Steam-assisted gravity drainage (SAGD) is the present method of choice to produce the initially immobile bitumen in oil sands. However, the unit cost of production and its energy intensity offer room for improvement through further development of the technology. Dissolved gas presents a challenge due to free gas formation upon heating. To establish equilibrium and due to local pressure gradients, this gas is pushed to the edges of the steam chamber, where temperatures are lower. The gas acts as a thermal insulator, reducing the efficiency of heat transfer between the steam and bitumen. Currently, injector wells create small axial pressure gradients which allow for gas to be swept to low pressure locations where it can accumulate and get produced.

This study presents a novel well configuration to increase gas production and reservoir sweep efficiency. By drilling the injector well shorter than the producer well and adding tubing to the toe in the producer, the gas will be swept towards the toe and produced. The hot emulsion flowing through the producer annulus will heat the toe region by conduction, allowing the steam chamber to spread progressively towards the toe.

A simulation study was conducted. Homogeneous reservoir simulations were performed and the proposed process was compared to several base cases with varying completions, fluid properties, and reservoir properties based on current oil sands projects. Heterogeneous simulations were performed with a non-porous shale baffle in varying locations. Results were compared to classical SAGD and an in-depth analysis was performed to understand the mechanisms behind the improvements and better optimize the process.

The homogeneous simulations indicate that the proposed process is very efficient at removing solution gas from the reservoir, which increases oil production rates. Steam to oil ratio (SOR), a measure of process energy efficiency, is reduced. The proposed process outperforms classical SAGD with conventional completion scheme in all heterogeneous simulations as well, both in terms of oil production rate and SOR. Simulations suggest startup can be performed the same as conventional SAGD. Overall, the proposed process is very easy to implement and offers significant benefits over classical SAGD with similar or reduced costs.

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