A Microbial Exopolysaccharide Produced by Sphingomonas Species for Enhanced Heavy Oil Recovery at High Temperature and High Salinity

Abstract

Microbial exopolysaccharides secreted by microorganisms during metabolic processes have been widely used in biotechnology because of their environmentally friendly and renewable nature. This study evaluates the potential of a novel microbial exopolysaccharide, diutan gum, which is produced by Sphingomonas species, for enhanced heavy oil recovery at high temperature and high salinity. In addition, two conventional polymers [xanthan gum and partially hydrolyzed polyacrylamide (HPAM)] used in oil exploitation are compared under the same conditions. It is found that the steady apparent viscosity and dynamic modulus of aqueous diutan gum solutions are not sensitive to the temperature and virtually independent of the salinity, while those of xanthan gum and HPAM significantly decrease at high temperature and high salinity. The retention values of the apparent viscosity and the dynamic modulus of diutan gum at 90 °C and 244 121 mg·L–1 salinity are greater than 90%. The gel-like structure of diutan gum is depende...