Kyushu University [Yuichi Sugai (Professor) Faculty of Engineering, Department of Earth Resources Engineering]

Yuichi Sugai

Last modified date：2023.11.22

Professor / Department of Earth Resources Engineering / Department of Earth Resources Engineering / Faculty of Engineering

Papers

1.	Alireza Safari, Lingping Zeng, Ronald Nguele, Yuichi Sugai, Mohammad Sarmadivaleh, Review on using the depleted gas reservoirs for the underground H₂ storage: A case study in Niigata prefecture, Japan, International Journal of Hydrogen Energy (Elsevier), https://doi.org/10.1016/j.ijhydene.2022.12.108, 48, 28, 10579-10602, 2023.04, 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..
2.	Danielle Poungui, Yuichi Sugai, Kyuro Sasaki, Ronald Nguele, Swelling Mechanisms Assessment of Water-based Drilling Mud by Polyvinyl Alcohol, Proceeding of Society of Petroleum Engineers - SPE/IATMI Asia Pacific Oil and Gas Conference and Exhibition 2022, https://doi.org/10.2118/210694-MS, SPE-210694-MS, 2022.10, 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..
3.	Miu Ito, Yuichi Sugai, Evaluation of the Potential of Foam Producing Microorganism Improving Heterogeneity of Permeability for Novel Microbial Foam EOR, Proceeding of Society of Petroleum Engineers - SPE/IATMI Asia Pacific Oil and Gas Conference and Exhibition 2022, https://doi.org/10.2118/210696-MS, SPE-201696-MS, 2022.10, 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..
4.	Theodora Noely Tambaria, Yuichi Sugai, Ferian Anggara, Experimental Measurements of CO₂ Adsorption on Indonesian Low-rank Coals under Various Conditions., Journal of Petroleum Exploration and Production Technology (Springer), https://doi.org/10.1007/s13202-022-01569-z, 13, 813-826, 2022.09, 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..
5.	Nam Nguyen Hai Le, Yuichi Sugai, Ronald Nguele, Enhanced Oil Recovery in Heterogeneous Reservoir by CO₂-Colloidal Gas Aphrons Fluid Injection., Proceeding of 83rd EAGE Annual Conference & Exhibition, https://doi.org/10.3997/2214-4609.202210546, 2022, 1-5, 2022.06, 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 %..
6.	Nam Nguyen Hai Le, Yuichi Sugai, Hung Vo-Thanh, Ronald Nguele, Ronald Ssebadduka, Ning Wei, Experimental investigation on plugging performance of CO₂ microbubbles in porous media, Journal of Petroleum Science and Engineering (Elsevier), https://doi.org/10.1016/j.petrol.2022.110187, 211, 110187, 2022.04, 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..
7.	Miu Ito, Yuichi Sugai, Fundamental Investigation on a Foam-Generating Microorganism and Its Potential for Mobility Reduction in High-Permeability Flow Channels, Energies (MDPI), https://doi.org/10.3390/en15072344, 15, 7, 1-14, 2022.03, 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..
8.	Takehiro Esaki, Yuichi Sugai, 24. Evaluation of SrBr2 hydration reaction rate with repeated cycling, Journal of Materials Science and Chemical Engineering (Scientific Research), https://doi.org/10.4236/msce.2022.102005, 10, 2, 53-61, 2022.02, 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..
9.	Theodora Noely Tambaria, Yuichi Sugai, Ronald Nguele, Adsorption Factors in Enhanced Coal Bed Methane Recovery: A Review, Gases (MDPI), https://doi.org/10.3390/gases2010001, 2, 1, 1-21, 2022.01, 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..
10.	Muhammad Alfiza Farhan, Yuichi Sugai, Nuhindro Priagung Widodo, Syafrizal, The Development of a Low-Cost Method for Monitoring Methane Leakage from the Subsurface of Natural Gas Fields, Methane (MDPI), https://doi.org/10.3390/methane1010003, 1, 1, 24-37, 2021.12, 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..
11.	Miu Ito, Yuichi Sugai, Study on Enhanced Oil Recovery Using Microorganism Generating Foam in Presence of Nanobubbles, Proceeding of Society of Petroleum Engineers - SPE/IATMI Asia Pacific Oil and Gas Conference and Exhibition 2021, SPE-205671-MS, 2021.10, 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..
12.	Tola Sreu, Kyuro Sasaki, Yuichi Sugai, Ronald Nguele, An Experimental Study of the Influence of the Preflush Salinity on Enhanced Oil Recovery Using Silica-Based Nanofluids, Energies (MDPI), https://doi.org/10.3390/en14216922, 14, 21, 1-17, 6922, 2021.10, 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..
13.	Nam Nguyen Hai Le, Yuichi Sugai, Ronald Nguele, Tola Sreu, Bubble size distribution and stability of CO₂ microbubbles for enhanced oil recovery: effect of polymer, surfactant and salt concentrations, Journal of Dispersion Science and Technology (Taylor & Francis), https://doi.org/10.1080/01932691.2021.1974873, 2021.09, 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.
14.	Miu Ito, Yuichi Sugai, Nanobubbles activate anaerobic growth and metabolism of Pseudomonas aeruginosa, Scientific Reports (Nature), https://doi.org/10.1038/s41598-021-96503-4, 11, (2021) 11:16858, 1-12, 2021.08, 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.
15.	Ronald Nguele, Hikaru Hirota, Yuichi Sugai, Kyuro Sasaki, Role of Polymer-Based Nanofluids on Asphaltene Adsorption during Carbon Dioxide (CO₂) Injection, Energy & Fuels (ACS), https://doi.org/10.1021/acs.energyfuels.1c02333, 35, 18, 14746-14757, 2021.08.
16.	Ronald Ssebadduka, Kyuro Sasaki, Ronald Nguele, Tumelo Kgetse Dintwe, Tiago Novaes, Yuichi Sugai, New Method to Predict the Viscosity of Bitumen Diluted with Light Oil Using a Modified Van Der Wijk Model under Reservoir Temperature and Pressure, ACS Omega (ACS), https://doi.org/10.1021/acsomega.1c00079, 2021.04.
17.	Aditya Dewanto Hartono, Kyuro Sasaki, Yuichi Sugai, Ronald Nguele, Computational Performance of Disparate Lattice Boltzmann Scenarios under Unsteady Thermal Convection Flow and Heat Transfer Simulation, Computation (MDPI), https://doi.org/10.3390/computation9060065, 9, 65, 1-21, 2021.05, 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..
18.	Ronald Nguele, Brian Adala Omondi, Soichiro Yamasaki, Shusaku Mandai, Kyuro Sasaki, Yuichi Sugai, Evaluation of CO₂-triggered and thermo-responsive gels for heterogeneous oil formations, Colloids and Surfaces A: Physicochemical and Engineering Aspects (Elsevier), https://doi.org/10.1016/j.colsurfa.2021.126688, 622, 5, 1-11, 2021.04.
19.	Hung Vo Thanh, Yuichi Sugai, Kyuro Sasaki, Application of artificial neural network for predicting the performance of CO₂ enhanced oil recovery and storage in residual oil zones, Scientific Reports (Nature), https://doi.org/10.1038/s41598-020-73931-2, 10, (2020) 10:18204, 1-16, 2020.10, 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..
20.	Nam Nguyen Hai Le, Yuichi Sugai, Kyuro Sasaki, Investigation of Stability of CO₂ Microbubbles—Colloidal Gas Aphrons for Enhanced Oil Recovery Using Definitive Screening Design, Colloids and Interfaces (MDPI), https://doi.org/10.3390/colloids4020026, 4, 2, 1-15, 2020.06, 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..
21.	Eric O. Ansah, Hung Vo Thanh, Yuichi Sugai, Ronald Nguele, Kyuro Sasaki, Microbe-induced fluid viscosity variation field-scale simulation, sensitivity and geological uncertainty, Journal of Petroleum Exploration and Production Technology, 10.1007/s13202-020-00852-1, 10, 5, 1983-2003, 2020.06, 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..
22.	Yuichi Sugai, Yukihiro Owaki, Kyuro Sasaki, Simulation Study on Reservoir Souring Induced by Injection of Reservoir Brine Containing Sulfate-Reducing Bacteria, Sustainability (MDPI), https://doi.org/10.3390/su12114603, 12, 11, 1-17, 2020.06, 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..
23.	Nao Miyazaki, Yuichi Sugai, Kyuro Sasaki, Yoshifumi Okamoto, Satohiro Yanagisawa, Screening of the Effective Additive to Inhibit Surfactin from Forming Precipitation with Divalent Cations for Surfactin Enhanced Oil Recovery, Energies (MDPI), https://doi.org/10.3390/en13102430, 13, 10, 2430-2445, 2020.05, 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..
