Enhanced Oil Recovery (EOR) is a technique for increasing the amount of crude oil that can be extracted from an oil field. Following natural oil production and water injection, respectively primary and secondary oil recovery, the recovery of oil is enhanced with tertiary techniques like injection of CO2, surfactants, polymer injection, etc. or a combination. With polymer injection water soluble polymer is injected into the oil-bearing formation to improve the displacement of the oil and thereby increase the oil recovery. Typically, the polymer is injected in one or more injection wells, displacing the oil to the producing wells. Application of the method, however, is limited to oil reservoirs with relative low temperature and salinity.