Sustainable approach for generating emulsified acid system for matrix acidizing in carbonate reservoirs

Conventional emulsified acid systems (EASs) for carbonate matrix acidizing are commonly prepared by batch, high-shearing mixing, which can be operationally cumbersome at the field scale and yield unstable emulsions when corrosion inhibitors and other chemical additives reduce turbulence during mixing. A sustainable method for the inline preparation of emulsified acid systems (EAS) was developed to improve matrix acidizing in carbonate reservoirs. The process integrates a liquid–liquid ejector with a two-stage centrifugal pump featuring perforated vanes, enhancing emulsification and scalability for bulk production. The prepared EAS was successfully tested for conductivity and thermal stability, confirming its formation as a water-in-oil invert emulsion (70% of acidic and 30% of diesel phases) with stable properties. Core flooding experiments were conducted using a tight Indiana limestone sample under reservoir conditions (90 °C and 3000 psi back pressure) to evaluate the effectiveness of the prepared EAS in creating wormholes for enhanced acid penetration. Thermal stability tests showed no visible phase separation for 24 h up to 75 °C, and core flooding produced a dominant wormhole increasing permeability from ∼8 mD to ∼3 D. The results demonstrated that the commercial EAS formulation, which contains a corrosion inhibitor and other additives, acts as a drag reducer. Consequently, increased turbulent mixing is required to achieve and maintain diesel as the external phase and prevent phase inversion. The optimized preparation method, incorporating a centrifugal pump at the ejector's discharge line, significantly improved mixing efficiency and emulsion stability regardless of water salinity. These findings offer a viable and scalable solution for field applications, alleviating the operational challenges of the traditional EAS preparation method and enhancing the effectiveness of matrix acidizing in high-temperature carbonate reservoirs.