Multiscale simulation of injection-induced fracture slip and wing-crack propagation in poroelastic media

TL;DR

This paper develops a multiscale mathematical model and numerical method to simulate how fluid injection induces fracture slip and wing-crack propagation in poroelastic media, capturing complex hydraulic-mechanical interactions.

Contribution

It introduces a coupled multiscale approach that models fracture shearing and propagation under fluid injection, addressing numerical challenges of scale and material discontinuity.

Findings

Fracture shearing is linked to fluid injection and fracture propagation.

The model captures interactions between multiple fractures.

Simulations demonstrate the influence of fluid pressure on fracture growth.

Abstract

In fractured poroelastic media under high differential stress, the shearing of fractures and faults and the corresponding propagation of wing cracks can be induced by fluid injection. Focusing on low-pressure stimulation with fluid pressures below the minimum principal stress but above the threshold required to overcome the fracture's frictional resistance to slip, this paper presents a mathematical model and a numerical solution approach for coupling fluid flow with fracture shearing and propagation. Numerical challenges are related to the strong coupling between hydraulic and mechanical processes, the material discontinuity the fractures represent in the medium, the wide range of spatial scales involved, and the strong effect that fracture deformation and propagation have on the physical processes. The solution approach is based on a multiscale strategy. In the macroscale model, flow in and poroelastic deformation of the matrix are coupled with the flow in the fractures and fracture contact mechanics, allowing fractures to frictionally slide. Fracture propagation is handled at the microscale, where the maximum tangential stress criterion triggers the propagation of fractures, and Paris' law governs the fracture growth processes. Simulations show how the shearing of a fracture due to fluid injection is linked to fracture propagation, including cases with hydraulically and mechanically interacting fractures.