Relative permeability plays a significant role in predicting oil rate and ultimate oil recovery factor. The literature reveals that same set of relative permeability is often used to predict the ES-SAGD performance regardless of not only the downhole operating temperature but also the injected solvent concentration. This can lead to significant errors when predicting the ES-SAGD performance and its economical feasibility. In paper SPE-180713-MS, SAGD relative permeability was presented as a function of temperature. In this paper, a series of realistic ES-SAGD relative permeability curves were developed based on experimental work combined with simulation studies.
A typical Athabasca oil and sand were used to obtain the experimental data and construct relative permeabilities using unsteady-state method. First residual oil saturations were determined in presence of hot water and steam flooding under SAGD condition at a given temperature. Following that, a typical n-alkane (n-heaxane) solvent was co-injected with steam at different concentrations varying from one to 25 weight percent of the injected steam while the operating temperature was kept constant. The produced oil and water volumes were collected and measured during the hot water, steam injection, and solvent co-injection experiments. The data were utilized to construct the relative permeability curves at a given operating temperature (200 °C) and various solvent concentrations. Finally, a series of reservoir simulations were performed to history match the lab experiments and examine the accuracy of inferred relative permeability curves.