CO2 injection and storage in porous rocks: coupled geomechanical yielding below failure threshold and permeability evolution

Abstract

Summary With the increasing demand for CO2 storage into the subsurface, it is important to recognize that target storage formations like saline aquifers can vary significantly in their geomechanical and hydraulic properties. Consequently, modelling of CO2 injection requires the selection of the most appropriate constitutive material model for the best possible representation of the material response. The authors focus on modelling the geomechanical behaviour of the reservoir material, coupled with multi-phase flow solution of CO2 injection into a saline saturated medium. It is proposed to use the SR3 critical state material model which considers a direct link between strength-volume-permeability that evolves during the simulation. Furthermore the material is considered to yield prior to reaching a peak strength in agreement with experimental observations. Multi-phase flow coupled to advanced geomechanics provides a holistic approach to modelling CO2 injection into sandstone reservoirs. The resulting injection pressures, CO2 migration extent and patterns, formation dilation and strength reduction are compared for a range of in-situ porosities and incremental material model enhancements. This work aims to demonstrate a numerical modelling framework to aid in the understanding of geomechanical responses to CO2 injection for safe and efficient deployment.