Research and Evaluation of a New Autogenic Acid System Suitable for Acid Fracturing of a High-Temperature Reservoir.

An organic ester p-nitrobenzyl acetate (PNBA) was synthesized and used to establish a kind of autogenic acid system through the hydrolysis of ester to acetic acid in situ. The autogenic acid system can form a homogeneous solution by adding an organic solvent. The autogenic acid system possesses the desired characteristic in which hydrolysis can generate a small amount of acetic acid below 120 degrees C and a large amount of acid above 140 degrees C in 2 h. The acid-generated ability at different time and temperature was studied in detail. The dissolution of solid calcium carbonate and carbonate rocks by the autogenic acid system was investigated. The autogenic acid displayed lower dissolution ability on a carbonate rock and weak corrosion of a N80 steel sheet at 150 degrees C. The autogenic acid is especially suitable for acid fracturing and dissolution of rocks in a high-temperature carbonate reservoir.