The large-scale geomechanical and hydrogeological effects of multiple CO2 injection sites on formation stability

We present results of a recent study investigating geomechanical and hydrogeological consequences of large-scale deployment of CO2 sequestration within a region spanning tens of kilometres. This initial study considered a faulted aquifer bounded above and below by impermeable rock. We performed a parameter study of fault activation due to elevated pore pressures and addressed several combinations of injection scenarios and in situ stress orientations. The simulations were performed using iteratively coupled flow and geomechanical capabilities. For each scenario, multiple fluid injectors were simulated using a non-steady reservoir flow model while geomechanical analysis predicted the evolving potential for fault reactivation within the reservoir and concomitant permeability evolution. It is observed that the initially considered scenario leads to a loss of containment of fluid from the storage domain. However, alternative scenarios involving either different in situ stress conditions, or modified injection scenarios resulted in successful containment. The results highlight the importance of site selection, site characterization and in situ stress determination when pressure waves from multiple wells and multiple faults interact, and demonstrate the ability of existing tools to help resolve these issues. The results also emphasize that site-specific injection scenarios will be required to manage permitting, deployment, and operations in such a way as to avoid unintended negative consequences, such as large-scale fault activation, related to large-scale deployment. (C) 2010 Elsevier Ltd. All rights reserved.