A Parallelized 3D Geomechanical Solver for Fluid-induced Fault Slip in Poroelastic Media

TL;DR

This paper introduces a parallelized, fully implicit 3D geomechanical solver that models fluid-induced fault slip in poroelastic media, validated against analytical solutions and applied to CO2 injection scenarios.

Contribution

It presents a novel finite-element based, parallel solver capable of accurately modeling fault slip and fluid flow in fractured reservoirs with explicit fracture representation.

Findings

Successfully reproduces fault slip due to fluid injection

Validates model accuracy against analytical solutions

Demonstrates application to CO2 storage scenario

Abstract

We present a fully implicit formulation of coupled fluid flow and geomechanics for fluid injection/withdrawal in fractured reservoirs in the context of CO2storage. Utilizing a Galerkin finite-element approach, both flow and poroelasticity equations are discretized on a shared three-dimensional mesh. The fluid flow is assumed to be single-phase. The hydraulic behaviour of fractures is represented through a double-nodes flow element, which allows to efficiently model longitudinal and transversal fracture permeabilities. In addressing the mechanical subproblem, fractures are explicitly modelled using cohesive elements to account for contact, friction and opening phenomena. The nonlinear set of equations is solved implicitly through an iterative partitioned conjugate gradient procedure, extending its traditional application to continuous problems to those involving explicit discontinuities such as faults and fractures. The model's accuracy is verified against analytical solutions for different geomechanical problems, notably for the growth of a frictional slip rupture along a fault due to fluid injection. Such a particularly challenging benchmark for a critically stressed fault is here reproduced for the first time by a finite-element based scheme. The capabilities of the developed parallel solver are then illustrated through a scenario involving CO2 injection into a faulted aquifer. The original solver code, tutorials, and data visualization routines are publicly accessible.