Inverse Pickering emulsion stabilized by modified cellulose nanocrystals for drilling fluid application

With the rise in oil consumption, the production and exploration of oil have increasingly targeted unconventional reservoirs. Oil-based drilling fluids (ODFs) are well-suitable for unconventional reservoirs because of their superior wellbore stability, strong lubrication, and great resistance to contamination. Inverse (water-in-oil, W/O) emulsions have the ability to lower the oil content in conventional ODFs through the addition of water, leading to more cost-effectiveness and eco-friendliness. However, inverse emulsions require the introduction of a large amount of surfactants to stabilize the oil/water interface, which led to environmental pollution. To address these issues, surface modified cellulose nanocrystals (C14-CNCs) were prepared through acylation modification and then used as solid stabilizers to prepare a high-performance inverse Pickering emulsion-based drilling fluid (IPEDF), in which sunflower seed biodiesel was chosen as the oil phase, and organobentonite (i.e., low polarity SD-1 and high polarity SD-2) was used as a viscosifier and filtration loss reducer. The stability and structure of Pickering emulsion can be controlled by altering the hydrophilicity of C14-CNCs through adjusting the reaction time of acylation. Through optimization of the polarity of organobentonite and the hydrophilicity of C14-CNCs, the as-formulated IPEDF exhibits superior shear-thinning behavior, thixotropy, and filtration property. This work provides a promising avenue for using biomass-derived nanomaterials as stabilizers for the high-performance inverse Pickering emulsion drilling fluids.