Article
Energy & Fuels
Wei Liu, Deyao Wu, Hao Xu, Xiangyu Chu, Wei Zhao, Yinlei Yang
Summary: A permeability evolution model was developed with initial permeability and deformation coefficient as crucial parameters. The model was validated against gas permeability data and indicated that as volatile matter content increases, permeability decreases exponentially.
ENERGY SCIENCE & ENGINEERING
(2021)
Article
Chemistry, Multidisciplinary
Kang An, Songwei Shan, Yanfei Zhong, Haidong Chen, Guangwei Xu, Xiangjun Chen, Zhaofeng Wang
Summary: Affected by tectonics, China has widely distributed soft and hard composite coal seams; the stratification of soft layers in these seams plays a key role in controlling coal and gas outburst accidents. To accurately extract the soft layers, a directional hydraulic coal mining equipment, including a drilling rig pump truck system, a directional coal wireless measurement system, and a cutter drill pipe system, has been developed. Mathematical modeling and numerical simulations show that the stress and gas pressure around the borehole significantly decrease after coal extraction. On-site tests demonstrate that directional hydraulic coal extraction can achieve a volume of 0.25 m(3) per meter, with over 3% of the total coal within the coverage area being extracted. The average gas extraction concentration in the coal extraction area is 80.15%, and the net gas extraction from 100 m boreholes reaches 0.17 m(3)/(min & BULL;hm). Directional hydraulic coal mining technology effectively prevents coal and gas outbursts in soft and hard composite coal seams and has promising applications.
Article
Engineering, Geological
Chunguang Wang, Jidong Zhang, Junguo Chen, Ruizhi Zhong, Guanglei Cui, Yujing Jiang, Weitao Liu, Zhongwei Chen
Summary: The deformation of coal during gas depletion involves bulk compression controlled by effective stress and coal matrix swelling/shrinkage induced by gas sorption/desorption. Introducing an internal swelling coefficient into permeability models is crucial for considering the complex interaction between fracture and matrix, and improving prediction accuracy. The experimental and numerical results highlight the importance of understanding the contribution of matrix deformation to fracture behavior in coal reservoirs.
INTERNATIONAL JOURNAL OF ROCK MECHANICS AND MINING SCIENCES
(2021)
Article
Energy & Fuels
Mohammed A. Aldhuhoori, Hadi Belhaj, Hamda K. Alkuwaiti, Bisweswar Ghosh, Ryan Fernandes, Rabab Qaddoura
Summary: This study introduces a new comprehensive flow model suitable for tight UCRs, incorporating viscous, inertia, and diffusion forces to account for fluid transport at three scales. It was found that in cases of lower permeability of porous medium and lower viscosity of flowing fluid, the diffusion mechanism plays a more predominant role in controlling flow velocity.
JOURNAL OF PETROLEUM SCIENCE AND ENGINEERING
(2021)
Article
Energy & Fuels
Yaoyao Zhao, Dongxue Cui, Jishan Liu, Mingyao Wei, Yingke Liu
Summary: This study introduced a gas expansion-based experimental technique to measure overall strain, fracture strain, and calculate matrix strain of coal for determining permeability under nonequilibrium conditions. The results indicated that the permeability profiles were similar in shape but slightly varied in magnitude. This finding highlights the significance of considering transient effects in coal seam gas extraction.
Article
Geosciences, Multidisciplinary
Zhiheng Cheng, Hui Pan, Quanle Zou, Zhenhua Li, Liang Chen, Jialin Cao, Kun Zhang, Yongguo Cui
Summary: With the increasing demand for coal resources, coal has been mined in deep coal seams, leading to great risks of coal and gas outburst. Protective coal seam mining, as a safe and effective method for gas control, has been widely used. This study investigated stress-seepage coupling laws and permeability characteristics of a protected coal seam during the process of protective coal seam mining.
NATURAL RESOURCES RESEARCH
(2021)
Article
Mathematics, Interdisciplinary Applications
Shuang Song, Mingkun Pang, Yi Guo, Lei Zhang, Tianjun Zhang, Hongyu Pan
Summary: This study investigates the permeability of crushed coal bodies under pressure by quantitatively considering the particle size distribution using fractal theory. The percolation characteristics and permeability are calculated based on the fractal dimension and porosity. Experimental results show that the migration of fine particles increases the porosity and enhances the permeability properties of the skeleton, causing sudden seepage changes. A fractal-percolation model for crushed coal bodies under pressure is proposed, which provides a solution for determining the grain permeability of crushed coal bodies effectively.
FRACTAL AND FRACTIONAL
(2023)
Article
Mechanics
Ya Meng, Zhiping Li
Summary: This study investigates the gas slippage effect in coal samples with different coalification degrees through helium permeability experiments. The research reveals the characteristics of gas permeability variations in coal samples and the influence of coalification degrees, coal pore structures, and different gases on the gas slippage effect. The study establishes a prediction model for coalbed methane (CBM) well production considering the gas slippage effect and reveals the degree of impact on CBM well productivity.
Article
Chemistry, Multidisciplinary
Lin Zhang, Chengmin Wei, Yao Nie, Ruiying Wang
Summary: The research on active nitrogen injection pressure measurement is of great significance to improve pressure measurement efficiency. Experimental results show that when the injected nitrogen pressure is close to the original coal seam gas pressure, the borehole gas pressure balance time is shorter. A numerical solver for active pressure measurement was developed based on OpenFOAM and C++ language.
Article
Multidisciplinary Sciences
Yunpeng Yang, Zhihui Wen, Leilei Si, Xiangyu Xu
Summary: This study investigated the variation resistivity of electrical parameters of coal samples with different metamorphic grades by applying a self-developed direct current (DC) field. The analysis showed that the internal current of all coal samples increases continuously and tends to be stable gradually after reaching the inflection point at peak. The temperature rise effect on anthracite coal surface lags behind changes of currents running through coal samples.
SCIENTIFIC REPORTS
(2021)
Article
Energy & Fuels
Chenghao Wang, Yuanping Cheng, Liang Wang, Jingyu Jiang, Zhaonan Jiang
Summary: This study established a new method to characterize the seepage pore size distribution under different effective stress conditions. The results showed that the volume reduction of seepage pores presents a logarithmic growth with the increase of confining stress. The size of seepage pores generally ranges from 0.1 to 1.0 mu m, and the volume of seepage pores with sizes ranging from 0.1 to 0.5 mu m always accounts for more than 80% of the total seepage pore volume.
Article
Mechanics
Hu Liu, Guannan Liu, Xutong Zhang, Jiayi Gu, Jingyun Zhu
Summary: After hydraulic fracturing, shale gas is transported to horizontal wells through various media. The study developed a shale multi-scale mining model, considering power-law fracture distribution, porous media fractal theory, and seepage mechanisms in both water and gas phases. The results demonstrated the importance of the degree of hydraulic fracturing, properties of the water phase, and hydraulic fracturing porosity in improving gas production and pore structure evolution.
Article
Mechanics
Yafei Luo, Yongjian Zhu, Fei Huang, Binwei Xia
Summary: This study investigated the nonlinear seepage characteristics of coal under true triaxial stress and found that the characteristics increase with increasing principal stresses and gas pressure gradient. Both the Forchheimer and Izbash equations accurately characterize the nonlinear seepage, but the Forchheimer equation requires more theoretical parameters to measure the degree of nonlinear seepage.
Article
Construction & Building Technology
Alireza Kaboudan, Mahmood Naderi, Majid Amin Afshar
Summary: This study investigated the validity of the Darcy flow model for water penetration into concrete, using a two-dimensional diffusion flow model to predict water penetration. Results showed that water penetration did not follow a Darcy flow model, but could be accurately predicted using optimum diffusion coefficients. Strong correlations were found between permeability parameters, test duration, applied water pressure, and weak correlations between diffusion coefficients and penetrated water volume.
JOURNAL OF BUILDING ENGINEERING
(2021)
Article
Chemistry, Multidisciplinary
Tianyu Xin, Bing Liang, Junguang Wang, Weiji Sun, Yashengnan Sun
Summary: In the process of cyclic loading and unloading, the porosity and permeability of coal samples were investigated, showing exponential decrease with an increase in loading and unloading cycles. Factors such as initial confining pressure and cyclic load amplitude were found to influence the evolution of permeability and pore structure characteristics of coal samples.
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.
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
Energy & Fuels
Jimmy Xuekai Li, Matt Tsang, Ruizhi Zhong, Joan Esterle, Claire Pirona, Mojtaba Rajabi, Zhongwei Chen
Summary: In this paper, advanced machine learning and computer vision techniques were applied to provide a data-driven solution to reduce the subjectivity of Coal Mine Roof Rating (CMRR) calculation. The machine learning methods were used to predict the uniaxial compressive strength (UCS) of roof strata and the computer vision model was adopted to extract core dimensions for rock quality designation (RQD) and fracture spacing calculation. The automatic CMRR values from machine learning models showed a promising correlation with the manually calculated CMRR values, indicating the potential of this approach as an alternative method.
INTERNATIONAL JOURNAL OF COAL GEOLOGY
(2023)
Article
Green & Sustainable Science & Technology
Peibo Li, Jianguo Wang, Wei Liang, Rui Sun
Summary: This study develops an analytical stress model and a seepage-mechanical-damage numerical model to analyze the vertical propagation of I/II mixed fractures in coal-measure superimposed reservoirs. The investigation reveals that hydraulic fracture propagation through the reservoir interface is a process of multi-physical interactions mainly controlled by injection pressure and elastic modulus ratio of adjacent reservoirs.
Article
Chemistry, Multidisciplinary
Rui Sun, Jianguo Wang, Ying Liu
Summary: In this paper, the differential equations of motion for a bus running on different road conditions are established and the entire driving process is mechanically analyzed. The study finds that the bump degree differs on different roads and the rear row is bumpier. The relationship between the speed of the bus and the vertical displacement and acceleration is quantitatively described. Furthermore, the change in vertical displacement and acceleration under different spring stiffness coefficient ratios of the front and rear wheels is analyzed.
APPLIED SCIENCES-BASEL
(2023)
Article
Chemistry, Multidisciplinary
Qi Liu, J. G. Wang, Bowen Hu
Summary: Charge-discharge in a lithium-ion battery can cause adverse reactions and deformations, potentially leading to mechanical fractures. This study proposes a novel binding protective structure that balances lithium-ion permeability and structural stability. Analytical and numerical results show that the binding protective structure has high fracture-proof effectiveness and ion diffusion rate, although it may have lower structural stability compared to other structures.
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)
Article
Energy & Fuels
Rui Sun, Jianguo Wang, Kai Zhang, Fuqing Li, Xiaolei Ding, Qinghua Guo
Summary: This study analytically solves the redistributions of stress and displacement in each layer of a multilayer chamber based on complex variable function theory. A comprehensive parameter is obtained to quickly evaluate the stability of the chamber. The study also explores the role and selection of lining and grouting layers in enhancing the chamber stability. The results show that the chamber stability can be effectively evaluated and enhanced using these analytical solutions and comprehensive parameters.
ENERGY SCIENCE & ENGINEERING
(2023)
Article
Geosciences, Multidisciplinary
Wei Liang, Jianguo Wang, Peibo Li, Chunfai Leung, Sianghuat Goh, Shuxun Sang
Summary: This paper develops a wellbore-reservoir coupling model to explore the interlayer interference during three-gas co-production in a coal-measure superimposed reservoir. The results show that the interlayer interference coefficient in the coal measure decreases with production time and reservoir spacing, but increases with the parameter difference between the coalbed and other reservoirs. Therefore, adjusting the wellbore pressure at the beginning of three-gas co-production can effectively reduce interlayer interference.
NATURAL RESOURCES RESEARCH
(2023)
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)
Article
Energy & Fuels
Chunshan Zheng, Feng Liao, Sheng Xue, Bingyou Jiang, Xuanping Gong, Baiqing Han, Zhongwei Chen
Summary: Enhancing coal permeability by adopting chemical solvents treatment is an effective method to improve coalbed methane production efficiency. This study investigated the changes in coal ultrasonic characteristics, pore structure, and permeability after treatment with different chemical solvents. Results showed that ultrasonic velocity in coal reduces while ultrasonic attenuation coefficient increases after treatment, indicating good development of coal fractures. The porosity and permeability of CS2-treated coal experienced the maximum increase, and the permeability changes obtained from the NMP calculation model were consistent with lab measurements. The results demonstrate that chemical solvents can dissolve molecular substances in coal and improve pore connectivity.
GEOENERGY SCIENCE AND ENGINEERING
(2023)