response at the monitoring well against the pressure build-up at the injector have been presented for various monitoring locations (500 to 5,000 m　from a injector) and homogeneous and heterogeneous models of horizontal permeability distribution in the aquifer (Base Model and Model 1, 2 & 3) and CO2 injection patters during 100 days (Scheme 1, 2 & 3). It has been presented from the numerical simulation results that the monitoring well radial distance from the injector is recommended to be 2,000 to 4,000 m or less than 1000 m when the resolution or sensitivity of the pressure transmitter is 1kPa or 10kPa, respectively.

DOI： https://doi.org/10.2473/journalofmmij.137.17

Language：English   Publishing type：Research paper (scientific journal)  

This study is intended to expand the scope of microbial enhanced oil recovery (MEOR) simulation studies from 1D to field scale focussing on fluid viscosity variation and heterogeneity that lacks in most MEOR studies. Hence, we developed a model that incorporates: (1) reservoir simulation of microbe-induced oil viscosity reduction and (2) field-scale simulation and robust geological uncertainty workflow considering the influence of well placement. Sequential Gaussian simulation, co-kriging and artificial neural network were used for the petrophysical modelling prior to field-scale modelling. As per this study, the water viscosity increased from 0.5 to 1.72 cP after the microbe growth and increased biomass/biofilm. Also, we investigated the effect of the various component compositions and reaction frequencies on the oil viscosity and possibly oil recovery. For instance, the fraction of the initial CO2 in the oil phase (originally in the reservoir) was varied from 0.000148 to 0.005 to promote the reactions, and more light components were produced. It can be observed that the viscosity of oil reduced considerably after 90 days of MEOR operation from an initial 7.1–7.07 cP and 6.40 cP, respectively. Also, assessing the pre- and post-MEOR oil production rate, we witnessed two main typical MEOR field responses: sweeping effect and radial colonization occurring at the start and tail end of the MEOR process, respectively. MEOR oil recovery factors varied from 28.2 to 44.9% OOIP for the various 200 realizations. Since the well placement was the same for all realizations, the difference in the permeability distribution amongst the realizations affected the microbes’ transport and subsequent interaction with nutrient during injection and transport.

DOI： 10.1007/s13202-020-00852-1

Language：English   Publishing type：Research paper (scientific journal)  

The CO₂ diffusion coefficients in crude oils were measured from curves of oil-swelling vs. elapsed time with CO₂ dissolution in the oils. The oil swelling was measured with CO₂ up to a pressure of 10 MPa at 50 °C. The swelling coefficient and diffusion coefficient of CO₂ and CH₄ gases in the oil column were compared with CH₄ gas. The diffusion coefficient of the heavy oil was evaluated as approximately 1.1–1.6% of that of bitumen. The swelling factors increased with pressure, and the diffusion coefficients in CO₂ supercritical range were more than twice as high as those in the CO₂ gas phase. An empirical equation to estimate gas solubility in crude oils vs. API gravity has been presented as well. Gas diffusion coefficients were shown to relate to oil viscosity based on the Stokes-Einstein formula and a new correlation between the two with the absolute average deviation (AAD%) of about 15.5%, derived.

DOI： 10.1016/j.petrol.2019.106823

Language：English   Publishing type：Research paper (scientific journal)  

Weathered and fractured crystalline basement is known as the important unconventional reservoir in the Cuu Long Basin. Naturally fractured reservoir plays a crucial role in oil exploration to contribute for hydrocarbon production in Vietnam. However, the complexity and heterogeneity of the fractures system in the basement reservoir are challenges for oil and gas production. They require the realistic simulation scenarios to estimate the hydrocarbon potential as well as field development plan of these reservoirs. Thus, this paper aims to propose the feasibility development scenarios to improve oil recovery factor for crystalline basement reservoir, X field, Cuu Long Basin, Vietnam. First, history matching process is validated for the model to fit the actual production data (reservoir pressure, pressure, water cut in each well) in order to approach closer the fluid flow behavior through the reservoir. The manual matching was selected to adjust the actual aquifer size and permeability distribution with limit simulation runs. Next, the highest reliability matching model which approximately reflects the actual fluid flow behavior can be used as the base case to forecast the future reservoir performance through the field development plan. The most potential scenario is to add six new infill production wells, two side track wells and two water injection wells. The forecasted results indicate that this scenario yields 8% more oil recovery factor compared to the natural drive with thirteen producers. This result suggests that the precise field development plan is to increase the efficiency of the production process by increasing the displacement parameters of residual oil and reservoir sweep efficiency by stimulation. The major contribution of this paper demonstrates the merits of the field development plan in fractured basement reservoir. The findings of this study can help better understand the fluid flow behavior using the production history profiles and field development scenarios of crystalline basement reservoir of Cuu Long Basin.

DOI： 10.1007/s13202-019-00755-w

Language：English   Publishing type：Research paper (scientific journal)  

Microbial influenced corrosion that associated with biofilm has been one of the major problem in industry. It causes damage to equipment and infrastructure because of rapid material deterioration and often resulting in pipeline failures. Pipeline failures can lead to large economic losses and environmental problems. Synthetic chemical biocides are commonly used to prevent corrosion but are not effective against preformed biofilm on pipes and toxic to the environment. A new antimicrobial is being developed by using biosurfactant produced by indigenous oil reservoir bacteria Bacillus sp. to prevent and eradicate biofilm. This study aims to determine minimum inhibitory concentration (MIC), minimum biofilm inhibitory concentration (MBIC), and minimum biofilm eradication concentration for 50% eradication (MBEC₅₀) of biosurfactant against biofilm forming bacteria isolated from oil resevoir, its effect on biofilm community structure and its ability to inhibit the corrosion rate of Carbon Steel ST37. MIC, MBIC, and MBEC₅₀ were determined using broth macrodillution technique, biofilm community structure were analyzed using total plate count method, and corrosion rate of steel were determined using weight loss method. Biofilm and corroded steel surface was also visualized using SEM-EDS. From this study, it is revealed that MIC, MBIC, and MBEC₅₀ values respectively are 62.5; 31.25; and 500 μg ml^-1. Biosufactant is able to inhibit Pseudomonas sp. 1 and Pseudomonas sp. 2 attachment to Carbon Steel ST37 surface and also able to eradicate preformed biofilm on steel surface. This study also showed the reduction of corrosion rate in Carbon Steel ST 37 as a result of biosurfactants treatment; from 4.56 10^-4 mm year^-1 to 3.31 10^-4 mm year^-1 based on MBIC value and from 5.18 10^-5 mm year ^-1 to 2.7 10^-5 mm year^-1 after biofilm eradication at MBEC value. The results showed that biosurfactant in this study could be a good candidate for a new anti-corrosion agent.

DOI： 10.1088/2053-1591/ab4948

Language：English   Publishing type：Research paper (scientific journal)  

Biosurfactants are one of the microbial bioproducts that are in most demand from microbial-enhanced oil recovery (MEOR). We isolated and screened potential biosurfactant-producing bacteria, followed by biosurfactant production and characterization, and a simulation of the MEOR application to biosurfactants in a sand-packed column. Isolate screening was conducted based on qualitative (hemolytic blood assay and oil-spreading test) and semi-qualitative (emulsification assay and interfacial tension measurement) parameters. Bacterial identification was performed using 16S rRNA phylogenetic analysis. Sequential isolation yielded 32 bacterial isolates, where Pseudomonas sp. G3 was able to produce the most biosurfactant. Pseudomonas sp. G3 had the highest emulsification activity (Ei = 72.90%) in light crude oil and could reduce the interfacial tension between oil and water from 12.6 to 9.7 dyne/cm with an effective critical-micelle concentration of 0.73 g/L. The Fourier transform infrared spectrum revealed that the biosurfactant produced was a glycolipid compound. A stable emulsion of crude extract and biosurfactant formed at pH 2–12, up to 100 °C, and with a NaCl concentration of up to 10% (w/v) in the response-surface method, based on the Box–Behnken design model. The sand-packed column experiment with biosurfactant resulted in 20% additional oil recovery. Therefore, this bacterium and its biosurfactant show potential and the bacterium is suitable for use in MEOR applications.

