A New Screening Method for CO2 Flooding Candidate Condensate Gas Reservoirs Based on Fuzzy Comprehensive Evaluation and Analytic Hierarchy Process

Summary As condensate gas reservoirs enter the later stages of depletion, CO2 injection can simultaneously enhance natural gas production and facilitate carbon sequestration, making it an ideal secondary recovery technique. The application of CO2 injection in gas reservoirs is crucial to China’s energy development and can significantly contribute to achieving the “carbon neutrality peak” goal. To identify condensate gas reservoirs suitable for CO2 injection, this study establishes a specialized evaluation method for CO2 injection suitability. Based on extensive literature review, experimental data, and field application, the study conducts an in-depth analysis of the key factors influencing CO2 injection. A standardized system is proposed, which includes four primary evaluation indicators and 14 secondary indicators, with their parameter ranges optimized. Using fuzzy mathematics, a comprehensive evaluation framework for CO2 injection suitability is further developed, and the weights of each indicator are determined through the analytic hierarchy process (AHP). Taking the H condensate gas reservoir as a case study, the CO2 injection suitability evaluation method was applied, and the results aligned with the field outcomes of enhanced recovery through CO2 injection in the H condensate gas reservoir, demonstrating the practical applicability and reliability of the proposed method. This method can be used to evaluate the CO2 injection suitability of target blocks before initiating CO2 injection projects, thereby improving the success rate of CO2 injection operations.