Optimization of in-situ combustion processes: A parameter space study towards reducing the CO₂ emissions
2011
Liu, Zhenshuo | Jessen, Kristian | Tsotsis, Theodore T.
Enhanced oil recovery (EOR) through in-situ combustion (ISC) is a process that utilizes a fraction of the oil in-place as fuel in order to upgrade and displace the hydrocarbons in heavy oil reservoirs. In ISC processes, air is injected into a heated section of the reservoir. Upon reaching a threshold temperature, the oxygen in the injected air reacts with the oil in-place and generates heat, a lighter oil fraction, as well as steam and other gaseous reaction products, primarily CO₂, which help drive the upgraded oil (lighter fraction) towards the production wells. ISC processes can, as a result, be highly efficient but at the same time produce significant amounts of CO₂, a potent greenhouse gas. In this paper the emphasis is on developing an ISC process with significantly reduced CO₂ emissions. The process involves the capture and re-injection of CO₂ into the formation. We find that, in addition to reducing the CO₂ emissions, this novel process also shows improved oil recovery rates relative to conventional ISC without CO₂ capture and recycle. We observe, for example, increases in the oil recovery of ∼33% for a fixed time of operation when comparing the ISC process with CO₂ recycle against the conventional ISC process. In addition, at the time when 80% of the total oil in-place has been produced, the CO₂ emissions are consistently lowered by 18–22% when CO₂ is recycled back into the formation. This study analyzes the characteristics and dynamics of the process and explores the effect of the relevant process parameters. For a wide range of Peclet and Damköhler numbers as well as initial saturations, favorable trends induced by CO₂ recycling are observed.
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