Research of liquid system selection technology of Sinian system reservoir stimulation in Sichuan Basin

The reservoir of Gaoshiti-Moxi structure of Sinian system in Sichuan Basin has the characteristics of high temperature, deep buried, fractured-vuggy development and strong reservoir heterogeneity. The acid fluid system and formula selection is one of the key factors to stimulate the reservoir and increase production. Combined with the characters of Sinian system, the technical difficulties of reservoir stimulation were analyzed, the acid liquid system performance experiments were carried out, and results showed that:①The filtration performance of gelled acid and VES acid is good, and the filtration coefficient is about 10^-4-10^-5 level; ②the friction resistance of gelled acid and cross-linked acid is low, the average friction coefficient is 0.377 7 and 0.366 4 for each acid; ③the acid-rock reaction rate of gelled acid and cross-linked acid is low, and the average reaction rate is about 10^-5 level; ④the VES acid can treat the 40 times permeability cores diverting successfully, and the most variable viscosity can reach 70 mPa·s; under 150 ℃ for 2.5 h, the degradable fiber can degrade completely, the injection pressure can achieve 3.2 MPa in the test. Finally, the acid system optimum principles have developed based on four types of reservoir characteristics, and the optimized acid systems have successfully applied in Sinian system reservoir.