Abstract
The article considers the influence of seawater and surfactants on interfacial processes in the “oil–water–rock” system and their impact on oil displacement efficiency under the conditions of the Kashagan carbonate reservoirs. The relevance of the study is associated with the high salinity of formation waters, complex thermobaric conditions, heterogeneity of carbonate rocks, and the need to improve the oil recovery factor in the oil fields of the Kazakhstan sector of the Caspian Sea. The study analyzes changes in interfacial tension, rock wettability, residual oil saturation, and oil recovery factor during the application of formation water, seawater, and chemically modified seawater containing anionic surfactants. Experimental studies were carried out using a DSA100 automatic tensiometer by the pendant drop method under conditions close to the reservoir parameters of the Kashagan field. The results showed that the use of seawater leads to a reduction in interfacial tension and partial alteration of carbonate rock. The most pronounced effect was observed with the addition of surfactants, which ensured the reduction of interfacial tension to ultra-low values and promoted the transition of the reservoir surface from a hydrophobic state to a mixed-wet or predominantly hydrophilic condition.