Surfactant Adsorption Evaluation in the Presence of Crude Oil at High Reservoir Temperature Condition
Authors: Belhaj Ahmed Fatih , Elraies Khaled Abdalla , Shuhili Juhairi Aris , Mahmood Syed Mohammad , Tewari Raj Deo 
Published: November 2020

Abstract
The application of surfactants in Enhanced Oil Recovery (EOR) has over the years, revealed various challenges that impose limitations on successful implementation of surfactant flooding. Surfactant adsorption is one of the major criteria that strongly dictates the feasibility of surfactant flooding in chemical enhanced oil recovery (CEOR). This paper presents the impact of the presence of crude oil on surfactant adsorption and the influence of surfactant partitioning on the adsorption quantification. In this study, static adsorption experiments were conducted for a mixture of Alkyl Ether Carboxylate (AEC) and Alkylpolyglucoside (APG) in the absence as well as the presence of crude oil. Partitioning experiments were carried out to evaluate the surfactant partitioning between the aqueous surfactant solution and the crude oil, in order 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 32,000 ppm and temperatures of (80 °C and 106 °C). High Performance Liquid Chromatography (HPLC) was utilized in measuring the surfactant concentration throughout adsorption and partitioning tests. X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) were utilized for rock characterization prior to 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, as all having a similar increasing trend as 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 due to not considering the impact of surfactant partitioning. A significant amount of what was adsorbed belongs to AEC due to its increased chain–chain interactions with APG; hence, AEC is the greatest contributor in the overall surfactant mixture’s adsorption. Also, the AEC:APG mixture was affected by temperature increase, showing that APG has a greater sensitivity to temperature in comparison to AEC. 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 the presence and 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 explained that the change of the rock structure after adsorption in the presence of crude oil was due 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.