Polymer flooding is a well-established commercially available chemical technique for enhancing oil recovery. This technique is mainly used in sandstones with a limited application in carbonates due to the harsh reservoir conditions of high temperature and high salinity. This paper numerically investigates the effect of Schizophyllan biopolymer on oil recovery from carbonate cores. The effect of biopolymer on oil recovery was predicted by running several synthetic 1D simulations using measured reservoir rock and fluid data. Biopolymer flow behavior was modeled through considering adsorption, viscosity, density, salinity, non-Newtonian, inaccessible pore volume, permeability reduction, and degradation effects. The simulation runs were performed in both secondary and tertiary modes of injection. The study also includes a description of polymer screening, rheological properties measurement, and design to tailor high temperature and high salinity carbonate reservoirs.

The results show that the investigated biopolymer improves oil recovery in both secondary and tertiary modes of injection compared to conventional formation waterflooding. Moreover, the overall oil recovery of both secondary and tertiary polymer floodings are almost comparable after 6 pore volumes of injection. Nevertheless, the application of polymer flooding in the secondary mode is more preferable due to boosting the oil production rate at an earlier time. Also, an optimum polymer concentration of 800 ppm is recommended for achieving a minimum total relative mobility of oil and water phases. The findings of this work are supported by fractional flow and mobility ratio analyses to highlight the improvement in volumetric sweep efficiency as a result of using the investigated biopolymer. This study highlights the advantages of using Schizophyllan biopolymer on oil recovery from carbonate reservoirs with high temperature and high salinity conditions. The biopolymer improves mobility ratio by mainly decreasing water effective permeability and increasing water viscosity. The study at the laboratory-scale is considered as a basis for field-scale predictions.

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