In this study, hydrophobic quaternary ammonium intermediate was synthesized by epichlorohydrin (ECH) and oleamide propyl dimethyl tertiary amine (PKO). Sodium carboxymethylcellulose (CMC) was chemically modified by introducing a large number of hydrophobic quaternary ammonium branched chains to improve CMC’s salt resistance, thickening ability, and solubility. The quaternary ammonium salt structure can partially offset the compression double-layer effect of linear polymers in a low-price salt ion solution, which makes CMC more stretchable and helps it obtain a higher viscosity and greater drag-reduction performance. The experiment was mainly divided into three parts: Firstly, we performed an epichlorohydrin and oleic acid PKO reaction, generating an oleic acid chain quaternary ammonium chlorine atom intermediate. Secondly, the etherification reaction between intermediate –Cl and –OH groups of CMC was completed. Finally, the modified CMC was characterized by IR, SEM, and XPS, and the viscosity and the drag-reduction rate were evaluated. After CMC and the intermediate were reacted at a mass ratio of 9:1.8 at 80 °C for 5 h, the new CMC with enhanced thickening ability, salt resistance, and drag-reduction performance was obtained. We found that the apparent viscosity increased by 11%, the drag reduction rate increased by 3% on average, and the dissolution rate was also significantly accelerated, which was ascribed to the introduction of quaternary ammonium cation. Moreover, the oleic acid amide chain increased the repulsive force of the CMC chain to low-priced metal cations in solution and intermolecular repulsive force, which is beneficial to increase the viscosity, salt resistance, and drag-reduction performance.
Water‐based fracturing fluids are widely used in the development of tight, low‐permeability unconventional oil and gas fields, where the crosslinking agent component can thicken the low‐viscosity, high‐flowability base fluid to ensure sufficient proppant is transported from the wellbore to the tip of the fracture and generate the required net pressure to support the fracture. Zirconium crosslinking agents are widely used due to their good stability and high shear resistance. In the paper, glycerin, zirconium chloride, lactic acid, sodium hydroxide, and water were reacted at a molar ratio of 7:1:3:4:98 and a temperature of 80°C for 5 h; Using triethanolamine, zirconium chloride, lactic acid, and water as raw materials, the molar ratio of 4:1:3:98, reaction at 80°C for 5 h, and then zirconium lactate crosslinker and triethanolamine zirconium lactate crosslinker were synthesized respectively, which were incorporated into a newly designed self‐generating acid temperature‐controlled crosslinking system to crosslink salt‐resistant cleaning fracturing fluids mainly composed of sodium carboxymethyl cellulose, achieving delayed crosslinking of the fracturing fluid in different temperature formations. The strong crosslinking temperature range of glycerol‐lactic acid zirconium and the rheological properties of triethanolamine zirconium lactate gel and zirconium lactate gel in the system were tested. The viscosity of triethanolamine zirconium lactate gel and zirconium lactate gel were 88.86 and 94.69 mPa·s, respectively, at the shear rate of 300 s−1, and the viscosity remained above 200 mPa·s at the shear rate of 170 s−1, 60°C for 1 h. These figures far exceed the gels formed by commercially purchased zirconate. This system can make glycerol lactic achouid zirconium crosslinking agents undergo strong crosslinking at 40–65°C and triethanolamine lactic acid zirconium undergo strong crosslinking at 55–75°C. It has significant implications for the delayed crosslinking effect of massive fracturing operations.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.