Nanocellulose and Its Derivatives for High-Performance Water-Based Fluids
Authors: Hall Lee J. , Deville Jay P. , Araujo Carlos Salas , Li Shuai , Rojas Orlando J. 
Published: March 2017

Abstract
Water-based drilling fluids provide an economical and environmentally attractive option for wellbore construction. Despite the development of high performance water-based fluids, consistent demonstration of drilling performance comparable to oil-based fluids has proven to be elusive. Both traditional and high-performance water-based systems typically use biopolymers to provide filtration control, viscosity, and suspension properties. These biopolymers include naturally occurring materials, such as celluloses, starches, hydrocolloids, and bacterially engineered polymers, such as xanthan gum. