An Uneven Acid Injection Technology for Long-Lateral Horizontal Wells in Complex Carbonate Reservoirs: Simulation, Optimisation and Practice

Focusing on the characteristics of long horizontal interval (>800m) and strong heterogeneity of complex carbonate reservoir, this paper puts forward a high efficiency uneven acid distribution technology, consequently solving the problems of high large scale and financially-challenged acidizing result. It takes the damage profile in productivity established stage or liquid production profile in the stable production stage for horizontal wells as the designed core, and selects optimal injecting point and interval in the long-interval horizontal well to maximize stimulation effect with minimal acid. This paper establishes an integrated mathematical model for the quantitative analysis of non-uniform damage of horizontal well simulated acidizing diverting and the acid-etched wormholes propagation for complicated carbonate reservoir. Besides, the matching technological methods and strategies, such as whole or local selective acid injection using coil tubing, inert liquid injection in the annulus, and the secondary segmented acidizing displacement, were presented. This technology has been applied in the AHDEB and HALFAYA oilfield, completing 296 wells acidizing treatments. The results demonstrated that the average acidizing volume decreased from 500-900m3 to 150m3 and production significantly increased.