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About the Journal

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Journal:
Coal Geology & Exploration
Establishment year:
1973
 
Periodicity:
Biomonthly
Supervised by:
Xi’an Research Institute Co. Ltd., China Coal Technology and Engineering Group Corp.
Sponsored by：
Xi’an Research Institute Co. Ltd., China Coal Technology and Engineering Group Corp.
Editor-in-chief:
 DONG Shuning
 
Associate E ditor-in-chief:

 LIU Cheng, James W. LaMoreaux 

 

Executive Editor-in-chief:
JIN Xianglan 

 

ISSN:
1001-1986
CN:
61-1155/P
Web:
www.mdkt.cbpt.cnki.net

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Article list

  • Research progress and prospects of full flowsheet coal-based CCUS

    SANG Shuxun;LIU Shiqi;ZHENG Sijian;HUANG Fansheng;LIU Tong;CHEN Siming;ZHOU Xiaozhi;HAN Sijie;TIAN Yuchen;XIANG Wenxin;BAI Yansong;School of Resources and Geosciences, China University of Mining and Technology;Key Laboratory of Coalbed Methane Resources & Reservoir Formation Process, Ministry of Education, China University of Mining and Technology;Jiangsu Key Laboratory of Coal-based Greenhouse Gas Control and Utilization, China University of Mining and Technology;Carbon Neutrality Institute, Ch

    [Background] The engineering-oriented, full flowsheet coal-based carbon capture, utilization, and storage(CCUS) technology is the key to efficient, clean coal utilization and carbon emission reduction. It represents a major technology that is urgently needed to ensure the energy security of China and achieve the strategic goals of peak carbon dioxide emissions and carbon neutrality of the country. Based on previous research efforts of the authors' team, this study reviews the current status of this technology, reveals its integration mechanisms, and attempts to establish a pattern and scheme for CCUS cluster deployment in coal energy bases. Furthermore, it discusses the future development directions and technical challenges of the full flowsheet coal-based CCUS technology. [Advances] The key links of engineering-oriented, full flowsheet coal-based CCUS technology include energy-saving, highly adaptable coal-based CO_2 capture, safe and efficient geologic CO_2 sequestration in coal seams, and full and cost-effective CO_2 utilization in coal mining areas. The integration of this technology is achieved by the coupled control of three mechanisms: source-sink matching, technical parameter matching, and system optimization. Specifically, the source-sink matching mechanism enables the physical connection of coal-based CCUS facilities through multidimensional, multi-constraint pathway optimization. The technical parameter matching mechanism, using end-to-end coordinated design of critical operational parameters for carbon capture, storage, and utilization, achieves both the stable overall operation of physically connected facilities and the establishment of technical chain parameters. The system optimization mechanism allows for the dynamic optimization of the technical chain and the construction of optimal system configurations using big data platforms, optimization models, and intelligent algorithms. The three mechanisms exhibit strong interdependencies and mutual feedback. The technical pattern of the full flowsheet coal-based CCUS technology possesses distinct characteristics, including CO_2 capture from coal-fired or coal chemical industrial sources, geologic CO_2 sequestration in coal-bearing basins or coal seams, and CO_2 utilization in coal mining areas. This technology is implemented as CCUS clusters in coal energy bases. The CCUS clusters in large-scale coal bases, exemplified by the Junggar and Ordos basins, are expected to provide critical technical support for the low-carbon, high-quality development of China's coal industry. [Prospects] The deployment of CCUS clusters in large coal bases represents the mainstream development direction of the full flowsheet coal-based CCUS technology, with the connotation comprising:(1) low-cost CO_2 capture;(2) safe and efficient geologic CO_2 sequestration in deep, depleted coalbed methane(CBM) or coal-measure gas reservoirs within coal-bearing basins,and(3) high-value, integrated utilization of CO_2 in coal mining areas. Additionally, major directions for the technology expansion include:(1) enhanced CBM recovery(ECBM) driven by tail gas from the coal chemical industry and CO_2 sequestration;(2) ECBM by injecting flue gas from oxygen-enriched combustion(flue-gas ECBM) and CO_2 sequestration,(3) efficient CO_2 capture and large-scale CO_2 conversion and utilization for peak shaving via coal-fired power generation in new energy bases; and(4) CO_2 capture from coal-fired power generation bases coupled with carbon and energy storage in abandoned mine goafs.

    2026 01 v.54;No.337 [Abstract][OnlineView][Download 2184K]

  • Carbon sequestration technology: Challenges and urgent critical scientific issues

    LI Xiaochun;LIU Tianyu;ZHANG Liwei;ZHOU Hong;LIU Guizhen;WANG Yan;GAN Manguang;LI Qi;State Key Laboratory of Geomechanics and Geotechnical Engineering Safety, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences;University of Chinese Academy of Sciences;National Science Library(Wuhan), Chinese Academy of Science;

    [Objective] Carbon sequestration technology represents a core approach to achieving carbon neutrality.However, its large-scale application remains constrained by multiple technical and scientific challenges. [Methods]Based on an analysis of existing carbon sequestration projects, this study identified four major challenges in carbon sequestration:(1) high uncertainty in the assessment of CO_2 sequestration capacity;(2) low injectivity of low-permeability discontinuous reservoirs;(3) a limited understanding of long-term mechanical stability; and(4) significant difficulty in assessing the risks of CO_2 leakage. [Results] To address these challenges, this study proposes the common issues currently faced by carbon sequestration technology, and, accordingly, determines three urgent critical scientific issues. First,there is an urgent need to develop universal geological theories applicable to carbon sequestration projects and, accordingly, to improve systems for evaluating effective sequestration capacity based on reservoir injectivity, tightness, and stability. Second, disturbance patterns in carbon sequestration projects should be investigated, and multi-field, multi-phase,and multi-scale constitutive relationships should be established, with the purpose of enhancing prediction accuracy.Third, it is necessary to advance the risk assessment, monitoring, and remediation theories applicable to carbon sequestration projects, as well as to integrate multi-physical-field coupling simulation with low-cost, high-sensitivity monitoring technologies. These efforts are essential for establishing closed-loop risk management systems. [Conclusions] In the future, it is advisable to address these three critical scientific issues through theoretical innovation, technological development, and interdisciplinary collaboration. These efforts will help optimize the evaluation of CO_2 sequestration capacity, improve CO_2 sequestration efficiency in reservoirs within basins, ensure the long-term stability of sequestration sites, and mitigate leakage risks. These advances will provide robust support for the large-scale applications of carbon sequestration and the achievement of global carbon neutrality.

    2026 01 v.54;No.337 [Abstract][OnlineView][Download 1761K]

  • Multi-scale source-sink matching and transportation route optimization for geologic CO2 sequestration of industrial CO2 stationary sources in Jiangsu Province

    TIAN Yuchen;LIU Shiqi;ZHANG Helong;MO Hang;WANG Dexi;SANG Shuxun;WANG Jun;WANG Wenkai;ZHENG Sijian;School of Resources and Geosciences, China University of Mining and Technology;Key Laboratory of Coalbed Methane Resources & Reservoir Formation Process, Ministry of Education, China University of Mining and Technology;China Nonferrous Metals (Guilin) Geology and Mining Co., Ltd.;East China Oil &Gas Company,SINOPEC;Jiangsu Key Laboratory of Coal-based Greenhouse Gas Control and Utilization,China Un

