Article
Energy & Fuels
Ming-Yao Wei, Jishan Liu, Ying-Ke Liu, Zhang-Hao Liu, Derek Elsworth
Summary: Gas transport in coal leads to stress variation, affecting porosity and permeability evolution. Neglecting the heterogeneity and anisotropy of coal in dual porosity models can deviate from real physical mechanisms. Advanced virtual simulation incorporating real fracture geometry reveals non-uniform distribution of fracture geometry as a key factor impacting permeability change.
Article
Energy & Fuels
Xiang Li, Chuanzhong Jiang, Jishan Liu, Yixin Zhao
Summary: In this study, a new concept of the differential strain index (DSI) is proposed to define the relationship among desorption-induced strains of coal bulk, pores and solid grains. DSI is a function of gas pressure, regulated by Langmuir constants. A DSI-based coal permeability model is incorporated into the coupled multiphysics model for coal seam gas production, showing significant changes in coal permeability controlled by the DSI. The magnitudes and trends of change are defined by Langmuir strain ratio and pressure ratio, respectively.
Article
Engineering, Geological
Xiang Zhou, Shimin Liu, Yida Zhang
Summary: This study investigates the interplay between adsorption, deformation, and permeability evolution of coals by adopting the novel concept of adsorption stress popularized in material science research. The prediction covers a wide range of permeability data obtained from laboratory tests and field observations, showing the competition between desorption-induced fracture opening and poroelastic compaction controlled by various ratios.
ROCK MECHANICS AND ROCK ENGINEERING
(2021)
Article
Energy & Fuels
Zhao Yaoyao, Zhao Yixin, Liu Jishan, Wei Mingyao, Cui Dongxue, Gao Sen
Summary: Permeability is a key parameter for evaluating the ability of coal reservoirs to transmit coalbed methane. The deformations of coal caused by physical field variations control the permeability evolution, and there is obvious non-uniformity in the deformations due to coal heterogeneity. However, the relationship between non-uniform deformation and permeability is unclear. This study conducted experiments to measure the permeability and deformations of a coal sample under different boundary conditions and injection pressures. The results showed anisotropic mechanical properties of the coal sample and differences in deformations between coal bulk and fractures.
Article
Geosciences, Multidisciplinary
Jianhua Li, Bobo Li, Qiaoyun Cheng, Zheng Gao
Summary: Permeability is a key parameter for understanding coalbed methane mining and carbon dioxide geological storage. Coal exhibits distinct deformation characteristics due to the presence of soft and hard parts in fractures, which affect permeability. The study also found that coal shows strong anisotropy under reservoir conditions, with varying permeability in different directions.
NATURAL RESOURCES RESEARCH
(2021)
Article
Energy & Fuels
Yaoyao Zhao, Yixin Zhao, Jishan Liu, Mingyao Wei, Yifan Huang, Chuanzhong Jiang
Summary: In this study, a new multi-physical field coupling model was established to accurately predict the non-uniform deformation between coal bulk and fractures. Three kinds of non-uniform deformation indexes were defined and the theoretical solutions of the model were validated with experimental results. Additionally, the concept of modified effective stress was proposed to address the inconsistency between theoretical and experimental permeability solutions under constant effective stress condition.
Article
Engineering, Environmental
Jia Lin, Ting Ren, Yuanping Cheng, Jan Nemcik
Summary: CO2 geo-sequestration in unminable coal seams shows promise in reducing greenhouse gas emissions and enhancing coal bed methane recovery, but faces challenges in permeability reduction effects post-injection.
PROCESS SAFETY AND ENVIRONMENTAL PROTECTION
(2021)
Article
Engineering, Geological
Rui Shi, Jishan Liu, Xiaoming Wang, Derek Elsworth, Zhizhuang Wang, Mingyao Wei, Guanglei Cui
Summary: Gas adsorption/desorption in fractured shale can cause swelling/shrinking of the matrix, with significant contrast in permeability between fractures and matrix leading to prolonged equilibration time for gas injection or depletion-induced pressure difference. The development of strain gradients near fractures in the matrix under constant confining pressure conditions influences the evolution of fracture permeability.
