記述言語：その他   掲載種別：研究論文（学術雑誌）  

We measured the P-wave velocities (VP) of mafic high-grade metamorphic rocks at 1.0 GPa pressure and a range of temperatures from 25 to 400 °C, along orthogonal directions corresponding to macroscopic fabric elements in the specimen. Our results showed that biotite-rich rocks (over 15 vol per cent biotite) displayed a strong decrease in VP with increasing temperature whereas biotite-free rocks did not. The anisotropy of VP (AVP) in biotite-rich rocks also increased with increasing temperature because of differential VP reduction, indicating a thermal dependence of the elastic properties of biotite. We conducted molecular dynamics simulations to investigate the effect of temperature on the elastic stiffness constants (Cij) of phlogopite, an end member of the biotite solid-solution series. The simulations indicated that Cij of phlogopite have a strong anisotropy and temperature dependence. We then estimated Cij of the bulk rock by using the Voigt-Reuss-Hill average procedure based on the estimated Cij of phlogopite, reference values for Cij of hornblende and plagioclase and measured crystal preferred orientations. From the resulting values of bulk-rock Cij, we calculated the quasi-VP and anisotropy parameter ϵ, under the assumption of transverse isotropy, and confirmed that temperature had a clear effect on velocity whereas AVP remained stable. This result suggests that the thermal effect on VP of biotite-rich rocks can be explained by the thermal dependence of Cij of phlogopite, which we attribute to a lattice rearrangement in phlogopite. This finding implies that the elastic properties of micas may change and affect the elastic properties of bulk rocks in the absence of mechanical breakage, dehydration reactions or phase changes. The thermal effect on AVP of biotite-rich rocks cannot be explained by a thermal dependency of the elastic constants of phlogopite. We speculate that the local concentration of thermal stress on biotite may account for the thermal dependency of AVP of biotite-rich rocks.

DOI： 10.1093/gji/ggac187

記述言語：その他   掲載種別：研究論文（学術雑誌）  

We analyzed the chemical and isotopic composition of the geothermal fluids from the Hatchobaru geothermal field in the Kyushu Island, Japan. Fluid chemistry showed similarity with that reported in earlier studies. Chemical geothermometry provided an estimated reservoir temperature of 250–300 °C. Helium and carbon isotopic ratios of the steam is likely to reflect the signature of the magmatic heat source. The apparent equilibrium temperature for carbon isotope exchange between CO2 and CH4 was 375–430 °C. The sulfur isotope data were in accordance with the idea that an acidic Cl-SO4-type fluid was modified from a neutral Cl-type fluid.

DOI： 10.1016/j.geothermics.2022.102379

記述言語：その他   掲載種別：研究論文（学術雑誌）  

Magnetotelluric (MT) surveys have revealed the existence of subvertical conductors at depths of several kilometers in the volcanic and geothermal areas of northern Japan. The conductive anomalies suggest that saline magmatic fluids are trapped within or in the vicinity of granitic intrusions and potentially form supercritical geothermal reservoirs. Detailed interpretation of the observed conductivity is a challenging task, as estimating the contributions of the pore fluids to the bulk conductivity of the systems requires specific information. Such information includes the in situ pressure, temperature, and salinity conditions in the conductors. In this study, we modeled magmatic fluids as H2O-NaCl fluids and developed a new approach to estimate the electrical conductivity of the fluids at elevated temperatures up to 525 °C and salinity up to 25 wt% NaCl. Using our developed approach, the possible ranges of fluid electrical conductivity were calculated under supercritical geothermal conditions. Further, we examined the pressure, temperature, and salinity conditions required to explain these observations. Our study showed that H2O-NaCl fluids in the vapor and halite coexistence states likely have extremely low conductivity that could not explain the observed conductors. This finding indicated that relatively shallow conductors located above 4 km could have abnormally high pressures if the phase relations of in situ fluids were close to those of the H2O-NaCl fluids. Salinity of more than 0.5 wt% NaCl is necessary for single-phase fluids to account for such observation. Whether the fluids in the liquid and vapor coexistence state could have such high conductivity is currently uncertain owing to a lack of experimental data. Further, our predictions about the depth variation of fluid conductivity indicated that near-lithostatic pressures, or extremely high temperatures (above 550 °C) under sufficiently high pressures are required to reproduce the observed nearly uniform distribution with depth. However, it is currently difficult to rule out the possibility that a shallower part of the conductors is cooled to approximately 400 °C, as MT inversion could have difficulty in accurately capturing a small variation in conductivity within the conductors.

