Emulsified acid consists of two phases—the acid phase and the oil phase—with the acid phase encapsulated by the oil phase. This structure effectively blocks the diffusion and migration of H⁺ ions, slows down the reaction rate between the acid and rock formations, and thereby extends the acid’s penetration distance. It is particularly suitable for deep acid stimulation and enhanced oil recovery (EOR) operations in low-permeability carbonate reservoirs. Meanwhile, emulsified acid has higher viscosity than neat acid, which can effectively reduce acid filtration loss and ensure uniform distribution of the acid in heterogeneous formations during carbonate reservoir treatment.
At present, the channel flow theory is a widely recognized mechanism for the selective acidizing of emulsified acid. Rock surfaces in oil-water channels exhibit different wettabilities: those in long-term oil-flowing pores adsorb natural active components from crude oil, showing obvious oil-wet and water-repellent properties. In contrast, long-term water-flowing pores undergo hydroxylation, carry negative charges, and present distinct water-wet and oil-repellent characteristics, resulting in the oil and water phases flowing along their respective interconnected channels. Therefore, for water-bearing oil wells, conventional water-based acidizing operations often lead to an increase in the water cut of oil production while achieving unsatisfactory oil increment effects. Additionally, the acid in water-based acidizing fluids directly contacts the rock formation, leading to an excessively fast reaction rate between the acid and the rock, a short penetration distance, and thus affecting the acidizing efficiency.
Post time: Dec-10-2025