Modified Method for Estimating Geothermal Resources in Oil and Gas Reservoirs
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Modified Method for Estimating Geothermal Resources in Oil and Gas Reservoirs Kewen Li · Wenjie Sun
Received: 16 July 2013 / Accepted: 19 December 2013 © International Association for Mathematical Geosciences 2014
Abstract Increasing attention has been paid to the power generated by utilizing hot fluids that are co-produced from oil and gas reservoirs, as well as other geothermal resources. It is thus essential to evaluate the geothermal resource in oil and gas reservoirs accurately. Although there are a number of approaches for determining the geothermal resource associated with oil and gas fields, a lot of problems are yet to be solved. Previous studies on the effects of oil and gas saturation on the geothermal resource were considered; however, it was assumed that the oil and gas saturations were constant during the development, which is not true. To this end, the existing volumetric approach of evaluating geothermal resource in oil and gas reservoirs was modified by considering the change of oil and gas saturation with time. An oil reservoir from Huabei oilfield with a moderately high temperature was chosen as a target reservoir to apply the modified method. The effects of porosity, oil and gas saturations, and reservoir rock type on the geothermal resource were studied and the results compared to existing approaches. Also, the possible energy and income that might be generated from this geothermal system were estimated. The results indicate that the geothermal resource, energy, and possible income have been overestimated by the existing models, and the difference becomes more significant as the oil or gas saturation increases.
K. Li (B) China University of Geosciences, Beijing 100083, China e-mail: [email protected] K. Li Stanford Geothermal Program, Stanford University, Stanford, CA 94305, USA W. Sun School of Earth and Space Sciences, Peking University, Beijing 100871, China W. Sun Research Institute of Petroleum Exploration and Development, China National Petroleum Corporation, Beijing 100083, China
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Math Geosci
Keywords Modified method · Geothermal resource · Fluid saturation · Porosity · Oil and gas reservoirs
1 Introduction Currently, a large number of oil and gas fields are in the late period of development. Water cut in these mature oil and gas fields is very high, even up to 97 %. The traditional oilfield has become a water field (Xin et al. 2012). The produced water is usually considered a nuisance to oil and gas producers, because it is required to dispose or re-inject the water into reservoirs. This process costs a lot and reduces the net profit value of the oil and gas producers. The development of these oil and gas fields becomes a huge challenge because of its high cost, and one of the solutions to this problem may be electricity generated by utilizing the geothermal resource co-produced from the oil and gas reservoirs (Erdlac et al. 2006, 2007; Li et al. 2007, 2012, 2013; Xin et al. 2012). This is because many of the high water cut oil and gas reservoirs produce water with a temper
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