    [Objective] CO_2 stationary sources tend to show a dispersed distribution, while carbon sinks are concentrated in specific sedimentary basins. The resulting significant source-sink mismatch in space restricts the large-scale applications of carbon capture, utilization, and storage(CCUS) technology. Therefore, reducing CCUS costs by investigating source-sink matching and optimizing CO_2 transportation routes under a multi-scale spatial framework is the key to the engineering applications of CCUS. [Methods] Targeting representative industrial CO_2 stationary sources and carbon sinks in Jiangsu Province, this study established source-sink matching models on multiple scales covering hydrocarbon reservoirs, sags, and basins. Based on both the geographic information system(GIS)-based least-cost path planning method and an improved pipeline network optimization strategy, this study explored regional multi-scale source-sink matching. [Results and Conclusions] By the end of 2023, a total of 269 representative industrial CO_2 stationary sources were identified in Jiangsu Province, with total annual CO_2 emissions reaching 6.26×10~8 t. Among these sources, different types exhibited different CO_2 emission scales and spatial distributions, with the thermal power sector yielding the highest proportion of CO_2 emissions. In Jiangsu Province, thermal power plants and steel mills are primarily distributed in the southern part of the Yangtze River Delta and cities along the Yangtze River. In contrast, cement plants are concentrated in the southern part of the province, while synthetic ammonia plants show a scattered distribution. Within the study area, deep saline aquifers and oil reservoirs in sags, such as B10, B11, and B6, exhibited great potential for geologic CO_2 sequestration, with the sequestration capacities estimated at about 58.7×10~8 t and 7.28×10~8 t, respectively. In combination with the regional demands for carbon emission reduction and the source-sink spatial distribution, this study developed source-sink matching models on multiple scales covering hydrocarbon reservoirs, sags, and basins. The calculation results of these models indicate that the theoretical pipeline lengths on the scales of hydrocarbon reservoirs, sags,and basins were determined at 238.9 km, 398 km, 3 873 km(the Subei Basin), and 4 100 km(the Subei-southern Yellow Sea Basin), respectively. After being optimized by integrating the GIS and the saving algorithm-based strategy, the pipeline lengths on the scales of hydrocarbon reservoirs, sags, and basins were calculated at 243.7 km, 426 km, 1 831 km(the Subei Basin), and 2 121 km(the Subei-southern Yellow Sea Basin), respectively. Such effort contributed to the formation of optimized CO_2 transportation routes matched better with the geographical setting and actual engineering implementation requirements while effectively reducing the construction costs of pipeline networks. The results of this study will provide a theoretical basis and methodological support for building low-cost, highly adaptable CCUS transportation routes in the eastern coastal areas of China.

    2026 01 v.54;No.337 [Abstract][OnlineView][Download 2670K]

  • Research and application of a decision support platform for geologic CO2 storage siting based on a global case database

    ZHOU Yinbang;WANG Rui;ZHEN Yan;DAI Quanqi;CHENG Chuanjie;Petroleum Exploration and Production Research Institute,SINOPEC;School of Geoscience and Technology,Southwest Petroleum University;

    [Objective] Under the strategic background of reaching the goals of peak CO_2 emissions and carbon neutrality, there is an urgent need to address the core issue of geologic CO_2 storage(GCS) siting in the advancement of largescale GCS deployment. Establishing a decision support platform based on a global GCS case database can provide key data and historical experience references for GCS siting, reduce storage risks and costs, and accelerate industrial layout.Furthermore, the platform can offer a scientific basis for formulating related policies and conducting technological R&D.[Methods] This study proposed and developed a comprehensive evaluation system for GCS siting. This system integrates three core techniques: a case analogy algorithm based on improved cosine similarity, a suitability assessment model relying on fuzzy comprehensive evaluation, and a method for selecting favorable geobodies by combining 3D geological models. By constructing a quantitative case database and linking multi-source parameters, this study established a unified spatial database model. Using the ArcGIS platform, it developed a range of functional modules integrating the comparison and selection of similar cases, the suitability assessment of storage sites, and the selection of favorable geobodies. Consequently, a systematic technical support system for GCS siting was formed. [Results and Conclusions] Using the resulting framework, this study developed a decision support platform for quantitative selection of optimal GCS targets, which integrated an improved cosine similarity algorithm, a suitability assessment model based on a random forest algorithm, and 3D geological modeling. Through algorithm-driven systematic scanning of the entire data volume,this platform significantly enhances the case matching accuracy from qualitative to quantitative and improves the objectivity of geobody evaluation, effectively reducing the subjective bias and limited vision inherent in traditional manual methods. This platform enables a unified quantitative evaluation and hierarchical ranking of various trap types such as anticlines and fault blocks, substantially improving both the efficiency of GCS target identification and the comparability of results. The practical application in the Gaoyou Sag within the Subei Basin demonstrates that this platform can provide precise, efficient digital solutions that provide direct support for GCS siting, thereby significantly enhancing the scientific rigor and prospective planning for large-scale CO_2 storage deployment.

    2026 01 v.54;No.337 [Abstract][OnlineView][Download 2071K]

  • Designation and classification of CO2 storage technologies

    MA Fubo;YANG Xuechao;ZHOU Zhengwu;LIU Hongliang;CHANG Jia;YI Jiayao;WANG Yan;New Energy Technology Research Institute Co., Ltd., China Energy Investment Corporation Co., Ltd.;Yulin Chemical Co., Ltd., China Energy Investment Corporation Co., Ltd.;North China Electric Power University;

    [Objective and Method] Currently, there remains a lack of criteria for technical certification, designation,and classification of carbon dioxide(CO_2) storage technologies due to their cross-disciplinary nature and ambiguous scopes. To address this issue, this study proposes technical certification criteria and designation principles, as well as analyzes four types of common CO_2 storage technologies: geologic storage, underground space storage, ocean water storage, and utilization and storage. Accordingly, a classification philosophy and scheme for these technologies is determined. [Results and Conclusions] In terms for technical certification criteria, a CO_2 storage technology has to meet four criteria:(1) it must enable effective, long-term to permanent separation of CO_2 from the atmosphere;(2) it must be anthropogenic activity aimed at reducing atmospheric CO_2 beyond statutory requirements;(3) it should do no significant harm to the environment. Regarding the designation in Chinese and English(including English abbreviations) for CO_2 storage technologies, the following principles should be followed:(1) well-known technology names should be used without modification, while technologies similar to those widely recognized should be designated following the designation principles of the latter. For emerging technologies, the most frequently used Chinese and English names, as identified using academic search engines, shall be used. For English terms, "sequestration" and "storage" differ slightly in the field of carbon removal. Specifically, "sequestration" emphasizes scientific mechanisms, while "storage" highlights a broader scale or is more engineering-oriented. A generally hierarchical classification philosophy is proposed in this study. First, based on their differences in storage environments, CO_2 storage technologies can be divided into terrestrial and marine categories. Second, several types can be determined based on CO_2 storage space and mechanism. Third, further classification is performed by storage depth and scale. Fourth, the minimum types can be determined by further classification by storage proportion and time. Using this classification philosophy, a classification scheme for CO_2 storage technologies is determined, consisting of two levels and seven indicators. The first level comprises storage environment,storage space, and storage mechanism, which are three qualitative indicators. The second level is composed of sub-class,model, grade, and pattern, corresponding to four quantitative indicators, i.e., storage depth, storage scale, storage proportion, and storage time, respectively.

    2026 01 v.54;No.337 [Abstract][OnlineView][Download 1498K]

  • Reaction mechanisms during CO2 absorption in ethanolamine solutions

    TENG Weiwei;WU Yan;FAN Yuxin;LIAO Tao;WANG Zicheng;YU Hui;LI Meng;XU Xiaoling;Xinjiang Oilfield Company;Oil Production Technology Research Institute of Xinjiang Oilfield Company;School of Engineering, China University of Petroleum-Beijing at Karamay;

    [Objective] Presently, CO_2 capture technology based on the ethanolamine solutions suffers from drawbacks such as high energy consumption and elevated costs. A primary method to address these challenges is to construct blended amine solutions by synergistically integrating the absorption and desorption advantages of different types of ethanolamines. Hydroxyethyl ethylenediamine(AEEA) and N-methyldiethanolamine(MDEA) represent two major commonly used absorbents, and their blending necessitates an accurate understanding of their CO_2 absorption patterns, including CO_2 loading capacity, the ion-concentration distribution patterns of reaction products, and reaction orders. Currently,their absorption mechanisms remain poorly understood, and there is a lack of relevant reaction parameters, jointly undermining the prediction accuracy of process models. [Methods] By investigating the CO_2 absorption processes of AEEA and MDEA solutions, this study clarified the reaction mechanisms of both solutions. Furthermore, it established ion concentration distribution models of the reaction products based on pH values, determined the reaction orders through regression analysis, and developed the reaction rate models of both solutions. [Results and Conclusions] The results indicate that, under the same concentration, the AEEA solution exhibited higher CO_2 absorption capacity and rates compared to the MDEA solution. The AEEA solution presented a two-stage CO_2 absorption process, with reaction orders approaching 2. Initially, the CO_2 absorption process in the AEEA solution was controlled by the formation of zwitterionic intermediates(R_1R_2NH~+COO~-) from AEEA-CO_2 reactions. In the late stage, this process was jointly governed by mass transfer and reactions. In contrast, the CO_2 absorption in the MDEA solution was identified as a base-catalyzed hydration process, with the reaction rate showing a linear correlation with the MDEA concentration and the reaction order determined at 1. The novel insights and models of this study provide theoretical guidance for the optimization of the concentration, retention time, and circulation rate of solvents, along with column design, in carbon capture technique.

