A study of injection-induced mechanical deformation at the In Salah CO2 storage project

The In Salah project (a joint venture of BP, Statoil and Sonatrach) includes a CO2 sequestration effort that has successfully injected millions of tons of CO2 into a deep saline formation close to a producing gas field in Algeria. We have performed detailed simulations of the hydromechanical response in the vicinity of the KB-502 CO2 injection well specifically because the morphology of the observed surface deformation differed from that above the other injectors at the field. We have simulated the mm-scale uplift of the overburden associated with the injection and compared the results with observed ground surface deformation measured by InSAR. By solely including conducting and bounding faults in the model we achieve better agreement with the magnitude of the observed net uplift at the ground surface, but not the shape of the uplift pattern. However, by further including flow into a hypothetical vertical extension of a fault, our simulations better match the morphology of the surface deformation. Our results indicate that the best fit is obtained through a combination of reservoir and fault pressurization, rather than either alone. However, our analysis required assumptions regarding the mechanical properties of the faults and the overburden. These results demonstrate that InSAR provides a powerful tool for gaining insight into the fate of fluid in the subsurface, but also highlight the need for detailed, accurate static geomodels.