Design of Hybrid Steam-In Situ Combustion Bitumen Recovery Processes |
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| Authors: | Xiaomeng Yang Ian D Gates |
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| Institution: | (1) Department of Chemical and Petroleum Engineering, University of Calgary, Calgary, AB, Canada;(2) Alberta Ingenuity Centre for In Situ Energy (AICISE), Schulich School of Engineering, University of Calgary, Calgary, AB, Canada |
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| Abstract: | Given enormous capital costs, operating expenses, flue gas emissions, water treatment and handling costs of thermal in situ
bitumen recovery processes, improving the overall efficiency by lowering energy requirements, environmental impact, and costs
of these production techniques is a priority. Steam-assisted gravity drainage (SAGD) is the most widely used in situ recovery
technique in Athabasca reservoirs. Steam generation is done on surface and consequently, because of heat losses, the energy
efficiency of SAGD can never be ideal with respect to the energy delivered to the sandface. An alternative to surface steam
generation is in situ combustion (ISC) where heat is generated within the formation through injection of oxygen at a sufficiently
high pressure to initiate combustion of bitumen. In this manner, the heat from the combustion reactions can be used directly
to mobilize the bitumen. As an alternative, the heat can be used to generate steam within the formation which then is the
agent to move heat in the reservoir. In this research, alternative hybrid techniques with simultaneous and sequential steam-oxygen
injection processes are examined to maximize the thermal efficiency of the recovery process. These hybrid processes have the
advantage that during ISC, steam is generated within the reservoir from injected and formation water and as a product of oxidation.
This implies that ex situ steam generation requirements are reduced and if there is in situ storage of combustion gases, that
overall gas emissions are reduced. In this research, detailed reservoir simulations are done to examine the dynamics of hybrid
processes to enable design of these processes. The results reveal that hybrid processes can lower emitted carbon dioxide-to-oil
ratio by about 46%, decrease the consumed natural gas-to-oil ratio by about 73%, reduce the cumulative energy-to-oil ratio
by between 40% and 70% compared to conventional SAGD, and drop water consumption per unit oil produced. However, oil recovery
is between 25% and 40% below that of SAGD. Design of successful hybrid steam–oxygen processes must take into account the balance
between injected steam and amount of injected oxygen and combustion gas products that dilute injected and in situ-generated
steam in the depletion chamber by lowering its partial pressure, and thus its saturation temperature which in turn impacts
production rates and recovery. |
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| Keywords: | In situ combustion hybrid steam-combustion combustion kinetics enhanced oil recovery Athabasca bitumen |
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