Preparation and characterization of the octenyl succinic anhydride (OSA) modified sphingan WL gum as novel biopolymeric surfactants

Combining polymer and surfactant in one agent namely polymeric surfactants with both high viscosity and surface activity has become a viable alternative for the traditional enhanced oil recovery (EOR) processes. With the purpose of developing new polymeric surfactants, the biopolymer flooding agent sphingan WL gum was modified by octenyl succinic anhydride (OSA) through the esterification reaction. The effects of molecular weight (MW) of WL and the OSA: WL ratio on the properties of the products were investigated. As the OSA concentration increased, the degree of substitution was increased. WL2 with the medium MW was the best substrate and the optimal OSA:WL was 1:1; the obtained sample OSA-WL2-2 exhibited good viscosity and surface activity. Compared with WL2, its viscosity (23 mPa·s) was increased by 75.98 %; the surface tension decreased from 59.30 mN/m to 48.13 mN/m, and the critical micelle concentration was 2.29 mg/mL; the emulsifying activity index was increased by 57.18 %. OSA-WL2-2 also had higher elastic modulus G' and salt tolerance due to its increased MW and intermolecular association among the hydrophilic and hydrophobic groups. OSA-WL2-2 showed higher oil washing efficiency (79.6 %) than the commonly-used polyacrylamide, SDS and modified cellulose samples and made it a potential flooding agent in EOR.