Distribution Relationship of Pore Pressure and Matrix Stress during Hydraulic Fracturing

When hydraulic fracturing is utilized to eliminate coal and gas outbursts and rockburst in dynamic disaster coal-rock formations, the stress disturbance of hydraulic fracturing may have negative effects such as causing local stress concentration. The method of combining physical model experiments and numerical simulations is adopted to study the distribution relationship of pore pressure and matrix stress during hydraulic fracturing. The research results show that the pore pressure and matrix stress gradually attenuate farther away from the hydraulic fracture in the process of hydraulic fracturing. The attenuation rate of matrix stress is less than that of pore pressure. The range of the matrix stress disturbance zone is larger than the range of the pore pressure disturbance zone. With the increase of pumping time, the increasing speed of the matrix stress disturbance zone is greater than that of the pore pressure disturbance zone. This indicates that the squeezing force on both sides of the hydraulic fracture increases correspondingly with the increase in crack opening, which causes the range and magnitude of the matrix stress disturbance zone to increase gradually. The stress disturbance zone around the hydraulic fracture includes the pore pressure disturbance zone and the matrix stress disturbance zone. In the pore pressure disturbance zone, the pore pressure and the matrix stress increase and interact at the same time, which together lead to the deformation and failure of coal and rock mass. The relationship between the pore pressure and the matrix stress in this region conforms to the natural logarithmic attenuation relationship. Outside the pore pressure disturbance zone, the deformation and failure of coal and rock mass are mainly caused by the matrix stress effect.