Field-Wide Evaluation of HCl and Viscoelastic Diverting Acid Systems for Carbonate Matrix Acidizing: Integrated Laboratory, Simulation, and Multi-Well Case Study

This study presents a comprehensive, field-scale evaluation of matrix acidizing treatments performed on four carbonate gas wells in southern Iran, integrating laboratory optimization, predictive simulation, and standardized field execution. The acid systems—comprising 28 wt% hydrochloric acid (HCl), 15 wt% viscoelastic diverting acid (VDA), and tailored additive packages—were systematically designed through dissolution capacity, emulsion compatibility, corrosion resistance, iron control, and H₂S scavenging tests under reservoir-simulated conditions. Numerical simulations guided the design of injection rates, stage volumes, and diversion sequences, ensuring acid placement efficiency while maintaining operations below fracture pressure. Field application delivered substantial performance gains, including gas production increases of up to 100%, wellhead pressure improvements of up to 84%, and skin factor reductions from as high as 5.0 to as low as −2.3. The thermo-reversible gelation behavior of VDA enabled effective diversion into low-permeability zones, promoting uniform wormhole distribution and enhanced reservoir contact. Post-treatment, Basic Sediment and Water (BS&W) content decreased significantly, further improving produced-fluid quality. Unlike conventional single-well analyses, this study offers a rare multi-well perspective, demonstrating the scalability, repeatability, and robustness of a unified HCl–VDA workflow in high-temperature, sour, and heterogeneous carbonate formations. The findings provide a transferable framework for optimizing acid placement and achieving predictable stimulation outcomes in similar carbonate reservoir settings worldwide.