Environmentally friendly and salt-responsive polymer brush based on lignin nanoparticle as fluid-loss additive in water-based drilling fluids

The sustainable development of global energy necessitates high-performance water-based drilling fluid (WDFs) with low toxicity and sustainability, especially in high salinity reservoir excavation. Herein, we report an environmentally friendly and salt-responsive zwitterionic polymer brush based on enzymatic lignin nanoparticles (EHL) prepared by intramolecular self-assembly as a fluid-loss additive (EHL-ASN) for WDFs by the antipolyelectrolyte effect to overcome the issues of wellbore instability and collapse caused by the deterioration of rheological and filtration properties of WDFs due to electrolyte invasion in drilling high salinity reservoirs and reveal the salt response mechanism of EHL-ASN. The ascending viscosity of EHL-ASN solution corresponded to the heightening of electrolyte salinity, which revealed that EHL-ASN solution had obvious salt response. The biological toxicity evaluation of EHL-ASN exhibited that its half maximal effective concentration (EC50) was 51,900 mg/L, which accorded with the direct emission standard. Additionally, the results for rheological and fluid-loss performance evaluation of EHL-ASN/WDFs promulgated that EHL-ASN had significant effects on heightening viscosity and debasing fluid-loss, in which, EHL-ASN could significantly debase the fluid-loss (FLAPI) of saturated salt-based mud (SSBM) from 194 mL to 4 mL, with a decline rate of 97.9%. This work not only provides a novel approach for high value utilization of lignin, but also paves the way for the development of environmentally friendly intelligent WDFs.