Optimizing the Use of Dissolvable Plugs in Acid Fracturing Through CFD Simulation and Field Validation

Abstract Acid fracturing has gained prominence as an effective technique for stimulating challenging formations, such as bauxite, which require higher pressures to break. Dissolvable plugs are often the only viable option for fracturing intervals where casing deformation or inaccessibility by coiled tubing pose significant challenges. However, conventional dissolvable plugs, typically made of magnesium (Mg) or aluminum (Al) alloys, react aggressively with acidic fracturing fluids. Developing coatings that delay reactions while still allowing complete dissolution is highly challenging due to the variability of downhole conditions. This study employs computational simulation and field trials to establish reliable operational practices for using dissolvable plugs in acid fracturing by minimizing direct exposure to highly acidic environments. Typical acid fracturing procedures and well structures were systematically analyzed. Using Computational Fluid Dynamics (CFD) modeling, the evolution of the chemical environment within the "dead zone"—the area between the plug and perforation holes—was simulated to assess acidity changes over time and distance. The effect of dead zone length on the plug's exposure to acidic conditions was quantified, and a minimum safe dead zone length was determined. The effectiveness of this approach was validated through multiple field case studies. CFD simulations revealed that fresh water trapped in the dead zone can significantly slow the diffusion of acidic fracturing fluids toward the plug area, redirecting the majority of the acidic fluid through the perforation holes into the reservoir. A dead zone length of 7 mm was identified as sufficient for most acid fracturing applications. Field tests with this configuration confirmed that conventional dissolvable plugs remained intact and functional without premature degradation, validating the simulation results. This is the first report detailing a practical and effective operational method for safely using conventional dissolvable plugs in acid fracturing without risk of early failure. By eliminating the need for specialized, highly engineered dissolvable plugs with complex designs and expensive materials, this approach significantly reduces the cost of acid fracturing operations. Additionally, the simulation insights provide a clear understanding of wellbore chemical evolution, offering operators valuable guidance for optimizing acid fracturing processes and designing tools to maintain well integrity and improve efficiency.