Improving the Thermal Stability of Hydrophobic Associative Polymer Aqueous Solution Using a “Triple-Protection” Strategy

Abstract

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.

Synthesis and rheological properties of water soluble ionic copolymers as modifier fluids at high temperature and saline media

“…Finally, the aqueous saline polymer solution of (A 35 N 35 P 30 ) exhibited a transparent aspect indicating great salt tolerance and excellent thermal stability of this copolymer under harsh conditions of 150°C and 250,000 ppm of NaCl. Recently, Zhao et al reported the thermal stability of water soluble ionic terpolymers without the presence of thermo‐responsive moieties in the resultant materials 68,69 . At the beginning (0–20 min), the viscosity of terpolymer showed a decrease with the increase of temperature from 25 to 140, 160, and 200°C, respectively.…”

Experimental Study on High-Performers Quaternary Copolymer Based on Host–Guest Effect

“…The conformation is mainly affected by the rigidity of the polymer and the forces between groups and molecular chains. Although rigidity of the polymer worsens the flexibility of the molecular chain, it can make the molecular chain more extended [ 32 ]. Therefore, increasing the rigidity of the polymer can effectively increase the temperature resistance, and the introduction of the hydrophobic group can also change the conformation of the polymer at high temperatures [ 33 ].…”

Application of Polymers for Chemical Enhanced Oil Recovery: A Review

“…Sarsenbekuly et al [ 54 ] observed that the viscosity of synthesized polymeric solution decreased with an increase in temperature for lower concentrations of HAPAM [ 54 ]. Likewise, Yang et al [ 57 ] noted that the addition of a lower concentration (10%) of N -vinyl-2-pyrrolidone hydrophobic moieties to a copolymer of acrylamide and acrylic acid yielded a lower viscosity of the polymer. On the other hand, when the polymer concentration is above the CAC, the viscosity of the polymer increases with temperature until it reaches a maximum point and thereafter decreases.…”