24.	Ronald Ssebadduka, Hiroyuki Kono, Kyuro Sasaki, Yuichi Sugai, Ronald Nguele, Measurements of CO₂ molecular diffusion coefficients in crude oils from swelling-time curve and estimation using viscosity from the Stokes-Einstein formula, Journal of Petroleum Science and Engineering, 10.1016/j.petrol.2019.106823, 187, 2020.04, 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..
25.	Hung Vo Thanh, Yuichi Sugai, Ronald Nguele, Kyuro Sasaki, Robust optimization of CO₂ sequestration through a water alternating gas process under geological uncertainties in Cuu Long Basin, Vietnam, Journal of Natural Gas Science and Engineering (Elsevier), 10.1016/j.jngse.2020.103208, 76, 1-15, 2020.04, 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..
26.	Ngoc Thai Ba, Hung Vo Thanh, Yuichi Sugai, Kyuro Sasaki, Ronald Nguele, Trung Phi Hoang Quang, Minh Luong Bao, Nam Le Nguyen Hai, Applying the hydrodynamic model to optimize the production for crystalline basement reservoir, X field, Cuu Long Basin, Vietnam, Journal of Petroleum Exploration and Production Technology, 10.1007/s13202-019-00755-w, 10, 1, 31-46, 2020.01, 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..
27.	Eric O. Ansah, Hung Vo Thanh, Yuichi Sugai, Ronald Nguele, Kyuro Sasaki, Microbe-induced fluid viscosity variation field-scale simulation, sensitivity and geological uncertainty, Journal of Petroleum Exploration and Production Technology (Springer), 10.1007/s13202-020-00852-1, 2020.01, 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..
28.	Hung Vo Thanh, Yuichi Sugai, Ronald Nguele, Kyuro Sasaki, Integrated workflow in 3D geological model construction for evaluation of CO₂ storage capacity of a fractured basement reservoir in Cuu Long Basin, Vietnam, International Journal of Greenhouse Gas Control (Elsevier), 10.1016/j.ijggc.2019.102826, 90, 2019.11, 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..
29.	Isty Adhitya Purwasena, Dea Indriani Astuti, Nabiilah Ardini Fauziyyah, Dina Aurum Sari Putri, Yuichi Sugai, Inhibition of microbial influenced corrosion on carbon steel ST37 using biosurfactant produced by Bacillus sp., Materials Research Express, 10.1088/2053-1591/ab4948, 6, 11, 2019.10, 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..
30.	Dea Indriani Astuti, Isty Adhitya Purwasena, Ratna Eka Putri, Maghfirotul Amaniyah, Yuichi Sugai, Screening and characterization of biosurfactant produced by Pseudoxanthomonas sp. G3 and its applicability for enhanced oil recovery, Journal of Petroleum Exploration and Production Technology, 10.1007/s13202-019-0619-8, 9, 3, 2279-2289, 2019.09, 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..
31.	Salmawati Salmawati, K. Sasaki, Yuichi Sugai, Amin Yousefisahzbi, Estimating a baseline of soil CO2 flux at CO2 geological storage sites, Environmental Monitoring and Assessment, 10.1007/s10661-019-7724-5, 2019, 191:563, 1-12, 2019.08, 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)..
32.	Ronald Nguele, Sreu Tola, Hiroki Inoue, Yuichi Sugai, K. Sasaki, Enhancing oil production using silica-based nanofluids Preparation, stability, and displacement mechanisms, Industrial and Engineering Chemistry Research, 10.1021/acs.iecr.9b01629, 1-16, 2019.08, 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..
33.	Ichhuy Ngo, Falan Srisuriyachai, K. Sasaki, Yuichi Sugai, Ronald Nguele, Effects of reversibility on enhanced oil recovery using Sodium Dodecylbenzene Sulfonate (SDBS), Journal of the Japan Petroleum Institute, 10.1627/jpi.62.188, 62, 4, 188-198, 2019.07, 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 %..
34.	Hemeng Zhang, K. Sasaki, Xiaoming Zhang, Yuichi Sugai, Yongjun Wang, Numerical simulations on the self-heating behaviours of coal piles considering aging effect, Combustion Theory and Modelling, 10.1080/13647830.2019.1644378, 23, 6, 1169-1190, 2019.07, 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..
35.	Cong Wang, O. S. Alade, K. Sasaki, Yuichi Sugai, Experimental and simulation studies on gasification characteristics of a low-rank coal by rapid heating under CO2-rich condition, Journal of Applied Research and Technology, 16, 4, 255-266, 2019.06, 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..
36.	O. S. Alade, Dhafer Al Shehri, Mohamed Mahmoud, K. Sasaki, Yuichi Sugai, Evaluation of laminar flow of surfactant-stabilized bitumen-in-water emulsion in pipe using computational fluid dynamics Effects of water content and salinity, Journal of Dispersion Science and Technology, 10.1080/01932691.2019.1614046, 40, 1-12, 2019.05, 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..
37.	Mochammad Andy Natawijaya, Yuichi Sugai, Ferian Anggara, CO₂ microbubble colloidal gas aphrons for EOR application: the generation using porous filter, diameter size analysis and gas blocking impact on sweep efficiency, Journal of Petroleum Exploration and Production Technology (Springer), https://doi.org/10.1007/s13202-019-0680-3, 2019.05, 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..
38.	San Yee Khaing, Yuichi Sugai, Kyuro Sasaki, Myo Min Tun, Consideration of Influential Factors on Bioleaching of Gold Ore Using Iodide-Oxidizing Bacteria, Minerals (MDPI), https://doi.org/10.3390/min9050274, 9, 5, 274-285, 2019.05, 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..
39.	Hung Vo Thanh, Yuichi Sugai, Kyuro Sasaki, Impact of a new geological modelling method on the enhancement of the CO₂ storage assessment of E sequence of Nam Vang field, offshore Vietnam, Energy Sources, Part A: Recovery, Utilization, and Environmental Effects (Taylor & Francis), https://doi.org/10.1080/15567036.2019.1604865, 1-15, 2019.04, 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..
40.	San Yee Khaing, Yuichi Sugai, Kyuro Sasaki, Gold Dissolution from ore with Iodide-oxidising Bacteria, Scientific Reports (Nature), https://doi.org/10.1038/s41598-019-41004-8, 9, (2019) 9:4178, 1-11, 2019.03, 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..
41.	Dea Indriani AstutiIsty, Adhitya Purwasena, Ratna Eka Putri, Maghfirotul Amaniyah, Yuichi Sugai, Screening and characterization of biosurfactant produced by Pseudoxanthomonas sp. G3 and its applicability for enhanced oil recovery, Journal of Petroleum Exploration and Production Technology (Springer), https://doi.org/10.1007/s13202-019-0619-8, 2019.02, 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..
42.	Eric O. Ansah,Yuichi Sugai,Pierre Ronald Nguele Odou,Kyuro Sasaki, Integrated microbial enhanced oil recovery (MEOR) simulation: Main influencing parameters and uncertainty assessment, Journal of Petroleum Science and Engineering (Elsevier), 10.1016/j.petrol.2018.08.005, 171, 784-793, 2018.12, 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..
43.	Olalekan S. Alade, Kyuro Sasaki, Yuichi Sugai, Kojo T. Konadu, Eric O. Ansah, Bayonile Ademodi, Ryo Ueda, Kinetics of Thermal Degradation of A Japanese Oil Sand, Egyptian Journal of Petroleum, 10.1016/j.ejpe.2017.08.001, 27, 4, 505-512, 2018.12, 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)..
44.	Xiaochen Yang, Kyuro Sasaki, Xiaoming Zhang, Yuichi Sugai, Permeability Estimate of Underground Long-wall Goaf from P-wave Velocity and Attenuation by Lab-scale Experiment on Crushed Rock Samples, Journal of Applied Geophysics, 10.1016/j.jappgeo.2018.09.009, 159, 785-794, 2018.12, 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..
45.	Yuichi Sugai,Yukihiro Owaki,Kyuro Sasaki,Fuminori Kaneko,Takuma Sakai, Numerical modelling of the growth of sulfate-reducing bacteria indigenous to an oilfield in Japan, Petroleum Science and Technology (Taylor & Francis), https://doi.org/10.1080/10916466.2018.1496102, 36, 19, 1597-1604, 2018.09, 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)..
46.	Eric O. Ansah,Yuichi Sugai,Kyuro Sasaki, Geological tectonics and physio-chemical metrics as screening criteria for MEOR applicability in West Africa transform regional oil wells - a review, International Journal of Petroleum Engineering, http://dx.doi.org/10.1504/IJPE.2018.093164, 3, 2, 116-137, 2018.07, 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..
47.	Eric O. Ansah,Yuichi Sugai,Kyuro Sasaki, Modeling microbial-induced oil viscosity reduction: Effect of temperature, salinity and nutrient concentration, Petroleum Science and Technology (Taylor & Francis), 10.1080/10916466.2018.1463253, 1-7, 2018.05, 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..
