Optimization of Well-Pair Spacing and Well Configuration for the SAGD Process in the Oilsands Reservoirs

The performance of steam-assisted gravity drainage (SAGD) is influenced not only by reservoir properties, but also by well-pair spacing. Field operators empirically increase the well-pair spacing for thicker reservoirs. However, a quantitative method is needed to determine the well-pair spacing based on reservoir properties. This study accordingly developed an optimization method for well-pair spacing using the properties of representative oil sands reservoir in Athabasca, Canada. In addition, the economic feasibilities of narrow-spacing and infill well-drilling methods were compared. A sensitivity analysis of vertical permeability and reservoir thickness was conducted to identify reservoir conditions under which SAGD operations are economically viable. The results revealed that the optimal well-pair spacing was the reservoir thickness multiplied by five, subtracting 50 m when the vertical permeability was 500 mD, and five times the reservoir thickness for vertical permeabilities of 1,500 mD and 2,500 mD. The infill well-drilling method with the optimized well-pair spacing showed the highest performance among the well configurations considered.