Research on Enhancing Gas Extraction Efficiency through CO₂ Gas Fracturing in Outburst-Prone Coal Seams

Area of Science:

• Mining Engineering
• Geological Engineering
• Safety Science

Background:

• Coal mine gas disasters pose a significant global safety risk.
• Efficient gas control technologies are crucial for mining operations.
• Existing dense-borehole gas extraction proved insufficient for outburst-prone seams at Pingshu Coal Mine.

Purpose of the Study:

• To evaluate the efficacy of CO2 gas fracturing (CO2-Frac) in outburst-prone coal seams.
• To compare the performance of single-hole versus dual-hole CO2-Frac configurations.
• To validate CO2-Frac as a viable safety measure in challenging mining environments.

Main Methods:

• Field-scale CO2-Frac project at Pingshu Coal Mine.
• Fracture propagation experiments with single-hole and dual-hole setups.
• On-site gas extraction tests to assess effectiveness.

Main Results:

• Dual-hole CO2-Frac expanded the fractured and pressure relief area to 26.82 m², a 220% increase over single-hole.
• Gas extraction flow rate improved 7.3-fold (0.026 to 0.216 m³/min per 100m borehole).
• Gas extraction period reduced from 20 to 6 days.

Conclusions:

• Dual-hole CO2-Frac is highly effective for gas control and safety in outburst-prone coal seams.
• The technique offers significant improvements in fractured area and gas extraction efficiency.
• Provides theoretical and practical validation for similar mining applications.