Impact of injection pressure on CO2–enhanced coalbed methane recovery considering mass transfer between coal fracture and matrix

Yin, Guangzhi; Deng, Bangming; Li, Minghui; Zhang, Dongming; Wang, Weizhong; Li, Wenpu; Shang, Delei

doi:10.1016/j.fuel.2017.02.011

Cited by 65 publications

(36 citation statements)

References 24 publications

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“…The mass balance equation of the each component of gas (CH 4 /CO 2 ) can be expressed for a static medium, that incorporates the convective and dispersion modes of transport but involves the interchange between adsorbed gas and free gas as [10,21,42,43,51,52]:…”

Section: Binary Gas Transportmentioning

confidence: 99%

“…where the gas content of a component gas i is m i which includes both the free-phase and adsorbed gas; v g is the vector of convective velocity; ρ i is the gas density in the matrix or the fracture; D i is the diffusion coefficient; m iF represents the gas content of the free state in the matrix or the fracture; Q si is the gas source or sink. The mass of each component of gas (CH 4 /CO 2 ) present in a unit of the matrix and fracture system can be expressed as follows [43,52].…”

Section: Binary Gas Transportmentioning

confidence: 99%

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Reservoir Permeability Evolution during the Process of CO2-Enhanced Coalbed Methane Recovery

Wang

Jiang

et al. 2018

Energies

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In this study, we have built a dual porosity/permeability model through accurately expressing the volumetric strain of matrix and fracture from a three-dimensional method which aims to reveal the reservoir permeability evolution during the process of CO2-enhanced coalbed methane (CO2-ECBM) recovery. This model has accommodated the key competing processes of mechanical deformation and adsorption/desorption induced swelling/shrinkage, and it also considered the effect of fracture aperture and effective stress difference between each medium (fracture and matrix). We then numerically solve the permeability model using a group of multi-field coupling equations with the finite element method (FEM) to understand how permeability evolves temporally and spatially. We further conduct multifaceted analyses to reveal that permeability evolution near the wells is the most dramatic. This study shows that the farther away from the well, the gentler the evolution of permeability. The evolution of reservoir permeability near the injection well (IW) and the production well (PW) are very different, due to the combined effects of effective stress changes and gas adsorption and desorption. Furthermore, adsorption is the main controlling factor for the change of permeability for regions near the IW, while the change in effective stress is the main cause for the change in permeability near the PW. Increasing the injection pressure of CO2 will cause the reservoir permeability to evolve more quickly and dynamically.

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Section: Binary Gas Transportmentioning

confidence: 99%

Section: Binary Gas Transportmentioning

confidence: 99%

Reservoir Permeability Evolution during the Process of CO2-Enhanced Coalbed Methane Recovery

Wang

Jiang

et al. 2018

Energies

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“…Injection of foreign gases into coal seam is considered an effective method to enhance gas drainage . This process expedites the gas transport by competitive sorption and sweeping effects and maintaining pressure gradient between coal seam and borehole . The gases commonly used as injectants are nitrogen (N 2 ), carbon dioxide (CO 2 ), and gas mixture (N 2 /CO 2 ) .…”

Section: Introductionmentioning

confidence: 99%

Numerical investigation of flue gas injection enhanced underground coal seam gas drainage

Huo

Jing

Fan

et al. 2019

Energy Science & Engineering

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Coal seam with low permeability is widely distributed in China. Injection of flue gas (N2:CO2 = 0.85:0.15) is an effective approach to improve coal seam gas drainage efficiency. This process relates complex responses among ternary gases (CH4, CO2, and N2) competitive sorption on coals, gas diffusion, gas‐water migration by means of two‐phase flow, and coal deformation. In this paper, an improved hydraulic‐mechanical model coupling above interactions is established for flue gas injection enhanced gas drainage. This model is used to simulate flue gas enhanced drainage by finite element method. The sensitivity analyses of key factors are made to recovery a better understanding on the processes controlling flue gas enhanced drainage. Results show that the flue gas enhanced drainage can indeed improve the efficiency of gas extraction and reduce the gas pressure to the required value in a shorter duration. Due to the competitive adsorption and gas sweeping effect of injected flue gas, CH4 is driven toward drainage borehole, and CH4 pressure and content near the injection borehole decrease faster than that near the drainage borehole. The peak CH4 pressure laterally moves from the injection borehole to the drainage borehole. Higher injection pressure, initial permeability, and smaller sorption affinity ratios may lead to greater CH4 production rate at early drainage stage, but smaller CH4 production rate at late stage. The factors controlling the behavior of flue gas enhanced drainage are initial permeability, injection pressure, and sorption affinity ratios in order. This work offers useful framework to investigate important technical challenges associated with enhanced mine gas drainage, as well as unconventional gas development.

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“…e pore structure of the coal seam determines the law of gas adsorption/desorption, diffusion, seepage, and mass transfer between the coal fracture and matrix [13,14]. e hydraulic-mechanical coupling model in the coal seam can fully reflect the relationship between gas seepage and coal deformation and capture the evolution of coal porosity and permeability [15]. For gas migration in coal seams, many gas-solid coupling models have been put forward.…”

Section: Introductionmentioning

confidence: 99%

Hydraulic‐Mechanical Coupling Model with Dual‐Porosity Dual‐Permeability for Anisotropy Coal Seams and Its Application in Mine Gas Extraction

Huo

Jing

et al. 2019

Advances in Civil Engineering

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The parameters of pore-fracture structure and permeability have a controlling effect on the behaviors of gas adsorption/desorption and transportation in coal reservoir. A mathematic model for coal seams is of great significance to evaluate the mass migration within the coal fracture-matrix system. In this paper, the hydraulic-mechanical coupling model considering both dual-porosity dual-permeability and anisotropy characteristics is first established by using the methods of theoretical analysis, nuclear magnetic resonance (NMR) test, and numerical simulation. Then, this model is applied to simulate the gas migration characteristics of No. 3 coal seam in Changping Mine, China. Results show that the pore structure of No. 3 coal seam is characterized by small radius of pores and pore throats, which is determined by the NMR test, verifying the dual-permeability dual-porosity of coal seams. Both matrix permeability and fracture permeability increase approximately linearly with the process of mine gas extraction. The increased magnitude of the matrix permeability is greater than that of the fracture permeability. The permeability is inversely proportional to the anisotropy coefficient. The pressure gradient within the coal matrix and fracture increases first and then decreases with the extraction time. This pressure gradient is proportional to the anisotropy coefficient at the early stage of extraction and is inversely proportional to the anisotropy coefficient at the later stage. The seepage and diffusion flux are proportional to the anisotropy coefficient. The proportion of matrix-to-fracture seepage flux to the total flux increases first and then decreases to a certain value. The proposed model provides a guide for accurate designation of gas extraction from coal seams.

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Impact of injection pressure on CO2–enhanced coalbed methane recovery considering mass transfer between coal fracture and matrix

Cited by 65 publications

References 24 publications

Reservoir Permeability Evolution during the Process of CO2-Enhanced Coalbed Methane Recovery

Reservoir Permeability Evolution during the Process of CO2-Enhanced Coalbed Methane Recovery

Numerical investigation of flue gas injection enhanced underground coal seam gas drainage

Hydraulic‐Mechanical Coupling Model with Dual‐Porosity Dual‐Permeability for Anisotropy Coal Seams and Its Application in Mine Gas Extraction

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