3D Simulation of Mixed-Mode Poroelastic Fracture Propagation for Reservoir Stimulation

摘要

The paper presents three-dimensional numerical model for the multiple fracture propagation in the poroelastic reservoirs. The simulator model is developed based on the fully-coupled 3D poroelastic displacement discontinuity method for the hydro-mechanical response of the reservoir rocks and the linear elastic fracture mechanics for the fracture propagation. The reservoir rock mass is assumed homogenous and isotropic with constant poroelastic physical properties. The mixed-mode fracture propagation is analyzed using crack-tip opening displacement approach. Details of mathematical formulations and methodology for numerical implementation are presented first. Then, the numerical model is verified using analytical solution for a pressurized penny-shaped fracture. Finally, numerical examples for the fluid injection into a cluster of natural fractures and simultaneous propagation of pressurized multiple fractures in Westerly Granite are presented. The results demonstrate that along with the rock properties and the in-situ stress conditions, the "stress shadowing" effect which mainly depends on the spatial interval between the fractures plays a critical role in the multiple fracture propagation. Also, the simulation demonstrated that mixed-mode propagation can occur under influence of "stress shadowing".