OPTIMIZATION OF CO2 WATER-GAS ALTERNATING INJECTION-PRODUCTION PARAMETERS IN LOW PERMEABILITY RESERVOIRS

The reservoir heterogeneity of low permeability reservoir is strong, and it is easy to form fingering phenomenon in the process of continuous water injection or gas injection development. The use of CO2 water-gas alternation technology can not only make full use of the advantages of CO2 flooding, but also effectively reduce the fingering phenomenon and improve the development effect. However, due to the unreasonable injection rate, slug size, gas-water ratio and other parameters, the CO2 breakthrough in the production well is too early or the expected development effect is not achieved. Therefore, it is necessary to study the optimization of CO2 watergas alternating injection-production parameters in low permeability reservoirs. Based on the actual formation and fluid characteristics of A oilfield, the reservoir numerical simulation method was used to optimize the injection-production parameters of CO2 water-gas alternating flooding in this area. The results show that the development effect is the best when the water injection is first followed by gas injection, the gas injection rate is 0.08 PV / year, the water-gas ratio is 1:2, and the alternating period is 3 months. The recovery rate is 42.15 %. The scheme is 13.67 % higher than the pure water flooding scheme and 4.89 % higher than the pure gas flooding. The research results have certain reference significance for improving the mining effect of A oilfield.