A Potential Evaluation and Pilot Test of CO2 Miscible Injection in Daqing, China

Abstract

The paper introduces the entire process for a CO2 injection in the Fang-48 Group, Daiqng Oilfield. A study using experiment and full-field reservoir modeling investigated and optimized the design of a CO₂ miscible flooding project for Fang-48 Group, Daqing. The study began with extensive data gathering in the field and building a full-field three-dimensional geologic model. A fullfield simulation model with relatively coarse gridding was subsequently built and used to history match the depletion and waterflood. This history matching model highlighted areas in the field with current high oil saturations as priority targets for CO₂ flooding and generated a forecast of reserves from continued waterflooding. The estimation of minimum miscibility pressure was conducted with the slimtube method. A full-field CO₂ model with more finely gridded patterns was built using oil saturations and pressures at the end of history in the waterflood model. The CO₂ model identified the best patterns for CO₂ flooding and was instrumental in selecting a strategy for sizing the initial flood area and in determining the size, location, and timing of future expansions of the CO₂ flood. Continuous CO₂ miscible injection and alternating were simulated. CO₂ WAG injections were simulated mainly to observe the improvement of low sweep efficiency caused by override and unfavorable mobility ratio. Main considered sensitivities included the WAG ratio and slug size. The integrated recovery efficiency comparison of CMI and WAG was used to demonstrate the mobility control of the WAG process.