Experimental and Modelling Studies on Adsorption of Anionic Surfactant in Alkaline-surfactant-polymer (ASP) Flooding

Alkaline-surfactant-polymer (ASP) has recently gained interest in the petroleum industry due to its synergy. However, studies on surfactant adsorption in ASP formulation modelling are still limited and unclear, making it challenging to obtain the ideal ASP formulation. Therefore, this research focuses on adsorption of anionic sodium dodecyl sulfate (SDS) and cationic cetyltrimethylammonium bromide (CTAB) surfactants on quartz sand surface, in the presence of sodium carbonate (Na2CO3) alkali and partially hydrolyzed polyarylamide (HPAM) polymer and modelling of adsorption isotherms. Critical micelle concentrations (CMCs) of both surfactants were determined from surface tension method. Static adsorption tests were conducted by shaking of the mixture samples (mass-to volume ratio of 1:5), centrifuging it, and then collecting the supernatant liquid for UV-Vis analysis. Surfactant concentrations ranged from 100-2000 ppm (SDS) and 100-500 ppm (CTAB). The Na2CO3 and HPAM concentrations for ASP solution were fixed at 5000 and 500 ppm, respectively, while the salinity varied from 10000 to 30000 ppm. The CMC of SDS was found at 2200 ppm, higher than CTAB (370 ppm). From adsorption tests, overall, the CTAB adsorption was greater than SDS on quartz-sand with doubled the value at 10000 ppm salinity at 500 ppm concentration. The adsorption of surfactants also increased with increasing salinity. From Langmuir and Freundlich adsorption isotherms developed, the Langmuir isotherm model proved to be the best fit for the experimental data of surfactant adsorption phenomena in ASP flooding.