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Enhanced oil recovery in mature fields can be implemented using chemical flooding with the addition of surfactants using surfactant-polymer (SP) or alkaline-surfactant-polymer (ASP) flooding. Chemical flooding design is implemented taking into account reservoir conditions and composition of reservoir fluids. The surfactant in the oil-displacing formulation allows changing the rock wettability, reducing the interfacial tension, increasing the capillary number, and forming an oil emulsion, which provides a significant increase in the efficiency of oil displacement. The article is devoted with a comprehensive study of the formed emulsion phase as a stage of laboratory selection of surfactant for SP or ASP composition. In this work, the influence of aqueous phase salinity level and the surfactant concentration in the displacing solution on the characteristics of the resulting emulsion was studied. It was shown that, according to the characteristics of the emulsion, it is possible to determine the area of optimal salinity and the range of surfactant concentrations that provide increased oil displacement. The data received show the possibility of predicting the area of effectiveness of ASP and SP formulations based on the characteristics of the resulting emulsion.

The purpose of the article is the search and development of water-soluble chemicals for the successful drainage and impregnation of low-permeable shale oil formations. The main problem for shale oil deposits is ultra-low water permeability. We are dealing with the cores of the Bazhenov formation, which have permeability of 10 mkD, nano-porous matrix with natural cracks. In the paper we have collected and examined the mechanisms that prevent water from penetrating into core samples with low permeability, and suggest chemicals that can help overcome this problem. Complexes of different surfactants, polysurfactants, nanoparticles with modified surface were investigated. Wettability, interfacial tension measurements, adsorption, micelles formation and phase behavior experiments were held in order to select the most effective chemical agent. A "funnel" of experimental search was performed and two best surfactants and composition of surfactant with nanoparticles was figured out. Then, for the first time, displacement experiments were carried out through the consolidated core samples of the Bazhenov formation, and the displacement efficiency of 53% was obtained. Due to the fact that the injection pressure turned out to be very high, and there were also problems associated with the adsorption of surfactants. The further steps to improve the experimental study were discussed.