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.