Application of coiled tubing withdrawing acidizing with diverting acid system in Ahdeb oil field, Iraq

Ahdeb Oilfield is the first oilfield reconstructed after the Iraqi War and mainly developed by long-lateral horizontal wells in linear well pattern. The wells, with a horizontal section of 800-1 000 m, face strong heterogeneity, and uneven acid distribution etc. in the process of acidizing. In view of these problems, the following measures were taken to assist effective acid distribution: CT was withdrawn continuously from high to low velocity along the whole horizontal section. Diverting acid system was used to help equalize acid distribution. The jetting nozzle was adopted to remove deep damage caused by the drilling fluid and completion fluid and improve acid penetration in relatively low permeability section. In the past 3 years, over 90 horizontal wells were stimulated with viscoelastic diversion acidizing, oil production of individual wells has increased by more than 1.4 times after acidizing, and cumulative oil production increment reaches 88.9×104 ton.