The SAGD process can be achieved only after the thermal and hydraulic communication between the injection well and the production well has been established during the start-up operation. The start-up operation involves interactions of geomechanical responses and multiple phase flow behaviors in the inter-well formation. Such interaction would have an impact on SAGD in terms of recovery performance. This paper presents an experimental study on investigating the mechanisms and mechanics of geomechanical dilation and fundamentals during cold-water injection.
A triaxial experimental program has been designed and conducted to verify geomechanical dilation through experimental measurements. A series of reconstituted water-wet/bitumen sand specimens were prepared with different fluid saturation and almost identical void ratio. Reclaimed/cleaned tailings sand from oil sands mining operations was used to prepare artificial specimens, which are representative of McMurray Formation oil sands. A water-wet or bitumen sand core plug was then tested in an environmental chamber to simulate reservoir boundary conditions in terms of stress state, temperature, and pore pressure. A series of experiments were carried out in a triaxial cell under either initial isotropic or initial anisotropic stress state. Experimental results highlight the promising potential to dramatically enhance effective permeability to water and porosity in the dilated zone with pore pressure injection at modest levels of stress anisotropy.
The lab-scale experimental data provides supports on development of numerical models for predicting SAGD start-up performance and on proactive utilization of the dilation as start-up process for in-situ oil sands development.