    2026 01 v.54;No.337 [Abstract][OnlineView][Download 1630K]

  • Concept of CCCUS technology for CO2 recycling in deep unmineable coal seams

    LIANG Weiguo;YAN Jiwei;ZHU Dijie;GUO Hongguang;GONG Li;NIU Dong;Key Laboratory of In-situ Property-improving for Mining of Ministry of Education, Taiyuan University of Technology;College of Mining Engineering, Taiyuan University of Technology;Taiyuan University of Science and Technology;College of Safety and Emergency Management and Engineering, Taiyuan University of Technology;

    [Background] China possesses substantial resources of deep unmineable coal seams, which hold considerable potential for CO_2 sequestration. However, simply sequestrating CO_2 in deep coal seams incurs high economic costs while also wasting deep coal resources. The microbial conversion of sequestrated CO_2 into methane(CH_4) enables circular carbon capture, utilization, and storage(CCCUS), which is of great significance for the sustainable development of both resources and the environment. [Methods] Using a range of methods, including experimental study, theoretical analysis, and engineering simulations, CCCUS in deep unmineable coal seams is designed to(1) reveal the mechanisms behind efficient CO_2 fracturing and associated permeability enhancement, as well as CO_2 displacing CH_4, in deep unminable coal seams;(2) to investigate the mechanisms controlling the generation of complex fracture networks and efficient CH_4 displacement in the coal mines;(3) to develop methods for efficient hydrogen production from liquefied straw in deep coal seams under high-temperature and high-pressure conditions;(4) to propose a technical route for bioconversion of CO_2 in deep coal seams into CH_4 using liquefied straw; and(5) finally to evaluate the economic viability of CO_2 recycling. [Results and Conclusions] CO_2 fracturing in deep coal seams can create more complex fracture networks, increase the connectivity of micro-and nano-scale pores and fractures, and enhance CH_4 displacement efficiency. Meanwhile, microorganisms enable the efficient conversion of CO_2 into CH_4, thereby improving the conversion efficiency of CO_2 in deep coal seams. This study investigates the evolution patterns of pore and fracture structures in coal reservoirs under the combined effects of CO_2 fracturing, CO_2 displacing CH_4, and CO_2 to CH_4 bioconversion. It improves the theory on the coupling of coal body structure evolution and fluid migration under CCCUS in deep unmineable coal seams and explores the influence patterns of CCCUS on surrounding rock stability and geological environment, along with associated controlling mechanisms. Furthermore, this study enriches and develops theories on multi-field coupling in transport within porous media, achieves the technical reliability of CO_2 recycling, and quantitatively characterizes the economic indicators of CO_2 recycling. The results of this study provide an important theoretical basis for the implementation of innovative CCCUS technology in deep unmineable coal seams and offer robust support for China's energy revolution and the achievement of its goals of peak carbon dioxide emissions and carbon neutrality.

    2026 01 v.54;No.337 [Abstract][OnlineView][Download 1750K]

  • An improved model of trans-critical CH4 and CO2 adsorption in coals based on monolayer adsorption and adsorption potential theories

    SONG Xuemei;ZHANG Kun;SANG Shuxun;MA Mengya;LIU Huihu;XU Hongjie;State Key Laboratory of Digital Intelligent Technology for Unmanned Coal Mining, Anhui University of Science & Technology;School of Resources and Geosciences, China University of Mining and Technology;Joint National-Local Engineering Research Centre for Safe and Precise Coal Mining, Anhui University of Science & Technology;School of Earth and Environment, Anhui University of Science & Technology;

    [Objective and Method] Adsorbed phase density represents a key parameter for determining gas adsorption capacity in coals. Using bituminous coal samples from the Huainan and Huaibei mining areas in Anhui Province, this study carried out high-pressure isothermal adsorption experiments of CO_2 and CH_4 at temperatures of 24 ℃, 36 ℃, and48??℃. In combination with the quantitative characterization of pore structures in coals using low-temperature liquid nitrogen adsorption(LNA) experiments and mercury intrusion porosimetry(MIP), this study analyzed the high-pressure trans-critical CH_4 and CO_2 adsorption processes in coals. Meanwhile, based on the Gibbs excess adsorption, the adsorbed phase volumes and maximum adsorbed phase densities of CO_2 and CH_4 in coals were calculated using the intercept method. Furthermore, by integrating the Langmuir model based on the monolayer adsorption theory and the modified Dubinin-Astakhov(D-A) model based on the adsorption potential theory, this study established a model of highpressure trans-critical CH_4 and CO_2 adsorption in coals. [Results and Conclusions] Under the experimental conditions of 24 ℃-48 ℃ and 0-32 MPa, the excess adsorption capacities of CH_4 and CO_2 showed gradually declining trends after peaking due to an increase in the product of their free phase density(ρ_f) and adsorbed phase volumes(V_a) in the highpressure range. Specifically, the free phase density of CH_4 increased linearly with adsorption pressure, resulting in a linear decrease in the excess adsorption capacity in the high-pressure range. In contrast, the free phase density for CO_2 increased linearly in the low-pressure range(0-7 MPa) but exhibited an S-shaped trend in the high-pressure range(> 7 MPa), leading to more complex variations in the excess adsorption capacity. Given the linearly decreasing trend in the excess adsorption capacity of CH_4 in the high-pressure range, the adsorbed phase volume and maximum adsorbed phase density of CH_4 were calculated using the intercept method. Then, an expression of the adsorbed phase density was derived using the modified D-A model. As a result, a model of the absolute adsorption capacity of CH_4 under high pressures was established. By substituting the maximum adsorbed phase density of CO_2, used as a substitute for the hypothetical saturated vapor pressure, into the above model, an improved model was developed to fit the adsorbed phase density and absolute adsorption capacity of CO_2 in the high-pressure trans-critical adsorption processes. The improved model yielded coefficients of determination(R~2) greater than 0.98 for the fitting of the absolute adsorption capacities of CH_4 and CO_2. However, large deviations were observed during the fitting of CO_2 adsorption in the low-pressure range.To address this, the Langmuir model was introduced to describe the adsorption process in the low-pressure range. The resulting combined model further enhanced the fitting accuracy of the absolute adsorption capacities of CH_4 and CO_2 across the entire pressure range(R~2 > 0.99). The results of this study provide a theoretical basis and optimized method for exploring the high-pressure trans-critical adsorption processes of gases in coals and for assessing the CO_2 sequestration capacity in deep coal seams.

    2026 01 v.54;No.337 [Abstract][OnlineView][Download 1799K]

  • A method of carbon emission accounting and pathways of emission reduction through reduction through CCUS for underground coal mines

    XU Shen;WANG Meng;DAI Xuguang;QIU Yuxin;TUO Jialong;LI Wenhao;GAO Jie;Jiangsu Key Laboratory of Coal-based Greenhouse Gas Control and Utilization;Key Laboratory of Coalbed Methane Resources & Reservoir Formation Process,Ministry of Education;School of Resources and Geosciences,China University of Mining and Technology;

    [Objective] Coal production and utilization lead to substantial carbon emissions, and the carbon emissions from underground coal mines have attracted increasing attention. However, research on emission reduction pathways in coal mines remains nascent. [Methods] The Y Coal Mine was investigated in this study. Using methods including life cycle assessment(LCA), emission factor approach, and monitoring, this study identified the boundaries for carbon emission accounting and determined the sources, total amount, and characteristics of carbon emissions from the coal mine.Furthermore, a framework of carbon emission reduction through CCUS was established based on the principle of carbon capture, utilization, and storage(CCUS) technique and the technical means used in the critical links of the technique, as well as the specific carbon emission characteristics and geological conditions. [Results and Conclusions] The accounting boundaries cover the entire process from underground mining to coal washing and processing and then to coal transportation. Sources of carbon emissions can be categorized into direct and indirect types. Direct carbon emissions primarily comprise methane(CH_4) and carbon dioxide(CO_2) escaping from coal mining and post-mining operations, as well as greenhouse gases generated from fossil fuel combustion. Indirect emissions principally involve purchased electricity and consumed water resources. The carbon emission accounting results indicate that the annual carbon emissions from the Y Coal Mine totaled 7.43×10~5 t carbon dioxide equivalent(CO_2e) in 2024. Among these, gas escape led to the highest carbon emissions of 6.74×10~5 t CO_2e, accounting for approximately 90.8% of the total. In contrast, fuel combustion produced the lowest emissions, totaling 728.56 t CO_2e and representing a proportion of 0.2%. Indirect emissions accounted for approximately 9% of the total, primarily originating from the use of electricity(6.65×10~4 t CO_2e) and water resources(1.24×10~3 t CO_2e). The Y Coal Mine shows a carbon emissions structure dominated by gas escape. Therefore,carbon emission reduction should focus on gas drainage and utilization, along with the control of gas escape. The results of this study provide a quantitative method for developing a carbon emission accounting system for underground coal mines. This method, combined with the proposed pathways for emission reduction through CCUS, offers theoretical support and a practical reference for the green, low-carbon transition of the coal mining industry.

