Acid Fracturing Modification of 180 ℃ High-temperature Carbonate Rock Reservoirs Using Gelled Acid and Its Application

The Engineering Technology Department of Southwest Oil and Gas Field Company has a large number of high-temperature wells in the northern slope of the central Sichuan ancient uplift and the lower Permian in western Sichuan, with some wells reaching a bottom temperature of 180 ℃ or above. The performance of acid fracturing working fluid and its applicability to reservoirs are prerequisites for successful stimulation. In response to the problem that existing acid solutions cannot effectively meet the requirements of deep high-temperature reservoir acid fracturing transformation, a high-temperature resistant carbonate rock reservoir acid fracturing transformation cementitious acid system has been developed, and its comprehensive performance evaluation and on-site testing have been conducted. The performance evaluation and on-site test results show that the resistance reduction rate of the gelling agent (0.5%) used in gelling acid is 75%; The corrosion rate of cementitious acid on N80 specimens at 180 ℃ is 30-45g/m2 • h; After continuous shear at 180 ℃ and 170 s−1 for 60 min, the viscosity of the gelled acid remained at 20.0 mPa • s; After aging at 180 ℃ for 4 h, the gelled acid remained homogeneous and did not show any precipitation, residue, or stratification. The retarding rate of gelling acid is 70% of that of conventional acid. These properties are beneficial for reducing construction difficulty and risks, achieving deep penetration into reservoirs, forming longer acid corrosion fractures, and achieving deep transformation and effective production increase. Cementitious acid has been successfully applied in high-temperature carbonate rock acid fracturing sites. Meet the acid fracturing transformation requirements of 180 ℃ carbonate rocks.