Poromechanical Modeling and Numerical Simulation of Hydraulic Fracture Propagation

Hydraulic fracturing (HF) is an important technique for enhancing the permeability of petroleum and gas reservoirs. To understand the coupling response mechanism of fluid pressure and in situ stress during the expansion of hydraulic fractures-based on the theory of the fluid flow of seepage porous media and damage mechanics-a poromechanical model of hydraulic fracture propagation is proposed and the finite element method (FEM) numerical weak coupling calculation method of hydraulic fracturing is realized. First, the effect of the coupling stress field is described by introducing the β value of the amount of pore volume that varies, resulting from internal pressure per unit of fluid internal, and the coupling calculation method of the pore pressure-effective stress-element damage-pore pressure expansion coefficient is formulated. Second, based on the concept of damage localization, a calculation method for the hydraulic fracture opening equation is proposed, and then the element damage-hydraulic fracture opening-permeability tensor-pore pressure field calculation cycle is established. The model indicates four stages of fracture propagation: I, fracture nucleation, II, kinetic propagation, III, steady propagation, and IV, propagation termination. Finally, as an example, a numerical simulation of three-dimension hydraulic fracturing is performed. In comparison to previous research, the morphology of the fracture zone and the fluid pressure contour of the horizontal section are approximately ellipses, which verify the feasibility of the weak coupling calculation method; the fracture parameters verify its accuracy, which include the length, width, and fluid pressure.