Viscoelastic Rheological Property of Different Types of Polymer Solutions for Enhanced Oil Recovery

The capability of hydrophobic association polymer (HAPAM) to displace oil is different from that of hydrolyzed polyacrylamide (HPAM) because they have different rheological properties. The viscoelasticity of five polymers was measured using Physica MCR301 rheometer and was compared. The five polymers include three HAPAMs with relative molecular mass of 1 248x10 ⁴ (Type I), 750x10 ⁴ (Type II), and 571x10 ⁴ (Type III) separately and two HPAMs with relative molecular mass of 1 200x10 ⁴ and 3 800x10 ⁴ respectively. The experiment results indicate that the viscoelasticity of HAPAM is better than that of HPAM. The storage modulus G' and the loss modulus G" for HAPAM solutions are also larger than those for HPAM. Comparing the rheological curves of different HAPAM types, it is found that the viscosity of type II and type III is almost same at different shear rates while the viscosity of type I is the lower than that of Types II and III. The storage modulus G' and the loss modulus G" for three types of HAPAM were measured in low oscillation frequency range, and the results show that G' is greater than G" for all three different types of HAPAM, but their loss modulus is almost same, and the G' is in the order of type II>type III>type I. In addition, the G' and G" increase with aging time for all three HAPAM solutions were stayed at different days. The viscoelasticity of type I reaches the highest value when aging time is 9 d at 45 °C, but it is 7 d for type II and type III. The different viscoelasticity properties can be attributed to self-organization supermolecule networks which is formed by hydrophobic association of HAPAM molecular and molecular chain entanglement.