Development and application of acid fluid system for acid fracturing of high-temperature carbonate reservoirs

In the reformations of fractured and vuggy reservoirs in the Tahe Oilfield, acid fluids and rocks reacted rapidly under high temperatures, and the filtration amount was large. Conventional acid fluid systems failed to realize deep reformations and to improve the conductivity of acid-etched fractures. Thanks to years of laboratory experiments and field tests, multiple sets of acid fluid systems including gelled acid, variable viscosity acid, steering acid and surface cross-linked acid were proposed. Through the analyses and comparisons of high-temperature rheological curves, different acid fluid systems were chosen according to different reservoir types. They were used to guide acid liquid selection and to improve technique in single well, and had obtained good application effects.