Improving polymer flood performance in high salinity reservoirs

•We conducted experiments to investigate the effect of preflush slug injection prior to polymer in high salinity reservoirs.•The investigated parameters are polymer concentration and polymer slug size, preflush salinity, and preflush slug size.•We compared the results with waterflooding and polymer flooding.•The difference of salinities between preflush slug and in situ water should be maintained at a minimum to ensure high oil recovery.•Preflush-polymer-water flood process outperformed water flood performance by as much as 18%.

The application of Enhanced Oil Recovery (EOR) techniques is encouraged by the current oil price and the growing global demand for oil. Optimizing oil production from current resources becomes a main strategy target for many oil producing companies around the world. Among EOR processes, polymer flooding is an attractive option in many reservoirs. The objective of polymer flooding is to control water mobility inside oil reservoirs to ensure high oil recovery factors. Several design parameters are critical for the success of polymer flooding applications. In many reservoirs, high salinity of formation׳s water imposes a challenge on polymer flood applicability. Therefore, improving polymer flood performance in high salinity conditions may unlock these resources which in turn will have enormous positive impact on oil reserves. Injection of a water slug (preflush) ahead of polymer, to condition the high salinity reservoir, is a promising technique to minimize the effect of salinity on polymer slug. In this work, a series of lab experiments were conducted to explore the performance of sequential injection of preflush-polymer-water on oil recovery factor. The effects of several design parameters are investigated including polymer concentration and polymer slug size, preflush salinity, and preflush slug size. The results indicate that preflush and polymer characteristics have various degrees of influence on oil recovery factor.