DOI： 10.1016/j.geothermics.2022.102361

記述言語：その他   掲載種別：研究論文（学術雑誌）  

Magnetotelluric (MT) observations have revealed subvertical electrical conductors that extend from shallow depths into the mid-crust at various geothermal zones, active volcanoes and active faults worldwide. These deeply rooted subvertical conductors have typically been interpreted to represent entire zones of dedicated fluid transport through the crust. We estimate the high-resolution 3-D crustal resistivity structure below the Kuju Volcanoes, Japan, using dense observations from 153 broad-band MT measurement sites and 40 telluric measurement sites. The resistivity structure highlights subvertical conductors that merge into a deep conductor to the north of the volcanoes, with deep low-frequency earthquakes occurring near the southeastern edge of this subvertical conductor at 10-30 km depth. This deep conductor branches into several subvertical conductors at 2-10 km depth, coinciding with a shallow zone where tectonic earthquakes rarely occur. The surface expressions of active geothermal areas and past volcanic eruptions are all located above the edges of the conductors at 2-6 km depth. Widespread conductive layers exist around the volcanoes above 2 km depth, and their distribution approximately corresponds to a low-gravity-anomaly zone. We discuss the nature of these subvertical conductors, the potential causes of their complex structure and their relationship to local magmatic fluid transport. These subvertical conductors, a shallow clay-rich layer, developed fracture systems and high-strength solidified magma may all contribute to magmatic fluid transport to the surface at the Kuju Volcanoes. In this study, we add the possibility that the edges of these subvertical conductors act as important magmatic fluid pathways.

DOI： 10.1093/gji/ggab368

記述言語：その他   掲載種別：研究論文（学術雑誌）  

This study proposes a new viscosity-dependent empirical model to calculate the electrical conductivity of H2O-NaCl fluids at elevated-temperature and high-salinity conditions. The proposed model is developed based on the experimental data of Bannard (1975), which covers a wide range of pressure, temperature, and salinity conditions, i.e., pressures up to 200 MPa, temperatures up to c.a. 525 ∘C, and NaCl concentrations from 0.06 to ca. 25 wt&#37; NaCl. To the author's knowledge, this is the first model which is fully consistent with the experimental data of Bannard (1975). A comparison study with existing conductivity models showed that the proposed model can predict the conductivity of H2O-NaCl fluids with higher accuracy particularly at temperatures above 200 ∘C. On the other hand, detailed verification of the proposed model indicated that extrapolation of the proposed model to the low fluid density conditions (< 400 kg/cm3) may produce large errors (> 30&#37;). Furthermore, we discussed pressure- and salinity-dependence of the fluid conductivity at elevated temperatures, as well as the bulk property of the two-phase (vapor-liquid) fluids, using the proposed model.

DOI： 10.1016/j.fluid.2021.113187

記述言語：その他   掲載種別：研究論文（学術雑誌）  

We conducted a comprehensive experimental study on the effect of the CO2 injection rate (flow rate: represented by the macroscopic capillary number, Nc) on CO2 saturation (SCO2) and the CO2 distribution in porous, brine-saturated Berea sandstone. We measured two independent geophysical parameters, P-wave velocity (Vp) and electrical resistivity (ρ*), to monitor the two-phase flow. Vp showed clear dependency on SCO2 in the transition zone between the capillary limit (CL) and the viscous limit (VL), but not near the CL. The Vp−SCO2 relationship showed that the characteristic size of connected CO2 volumes decreased with increasing Nc, whereas resistivity increased continuously with increasing SCO2. Therefore, resistivity is sensitive to SCO2 under flow conditions between the CL and VL. The ρ*–SCO2 relationship showed that CO2 penetration increased with increasing Nc. These results indicate that we can use Vp and ρ* to monitor CO2 flow in pore spaces because the injected CO2 forms pathways and replaces brine under a wide range of Nc values.

DOI： 10.1016/j.ijggc.2020.103228

記述言語：その他   掲載種別：研究論文（学術雑誌）  

It has been suggested that a large amount of crustal fluid is trapped at a supercritical state within intrusive rocks beneath volcanoes or calderas near the mountain ranges of northeastern Japan. If we could extract and use these crustal fluids, we could expect to achieve a high level of energy productivity. We have collated field data on high-temperature geothermal areas of the world, used these to produce simple models of their geothermal systems, and then explored their features in terms of the amount of potential power generation. For example, a potential of around 0.1 GW per reservoir over 30 years is expected in northeastern Japan if we consider supercritical reservoirs extending to a 5 km depth.

DOI： 10.1016/j.geothermics.2019.07.002

記述言語：その他   掲載種別：研究論文（学術雑誌）  

Fluid-flow tests and simultaneous measurements of water saturation (S ), complex resistivity and elastic wave velocity were conducted in the laboratory to elucidate the relationship between these properties in fractured andesite. The elastic wave velocity showed almost no dependence on S while the resistivity decreased with increasing S (up to 800 Ω m for 5% < S < 15%). Changes in the resistivity of the rock were also detected when the salinity and fracture porosity changed (1 order of magnitude difference in resistivity with a change of ~1 order of magnitude salinity or with ~2.5 times the porosity change). Our experimental results suggest that the resistivity is a suitable parameter for monitoring the artificial recharge into a depleted reservoir in the early stages of an Enhanced Geothermal System. w w w w