ROCK MECHANICS AND ROCK ENGINEERING
(2021)
Article
Energy & Fuels
Guanglei Cui, Wangxing Cheng, Wei Xiong, Tianyu Chen, Yong Li, Xia-Ting Feng, Jishan Liu, Derek Elsworth, Zhejun Pan
Summary: The co-production of gas from coalbeds and tight formations is a viable means to improve well productivity. However, previous studies have not paid much attention to the effectiveness of gas co-production with regard to well types. In this study, a coupled model is proposed to analyze the impacts of gas co-production and different reservoir interactions. The results provide recommendations for the use of horizontal or vertical wells based on the characteristics of the reservoirs and well life.
Article
Energy & Fuels
Ang Liu, Shimin Liu, Peng Liu, Satya Harpalani
Summary: Matrix shrinkage is a unique property of coal that affects sorption-induced strain. Models can quantify the effects of matrix shrinkage, and experiments validate the changes in coal under different stress conditions.
Article
Geosciences, Multidisciplinary
Jun Tang, Jie Zhu, Tangsha Shao, Jinge Wang, Yaodong Jiang
Summary: Fracture compressibility and strain conditions play a crucial role in coal permeability evolution. The new permeability model derived in this study, considering variable fracture compressibility, showed more accurate results compared to the model with constant fracture compressibility. Coal fracture compressibility generally decreases with increasing effective stress and responds differently to changes in gas pressure and type.
NATURAL RESOURCES RESEARCH
(2021)
Article
Energy & Fuels
Haoze Li, Bingxiang Huang, Qingying Cheng, Xinglong Zhao, Bin Chen, Long Zhao
Summary: This paper focuses on the influence of proppant embedding in coal on the fracture surface, analyzing the embedding law from macro and micro perspectives and establishing a damage model. The energy of proppant is released first, followed by the energy of the coal during the embedding process.
Article
Engineering, Environmental
Junqiang Kang, Derek Elsworth, Xuehai Fu, Shun Liang, Hao Chen
Summary: The adsorption of methane in coal releases heat and causes thermal expansion, which is related to adsorption swelling and adsorption capacity. The study finds that thermal expansion due to adsorption heat may contribute to 35% of the total adsorption strain under ideal isentropic conditions. Laboratory experiments cannot accurately measure the thermal expansion during adsorption, but reduced heat dissipation in coalbed reservoirs may retain thermal deformation and affect short-term permeability evolution.
CHEMICAL ENGINEERING JOURNAL
(2022)
Article
Chemistry, Physical
Kun Yu, Kaidi Zhao, Yiwen Ju
Summary: The low permeability of unconventional reservoirs, particularly coal and clay-rich shale, can significantly impact the production efficiency of methane due to the unique water sensitivity and swelling mechanism of clay minerals. Hydraulic fracturing can enhance the permeability of these reservoirs, with clay-rich shale showing better improvement than coal.
APPLIED CLAY SCIENCE
(2022)
Article
Geosciences, Multidisciplinary
Stefan Iglauer, Hamed Akhondzadeh, Hussein Abid, Adriana Paluszny, Alireza Keshavarz, Muhammad Ali, Ausama Giwelli, Lionel Esteban, Joel Sarout, Maxim Lebedev
Summary: The study shows that geo-storage of H-2 in coal seams is feasible, which can contribute to the large-scale implementation of a hydrogen economy.
GEOPHYSICAL RESEARCH LETTERS
(2022)
Article
Energy & Fuels
Guanglei Cui, Wangxing Cheng, Wei Xiong, Tianyu Chen, Yong Li, Xia-Ting Feng, Jishan Liu, Derek Elsworth, Zhejun Pan
Summary: The co-production of gas from coalbeds and tight formations is a viable means to improve well productivity. However, previous studies have not paid much attention to the effectiveness of gas co-production with regard to well types. In this study, a coupled model is proposed to analyze the impacts of gas co-production and different reservoir interactions. The results provide recommendations for the use of horizontal or vertical wells based on the characteristics of the reservoirs and well life.