48.	Xiaochen Yang, Kyuro Sasaki, Xiaoming Zhang, Yuichi Sugai, Experimental study on seismic attenuation and permeability of large porosity rock, Journal of Geoscience and Environment Protection, 10.4236/gep.2018.65007, 2018, 6, 80-90, 2018.05, 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..
49.	Isty Adhitya Purwasena,Yuichi Sugai, The analysis of bacterial diversity in high thermic-low salinity Oil Reservoirs prior to Microbial Enhanced Oil Recovery field test, Journal of Engineering and Applied Sciences, 10.3923/jeasci.2018.4104.4112, 13, 11, 4104-4112, 2018.01, 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..
50.	Hiroki Matsuda, Takafumi Yamakawa, Yuichi Sugai, Kyuro Sasaki, Numerical Prediction of Seabed Subsidence with Gas Production from Offshore Methane Hydrates by Hot-Water Injection Method, International Journal of Petroleum and Petrochemical Engineering, 10.20431/2454-7980.0401004, 4, 1, 18-32, 2018.01.
51.	Salmawati, Kyuro Sasaki, Yuichi Sugai, Estimating Surface CO2 Flux Based on Soil Concentration Profile, British Journal of Environment & Climate Change, 10.9734/BJECC/2017/38328, 7, 4, 214-222, 2017.12.
52.	Yuta Yoshioka, Kyuro Sasaki, Kyoichi Takatsu, Yuichi Sugai, Screening of Major Chemical Reactions in In-Situ Combustion Process for Bitumen Production from Oil Sands Reservoirs, International Journal of Petroleum and Petrochemical Engineering, 10.20431/2454-7980.0304008, 3, 4, 82-92, 2017.12.
53.	Evan Rosyadi Ogara, Yuichi Sugai, Kyuro Sasaki, Ferian Anggara, The Effect of Coal Characteristics on Adsorption and Desorption Gas at Indonesia Low Rank Coal, International Symposium on Earth Science and Technology 2017, 472-477, 2017.11.
54.	Ronald Nguele, Kyuro Sasaki, Yuichi Sugai, Hikmat Said-Al Salim, Ryo Ueda, Mobilization and Displacement of Heavy Oil by Cationic Microemulsions in Different Sandstone Formations, Journal of Petroleum Science and Engineering, 10.1016/j.petrol.2017.07.032, 157, 1115-1129, 2017.08.
55.	Yongjun Wang, Xiaoming Zhang, Yuichi Sugai, Kyuro Sasaki, Determination of Critical Self-Ignition Temperature of Low-Rank Coal Using a 1 m Wire-Mesh Basket and Extrapolation to Industrial Coal Piles, Energy & Fuels, 10.1021/acs.energyfuels.7b00409, 31, 7, 6700-6710, 2017.08.
56.	Yuichi Sugai, Junpei Mikumo, Keita Komatsu, Kyuro Sasaki, Experimental Investigation on the Availability of Yeast Cell Wall as an Interfacial Tension Reducer for Enhanced Oil Recovery, Journal of Petroleum & Environmental Biotechnology, 10.4172/2157-7463.1000329, 8, 3, 1-6, 2017.06, 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..
57.	San Yee Khaing, Sugeng Sapto Surjono, Jarot Setyowiyoto, Yuichi Sugai, Facies and Reservoir Characteristics of the Ngrayong Sandstone in the Rembang Area, Northeast Java (Indonesia), Open Journal of Geology, 10.4236/ojg.2017.75042, 7, 5, 608-620, 2017.05, 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..
58.	Yousefi-Sahzabi, A., Eda Unlu-Yucesoy, Kyuro Sasaki, Arif Widiatmojo, Yuichi Sugai, Turkish Challenges for Low-Carbon Society: Current Status, Government Policies and Social Acceptance, Renewable and Sustainable Energy Reviews, 68, 1, 596-608, 2017.02.
59.	Olalekan S. Alade, Kyuro Sasaki, Yuichi Sugai, Bayonile Ademodi, Junpei Kumasaka, Effect of Emulsication Process Conditions on the Properties of Water-in-Bitumen Emulsion, 石油技術協会誌, 82, 1, 73-84, 2017.02.
60.	Ronald Nguele, Kyuro Sasaki, Yuichi Sugai, Brian A. Omondi, Hikmat Said-Al Salim, Ryo Ueda, Interactions between Formation Rock and Petroleum Fluids during Microemulsion Flooding and Alteration of Heavy Oil Recovery Performance, Energy & Fuels, https://doi.org/10.1021/acs.energyfuels.6b02216, 31, 1, 255-270, 2017.01.
61.	San Yee KHAING, Sugeng Sapto SURJONO, Jarot SETYOWIYOTO, Yuichi Sugai, Petrography, Mineralogy and Reservoir Characteristics of the Ngrayong Sandstone in the Rembang Area, Northeast Java (Indonesia), International Symposium on Earth Science and Technology 2016, 216-222, 2016.12.
62.	E. Owusu ANSAH, C. E. ABBEY, Yuichi Sugai, D. K. ADJEI, Contamination of Food by Iron from Grinding Disc Mills, International Symposium on Earth Science and Technology 2016, 193-198, 2016.12.
63.	Ibrahim Al Hadabi, Kyuro Sasaki, Yuichi Sugai, Yousefi-Sahzabi, A., Steam Trap Control Valve for Enhancing Steam Flood Performance in an Omani Heterogeneous Heavy Oil Field, Journal of Unconventional Oil and Gas Resources, https://doi.org/10.1016/j.juogr.2016.03.005, 16, 113-121, 2016.12.
64.	Minoru Saito,Yuichi Sugai,Kyuro Sasaki,Yoshifumi Okamoto,Chencan Ouyang, Experimental and Numerical Studies on EOR Using a Biosurfactant, the Abu Dhabi International Petroleum Exhibition and Conference 2016, SPE-183496-MS, 2016.11, 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..
65.	Ibrahim Al Hadabi, Kyuro Sasaki, Yuichi Sugai, The Effect of Kaolinite on Water-In-Oil Emulsion Formed by Steam Injection during Tertiary Oil Recovery: A Case Study of an Omani Heavy Oil Sandstone Reservoir with a High Kaolinite Sludge Content, Energy & Fuels, https://doi.org/10.1021/acs.energyfuels.6b01822, 30, 12, 10917-10924, 2016.11.
66.	Olalekan S. Alade, Kyuro Sasaki, Ogunlaja, A.S., Yuichi Sugai, Bayonile Ademodi, Junpei Kumasaka, Thermal Tolerance and Compatibility of NaOH–Poly(vinyl alcohol) in Bitumen Emulsification for Improved Flow properties, Energy & Fuels, http://dx.doi.org/10.1021/acs.energyfuels.6b02060, 30, 11, 9310-9321, 2016.09.
67.	Olalekan S. Alade, Bayonile Ademodi, Kyuro Sasaki, Yuichi Sugai, Junpei Kumasaka, Ogunlaja, A.S., Adeniyi Sunday Ogunlaja, Development of Models to Predict The Viscosity of A Compressed Nigerian Bitumen and Theological Property of Its Emulsions, Journal of Petroleum Science and Engineering, http://dx.doi.org/10.1016/j.petrol.2016.06.040, 145, 1, 711-722, 2016.09.
68.	Ferian Anggara, Kyuro Sasaki, Yuichi Sugai, The Correlation between Coal Swelling and Permeability during CO2 Sequestration: A Case Study using Kushiro Low Rank Coals, Journal of Petroleum Exploration and Production Technology, https://doi.org/10.1016/j.coal.2016.08.020, 166, 62-70, 2016.09.
69.	Ronald Nguele, Kyuro Sasaki, Mohammad Reza Ghulami, Yuichi Sugai, Masanori Nakano, Pseudo-phase Equilibrium of Light and Heavy Crude oils for Enhanced Oil Recovery, Journal of Petroleum Exploration and Production Technology, http://dx.doi.org/10.1007/s13202-015-0195-5, 6, 3, 419-432, 2016.08.
70.	Very Susanto, Kyuro Sasaki, Yuichi Sugai, Wataru Kawasaki, Field Test Study on Leakage Monitoring at A Geological CO2 Storage Site using Hydrogen as a Tracer, International Journal of Greenhouse Gas Control, https://doi.org/10.1016/j.ijggc.2016.04.001, 50, 37-48, 2016.07.
71.	Hiroki Matsuda, Takafumi Yamakawa, Yuichi Sugai, Kyuro Sasaki, Gas Production from Offshore Methane Hydrate Layer and Seabed Subsidence by Depressurization Method, Engineering, http://dx.doi.org/10.4236/eng.2016.86033, 8, 6, 353-364, 2016.06.