    2026 01 v.54;No.337 [Abstract][OnlineView][Download 1588K]

  • An experimental study on nonlinear seepage characteristics in coal seams during CH4 displacement through N2 and CO2 flooding

    LI Zefeng;HUANG Mengru;ZHANG Hongzhong;LAN Jianping;SONG Jinsuo;FAN Shixing;Changqing Downhole Technology Operating Company, Chuanqing Drilling Engineering Company Limited;National Engineering Laboratory for Exploration and Development of Low-Permeability Oil & Gas Field;College of Safety Science and Engineering, Xi'an University of Science and Technology;

    [Background] Coal seams in China are generally characterized by low porosity(<5%) and low permeability(0.001×10~(-3)μm~2), leading to low coalbed methane(CBM, dominated by CH_4) drainage efficiency. Gas flooding-enhanced CBM drainage technology plays a significant role in surface CBM drainage, underground CBM pre-drainage,and deep geologic CO_2 storage. [Methods] This study investigated four common types of gases: N_2 and CO_2 for flooding, CH_4 to be displaced, and He for blank control. Based on the physical properties of these gases and employing methods including the quasi-static method, the gas flow rate method, and the Reynolds number, this study explored the seepage behavior and characteristics of the four types of gases in coal cores measuring 100 mm, 200 mm, and 300 mm in length. Furthermore, it analyzed the impacts of the threshold pressure gradient, viscous resistance, and adsorption force on the seepage characteristics of He, N_2, CO_2, and CH_4. [Results and Conclusions] The results indicate that the resistance to the migration of the four types of gases in coal cores decreased in the order of FHe, F_(CO_2), F_(CH_4), and F_(N_2). The magnitude of the resistance was associated with the average effective diameter of gas molecules, the dynamic viscosity of gas, and gas phase change. The increases in the density and viscous resistance of supercritical gas led to significantly elevated resistance to gas migration. The threshold pressure gradients of the four types of gases decreased in the order of λ_(He), λ_(CO_2), and λ_(CH_4)(approximately equal to λ_(N_2)), and they were inversely proportional to the coal core length. The threshold pressure gradients were affected by the dynamic viscosity of gases, the pore characteristics of coal cores, and adsorptivity. The viscous resistance was generated by the interactions between the gases and pore walls and adsorption layers. The Reynolds numbers for the four types of gases decreased in the order of Re_(CO_2), Re_(N_2), Re_(CH_4), and Re_(He), increasing with the injection pressure and pore size. The adsorption of coal matrix for gas significantly affected the permeability and seepage velocity. N_2 exhibited a high permeability due to the weak adsorption of coals for it and small pore changes, with gas permeability in coal cores decreasing in the order of k_(He), k_(N_2), k_(CO_2), and k_(CH_4). Due to the strong adsorption of CO_2, it will cause the expansion of coal matrix, resulting in low permeability of coal core. There existed a critical pressure for gas migration in coal cores. When the injection pressure was less than the critical pressure, gas seepage exhibited nonlinear characteristics under the influence of adsorption and slippage effects. Otherwise, the gas seepage tended to be stable and gradually approached linear flow. The results of this study provide a theoretical basis for the process parameter optimization, efficiency enhancement, and engineering applications of CH_4 displacement through gas flooding.

    2026 01 v.54;No.337 [Abstract][OnlineView][Download 2095K]

  • Performance and carbonation mechanisms of multi-source solid waste-based carbonsequestering backfill materials for coal mines

    GUO Qingwen;LI Dongyin;WANG Shen;LIU Songhui;LI Quanjiang;LI Song;School of Energy Science and Engineering,Henan Polytechnic University;Collaborative Innovation Center of Coal Work Safety and Clean High Efficiency Utilization;Henan Polytechnic University-Jiaozuo Coal Group Intelligent,Safe and Efficient Mining R & D Center;School of Materials Science and Engineering,Henan Polytechnic University;

    [Objective] The reutilization of solid waste such as coal gangue and steel slag is critical to green mining. Preparing solid waste-based carbon-sequestering backfill materials and then filling them into coal mine goaves emerge as an important approach to solid waste utilization, carbon emission reduction, and green coal mining. [Methods] Based on the designed mix proportions of a high-solid-waste system consisting of steel slag and coal gangue, in which steel slag was used to compensate for the insufficient carbonation reactivity of coal gangue, this study prepared solid waste-based backfill material samples composed of coal gangue, steel slag, and cement. Through mechanical and carbon-sequestration tests in the laboratory, along with a range of test methods including thermogravimetric analysis(TGA), X-ray diffraction(XRD) analysis, scanning electron microscopy(SEM), Fourier transform infrared spectroscopy(FTIR), and mercury intrusion porosimetry(MIP), this study explored the mechanical properties, carbon sequestration capacity, and carbonation reaction mechanisms of these solid waste-based backfill materials. [Results and Conclusions] Carbonation temperature significantly affected the mechanical properties of the backfill materials. As the carbonation temperature increased from 40 ℃ to 80 ℃, the compressive strength of the samples showed an increasing trend. Increasing the steel slag content can enhance the compressive strength of the samples during the later curing stage. With an increase in the carbonation temperature, the CO_2 absorption capacity of the samples increased initially and then decreased. Notably, the sample comprising 35% calcined coal gangue and 50% steel slags yielded a CO_2 absorption capacity reaching up to 6.9%at a carbonation temperature of 60 ℃. Carbonation reactions promoted the formation of CaCO3 to fill material pores,while the active silico-aluminous phase accelerated the formation of calcium-silicate-hydrate( C-S-H) gel. Both aspects enabled the stable bonding between CaCO3 and C-S-H and thus enhanced the material density, serving as the key mechanisms for improving the performance of solid waste-based backfill materials. The results of this study provide theoretical support for developing high-performance, multi-source solid waste-based, carbon-sequestering backfill materials, contributing to the development of carbon sequestration technology for green mine backfilling.

