A zwitterionic polymer containing a hydrophobic group: enhanced rheological properties

A zwitterionic polymer containing a hydrophobic long chain, named MANPS, was independently developed by free radical solution polymerization. The introduction of an hydrophobic long-chain monomer, namely, octadec-9-enioc acid allylamide (NAE) and an amphoteric ionic monomer, i.e., 3-(3-methylacrylamide propyl dimethylamino)-propyl-1-sulfonate (MEPS) in conventional acrylamide (AM) and acrylic acid (AA) enhanced the rheological properties of polymer flooding agents, thereby improving their temperature resistance and salt tolerance. A series of experiments were performed to determine the optimal reaction conditions for the polymer; the structure and molecular weight characteristics of MANPS were confirmed by FT-IR spectroscopy, 1H NMR spectroscopy, intrinsic viscosity, high-performance liquid chromatography (HPLC) and SEM. The rheological test results showed that MANPS had higher apparent viscosity than the partially hydrolyzed polyacrylamide (HPAM). It exhibited good shear recovery at a certain shear rate. The reason was considered to be the long-chain entanglement of molecules and the “anti-polyelectrolyte action” of zwitterions. Thermogravimetric analysis provided good evidence of the thermal properties of the copolymer MANPS. Evaluating the oil displacement performance of the oil-displacing agent was an essential part. The results showed that the copolymer MANPS was comparable to HPAM having a 10.4% higher oil displacement rate under the same concentration and test conditions.