DOI： 10.11367/grsj.41.53

記述言語：日本語  

<p>地震探査，電磁探査をはじめとした物理探査による地下流体の分布評価は，地熱資源をはじめとした流体資源の開発に不可欠であり，その探査精度を向上するためには岩石の物理的性質を実験的に詳細に調べる必要がある。本研究では，地熱貯留層を構成する岩石の水飽和度と複素比抵抗ならびに弾性波の関係を実験的手法によって明らかにすることを目的とし，岩石コアの室内透水試験を行った。実験供試体は，既存のマクロクラックに加え人工的に熱性亀裂を造成した安山岩（空隙率10.5%）のコア試料を用い，封圧20 MPa，温度25 ℃の条件下で透水試験中の水飽和度，浸透率，複素比抵抗（測定周波数10^－2−10⁵ Hz）および弾性波（P波，測定周波数250 kHz）を測定した。透水試験では，地熱貯留層内の水飽和度変化を再現するため，はじめに過熱蒸気を模擬した窒素ガスで空隙を充填させたのち，塩水（1 wt-% KCl溶液）を一定圧力で注入する窒素−塩水置換試験を行った。この試験の結果，塩水注入前の複素比抵抗は10⁴ Ωmのオーダーであったのに対し，注入後の複素比抵抗は2桁低い10² Ωmのオーダーとなった。また水飽和度の上昇に伴う複素比抵抗の連続的な減少が確認され，この水飽和度と複素比抵抗の相関には有意な周波数依存性は認められなかった。同時に測定していたP波速度は，注入水圧や水飽和度の変化によってほとんど変化しなかった一方で，P波の振幅には水飽和度の上昇に伴う連続的な減衰が認められた。これらの結果から，複素比抵抗はP波速度に比べて微細な水飽和度の変化に対する感度が高いことが明らかとなり，地熱貯留層における緩やかな水飽和度の変化が，複素比抵抗によってモニタリング出来る可能性が示唆された。また水飽和度の上昇に伴うこれら物性値の変化から，本研究試料内の窒素−塩水二相流体流動挙動は2つのステージに分けられることが推察された。</p>

DOI： 10.3124/segj.71.71

記述言語：英語   掲載種別：研究論文（学術雑誌）  

In this study, we attempt to clarify the heterogeneous CO2 distribution in homogeneous and high-permeability porous sandstone (Mt. Simon sandstone: 105 mD) using both physical rock experiments and fluid mechanical analyses. In particular, the experiments involve CO2 injection into porous sandstone with measurements of P-wave velocity (Vp) and strain under low capillary number (Ca) flow conditions. We set three Vp-measurement lines and two strain gauges (vertical and horizontal) at the center of the core. We also monitor changes of flow rate, volume, and differential pressure between the two pumps during CO2 injection. The Vp values of all channels show slight changes (under 4&#37;). By contrast, the strain measurements indicate a substantial expansion in both directions. It is proposed that the injected CO2 reaches the counter end of the core specimen immediately and forms few large-percolation clusters in porous sandstone. The CO2 that follows flows only through clusters as pathways without capillary resistance. These CO2 flows produce spatially heterogeneous distributions of CO2 in the porous sandstone and make it difficult to monitor and detect CO2 by seismic wave velocities only.

DOI： 10.1016/j.ijggc.2018.03.005

記述言語：その他   掲載種別：研究論文（その他学術会議資料等）  

For developing the technique of Enhanced Geothermal System (EGS), the estimation of injected water distribution is essential. To estimate water saturation changes deep under the ground, geophysical explorations (e.g., seismic and electromagnetic explorations) have been applied; however, the relationship between the electric/elastic properties and the water saturation in reservoir rocks has not been well known. Our goal is to elucidate this basic relationship as well as effects of salinity and fracture porosity on it via fluid-flow experiments for more quantitative interpretation of geophysical explorations. In this research, we prepared two types of specimen from geothermal reservoir rocks; A) contains artificially induced thermal cracks (porosity = 10.5%) and B) initially contains a single fracture (porosity = 3.8%). In fluid-flow tests, specimens were initially filled with nitrogen gas (10 MPa of pore pressure) under 20 MPa of confining pressure; the gas emulates the superheated steam that is observed in the geothermal fields. Then, brine (0.1 and 1wt%-KCl) which emulates the artificial recharge to the reservoir, was injected into the samples (11-16 MPa of injection pressure). During the tests, water saturation, permeability, complex resistivity (in the frequency range of 10-2-105 Hz) and elastic wave velocity were simultaneously measured. As a result of Type A specimen, resistivity dramatically decreased from 104 to 102 Ω due to the brine injection. However, P-wave velocity was almost constant (the difference was less than 1%) at that time. These results indicate that resistivity could be sensitive to minor changes in water saturation in the reservoirs compared with P-wave velocity. As a result of Type B specimen, we observed salinity effect on resistivity (the resistivity difference between 0.1 and 1wt%-KCl brine was almost twice) and its decreasing trend against the water saturation was different from the result of Type A specimen. These dependencies (water saturation, salinity, and porosity) on resistivity could be explained by the total ion content within a specimen.

