Use of thermal geomechanics for improving vertical communication in oil sands reservoirs with interbedded shales

摘要

This paper investigates the potential of using heating or cooling to induce shear or tensile failure of the shales present in low-quality oil sands of Alberta and thus improve vertical communication and recovery. Several methods were considered and explored by conceptual simulations, in a setting representative of Nexen Energy ULC Long Lake reservoir. Various scenarios were simulated using a coupled thermal reservoir and geomechanical modeling software (GEOSIM). In order to capture the relevant physics, significant extensions to the software were required, for modeling cryogenic cooling and thermal dependencies of properties. The main findings of the study are:-Electric heating using the SAGD injector well can induce shear failure in shales close to it. It also creates a shear failure region around the injector and it could be considered as a modification of the start-up strategy.-Modeling of cryogenic cooling requires capturing several ice formation effects, which have a strong effect on stresses and failure. Cryogenic cooling directly in the shale predicted progressive shear failure to a considerable distance from the injector. 2-D simulations of cooling the SAGD injector show that the horizontal stresses can be considerably reduced and will favor vertical fractures-Hydraulic fracturing after a sufficient cooling period appears to be a feasible process which can be carried out with significantly reduced injection pressures, comparable to MOP (maximum operating pressure).