Thermal recovery strategies for thin heavy oil reservoirs

Up to 80% of heavy oil reservoirs in Western Canada are less than 5 m thick and as yet the only economic processes are cold production ones which realize recovery factors between 10% and 15%. This implies that >85% of the oil remains in the ground after the process becomes uneconomic to continue operation. At this time, no thermal processes exist that are economic. Here, a reservoir simulation study was conducted to guide the design of thermal recovery processes for a heavy oil reservoir with a thickness of 4 m by comparing different operating strategies including Steam-Assisted Gravity Drainage (SAGD), steam flooding, hot water flooding, and alternating steam/hot water flooding. A base case of cold production (without sand) was also done for comparison purposes. It was found that the cold production case was not viable with very low recovery factor. Higher recovery factor was achieved by using SAGD strategy but at a poorer thermal efficiency. Steam flooding operations exhibits better performance than SAGD in terms of heat utilization. However, its high heat loss to the over and underburden leads to higher cumulative-energy-injected-to-oil ratio (cEOR). Hot water flooding, however, achieved oil production rates comparable to steam flooding at much lower cEOR. The flood cases are tested at different well separations. However, the results suggest that hot water flooding alone may not be the target process of choice for thin heavy oil reservoirs and solvents may be needed to lower the energy intensity further.