Numerical analysis of matrix swelling and its effect on microstructure of digital coal and its associated permeability during CO2-ECBM process based on X-ray CT data

Recent Advances and Perspectives of CO2-Enhanced Coalbed Methane: Experimental, Modeling, and Technological Development

“…The connected fractures keep stretching in coal, and the aperture of the fractures gradually narrows. Matrix swelling leads to a gradual decrease in coal body permeability and hinders fluid transport . To address the issue that CO 2 injection reduces coalbed permeability and increases well injection capacity, Zhang et al provided the first observational evidence that injecting nitrogen (N 2 ) can improve coal seam permeability by reopening fractures closed by CO 2 adsorption-induced coal swelling through in situ simultaneous X-ray microtomography.…”

“…X-ray CT scanning system: (a) preparation of the sample, (b) imaging system components, and (c) typical two-dimensional (2D) CT slices. This figure was reproduced with permission from ref . Copyright 2022 Elsevier.…”

“…Image processing flow diagram: (a) original CT section, (b) median filtering processing, (c) threshold selection, and (d) selection of the representative elementary volume (REV). This figure was reproduced with permission from ref . Copyright 2022 Elsevier.…”

“…7−9 Injection of CO 2 has been implemented to coal seams to both enhance CH 4 recovery and reduce CO 2 emission. 10,11 Although the cost of carbon dioxide (CO 2 )enhanced coalbed methane recovery (CO 2 -ECBM) is higher than that of depleted CBM, the benefits of increasing CH 4 production and reducing greenhouse gas emissions from CO 2 -ECBM are incalculable. 12, 13 CO 2 injection was proposed to the depleted oil reservoirs for enhancing the remaining oil recovery (EOR).…”

“…To control global warming and achieve the carbon-neutrality goal, environmentally friendly energy resources have gained more attention in recent decades. , Coalbed methane (CBM, mainly CH 4 ) is considered as a potential clean energy source, and redundant mine gas may cause coal and gas outburst and gas explosion disasters, resulting in casualties and equipment damage in underground coal mining. − Natural depletion of the gas reservior is a common method for CBM recovery but fails in a low recovery ratio, especially in low-permeability reserviors. − Injection of CO 2 has been implemented to coal seams to both enhance CH 4 recovery and reduce CO 2 emission. , Although the cost of carbon dioxide (CO 2 )-enhanced coalbed methane recovery (CO 2 -ECBM) is higher than that of depleted CBM, the benefits of increasing CH 4 production and reducing greenhouse gas emissions from CO 2 -ECBM are incalculable. , …”