Performance of Oil-Based Drilling Mud Modified by Lignocellulose Nanofiber-Cottonseed Oil-Sucrose Ester Compounds at Elevated Temperatures

Inverted-emulsion oil-based muds (OBMs) are widely used in high-temperature drilling due to their thermal stability and lubricity. However, high loadings of synthetic emulsifiers and fluid loss agents are often needed for fluid loss control, leading to environmental concerns and high costs. This study aims to develop a bioderived emulsion additive comprising lignocellulosic nanofibers (LCNFs), sucrose ester (SE), and cottonseed oil (CSO) to enhance the performance and sustainability of commercial OBM formulations. The LCNF-oil mixture (LOM) system was prepared by dispersing LCNFs (2.8 wt %) and SE (0.25–0.75 wt %) into CSO. The use of SE in the LCNF/SE system significantly improved the dispersion of LCNFs, increasing the zeta potential from −32.9 to −52.8 mV and reducing the particle size from 108 to 30 nm. In the LOM-applied OBM, yield stresses increased from 3.84 to 5.76 Pa and gel strength increased from 6.24 to 8.16 Pa, with minimal impact on plastic viscosity. With the use of LOM in the OBM, filtration performance was substantially improved, with fluid loss reduced from 12.2 to 6.0 g and filter cake thickness from 3.5 to 2.5 mm from HT/HP filtration tests. The water-wettability of the filter cake improved as shown by the decreased water contact angle from 74.1° to 43.5°. Thus, LOM functions as a multifunctional and biodegradable additive that enhances OBM rheology, filtration loss control, and wettability of the OBM, offering a promising strategy for more sustainable high-temperature drilling applications.