Article
Geochemistry & Geophysics
Nai Cao, Gang Lei, Yuan Su, Hong Li, Jiali Zhang, Ci Zhang
Summary: The study on flow in fractured-vuggy carbonate reservoirs under pseudosteady state conditions is crucial for describing the productivity index of the well. Research found that fracture surface morphology and effective stress significantly affect productivity, and various factors can lead to changes in well productivity.
Article
Energy & Fuels
Adelina Lv, Mohammad Ali Aghighi, Hossein Masoumi, Hamid Roshan
Summary: The study investigates the mechanisms influencing wave propagation in fractured coals through a combination of ultrasonic transmission and XRCT imaging. The results show that the closure of fractures by matrix swelling predominantly controls the change in wave velocities, while the effect of gas adsorption on matrix properties on wave propagation is trivial. Further numerical simulations confirm the insignificant impact of changes in coal matrix properties by gas adsorption on wave velocity. The findings have implications for characterizing and monitoring coal seam gas production and gas drainage.
INTERNATIONAL JOURNAL OF COAL GEOLOGY
(2022)
Article
Engineering, Chemical
Peng Liu, Jinyang Fan, Deyi Jiang
Summary: This study conducted a series of permeability tests on coal using the pulse-decay method for helium, CH4, and CO2 depletions under different conditions, revealing differences in permeability behavior between helium and sorbing gases, particularly with regard to the rebound effect. The results suggest that the matrix shrinkage is a main factor causing the permeability 'rebound' of sorbing gases, highlighting the importance of matrix flows in coalbed methane production.
TRANSPORT IN POROUS MEDIA
(2021)
Article
Mechanics
Fuyong Wang, Hui Yue
Summary: This paper presents a generalized mathematical model that comprehensively characterizes the flow behavior of matrix nanopores and natural/hydraulic fractures in tight oil reservoirs during spontaneous imbibition. The proposed model considers the fractal characteristics of pores and fractures and accounts for many factors to predict cumulative oil production, oil flow rate, and oil recovery factor during imbibition flow. Experimental data on fractured tight sandstones are used to validate the model, and sensitivity analyses are conducted to assess the influence of various factors on imbibition behavior.
Article
Engineering, Chemical
Yubing Liu, Dong Zhao, Yiteng Li, Li Zhang
Summary: This study investigated the permeability of intact and fractured coal specimens and analyzed the fitting results based on established permeability models. The results showed that fractured coal exhibited an L-shaped permeability trend, while intact coal had an S-shaped trend. Macroscopic fractures increased the permeability of coal samples by 1-3 orders of magnitude, and the slip of the fracture surface resulted in permeability fluctuations.
Article
Engineering, Petroleum
Lan Mei, Wei Wei, Jianchao Cai, Qingbang Meng
Summary: This study enhances the understanding of the fluid exchange behavior of counter-current imbibition in strong water-wet and moderate water-wet fractured reservoirs. The research establishes a time-dependent shape factor (TDSF) related to the microscopic pore structure using fractal theory and carries out sensitivity analysis. The results show that the unsteady-state duration of TDSF is proportional to the characteristic length and tortuosity fractal dimension of the matrix, and inversely proportional to the maximum pore diameter of the matrix.
Article
Geochemistry & Geophysics
Xuyang Zhang, Jianming Zhang, Cong Xiao
Summary: This study experimentally investigates the influence of fracture systems on the characteristics of two-phase displacement seepage in tight sandstone sample cores, revealing the importance of fractures in the oil-water two-phase seepage mechanism after hydraulic fracturing treatment. The experimental results demonstrate that fractures shorten the water-free production period and reduce the recovery rate.
Article
Geochemistry & Geophysics
Haifeng Ma, Fanfan Yao, Xin'gang Niu, Jia Guo, Yingming Li, Zhiqiang Yin, Chuanming Li
Summary: The study investigated the mechanical behavior and permeability characteristics of coal under the coupling action of stress and seepage, revealing that the confining pressure influences the permeability of the briquette by affecting its dilatancy behavior. As the confining pressure increases, the permeability of the sample decreases, with a logarithmic function at the initial stage and a power function after failure, leading to a decrease in permeability coefficient.
