Gasified acid solution in pre-transition state for well stimulation

In this paper, a new class of fluids is considered, which are single-phase gas-liquid mixtures in the pre-transition state. The mentioned single-phase mixture is a liquid with precritical gas bubbles of nanometer size. The stability of nanobubbles can be increased by introducing surfactants into the gas-liquid mixture. The rheology of a gasified acid solution in a pre-transition has been studied. Based on the conducted research, the method of treating the wellbore zone with a gasified acid solution in a pre-transition state is proposed in order to increase the efficiency of acid treatment. The introduction of a cationic surfactant (0.1%) promotes hydrophobization of the pore walls and slows down the reaction between rock and acid. Improved filtration of single-phase gasified acid solution in pre-transition state increases liquid flow rate at constant pressure drop and reduces the consumption of gaseous agent. The effective viscosity of the gasified acid solution in the pre-transition state is 10 times lower than that of the non-carbonated acid solution. The resulting gasified acid solution flows uniformly into zones of varying permeability, increasing the treatment coverage through both the formation thickness and its depth. Compared to existing acid treatment technologies, such as the use of foam acid and viscoelastic surfactant-based systems, the gasified acid solution in the pre-transition state has a penetration capacity of 40-70% and a coverage factor of 100% higher. In order to reveal the effect of gasified acid solution in pre-transition state on the porous medium, the COMSOL Multiphysics simulation was used.