Synthesis and performance evaluation of a new drag reducer–cationic hybrid polymeric based on polyacrylamide

The aim of the present work is to prepare polymeric materials and to be used as drag reducer. In this paper, a new type of drag reducer was synthesized with polymeric materials. Technically, N, N-dimethyl-N-hexadecyl allylammonium bromide (DHAB) was synthesized with 3-bromopropene and N, N-dimethylcetyl tertiary amine, and then cationic hydrophobically associating polyacrylamide P(AM-DHAB), the desired drag reducer, was synthesized. The chemical structures of the products were confirmed by IR and NMR. The molecular weight of the drag reducer was found to be 2.66 × 10 6 g/mol as measured by laser light scattering method. In fresh water, when the concentration of drag reducer is 0.03%, the highest drag reduction rate is reached up to 73.05%. However, when the concentration of drag reducer is further increased, the viscosity is increased and drag reduction rate is decreased; indicating high viscosity has a significant negative effect on drag reduction rate. While in brine, with a viscosity obviously lower than that in fresh water, the drag reduction rate was slightly lower than 70% when the concentration of drag reducer was 0.03%; increasing the concentration of P(AM-DHAB) did not lead to a significant increase in viscosity, instead, it caused the drag reduction rate to be higher than 70%. Therefore, low viscosity facilitates drag reduction performance. Potassium persulfate makes the viscosity of slick water decrease sharply, which helps promote the polymer degradation and thus prevent polymer damage to the reservoir. Scanning electron microscope (SEM) showed that the drag reducer featured an obvious network structure in fresh water before gel breaking, and that there was almost no network structure but a small number of crystallites after gel breaks. In contrast, in brine, no matter before and after gel breaking, only salt crystals were cleanly seen under electron microscope due to high concentration of salt.