Modeling of coupled deformation and permeability evolution during fault reactivation induced by deep underground injection of CO2

Abstract

The interaction between mechanical deformation and fluid flow in fault zones gives rise to a host of coupled hydromechanical processes fundamental to fault instability, induced seismicity, and associated fluid migration. In this paper, we discuss these coupled processes in general and describe three modeling approaches that have been considered to analyze fluid flow and stress coupling in fault-instability processes. First, fault hydromechanical models were tested to investigate fault behavior using different mechanical modeling approaches, including slip interface and finite thickness elements with isotropic or anisotropic elasto-plastic constitutive models. The results of this investigation showed that fault hydromechanical behavior can be appropriately represented with the least complex alternative, using a finite thickness element and isotropic plasticity. We utilized this pragmatic approach coupled with a strain-permeability model to study hydromechanical effects on fault instability during deep underground injection of CO 2 . We demonstrated how such a modeling approach can be applied to determine the likelihood of fault reactivation and to estimate the associated loss of CO 2 from the injection zone. It is shown that shearenhanced permeability initiated where the fault intersects the injection zone plays an important role in propagating fault instability and permeability enhancement through the overlying caprock.

The Geomechanics of CO2 Storage in Deep Sedimentary Formations

“…Thus, it is very difficult to predict how much fault permeability will change in the case of an injectioninduced fault reaction. However, fault permeability could be subject of sensitivity studies and potential permeability changes could perhaps be bounded using fault permeability models (e.g., Cappa and Rutqvist 2011a;Seyedi et al 2011) and to investigate potential consequence, should a fault be reactivated.…”

Exploring the concept of compressed air energy storage (CAES) in lined rock caverns at shallow depth: A modeling study of air tightness and energy balance

“…TOUGH-FLAC has previously been applied to a wide range of problems involving coupled multiphase fluid flow, heat transport, and geomechanical processes, including geologic carbon sequestration [13,14], geothermal energy production from steam dominated geothermal reservoirs [15], and thermally driven coupled processes associated with underground excavations at temperatures above boiling [16].…”

Volume-Based Modelling of Fault Reactivation in Porous Media Using a Visco-Elastic Proxy Model

“…It ranges from 3 up to 25 for consolidated geologic materials (Wong et al 1997;David et al 1994). Consistent with Cappa and Rutqvist (2011) and Rutqvist et al (2013), we use a value of n = 15 for our simulations.…”

“…For this purpose, two simulators can be coupled, such as TOUGH2 and Code_Aster by Rohmer and Seyedi (2010) or TOUGH2 and FLAC3D by , Cappa and Rutqvist (2011). The latter combination has recently been expanded towards the modelling of fault reactivation by hydraulic fracturing (Rutqvist et al 2013).…”