Development and Performance Evaluation of Environment-Friendly Self-degradable Polymer Film Workover Fluid System

At present, the chelating acid fluid and PRD drilling fluid in the period of well drilling and completion are still applied as the workover fluid in Weizhou Oilfield. Leakage often occurs due to the insufficient plugging ability of chelating acid workover fluid, which will not only lead to the waste of workover fluid but also cause reservoir damage and low oil and gas production. After PRD drilling and workover, it is difficult to break the gel, resulting in plugging and the sharp drop of oil output. The test shows that the lower pay zone has no output, which causes great economic losses and brings great difficulties to the exploitation of oil and gas resources. Aiming at the problems of insufficient plugging performance, poor reservoir protection performance, difficulty in self-plugging removal, and environmental protection of the existing workover fluid system in Weizhou Oilfield, an environment-friendly self-degradable polymer film workover fluid system was developed, and the formula was seawater + 1% Dristemp + 3% film-forming agent + 2% bionic inhibitor + 3% super-amphiphobic agent. The system has high temperature stability, good pressure-bearing and plugging performance and water blocking resistance, and can effectively protect the reservoir. In addition, through the environmental protection performance test, it is determined that the formula has excellent characteristics of safety, non-toxicity, and no environmental pollution.