Geologic CO2 Storage Optimization under Geomechanical Risk Using Coupled-Physics Models

Abstract

Numerical simulation of fluid flow, transport, and trapping mechanisms have been used to optimize CO2 storage in geologic formations by improving trapping efficiency through injection strategies. Flow models, however, do not capture the geomechanical deformation that can occur during CO2 injection, including reservoir expansion, ground surface uplift, and induced seismicity. The geomechanical risks of CO2 injection have drawn more attention in recent years and coupled flow and geomechanical simulation models are increasingly used to study the geomechanical effects during CO2 injection, to ensure environmentally sound and safe operations. We present an optimization framework for geologic CO2 storage under geomechanical risks, where coupled flow-geomechanics simulations are used to quantify the risks of injection-induced ground surface deformation and rock failure in reservoir and caprock layers. A multi-objective optimization problem is formulated and solved to maximize CO2 storage while minimizing the two forms of geomechanical risks. The optimization decision variables include the locations of injection wells. Multiple numerical experiments with increasing complexity are presented to demonstrate the performance of the proposed framework. The results reveal optimal decisions that are different from those obtained from flow-only simulation that disregard the geomechanical risks associated with CO2 injection. When geomechanical risks are considered, the wells may not necessarily be concentrated in areas with the highest storage capacity because that may lead to rock failure and/or unacceptable levels of ground surface uplift. Overall, the observations from this study reveal important differences in optimization results and conclusions when geomechanical risks of geologic CO2 storage are considered.