Research and Application of Chemical Water Plugging Technology with High Salt Resistant Gel and Immobile String

Abstract The salinity of formation water in Gasi N1-N2 reservoir is 18 × 10 4 mg/L, in which calcium and magnesium ions are 6300 mg/L. The conventional gel used for profile control and water plugging has poor salt resistance and is easy to dehydrate under the erosion of formation water; At the same time, the chemical water plugging of oil wells in the past needs to trip down the downhole string for many times, and the construction period is long. In order to solve the former problem, an anti-high salt organic gel suitable for Gasi N1-N21 reservoir is synthesized. The formula is 0.4 wt% SD-3000 + 0.1-0.2 wt% urotropine + 0.05 wt% resorcinol + 0.4 wt% additive. The viscosity of the gel is more than 6000 mPa.s after gelation, and no obvious dehydration phenomenon is found after aging for five months in the formation water environment of Gasi N1-N21 reservoir at 65 °C. The technology of chemical water plugging without moving the string has been innovatively developed, which does not require the operation of tubing and pump during construction. In Gasi N1-N21 reservoir, anti-high salt gel was used to carry out three well-times of chemical water plugging tests without pulling the string, which were all successful, saving 44% of the cost of measures and shortening 78% of the construction period. After water plugging, water production was obviously inhibited, and the average moisture content was reduced from 95% to 45%. The average daily oil increment of a single well was 1.8 tons, and the cumulative oil increment was 1700 tons. The results show that the chemical water plugging technology without pulling string has broad application prospects in Gasi N1-N21 reservoir in Qinghai Oilfield and similar reservoirs in China.