72.	Ibrahim Al Hadabi, Kyuro Sasaki, Yuichi Sugai, Yousefi-Sahzabi, A., Steam Trap Control Valve for Enhancing Steam Flood Performance in an Omani Heterogeneous Heavy Oil Field, Journal of Unconventional Oil and Gas Resources, 14, 2016.05.
73.	Junpei Kumasaka, Kyuro Sasaki, Yuichi Sugai, Olalekan S. Alade, Masanori Nakano, Measurement of Viscosity Alteration for Emulsion and Numerical Simulation on Bitumen Production by SAGD Considering In-situ Emulsification, Journal of Earth Science and Engineering, 6, 1, 10-17, 2016.03.
74.	Chanmoly Or, Kyuro Sasaki, Yuichi Sugai, Masanori Nakano, Motonao Imai, Swelling and Viscosity Reduction of Heavy Oil by CO2-Gas Foaming in Immiscible Condition, SPE Reservoir Evaluation & Engineering, 19, 1, 1-12, 2016.03.
75.	Chanmoly Or, Kyuro Sasaki, Yuichi Sugai, Masanori Nakano, Motonao Imai, Preliminary Numerical Modelling of CO2 Gas Foaming in Heavy Oil and Simulations of Oil Production from Heavy Oil Reservoirs, The Canadian Journal of Chemical Engineering, 94, 3, 576-585, 2016.03.
76.	Olalekan S. Alade, Kyuro Sasaki, Yuichi Sugai, Bayonile Ademodi, Masanori Nakano, Bitumen Emulsification using A Hydrophilic Polymeric Surfactant: Performance Evaluation in The Presence of Salinity, Journal of Petroleum Science and Engineering, 138, 66-76, 2016.02.
77.	Ronald Nguele, Kyuro Sasaki, Hikmat Said-Al Salim, Yuichi Sugai, Arif Widiatmojo, Masanori Nakano, Microemulsion and Phase Behavior Properties of (Dimeric Ammonium Surfactant Salt – Heavy Crude Oil – Connate Water) System, Journal of Unconventional Oil and Gas Resources, 14, 62-71, 2016.01.
78.	Ronald Nguele, Mohammad Reza Ghulami, Kyuro Sasaki, Hikmat Said-Al Salim, Arif Widiatmojo, Yuichi Sugai, Masanori Nakano, Asphaltene Aggregation in Crude Oils during Supercritical Gas Injection, Energy & Fuels, 30, 2, 1266-1278, 2016.01.
79.	Arif Widiatomojo, Kyuro Sasaki, Nuhindro Priagung Widodo, Yuichi Sugai, Yousefi-Sahzabi, A., Ronald Nguele, Predicting Gas Dispersion in Large Scale Underground Ventilation: A Particle Tracking Approach, Building and Environment, 95, 171-181, 2016.01.
80.	Ronald Nguele, Kyuro Sasaki, Hikmat Said-Al Salim, Yuichi Sugai, Physicochemical and Microemulsion Properties of Oimeric Quaternary Ammonium Salts With Trimethylene Spacer for Enhanced Oil Recovery, Colloid and Polymer Science, 293, 12, 3487-3497, 2015.12.
81.	Arif Widiatmojo, Kyuro Sasaki, Yousefi-Sahzabi, A., Ronald Nguele, Yuichi Sugai, Atsushi Maeda, A Grid-free Particle Tracking Simulation for Tracer Dispersion in Porous Reservoir Model, Journal of Unconventional Oil and Gas Resources, 10.1016/j.juogr.2015.05.005, 11, 75-81, 2015.09.
82.	Ronald Nguele, Kyuro Sasaki, Yuichi Sugai, Mohammad Reza Ghulami, Masanori Nakano, Pseudo-phase Equilibrium of Light and Heavy Crude oils for Enhanced Oil Recovery, Journal of Petroleum Exploration and Production Technology, 10.1007/s13202-015-0195-5, 1-14, 2015.08.
83.	Olalekan S. Alade, Kyuro Sasaki, Yuichi Sugai, Bayonile Ademodi, Junpei Kumasaka, Masanori Nakano, Prospects of Bitumen Emulsification using a Hydrophilic Polymeric Surfactant, International Journal of Engineering Practical Research, 4, 1, 55-59, 2015.04.
84.	Yuichi Sugai, Keita Komatsu, Kyuro Sasaki, Estimation of IFT Reduction by a Biomass Material and Potential of Its Utilization for EOR, Society of Petroleum Engineers (SPE) Asia Pacific Oil and Gas Conference and Exhibition, SPE-176490-MS, 2015.10, 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..
85.	Arif Widiatomojo, Kyuro Sasaki, YOUSEFISAHZABI AMIN, Nguele Ronald, Yuichi Sugai, Atsushi Maeda, A Grid-Free Particle Tracking Simulation for Tracer Dispersion in Porous Reservoir Model, A Grid-Free Particle Tracking Simulation for Tracer Dispersion in Porous Reservoir Model, 11, 75-81, 2015.09.
86.	Yuichi Sugai, Very Susant, Kyuro Sasaki, Ryo Mori, Spectrophotometric determination of pH change of formation water under high CO2 pressure using a mixed pH indicator, Journal of MMIJ（資源・素材学会）, 131, 8,9, 518-523, 2015.08, 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 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. .
87.	Ronald Nguele, Kyuro Sasaki, Yuichi Sugai, Hikmat Said‐Al Salim, Mohammad Reza Ghulami, Masanori Nakano, Experimental Investigation of Brine Hardness and Its Induced Chemistry during Heavy Crude Recovery Through CO2 Injection , International Journal of Engineering Practical Research, 4, 1, 60-66, 2015.04.
88.	Wang Yongjun, Zhang Xiaoming, Yuichi Sugai, Kyuro Sasaki, A study on Preventing Spontaneous Combustion of Residual coal in A coal Mine Goaf, Journal of Geological Research, 1-8, 712349, 2015.03.
89.	Arif Widiatmojo, Kyuro Sasaki, Yuichi Sugai, Yoshiaki Suzuki, Hiroyuki Tanaka, Kagemi Uchida, Hiroyuki Matsumoto, Assessment of Air Dispersion Characteristic in Underground Mine Ventilation: Field Measurement and Numerical Evaluation , Process Safety and Environmental Protection, 93, 173-181, 2015.01.
90.	OR Chanmoly, Kyuro Sasaki, Yuichi Sugai, Masanori Nakano, Motonao Imai, Motonao Imai,Numerical simulation of CO2 gas microbubble of foamy oil, Energy Procedia, 63, 7821-7829, 2014.12.
91.	Yuichi Sugai, Keita Komatsu, Kyuro Sasaki, Kristian Mogensen, Martin Vad Bennetzen, Microbial-Induced Oil Viscosity Reduction by Selective Degradation of Long-Chain Alkanes, Abu Dhabi International Petroleum Exhibition and Conference, SPE-171850-MS, 2014.11.
92.	Haruhiro Suzuki, Amin Yousefi-Sahzabi, Yuichi Sugai, Hossein Yousefi, Kyuro Sasaki, Economical Considerations on CCS System for Geological Uncertainty and Injection Failure, International Journal of Energy Economics and Policy, 4, 4, 772-784, 2014.11.
93.	Isty Adhitya Purwasena, Yuichi Sugai, Kyuro Sasaki, Estimation of the potential of an anaerobic thermophilic oil-degrading bacterium as a candidate for MEOR, Journal of Petroleum Exploration and Production Technology (Springer), 10.1007/s13202-013-0095-5, 4, 2, 189-200, 2014.06, 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..
94.	Ferian Anggara, Kyuro Sasaki, Sandra Rodrigues, Yuichi Sugai, The effect of megascopic texture on swelling of a low rank coal in supercritical carbon dioxide, International Journal of Coal Geology (Elsevier), 10.1016/j.coal.2014.02.004, 125, 45-56, 2014.05.
95.	Yuichi Sugai, Yukihiro Owaki, Kyuro Sasaki, Fuminori Kaneko, Takuma Sakai, Numerical Prediction of Reservoir Souring Based on the Growth Kinetics of Sulfate-reducing Bacteria Indigenous to an Oilfield, Society of Petroleum Engineers (SPE) International Oilfield Corrosion Conference and Exhibition, 10.2118/169629-MS, SPE-169629-MS, 2014.05.
96.	Isty Adhitya Purwasena, Yuichi Sugai, Kyuro Sasaki, Petrotoga japonica sp. nov., a thermophilic, fermentative bacterium isolated from Yabase Oilfield in Japan, Archives of Microbiology (Springer), 10.1007/s00203-014-0972-4, 196, 5, 313-321, 2014.05.
97.	Arif Widiatmojo, Kyuro Sasaki, Yuichi Sugai, Hiroyuki Tanaka, Kagemi Uchida, Hiroyuki Matsumoto, Assessment of Air Dispersion Characteristic in Underground Mine Ventilation: Field Measurement and Numerical Evaluation, Process Safety and Environment Protection (Elsevier), 10.1016/j.psep.2014.04.001, In Press, 2014.04.
