Numerical simulation research on failure law of surrounding rock in coalbed methane well

The entire process of fracturing at different sections, were namely 1-1(wellhead), 2-2(well middle), 3-3(well bottom), was simulated to study the failure law of surrounding rock at different depths. The failure mechanics of borehole rock mass was analysed using Realistic Failure Process Analysis (RFPA) software. The results showed that as the depth of wells continues to deepen, the crack propagation was restrained relatively by inhomogeneous materials in rock mass. In addition, with the increase of inhomogeneous materials in the surrounding rock, the brittle of rock and peak strength of the fracture gradually increase. The entire process of rock failure was corresponded to three stages, namely damage initiation, restriction propagation and rock failure. As the depth of wells deepens, the steps in damage initiation gradually decreased compared with the steps in restriction propagation stage. As the confining pressure continues to increase, the accumulated energies in the rock mass reached the peak strength of the crack, it would immediately violently crack.