A Salt-Resistant Sodium Carboxymethyl Cellulose Modified by the Heterogeneous Process of Oleate Amide Quaternary Ammonium Salt

Abstract

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.

Preparation and laboratory study of a sodium carboxymethyl cellulose smart temperature‐controlled crosslinked gel fracturing fluid system

“…The mass ratio of 7:3 is mixed to prepare fracturing fluid, which can greatly increase the degradation performance, salt resistance, temperature resistance, and shear resistance of fracturing fluid. 22,23 Before crosslinking, the drag reduction rate is more than 70%, after breaking the gel, the residue amount is very low. Compared with a single PAM fracturing fluid, it can effectively reduce the water sensitivity and water locking effect in the reservoir, which is very suitable for large-scale fracturing operations in the middle and high depth of tight oil and gas reservoirs.…”

“…In addition, rigid sodium carboxymethyl cellulose (CMC) is used as the main thickening agent, while polyacrylamide (PAM) is only used as the drag reducing agent. The mass ratio of 7:3 is mixed to prepare fracturing fluid, which can greatly increase the degradation performance, salt resistance, temperature resistance, and shear resistance of fracturing fluid 22,23 . Before crosslinking, the drag reduction rate is more than 70%, after breaking the gel, the residue amount is very low.…”