DOI： 10.1007/s13202-019-0619-8

Language：English   Publishing type：Research paper (scientific journal)  

This study aims to determine a baseline for natural soil carbon dioxide (CO2) flux at the surface based on long-term field measurements, with the ultimate purpose to detect the gas leakage atCO2 geological storage sites. CO2 surface monitoring is a tool that measures the safety and effectiveness of CO2 capture and storage (CCS), a technology which is believed to be a reliable approach to mitigate the CO2 emission. However, the fluctuations of naturally occurring CO2 in soil layers complicate the leakage detection as the soil connects both the underground layers and the atmosphere. In this regard, this study not only investigates the natural surface CO2 flux behavior but also develops an equation to estimate the surface CO2 flux with respect to the soil moisture content and temperature. To meet this end, two values within the CO2 flux equation were defined and calculated based on the field measurements; a,representing a water saturation–dependent value, and b,representing the temperature sensitivity (independent of the water saturation). The results show a good agreement between estimated and measured data. Upon which, the maximum baseline for surface CO2 flux was derived and used as a threshold to detect the potential CO2 leakage in the candidate field (INAS, Japan).

DOI： 10.1007/s10661-019-7724-5

Language：English   Publishing type：Research paper (scientific journal)  

A novel two-step preparation of a silica nanofluid (Si-NF) with potential for light oil recovery is herein presented. It was observed that a Si-NF, prepared by dispersing silica nanoparticles (Si-NPs) in poly(vinyl alcohol) (1%) under carbon dioxide gas bubbling, is stable for 30 days at a temperature as high as 55 °C without any visible sedimentation. Unstable Si-NFs formed siliceous gels whose strength depends on Si-NP load. The spectral characterization revealed that prepared Si-NFs consisted of silanols, carbonyls, and alcohols. As part of an effort to enhance the light oil production (API 31°), 1, 0.5, and 0.1 wt % Si-NPs were injected in waterflooded Berea sandstone at 55 °C. An increase in oil as high as 7.6% was achieved for the Si-NF with the highest Si-NP load (1 wt % Si-NP). Oil production encompassed the discontinuity of Si-NFs, channel plugging, wettability, and interfacial tension alterations.

DOI： 10.1021/acs.iecr.9b01629

Language：English   Publishing type：Research paper (scientific journal)  

Reduction of interfacial tension (IFT) between residual crude oil and formation fluids in oil reservoirs is the key to enhanced oil recovery (EOR) by surfactant flooding. However, adsorption of injected surfactant on minerals in the oil-bearing rock matrix reduces the effectiveness of this method. The present study investigated the effects of surfactant adsorption and desorption in the rock matrix on the oil recovery ratio achieved by surfactant-EOR. Sodium dodecylbenzene sulfonate (SDBS), a common surfactant in EOR, was used with Berea sandstone samples (rock particles and cores) as adsorbent. Adsorption of SDBS in the samples increased with concentration, and the static saturated amount was 0.9 mg-SDBS/g-rock for 1.0 wt% SDBS-water solution. If brine (1.0 wt% salinity) was injected after saturated adsorption of SDBS in the core, 83 % of adsorbed SDBS was desorbed into the brine (the reversibility effect). To clarify the reversibility effect in oil reservoirs, field scale numerical simulations were conducted for a typical 5 spot model (area: 180 m × 180 m, thickness: 60 m) using core-flooding data reported previously. By introducing the reversibility model into the simulations on of surfactant flooding injection of slugs of 0.1 PV and 0.3 PV into the initial reservoir, oil recovery factor showed differences of 2.3 % and 2.9 % compared to without the model, respectively. Injection of the surfactant solution after water-flooding caused a difference of only 0.4 %.

