Achieving Successful Diversion in Acid Stimulation Treatments: Case Study of Excellent Results Achieved Using Associative Polymer Treatment (APT) in Highly Heterogeneous Carbonate Reservoirs in Saudi Arabia

摘要

An effective diversion technique is a critical component in all acid stimulation jobs, which enables us to achieve full zonal coverage and thereby achieve the treatment objectives. The highly heterogeneous multilayered nature, and the high temperature and pressure condition of the carbonate reservoirs in the Saudi Arabian gas fields, pose a significant challenge in the ability to achieve effective diversion. Associative polymer technology (APT), which is a very low viscosity aqueous-polymer solution designed for optimum diversion was successfully field tested during acid matrix treatments pumped in three new gas producers. The treatments comprised an organic acid blend, retarded acid and associative polymer diverting fluid, and were pumped in perforated intervals up to 264 ft. The diversion and acid reaction signatures were clearly shown in the acquired surface and bottom-hole pressure (BHP) plots for all respective stages, thereby indicating a successful diversion. A post-stimulation pressure buildup (PBU) test conducted in one well showed a skin of -4. Production testing (PLT) surveys conducted in two of the treated wells showed flow contribution from all targeted pay zones, and a net gas rate gain of up to 40% was recorded. This paper will discuss the rationale for selecting APT, acid fluid design and optimization, treating pressure behavior, and post-treatment results and diagnostic data, which confirm the effectiveness of the associative polymer as a diverting agent.