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Multicomponent Competitive Adsorption of CH4 with Injected Superheated CO2, N2, and H2O in Lignite
Xiao Zhang1, Jupeng Tang1,2, Fei Wang3
1School of Civil Engineering, Liaoning Technical University, Fuxin, Liaoning 123000, China.
ACS Omega
|July 24, 2026
Summary
This study explores gas injection for coalbed methane (CBM) recovery. Low-pressure water injection is most effective, while specific ratios of nitrogen and carbon dioxide optimize methane displacement.
Area of Science:
- Geochemistry
- Petroleum Engineering
- Computational Chemistry
Background:
- Enhancing coalbed methane (CBM) recovery requires understanding competitive adsorption between injected gases and methane (CH4).
- Existing research has not systematically addressed the competitive adsorption of water (H2O) with CH4 or the behavior of superheated gases with CH4.
Purpose of the Study:
- To investigate the competitive adsorption of H2O with CH4 and superheated gases (N2, CO2) with CH4 in lignite.
- To determine optimal conditions for gas injection to maximize CBM recovery.
Main Methods:
- Construction of a lignite supercell model.
- Grand canonical Monte Carlo (GCMC) and molecular dynamics (MD) simulations at 473.15 K and 0-10 MPa.
- Analysis of atomic density and potential energy to evaluate displacement limits and critical compositions.
Main Results:
- In the CH4/H2O system, selectivity increases with pressure; low-pressure H2O injection (<3 MPa) is most advantageous.
- In the N2/CH4/CO2 ternary system, a CH4 molar fraction of 30% acts as a turning point for competitive adsorption.
- Displacement limits are evaluated using atomic density and potential energy peaks, providing quantitative insights.
Conclusions:
- Low-pressure water injection is beneficial for CBM recovery, with diminishing returns at higher pressures.
- A critical CH4 molar fraction of 30% in ternary gas mixtures dictates the effectiveness of displacement.
- This research provides a quantitative basis for optimizing gas injection strategies to enhance CBM recovery.
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