Feasibility of Dynamic Acid Corrosion Control in Oil Well Tubing

Abstract

Matrix acidizing operations are regarded as one of the most important and familiar operations in Iraqi oil wells. These operations are carried out in a routine way, injecting 15% hydrochloric acid with 1% ACI (the acid corrosion inhibitor used with HCl acid in southern Iraq) for stimulation of carbonate formation. Since oil production was started in Iraq, the acidizing jobs have been carried out using the above concentration. In spite of the experience in performing the acidizing jobs in the southern part of the Iraqi oil fields, it has been found that the above concentration of ACI is high for 15% HCl. An experimental study has been carried out to investigate the corrosion in oil well tubing, which is of great importance in well acidizing operations, to establish a successful acid corrosion control in oil well production tubing. The investigation was carried out on coupons of three types with two different concentrations of hydrochloric acid (15%, 28%). The investigation was extended to cover the effects of the following: (1) volume of acid (milliliters)/area of test coupon (square inches), VIA; (2) agitation of acid; (3) effective contact time; (4) concentration of ACI (acid corrosion inhibitor). Comparison of static and dynamic tests was covered in this work. It is found that as VIA increases, acid corrosion rate decreases for all values of ACI concentration to a certain limit, and also that increasing the effective contact time increases the rate of corrosion. The study proves the importance of dynamic conditions which depict real or actual field circumstances.