DOI： 10.1627/jpi.62.188

Language：English   Publishing type：Research paper (scientific journal)  

In this study, the theoretical approach and numerical modelling of coal spontaneous combustion were investigated considering the aging effect. Numerical simulations ofthree-dimensional coal piles in cubic wire-mesh baskets (WMBs) were performed using ANSYS FLUENT. A theoretical heat generation model was constructed that incorporated aging effect (using a decay-power factor, γ ), equivalent oxidation exposure time (EOE-time) theory, and moisture evaporation. The results from this model were compared with those obtained from the conventional Arrhenius equation, which does not take aging effect into account. The γ value required to accurately express the aging effect in conjunction with EOE-time theory was determined to be 4 × 10−5 s−1 for the low-rank coal used in this work. This value was obtained by comparing simulated and measured coal temperature-time curves in WMBs. A moisture evaporation model that included an estimated evaporation heat rate was applied, based on the difference between coal moisture ratio and air relative humidity. These models were employed to simulate the self-ignition behaviour of coal piles and to explore the different heating processes of wet and dry coals. Finally, the relationships between pile volume and both critical self-ignition temperature and critical lead time were presented for industrial management of coal piles.

DOI： 10.1080/13647830.2019.1644378

Language：English   Publishing type：Research paper (scientific journal)  

In this investigation, an environmentally benign and efficient way for gasification of low-rank coal under CO2 rich condition, rapid heating, and high pressure was investigated. Series of experimental and simulation studies were carried out to compare the combustion characteristics of the Shandong (SD) low rank coal and Datong (DT) bituminous coal. It was found that the gasification potential of the SD coal sample was higher than that of the DT coal sample under the conditions investigated. A gasification model was developed and validated to predict the gasification characteristics of the low rank coal based on the experimental and the gasification kinetic parameters. It was found that the gasification conditions resulting in effective gasification of the low rank coal (in terms of CH4, CO and H2 gases production) are 100% CO2 concentration, 37.5 J/s heating rate, and 0.5 – 1 MPa pressure range.

Language：English   Publishing type：Research paper (scientific journal)  

Laminar flow of oil-in-water (O/W) emulsion in a horizontal pipe has been simulated to quantify the effect of salinity of aqueous phase and water content on flow characteristics using computational fluid dynamics (CFD). Bitumen was dispersed in aqueous solution containing surfactant at different NaCl concentrations and water contents. Rheological parameter was obtained from the viscosity-shear rate profiles of the fluid. Numerical modeling and simulation was performed using a finite element simulation software. The case was simplified by considering the O/W emulsion as a stable, pseudo-homogeneous (single-phase) fluid within the conditions investigated. At flow reference temperature, Tref = 30 °C, the pressure drop obtained from emulsion with 30% water content was 931 Pa, compared to 84.6 Pa which was obtained from 50% water content (i.e. reference fluid without NaCl). In addition, the pressure drop of 239 Pa, 142 Pa, 124 Pa, and 82.9 Pa was obtained from O/W emulsion samples containing 70000 ppm, 40000 ppm, 20000 ppm, and 10000 ppm salinity in the aqueous phase, respectively. Furthermore, the maximum dynamic viscosity imposed by the fluid, was calculated as ≈81000 cP for the sample containing 30% water content compared to ≈14000 cP from the reference fluid. The dynamic viscosity obtained from 70000 ppm salinity content was ≈34000 cP compared to ≈20000 cP, ≈16000 cP, and ≈13000 cP calculated for 40000 ppm, 20000 ppm, and 10000 ppm salinity, respectively. Moreover, large reduction in pressure drop (99%) and dynamic viscosity (60–90%), regardless of the water content and salinity were obtained from the simulation.

