Summary The application of surfactants in enhanced oil recovery (EOR) has revealed over the years various challenges that impose limitations on the successful implementation of surfactant flooding. Surfactant adsorption is one of the most important aspects that strongly dictates the feasibility of surfactant-based EOR. The effect of the presence of crude oil on surfactant adsorption and the influence of surfactant partitioning on the adsorption quantification are presented in this paper. Static adsorption experiments were conducted in this study for a surfactant mixture [alkyl ether carboxylate (AEC):alkylpolyglucoside (APG)] on sandstone rock samples in the absence and presence of crude oil. Partitioning experiments were carried out to evaluate the surfactant partitioning between the aqueous surfactant solution and the crude oil to determine the partitioning influence on the adsorption results in the presence of crude oil. The mixture’s adsorption and partitioning behaviors were studied at a fixed salinity of 32 k ppm and temperatures of 80 and 106°C. High-performance liquid chromatography (HPLC) was used in measuring the surfactant concentration throughout adsorption and partitioning tests. Rock characterization was also performed in this study using X-ray diffraction (XRD) as well as X-ray photoelectron spectroscopy (XPS) before and after adsorption with and without crude oil being present. Static adsorption outcomes displayed the adsorption of APG, AEC, and the overall mixture with and without crude oil being present, because all are having a similar increasing trend when concentration increases. However, the adsorption values were much higher when crude oil was present as compared with the adsorption values when crude oil was absent; this is because of not considering the impact of surfactant partitioning. The adsorption values (i.e., at 0.2 wt%) for both temperatures were below 2.5 mg/g in the absence of crude oil and rose to around 3.5 mg/g in the presence of crude oil. A significant amount of what was adsorbed belongs to AEC because of its increased chain-chain interactions with APG, which was evidenced experimentally in our previous work; hence, AEC is the greatest contributor to the overall surfactant mixture’s adsorption. Also, temperature had an impact on the adsorption capacity of the AEC:APG mixture, showing that APG has a greater sensitivity to temperature in comparison to AEC. The adsorption behavior of APG was found to be the opposite of AEC, where the adsorption capacity at 106°C was lower for AEC than its adsorption capacity at 80°C and vice versa for APG. The surfactant partitioning results were used to validate the surfactant adsorption outcomes in the presence of crude oil. After eliminating the partitioning effect, the surfactant adsorption isotherms in both cases of the presence and the absence of crude oil were almost identical. The results highlighted the importance of measuring surfactant partitioning, and the impact that partitioning has on the total surfactant losses during the surfactant flooding process. XRD and XPS results indicated that the change of the rock structure after adsorption when crude oil was present was attributed to the rock dissolution phenomena. It was concluded that adsorption and partitioning take place in the water/oil/rock system simultaneously and taking that into account allows for the improved and proper designing of the surfactant flooding.

中文翻译：

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高油藏条件下原油存在下砂岩上阴离子-非离子表面活性剂混合物的静态吸附评价

总结 多年来，表面活性剂在提高采收率 (EOR) 中的应用揭示了各种挑战，这些挑战限制了表面活性剂驱油的成功实施。表面活性剂吸附是强烈决定基于表面活性剂的 EOR 可行性的最重要方面之一。本文介绍了原油的存在对表面活性剂吸附的影响以及表面活性剂分配对吸附定量的影响。在这项研究中，在不存在和存在原油的情况下，对砂岩岩石样品上的表面活性剂混合物 [烷基醚羧酸盐 (AEC): 烷基聚葡糖苷 (APG)] 进行了静态吸附实验。进行分配实验以评估表面活性剂水溶液和原油之间的表面活性剂分配，以确定在原油存在下分配对吸附结果的影响。在 32 k ppm 的固定盐度和 80 和 106°C 的温度下研究了混合物的吸附和分配行为。高效液相色谱 (HPLC) 用于测量整个吸附和分配测试中的表面活性剂浓度。本研究还使用 X 射线衍射 (XRD) 以及 X 射线光电子能谱 (XPS) 在存在和不存在原油的情况下吸附前后进行岩石表征。静态吸附结果显示了 APG、AEC 以及存在和不存在原油的整体混合物的吸附，因为当浓度增加时，所有这些都具有相似的增加趋势。然而，与没有原油时的吸附值相比，存在原油时的吸附值要高得多；这是因为没有考虑表面活性剂分配的影响。在没有原油的情况下，两种温度下的吸附值（即在 0.2 wt%）均低于 2.5 mg/g，而在有原油的情况下，吸附值上升至约 3.5 mg/g。大量被吸附的物质属于 AEC，因为它与 APG 的链-链相互作用增加，这在我们之前的工作中得到了实验证明；因此，AEC 是整个表面活性剂混合物吸附的最大贡献者。此外，温度对 AEC:APG 混合物的吸附能力有影响，表明与 AEC 相比，APG 对温度的敏感性更高。发现 APG 的吸附行为与 AEC 相反，其中 AEC 在 106°C 的吸附容量低于其在 80°C 的吸附容量，反之亦然。表面活性剂分配结果用于验证原油存在下的表面活性剂吸附结果。消除分配效应后，有原油和无原油两种情况下的表面活性剂吸附等温线几乎相同。结果强调了测量表面活性剂分配的重要性，以及分配对表面活性剂驱过程中表面活性剂总损失的影响。XRD和XPS结果表明，当有原油存在时，吸附后岩石结构的变化归因于岩石溶蚀现象。得出的结论是吸附和分配同时发生在水/油/岩石系统中，考虑到这一点，可以改进和正确设计表面活性剂驱油。