Low Permeability Fractured Reservoir Drive Co₂ Plugging Technology

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.