Enhanced Oil Recovery by COMB-Flow: Polymer Floods Revitalized

Abstract When a typical oil reservoir reaches its economic limit after primary and secondary recovery (water flooding), the world average says that more than two thirds of the original oil is left in place1. The challenge is to develop Enhanced Oil Recovery (EOR) methods that ensure an economical tail end production from these fields. Today’s oil price is very high resulting in better economics for EOR-concepts. There is now a trend in the business that companies again are doing research and development in this area. Secondary water flooding leaves the residual oil capillary trapped. Surfactant injection can mobilize this residual oil by a strong reduction in the interfacial tension (IFT) between oil and water. However, a combination of polymer for mobility control, a small bi-functional molecule for enhanced solubility and reduced effect of salinity, and surfactant to lower the IFT will according to the theory have a much better effect as a tertiary oil recovery method. The concept is to search for a robust type III phase system. A polymer, a surfactant and a small bi-functional molecule in combination has been given the tentative name of "COMB-flow". Laboratory experiments with this COMB-flow system indicate an increased recovery of OOIP by 20%. The residual oil saturation was lowered by 12% and the residual oil recoveries ranged between 30.5% and 37.3%. Relative to the recovery obtained after traditional water flooding the recovery is enhanced almost 50%. These results were obtained on a crude oil having the in situ viscosity of 3.5 mPas at reservoir temperature. The experiments were performed at reservoir conditions. This system will be tested further on effects on different crude oils. Furthermore, different flow regimes will be tested.