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

記述言語：日本語   掲載種別：研究論文（国際会議プロシーディングス）  

記述言語：日本語   掲載種別：研究論文（国際会議プロシーディングス）  

記述言語：英語   掲載種別：研究論文（その他学術会議資料等）  

Evaluating and monitoring the CO2 behavior in the reservoir, understanding the mechanism of CO2 flow and distribution in the water-CO2 mixture state is essential. In this study, measurement of the complex electrical impedance (Z) and P-wave velocity (V-p) is conducted during the CO2 injection into the rock core under the reservoir condition. Specimen is low permeable sandstone and injection rate is ultra-low (in the low capillarity number (C-n) area) to high. In addition to measuring Z and V-p, differential pressure on the both sides of the specimen and CO2 saturation (S-CO2) of the entire specimen are measured. The change of Z and Vp are observed according to the change of differential pressure and S-CO2. After the injection test, SCO2 in cross-section of the specimen is estimated using Archie's law and Gassmann's equation (Patchy saturation model) to the experimental results. (C) 2017 The Authors. Published by Elsevier Ltd.

DOI： 10.1016/j.egypro.2017.03.1629

記述言語：英語   掲載種別：研究論文（その他学術会議資料等）  

Two-phase flow is important to discuss the displacement mechanism between brine and super critical CO2 in the reservoir. The capillary number (Ca) is essential parameter to control the CO2 flow in porous sandstone. In this study, we try to estimate the effect of Ca on CO2 behavior by CO2 injection experiment. The CO2 is injected porous sandstone with changing flow rate (FR) and measure P-wave velocity (Vp) and electrical impedance (Z), simultaneously. The CO2 produces very low Ca-flow in porous sandstone. Vp indicates rapidly reduction with increasing Ca under this CO2-flow condition. On the other hand, Z shows clearly increment with increasing Ca. Both of parameters mean the increasing CO2 saturation (SCO2) with increasing Ca.

DOI： 10.1016/j.egypro.2017.03.1636

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.egypro.2017.03.1629

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.egypro.2017.03.1636

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

記述言語：日本語   掲載種別：研究論文（国際会議プロシーディングス）  

記述言語：日本語   掲載種別：研究論文（国際会議プロシーディングス）  

記述言語：英語   掲載種別：研究論文（その他学術会議資料等）  

A pilot CCS project in Indonesia will be implemented in Gundih area, Central Java Province in Indonesia. Before the CO2 injection, the reservoirs for CO2 injection must be characterized carefully by conducting geophysical exploration as well as reservoir simulation, in order to make sure that the reservoir is suitable for CO2 storage. Here we report results of reservoir characterization and simulation for the determination of CO2 injection site in the Gundih area. Subsurface structures imaged on seismic reflection profiles indicate that the Ngrayong formation is one of the candidates for CO2 injection. We observed the outcrop of the Ngrayong formation and measured hydrological and geophysical properties (e.g., permeability, seismic velocity) of the rock samples obtained from outcrop and wells. The Ngrayong formation has layered structure and heterogeneous characteristics. Using (1) hydrological properties, (2) subsurface structures (i e., geometry of the Ngrayong formation) and (3) physical properties predicted by integrating seismic and logging data via acoustic impedance inversion, we applied reservoir simulation and evaluated security of the CO2 injection sites. (C) 2014 The Authors. Published by Elsevier Ltd.

DOI： 10.1016/j.egypro.2014.11.666

記述言語：英語   掲載種別：研究論文（その他学術会議資料等）  

記述言語：その他  

© 2015 by the Canadian Institute of Mining, Metallurgy &amp; Petroleum and ISRM. Instead of carbon capture and geological storage (CCS) that does not rely on structural aquifers, injecting carbon dioxide into sedimentary rock deep underground has been considered. For advection velocity of the fluid is slow, the permeability of sedimentary rock deep underground is low. In order to perform the CCS on the low permeable sedimentary rock, it is necessary to clarify the behavior of long term storage properties of carbon dioxide (CO2). In this study, the permeability and storativity of CO2injected into low permeable rock has been evaluated. The injection of supercritical CO2has been conducted on the specimen of Ainoura sandstone (unit weight: 2.39 g/cm3, porosity: 11.9 &#37;) saturated with water by using flow pump method. The experiment has been set up to reproduce te similar condition of deep underground reservoir under 20 MPa confining pressure, 10 MPa pore pressure, 35°C temperature and 3 μl/min CO2injection rate. In order to prevent an increase in pore pressure, the boundary condition on the outlet side of specimen has been kept a constant pressure. As a result, it has been possible to observe step by step the change of the differential pressure between both ends of specimen. Furthermore, the relative permeability and specific storage of rock under supercritical CO2injection has been examined by the theoretical analysis of flow pump permeability test incorporating Darcy&#039;s law for two-phase flow. It is observed that CO2has been transmitted gradually while CO2stored in the rock. It is also clarified that residual water has existed in specimen after showing the constant differential pressure in the end of the experiment. Using the results of the experiment, 3D core-scale flow-simulation by using TOUGH2 has been conducted due to confirm the flow of fluid and CO2distribution in the specimen. From the experimental results and analytical solution to them, permeability and storativity are identified, and simulation results support the validity of the experimental results.

