Study on Chemical Channeling Control Technology of Hydrocarbon Gas Flooding in Mahu Tight Conglomerate Reservoir

In view of the problem that the enhanced oil recovery of hydrocarbon gas drive is limited by gas channeling between injection and production wells after volume fracturing of horizontal wells in tight reservoirs, this paper combines the geological understanding of relevant blocks and the analysis of injection-production performance, optimizes the chemical channeling sealing system, and makes clear the process parameters such as injection slug, speed and pressure limit in the field construction of chemical channeling control of hydrocarbon gas drive, and makes clear the feasibility of this method through field tests. The research results show that there is a hypertonic channel between a gas injection well Z1 and its corresponding first-line production well C1, which leads to gas channeling between Z1 and C1 and weakens the displacement effect between Z1 and its other corresponding first-line well C2. Considering the high injectivity and reservoir adaptability of low permeability reservoirs, the polymer gel profile control and channeling control system with initial viscosity as low as 30 ∼ 120 mPa· s, gel-forming strength as high as 2000∼12000 mPa·s and stable period as long as 180d at 90 °C is optimized indoors. Based on the packer of gas injection pipe string, fracturing operation parameters in the early stage and gel formation time of the system, a general injection mode with a pressure limit of 30MPa and a speed of 0.025∼0.3m3/min is designed, and a slug channeling control mode of “ fresh water recharge+high viscosity polymer pre-placement+polymer gel profile control” is formed. The field test of profile control and channeling control by hydrocarbon gas drive shows that the gas injection pressure of well Z1 is increased by 4 ∼ 7 MPa; The average daily oil increase of C1 well corresponding to gas channeling is 5.4 tons, and after the measures, the cumulative oil increase is 977 tons in 181d. The average daily oil increase of C2, the production reduction well corresponding to hydrocarbon gas flooding, is 7.7 tons, and the cumulative oil increase is 1394 tons after 181d production. Overall, it shows that after the chemical control of gas channeling by hydrocarbon gas flooding, the injection-production wells are obviously affected, and the injection-production wells are effectively driven. This technology has popularization value in improving the gas drive development effect of Mahu tight reservoir, and has certain reference significance for efficient gas injection development of tight reservoir.