Correlation between micellization and esterification processes in non-aqueous surfactant-containing compositions potentially applicable for organic-rich rocks treatments

This article is concerned with study of surfactants' influence on the properties of developed hydrocarbon-based intensifying compositions, potentially applicable in complex reservoirs with a high content of rock-forming organic matter, including Bazhenov Formation (Western Siberia, Russia). These compositions consist of acetic acid, isopropanol, isopropyl acetate (product of the esterification reaction between acid and alcohol directly in the composition volume), and an aromatic solvent – composition base. Also, surfactants are important components of chemical compositions for rock treatments (for example, for acid treatments). Their presence promotes increasing of the detergency effect on hydrocarbon components and slows down the intense interaction of the acidic component of compositions with minerals. It is known that surfactants in solutions are inclined to micellization, furthermore, a hydrocarbon medium promotes the formation of reverse micelles. The most important function of such structures is their ability to have a reversible process of solubilization of polar components from solution into the core, making them inactive. It has a huge impact on the resultant content of compositions’ components and, as a result, on the final properties of these systems. Behavior of formed reverse micelles of different types of surfactants in compositions was studied by determining their interstructural and local transformations using the viscosimetry method under conditions of millimeter-scale pores. It has been shown that the features of local transformations of micelles influence the esterification reaction between acid and alcohol. It has been established that the amount of formed ester and functions of intensifying systems vary depending on the type and concentration of surfactant. The results obtained will help to realize a more accurate choice of composition formulations depending on the mineral composition of rocks and the content of various hydrocarbon compounds in rock-forming organic matter. • Complex hydrocarbon-based intensifying compositions with the possibility of obtaining an additional detergency agent (ester) in-situ directly in compositions are proposed as potentially applicable to well stimulation from organic-rich rocks; • Properties of complex intensifying systems for organic-rich rocks depend on changes in the micellar structures of surfactants at different concentrations; • Concentrations and ratios of various compositions' components affect the amount of isopropyl acetate obtained in-situ; • Based on studying viscosity characteristics of compositions and their relationship with esterification reaction, optimal concentrations of surfactants can be selected under conditions of millimeter-scale pores