Evaluation of CO2 Flooding in the Fuyang Ultra-Low Permeability Reservoirs

In order to figure out an effective recovery technique for the Fuyang ultra-low permeability reservoir, CO2 flooding pilot test and expanded industrial test have been successively carried out in Daqing Oilfield from 2003 to 2007. In this paper, through single-factor analysis of development indicator in CO2 flooding test of ultra-low permeability reservoir, the CO2 flooding evaluation indicators and weights are clarified. Considering the development features of CO2 flooding, the miscible volume coefficient and relative miscible degree are introduced, a CO2 flooding evaluation process is established, and a flowchart of CO2 flooding comprehensive evaluation is formed. According to the CO2 flooding theory and the practice of CO2 flooding test, the evaluation criteria for development indicator is determined. Finally, a comprehensive evaluation is made on CO2 flooding in three long-term test areas. The evaluation results show that the CO2 flooding is better performed in the S pilot test area and F pilot test area than in the F expanded test area, which are consistent with the field test results. The proposed method lays a foundation for the comprehensive evaluation of CO2 flooding in the Fuyang ultra-low permeability reservoir, and is referential for similar reservoirs.