Targeted Stimulation Effects of CS₂ Extraction on Methane Desorption in Coal

Area of Science:

• Geochemistry
• Petroleum Engineering
• Physical Chemistry

Background:

• Carbon disulfide (CS₂) is known to stimulate coal macromolecular and pore structures.
• Understanding methane desorption characteristics after CS₂ extraction is crucial for optimizing coalbed methane (CBM) recovery.
• Previous studies have not fully explored the impact of CS₂ extraction on methane desorption dynamics.

Purpose of the Study:

• To investigate the effect of CS₂ extraction on methane desorption characteristics in coal.
• To elucidate the underlying stimulation mechanism of CS₂ extraction on desorption dynamics.
• To provide a theoretical basis for utilizing CS₂ extraction to enhance CBM production.

Main Methods:

• Isothermal adsorption experiments were conducted on coal samples.
• Desorption stage theory was applied to analyze the changes in methane release.
• Key desorption parameters were measured and compared before and after CS₂ extraction.

Main Results:

• CS₂ extraction weakened adsorption and enhanced desorption, indicated by decreased Langmuir constants (a and b).
• Desorption stages were altered, with Stage II (slow desorption) and Stage III (fast desorption) expanding, and Stage IV (sensitive desorption) shortening.
• Critical desorption pressure (P_cd), gas saturation (β), effective pressure drop (P_e), and effective desorption quantity (V_e) increased, signifying easier desorption conditions and higher desorption capacity.

Conclusions:

• CS₂ extraction effectively lowers the critical conditions for methane desorption and enhances overall desorption capacity.
• The study reveals that CS₂ extraction promotes the conversion of adsorbed gas to free gas, extending the effective production period.
• Findings support the application of CS₂ extraction as a viable method to modify desorption characteristics and boost CBM recovery.