A Uniaxial Compression Experiment with CO2-Bearing Coal Using a Visualized and Constant-Volume Gas-Solid Coupling...

Area of Science:

• Geotechnical Engineering
• Environmental Science
• Materials Science

Background:

• Carbon dioxide (CO2) injection into coal seams is crucial for mitigating atmospheric greenhouse gases and improving coalbed methane (CBM) extraction.
• Understanding the impact of CO2 sorption on coal's physical and mechanical properties is essential for effective carbon capture, utilization, and storage (CCUS) and CBM recovery operations.

Purpose of the Study:

• To investigate the influence of CO2 sorption on the physical and mechanical properties of coal using a novel visualized, constant-volume gas-solid coupling system.
• To analyze the fracture evolution of coal under varying CO2 pressures using fractal geometry.

Main Methods:

• Development and application of a visualized, constant-volume gas-solid coupling system for uniaxial compression experiments on coal briquettes.
• Real-time monitoring of coal briquette surface deformation and fracture evolution under different CO2 pressures.
• Application of fractal geometry methods to quantify fracture characteristics.

Main Results:

• CO2 sorption significantly reduces the peak strength and elastic modulus of coal briquettes.
• Fracture evolution in coal under failure conditions exhibits fractal characteristics.
• Coal strength, elastic modulus, and fractal dimension show a non-linear correlation with CO2 pressure.

Conclusions:

• The visualized gas-solid coupling system provides a valuable platform for studying multifield coupling effects in rock mechanics.
• CO2 sorption negatively impacts coal's mechanical integrity, with effects being pressure-dependent.
• Fractal analysis offers a quantitative approach to understanding coal fracture behavior under CO2 injection.