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Over 40% of the current world conventional oil production comes from carbonate reservoirs, dominantly mature and declining giant oilfields. After primary and secondary oil production stages using tertiary oil production methods as part of an enhanced oil recovery (EOR) scheme is inevitable. Surfactant flooding aims at reducing the mobility ratio through lowering the interfacial tension between oil and water and mobilizing the residual oil. This article highlights the adsorption equilibrium of the combination of different types of nanosilica and Zyziphus Spina Christi, a novel surfactant, in aqueous solutions for EOR and reservoir stimulation purposes. A conductivity technique was used to assess the adsorption of the surfactant and nanosilica in the aqueous phase. Batch experiments were used to understand the effect of adsorbent dose on sorption efficiency as well. The adsorption data were examined using four different adsorption isotherm models (Langmuir, Freundlich, Temkin, and Linear), and the adsorption parameters were determined for each model. This study suggests that a Freundlich isotherm model can satisfactorily estimate the adsorption behavior of combination nanosilica and surfactant adsorption on carbonates. Results from this study can help in appropriate selection of surfactants in the design of EOR schemes and reservoir stimulation plans in carbonate reservoirs.

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One of the robust and high-performance EOR methods which use chemical agents is chemical flooding. Environmental impacts, surfactant cost, and oil price are the three main parameters that affect on the robustness of the surfactant flooding in oil reservoirs. Interfacial tension reduction and wettability alteration of the reservoir rocks are the two main mechanisms of the oil recovery via employing surfactant flooding. The preliminary study about adsorption and environmental impacts of the new natural-based surfactant which derived from roots of Glycyrrhiza Glabra was investigated systematically by the authors and proved the ability of the aforementioned surfactant for EOR goals. Thanks to this point that throughout the current study, core displacement tests and qualitative and quantitative wettability experiments were carried out to specify performance of the above-mentioned natural surfactant in oil recovery. For wettability alteration measurements, contact angle measurement as a quantitative method, and floatation and two-phase separation experiments as qualitative methods were utilized. In addition, three commonly industrial surfactants were implemented throughout the wettability alteration experiments to contrast performance of the used surfactants. Thanks to the outcomes obtained from qualitative and quantitative wettability alteration experiments, and the surfactant suggested in this study could change wettability of carbonate rock from strongly oil-wet toward water-wet state. In addition, based on the core displacement experiments, it is robust, cheap, and high performance in comparison with other conventional industrial surfactants for surfactant flooding purposes. There is a hypothesis that the addressed raw surfactant can be utilized in chemical flooding of oil reservoirs owing to very low cost and availability around the world compared to other currently implemented surfactants.