Development and Application of an Adsorptive Retarded Acid

Conventional acids for acidizing job have some disadvantages such as fast reaction, short effective functioning distance and poor erosion etc. To address these problems encountered in acidizing with conventional acids, an adsorptive retarded acid was developed, in which the hydrophobic cationic groups of the retarder are able to adsorb on the surfaces of formation rocks, forming a protective membrane to shut off the contact of H+ and the surfaces of the rocks, thereby retarding the reaction between acid and rocks, and increasing the length of acid-corroded fractures and the inhomogeneity of acid corrosion. A retarded acid formulation was developed based on the optimization acid concentration and the concentration of other additives. Evaluation of the performance of the retarded acid showed that the acid was retarded by 91.2% and the rate of corrosion was retarded by 99.6%. Reaction of the retarded acid and rocks produced clear ditches and trenches, and the flow conductivity of the ditches and trenches drops at a low magnitude as enclosure pressure is increasing, fully proving the retarding capacity of the retarded acid. This retarded acid has been successfully used in Sulige gas field, the daily gas production rate of an individual well was 5 times that of gas wells nearby.