Abstract
Successful matrix acid stimulation treatments require careful downhole placement and optimal zonal coverage. The acid must enter the zones with the highest permeability and/or lowest skin to maximize its effectiveness. Without proper fluid diversion, the acid tends to flow into the least damaged zones, leaving the most damaged zones undertreated. To achieve a skin factor on the order of −3 to −4, an effective diversion technique is crucial to ensure complete zonal coverage and remove damage throughout the producing interval.
This paper presents a modified matrix acidizing treatment explicitly developed for the fractured carbonate reservoir in the Gulf of Suez basin in the Eastern Desert of Egypt. The challenge was to treat the lower-permeability matrix while achieving a well-defined acid distribution between the flow zones of the natural fractures and the unfractured matrix, given the significant permeability contrast of 130:1.
Extensive experimental and laboratory tests were conducted to prepare a viscous pill that temporarily isolated the fractures or fissures network prior to the full acid treatment. Additionally, a passive diverter was employed instead of an active acid-based diverter, effectively diverting the acid away from each zone after pumping. The results of these novel diversion techniques demonstrated a remarkable sixfold increase in well productivity. The post-treatment evaluation, falloff analysis, and comparison with production logging and core analysis further supported the efficacy of the temporary isolation approach, particularly in treating the lower-permeability layers that are the primary target for matrix acidizing.
This paper showcases the applications and laboratory tests of this unique recipe and cost-effective diversion technique in fractured carbonate reservoirs and shares valuable lessons learned during the applications. The ultimate goal is to provide a comprehensive recipe that can be utilized worldwide, offering practical solutions for maximizing production and reservoir potential in similar reservoir environments.