    2026 01 v.54;No.337 [Abstract][OnlineView][Download 2421K]

  • Evolutionary mechanisms of nanopores and adsorption capacity in shales under ScCO2-water-rock interactions

    FENG Guangjun;WANG Meng;ZHU Yanming;SONG Yu;DAI Xuguang;ZHENG Sijian;XIE Hong;SHANG Fuhua;Key Laboratory of Coalbed Methane Resources & Reservoir Formation Process,Ministry of Education,China University of Mining and Technology;School of Resources and Geosciences,China University of Mining and Technology;Carbon Neutrality Institute,China University of Mining and Technology;School of Mines,Inner Mongolia University of Technology;

    [Background] Supercritical carbon dioxide(ScCO_2)-enhanced shale oil and gas recovery serves as an effective approach to geologic CO_2 sequestration. Injecting ScCO_2 into shale reservoirs can trigger complex ScCO_2-water-rock interactions, thereby altering the material composition, nanopore structure, and adsorption capacity of shales. Examining their evolutionary processes represents a critical scientific issue in the evaluation of CO_2 sequestration efficiency. [Methods] This study investigated the shales of the Longmaxi Formation in the southeastern Chongqing area. Through simulation experiments on ScCO_2-water-rock interactions and by integrating X-ray diffraction(XRD), low-pressure CO_2/N_2 adsorption, fractal theory, and isothermal adsorption experiments, this study explored the evolution mechanisms behind the material composition, nanopore structure, fractal heterogeneity, and adsorption capacity of shales under ScCO_2-waterrock interactions. By controlling the time, temperature, and pressure of ScCO_2-water-rock interactions, this study conducted in-depth analyses of factors affecting CO_2 adsorption and sequestration efficiency. [Results and Conclusions]The ScCO_2-water-rock interactions consisted primarily of organic matter extraction and dissolution, mineral dissolution,and ion-exchange reactions, which significantly reduced the mass fractions of the total organic carbon(TOC), carbonates, and clay minerals in shales. With an increase in the reaction time and pressure, the mass fractions of the organic and inorganic components in shales varied more significantly. Organic matter extraction and mineral dissolution led to increases in the volume and specific surface area of nanopores in shales. Elevated temperature primarily promoted the development of micropores measuring 0.9–1.5 nm in size. In contrast, a rise in pressure led to a significant increase in the volumes of both micropores(<2 nm) and mesopores(2–50 nm) while also enhancing the heterogeneity of pore structures. However, as the reaction time increased, secondary minerals precipitated and blocked pores. Notably, micropores and their heterogeneity were particularly susceptible to precipitation-induced volume reduction. Compared to subcritical temperature and pressure conditions, shales after CO_2-water-rock interactions exhibited a surge in CO_2 adsorption capacity and rate under supercritical conditions. Therefore, maintaining the temperature and pressure conditions for ScCO_2 is crucial to improvements in the CO_2 adsorption capacity and sequestration efficiency of shale reservoirs. Notably, in the long-term CO_2 sequestration process, the degradation of storage efficiency induced by secondary mineral precipitationassociated pore blocking warrants more attention. Overall, the results of this study provide a theoretical foundation for both the application of ScCO_2-enhanced shale oil and gas recovery and the scientific optimization of geologic CO_2 sequestration efficiency.

    2026 01 v.54;No.337 [Abstract][OnlineView][Download 1779K]

  • Huff-n-puff experiments of mixed CO2 and formation water for enhanced oil recovery of shale oil in the Subei Basin

    XIAO Pufu;ZHANG Jie;YANG Zhengmao;WANG Rui;CUI Maolei;LEI Mengmeng;TIAN Yunfei;ZENG Jun;LIU Yuwei;State Key Laboratory of Shale Oil and Gas Enrichment Mechanisms and Efficient Development;Petroleum Exploration and Production Research Institute,SINOPEC;East China Oil & Gas Company,SINOPEC;School of Chemistry and Chemical Engineering, Henan University of Technology;

    [Objective] In the Subei Basin, the depletion-drive development of shale oil following reservoir volume fracturing faces challenges such as rapid production decline and low oil recovery. To address these issues, this study explored an experimental method of CO_2 + formation water(also referred to as carbonated water) huff and puff for enhanced oil recovery(EOR) by combining the felsic, clayey, and organic-rich characteristics of shale oil reservoirs in the Subei Basin, along with CO_2 high pressure quality exchange technology. [Methods] Through multiple physical simulation experiments in the laboratory, combined with nuclear magnetic resonance(NMR) experiment technology, this study conducted dynamic and static experiments on cores, including high-temperature and high-pressure imbibition, dissolution, and carbonated water huff and puff, to verify the feasibility of carbonated water huff and puff for shale oil recovery.Variations in 2D NMR T_1-T_2 spectra were analyzed to determine the characteristics and patterns of the production of different types of crude oil during huff and puff. [Results and Conclusions] By creating acidic conditions, CO_2 huff and puff following imbibition could dissolve minerals such as calcites and dolomites in shale oil reservoirs, thus improving the microscopic pore-throat structures in the reservoirs, as well as the porosity and permeability of cores. Accordingly,the late-stage shale oil recovery was enhanced. Comparison of CO_2 and carbonated water huff and puff revealed that the carbonated water huff and puff increased the injection-production pressure difference, enhancing cumulative recovery by6.7%. In the first several rounds, CO_2 huff and puff achieved rapid and effective production of movable oil and light hydrocarbons, enhancing oil recovery more significantly. In contrast, in the late stage, the carbonated water huff and puff expanded the influence of CO_2 through dissolution and diffused CO_2 into more matrix pores. Consequently, the conversion between heavy hydrocarbons(or adsorbed oil) and light hydrocarbons was gradually achieved through mass transfer, resulting in significantly improved huff-n-puff performance. Therefore, to achieve the optimal shale oil recovery, it is advisable to adopt two rounds of CO_2 huff and puff in the early stage, followed by multiple rounds of carbonated water huff and puff in the late stage, when designing huff-n-puff schemes in the field. Overall, the results of this study reveal the mechanisms by which the carbonated water huff and puff enhance crude oil production, confirming the feasibility of this method for EOR of shale oil. This study provides a significant experimental basis and new directions for developing EOR technologies for shale oil reservoirs in the Subei Basin and even in eastern China.

    2026 01 v.54;No.337 [Abstract][OnlineView][Download 2039K]

  • Advances in research on CO2 corrosion mechanisms, modification, and application of cements for injection wells in geologic CO2 sequestration

    HAO Feng;ZHANG Zongfeng;WANG Hongmin;DU Shuai;HUANG Da;YANG Xuefeng;WANG Kexin;ZHANG Yu;Shanghai Offshore Oil & Gas Company,SINOPEC;

    [Background and Merhod] The wellbore integrity of CO_2 injection wells plays a critical role in maintaining the long-term safe operation of geologic CO_2 sequestration(GCS) projects. Well cement serves as the foremost wellbore integrity barrier, and its durability under GCS has emerged as a hot research topic both at home and abroad. This study systematically reviews the advances in research on the chemical corrosion mechanism of well cement under the operating conditions of GCS, technologies for cement modification for enhanced resistance to CO_2 corrosion, and non-Portland cement systems. Furthermore, the directions for the future development of well cement are proposed. [Advances]The corrosion of Portland cement essentially stems from the reactions of its hydration products, Ca(OH)_2 and C-S-H, in an acidic CO_2 environment. Among these, Ca(OH)_2 is preferentially consumed, while C-S-H exhibits a higher stability.Therefore, in the modification design of Portland cement, Ca(OH)_2 can be retained appropriately as a buffer during carbonation reactions. This measure helps maintain the cement performance for the long term. Although most laboratory acceleration experiments have revealed significant degradation of Portland cement when exposed to a CO_2 atmosphere,field evidence from sites exemplified by the SACROC block in the United States indicates that Portland cement can provide effective sealing for decades under sound cementation conditions. This discrepancy highlights the inadequacy of current experimental evaluation systems in simulating actual downhole environments(e.g., confining pressure, formation water chemistry, dynamic temperature and pressure conditions). Primary approaches to enhancing the resistance to CO_2 corrosion of Portland cement include reducing the cement matrix permeability, incorporating inert or active fillers to regulate the products of chemical reactions, and applying surface protective coatings. Among these, nano-SiO_2 can optimize the microstructures of cement and produce a synergistic effect by participating in pozzolanic reactions, emerging as an effective material for the modification of Portland cement to enhance its carbonation resistance. Despite having exhibited sufficient sealing performance in partial carbon capture and storage-enhanced oil recovery(CCS-EOR) projects,modified Portland cement faces the risk related to long-term durability under extreme conditions due to its thermodynamic metastability. Therefore, non-Portland cement systems prove a better choice for CCS-geologic sequestration wells aimed at permanent CO_2 sequestration. [Prospects] Presently, there remains a lack of unified standards for the experimental evaluation of long-term cement integrity under GCS conditions, leading to insufficient comparative data arising from methodological differences. In the future, it is necessary to establish standardized testing systems that cover lowtemperature, dynamic corrosion conditions while also highlighting the settlement stability of cement. The purpose is to enhance the value of evaluation results for guidance on engineering practices. Additionally, although non-Portland cement systems can fundamentally circumvent the carbonation risk, they suffer from limitations of practical applicability and field operability. Therefore, it is recommended to further conduct systematic research on material performance regulation, construction suitability, and cost effectiveness.

