A Peridynamics Model for the Propagation of Hydraulic Fractures in Naturally Fractured Reservoirs

Abstract

Summary A novel and fully coupled hydraulic-fracturing model derived from a nonlocal continuum theory of peridynamics is presented and applied to the hydraulic-fracture (HF) propagation problem. It is shown that this modeling approach provides an alternative to finite-element and finite-volume methods for solving poroelastic and fracture-propagation problems. In this paper, we specifically investigate the interaction between an HF and natural fractures (NFs). The peridynamics model presented here allows us to simulate the propagation of multiple, nonplanar, interacting fractures and provides a novel approach to simulate the interaction between HFs and NFs. The model predictions in two dimensions have been validated by reproducing published experimental results where the interaction between an HF and an NF is controlled by the principal-stress contrast and the approach angle. A detailed parametric study involving poroelasticity and mechanical properties of the rock is performed to understand why an HF becomes arrested or crosses an NF. This analysis reveals that poroelasticity, resulting from high fracture-fluid leakoff, has a dominant influence on the interaction between an HF and an NF. In addition, the fracture toughness of the rock, the toughness of the NF, and the shear strength of the NF also affect the interaction between an HF and an NF. We also investigate the interaction of multiple completing fractures with NFs in two dimensions and demonstrate the applicability of the approach to simulate complex fracture networks on a field scale. Finally, the 3D interaction study elucidated that the height of the NF, the position of the NF, and the opening resistance of the NF all have a significant effect on the 3D interaction between an HF and an NF.