Pickering Emulsified Acid Systems (PEAS): A Promising Approach for Reduced Drag in Matrix Acidizing.

Matrix acidizing is a widely employed stimulation technique that enhances well productivity in carbonate reservoirs by dissolving formation damage and creating conductive channels known as wormholes. Conventional hydrochloric acid (HCl) systems, while effective, suffer from limitations such as high corrosivity, excessive reactivity, and poor thermal stability. Emulsified acid systems (EAS) have emerged to address these drawbacks by introducing an oil phase that slows the acid-rock reaction and facilitates deeper penetration. However, the high viscosity of surfactant-based EAS leads to increased pumping resistance and energy consumption. This study introduces a Pickering emulsified acid system (PEAS) formulated using organoclay (OC) nanoparticles as solid-particle emulsifiers to overcome these limitations. PEAS exhibits enhanced thermal stability, compatibility, and drag-reducing characteristics due to the rheological behavior and lubricity of OC. Comparative flow-loop tests with 15% and 20% HCl revealed significantly lower frictional pressure drops for PEAS than traditional EAS across a range of temperatures (25-50 °C). Postflow characterization including conductivity, stability, and rheology analyses confirmed the structural robustness and field-relevant performance of PEAS. These findings position PEAS as a promising, environmentally friendly fluid system for improving acid placement, enabling efficient wormhole formation and reducing the energy footprint of matrix acidizing operations.