    2026 01 v.54;No.337 [Abstract][OnlineView][Download 1596K]

  • Research advances and prospects of geologic CO2 sequestration models

    HU Chenlin;DONG Cheng;SANG Shuxun;TANG Yong;LI Xin;ZHANG Bin;ZHAO Lingfeng;School of Geology and Mining Engineering, Xinjiang University;Xinjiang Key Laboratory for Geodynamic Processes and Metallogenic Prognosis of the Central Asian Orogenic Belt, Xinjiang University;School of Resources and Geosciences, China University of Mining and Technology;Huairou Laboratory,Xinjiang Research Institute;School of Petroleum Engineering, Yangtze University;

    [Background] The urgent need to respond to global climate change and to achieve carbon neutrality is driving geologic CO_2 sequestration technology to be increasingly large-scale, safe, and intelligent. Since the CO_2 sequestration process involves multi-physical field coupling, the engineering feasibility and long-term safety of CO_2 sequestration heavily rely on the capacity of numerical models to perform accurate characterization of complex subsurface processes.Therefore, establishing a model system, covering the entire process consisting of injection, migration, sequestration, and monitoring, that is suitable for various geobodies for CO_2 sequestration has emerged as a foundation for the engineering application of geologic CO_2 sequestration technology. [Advances] This study systematically expatiates on six types of core models for geologic CO_2 sequestration: multiphase flow, vertical integration, reactive transport, deep learning, CO_2 plume, and geomechanical models. Based on the practical validation through representative CO_2 sequestration projects across the world, this study develops a universal modeling methodology centered on the synergy between reservoir characteristics, algorithm selection, and monitoring requirements. Studies have revealed that in the injection phase, key parameters can be effectively optimized using Fourier algorithms coupled with the multiphase flow model; in the migration phase, the spatial distribution of CO_2 can be accurately traced using the plume model coupled with finite element and finite volume methods; in the monitoring phase, cap rock integrity and the fault reactivation risk can be systematically assessed using the geomechanical model, thereby enabling the full-chain dynamic safety characterization. [Prospects] Given complex geological conditions and the demand for long-term safe sequestration, future efforts should focus on intelligent modeling driven by both big data and artificial intelligence. It is advisable to establish a new generation of models that are capable of autonomous learning, real-time data assimilation, and dynamic optimization by deeply integrating geological mechanisms and multi-source monitoring data. The purpose is to significantly enhance prediction accuracy and scenario adaptability. This model system will further extend to a fully closed-loop system covering capture, transport, sequestration, utilization, and emission, thereby supporting the establishment and intelligent adjustment of the integrated scheme of the CO_2 sequestration-utilization cycle. Furthermore, this system will promote the transition of CO_2 sequestration from single-link simulation to whole-chain collaborative management. Overall, the results of this study provide a systematic methodology for the cross-scenario application of geologic CO_2 sequestration models and offer a pathway for the evolution of the model system toward prolonged effects and intelligence.

    2026 01 v.54;No.337 [Abstract][OnlineView][Download 2221K]

  • Numerical simulation of CO2 sequestration combined with enhanced geothermal energy extraction in deep saline aquifers

    XIE Zehao;ZHANG Liehui;ZHAO Yulong;CAO Cheng;KOU Zuhao;ZHANG Deping;LI Jinlong;State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University;Carbon Dioxide Capture,Storage and Enhanced Oil Recovery, Jilin Oilfield Company, PetroChina;Research Institute of Exploration and Development,Jilin Oilfield Company, PetroChina;

    [Objectives and Methods] Deep saline aquifers represent ideal spaces for geologic CO_2 sequestration while also featuring high geothermal gradients and abundant geothermal resources. The combination of CO_2 sequestration and geothermal energy extraction holds great significance for enhancing the CO_2 sequestration effect and achieving integrated resource development of deep saline aquifers. Therefore, this study proposed a development approach that combined CO_2 sequestration with geothermal energy extraction in deep saline aquifers and established a thermo-hydro-chemical coupling numerical simulation model of the gas-water two-phase flow. Accordingly, it explored the optimal injection mode, production and injection well patterns, and injection and production parameters [Results and Conclusions]Extracting formation water and geothermal energy during CO_2 injection can effectively delay the rise in formation pressure while also providing more spaces for CO_2 storage, with the CO_2 storage capacity increasing by 16 500 t. After the depletion of movable water, further geothermal energy extraction with CO_2 as the work fluid yielded an additional 6.60 MJ of heat while further increasing the CO_2 storage capacity by 30 800 t. Geochemical reactions occurred during CO_2 injection, increasing reservoir porosity and permeability by 0.002 2 and 0.43×10~(-3)μm~2, respectively. This creates favorable conditions for continuous CO_2 injection and geothermal energy extraction. Intermittent injection can delay the rise in the formation pressure to the greatest extent, identified as the optimal injection mode. It is recommended that production and injection wells should be arranged in the same aquifer and that more injection wells should be arranged in the structurally lower parts of reservoirs compared to production wells. The optimal injection and production parameters include an injection rate of 10 000 m3/day, an injection-to-production rate ratio of 0.8, an injection cycle of three months,and a cyclic injection-to-production time ratio of 1. The proposed new development approach offers a novel philosophy for geologic CO_2 sequestration in deep saline aquifers while also serving as a valuable reference for reaching the goals of carbon neutrality and peak carbon dioxide emissions and promoting efficient, collaborative resource development.

    2026 01 v.54;No.337 [Abstract][OnlineView][Download 2374K]

  • Numerical simulations of the impacts of CO2-induced calcite dissolution on the permeability and elastic parameters of rocks

    YANG Bo;XU Tianfu;FENG Guanhong;ZHU Huixing;Key Laboratory of Groundwater Resources and Environment, Ministry of Education, Jilin University;Jilin Provincial Key Laboratory of Water Resources and Environment, Jilin University;

    [Objective] CO_2 dissolution in water tends to induce mineral reactions, thus significantly changing the pore structure of rocks and further affecting their seepage and mechanical properties. This phenomenon poses a major impact on the suitability and long-term safety of geologic CO_2 sequestration engineering. [Methods] Using a simulation technology that combines the lattice Boltzmann method(LBM) and the finite element method(FEM), this study systematically investigated the calcite dissolution characteristics of calcite-bearing rock samples under varying injection rates of a saturated solution of CO_2. Furthermore, the dynamic evolution patterns of the permeability and elastic parameters(bulk and shear moduli) of the rock samples were revealed. [Results and Conclusions] At lower injection rates, the chemical reaction products became enriched in the mid-to-distal part of the samples, inhibiting calcite dissolution in this part. Consequently, the chemical reactions occurred merely near the injection port. As the injection rate increased, the saturated solution of CO_2 exhibited an enhanced capacity to penetrate samples and then diluted reactants. As a result, calcites in the mid-to-distal part could participate in the reactions, resulting in a more uniform spatial distribution of calcite dissolution positions across the samples. Calcite dissolution significantly enhanced the rock permeability, especially at higher injection rates. At lower injection rates(30-150 m/a), the solute transport was primarily achieved by diffusion, leading to an insignificant increase in rock permeability. When the injection rate increased to 750-18 750 m/a, the solute transport mechanism gradually transitioned into advection, leading to greater differences in the rock matrix structure and more pronounced permeability enhancement. For the fitting of the permeability-porosity relationship, the power function model generally exhibited fit index n ranging from 2.8 to 6.5, while the Carman-Kozeny model showed n values varying from 0.9 to 4.6. Notably, the n values of both models showed a monotonically increasing trend with an increase in the injection rate. Comparative analysis reveals that the Carman-Kozeny model outperformed the power function model in terms of prediction accuracy. Calcite dissolution significantly reduced the elastic properties of rocks. As the porosity increased from 0.44 to 0.56, both the shear and bulk moduli decreased by approximately 20%. Additionally, both moduli declined rapidly initially and then decreased slowly in the late stage. Such nonlinear evolution renders the power function model more advantageous than the traditional linear model. This study also revealed that the elastic properties of rocks experienced exacerbated degradation with an increase in the injection rate. Compared to the bulk modulus, the shear modulus was more sensitive to variations in the injection rate. This study determines the key mechanism where the fluid injection rate dominates the evolution of the permeability and mechanical properties of rocks by governing the spatial distribution of dissolution, providing a theoretical basis for assessing the long-term safety of geologic CO_2 sequestration sites.

