Modeling of Geothermal Power Generation from Abandoned Oil Wells Using In-situ Combustion Technology

Abstract

There is a great amount of oil still remaining in abandoned oil reservoirs because of technology and economic limitations. The residual oil saturation is usually over 30% in many abandoned oil reservoirs. This paper investigated the feasibility of acquiring both oil and geothermal energies from these abandoned oil wells using the in-situ sub-combustion technology by air injection. This method can also help ease the serious pollution problems caused by leakage of residual oil. Air may be injected in these abandoned oil reservoirs and in-situ combustion will occur through oxidization. Based on the existing research, the temperature in oil reservoirs under air injection with in-situ combustion could reach over 400oC for light oil reservoirs and over 600oC for heavy oil reservoirs. High temperature and high pressure steam can be obtained for power generation using water injection. A closed loop double pipe heat exchanger system was adopted in order to recover the geothermal energy from the oil wells. The simplified model describing the heat change of fluids from bottom to wellhead were proposed and the mathematical equations were developed to assess the economic benefit and feasibility. The proposed model was compared against other models, in order to determine the reliability and accuracy of the proposed model. Comparing with other geothermal recovery methods, the proposed approach could recover both the abandoned oil and geothermal energies more efficiently, obtaining 3-4 times more energy in total.