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A Uniaxial Compression Experiment with CO2-Bearing Coal Using a Visualized and Constant-Volume Gas-Solid Coupling Test System
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Simulation study on dynamic characteristics of gas diffusion in coal under nitrogen injection
1School of Emergency Management and Safety Engineering, China University of Mining and Technology, Beijing, 100083, China. yxzhs163@163.com.
Scientific Reports
|November 7, 2022
Summary
Nitrogen (N₂) injection enhances methane (CH₄) desorption from coal seams by displacing adsorbed CH₄ and promoting diffusion. Higher N₂ pressure and coal moisture content increase methane release, aiding extraction.
Area of Science:
- Geochemistry and Petroleum Engineering
- Materials Science and Engineering
Background:
- Understanding methane (CH₄) desorption mechanisms in coal seams is crucial for safe and efficient extraction.
- Inert gas injection, specifically nitrogen (N₂), is explored as a method to enhance methane recovery from coal beds.
Purpose of the Study:
- To elucidate the mechanism of methane desorption induced by nitrogen injection in coal seams.
- To investigate the influence of nitrogen pressure, temperature, and water content on methane desorption dynamics.
Main Methods:
- Utilized Giant Canonical ensemble Monte Carlo (GCMC) and Molecular Dynamics (MD) simulations.
- Employed a molecular structure model of wiser bituminous coal for simulation studies.
Main Results:
- Methane and nitrogen adsorption isotherms in coal models follow the Langmuir model, with higher adsorption capacity for CH₄ than N₂.
- Increased nitrogen injection pressure and temperature significantly enhance methane desorption.
- Nitrogen competes with methane for adsorption sites, facilitating CH₄ displacement; higher N₂ pressure amplifies CH₄ diffusion.
Conclusions:
- Nitrogen injection promotes methane desorption through competitive adsorption (gas displacement) and enhanced diffusion.
- Coal seam water content positively influences methane desorption.
- Findings offer theoretical support for optimizing methane extraction technologies in goaf areas.
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