98.	Yuichi Sugai, Tayfun Babadagli, Kyuro Sasaki, Consideration of an effect of interfacial area between oil and CO2 on oil swelling, Journal of Petroleum Exploration and Production Technology (Springer), 10.1007/s13202-013-0085-7, 4, 105-112, 2014.03, 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. .
99.	Chanmoly Or, Kyuro Sasaki, Yuichi Sugai, Masanori Nakano, Motonao Imai, Experimental Study on Foamy Viscosity by Analysing CO2 Micro-Bubbles in Hexadecane, International Journal of Oil, International Journal of Oil, Gas and Coal Engineering, 2, 2, 11-18, 2014.03.
100.	Isty A. Purwasena, Yuichi Sugai, Kyuro Sasaki, Utilization of Natural Reservoir Brine in Enrichment Culture Medium: An Alternative Approach for Isolation of Anaerobic Bacteria from an Oil Reservoir, Petroleum Science and Technology (Taylor & Francis), 10.1080/10916466.2011.615365, 32, 7, 783-789, 2014.02, 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..
101.	Maneeintr Kreangkra, Kyuro Sasaki, Yuichi Sugai, Investigation of the Effects of Parameters on Viscosities and Correlation of Heavy Oil and Stability of Its Emulsion, Journal of the Japan Institute of Energy, 92, 9, 900-904, 2013.09.
102.	Yuichi Sugai, Kyuro Sasaki, Ryo Wakizono, Yasunori Higuchi, Noriyuki Muraoka, Considerations on the possibility of microbial clogging of re-injection wells of the wastewater generated in a water-dissolved natural gas field, International Biodeterioration & Biodegradation (Elsevier), http://dx.doi.org/10.1016/j.ibiod.2012.10.003, 81, 35-41, 2013.07, 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..
103.	Ferian Anggara, Kyuro Sasaki, Yuichi Sugai, Swelling Measurements of a Low Rank Coal in Supercritical CO2, International Journal of Geosciences, 4, 5, 863-870, 2013.07.
104.	Arif Widiatmojo, Kyuro Sasaki, Nuhindro P. Widodo, Yuichi Sugai, Discrete Tracer Point Method to Evaluate Turbulent Diffusion in Circular Pipe Flow, Journal of Flow Control, Measurement & Visualization, 1, 2, 57-68, 2013.07.
105.	Zhigang Li, Xiaoming Zhang, Yuichi Sugai, Jiren Wang, Kyuro Sasaki, Measurements of Gasification Characteristics of Coal and Char in CO2-Rich Gas Flow by TG-DTA, Journal of Combustion, http://dx.doi.org/10.1155/2013/985687, 2013, Article ID 985687, 15 pages, 2013.06, 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..
106.	Arif Widiatmojo, Kyuro Sasaki, Nuhindro P. Widodo, Yuichi Sugai, Johannes Shinaga, Haris Yusuf, Numerical Simulation to Evaluate Gas Diffusion of Turbulent Flow in Mine Ventilation System, International Journal of Mining Science and Technology, 23, 3, 349-355, 2013.05.
107.	Yuichi Sugai, Kyuro Sasaki, Keigo Yoshimura, Toshinori Yukitake, Shigenori Muta, Pilot study on the construction of several temperature-controlled multi-purpose rooms in a disused tunnel, Tunnelling and Underground Space Technology (Elsevier), 10.1016/j.tust.2012.06.009, 32, 180-189, 2012.11, 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..
108.	Ryo Mori, Yuichi Sugai, Kyuro Sasaki, Kazuhiro Fujiwara, Takamichi Nakamura, Experimental and Numerical Studies on the Microbial Restoration of Natural Gas Deposits in Depleted Oil Reservoirs Storing CO2, Society of Petroleum Engineers (SPE) Asia Pacific Oil and Gas Conference and Exhibition, SPE-158875-MS, 2012.10, 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..
109.	Ferian Anggara, Kyuro Sasaki, Yuichi Sugai, Swelling experiments of Kushiro coals in supercritical CO2, Proc. of the 18th Formation Evaluation Symposium of Japan, 2012.09.
110.	OR Chanmoly, Kyuro Sasaki, Yuichi Sugai, Masanori Nakano, Motonao Imai, Characteristics of Micro-bubble Foamy Oil Generation and Distribution, Proc. of the 18th Formation Evaluation Symposium of Japan, 2012.09.
111.	Yuichi Sugai, Ryo Mori, Kyuro Sasaki, Kazuhiro Fujiwara, Estimation of the Potential of Microbial Restoration of Natural Gas Deposit with CO2 Sequestration, Proc. of the International Symposium on Earth Science and Technology 2012, 15-20, 2012.09.
112.	Zhigang Li, Xiaoming Zhang, Yuichi Sugai, Jiren Wang, Kyuro Sasaki, Coal Gasification in High Pressure and High CO2 Concentration Atmosphere by Rapid Heating, Proc. of the International Symposium on Earth Science and Technology 2012, 391-397, 2012.09.
113.	Yuta Yoshioka, Kyuro Sasaki, Yuichi Sugai, A Kinetic Reaction Model for Bitumen Production from Oil Sands by In-Situ Combustion, Proc. of the International Symposium on Earth Science and Technology 2012, 347-351, 2012.09.
114.	OR Chanmoly, Kyuro Sasaki, Yuichi Sugai, Masanori Nakano, Motonao Imai, Characteristics of CO2 Gas Diffusivity and Solubility in the Crude Oil, Proc. of the International Symposium on Earth Science and Technology 2012, 279-283, 2012.09.
115.	Haruhiro Suzuki, Kyuro Sasaki, Yuichi Sugai, An Evaluation Study on CCS System against Geological Uncertainty and Troubles, Proc. of the International Symposium on Earth Science and Technology 2012, 233-236, 2012.09.
116.	Zhigang Li, Xiaoming Zhang, Yuichi Sugai, Jiren Wang, Kyuro Sasaki, Properties and Developments of Combustion and Gasification of Coal and Char in a CO2-Rich and Recycled Flue Gases Atmosphere by Rapid Heating, Journal of Combustion (Hindawi Publishing Corporation), 10.1155/2012/241587, 2012, Article ID 241587, 11 pages, 2012.07, 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..
117.	Amin Yousefi-SAHZABI, Kyuro Sasaki, Yuichi Sugai, Mitigating climate change by CO2 air capture and geological storage: Opportunities for Iran, WIT Transactions on Ecology and the Environment (WIT Press), 10.2495/AIR120461, 157, 525-534, 2012.04, 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..
118.	Yuichi Sugai, Isty A. Purwasena, Kyuro Sasaki, Kazuhiro Fujiwara, Yoshiyuki Hattori, Komei Okatsu, Experimental studies on indigenous hydrocarbon-degrading and hydrogen-producing bacteria in an oilfield for microbial restoration of natural gas deposits with CO2 sequestration, Journal of Natural Gas Science and Engineering (Elsevier), 10.1016/j.jngse.2012.01.011, 5, 31-41, 2012.03, 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..
119.	Zhigang Li, Xiaoming Zhang, Kyuro Sasaki, Yuichi Sugai and Jiren Wang, Characteristic Analyses of Gasification and Combustion of Different Coal Samples in CO2-Enriched and Recycled Flue Gases Atmosphere by Rapid Heating: Effects of O2 Concentration and H2O, Proceedings of Carbon Management Technology Conference 2012, 151261-MS, 2012.02.
120.	Yongjun WANG, Xiaoming ZHANG, Kyuro SASAKI and Yuichi SUGAI, The Study of Goaf and Coal Spontaneous Combustion in Haizi Colliery, Proc. of the International Symposium on Earth Science and Technology 2011, 177-182, 2011.12.
121.	Takafumi YAMAKAWA, Kyuro SASAKI and Yuichi SUGAI, Targeted Methane Hydrate Layer for Economical and Optimum Gas Production, Proc. of the International Symposium on Earth Science and Technology 2011, 251-252, 2011.12.
122.	Yusuke MATSUNAMI, Takafumi YAMAKAWA, Shinji ONO, Yuichi SUGAI and Kyuro SASAKI, An Analytical Model for Gas Production from Methane Hydrate Layer by Depressurization Method, Proc. of the International Symposium on Earth Science and Technology 2011, 253-258, 2011.12.
123.	Kreangkrai MANEEINTR, Tayfun BABADAGLI, Kyuro SASAKI and Yuichi SUGAI, Interfacial Tension Study of Heavy Oil Emulsion-Carbon Dioxide System by Using Pendant Drop Volume Analysis Method, Proc. of the International Symposium on Earth Science and Technology 2011, 265-270, 2011.12.
