Potential applications of cyclodextrins in enhanced oil recovery

Abstract

• We tested the use of cyclodextrins (CD) as additives for enhanced oil recovery. • The CD decreased the oil-water contact angle for a dodecane drop immersed in brine in contact with a quartz surface. • Molecular dynamics calculations indicated that the observed effects are due to the formation of inclusion complexes at the brine/dodecane interface. In the present work, cyclodextrins (CD) were tested as potential agents for enhanced petroleum recovery. For this purpose, wettability was evaluated through a combination of experimental measurements of the contact angle of a hydrocarbon drop (dodecane) on a quartz surface and molecular dynamics (MD) simulations. The whole system was immersed in a 0.6 M NaCl aqueous solution containing the CD. Here, the dodecane, the quartz and the NaCl solution represent the oil, the rock surface and the reservoir brine, respectively, thus mimicking the situation occurring in actual oil reservoirs. It was found that the presence of the CD in the aqueous phase consistently decreased the oil–water contact angle for the dodecane drop on quartz, indicating that the CD have an effect in displacing the hydrocarbon from the rock surface. The results show that cyclodextrins are potential candidates as additives in enhanced oil recovery. Complementary, MD calculations were performed to clarify the molecular mechanisms involved in the wettability modification due to the presence of the CD. Two different strategies were employed to determine the contact angles through MD, the first of them employing the Young–Laplace equation and the second using direct geometric measurements. The calculated contact angles were in good agreement with the experimental data. The MD results suggest that the decreased contact angles are mainly due to two effects: (i) formation of inclusion complexes between the CD and dodecane at the oil:water interface; and (ii) formation of CD monolayer on the quartz surface, resulting in a decreased surface wettability for the dodecane drop.