Mobility Control and Adsorption-Retention Behavior of an Engineered-Strain-Derived Microbial Polysaccharide in High-Temperature and High-Salinity Porous Media

Conventional polymers often undergo viscosity loss and performance deterioration in high-temperature and high-salinity reservoirs. A novel microbial polysaccharide system developed from an engineered oil-recovery strain exhibits good temperature and salt tolerance as well as strong mobility-control capacity, indicating its potential as an oil-displacement agent. Here, we examine how adsorption and retention in porous media contribute to its mobility-control behavior under high-temperature and high-salinity conditions. The polysaccharide showed concentration-dependent shear-thinning behavior at 85 °C in formation water and significantly enhanced flow resistance during core flooding, with a maximum resistance factor of 13.05 while maintaining a moderate residual resistance factor of 1.93–2.4. Dynamic retention increased with polysaccharide concentration and decreased with injection rate, reaching a maximum of 0.43 mg/g. Static adsorption followed Langmuir-type behavior (R2 > 0.98, Langmuir affinity constant KL = 9.6 L/mg), suggesting strong polymer-mineral affinity, and single-mineral adsorption further showed preferential adsorption on clay minerals. These results indicate that adsorption and retention contribute to the flow-resistance behavior of this polysaccharide in high-temperature and high-salinity porous media, providing a basis for its application in polymer flooding under harsh reservoir conditions.