記述言語：英語   掲載種別：研究論文（その他学術会議資料等）  

Click here and insert your abstract text. Physical properties of reservoir and seallayer samples are essential information to evaluate the storage and seal potential and to predict long term CO2 behaviour in reservoir. In this study, we measure the elastic wave velocities (V-p and V-s), porosity and density of sandstone, limestone and limemudstone samples are measured of Ngrayong Fm. and Bulu Fm, Central Java, Indonesia. The sandstones indicate low V-p, V-s, density and high porosity. These results suggest that sandstones on Ngrayong Fm. have large porosity and became important candidate of CO2 reservoir. On the other hand, limemudstone indicates high velocities with low porosity and point out that they have enough potential to be sealing layer of injected CO2. (C) 2014 The Authors. Published by Elsevier Ltd.

DOI： 10.1016/j.egypro.2014.11.525

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Two-phase fluid flow is strongly controlled by small-scale (subcore-scale) heterogeneity of porous sandstone. We monitor the heterogeneous/anisotropic two-phase flow (CO2 and water) in porous sandstone and conduct multichannel V-P and V-P anisotropy measurements under super critical CO2 conditions during CO2 injection (drainage) and water reinjection (imbibition) processes. In drainage, V-P shows large reduction (similar to 10&#37;) in all sections of the core sample and changes from the bottom inlet side to upper outlet side. It is considered that V-P reduction reflects the CO2 movement in the specimen. The V-P anisotropy of the upper two planes indicates clear increase. The results of this experiment indicate the heterogeneous CO2 flow around laminae in porous sandstone and characteristic behavior of these laminae as a barrier for CO2. On the other hand, flow of water is not affected by this barrier. This characteristic CO2 water flow around laminae is observed in the numerical simulation results. This simulation study also indicates that the capillary number is not directly affected on two-phase fluid flow around small-scale heterogeneity in porous sandstone. These results suggest that the small-scale heterogeneity behaves as a CO2 gate and strongly controls CO2 behavior in porous sandstone.
Key Points <list list-type="bulleted" id="jgrb50869-list-0001"><list-item id="jgrb50869-li-0001">The gate effect of small-scale heterogeneity on CO2 flow in porous sandstone<list-item id="jgrb50869-li-0002">Monitoring of anisotropic CO2 flow around lamina by V-P and V-P anisotropy<list-item id="jgrb50869-li-0003">Water and CO2 flow simulation by LBM in heterogeneous sandstone

DOI： 10.1002/2014JB011281

記述言語：英語   掲載種別：研究論文（その他学術会議資料等）  

It is important to produce Carbon-Free Hydrogen for FCV. Current Japanese situation, it is difficult to fully supply the Carbon Free Hydrogen is generated by water-electrolysis (WER) using renewable energy. This study presents the Steam reforming for natural gas (NSR) with decentralized CCS system for producing Carbon-Free Hydrogen. The CCS cost is covered by the differential cost between WER and NSR Hydrogen production cost. Our preliminary investigation suggests the differential cost between WER and NSR Hydrogen enough to cover the cost of decentralized CCS (under 1000 ton-CO2/y). We also analyze the feasibility of Mother-Daughter type of Hydrogen supplement system with decentralized CCS. In this case, NSR with CCS system has advantage against WER Hydrogen production systems. These investigations clearly indicate the high potential of NSR with CCS system but it is carefully discussion about CO2 behavior in the reservoir by well-established and newly developing methods for safety. (C) 2014 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/).

DOI： 10.1016/j.egypro.2014.11.490

記述言語：英語   掲載種別：研究論文（学術雑誌）  

In this study, we conduct a simultaneous measurement of V-p and V-s of porous sandstone during drainage and imbibition to monitor the change of CO2 saturation (S-CO2) in porous sandstone under in situ pressure and temperature conditions. We estimate the S-CO2, from the change in V-s. The relationship between measured V-p and S-CO2 indicates two interesting results. First, we can find that V-p does not recover to pre-drainage levels after the end of the imbibition process. This unrecovered V-p is considered to be the effect of residual trapped C-O2. Second, there is a hysteresis between drainage and imbibition. Finally, we investigate the V-p-V-s, relation and find clear differences between water-saturation and irreducible water-saturation. From the V-p-V-s, relation, we also identify the un-recovered V-p-changes between drainage and imbibition. These results indicate the high-potential of monitoring the change of S-CO2 from V-p and V-s. (C) 2014 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.ijggc.2014.03.013

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.egypro.2014.11.525

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.egypro.2014.11.666

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.egypro.2014.11.490

記述言語：英語   掲載種別：研究論文（その他学術会議資料等）  

To understand the structural and residual CO2 trapping mechanism, we conducted laboratory experiments and 2-D fluid flow simulations. The results of elastic wave velocity measurements indicate that there are strong effects of injected CO2 volume on elastic wave velocities. We calculated CO2 saturation from changes of Vs and estimated the irreducible water saturation and residual CO2 saturation. We also discovered the strong effect of small-scale heterogeneity of pore structure on fluid behavior by 2-D fluid flow simulation. The simulation results indicated that the laminae restricted fluid flow and stored CO2 as the residual trapped CO2. These results indicate that the small-scale heterogeneity is important to forming residual trapped CO2. (C) 2013 The Authors. Published by Elsevier Ltd.

