Abstract
Polymer solutions reduce the water-oil mobility ratio and improve sweep efficiency and are used for enhanced oil recovery (EOR) in petroleum reservoirs. However, they have some limitations, especially in harsh reservoir conditions. At high temperatures and high salinities (HTHS), the polymers' efficiency decreases because of their viscosity reduction. Using a mixture of polymers that are stable in harsh conditions could solve this challenge. In this study, the synergetic effect of hydroxyethyl celluloses' (HECs) resistance to salinity, and the polyvinyl pyrrolidones' (PVP) resistance to elevated temperatures are studied for their mixtures in different situations. The effects of temperature, salinity, and shear rate on the viscosity of PVP and HEC mixtures were investigated. Measuring the viscosity of PVP and HEC at various concentrations showed that a maximum viscosity could be achieved at a composition ratio of 40:60 for HEC/PVP which is considered an optimum composition. While results indicated that increasing shear rate reduces viscosity, the optimum concentration has the greatest reduction that could make the flooding operation more efficient. Studies on temperature and salinities showed that mixtures of PVP and HEC have good stability in the HTHS conditions. The optimum solution had the lowest independence to temperature compared to other concentrations of HEC and PVP. As lower interfacial tension (IFT) assists in more efficient flooding, the interfacial tension between oil and polymer solutions was measured. It was observed that the suggested polymeric solution has desirable IFT (less than 8 mN/m) with oil in the presence of different salts.
NSTL