Enhanced Carbonate Reservoir Stimulation Using a Novel Emulsified Acid: Core Flooding and Micro CT-Scan Validation

Abstract In carbonate reservoir stimulation, achieving controlled acid reactivity is critical to prevent rapid acid spending and ensure deeper penetration into the formation. Acid retardation slows the reaction between acid and rock and helps extend the contact time, resulting in more uniform dissolution and enhancing the stimulation effect. Emulsified acid systems offer an effective way to achieve this by encapsulating the reactive phase within a non-reactive continuous phase, delaying the acid release and reducing premature reaction near the wellbore. This study investigates the performance of a Novel Emulsified Acid (NEA) system designed to improve acid penetration, control reaction kinetics, and minimize formation damage compared to conventional acid systems. The NEA formulation was evaluated through core flooding experiments, with structural alterations validated using Micro CT-Scan imaging. The system consists of hydrochloric acid as the reactive phase, stabilized within a Non-Aqueous Phase (NAP) as the continuous phase to delay reactivity and extend acid contact time. Unlike traditional emulsified acids, NEA employs an optimized NAP formulation for enhanced stability and retardation. Emulsion stability is further reinforced by an emulsifier, which helps stabilize the system, along with additives that serve as polymer stabilizers and metal-binding agents (chelating agents). Core flooding experiments demonstrated that NEA significantly improves reservoir characteristics by enhancing porosity and permeability, and by generating more efficient wormholes compared to using conventional acid systems. Micro CT-Scan imaging confirmed the formation of well-connected flow paths, validating the effectiveness of NEA in optimizing acid penetration and rock dissolution patterns. These findings demonstrate the potential of NEA as a superior stimulation fluid for unlocking untapped productivity in complex carbonate formations. Future field-scale implementation is planned as a continuation of this laboratory-scale experiment to validate performance under real reservoir conditions.