Article
Polymer Science
Tao Wu, Qian Wang, Shifang Wang
Summary: The apparent gas permeability model for real gas flow in fractured porous media, derived in this paper, takes into account real gas effects, the roughness of fracture surface, and Knudsen diffusion based on fractal theory. The predictions match well with published permeability models and experimental data, confirming the rationality of the proposed model.
Article
Energy & Fuels
Xia Yan, Hai Sun, Zhaoqin Huang, Lijun Liu, Ping Wang, Qi Zhang, Jun Yao
Summary: This article presents a new hierarchical approach for simulating hydromechanical coupling in fractured shale gas reservoirs with multiple porosity scales. The method uses equivalent mesoscopic models and two-level homogenization to represent materials and fractures implicitly through an equivalent continuum model, while explicitly considering hydraulic fractures. Test and application of this hierarchical approach show its effectiveness in studying various factors affecting gas production.
Article
Chemistry, Physical
Shanshan Yang, Mengying Wang, Sheng Zheng, Shuguang Zeng, Ling Gao
Summary: Based on the statistical self-similar fractal characteristics of porous media microstructure, a permeability analysis model of fluids in a matrix-embedded fracture network is established. The predicted values show that the permeability of rough fracture network and rough matrix pores decreases with increasing relative roughness, and is lower than experimental data. The total flow rate of rough fractured dual porous media is lower than that of a smooth fractal model and experimental data. Additionally, the relative roughness of the fracture network has a greater influence on fluid permeability than the relative roughness of matrix pores in the fractured dual porous media.
Article
Multidisciplinary Sciences
Menglai Wang, Dongming Zhang
Summary: The water permeability of fractured shale in the Qiongzhusi Formation was studied under varying pressure and stress conditions. Results showed an increase in permeability with pressure differential and a decrease in permeability with increasing effective stress, although this effect decreased as the effective stress continued to increase. Interestingly, shale permeability increased with pressure at low pressures, which was inconsistent with classic Darcy's theory. The proposed permeability model accurately captured experimental data in a wide range of stresses.
ROYAL SOCIETY OPEN SCIENCE
(2021)
Article
Geochemistry & Geophysics
Yanan Gao, Peng Guo, Zetian Zhang, Minghui Li, Feng Gao
Summary: The study shows that fractures have a quantitative impact on concentration distribution, while faults dominate concentration distribution and contaminant migration. The migration of contaminants can be divided into three zones along the fault direction: saturation zone, rapid diffusion zone, and concentration decrease zone. Over time, the accumulation of contaminants experiences a slow growth stage followed by a rapid growth stage. During the slow growth stage, contaminant migration is mainly through faults, while in the rapid growth stage, contaminants penetrate both through the rock matrix and faults.
Article
Mathematics, Applied
Aleksei Tyrylgin, Maria Vasilyeva, Anatoly Alikhanov, Dongwoo Sheen
Summary: In this paper, a multiphysics poroelasticity problem in multicontinuum media is considered. The authors propose an implicit finite difference approximation based on Caputo's time fractional derivative for time discretization, and use a Discrete Fracture Model (DFM) and the Generalized Multiscale Finite Element Method (GMsFEM) for modeling and numerical solution. The results show that the proposed method achieves good accuracy on a coarse grid.
JOURNAL OF COMPUTATIONAL AND APPLIED MATHEMATICS
(2023)
Article
Mechanics
Dongxu Zhang, Liehui Zhang, Huiying Tang, Shuwu Yuan, Hui Wang, Shengnan (Nancy) Chen, Yulong Zhao
Summary: A discrete fracture model was proposed in this study to simulate rock deformation and two-phase flow behaviors in NFR, with sensitivity analysis conducted on key parameters. Results showed that the fluid-solid coupling effect weakened with production time, decreased with increased matrix permeability, fracture connectivity controlled the water flood front, and water injection intensity affected natural fracture opening deformation and well productivity.
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
Energy & Fuels
Wai Li, Jishan Liu, Jie Zeng, Yee-Kwong Leong, Derek Elsworth, Jianwei Tian
Summary: This study proposes the concept of kerogen threshold differential pressure (KTP) to describe the influence of water on gas liberation from kerogen. A fully coupled, multidomain, and multiphysics model is developed to simulate gas extraction from stimulated shale reservoirs, and a sensitivity analysis is performed to investigate the effects of important factors.
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)