Carbon Capture and Storage (CCS) in a geological formation is being implemented in different countries around the world as an alternative to reduce CO2 emissions from the atmosphere. To assess the CCS project implementation feasibility, it is necessary the assurance of the injected CO2 confinement considering the main trapping mechanism (e.g., structural trapping, residual gas or mineralization, etc.) and operational parameters like injection rate/pressure and caprock integrity.

The caprock integrity is the key to avoiding CO2leakage to the surface or overlying formations, like freshwater aquifers, due to the pressure increase during the CO2 injection. To mitigate the risk of caprock failure, a full compositional, geochemical and geomechanical coupling approach must be implemented to estimate the fluid flow, the gas solubility in the aqueous phase, the stress distribution and the deformation in the formations. As part of the CSS modelling, it is also necessary to optimize the operational parameters to inject the maximum volume of CO2 considering the caprock properties uncertainties.

In this work, we present an integrated methodology to mitigate the caprock failure risk in a CSS project using compositional/geomechanical coupled numerical simulation. In this methodology we show the main physical/chemical effects that must be considered in the reservoir model during the CCS modeling. Subsequently, a geomechanical model was coupled to the reservoir model, to consider the effect of the stress distribution changes on the caprock integrity. Finally, an optimization study was performed considering operating well constraints and well location looking for an increase of the volume of CO2 injected avoiding caprock failure.

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