(60da) Experimental and Modeling Study of the Wettability Effect on the Adsorption of an Anionic Surfactant on Sandstone Cores | AIChE

(60da) Experimental and Modeling Study of the Wettability Effect on the Adsorption of an Anionic Surfactant on Sandstone Cores

Authors 

Amirmoshiri, R. - Presenter, Rice University
Biswal, S., Rice University
Farajzadeh, R., Shell Global Solutions International
Hirasaki, G. J., Rice University
Surfactant flooding for Enhanced Oil Recovery (EOR) improves the microscopic displacement efficiency via lowering the oil/water interfacial tension (IFT) and/or wettability alteration towards more favorable conditions. However, the economic viability of any chemical EOR process that involves surfactant can be substantially limited, if the surfactant loss or retention in porous media is large. In this study, we investigate the adsorption of an anionic surfactant, AOS1416, on Berea sandstone cores under different wettability states and surface redox potentials. Typically, anionic surfactant adsorption on water-wet and oil-free sandstone is thought to be low, due to electrostatic repulsion between the surfactant and the mineral surface. However, it is found that under non-water-wet conditions and high calcium concentration, surfactant adsorption increases significantly. Adsorption levels are determined by analyzing the effluent history data with a dynamic adsorption model based on a Langmuir isotherm. As an indication of wettability alteration, the surfactant breakthrough in the neutral-wet core takes place in parallel with the extraction of the adsorbed crude oil components from the rock surface. We also show that, under water-wet conditions, changing the surface redox potential from an oxidized to a reduced state decreases the adsorption levels to some extent. This is attributed to the removal of ferric ions from the sandstone surface and calcite dissolution during the alteration of the core redox state. Findings from this study suggest that laboratory surfactant adsorption tests need to be conducted with the meticulous consideration of the surface wettability and redox state of the rock surface.