Development and evaluation of authigenic acid system in high-temperature carbonate reservoirs

Abstract

Acidizing the carbonate reservoirs with the conventional acidizing liquid system always causes fast acid-rock reaction and short acidizing distance, and the productivity of oil wells is not significantly improved. The key to improve the acidizing effect in the deep carbonate reservoirs is to optimize the retardation performance of the acid system. The authigenic acid system provides the excellent retardation performance and long acid-rock reaction due to its characteristics of slow and continuous acid generation. Here, an authigenic acid system with the performance of stable and continuous acid generation at high temperature was developed with halide salt, carbonyl compounds and esters. The authigenic acid system provides the excellent acid generation performance, with 12.9% hydrochloric acid generated after reaction at 90°C for 6 hours and 18.9% hydrochloric acid generated after reaction at 150°C for 6 hours. Comparison of hydrochloric acid, viscous acid and authigenic acid by experiments of static corrosion in rock cores shows the longer acid-rock reaction time of the authigenic acid than that of the conventional acids. At 150°C, N80 steel sheet is corroded in the authigenic acid system at the rate of 0.984 gm·−2·h−1, which is lower than the industrial first-class standard and indicates excellent corrosion inhibition performance. Comparison of the acid-rock reaction kinetic equation of hydrochloric acid, authigenic acid in the carbonate rocks shows that the authigenic acid has the acid-rock reaction rate which is an order of magnitude lower than that of the conventional acid and has the better retardation performance, and it can be used to solve the difficulties in the deep acidizing of high-temperature reservoirs.