Research Progress on Retarded Acid for Carbonate Reservoir Stimulation

This paper systematically reviews the research progress of composite retarded acid systems in the stimulation of carbonate reservoirs. Addressing challenges such as the strong heterogeneity, high temperature, and high pressure of carbonate reservoirs, which lead to issues like fast reaction rates of conventional acids, short effective distances, and uneven stimulation effects, the paper focuses on the mechanisms of retarded acidizing technology for deep reservoir modification through controlling acid-rock reaction kinetics. It provides a detailed analysis of the reaction characteristics of five typical systems: conventional acidizing, emulsified acid, diverting acid, gelled acid, and retarded acid. Emulsified acid achieves retardation through oil-phase encapsulation but faces difficulties in demulsification; diverting acid relies on viscosity changes for diversion but involves complex processes; gelled acid uses high viscosity to reduce fluid loss but encounters challenges like high injection pressure and difficult flowback; retarded acid inhibits reactions by surfactant adsorption and film formation, yet its performance is susceptible to environmental factors. The study indicates that current retarder development is advancing towards green, efficient directions characterized by temperature and acid resistance, low damage, and easy flowback. Future research needs to deepen the understanding of retardation mechanisms in multiphase flow systems and optimize formulation design and operational practices to achieve precise matching between acid fluid performance and formation conditions, thereby providing theoretical support for the efficient development of carbonate oil and gas fields.