Advantageous supramolecular system through self-association of xanthan gum/cationic surfactant via β-cyclodextrin host-guest complexations for Enhanced Oil Recovery Applications

Abstract

The self-assembly of xanthan gum/surfactant/β-cyclodextrin to further improve its functionality at elevated temperatures and in brines with high salinity and hardness concentration was evaluated. The effect of surfactant type (i.e. anionic and/or cationic) and brine concentration (2.10 and 8.41 wt%) on self-association was established and compared to the behavior of a self-assembled system of a partly hydrolyzed polyacrylamide (HPAM)/surfactant/β-CD. Results demonstrate that self-assembly is surfactant dependent. Self-assembled polymeric (SAP) systems with superior viscoelasticity, tolerance to brine concentration, and improved thermal stability relative to their corresponding baseline polymers were obtained for the xanthan-gum/cationic surfactant/β-CD (XG-SAP) blend and the HPAM/anionic surfactant/β-CD (HPAM-SAP) mixture. Only the XG-SAP system shows thixotropy. Encapsulation of the cationic surfactant decreases its adsorption onto sand and kaolin by 27% relative to the adsorption of the surfactant in free state. The long-term bio-stability tests indicate that high brine concentration offers the antimicrobial action to the SAP and polymer systems. The XG-SAP system has inherent advantages for Enhanced Oil Recovery Applications.