Journal of Chemical Engineering of Japan, Vol.43, No.2, 115-125, 2010
Storage and Loss Moduli of Alcoflood Polymers Used in Enhanced Oil Recovery Processes
The viscoelastic behavior of aqueous solutions of Alcoflood polymers (AFPs) was investigated in terms of the complex modulus, storage modulus, and loss modulus using a RheoStress RS100 rheometer. AFP solutions with a wide range of concentrations were examined (100-10,000 ppm). Three different AFPs AF1235, AF1275, and AF1285 were tested. The linear viscoelastic range for these three AFPs over the concentration range of 100-10,000 ppm was around 2 Pa. The polymer concentration controlled the behavior of complex modulus versus frequency. The critical polymer concentration was found 1000 ppm. The apparent complex modulus, for polymer concentrations less than 1000 ppm, changed slightly with the power index around 2. For concentrations higher than 1000 ppm, the apparent complex modulus and power index significantly increased with the polymer concentration up to 10,000 ppm. The behavior of storage modulus of the AFPs was similar to that of complex modulus, whereas the loss modulus was different. At 1000 ppm, the AFPs showed a viscous behavior for frequencies less than 0.15 s(-1), and a predominantly elastic behavior for frequency greater than 0.15 s(-1). At high concentrations, AF1275 and AF1285 always showed an elastic response, whereas AF1235 showed an elastic response only if the frequency exceeded 0.3 s(-1).