124.	Amin Yousefi-SAHZABI, Kyuro SASAKI, Debra J DAVIDSON, Yuichi SUGAI and Nasrollah ABADIAN, CO2 Mitigation Opportunities in Iran’s Economic Sectors: Directions and Tools for Air Capture Implementation, Proc. of the International Symposium on Earth Science and Technology 2011, 287-294, 2011.12.
125.	Amin Yousefi-SAHZAB, Kyuro Sasaki, Hossein YOUSEFI, Saied PIRASTEH, Yuichi Sugai, GIS Aided Prediction of CO2 Emission Dispersion from Geothermal Electricity Production, Journal of Cleaner Production (Elsevier), 19, 1982-1993, 2011.11.
126.	Arif WIDIATMOJO, Kyuro SASAKI and Yuichi SUGAI, Numerical Simulation Method on Turbulent Gas Diffusion phenomena in Mine Ventilation Network, Proc. of 22nd World Mining Congress & Expo, I, 731-737, 2011.09.
127.	Kyuro Sasaki, Ferian Anggara and Yuichi Sugai, Coal-Matrix Swelling by CO2 Adsorption and A Model of Permeability Reduction, Proc. of 22nd World Mining Congress & Expo, II, 593-598, 2011.09.
128.	Ryo Wakizono, Yuichi Sugai, Kyuro Sasaki, Yasunori Higuchi, Noriyuki Muraoka, Investigation of Indigenous Bacteria in Water-dissolved Natural Gas Fields for Preventing Microbial Clogging of Injection Wells, Society of Petroleum Engineers (SPE) Asia Pacific Oil and Gas Conference and Exhibition, SPE-145990-MS, 2011.09, 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..
129.	Ryo Mori, Yuichi Sugai, Kyuro Sasaki, Kazuhiro Fujiwara, Evaluation of the Potential of Microbial Restoration of Natural Gas Deposit with CO2 Sequestration by Investigating Indigenous Bacteria in a High CO2 Content Oilfield, Society of Petroleum Engineers (SPE) Asia Pacific Oil and Gas Conference and Exhibition, SPE-145898-MS, 2011.09, 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..
130.	Hiroshi ANDO, Yuichi SUGAI, Youhei KAWAMURA, Hirokazu OKAWA and Kyuro SASAKI, Development of PVT Viscosity Meter, Proc. of the 17th Formation Evaluation Symposium of Japan, O1-6, 2011.09.
131.	Ferian ANGGARA, Kyuro SASAKI and Yuichi SUGAI, Coal Swelling Experiments and Permeability Reduction on Coal Seam by CO2 Injection, Proc. of the 17th Formation Evaluation Symposium of Japan, H1-6, 2011.09.
132.	Very SUSANTO, Kyuro SASAKI, Yuichi SUGAI and Kazutoshi SUGIYAMA, Preliminary Study of Surface Monitoring CO2 Dispersion from Shallow Aquifer CO2 Released, Proc. of the 17th Formation Evaluation Symposium of Japan, G1-7, 2011.09.
133.	Yousefi-Sahzabi, A., Sasaki, K., Djamaluddin, I., Yousefi, H., and Sugai, Y., GIS modeling of CO2 emission sources and storage possibilities, Energy Procedia, 10.1016/j.egypro.2011.02.188, 4, 2831-2838, 2011.04, 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..
134.	Yousefi-Sahzabi, A., Sasaki, K., Yousefi, H., and Sugai, Y., CO2 emission and economic growth of Iran, Mitigation and Adaptation Strategies for Global Change, 10.1007/s11027-010-9252-z, 16, 1, 63-82, 2011.01, 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..
135.	Zhigang LI, Xiaoming ZHANG, Yuichi SUGAI, Jiren WANG and Kyuro SASAKI, Flue Gas Analysis of Low-temperature Oxidation of Coal Sample for Low O2 Concentration in a Mixture of N2/CO2 and Circulated Gas by Rapid Heating, International Symposium on Earth Science and Technology 2010, 557-562, 2010.12.
136.	Isty A. PURWASENA, Yuichi SUGAI and Kyuro SASAKI, A Novel Anaerobic Hydrocarbon Degrading Bacteria and The Prospect for Microbial Enhanced Oil Recovery, International Symposium on Earth Science and Technology 2010, 397-400, 2010.12.
137.	Takafumi YAMAKAWA, Shinji ONO, Akinori IWAMOTO, Yuichi SUGAI and Kyuro SASAKI, Numerical Modeling of a New Gas Production Method from Methane Hydrate Layers by Hot Water Injection and BHP Control Using 4pairs of Dual Horizontal Wells, International Symposium on Earth Science and Technology 2010, 393-396, 2010.12.
138.	Ferian ANGGARA, Kyuro SASAKI and Yuichi SUGAI, Site Selection Criteria for Geological CO2 Sequestration: A Case Study from Indonesia, Proceedings of International Symposium on Earth Science and Technology 2010, 381-386, 2010.12.
139.	Hiroyuki KONO, Kyuro SASAKI, Yuichi SUGAI, Kreangkrai MANEEINTR, Takashi TAKAHASHI, Daisuke ITO and Takashi OKABE , Swelling Factors and Diffusion Coefficients of CO2 in Heavy Oil, International Symposium on Earth Science and Technology 2010, 377-380, 2010.12.
140.	Kreangkrai MANEEINTR, Kyuro SASAKI, Yuichi SUGAI and Wonkyu LEE, Effect of Parameters on Viscosities of Heavy Oil and Its Emulsions, International Symposium on Earth Science and Technology 2010, 373-376, 2010.12.
141.	Keigo YOSHIMURA, Yuichi SUGAI, Kyuro SASAKI, Toshinori YUKITAKE and Shigenori MUTA, Utilization of an Underground Tunnel for Low-Environmental-Load Cold Storage, International Symposium on Earth Science and Technology 2010, 367-372, 2010.12.
142.	Arif WIDIATMOJO, Kyuro SASAKI, N. P WIDODO, Yuichi SUGAI, Gabriel ARPA and Johannes SINAGA, Tracer Gas Simulation in Complex Mine Ventilation Using Discrete Tracer Points Method, International Symposium on Earth Science and Technology 2010, 259-264, 2010.12.
143.	Takafumi YAMAKAWA, Shinji ONO, Akinori IWAMOTO, Yuichi SUGAI and Kyuro SASAKI , A Gas Production System from Methane Hydrate Layers by Hot Water Injection and BHP Control with Radial Horizontal Wells, Canadian Unconventional Resources & International Petroleum Conference, SPE-137801-PP, 2010.10.
144.	Kazuhiro FUJIWARA, Yoshiyuki HATTORI, Hiroshi OHTAGAKI, Takamichi NAKAMURA, Takahiro ASANO, Komei OKATSU, and Yuichi SUGAI, Research on Microbial Restoration of Methane Deposit with Subsurface CO2 Sequestration into the Depleted Oil Fields, IEA-EOR 31st Annual Symposium and Workshop, 2010.10.
145.	Maneeintr KREANGKRAI, Kyuro SASAKI and Yuichi SUGAI, Experiment and Numerical Simulation of Japanese Heavy Oil Recovery, Journal of Novel Carbon Resource Sciences, 2, 41-44, 2010.10.
146.	Phung Quoc HUY, Kyuro SASAKI, Yuichi SUGAI, Maneeintr KREANGKRAI and Tayfun BABADAGLI, Numerical Simulation of CO2 Enhanced Coal Bed Methane Recovery for a Vietnamese Coal Seam, Journal of Novel Carbon Resource Sciences, 2, 1-7, 2010.10.
147.	Amin YOUSEFI, Kyuro SASAKI and Yuichi SUGAI, GIS Modeling of CO2 Emission Sources and Storage Possibilities, 10th International Conference on Green House Gas Technology, 330, 2010.09.
148.	Zhigang LI, Yuichi SUGAI, Kyuro SASAKI, Xiaoming ZHANG and Jiren WANG, TG-DTA Measurements on Datong Coal Gasification By Providing CO2 Gas Effect of Oxygen Concentration, 10th International Conference on Green House Gas Technology, 167, 2010.09.
149.	Isty A. Purwasena, Yuichi Sugai, Kyuro Sasaki, Estimation of the Potential of an Oil-Viscosity-Reducing Bacterium Petrotoga sp. Isolated from an Oil Field for MEOR, Society of Petroleum Engineers (SPE) Annual Technical Conference and Exhibition, SPE-137568-MS, 2010.09.
150.	Phung Quoc HUY, Kyuro SASAKI and Yuichi SUGAI, Fundamental Parameters for CO2 Enhanced Coalbed Methane Recovery in Deep And Unminable Coal Seams in Quangninh Coalfield, Vietnam, International Conference on Advanced Mining for Sustainable Development, 419-432, 2010.09.
