Synthesis and performance evaluation of new hydrophobic associative fracturing fluid thickener HLCW

Objective Aiming at the deficiencies of the single-function fracturing fluid system in the current shale oil development, this paper develops a new multifunctional thickener.

Method A new hydrophobic associative thickener, HLCW, was prepared from acrylamide, N-benzyl-N-methacryloyloxy-N,N-dimethylammonium chloride (MTC), and poly(ethylene glycol) docosyl ether methacrylate (BEM) using 2,2-azobisisobutylamidinium dihydrochloride (V50) polymer initiator. The product was characterized by infrared spectroscopy and nuclear magnetic structure, and evaluated for apparent viscosity, temperature and shear resistance, anti-expansion, drag reduction, salt resistance, sand suspension and gel breaking properties.

Result The critical associating concentration of the thickener was 0.5 wt%, and its apparent viscosity under this condition was 181.5 mPa·s. After shearing at a fixed shear rate of 170 s⁻¹ at 120 ℃ for 1.5 h, the final apparent viscosity of the aqueous solution of 0.5 wt% thickener HLCW was 78.96 mPa·s. At room temperature, the drag reduction rate of 0.012 5 wt% thickener HLCW formulated in clear water was 73.96%. When the mass fraction exceeded 0.3%, the anti-expansion rate of the thickener aqueous solution was as high as 80%. After breaking the gel, the broken gel solution was clarified and transparent, and the residue content was much lower than the industry standard.

Conclusion The thickener HLCW has good thickening effect, high temperature resistance, shear resistance, salt resistance, and is used as a drag reducing agent in low concentration and thickener in high concentration. It has good anti-expansion effect, and compared with cationic polyacrylamide with relative molecular mass of 10 million, the thickener HLCW shows excellent sand suspension performance, and has certain prospects for oilfield industrial application.