Technology of re-acidizing Well GX-3 by temporary plugging with fuzzy-ball fluid

In 2002, Well GX-3 was acidized and put into production, and its production decreased normally to 5×104 m3/d in 2014, so it is proposed to re-acidize the well in order to increase production. For the purpose of improving the effectiveness of re-acidization, the fuzzy-ball temporary plugging fluid was used to plug the originally acidized wormhole of high conductivity, hence forcing the acid solution to enter the non-acidized formations. Indoor tests show that, after plugged by fuzzy-ball fluid, the bearing capacity of previously acidized wormhole of high conductivity was improved by 78.06 MPa, the changes of plastic viscosity and yield point of temporary plugging fluid with pH 2 to 7 was below 3%, and the recovery of the permeability of originally acidized wormhole of high conductivity was 88.64%. 120 m3 of fuzzy-ball temporary plugging fluid was prepared on site to plug the originally acidized wormhole of high conductivity. The density of such fluid was 0.90~0.95 g/cm3, its plastic viscosity was 15~30 mPa·s and its yield point was 15~35 Pa. Wellhead was tested with a pressure of 3 MPa, 6.5 m3 of hydrochloric acid was injected, then the residual fluid was produced after standing for 7 h. When production was resumed, the gas yield was increased from 5×104 m3/d to 7×104 m3/d, indicating that acidization occurred after the fuzzy-ball fluid plugged the high-conductivity wormhole previously acidized, which did not damage the gas productivity of original fractures and instead added new gas producing layers, hence providing a new and effective method for re-acidification of carbonate reservoirs.