DOI： 10.1080/01932691.2019.1614046

Language：English   Publishing type：Research paper (scientific journal)  

Biosurfactants are one of the microbial bioproducts that are in most demand from microbial-enhanced oil recovery (MEOR). We isolated and screened potential biosurfactant-producing bacteria, followed by biosurfactant production and characterization, and a simulation of the MEOR application to biosurfactants in a sand-packed column. Isolate screening was conducted based on qualitative (hemolytic blood assay and oil-spreading test) and semi-qualitative (emulsification assay and interfacial tension measurement) parameters. Bacterial identification was performed using 16S rRNA phylogenetic analysis. Sequential isolation yielded 32 bacterial isolates, where Pseudomonas sp. G3 was able to produce the most biosurfactant. Pseudomonas sp. G3 had the highest emulsification activity (Ei = 72.90%) in light crude oil and could reduce the interfacial tension between oil and water from 12.6 to 9.7 dyne/cm with an effective critical-micelle concentration of 0.73 g/L. The Fourier transform infrared spectrum revealed that the biosurfactant produced was a glycolipid compound. A stable emulsion of crude extract and biosurfactant formed at pH 2–12, up to 100 °C, and with a NaCl concentration of up to 10% (w/v) in the response-surface method, based on the Box–Behnken design model. The sand-packed column experiment with biosurfactant resulted in 20% additional oil recovery. Therefore, this bacterium and its biosurfactant show potential and the bacterium is suitable for use in MEOR applications.

DOI： https://doi.org/10.1007/s13202-019-0619-8

Language：English   Publishing type：Research paper (scientific journal)  

Thermal degradation characteristics of a Japanese oil sand at different heating rates (10, 20, and 30 °C/min), and 30 ml/min air flow rate have been investigated. The kinetic parameters have been calculated based on three stages of weight loss and/or the conversion of the sample. These include, stage 1 (SI): volatilization of moisture content and the light hydrocarbon (20–227 °C), stage 2 (SII): combustion of heavy hydrocarbon (227–527 °C), and stage 3 (SIII): oxidative decomposition of carbonaceous organic matter (502–877 °C). The results showed that the rate of change of the oil sand conversion with time View the MathML sourcedαdt was affected by the heating rate. The time taken by the system to reach 0.99 conversion was observed as 85, 50, and 35 min at the heating rates of 10, 20, and 30 °C/min, respectively. The frequency factor, A, at SI was between 0.09 and 0.54 min−1, while the activation energy, Ea, was 11.2–12.5 KJmol−1 (the percentage weight loss, Wt, was 0–3.6 %w/w; and the conversion, α, was 0–0.2.). At SII, the values of A and Ea were 2.1–5.5 min−1 and 17.6–19 KJmol−1, respectively (Wt = 3.1–15.88 %w/w; α = 0.17–0.86.). The value of A at SIII was 5.5E11–1.1E13 min−1, while Ea was 160–200 KJmol−1 (Wt = 15.33–17.99 %w/w; and α = 0.84–0.99).

DOI： 10.1016/j.ejpe.2017.08.001

Language：English   Publishing type：Research paper (scientific journal)  

In this study, forty-five crushed rock samples were formed from rock and coal particles of different sizes to simulate the crushed and fragmented condition of a goaf area in an underground coal mine. The porosity (φ) range of the crushed samples was based on field observations in actual goafs. The permeability (k) was measured by reducing the size of the fragments of the actual goaf to lab-scale particles. Ultrasonic wave velocity (VPG) and attenuation (β) were measured for different porosities, particle sizes and frequencies. The ratio of the seismic wavelength and particle size was adjusted to match that of the parameters in the goaf. The results showed that the measured permeability conformed to the Kozney-Carman (KC) equation with a percolation threshold porosity of 0.06. The permeability of the crushed rock was dependent on φ4. The variations of the seismic velocity (η) and attenuation (ξ) were defined based on the ratio of the seismic parameters of the crushed rock and intact rock. η showed a linear relationship with the square root of the tortuosity (τ) for τ = 5–10. ξ showed an approximately linear relationship with the porosity part of the KC equation. An empirical equation is proposed based on the KC equation, involving the seismic velocity, attenuation and particle size. The estimated permeability based on the modified KC equation showed good agreement with the measured data. The permeability of the actual goaf was estimated as 1.0 × 104–6.5 × 105 d based on the rock properties in the goaf.

