A New Screening Evaluation Method for Carbon Dioxide Miscible Flooding Candidate Reservoirs

Prior to the implementation of CO2 injection EOR projects, the screening evaluation of candidate reservoirs will promote the economic benefits of CO2 injection. Currently, a uniform screening method for CO2 miscible flooding does not exist. Based on more than 112 successfully implemented CO2 miscible flooding reservoirs, which was referred in 2010 Worldwide EOR Survey, and CO2 miscible flooding mechanisms, this paper picks out 12 reservoir and fluid parameters affecting CO2 miscible flooding results as comprehensive evaluation parameters for screening candidate reservoirs. According to investigations on a large number of domestic and international CO2 miscible flooding projects, the quantitative methods are determined by theoretical analyses, field experience, and probability statistics. By means of calculating the combinational weights by improved analytical hierarchy process (AHP) and entropy method and combining the advantages of technique for order preference by similarity to ideal solution (TOPSIS) with gray relational analysis to construct a new similarity nearness degree, the weighted GC-TOPSIS model is established for screening candidate reservoirs. This screening method was employed for the assessment of five classical candidate reservoirs proposed for CO2 miscible flooding. The results show that this new method can correctly evaluate and compare the potential of CO2 miscible flooding.