Optimization And Numerical Simulation Of CO₂ Oil-dispelling Target Layer In Tight Sandstone Reservoirs In Well A Of Y Oilfield In Northern Shaanxi Province

As an effective method for enhanced oil recovery, CO₂ flooding has become a leading and common technique all over the world and shown a great effect. Especially the CO₂ miscible flooding, which at a certain temperature and pressure, may recover 5%-25% of the original oil in place. While the successful foreign CO₂ flooding technology may not be suitable for the unique tight sandstone reservoir in Shanbei area which has low permeability, strong heterogeneity and well-developed fractures. Therefore, it is necessary to conduct CO₂ flooding feasibility evaluation before CO₂ injection in the tight sandstone reservoir in Shanbei area, so as to form a suitable CO₂ flooding technology series and provide a model for CO₂ enhanced oil recovery ?CO₂-EOR? projects in other low permeability oil reservoir of the tight sandstone reservoir in Shanbei area and even China.Based on the theory and methods of reservoir characterization, geological modeling and numerical simulation, this paper chooses the oil field Y in Shanbei area as the research region, and first describe the features of target strata for CO₂ flooding. Then select the optimum member for CO₂ flooding based on the results of refinement and stratigraphic correlation, fancies analysis, reservoir properties and properties distribution characteristics. Taking the optimum member as the main research object, establish the 3D geological model of the study area. Integrating the reservoir characterization and geological model results, Optimizing the numerical simulation area, combining with the related experiment, and then perform CO₂ flooding numerical simulations in this area.This study designed CO₂ development plan for A well area of Y oil field in shanbei region, in which basic theories of reservoir characterization, modeling and numerical simulation on CO₂ flooding in low permeability reservoir is set up. The main results achieved and understanding are as follows:1. Based on the analysis of regional deposition backgrounds and well logging curves, combined with marker beds, lithology and formation thickness ratio, stratigraphic classification and correlation is conducted. The results show that target strata Chang4+5 in the study area is divided into Chang4+51, Chang 4+521 and Chang4+522,also Chang6 in the study area is divided into Chang61, Chang62, Chang63, and Chang64.2. The study results of sedimentary facies analysis and the feature of reservoir property show that the sand body distribution, connectivity and physical property of Chang4+522 and Chang61 is better, Chang4+522 is the most appropriate target horizon of CO₂ flooding.3. According to the results of 3D geological model, analysis of reservoir fluid and rock experimental, the condition of Chang4+522 in research area is suitable for CO₂ miscible flooding to enhance oil recovery.4. The CO₂ flooding numerical simulation results in Chang4+522 show that the effect of CO₂ flooding is better than that of water flooding. Recommended to adopt CO₂ flooding to improve recovery. Considering economy and storage effect, the injection rate of 75m3d/well is the optimal volume for model to acquire best development effect.