DOI： 10.1016/j.jappgeo.2018.09.009

Language：English   Publishing type：Research paper (scientific journal)  

The large porosity areas widely present in the underground resulting from
natural hazards or artificial damages. The porosity and permeability are suggested
to be capable of estimating the mechanical and air flow conditions inside
the porous layer in the underground. To accurately measure the porosity
and permeability in the porous area is imperative. To address this issue, we
experimentally modeled some porous samples in large porosities by using
sandstone particles sieved to different sizes. Ultrasonic was employed to apply
on the porous sandstone samples to characterize the seismic velocity and attenuation. Permeability was also measured simultaneously to find a correlation
with the porosity. The results showed the seismic attenuation decrease as
the reduction of frequency and increasing particle size at the same porosity.
Seismic attenuation was strongly correlated to porosity and particle size. Velocity
showed a good relationship with the porosity change. Permeability was
highly dependent on the particle size especially in the higher porosity range.
The results indicated that it is possible to find a relationship between the permeability and seismic attenuation via the porosity and particle size.

DOI： 10.4236/gep.2018.65007

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.20431/2454-7980.0401004

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DOI： 10.20431/2454-7980.0304008

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DOI： 10.9734/BJECC/2017/38328

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DOI： 10.1016/j.petrol.2017.07.032

Repository Public URL： http://hdl.handle.net/2324/1912759

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DOI： 10.1021/acs.energyfuels.7b00409

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DOI： https://doi.org/10.1021/acs.energyfuels.6b02216

Repository Public URL： http://hdl.handle.net/2324/1932061

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DOI： https://doi.org/10.1016/j.juogr.2016.03.005

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DOI： https://doi.org/10.1021/acs.energyfuels.6b01822

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DOI： http://dx.doi.org/10.1021/acs.energyfuels.6b02060

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DOI： https://doi.org/10.1016/j.coal.2016.08.020

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DOI： http://dx.doi.org/10.1016/j.petrol.2016.06.040

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DOI： http://dx.doi.org/10.1007/s13202-015-0195-5

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DOI： https://doi.org/10.1016/j.ijggc.2016.04.001

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DOI： http://dx.doi.org/10.4236/eng.2016.86033

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Repository Public URL： http://hdl.handle.net/2324/1912758

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Repository Public URL： http://hdl.handle.net/2324/1935825

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Repository Public URL： http://hdl.handle.net/2324/1935826

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DOI： 10.1016/j.juogr.2015.05.005

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DOI： 10.1007/s13202-015-0195-5

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DOI： 10.1016/j.coal.2014.02.004

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DOI： 10.1016/j.psep.2014.04.001

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Pyrolysis, combustion, and gasification properties of pulverized coal and char in CO2-rich gas flow were investigated by using gravimetric-differential thermal analysis (TG-DTA) with changing O2%, heating temperature gradient, and flow rate of CO2-rich gases provided. Together with TG-DTA, flue gas generated from the heated coal, such as CO, CO2, and hydrocarbons (HCs), was analyzed simultaneously on the heating process. The optimum O2% in CO2-rich gas for combustion and gasification of coal or char was discussed by analyzing flue gas with changing O2 from 0 to 5%. The experimental results indicate that O2% has an especially large effect on carbon oxidation at temperature less than 1100°C, and lower O2 concentration promotes gasification reaction by producing CO gas over 1100°C in temperature. The TG-DTA results with gas analyses have presented basic reference data that show the effects of O2 concentration and heating rate on coal physical and chemical behaviors for the expected technologies on coal gasification in CO2-rich gas and oxygen combustion and underground coal gasification.