DOI： 10.1016/j.egypro.2013.06.310

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.egypro.2013.06.310

記述言語：日本語  

To better understand trapping mechanisms of CO₂ in reservoir, we try to elucidate the effect of thin and low-porosity lamina in porous Tako sandstone on CO₂ flow by experiments and numerical simulations. Tako sandstone is characterized by the well-developed and low porosity lamina, where the intergranular space is filled with precipitated iron-rich minerals. We measure P-wave velocities (Vp) in three channels which are crossing through high porosity zone (Ch.A), on a lamina (Ch.B), and beneath the lamina (Ch.C) during CO₂ injection stage (drainage) and water re-injection stage (imbibition). In drainage, all channels show large Vp-reduction over 10 &#37;. In imbibition, they indicate Vp-increases but different recovery patterns with injecting CO₂-saturated water. After 250 ml water injection, Vp of Ch.A and Ch.B almost recover from Vp-reduction in drainage. On the other hand, Vp of Ch.C still has a reduction about 4&#37;. We then try 2D core-scale flow-simulations by using TOUGH-2 to confirm the effect of lamina on fluid flow and pattern of CO₂ distribution. In drainage, CO₂ has large mobility and moves upward vigorously to the top-end of core at 20ml CO₂-injection. After reaching the top-end, CO₂ invades lamina zone and raises CO₂-saturation during drainage. In enhanced case of difference between porosity-permeability relation, the result of simulation indicates the strong heterogeneity of CO₂-distribution pattern, which shows clear low-CO₂ saturation of the lamina zone and obvious high-CO₂ saturation of the zone of direct beneath of lamina. In imbibition, CO₂ saturation decreases rapidly after 40ml water injection. However, the zone of beneath the lamina keeps high CO₂ saturation after 100ml water injection. These results suggest that the lamina in Tako sandstone behave as barriers of CO₂ flow. This assumption is supported by results of Vp-measurement, because the channel of beneath a lamina still shows a Vp-reduction about 4&#37; after 250 ml water injection.

DOI： 10.2473/journalofmmij.128.511

記述言語：日本語  

&emsp;Relative permeability curves of water and supercritical CO₂ (scCO₂) were obtained for two porous sandstones under steady-state flow conditions. The present measurements provide accurate relative permeability values for water and scCO₂, which is important to better understand the behavior of CO₂ injected into the deep saline aquifer when carrying out carbon dioxide capture and storage (CCS). &emsp;We have developed a new method for measuring the volume of scCO₂ and water under the same pressure and temperature conditions as in the porous rock employing a high-pressure water-CO₂ separator. Water saturation in the sandstone was determined with a mass balance analysis measuring changes of the surface boundary between water and scCO₂. We measured Berea sandstone and Tako sandstone, which were cored and shaped into a cylinder form. The mixed fluid of water and scCO₂ was injected into a rock sample that was previously saturated with CO₂-saturated water. The flow volumes of the water and scCO₂ were measured for different saturation conditions by changing the mixing ratio of the fluids at the sample inlet. All measurements were made at 40&deg;C and 10 MPa, including those for the water-CO₂ separator. The injection flow rate was 0.5 ml/min. By plotting the ratios of water and scCO₂ of the inflow and outflow with respect to elapsed time, we can determine whether the flow is steady or unsteady. &emsp;The relative permeability curve is obtained by plotting the relative permeability values with respect to the degree of water saturation. The results for Berea sandstone suggest that the relationship between relative permeability and the relative saturation of water and scCO₂ correspond well to those of the previous study. However, the results for Tako sandstone deviate from the predicted curve of the previous study. This is likely to be due to the heterogeneity of Tako sandstone.

