Polymer, SRP-2-1, was synthesized by micellar polymerization and characterized by ¹H NMR. Salt tolerance and viscoelasticity tests verified that the salt resistance of SRP-2-1 was promoted by the synergistic effects of oxyethylene groups, sulfonate, and hydrophobic chains. It is suggested that the structure of SRP-2-1 became more compact with increasing salinity. Furthermore, a mechanism is proposed as to why SRP-2-1 solution has excellent salt-resistance properties. The experimental results indicate that, because of the good shear resistance properties, the polymer SRP-2-1 could be used as an alternative in many fields, for instance in fracturing fluids, enhanced oil recovery, and sewage treatment.

Three kinds of drag reducer were synthesized by inverse emulsion polymerization and named PHWAM-1, PHWAM-2, and PHWAM-3. Drag reduction (DR) tests showed that the three drag reducers have different DR characteristics in fresh water and various saline waters because of their different types of hydrophobic monomers. PHWAM-1, without hydrophobic monomers, performs better in fresh water, while PHWAM-2 and PHWAM-3, with hydrophobic monomers, perform better in brine. In addition, PHWAM-3, which has twin-tailed hydrophobic monomers, performs best in high-concentration brine. Measurements of micro-particle size and observations of spatial structure suggest that although the stronger hydrophobic polymer has no DR advantage over a linear polymer in fresh water, the molecular chains form a mutually associative supporting structure that improves the DR performance over that of a linear polymer in high-concentration brine.

Because of their high viscoelasticity, Hydrophobic Associative Water-Soluble Polymers (HAWSPs) have been widely used in many industrial fields, especially in oilfield flooding and fracturing. However, one major problem which limits the wide applications of HAWSPs is their weak resistance to high temperatures. Once the temperature increases over 100 °C, the viscosity of the fracturing fluid decreases rapidly, because high temperatures reduce fluid viscosity by oxidizing the polyacrylamide chains and weakening the association of hydrophobic groups. To improve the high temperature resistance of one HAWSP, a triple-protection strategy was developed. First, rigid N-vinyl-2-pyrrolidone moiety was introduced into the polymer chains. Second, an environmentally-friendly deoxidizer, carbohydrazide, was selected to prevent polymer oxidization by scavenging dissolved oxygen. Results showed that both the rigid groups and the deoxidizer improved the temperature resistance of the polymer and helped it maintain high viscosity under high temperature and shear rate. Using these two protection strategies, the resistant temperature of the polymer could reach 160 °C. However, the polymer network still got severely damaged at further elevated temperatures. Therefore, as the third protection strategy, the pre-added high temperature responsive crosslinking agent was applied to form new networks at elevated temperatures. The results have shown that the optimized polymer solution as a kind of fracturing fluid showed good temperature resistance up to 200 °C.

A new terpolymer (MAS-1) was created by copolymerizing acrylamide (AM), acrylic acid (AA), and 4-isopropenylcarbamoyl-benzene sulfonic acid (AMBS). Thermogravimetric analysis (TGA) suggested that MAS-1 has better heat resistance and meets the requirements for a fracturing fluid at 200 °C. X-ray diffraction (XRD), and conductivity tests showed that MAS-1 has good water solubility. The viscosity of the fracturing fluids containing MAS-1 was found to be about 135 mPa s after 120 min at 170 s⁻¹ and 150 °C. SEM images and the determination of viscoelasticity showed that MAS-1 has a dense and robust spatial network structure in the fracturing fluid. The sedimentation velocity of the proppant was 0.0528 cm min⁻¹ at 90 °C. When enough ammonium persulfate was added to yield approximately 0.10 wt%, the viscosity of the broken fluid was 4.5 mPa s, and the gel broken fluid was transparent without visible residue. In addition, the fracturing fluid did little damage to the reservoir. The drag reduction rate of MAS-1 was always higher than KYPAM-6A and HPAM with the shear rate ranging from 1000 s⁻¹ to 7000 s⁻¹. Therefore, this fracturing fluid could be an alternative for low permeability reservoir stimulation.