Numerical study of hydraulic fracturing on single-hole shale under fluid–solid coupling

To investigate the hydraulic fracture extension pattern of single-hole shale during hydraulic fracturing under fluid–solid coupling, this paper utilizes seepage–stress–damage coupling software to establish a mechanical model of hydraulic fracture initiation in single-hole shale under different pore pressure increments in seven groups. The results reveal that under the action of a single-hole pressure gradient, shale is destabilized and destroyed by shale instability after two damage degradations under the coupled action of hydraulic and peripheral pressures, the fracture network is fully developed, and the stress decreases sharply. The final damage pattern of the hydraulic fracture distribution is categorized into two types: “X” and “Y”. The hydraulic gradient under hydraulic fracturing is distributed as a closed-loop strip, the hydraulic gradient decreases layer by layer from the inside to the outside, the seepage field and stress field interact with each other, and the pore water pressure and stress are coupled with each other, resulting in increasingly complete fracture development.