Application of a New Integrated Variable-Viscosity Retarded Acid in Carbonate Reservoir Stimulation

Owing to the fact that carbonate reservoirs in the Sichuan Basin are buried relatively deeply, there are generally poor physical properties of the reservoirs, such as high temperature, low porosity and low permeability, underdeveloped dissolved pores and cavities, high closure stress, great difficulty in deep stimulation, and difficulty in maintaining the conductivity. These factors make the deep stimulation extremely challenging. Aiming at the above problems, this paper optimally selects an integrated variable-viscosity retarded acid. Through laboratory experiments, its compatibility performance, variable-viscosity performance, corrosion performance, drag reduction performance, temperature and shear resistance performance, and retarded reaction performance are evaluated, and a comparison is made with the conventional acid fluid system. The experimental results show that compared with the conventional acid fluid system, this acid fluid system has better reservoir adaptability. When the temperature is 160 ° C, compared to the conventional gelled acid system, the acid-rock reaction rate of this acid fluid system can be decreased by as much as 26%. Meanwhile, its temperature and shear resistance performance shows an improvement of around 110%. In addition, this acid fluid system has achieved good stimulation effects in field applications. Compared with the conventional gelled acid, the construction displacement is increased by about 70%, the acid fluid has a better fracture creation effect, a lower drag reduction rate, and a better deep stimulation effect.