The rheological characteristics of Kuwait crude oil samples were studied as a function of the American Petroleum Institute gravity(API),drag reduction material and concentration,isothermal and nonisothermal conditions,and mixer speed and frequency.Accurate measurements and analyses of rheological characteristics are important to determine the effect of a drag reduction agent and ambient conditions on the crude oil flow characteristics and required pumping power.Three crude oil samples obtained from different wells with API values of 14.81(crude A),16.33(crude B)and 14.09(crude C)were used in the experiments.Various polyacrylamide(PAM)concentrations were used to assess the effect on the rheological properties of the three crude oil samples.The disruption of wax crystal formation and the changes in loss modulus(G"),viscosity and strain were measured under isothermal and nonisothermal conditions.The PAM performance was compared with that of five surfactants,namely poly(sodium 4-styrenesulfonate)(PSSS),sodium dodecyl sulfate(SDS),cetyltrimethylammonium bromide(CTAB),hexadecylphosphocholine(HTPC),and CHP,which is an equal molar ratio mixture of PSSS,CTAB and HTPC.For a surfactant concentration of 70 ppm,PSSS results in the lowest viscosity value for crude A,while CHP results in the lowest viscosity value for crude B.An increase in the loss modulus(G")values was obtained with the addition of PSSS or CHP.
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