The research and application of compound flooding system in the block L of Huabei oilfield

Abstract

In the three rounds of gel flooding of the block L in Huabei oilfield, better effect of watercut decreasing and oil increasing had been achieved. In order to further develop the remaining oil potential, an oil-displacement slug was added on the basis of the gel slug, to form a compound flooding system in order to improve the oil displacement efficiency. Two types of oil displacement agents were optimized through basic performance evaluation. NO.I is surfactant. When the concentration was 0.3 percent, the oil-water interfacial tension could reach 1.15 ×10−3mn/m and still remain within the ultra-low interfacial tension range after 150 days under formation temperature but the static adsorption loss was only 3.4mg/g. NO.II is a kind of granular oil displacement agent with certain sealing ability.The initial particle size was 189nm and the size reached 520nm after hydration for 30 days and remained stable. In the sand filled tube with a permeability of 550×10−3μm2, the plugging rate was up to 70.88 percent. Through the double tube with high-low permeability core experiments, the oil displacement effect of movable gel, movable gel with oil displacement agent I and movable gel with oil displacement agent II were further compared. The results showed that movable gel with oil displacement agent II could improve oil recovery by 20.95 percent compared with water flooding, 7.88 percent compared with movable gel and 5.92 percent compared with movable gel with oil displacement agent I.The composite flooding system was applied in the block L with 6 wells and the effect of watercut decreasing and oil increasing was significant. The daily oil increase in peak period was 10t, and the watercut was decreased by 5.3 percent. The accumulative oil increase was 2736 tons with 13 months validity and will continue to be effective.