151.	Amin Yousefi-SAHZABI, Kyuro Sasaki, Hossein YOUSEFI, Yuichi Sugai, CO2 Emission and Economic Growth of Iran, Mitigation and Adaptation Strategies for Global Change (Springer), 10.1007/s11027-010-9252-z, 1-20-20, 2010.08.
152.	Phung Quoc HUY, Kyuro Sasaki, Yuichi Sugai, Satoshi Ichikawa, Carbon Dioxide Gas Permeability of Coal Core Samples and Estimation of Fracture Aperture Width, International Journal of Coal Geology (Elsevier), 83, 1-10, 2010.06.
153.	Kyuro SASAKI, Shinji ONO, Yuichi SUGAI, Norio TENMA, Takao EBINUMA and Hideo NARITA, Gas production from Methane Hydrate Sediment Layer by Thermal Stimulation with Hot Water Injection, 2010 Offshore Technology Conference, OTC-20592-PP, 2010.05.
154.	Tetsu YASUNAMI, Kyuro Sasaki, Yuichi Sugai, CO2 Temperature Prediction System in Injection Tubing Considering Supercritical Condition at Yubari ECBM Pilot-Test, Journal of Canadian Petroleum Technology (SPE), 49, 44-50, 2010.04.
155.	Kyuro Sasaki, Shinji Ono, Yuichi Sugai, Norio Tenma, Takao Ebinuma and Hideo Narita, A Thermal Gas Production System from Methane Hydrate Layers by Hot Water Injection, Proceedings of 2010 SPE Oil and Gas India Conference and Exhibition (OGIC2010), CD-ROM (SPE-129085-PP), 2010.01.
156.	Toshiya NIIMI, Yuichi SUGAI, Kyuro SASAKI, Kazuhiro FUJIWARA, Yoshiyuki HATTORI, Hiroshi OTAGAKI and Komei OKATSU, Screening of Oil-Degrading and Hydrogen-Producing Microorganisms for Microbial Conversion of CO2 into CH4 in Oil Reservoir, Proceedings of International Symposium on Earth Science and Technology 2009, 563-568, 2009.12.
157.	Isty Adhitya PURWASENA, Yuichi SUGAI and Kyuro SASAKI, Estimation of the Potential of Microbial EOR by Using Oil-degrading Bacteria, Petrotoga sp. Isolated from an Oilfield, Proceedings of International Symposium on Earth Science and Technology 2009, 543-550, 2009.12.
158.	Zhigang LI, Xiaoming ZHANG, Yuichi SUGAI, Jiren WANG and Kyuro SASAKI, Experimental Study on Combustion, Gasification and Adsorption of Coal in CO2 Rich Atmosphere, Proceedings of International Symposium on Earth Science and Technology 2009, 161-166, 2009.12.
159.	Ferian ANGGARA, Kyuro SASAKI, Hendra AMIJAYA, Yuichi SUGAI and Lucas Donny SETIJADJI, Preliminary Result: CO2 Adsorption Experiments on Indonesia Coal Seam, Proceedings of International Symposium on Earth Science and Technology 2009, 151-156, 2009.12.
160.	Pung Quoc HUY, Kyuro SASAKI, Yuichi SUGAI, Satoshi ICHIKAWA and Tayfun BABADAGLI, Visualization Study on Swelling of Coal Matrix in High Pressure CO2, Proceedings of International Symposium on Earth Science and Technology 2009, 145-150, 2009.12.
161.	Hiroyuki KONO, Kyuro SASAKI, Yuichi SUGAI, Kreankrai MANEEINTR, Takashi TAKAHASHI, Daisuke ITO and Takashi OKABE, Solubility Measurements of Gases into Heavy Oil by PVT Process, Proceedings of International Symposium on Earth Science and Technology 2009, 135-138, 2009.12.
162.	Gabriel ARPA, Kyuro SASAKI, Nuhindro Priagung WIDODO, Arif WIDIATMOJO and Yuichi SUGAI, A Comparative Study on Ventilation Efficiency in Dead Spaces Along Mine Airways Based on A Laboratory Model, and Mine Measurement, Proceedings of International Symposium on Earth Science and Technology 2009, 114-124, 2009.12.
163.	Arif WIDIATMOJO, Kyuro SASAKI, Gabriel ARPA, Yuichi SUGAI and Nuhindro Priagung WIDODO, A New Numerical Scheme for Discrete Tracer-Points Method to Simulate Gas Concentration in Mine Ventilation Network Flow, Proceedings of International Symposium on Earth Science and Technology 2009, 113-118, 2009.12.
164.	Hiroshi ANDO, Youhei KAWAMURA, Hirokazu OKAWA, Yuichi SUGAI and Kyuro SASAKI, Viscosity Measurement Method Using Induced EMF at Coil in PVT Apparatus, Proceedings of International Symposium on Earth Science and Technology 2009, 443-446, 2009.12.
165.	Isty Adhitya Purwasena, Yuichi Sugai, Kyuro Sasaki, Estimation of the Potential of an Oil-Viscosity-Reducing Bacteria, Petrotoga sp., Isolated from an Oilfield for MEOR, Proceedings of International Petroleum Technology Conference 2009 (IPTC2009), IPTC-13861-MS, 2009.12.
166.	Kyuro Sasaki, Gabriel Arpa, Arif Widiatmojo and Yuich Sugai, Flow Visualization and Tracer Gas Measurement for Gas and Particles Diffusion in Dead Spaces along a Mine Ventilation Airway, Proceedings of 11th International Symposium on Environmental Issues and Waste Management in Energy and Mineral Production (SWEMP 2009), CD-ROM, 2009.11.
167.	Isty Adhitya PURWASENA, Yuichi SUGAI and Kyuro SASAKI, The Effect of Nitrogen Sources on Enhancedment of Crude Oil Viscosity Reduction by a Novel Anaerobe Thermophilic Bacteria, Petrotoga sp., Proceedings of The 3rd International Symposium of Novel Carbon Resource Sciences, 152-160, 2009.11.
168.	Arif WIDIATMOJO, Kyuro SASAKI, Gabriel ARPA and Yuichi SUGAI, Discrete Tracer Points Method for Mine Ventilation Network, Proceedings of 11th International Symposium on Environmental Issues and Waste Management in Energy and Mineral Production (SWEMP 2009), CD-ROM, 2009.11.
169.	Pung Quoc HUY, Kyuro SASAKI and Yuichi SUGAI, Gas Adsorption Capacity to Evaluate CO2 Sequestration Potential in Quangninh　Coalfield, Vietnam, Mine Ventilation, Vol.2, Ed. D.C. Panigrahi Oxford & IBH Pub. (Proceedings of The 9th Mine Ventilation Congress, New Delhi INDIA), 2, 1031-1040, 2009.11.
170.	Gabriel ARPA, Kyuro SASAKI, Arif WIDIATMOJO and Yuichi SUGAI, Numerical Modeling of Diffusion Phenomena in Narrow Vein Mine Stope from Field Measurement and Scaled Laboratory, Mine Ventilation, Vol.2, Ed. D.C. Panigrahi Oxford & IBH Pub. (Proceedings of The 9th Mine Ventilation Congress, New Delhi INDIA), 2, 695-707, 2009.11.
171.	Arif WIDIATMOJO, Kyuro SASAKI, Gabriel ARPA, Yuichi SUGAI and Nuhindro Priagung WIDODO, Simulation of Diffusion using Discrete Points Movement Method and Effect of　Dead Space Volume in Mine Ventilation Airways, Mine Ventilation, Vol.2, Ed. D.C. Panigrahi Oxford & IBH Pub. (Proceedings of The 9th Mine Ventilation Congress, New Delhi INDIA), 2, 685-694, 2009.11.
172.	Kyuro Sasaki, Shinji ONO, Yuichi Sugai, Takao EBINUMA, Hideo NARITA, Gas Production System from Methane Hydrates Layers by Hot Water Injection using Dual Horizontal Wells, Journal of Canadian Petroleum Technology (SPE), 48, 10, 21-26, 2009.10.
173.	Phung Quoc Huy, Kyuro Sasaki, Yuichi Sugai, Takashi Kiga, Masaki Fujioka, Tomio Adachi, Effects of SO2 and pH Concentration on CO2 Adsorption Capacity in Coal Seams for CO2 Sequestration With Considerations for Flue Gas From Coal-Fired Power Plants, Journal of Canadian Petroleum Technology (SPE), 48, 10, 58-63, 2009.10.
174.	Hiroshi OTAGAKI, Kazuhiro FUJIWARA, Yoshiyuki HATTORI, Yuichi Sugai, Komei OKATSU, Varification of Microbial Activities for Microbial Restoration of Methane Deposit With Subsurface CO2 Sequestration into Depleted Oil Fields, Proc. of Society of Petroleum Engineers (SPE) Asia Pacific Oil and Gas Conference and Exhibition, SPE123596-MS, 2009.08.
