Optimizing Stimulation Efficiency in Large Volume Foamed Acidizing Treatments in Tight Carbonate Formations

Block 5, located in the northern region of the Sultanate of Oman, is a mature oilfield that continues to face challenges in sustaining economic production levels despite the application of horizontal well technology to maximize reservoir contact. While drilling campaigns have delivered mechanical success, a significant proportion of wells remain underperforming due to the inherently tight nature of the carbonate formations and damage associated with completion and workover operations. Stimulation is therefore essential to restore productivity; however, the complexity of treating long open-hole horizontal sections in tight formations has historically necessitated high capital expenditure solutions. To address these challenges, Large-Volume Acidizing (LVA) with foamed diversion has been adopted as a cost-effective alternative to conventional multistage stimulation systems, eliminating the need for coiled tubing intervention and complex completion hardware. Since its implementation in 2017, the LVA program has undergone progressive optimization in acid type, diversion techniques, and placement strategies, supported by advanced stimulation modeling. Recent advancements in the 2025 campaign include the introduction of a next-generation Single-Phase Retarded Acid (NG-SPRA) system, providing enhanced wormhole propagation, extended thermal stability, and reduced frictional pressure losses. In parallel, high-frequency pressure monitoring (HFPM) was incorporated into the treatment workflow to enable evaluation of diversion effectiveness, cluster coverage, and acid placement, allowing dynamic operational adjustments without additional intervention complexity. Field implementation of this integrated approach has demonstrated significant benefits. Initial post-stimulation oil rates exceeded three to four times the pre-treatment levels, with normalized productivity indices surpassing those achieved with previous-generation acid systems under comparable reservoir conditions. The combined NG-SPRA and HFPM methodology has delivered up to 85% cost savings relative to multistage completion alternatives while improving stimulation efficiency and lateral coverage. The results from Block 5 illustrate a transferable, field-proven workflow for cost-efficient carbonate stimulation in long-reach horizontal wells, offering applicable best practices for similar reservoirs within Oman and analogous carbonate settings globally.