Article
Energy & Fuels
Wai Li, Jishan Liu, Jie Zeng, Yee-Kwong Leong, Derek Elsworth, Jianwei Tian
Summary: This study developed a multidomain and multiphysics model to improve the simulation accuracy and obtain insights into coalbed methane (CBM) extraction. The model successfully coupled different physical processes and stimulation patterns to better understand CBM extraction. The findings suggest that the properties of different domains and the thermal effects can significantly influence CBM production, and increasing fracture complexity and improving stimulation techniques can enhance CBM recovery.
JOURNAL OF PETROLEUM SCIENCE AND ENGINEERING
(2022)
Article
Energy & Fuels
Jianwei Tian, Jishan Liu, Derek Elsworth, Yee-Kwong Leong, Wai Li
Summary: The fractal nature of coal pore sizes affects both coal absolute and relative permeabilities. This study employs the fractal theory to derive new relative permeability models and conducts sensitivity studies to understand the impact of fractal dimensions on gas production.
Review
Energy & Fuels
Qi Gao, Jishan Liu, Yifan Huang, Wai Li, Rui Shi, Yee-Kwong Leong, Derek Elsworth
Summary: The evolution of coal permeability is complex and has led to the development of numerous models. Despite efforts to evaluate these models, the reasons for discrepancies between observations and predictions have not been identified. This study examines the models and concludes that they can be categorized into equilibrium and non-equilibrium models based on the internal structure of coal, boundary conditions, and equilibrium state. It is found that the exclusion of equilibration process is the root cause of discrepancies and suggests future research should integrate rock structure, boundary conditions, and equilibration process in coal permeability models.
Article
Chemistry, Physical
Yee-Kwong Leong, Pengfei Liu, Jishan Liu, Peta Clode, Weian Huang
Summary: Composite NaMnt (SWy-2)-kaolin (KGa-2) gels with more than 10 wt% solids and a NaMnt fraction of 20% exhibit an open cellular microstructure. The flexible nanosized NaMnt platelets form a continuous structure with dispersed kaolin particles, resulting in various unique particle interaction configurations. The study also reveals the thixotropic and rheopectic behaviors of a 15.5 wt% gel with a 1:2 mass ratio of NaMnt to kaolin. Evaluation of the gel's structural development kinetics and aging behavior further provide insights into the formation process of continuous structures. Rating: 8/10.
COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS
(2023)
Article
Energy & Fuels
Jie Zeng, Jianchun Guo, Jishan Liu, Wai Li, Yingfang Zhou, Jianwei Tian
Summary: A fully anisotropic coal permeability model is established, incorporating stress sensitivity, anisotropic internal swelling/shrinkage, and gas rarefaction effects. The model's reliability is demonstrated through comparisons with coal anisotropic swelling data and anisotropic permeability evolution data. Results show that anisotropic internal swelling/shrinkage mainly determines the overall shape, evolution trend, range of permeability change, and anisotropy level of permeability curves.
Article
Energy & Fuels
Xingxing Liu, Liang Chen, Jinchang Sheng, Jishan Liu
Summary: In this study, a concept of local non-equilibrium index (LNEI) is proposed to define a complete permeability model under the influence of gas extraction/injection. The non-equilibrium model takes into account the transient nature of local equilibration evolution and is able to explain permeability data more accurately. The model is verified against experimental data and applied to predict the effects of local equilibration on coal permeability and gas production under field conditions.
Article
Energy & Fuels
Jianwei Tian, Jishan Liu, Derek Elsworth, Yee-Kwong Leong, Wai Li
Summary: In this study, a dual-fractal permeability model was proposed to investigate the impacts of coal internal structure on permeability. The model considers the effects of pore-fracture size distribution and effective stress, and incorporates multiple flow mechanisms.
Article
Geochemistry & Geophysics
Peng Dong, Rong Chen, Kaiwen Xia, Wei Yao, Zhigang Peng, Derek Elsworth
Summary: This study investigates dynamically triggered earthquakes on laboratory faults and reveals that the triggering process has two distinct phases, with a slow phase only present for a specific seismic condition and absent for supershear events.
