Ionic surfactants applied in enhanced oil recovery: adsorption, imbibition, and zeta potential approaches

Abstract

This work examines the capacity of ionic surfactants to be adsorbed onto limestone. It also analyzes their effects on enhanced oil recovery. The finite bath method was carried out with two surfactants, an anionic saponified coconut oil (SCO) and the cationic cetyltrimethylammonium bromide (CTAB). Imbibition assays were performed in the oil recovery analysis. The effects of the surfactant solution pH on the adsorption on limestone were also assessed by means of zeta potential measurements. Results demonstrate that SCO was highly adsorbed on the rock. The adsorption of CTAB molecules was lower than that of SCO molecules, leaving free CTAB molecules in the solution. As a result, CTAB molecules acted in the reduction of interfacial tension inside the porous medium. Interestingly, zeta potential data of SCO solutions also confirmed that electrostatic interactions play an important role in the adsorption of surfactants on the rock.