DOI： 10.5026/jgeography.120.944

記述言語：英語   掲載種別：研究論文（学術雑誌）  

P>Changes in V-p/V-s (Poisson's ratio) around a fault are related to changes in the fluid transport properties of rocks, which play a significant role in seismogenic processes. Here we report a notable relationship between V-p/V-s and the permeability of porous fault-related rocks (Chelungpu fault, Taiwan) by direct and simultaneous measurement of elastic wave velocities (V-p and V-s) and permeability under increasing effective confining pressure (P-eff) up to 25 MPa. V-p and V-s for all samples increased with P-eff in the range up to 20 MPa, then were nearly constant as P-eff increased to 25 MPa. Most silty sandstones with large proportions of fine-grained material showed positive correlations between V-p/V-s and permeability with rising pressure. On the other hand, well-sorted sandstones showed only slight changes in permeability with respect to V-p/V-s with rising pressure. We infer that grain size distributions, in particular the amount of silt- and clay-size grains, are responsible for the change in permeability with pressure as small particles clog pore networks with increasing P-eff, causing the decrease in permeability. These findings may be useful to explain changes in permeability and pore pressure in the deep crust.

DOI： 10.1111/j.1365-246X.2010.04694.x

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1111/j.1365-246X.2010.04694.x

記述言語：その他  

Sequestration of Carbon Dioxide (CO2) into saline aquifers has been proposed as one of the most practical options of all geological sequestration possibilities. When saline aquifers are to be used to sequester CO2 for long periods, it will be necessary to monitor the migration and diffusion of CO2 in those reservoirs. Monitoring of geological sequestration has been identified as one of the highest priority needs in several recent international conferences on greenhouse gas control technologies. Monitoring is necessary to confirm the containment of CO2, to assess leakage paths, and to gain understanding of interactions between CO 2, the rock-forming minerals, and formation fluids. Recently CO 2 monitoring has moved to next stage for the purpose of leakage detection and quantification of CO2 stored in reservoirs. What kinds of monitoring methods we could use and do the methods have sufficient resolution and detection levels need to be addressed urgently. Seismic surveys provide the most attractive approach for obtaining the spatial coverage required for mapping the location and movement of CO2 in the subsurface. However, from the first Japanese pilot project, time-lapse sonic logging results showed P-wave velocity becomes less sensitive when the CO2 saturation up to 20&#37;, while resistivity kept increasing with increase in CO2 saturation. This paper describes the results of P-wave velocity and resistivity measurements when injecting CO2 into water-saturated porous sandstones at laboratory and the results of comparison between P-wave velocity and resistivity changes obtained from both laboratory- and field-scales. Copyright 2009, Society of Petroleum Engineers.

記述言語：日本語   掲載種別：研究論文（国際会議プロシーディングス）  

記述言語：英語   掲載種別：研究論文（その他学術会議資料等）  

記述言語：英語   掲載種別：研究論文（その他学術会議資料等）  

In this paper, we present the results of geophysical and geochemical observations at the Nagaoka site, where the first Japanese project on CO2 geological storage is currently underway. We collected formation water and rock samples from the reservoir, and conducted laboratory experiments to investigate the seismic wave response and geochemical reactions due to the CO2 injection under simulated in situ conditions. The results of time-lapse crosswell seismic tomography indicate an area of P-wave velocity decrease due to CO2 saturation, and the CO2-bearing zone near the injection well expanded clearly along the formation up dip direction during CO2 injection. The presence of CO2 was also identified by induction, sonic and neutron logging at the observation wells. The results of geochemical reactions demonstrated the potential of reservoir sandstones at the Nagaoka site for the effective solubility, ionic, and mineral trapping of CO2. (C) 2009 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.egypro.2009.01.268

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1029/2006JB004678

記述言語：英語   掲載種別：研究論文（学術雑誌）  

We examined two effects of the presence of clay in brittle deformations: the reduction in frictional strength and the impediment of across-fault fluid flow. Permeability was monitored during the sliding deformation of a gouge of various mixes of Na-montmorillonite powder and granular quartz along a 30° precut surface of Berea sandstone under 80 MPa of normal stress, 5 MPa of pore water pressure, and room temperature. The decrease in the friction coefficient of a gouge with increasing clay content was not simple, but showed a sharp drop at 50 vol.&#37; clay content. The reduction in permeability due to deformation increased with increasing clay content from 0 to 24 vol.&#37;, and a dramatic reduction of ∼2.5 orders of magnitude occurred at 18 and 24 vol.&#37; clay content. However, in a gouge with more than 29 vol.&#37; clay content, deformation reduced the permeability by only 0.5 orders of magnitude. Thus the transitional clay contents at which the clay dominated the properties of fault strength and fluid transport were 50 and 29 vol.&#37;, respectively. These values almost agree well with values obtained using a model with an equal-sized clast (quartz) framework. The clay matrix can completely fill the pores sustained by a closest-packed quartz framework when the clay content reaches 29 vol.&#37;, whereas the content required to fill the pores of a framework that can barely sustain quartz-quartz contact is 50 vol.&#37;. Copyright 2007 by the American Geophysical Union.

