Influence of temperature-viscosity behaviors of Karamay oil sand bitumen on the geomechanics in the SAGD process

Viscosity-temperature behavior is important for the thermal recovery of bitumen: firstly, it is a criterion for evaluating the evolution of mobility with temperature, which affects oil production; and secondly, it determines the role of bitumen in the geomechanics in oil sand reservoir. To quantitatively evaluate the effect of temperature on dynamic viscosity, some experimental and modeling investigations were conducted. The viscosity of Karamay oil sand bitumen over a temperature range of 20 ~ 350 °C was measured, and the viscosity-temperature behavior was simulated by a modified three-parameter model using the least square method. It was found that the viscosity of Karamay bitumen drops sharply with the temperature increase. The effect of bitumen viscosity on the geomechanics in the SAGD process was discussed in terms of reservoir deformation, fluid flow, and heat transfer behaviors. The reservoir deformation, fluid flow, and heat transfer behaviors at varying bitumen viscosity show significant differences in the drained, partially drained, and undrained geomechanical zones. The structure’s bulk modulus, effective stress, and volumetric strain in the drained zone are lower than those in the undrained zone; while the oil mobility and Peclet number show the opposite tendency. The changes in the structure’s bulk modulus, effective stress, volumetric strain, oil mobility, and Peclet number due to the phase change of bitumen increase with the increase of oil saturation. This study can provide the field engineers with guidance for the design of a proper oil recovery scheme before its implementation, and with a useful relation for the coupled thermal-flow-structure analyses.