Adsorption of surfactants on clay minerals

Abstract

Adsorption of surfactants from aqueous solutions in porous media is very important in enhanced oil recovery (EOR) of oil reservoirs. The loss of surfactants due to adsorption on the reservoir rocks weakens the effectiveness of the surfactant solution injected to decrease the oil–water interfacial tension (IFT). This project investigated the effect of mineralogical composition of adsorbents on adsorption. Experimental results from this study will provide additional insight into the feasibility of surfactant-enhanced flushing. The experiments were divided into two parts. In the first part, the experiments were carried out in a surfactant flooding apparatus and for the second part the experiments were conducted in batches. In dynamic condition, nonionic surfactants were injected into the sand packs in which different amounts of clay minerals (kaolinite and illite) were added. In static condition, adsorbents were mix composition of quartz sand and clay minerals at different percentages exposed to nonionic and anionic surfactants. In both static and dynamic conditions, the amount of surfactant adsorbed was quantified by subtracting the concentration of surfactants after adsorption from the initial one. It was concluded that there is a relationship between adsorption of nonionic surfactants and the amount of clay mineral in the adsorbents since the quantity of surfactant adsorbed by adsorbents raised when the percentage of clay mineral in the adsorbents increased (from 2% to 8% in sand packs and from 5% to 20% in the mixtures). Adsorption power of clay minerals for nonionic surfactants follows the order of montmorillonite >> illite > kaolinite in batch experiments. In sand pack flooding, adsorption power of adsorbents go along the order of illite > kaolinite. Adsorption of the anionic surfactant on all adsorbents was negligible.