DOI： 10.1029/2006JB004678

記述言語：英語   掲載種別：研究論文（学術雑誌）  

From the friction experiments of the Atotsugawa fault gouge using a tri-axial apparatus under several pressure-temperature conditions at depths down to 9 km, we found an increase in the coefficient of friction from 0.50 to 0.58 as depth increases from 1 km to 9 km. Based on this result, we proposed a fault slip model which explains the creeping motion of the Atotsugawa fault. In this model, stress on the fault attains to the low frictional strength in the shallow part earlier than that in the deep so that this difference results in a creeping slip in the shallow depth during inter-seismic period. The model could successfully describe the presence of a creeping section along the Atotsugawa fault at shallow depth with its creeping rate similar to the field observation on the fault. (c) 2007 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.pepi.2007.01.003

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.pepi.2007.01.003

記述言語：英語   掲載種別：研究論文（学術雑誌）  

In order to study the effects of different pore fluids on elastic-wave velocities, we developed a new system for measuring elastic wave velocities (V-p and V-s) under high-pressure conditions up to 200 MPa and high-temperature conditions up to 200 degrees C using a gas-medium high-pressure and high-temperature apparatus. During the V-p and V-s measurements, we can also control the pore pressures from outside the rock samples. We measured V-p and V-s of the Berea sandstone samples under three different pore-fluid conditions including dry (without pore-fluids), in the presence of pore water, and in the presence of pore gas. Here we describe our new measurement technique and establish the capacity of the gas apparatus and measurement technique and their potentialities for the solution of geological problems.

DOI： 10.1186/BF03352651

記述言語：英語   掲載種別：研究論文（学術雑誌）  

The Vp anisotropies of two amphibole-rich rocks and two biotite-amphibole-rich rocks were measured under high-pressure conditions (up to 1.0 GPa), and calculated based on the physical properties and lattice-preferred orientation (LPO) of amphibole and biotite. The results of these studies clearly demonstrated the strong effects of the LPO of amphibole and biotite on Vp anisotropies. Previous studies pointed out the importance of [001] of amphibole and (001) of biotite for Vp anisotropy. In addition to these axes and poles, (100) of amphibole strongly affected the Vp anisotropy of the sample rocks.

DOI： 10.1111/j.1365-246X.2006.02961.x

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1111/j.1365-246X.2006.02961.x

記述言語：日本語  

We review the methods of measuring the velocities of elastic-waves in rocks and summarize the temperature-dependence of elastic-wave velocities under high-temperature and high-pressure conditions. The elastic-wave velocities in rocks are strongly affected by several phenomena such as thermal cracking, phase transition of minerals, partial melting of rocks, and dehydration of hydrous minerals. These phenomena are strongly affected by pressure-temperature conditions and chemical compositions of rocks and minerals. Thus, it is very difficult to predict the elastic wave velocities of rocks and minerals under high-pressure and high-temperature conditions theoretically. Laboratory measurements of the velocities of elastic-waves in rocks under high-pressure and high-temperature conditions have provided useful data for estimating physical and geological properties in the crust and upper mantle. We also mention the next issues to be studied in relation to the velocity of elastic waves in rocks. It is important to measure elastic-wave velocities in rocks under high-temperature and high-pressure conditions in the presence of pore-fluids.

DOI： 10.5026/jgeography.114.6_963

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/S0040-1951(03)00229-4

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Ultrasonic compressional wave velocities (Vp) and shear wave velocities (Vs) were measured with varying pressure up to 1.0 GPa in a temperature range from 25 to 400 degreesC for a suite of tonalitic-gabbroic rocks of the Miocene Tanzawa plutonic complex, central Japan, which has been interpreted as uplifted and exposed deep crust of the northern Izu-Bonin-Mariana (IBM) arc. The Vp values of the tonalitic-gabbroic rocks increase rapidly at low pressures from 0.1 to 0.4 GPa, and then become nearly constant at higher pressures above 0.4 GPa. The Vp values at 1.0 GPa and 25 degreesC are 6.3-6.6 km/s for tonalites (56.4-71.1 wt.&#37; SiO2), 6.8 km/s for a quartz gabbro (53.8 wt.&#37; SiO2), and 7.1-7.3 km/s for a hornblende gabbro (43.2-47.7 Wt-&#37; SiO2). Combining the present data with the P wave velocity profile of the northern IBM arc, we infer that 6-km-thick tonalitic crust exists at mid-crustal depth (6.1-6.3 km/s Vp) overlying 2-km-thick hornblende gabbroic crust (6.8 km/s Vp). Our model shows large differences in acoustic impedance between the tonalite and hornblende gabbro layers, being consistent with the strong reflector observed at 12-km-depth in the IBM arc. The measured Vp of Tanzawa hornblende-bearing gabbroic, rocks (7.1-7.3 km/s) is significantly lower than that Vp modeled for the lowermost crustal layer of the northern IBM arc (7.3-7.7 km/s at 15-22 km depth). We propose that the IBM arc consists of a thick tonalitic middle crust and a mafic lower crust. (C) 2003 Elsevier B.V. All rights reserved.

DOI： 10.1016/S0040-1951(03)00229-4

記述言語：その他  

Laboratory measurements of P-wave velocity of granulites from Lutzow-holm Complex, East Antarctica: Preliminary report

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

記述言語：その他   掲載種別：研究論文（学術雑誌）