Coupling of Multiphase Flow and Geomechanics in Fractured Porous Media: Application to CO2 Leakages from Natural and Stimulated Fractures

Abstract:

Leakage to the atmosphere of a significant fraction of injected CO2 would constitute a failure of a geological CO2 storage project from a greenhouse gas mitigation perspective. We present a numerical model that simulates flow and transport of CO2 into heterogeneous subsurface systems. The model, StoTran, is a flexible numerical environment that uses state-of-the-art finite element and finite volume methods and unstructured adaptive mesh refinement scheme implemented using MPI and OpenMP protocols. Multiphase flow equations and the geomechanical equations are implicitly solved and either fully or sequentially coupled. StoTran can address inverse and forward problems under deterministic or stochastic conditions. For the current study, StoTran has been used to simulate several scenarios spanning from a homogeneous single layered reservoir to heterogeneous multi-layered systems, which including cap-rock with embedded fractures, have been simulated under different operations of CO2 injection and CO2 leakages conditions. Results show the impact of the injection and leakage rates on the time evolution of the spread of the CO2 plume, its interception of the fractured cap-rock and the risk associated with the contamination of the overlaying aquifer. Spatial and temporal moments have been calculated for different, deterministic of stochastic, subsurface physical and chemical properties. Spatial moments enable assessing the extent of the region of investigation under conditions of uncertainty. Furthermore, several leakage scenarios show the intermittence behavior and development of the CO2 plume in the subsurface; its first interception with the fractures located further far from the injection well then, at a second stage, its interception with the fracture within the immediate vicinity of the injection well. We will present a remedy to CO2 leakages from the reservoir in order to enhance a long term containment of the injected CO2.

 This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.