    2026 01 v.54;No.337 [Abstract][OnlineView][Download 2243K]

  • Distribution characteristics and mechanisms of CH4 and CO2 adsorption in montmorillonite nanopores in water-bearing and saline environments

    DU Kai;RUI Zhenhua;QIAN Cheng;CHEN Siwei;State Key Laboratory of Petroleum Resources and Engineering, China University of Petroleum (Beijing);College of Petroleum Engineering, China University of Petroleum (Beijing);College of Geophysics, China University of Petroleum (Beijing);Hainan Institute of China University of Petroleum (Beijing);

    [Background] Carbon capture, utilization, and storage(CCUS) has emerged as a significant way to reduce greenhouse gas emissions under the guidance of the strategic goals of peak carbon dioxide emissions and carbon neutrality. With the continuous exploitation of unconventional hydrocarbon resources such as shale oil and gas, varying waterbearing and salinity conditions exert significant impacts on the occurrence stability and seepage behavior of CO_2, thereby reducing the efficiency and safety of CO_2 storage. Therefore, a thorough understanding of the competitive behavior and distribution patterns of CO_2 and other gases in shale nanopores under varying water-bearing and salinity conditions has become a critical scientific issue in the optimization of CO_2 storage and flooding processes. [Methods] To reveal the impacts of the water-bearing and saline environments on the occurrence and competitive behavior of typical gases, this study constructed slit-shaped nanopore models of montmorillonite under different water-bearing and salinity conditions through molecular dynamics simulations. Accordingly, it systematically analyzed the adsorption configurations, density distributions, diffusion behavior, and variations in interaction energy of CH_4 and CO_2 under various conditions. [Results and Conclusions] CH_4 and CO_2 exhibited significant differences in occurrence and migration behavior under dry, waterbearing, and saline conditions. In the dry system, CO_2 formed adsorption layers along montmorillonite surfaces, while the density of adsorbed CH_4 showed a bimodal distribution, with a maximum reaching up to 1.78 g/cm~3. After water was added to the dry system, water layers covered the montmorillonite surfaces, weakening gas-mineral interactions. Consequently, CO_2 and CH_4 migrated toward the nanopore center. Upon NaCl addition, CO_2 formed secondary adsorption layers at the interfaces, with the peak density of adsorbed CO_2 under a NaCl mass fraction of 20% recovering to about17% of the peak value in the dry system. With an increase in salinity, both CO_2 and CH_4 displayed decreased self-diffusion coefficients, especially CO_2, suggesting that CO_2 diffusion was more significanly restricted. While water films weakened the adsorption potential on the montmorillonite surfaces, Na~+ enhanced the interfacial re-adsorption of CO_2 through electrostatic shielding and hydration clustering. The results of this study reveal the molecular-scale CO_2 retainment in water-bearing and saline envionments.

    2026 01 v.54;No.337 [Abstract][OnlineView][Download 1884K]

  • Numerical simulations of the safety of geologic CO2 storage in saline aquifers in the Enping Sag, Pearl River Mouth Basin

    YU Tao;LI Xiwen;YANG Yunshi;CHEN Bingbing;JI Zemin;HE Chang;JIANG Lanlan;SONG Yongchen;Key Laboratory of Ocean Energy Utilization and Energy Conservation of Ministry of Education, Dalian University of Technology;State Key Laboratory of Enhanced Oil and Gas Recovery;Research Institute of Petroleum Exploration & Development,PetroChina;

    [Background] Since the beginning of the Industrial Revolution, excessive CO_2 emissions have aggravated the greenhouse effect. Against this backdrop, CO_2 capture, utilization, and storage(CCUS) technology has emerged as a critical countermeasure. Particularly, geologic CO_2 storage holds enormous application potential. China has implemented a demonstration project of geologic CO_2 storage in saline aquifers located in the Enping Sag, Pearl River Mouth Basin.Nevertheless, this sag exhibits formation dip angles and widely distributed fracture zones, which affect CO_2 migration and storage. [Methods] Focusing on the Enping Sag, this study established a two-dimensional model of the saline aquifer with a fracture zone using the TOUGH3 software. Using the established model, this study analyzed the impacts of factors, including formation dip angle, fracture zone location, and injection pressure, on the distributions of formation pressure, free CO_2, and dissolved CO_2, as well as the time-varying amounts of storage of various phases of CO_2 within reservoirs, during CO_2 storage. Through comparison of the amounts of CO_2 storage in the reservoirs, the influential mechanisms of varying factors on the upward migration and leakage of CO_2 were elucidated. Additionally, by analyzing the proportions of the amounts of dissolved CO_2 storage in varying reservoirs, this study revealed the role of different factors in determining the storage safety. [Results and Conclusions] During CO_2 injection, the fracture zone could release the pressure from the lower reservoir to the upper reservoir, thus alleviating the pressure rise in the middle cap rocks caused by the accumulation of free CO_2. At 100 a, CO_2 storage in the upper reservoir proved safer than that in the lower reservoir. In the formation at dip angles ranging from 0° to 2°, a higher formation dip angle led to a longer migration distance of free CO_2 in the reservoirs towards the updip direction. After 70 a, the risks of the upward migration and leakage of CO_2 were reduced. Between 20 a and 100 a, the safety of CO_2 storage in the reservoirs was enhanced, especially in the upper reservoir. Within a horizontal distance range of 50-200 m from the injection well, the risks of the upward migration and leakage of CO_2 decreased with an increase in the horizontal distance between the fracture zone and the injection well. However, the safety of CO_2 storage in the reservoirs decreased at 100 a. At injection pressure ranging from 16.5 MPa to 19.5 MPa, an increase in injection pressure corresponded to an increased total amount of CO_2 storage but a decreased proportion of the amount of the dissolved CO_2 storage at 100 a, with such storage tending to be unstable.At an injection pressure of 18.0 MPa, the proportion of the amount of CO_2 storage in the lower reservoir reached its maximum(42.21%), suggesting the lowest risks of the upward migration and leakage of CO_2. Among the three factors influencing CO_2 storage safety, formation dip angle and injection pressure determine the safety of CO_2 storage in the upper and lower reservoirs, respectively, while the horizontal distance between the fracture zone and the injection well serves as a major factor affecting the upward migration and leakage of CO_2. The results of this study will provide a theoretical basis for CO_2 storage projects in saline aquifers with fracture zones and deepen the understanding of the mechanisms behind CO_2 storage in analogous geological settings. Accordingly, the results will contribute to the large-scale application and industrial advancement of geologic CO_2 storage while also providing support for the attainment of peak carbon dioxide emissions and carbon neutrality.

    2026 01 v.54;No.337 [Abstract][OnlineView][Download 1876K]

  • Advances and prospects of research on in situ CO2 mineralization storage in basalts

    WANG Xiao;WU Bin;SHI Xiangchao;YE Zhongbin;WEI Bing;WANG Guanhua;Alvarado Vladimir;HUANG Kailin;YANG Zeyong;State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation,Southwest Petroleum University;Petroleum Engineering School,Southwest Petroleum University;Chengdu Technological University;Natural Resources and Planning Bureau of Xintai City;Department of Chemical and Biomedical Engineering,University of Wyoming;

