Preparation Of Acrylamide Polymers And The Study On The Molecular Weight And Solution Behavior

Conventionally partially hydrolyzed polyacrylamide (HPAM) is used in enhanced oil recovery (EOR) as thickening agents. However, HPAM has some disadvantages. For instance, high temperature leads to the breakage of polymer chain, and the viscosity of HPAM quickly decreases with increased salinity of water. Therefore the study on modified polyacrylamide more suitable for EOR has attracted extensive attention. In this paper, on the basis of copolymerization of acrylamide (AM) and acrylic (AA), poly (ethylene glycol) methyl ether methacrylate (PEGMA) was added to prepare ternary polymers AM/AA/PEGMA (PAAP). The structure and solution properties of the polymers were studied, providing the theoretical and experimental evidences for its use in EOR.Firstly the application of polyacrylamide (PAM) in EOR was introduced and the polymerization technics, effect factors and application of HPAM and amphiphilic polyacrylamide (APAM) were reviewed.Then the polymerization composition was studied. The best composition was obtained where the reaction temperature was 30°C, kerosene was used as oil phrase; the oil soluble ABVN was used as initiator; the concentration of AM and AA monomer solution was 60% in which the mole proportion of AM to AA was 3/1; MOA-3/OP-10 was used as composite emulsifer in which the weight proportion of MOA-3 to OP-10 was 90/10, and the volume ratio of emulsifer to oil phase was 25%; and the volume ratio of water to oil was 1/3.In accordance with the composition above, HPAM was prepared by inverse microemulsion polymerization. The structure of HPAM was characterized by IR, ¹H NMR. Moreover, the effects of the reaction temperature, and the concentration of monomer ([M]), initiator ([I]), emulsifier ([E]) on molecular weight (M) of HPAM were studied. It was found that the decrease of temperature leaded to the increase of M of HPAM. Furthermore, the approximate expression that M∝[M]^1.85[I]^-0.45[E]^-0.59 was obtained.On the basis of copolymerization of AM and AA, PEGMA was added to prepare ternary polymers AM/AA/PEGMA (PAAP) by inverse microemulsion polymerization. The structures of the ternary polymers were characterized by IR, ¹H NMR and intrinsic viscosity ([η]). The aggregation morphology of polymer solutions was studied by Atomic force microscope (AFM) and dynamic light scattering (DLS). Moreover, the effects of PEGMA content, polymer concentration, shear rate and temperature on the rheological behavior of polymer solutions were studied.The results indicated that the aggregates in dilute solution was spherical like and the average diameter was under 100 nm, which was not sensitive to NaCl presence and temperature rise compared to HPAM. When PEGMA increased, the intrinsic viscosity of PAAP increased, Huggins constant (K_H) first increased then deceased. Moreover, the apparent viscosity of PAAP solution increased with obvious shear thinning behavior and was sensitive to the polymer concentration and can be maintained when the temperature increases. The presence of NaCl made the polyelectrolyte chain of PAAP shrinking, leading to the declining of apparent viscosity. When PEGMA increased, the storage moduli (G′), loss moduli (G″) and the complex viscosityη* increased. G' became larger than G″at a certain frequency illustrating the importance of the elastic part of PAAP, while the characteristic relaxation time (Ï„) first increased then deceased with the increase of PEGMA.