SEISMOLOGICAL RESEARCH LETTERS
(2023)
Review
Energy & Fuels
Qi Gao, Jishan Liu, Yee-Kwong Leong, Derek Elsworth
Summary: The significant effects of gas sorption induced swelling on shale permeability have been studied through laboratory measurements and explained using permeability models. However, there are lab observations that cannot be explained by these models, leading to a knowledge gap. In this review, the authors aim to resolve this gap by assessing the role of swelling on shale permeability through data collection, model classification, and correlation assessments. The findings suggest that discrepancies between model predictions and lab measurements depend on various factors, including the relationship between bulk and pore swelling strains, pore size scales, and consistency of strain treatments. The authors propose that future research should focus on characterizing the transformation between bulk and pore swelling strains, considering shale multiscale pore structural characteristics, and incorporating the time-dependent nature of swelling strain and permeability evolution.
Article
Energy & Fuels
Zhao Yaoyao, Zhao Yixin, Liu Jishan, Wei Mingyao, Cui Dongxue, Gao Sen
Summary: Permeability is a key parameter for evaluating the ability of coal reservoirs to transmit coalbed methane. The deformations of coal caused by physical field variations control the permeability evolution, and there is obvious non-uniformity in the deformations due to coal heterogeneity. However, the relationship between non-uniform deformation and permeability is unclear. This study conducted experiments to measure the permeability and deformations of a coal sample under different boundary conditions and injection pressures. The results showed anisotropic mechanical properties of the coal sample and differences in deformations between coal bulk and fractures.
Article
Computer Science, Interdisciplinary Applications
Jianwei Tian, Jishan Liu, Derek Elsworth, Yee-Kwong Leong
Summary: In this study, a 3D discrete fracture model (DFM) was proposed to represent the distribution of natural fractures (NFs). Gas flow in shale matrix was represented by a dual-fractal permeability model (DFPM). A hybrid DFPM-DFM model was proposed to couple gas flow and geomechanics and solved using finite element method. The model was verified with field data and used to investigate the impacts of fractally-distributed pore size and fracture attributes on permeability evolution and gas production.
COMPUTERS AND GEOTECHNICS
(2023)
Review
Energy & Fuels
Bashirul Haq, Nasiru Salahu Muhammed, Jishan Liu, Hui Tong Chua
Summary: This critical review comprehensively examines the technical aspects of carbon dioxide enhanced gas recovery (CO2-EGR) for hydrogen production. The study finds that high pressure and moderate injection rates can improve EGR, while heterogeneous reservoirs tend to yield lower recovery rates. Factors such as flow rate, pressure, temperature, connate water, brine saturation, shale content, and the type of fluid phase used for injection significantly affect the molecular diffusivity of the injected gas and subsequent recovery outcomes. Simulation studies highlight the potential of injecting various gases with proper reservoir operation timing to enhance recovery and enable sustainable hydrogen production.
Article
Energy & Fuels
Yaoyao Zhao, Yixin Zhao, Jishan Liu, Mingyao Wei, Yifan Huang, Chuanzhong Jiang
Summary: In this study, a new multi-physical field coupling model was established to accurately predict the non-uniform deformation between coal bulk and fractures. Three kinds of non-uniform deformation indexes were defined and the theoretical solutions of the model were validated with experimental results. Additionally, the concept of modified effective stress was proposed to address the inconsistency between theoretical and experimental permeability solutions under constant effective stress condition.
Article
Energy & Fuels
Qi Gao, Jishan Liu, Yaoyao Zhao, Mingyao Wei, Yee-Kwong Leong, Derek Elsworth
Summary: Approximately 20% of global natural gas resources may be microbial in origin, leading to significant interest in extracting biogenic gas from coal seams. Previous studies have shown that this can be achieved through injecting nutrients solution into a coal reservoir, stimulating microbial growth and enhancing biodegradation of organic components into methane gas. In this study, a modeling tool is developed to validate this concept under laboratory and reservoir conditions, coupling various physical and biological processes. The model is verified against experimental data and applied to simulate practical operations, demonstrating the effectiveness of coal-to-methane bioconversion and extraction.
GEOENERGY SCIENCE AND ENGINEERING
(2023)