The Importance of Poromechanics for CO2 Storage Integrity

Understanding deformation related to CO2 injection into subsurface reservoirs is crucial to ensure storage integrity, but our understanding is hampered by the lack of models that capture the non-linear interaction between fluid flow and complexly deforming rocks. We developed new fully coupled (i.e. the solid feels the fluid pressure and fluid flow is affected by solid stresses and deformation of the porous rock) models that allow the simulation of CO2 injection and flow in a stressed crust that may deform visco-elastically, including non-linear rheology leading to weakening. These simulations reproduce features observed in CO2 injection operations, such as localization of flow into chimneys or channels and flow that is (locally and periodically) faster than predicted by Darcy flow. The model also allows investigating the effect of injection on the over-, under- and sideburden of the reservoir and to predict the effect of stress changes in the neighbouring formations. Comparison of a fully coupled with an incompletely coupled simulation illustrates the necessity of proper coupling.