Coupled adsorption-hydro-thermo-mechanical-chemical modeling for CO2 sequestration and well production during CO2-ECBM

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

“…Liu et al 27 established a THMC model for CO 2 -ECBM, taking into account the dissolution of minerals in water and the geochemical reactions of various cations and anions. The THMC coupling relationship is shown in Figure 36.…”

“…Coupling relations of the THMC model established by Liu et al This figure was reproduced with permission from ref . Copyright 2023 Elsevier.…”

“…CH 4 production and CO 2 storage calculated by Liu et al This figure was reproduced with permission from ref . Copyright 2023 Elsevier.…”

“…24,25 The fluid transport in CO 2 -ECBM recovery is illustrated in Figure 1. In comparison to the primary coalbed methane recovery, the process of CO 2 -ECBM is much more complex, 26,27 involving thermo−hydro−mechanical−chemical couplings controlling CH 4 production and CO 2 sequestration. 28,29 Scholars discover that rising the temperature of the gas reservoir will accelerate the migration of gas molecules, leading to underestimation of the CH 4 production if the thermal effect is ignored.…”

“…(2) CO 2 displaces CH 4 on the adsorption site, obeying the extended Langmuir equation. − (3) Displaced CH 4 migrates in the opposite direction, diffusing from the coal matrix to fractures and then moving toward the producing well, satisfying Fick’s law and Darcy’s law accordingly. , The fluid transport in CO 2 -ECBM recovery is illustrated in Figure . In comparison to the primary coalbed methane recovery, the process of CO 2 -ECBM is much more complex, , involving thermo–hydro–mechanical–chemical couplings controlling CH 4 production and CO 2 sequestration. , Scholars discover that rising the temperature of the gas reservoir will accelerate the migration of gas molecules, leading to underestimation of the CH 4 production if the thermal effect is ignored . The formation water will block the transport channel and hinder gas migration in the fracture, resulting in overestimation of CH 4 production if the water effect is ignored. , The change in gas adsorption/desorption and temperature will cause expansion/contraction of the coal matrix, dominating the evolution of key parameters: porosity and permeability. − Furthermore, the injected parameters, e.g., injection pressure, borehole spacing, and injection time, will alter the CH 4 production, CO 2 sequestration, and change rate of permeability. , To weaken the effect of excessive swelling of the coal matrix, reduce injection difficulty, and improve gas recovery, the injection of mixed gas (N 2 /CO 2 ) with an initial low concentration of CO 2 is proposed .…”