With a growing emphasis on safety of thermal operations in the Canadian oilsands operations, the focus of the industry on caprock integrity during SAGD has been increasing. A SAGD operation may create a high degree of deformation in the reservoir rock because of the stresses induced by pressure and temperature. This might yield to a failure of both the reservoir rock as well as the caprock. Thus, there is a need to understand the impact of various geomechanical and operational parameters on overall safety of a SAGD operation.
In this paper, caprock failure during SAGD was modeled using a coupled simulator to integrate reservoir flow with geomechanical deformation. Representative Canadian oilsands properties were used for the simulation. Both shear and tensile failures were modeled and the surface heave/deformation was recorded.
Sensitivity analyses and uncertainty assessments were performed to understand the effect of various geomechanical properties on caprock integrity and surface heave, including Young's modulus, Poisson's ratio and thermal pore pressure. At the same time, operating conditions such as well spacing and maximum injection pressure were also altered to see their effect on caprock integrity. This was done for different geological scenarios and different reservoir depths. Based on this study, we attempt to develop a generic workflow for quantifying the uncertainty associated with caprock integrity and minimizing the risk associated with caprock failures in any SAGD project.