Polymer flooding is the most successful chemical enhanced oil recovery (EOR) method. This technique has achieved large-scale field applications at Daqing and Shengli oilfields in China. At Daqing oilfield, polymer flooding has improved oil recovery by 10%. At Shengli field, polymer flood has contributed to more than 22 million tons of oil since 1992.

The most common polymer for EOR projects is partially hydrolyzed polyacrylamide (HPAM). Since 1970s, continuous efforts have been spent on understanding the factors that influence the viscosity behavior of HPAM. It was discovered that shearing, heat, divalent ions and monovalent ions all have negative impacts on polymer viscosity. However it is still a challenge to predict the viscosity of HPAM under given reservoir conditions. The commonly used Carreau equation and Meter equation fail to consider the various factors that lead to loss of polymer viscosity.

In this paper, extensive laboratory tests were conducted to measure the viscosity of HPAM solution under the influences of shearing, high temperature, Calcium concentration and sodium concentration. Based on the test data, numerical correlations are proposed to predict the power law parameters. These formulas take into consideration the various factors that affect polymer viscosity. These correlations will help to improve the prediction of polymer viscosity under reservoir conditions, and will lead to more reliable design for polymer flooding projects.

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