Production Induced In Situ Stress Change and Geomechanical Dilation to Boost the Production in an Offshore Oilsands Reservoir

Geomechanical dilation was implemented in an offshore cyclic steam stimulation (CSS) well in a mature oilsands reservoir to improve steam injectivity and enhance oil production. Designing such a treatment requires reliable characterization of the present-day in-situ stress state and coupled thermal–reservoir–geomechanical analysis yet stresses in thermal mature oilsands reservoirs are typically poorly constrained. In this study, the target well was tested with minifrac tests both before CSS and after an initial CSS cycle, providing rare before-and-after constraints on stress evolution. Interpretation of the two minifrac data sets indicates a reduction of ~ 3.8 MPa in the minimum horizontal stress (Shmin) near the injector, consistent with poroelastic stress relaxation caused by reservoir pore-pressure depletion. Laboratory triaxial tests at room and elevated temperatures were performed to quantify the temperature dependence of oilsands strength and stiffness. These data, together with the updated minifrac-derived stresses, were used to calibrate an iteratively coupled CMG-STARS–ABAQUS model that simulates multiphase thermal flow, geomechanical deformation, and shear-induced dilation. The coupled model was then applied to design a field-scale dilation job on the horizontal CSS well, ensuring that injection pressures exceeded the dilation threshold while remaining below the tensile breakdown pressure. Field execution of the treatment generated a laterally continuous high-permeability dilation zone around the well, reduced the surface steam-injection pressure by ~ 1.2 MPa at a designed steam injection rate, and allowed the planned steam volume to be injected without exceeding operating limits. The subsequent CSS cycle exhibited substantially higher and more sustained oil rates than the pre-dilation cycle. Overall, the results demonstrate that thermally induced stress changes can be significant in offshore oilsands reservoirs and that combining repeated minifrac measurements with coupled reservoir–geomechanical modeling provides a robust basis for designing effective, stress-informed geomechanical dilation treatments.