175.	Yuichi Sugai, Toshiya Niimi, Kyuro Sasaki, Yoshiyuki Hattori, Tsukasa Mukaidani, Kazuhiro Fujiwara, Komei Okatsu, Basic Studies on Oil-Degrading and Hydrogen-Producing microorganisms for Microbial Conversion of CO2 into CH4 in Oil Reservoir, Proc. of The 2nd International Symposium of Novel Carbone Resource Science, VII-32-39, 2009.03.
176.	Isty A. Purwasena, Yuichi Sugai and Kyuro Sasaki, A Preliminary Study on Microbial Enhanced Oil Recovery using CO2 as a Nutrient Source, Proc. of The 2nd International Symposium of Novel Carbon Resource Science, VII-1-8, 2009.03.
177.	Gabriel Arpa, Kyuro Sasaki and Yuichi Sugai, Numerical Modeling of Diffusion Phenomena in Narrow Vein Mine Stope from Field Measurement and Scaled Laboratory, Proc. of The 2nd International Symposium of Novel Carbon Resource Science, III-55-63, 2009.03.
178.	Phung Quoc Huy, Kyuro Sasaki, Yuichi Sugai and Tran Tu Ba, Evaluation of In-situ Gas Content and Coalbed Methane Potential in Quangninh Coalfield, Vietnam, Proc. of The 2nd International Symposium of Novel Carbon Resource Science, VII-26-31, 2009.03.
179.	A. Widiatomojo, Kyuro Sasaki, N.P. Widodo, G. Arpa and Yuichi Sugai, Numerical Simulation of Diffusion in Mine Airways using Discrete Tracer Movement Method and Effect of Dead Spaces Area, Proc. of The 2nd International Symposium of Novel Carbon Resource Science, III-47-54, 2009.03.
180.	Machiko OKA, Yuichi SUGAI, Kyuro SASAKI and Kazuhiro FUJIWARA, Investigation of Autotrophic Bacteria and Oil-Degrading Bacteria inhabit oil reservoir for MEOR without Injection of Organic Nutrients, Proceedings of International Symposium on Earth Science and Technology 2008, 71-76, 2008.12.
181.	Yuichi SUGAI, Tayfun BABADAGLI and Kyuro SASAKI, Measurement of Swelling of Crude Oil due to Carbon Dioxide, Proceedings of International Symposium on Earth Science and Technology 2008, 143-148, 2008.12.
182.	Yuichi Sugai, Toshiya Niimi, Kyuro Sasaki, Yoshiyuki Hattori, Sanae Kano, Tsukasa Mukaidani, Kazuhiro Fujiwara and Komei Okatsu, Screening of Oil-Degrading and Hydrogen-Producing Microorganisms for Microbial Conversion of CO2 into CH4 in Oil Reservoir, Proceedings of CIPC/SPE GTS 2008 Joint Conference, SPE-115009-MS, 2008.06.
183.	Yuichi SUGAI, Machiko OKA and Kyuro SASAKI, Screening of Effective Thermophilic Microorganisms for Microbial Enhanced Oil Recovery, Proceedings of 2nd International Conference and Workshop on Earth Resources Technology, 2008.04.
184.	Yuichi Sugai, Hong Chengxie, Tadashi Chida, Heiji Enomoto, Simulation Studies on the Mechanisms and Performances of MEOR using Polymer Producing Microorganism Clostridium sp. TU-15A, Proc. of Society of Petroleum Engineers (SPE) Asia Pacific Oil and Gas Conference and Exhibition, SPE-110173-MS, 2007.10.
185.	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.
186.	Kyuro SASAKI and Yuichi Sugai, Research Topics on Resources Production and Safety Engineering (REPS), Proceedings of International Workshop on Earth Resources Technology, 2007.04.
187.	N.P.WIDODO, K.SASAKI, Y.SUGAI, R.S.GAUTAMA, A.WIDIATMOJO, A LABORATORY EXPERIMENTS FOR TRACER GAS DIFFUSION, Proceedings of 4th International Workshop on Earth Science and Technology, 279-284, 2006.12.
188.	P.Q.HUY, K.SASAKI and Y.SUGAI, MEASUREMENTS OF CH4 AND CO2 ADSORPTION ISOTHERMS FOR COALS AND ITS ROLE TO ENHANCEING COAL BED METHANE AND CO2 SEQUESTRATION, Proceedings of 4th International Workshop on Earth Science and Technology, 271-278, 2006.12.
189.	S.ONO, K.SASAKI and Y.SUGAI, GAS Production SYSTEM FROM METHANE HYDRATE LAYER BY HOT WATER INJECTION USING DUAL-HORIZONTAL WELLS, Proceedings of 3rd International Workshop on Earth Science and Technology, 55－62, 2005.12.
190.	Y.SUGAI and K.SASAKI, EFFECTS OF A GREEN TUFF ON ACTIVATING MICROORGANISMS, Proceedings of 3rd International Workshop on Earth Science and Technology, 41－46, 2005.12.
191.	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.
192.	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 .
193.	Kyuro Sasaki, Yuichi Sugai and Kodai Kato, Enhancing SAGD Performance using Additional Steam Injector into Oilsand Reservoir with Lateral Shale Stringers, 26th IEA Annual Workshop & Symposium on Enhanced Oil Recovery, CD-ROM, 2005.09.
194.	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 .
195.	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.
196.	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.
197.	Y.SUGAI, Introduction of Enhanced Oil Recovery Technique by using Microorganisms, Proceedings of 2nd International Workshop on Earth Science and Technology, 193－200, 2004.12.
198.	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 .
199.	Y.SUGAI, J.FANGMING, H.ENOMOTO and T.MORIYA, Application of Membrane Separation Method to Concentrate Products on the Process Producing Environmentally Adaptable Deicer by means of Wet Oxidation of Organic Wastes, RESOURCES PROCESSING, Vol.51、No.3、148－157, 2004.09.
200.	Y.SUGAI, Application of Biotechnology for Resource Production and Environment Remediation, Proc. of International Workshop on Resource Science and Engineering of Rare Metals, 363-368, 2004.08.
201.	Y.SUGAI and K.SASAKI, The Characteristic and Effective Utilization of the Green Tuff, Proceedings of International Workshop on Resource Science and Engineering of Rare Metals, 195-196, 2004.08.
202.	K.SASAKI and Y.SUGAI, Developments of Cold Storage in Underground Rock Mass and Refrigeration Cycle using CO2 Hydrates Formation, Proceedings of International Workshop on Resource Science and Engineering of Rare Metals, 165-168, 2004.08.
203.	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 .
204.	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 .
205.	Y.SUGAI, Application of Biotechnology for Enhanced Oil Recovery, Proceedings of Akita-Sfax Universities Joint Conference CMR-VBL’2004, 52-56, 2004.05.
206.	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 .
207.	Model analysis for super-wet in-situ combustion, SAKAMOTO Yasuhide, SUGAI Yuichi, ENOMOTO Heiji and HONG Chengxie, Journal of the Japanese Association for Petroleum Technology, Vol.69, No.1 (20040101) pp. 73-82.
208.	Investigation on a wet oxidation of crude oil for simulation study of super-wet in-situ combustion as an EOR, SAKAMOTO Yasuhide, SUGAI Yuichi, JIN Fangming, ENOMOTO Heiji and HONG Chengxie, Journal of the Japanese Association for Petroleum Technology, Vol.68, No.4 (20030701) pp. 282-290 .
209.	Experimental study in laboratory for phenomena in an oil formation and effect of enhanced oil recovery in the super-wet combustion, SAKAMOTO Yasuhide, SUGAI Yuichi, ENOMOTO Heiji and HONG Chengxie, Journal of the Japanese Association for Petroleum Technology, Vol.68, No.1 (20030101) pp. 102-110 .
210.	Consideration on behavior of oil-water-two phase flow in thermal EOR and effect of water flood on an oil recovery at high temperatures, SAKAMOTO Yasuhide, SUGAI Yuichi, ENOMOTO Heiji and HONG Chengxie, Journal of the Japanese Association for Petroleum Technology, Vol.67, No.6 (20021101) pp. 557-566.
211.	Y.SUGAI, Fundamental Studies on Microbial Enhanced Oil Recovery with Polymer Producer Clostridium sp. TU-15A, Proceedings of International Symposium on Microbial Enhanced Oil Recovery, 39-45, 2000.08.
212.	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.
213.	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 .
214.	Yuichi Sugai, Atsushi Kishita, Hong Chengxie, Heiji Enomoto, Tadashi Chida, S.C.ZHOU, Laboratory Investigation of Polymer Producer TU-15A for MEOR Field Tests, Proc. of Society of Petroleum Engineers (SPE) Asia Pacific Oil and Gas Conference and Exhibition, SPE-54381-MS, 1999.04.

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