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Reservoir permeability of CO2 flooding test area in Block Da Qing Zi Jing in Jilin Oilfield is about 3.0~5.0 mD with poor physical properties, such as thin and multilayer reservoir, developed fractures, and strong heterogeneities. Therefore, commingled gas injection indicates there are large differences of gas injection between reservoirs, gas oil ratio increases in some oil wells. In order to inhibit the gas channeling, control flow pressure gradient and ensure the miscible displacement, profile control technique is an effective way to enlarge swept volume and enhance flooding EOR. According to reservoir characteristics, the gelling intensity could reach to 20000mpa.s under acidic condition. The system has the features of shearing resistance property, scouring resistance. Plugging efficiency of the core was higher than 92.0%. Based on the mechanisms of dual plugging of gel and foam, blocking gas channeling channels and enlarging swept volume of gas injection can be achieved. This technique had been applied in profile control test in five wells in CO2 test area of block Da QingZiJing and success rate is 100%. Injection pressure increases by 70.0%. Gas -liquid ratio decreases and oil production rate in the well group increases by 40.0%, the results show that profile control techniques can effectively plug gas channeling and enhance CO2 flooding EOR.

Abstract The formations of DaQing gas field are mainly volcanic reservoirs which have the characteristics of low permittivity and complex formation structures. Most of these wells need fracturing remodeling to meet the standards of industrial gas stream, and also, the gas productivity tests as well as the pressure recovery tests conducted on these wells are different from other regular gas reservoirs. Considering the nature of the volcanic reservoir, such as dissolution pores, karsts caves, natural fracture development, we built two mathematical models of dissolution pores development and natural fracture development under both of the Darcy flow conditions and Non-Darcy flow conditions separately to predict the production of triple porosity reservoir after gas reservoir well fractures. By using the Laplace transform and numerical inversion, the equation to calculate production of complex volcanic gas wells is obtained. Based on these researches, law of volcanic reservoir productivity is investigated. The theoretical data are compared with the practical data collected from the field operation. The comparison results reveal how the parameter of the fluid volume, proppant indexes, and conductivity of artificial fracturing induced fractures and length of fractures change affect the productivity. The research work reported in this paper provides theoretical support on the optimization method of fractured wells design of volcanic gas reservoir.