DOI： http://dx.doi.org/10.1155/2013/985687

Language：English   Publishing type：Research paper (scientific journal)  

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Combustion and gasification properties of pulverized coal and char have been investigated experimentally under the conditions of high temperature gradient of order 200◦C·s−1 by a CO2 gas laser beam and CO2-rich atmospheres with 5% and 10% O2. The laser heating makes a more ideal experimental condition compared with previous studies with a TG-DTA, because it is able to minimize effects of coal oxidation and combustion by rapid heating process like radiative heat transfer condition. The experimental results indicated that coal weight reduction ratio to gases followed the Arrhenius equation with increasing coal temperature; further which were increased around 5% with adding H2O in CO2-rich atmosphere. In addition, coal-water mixtures with different water/coal mass ratio were used in order to investigate roles of water vapor in the process of coal gasification and combustion. Furthermore, char-water mixtures with different water/char mass ratio were also measured in order to discuss the generation ratio of CO/CO2, and specified that the source of Hydrocarbons is volatile matter from coal.Moreover, it was confirmed that generations of CO and Hydrocarbons gases are mainly dependent on coal temperature and O2 concentration, and they are stimulated at temperature over 1000◦C in the CO2-rich atmosphere.

DOI： 10.1155/2012/241587

Language：English   Publishing type：Research paper (scientific journal)  

This paper investigates the preliminary strategies and tools for the implementation of CO 2 air capture and geological storage as a potential mitigation option in the future climate policy of Iran. It is a method to capture CO 2 directly from air and store it in geological structures based on large-scale industrial processes to enable the near-permanent sequestration of carbon. The reason for selecting this approach originates from its capability to mitigate CO 2 from all economic sectors with a single technology, while the conventional capture methods are designed only for mitigation of CO 2 from point sources of the power generation and industrial sectors. In order to facilitate the workflow of air capture as efficiently as possible, this study suggests some tools and directions for the selection of potential sectors and the prospective areas for the final site selection of the air capture units.

DOI： 10.2495/AIR120461

Language：Japanese   Publishing type：Research paper (scientific journal)  

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Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

This paper summarizes the capabilities of geographical information system (GIS) in CO2 capture and geological storage (CCS). GIS is emerging as a useful tool for the spatio-temporal analysis, techno-economic feasibility and environmental assessment of CCS projects. A review on the recent case studies reveals the applicability of geoinformation technology to the screening and analysis of emission sources, transportation and storage possibilities of CO2. This paper presents a survey on the methodologies, techniques and tools for modeling of the CO2 emission form stationary sources, CCS-GIS database development, spatial source-sink matching, and economic assessment.

DOI： 10.1016/j.egypro.2011.02.188

Language：English   Publishing type：Research paper (scientific journal)  

This research investigates the relationship between CO 2 emission and economic growth of Iran over 14 years from 1994 to 2007 using a national panel data set. The statistical and emission intensity methodologies are used for analyzing the data series. The study finds evidence supporting parameters which conclude the stability of significant correlation between CO 2 emission and economic development over time during the years under investigation in Iran. This relationship is investigated and discussed for the energy sectors of the country as well. The results confirm that in all sectors except of agricultural, there is a positive strong correlation between CO 2 emission and economic growth throughout the study period. In most sectors, CO2 emission intensity (the emission per unit of GDP) doesn't show increasing trends while the absolute emission is rapidly increasing by the economic growth.

