Fracture propagation characteristics driven by liquid CO₂ BLEVE for coalbed methane recovery

Fracture propagation induced by liquid CO₂ phase transition blasting (LCO₂-PB) is the major reason for the spotty fracturing performance of LCO₂-PB for enhancing coalbed methane (ECBM). Measures to effectively control the fracture propagation are of significant importance for ECBM recovery. Many researches to date have conducted the responses of the fracture propagation upon the CO₂ fracturing under various injection conditions, and some have found that the thermodynamic state of CO₂ can dominate the cracks distribution to some extent. This study therefore investigates the effect of various operated parameters of LCO₂-PB on the fracture propagation alteration of coal seam subjected to the thermodynamic state of CO₂ with different reservoir conditions. A series of fracture process simulations were performed based on the pressure–temperature-phase coupling model, and results indicate that high temperature of CO₂ flow in the fracture process greater fracture expansion; the fracture width decreased around by 66.8 % from smaller smash district to larger one, especially for low CO₂ flow rate; high elastic modulus and the temperature of coal seam favors greater length reduction and extensive crack connection, and as temperature of CO₂ induces the interlaced fractures earlier formation in the higher reservoir temperature.