Development and Experiment of Low-Density and Solid-Free Foam Workover Fluid for Low Pressure Gas Reservoir

For low production, high fluid loss, and low pressure gas formations, the application of conventional workover fluid may result in drainage difficulties, formation damage and production recovery. A low density and solid-free foam workover fluid was developed by adding high effective amphoteric ionic foaming agent and foam stabilizer in the circulating foam drilling fluid to make it form micro bubble materials with a special structure. Its density is between 0.50 and 0.95 kg/L, viscosity is less than 90 mPa·s, and stabilization time is 24 h under 100 ℃. Comprehensive experimental results indicated that the kind of workover fluid has a slight damage to payzone, with low filtration rate and good plugging effect, the influence of temperature and pressure on the workover fluid is not serious. Its application in Well Ba-II Xi 80104 of Xinjiang indicated that this bubble workover fluid performed very well to ensure smooth completion and workover operation and might be used in high fluid loss, strong water-sensitive, and water lock low pressure gas reservoirs.