Workover technology using fuzzy-ball temporary plugging fluid in Bohai Oilfield

Trial use on two wells shows that the fuzzy-ball temporary plugging fluid can address the problem of lost circulation during workover in Bohai Oilfield, but its properties and operation process need to be further optimized. Experiment shows that the plugging depth is 0.1m, so effective sealing can be realized without injecting too much fluid into the formation in order to create a deeper plugging belt. The plugging capability of fuzzy-ball temporary plugging fluid has nothing to do with its density. The thief zone with low pressure can be plugged by such fluid with 20~30 mPa·s plastic viscosity and 0.7~1.1 Pa/(mPa·s) rate of dynamic shear force. Leak test was conducted using standard formation water after being plugged by fuzzy-ball temporary plugging fluid, the bearing capacity of the formation was up to 25.64 MPa, showing that the thief zone can be plugged without whole well circulation. After successful pilot test on whole well slug in onshore S181 Gaswell, the slug was trial used in reservoir section in Well A in Bohai Oilfield, indicating that the fuzzy-ball temporary plugging fluid can be used in workover operation by plugging the reservoir with the slug.