    [Background] CO_2 storage in basalts, enjoying distinct advantages of rapid mineralization and high safety,has gradually emerged as a hot research topic both in China and abroad. This study presents a systematic review of the current status of research on the mechanisms of in situ CO_2 mineralization storage, the evolutionary characteristics of the physical properties of strata under the condition of mineralization reactions, and representative demonstration projects.On this basis, the future research directions are proposed. [Advances] The in situ CO_2 mineralization storage in basalts is essentially a process of CO_2-water-rock reactions, achieved primarily through both the dissolution of primary silicate minerals and the precipitation of secondary carbonate minerals, with the former limiting the speed of the whole reaction process. Through static autoclave experiments and dynamic core flooding experiments, existing studies have systematically revealed the dissolution and precipitation behavior of minerals in various types of basalts and have identified the mechanisms by which factors such as mineral composition, grain size/specific surface area, pH, temperature, and fluid composition regulate the kinetics and products of CO_2 mineralization reactions. Through the coupling of mineral dissolution and precipitation, CO_2 mineralization reactions alter the composition of minerals in strata while also significantly affecting their macroscopic physical properties, as manifested by pore structure reconstruction, porosity and permeability evolution, and mechanical property enhancement or weakness. These changes jointly determine the efficiency and geological safety of long-term CO_2 storage. The two global representative demonstration projects, i.e., the CarbFix project in Iceland and the Wallula project in the United States, employ two different CO_2 injection techniques. In the CarbFix project, CO_2-unsaturated aqueous solution is injected into basalts, with conversion used as the core logic. In this project,accelerated dissolution and mineralization reactions are employed for rapid CO_2 fixing, while isotope tracing technology is innovatively introduced to monitor the reaction process in real time. In contrast, the Wallula project focuses on CO_2 storage. In this project, supercritical CO_2 is injected into target strata, with caprocks and trap structures playing a key role in ensuring safe CO_2 sequestration. Additionally, geophysical logging is adopted to assess the CO_2 leakage risk. The two projects provide a valuable reference for the siting, design, and monitoring of CO_2 storage in basalts under various geological conditions. [Prospects] Although significant advances have been achieved in in-situ CO_2 mineralization storage in basalts, there is a urgent need to make breakthroughs in some key issues, including(1) the accurate identification and quantitative characterization of secondary minerals;(2) the understanding of the formation mechanisms of passivation layers and their inhibiting effects on reactions;(3) global sensitivity analysis of factors influencing CO_2 mineralization under actual complex geological-chemical coupling conditions; and(4) the decoupling and identification of multi-source and multi-sink reaction pathways in multi-mineral systems. Thoroughly investigating these issues will lay a core foundation for driving the large-scale applications of in situ CO_2 mineralization storage from demonstration, thus holding great significance for safe and efficient geological CO_2 sequestration in the future.

    2026 01 v.54;No.337 [Abstract][OnlineView][Download 2337K]

  • Advances in research on the in situ CO2 mineral trapping in buried volcanoes

    HE Yanxin;TIAN Wei;XIAN Benzhong;LIU Pingping;WEI Mingcong;WEI Qiwen;DENG Xuanyu;LIU Jianping;GU Jiapeng;School of Mining Engineering, Jiangxi University of Science and Technology;School of Earth and Space Sciences, Peking University;College of Geosciences, China University of Petroleum;School of Petroleum Engineering, Chongqing University of Science and Technology;

    [Objective and Methods] Driven by the goal of carbon neutrality, geologic CO_2 storage has become a critical national priority in China. Compared to conventional reservoirs in sedimentary basins, such as saline aquifers, depleted hydrocarbon reservoirs, and unmineable coal seams, basaltic formations offer more significant advantages in geologic CO_2 storage. Specifically, basaltic formations can form stable carbonates through reactions between CO_2 and rock minerals while also exhibiting extensive distribution, considerable potential for CO_2 storage, and low risk of CO_2 leakage. The engineering feasibility of geologic CO_2 storage in basaltic formations has been validated by the Iceland CarbFix and U.S. Wallula pilot projects. Buried volcanoes within sedimentary basins host abundant basaltic rocks, show an extensive distribution, and hold considerable potential for CO_2 storage, establishing them as potential targets for in situ CO_2 mineral trapping. However, there is a lack of systematic assessment of the feasibility, safety, and economic viability of in situ CO_2 mineral trapping in buried volcanoes. Therefore, this study analyzed the technical and economic feasibility of this technology based on the distribution, material composition, reservoir physical properties, reservoir-cap rock configuration of buried volcanoes, as well as the storage capacity, environmental risks, and cost-effectiveness related to in situ CO_2 mineral trapping. [Advances and Prospects] The buried volcanoes are globally widespread, holding enormous potential for CO_2 storage. They contain ferromagnesian mineral assemblages that enhance mineralization efficiency and hold high-quality reservoirs with abundant storage spaces. Moreover, their internal complex structures constitute natural reservoir-cap rock assemblages. All these characteristics make it theoretically and technically feasible to conduct geologic CO_2 storage in buried volcanoes. In terms of safety, the inherent safety of CO_2 mineral trapping, combined with multiple containment barriers at the basin scale, ensures minimal CO_2 leakage risks. As for economic viability, in addition to the low costs of in situ CO_2 mineral trapping itself, infrastructure reuse and synergistic storage in petroliferous basins can further reduce the costs, suggesting significant economic attractiveness. Therefore, buried volcanoes in sedimentary basins represent highly suitable targets for in situ CO_2 mineral trapping, outperforming typical basaltic formations in terms of technical feasibility, safety, and economic viability. Nevertheless, this technology still faces some technical limitations. For instance, mechanisms behind CO_2-fluid-rock interactions remain poorly understood, and the internal architectures of volcanoes are difficult to characterize. Therefore, future efforts should focus on the multi-field coupling experiments and simulations of CO_2-fluid-rock interactions, as well as the fine-scale characterization of buried volcano architectures. Characteristics such as geological conditions reveal that priority zones for CO_2 storage in buried volcanoes in China include the Tarim Basin(a land area in West China) and the Pearl River Mouth Basin(a sea area in East China). The results of this study provide reliable targets and geological bases for attaining the carbon neutrality goal.

    2026 01 v.54;No.337 [Abstract][OnlineView][Download 2633K]

  • Advances in research on geochemistry of CO2 storage in basalts: Microscopic mechanisms and reaction pathways

    MA Shijia;XIA Changyou;GAO Zhihao;RUI Zhenhua;LIANG Xi;UK-China (Guangdong) CCUS Centre;State Key Laboratory of Petroleum Resources and Engineering, China University of Petroleum (Beijing);University College London;

    [Objective and Method] The urgent need to reduce global greenhouse gas emissions has driven the development of CO_2 mineral trapping in basalts. To gain further insights into the microscopic mechanisms and reaction pathways of the mineral trapping, this study systematically reviews the geochemical reaction mechanisms involved, with a particular focus on the differences in reaction pathways between supercritical and dissolved CO_2 injection, the coupling between mineral dissolution and carbonate precipitation, and the key factors influencing these reactions. [Advances] In the case of supercritical CO_2 injection, CO_2 mineral trapping is achieved through multi-step coupling reactions in nanoscale hydration layers. Under dissolved CO_2 injection, the mineral trapping is primarily achieved through chemical dissolution and coordination reactions in the aqueous phase. In the geochemical reactions during CO_2 mineral trapping in basalts, minerals such as olivine and pyroxene play a dominant role in the release of metal cations, while carbonate minerals including calcite, magnesite, and ankerite precipitate sequentially under different temperature and pressure conditions. Calcite exhibits broad temperature adaptability, whereas magnesite and ankerite are commonly observed under moderately high temperature conditions. Factors such as pH, temperature, CO_2 partial pressure(p_CO_2)), fluid salinity, and rock heterogeneity exert significant impacts on reaction pathways and the evolution of minerals precipitated. Specifically, low pH accelerates the dissolution of primary minerals, while high pH creates favorable conditions for the precipitation of carbonate minerals. Elevated temperatures promote mineral dissolution, thus increasing the reaction rates. High CO_2 partial pressure can enhance the solubility and reactivity of CO_2, thereby accelerating mineral dissolution and carbonate formation. Fluid salinity affects the dissolution and precipitation processes of minerals by changing the ionic strength and chemical composition of solutions. Rock heterogeneity, including differences in mineral compositions and pore structures, affects fluid transport pathways and reaction efficiency. Furthermore, it facilitates localized precipitation and the formation of preferential flow channels, enabling sustained precipitation in low-flow and disconnected channels.It is necessary to investigate the impacts of rock heterogeneity on reservoir physical properties in the future. The abovementioned factors interact with each other, jointly determining the dynamic evolution of CO_2 mineral trapping. [Prospects] Future research directions are proposed in this study based on the review, including the establishment of parameter optimization frameworks, the construction of high-resolution coupling models, and the optimization of CO_2 injection strategies. These efforts will promote the large-scale applications and engineering implementation of CO_2 storage in basalts. Additionally, a thorough investigation into the mechanisms behind the synergy among the influential factors of reactions will lay a solid theoretical foundation for the optimization of CO_2 storage technology, thus further improving the efficiency and stability of CO_2 mineral trapping.

    2026 01 v.54;No.337 [Abstract][OnlineView][Download 2158K]