Numerical simulation of fluid-driven fracturing in orthotropic poroelastic media based on a peridynamics-finite element coupling approach

In the present manuscript a peridynamics-finite element coupling approach proposed by Sun and Fish (2021) is generalized to simulate fluid-driven fracturing in orthotropic poroelastic media. For this purpose, an orthotropic non-ordinary state-based peridynamics (NOSBPD) model with a bond micromodulus and a critical energy density continuously varying with the bond orientation is proposed. The governing equations of the coupled system involving an orthotropic NOSBPD model aimed at capturing the solid fracture and finite element model (FEM) aimed at modeling fluid flow with an anisotropic permeability tensor is derived. Both the m-convergence and delta-convergence studies are performed to determine appropriate discretization parameters for the proposed orthotropic NOSBPD model. The fracture propagation in the compact tension test with different material ori-entations is simulated for model verification. The effects of the elasticity and permeability anisotropy, injection rates as well as the existences of multiple fractures and natural fractures have been found to have a significant effect on the fluid-driven fracture propagation in orthotropic poroelastic media. The fracture seems to deviate from the initial notch direction under different material angles, and this trend becomes more prominent with reduction of the elastic modulus and the fracture release rate perpendicular to the bending plane. The perme-ability anisotropy affects the fluid pattern and the fracture propagation length. The rapid injection rate gives rise to a wider damage zone and a more diffuse pore pressure field.

Automated summary

In this paper, a peridynamics-finite element coupling approach is generalized to simulate fluid-driven fracturing in orthotropic poroelastic media. A non-ordinary state-based peridynamics model with orthotropic properties is proposed, and the governing equations of the coupled system involving both the peridynamics model and finite element model are derived. The effects of material anisotropy, injection rates, and the presence of multiple fractures on fluid-driven fracture propagation are investigated. The study reveals the significance of elasticity and permeability anisotropy, injection rates, and fracture characteristics in orthotropic poroelastic media.