The Influence Law and Mechanism of CO2 Injection Pressure on Coal Rock Pore-Fracture Characteristics

In order to clarify the characteristics of coal rock pore fracture changes after CO2 gas injection into coal seams, the Dafosi coalfield in Binchang mining area was taken as the research object. The changes in CT scanning surface, pseudo color, grayscale mean, and porosity of coal and rock samples were studied under different CO2 injection pressures. Through CT scanning experiments, combined with ORS visual and Matlab software. The main reasons for the changes in pore fracture characteristics of coal and rock after injecting CO2 gas were studied from three aspects: compressive deformation of coal and rock, crack width, and number of cracks. The experimental results showed that, as the injection pressure of CO2 gas increases, the color of coal rock CT scan images and pseudo color images becomes lighter, the mean gray level increases, and the porosity decreases; The compression deformation of coal rock is not the main reason for the changes in the characteristics of coal rock pores and fractures; The more CO2 gas is adsorbed by coal and rock, the narrower the cracks gradually, and the number of pores and fractures decreases. CO2 adsorption is the main reason for the decrease in porosity of coal and rock. The research results provide a technical boundary reference for the development of coalbed methane injection CO2.