Advanced Modeling and New Fit for Purpose Fluids Unlock Potential of Hot Carbonate Reservoirs During Acid Fracturing in Uzbekistan

Abstract

Selection of the optimum production stimulation strategy depends on the given reservoir and well parameters, with their uncertainties. This study proposes reservoir property-dependent profitability (RPDP) plots as a tool for stimulation treatment type selection. These plots helped to define acid fracturing as an optimum stimulation strategy for hot carbonate reservoirs, which are described in case studies. The presented case studies describe implementation of an advanced approach to acid fracturing design and execution. The advanced approach consists of three key components. First is use of a single-phase retarded acid to achieve longer etched fracture half lengths, decrease volume of the treatment, and mitigate the potential for anhydrite precipitation. The second component of the approach is employing linear gel as a pad to minimize water breakthrough risks but, at the same time, provide adequate viscosity during the fracturing process. The third component is implementation of an advanced acid fracturing simulator, which can model complex acid-rock interaction and transport processes. The combined advanced acid fracturing approach was applied to the design and execution of 15 acid fracturing jobs in Uzbekistan. Post-treatment production results showed that 300% productivity index (PI) increase was achieved for the entire set of wells. In comparison with the existing standard approach, the same PI increase was achieved with 70% less fluid pumped, and water breakthrough risk was successfully mitigated by optimization of fluid volumes in an advanced fracturing simulator.