DOI： 10.1007/s11027-010-9252-z

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

Repository Public URL： http://hdl.handle.net/2324/18391

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1007/s11027-010-9252-z

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (other academic)  

Research Topics on Resources Production and Safety Engineering (REPS), Kyuro SASAKI and Yuichi Sugai, Proceedings of International Workshop on Earth Resources Technology, 2007

Language：English   Publishing type：Research paper (international conference proceedings)  

A LABORATORY EXPERIMENTS FOR TRACER GAS DIFFUSION, N.P.WIDODO, K.SASAKI, Y.SUGAI, R.S.GAUTAMA, A.WIDIATMOJO, Proceedings of 4th International Workshop on Earth Science and Technology, 279-284, 2006

Language：English   Publishing type：Research paper (international conference proceedings)  

MEASUREMENTS OF CH4 AND CO2 ADSORPTION ISOTHERMS FOR COALS AND ITS ROLE TO ENHANCEING COAL BED METHANE AND CO2 SEQUESTRATION, P.Q.HUY, K.SASAKI and Y.SUGAI, Proceedings of 4th International Workshop on Earth Science and Technology, 271-278, 2006

Language：English   Publishing type：Research paper (international conference proceedings)  

GAS Production SYSTEM FROM METHANE HYDRATE LAYER BY HOT WATER INJECTION USING DUAL-HORIZONTAL WELLS, S.ONO, K.SASAKI and Y.SUGAI, Proceedings of 3rd International Workshop on Earth Science and Technology, 55-62, 2005

Language：English   Publishing type：Research paper (international conference proceedings)  

EFFECTS OF A GREEN TUFF ON ACTIVATING MICROORGANISMS, Y.SUGAI and K.SASAKI, Proceedings of 3rd International Workshop on Earth Science and Technology, 41-46, 2005

Language：English   Publishing type：Research paper (international conference proceedings)  

Enhancing SAGD Performance using Additional Steam Injector into Oilsand Reservoir with Lateral Shale Stringers, Kyuro Sasaki, Yuichi Sugai and Kodai Kato, 26th IEA Annual Workshop & Symposium on Enhanced Oil Recovery, 2005

Language：Japanese   Publishing type：Research paper (scientific journal)  

Hydrothermal Cracking of Polyethylene, Polypropylene, and/or Polystyrene Mixtures under Supercritical Water Condition, Atsushi KISHITA, Yuichi SUGAI, Shingo KOIZUMI, Fangming JIN, Heiji ENOMOTO and Takehiko MORIYA, Resources Processing, Vol.52, No.1, pp. 14～24, 2005

Language：Japanese   Publishing type：Research paper (scientific journal)  

Cracking of Polyethylene, Polypropylene, and Polystyrene with Suprcritical Water, Atsushi KISHITA, Yuichi SUGAI, Shinya TAKEMORI, Shingo KOIZUMI, Fangming JIN, Heiji ENOMOTO and Takehiko MORIYA, Resources Processing, Vol.52, No.1, pp. 14～24, 2005

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Application of Biotechnology for Resource Production and Environment Remediation, Y.SUGAI, Proc. of International Workshop on Resource Science and Engineering of Rare Metals, 363-368, 2004

Language：English   Publishing type：Research paper (international conference proceedings)  

Developments of Cold Storage in Underground Rock Mass and Refrigeration Cycle using CO2 Hydrates Formation, K.SASAKI and Y.SUGAI, Proceedings of International Workshop on Resource Science and Engineering of Rare Metals, 65-68, 2004

Language：English   Publishing type：Research paper (international conference proceedings)  

The Characteristic and Effective Utilization of the Green Tuff, Y.SUGAI and K.SASAKI, Proceedings of International Workshop on Resource Science and Engineering of Rare Metals, 195-196, 2004

Language：Japanese   Publishing type：Research paper (scientific journal)  

Characterization of a Water-insoluble Polymer Producing Bacterium Enterobacter sp. CJF-002 for MEOR, Journal of the Japan Petroleum Institute, Vol.47, No.4 (20040701) pp. 282-292