Thermal methods for heavy oil and bitumen recovery include the injection of steam as in the SAGD (Steam Assisted Gravity Drainage), CSS (Cyclic Steam Stimulation), and steam flooding processes. Thermal energy increases the temperature of the oil, reducing its viscosity and thereby allowing it to flow efficiently towards a production well. The electro-thermal process is an alternative (possibly a compliment) to steam injection processes. With ever-increasing natural gas prices, or corresponding reduction of natural gas supply, electro-thermal processes can be economically competitive compared to other thermal methods. An optimized electrothermal process can bring over 75% of heavy oil or bitumen to the surface as demonstrated by a recent field pilot in the Athabasca oil sands.
This study aims at optimizing electrothermal processes by vaporizing water in-situ. The Computer Modeling Group (CMG) reservoir simulation software is used to perform a series of preliminary simulation studies of electro-thermal heating in the Athabasca oil sands. First of all, the incremental oil recovery by vaporization is estimated based on a three block conceptual model. Secondly, a field scale model is set up to evaluate the effect of electrode spacing, water injection rate and electrical heating rate on the ultimate bitumen recovery. A statistic tool is used to analyze the simulation results in order to spot the optimum condition for maximizing bitumen production with water vaporization in-situ.
Simulation results showed that the incremental recovery brought by the water vaporization could be as high as 25% OOIP for Athabasca oil sands reservoirs based on the conceptual model. A sensitivity study on the field scale model, showed that the combination of medium electrical heating rate, low water injection rate, and small electrode spacing can maximize bitumen production economically with mild water vaporization in-situ.
The study demonstrated a promising technique for the future heavy oil / bitumen production. It also showed that electrothermal processes could be operated independently and produce considerable amount of bitumen economically.