Synergistic effects of microbial polysaccharide mixing with polymer and nonionic surfactant on rheological behavior and enhanced oil recovery

A novel sphingan WL was mixed with an anionic polyacrylamide (APAM) and a nonionic surfactant (Brij 35). The viscosity and rheological properties of the two mixtures were systematically investigated. An obvious increase in viscosity was observed for the mixed solution containing WL and APAM in a ratio of 9:1. The two inflection points on the surface tension curve indicated intermolecular interactions between WL and Brij 35. The combination of WL and the APAM or WL and Brij 35 resulted in the formation of networks in the solution through electrostatic interactions and hydrogen bonding interactions. Moreover, the rheological properties of WL-APAM were observed to be maintained under high temperature and high salinity conditions, and the WL-Brij 35 could tolerate high temperature, too. The mixtures of WL–APAM and WL–Brij 35 with only 0.035 wt% WL could enhance the oil displacement efficiencies by 21.31% and 22.17%, respectively. Therefore, the synergistic effects between exopolysaccharides and polymers/surfactants were demonstrated to improve oil recovery.