Application of acid fracturing technology with visco-elastic surfactant acid in Tahe Oilfield

During the acid fracturing in Ordovician reservoir in No.3 block of Tahe Oilfield, fracture height grew to connect lower water zone resulting in rapid watercut growth and waterflood breakthrough during later production. To improve acid fracturing effect and control water production after fracturing, visco-elastic surfactant acid technology was developed. When the visco-elastic surfactant in acid contacts with salt compound, very high viscosity can be obtained; but when contacts with hydrocarbons, viscosity will reduce due to degradation, which is beneficial to flow back. This acid is featured by automatic diverting and water control function, which was applied in well TK332 successfully, with early oil production of 30 m3/d, gas rate of 1.9×104 m3/d and no water production after stimulation. It is found that diverting acid is not suitable for high displacement operation and displacement at ~3 m3/min is better. Successful application of the technology provides good reference for similar operation.