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.
Highlights
Hydrophobic Associative Water-Soluble Polymers (HAWSPs) or Hydrophobically-ModifiedPolyacrylamide (HMPAM) derivatives are polymers that contain a small number of hydrophobic groups grafted onto the hydrophilic polymer backbone
A comprehensive strategy was implemented to temperature resistant HAWSP fluids which can be used as fracturing fluids for high temperature prepare high temperature resistant
HAWSP fluids which can be used as fracturing fluids for high applications, i.e., up to 200 ◦ C
Summary
Hydrophobic Associative Water-Soluble Polymers (HAWSPs) or Hydrophobically-Modified. Polyacrylamide (HMPAM) derivatives are polymers that contain a small number of hydrophobic groups grafted onto the hydrophilic polymer backbone. PEI has been employed to crosslink acrylamide-based polymer fracturing fluids in high frame still makes it difficult for low viscoelastic fluids to meet industrial requirements. An environmentally-friendly deoxidizer was added into the the amide groups in the HAWSP to increase the fluids viscosity especially at elevated temperature solution to prevent the polymer from being oxidized and degraded. HAWSPs can retain strong viscoelasticity crosslink with the amide groups in the HAWSP to increase the fluids viscosity especially at elevated only at low and medium temperature, most ofwithin the HAWSPs based fracturing temperature when the crosslinking can beso,achieved minutes. With increasing hydrophobic association viscoelasticity only atbelow low and medium temperature, so, most temperature, of the HAWSPsthe based fracturing fluids will weakened to cause viscoelasticity loss, the crosslinking of HAWSP with PEI will be canbeonly resist temperatures below 140 °C [37].
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