Modeling the Present-Day In-Situ Stress Field in a Geo-Energy Reservoir for Geomechanical Dilation-Enhanced Thermal Recovery

During thermal steam stimulation in the unconsolidated oilsands reservoir, fractures are often created to enhance injectivity. This process involves pressurizing and heating the reservoir, leading to changes in stress. The current understanding of the in-situ stress fields in mature oilsands reservoirs post thermal stimulation is limited, and the impact on ongoing reservoir stimulations is uncertain. Using minifrac stress tests as constraints, we developed the present-day in-situ stress field through integrated geomechanics and reservoir simulations on a mature oilsands reservoir. Both room-temperature and high-temperature triaxial tests were conducted to explore the thermal effects on oilsands strength, while multiple open-hole minifrac tests measured the in-situ stresses. We employed a multiphase thermal reservoir simulator coupled with a geomechanics finite element simulator to predict the present-day in-situ stress field by simulating temperature, pore pressure, and effective stress distributions, which complements previous isothermal studies on coupled reservoir-geomechanical analysis. Our findings reveal that years of steam stimulation led to notable changes in the magnitudes and orientations of the in-situ stress field. Steam injection amplified the in-situ stress around the steam chamber, with only partial stress recovery during production due to the formation’s elasto-plastic deformation. Future reservoir stimulation plans for this highly heterogeneous reservoir need careful consideration, as factors such as oil recovery, optimal well spacing and trajectory, and operational strategy hinge on the current in-situ stress field.