Preparation and Performance of Salt Tolerance and Thermal Stability Cellulose Nanofibril Hydrogels and Their Application in Drilling Engineering

Abstract

The poor salt tolerance, thermal stability, and environmental performance of petrochemicals can severely limit their applications in drilling engineering. In this study, cellulose nanofibril (CNF) hydrogels with improved salt tolerance and thermal stability were prepared, and their filtration performance was evaluated. The hydrogels were prepared through the simultaneous grafting of 2-acrylamido-2-methylpropane sulfonic acid (AMPS) and butyl acrylate (BA) onto the CNF surface through ceric ammoniumnitrate-induced radical polymerization. The modified and original CNF samples were characterized using Fourier Transform infrared spectroscopy (FT-IR) and rheological measurements. The FT-IR analysis results showed that both AMPS and BA were grafted onto the CNF backbone, affirming the successful preparation of the grafted CNFs. The rheological analysis results showed that the modified CNF hydrogels exhibited significantly improved salt tolerance, thermal stability, and “salt-thickening” effect. Moreover, the results of the fluid loss test showed that the modified CNF hydrogels exhibited a much better fluid loss control than the original CNF hydrogels. In addition, after adding 2% modified CNF hydrogels as a filtrate reducer in the drilling fluids prepared with a 6% combined salt solution, the filtrate loss was significantly reduced even after aging for 72 h at 160°C.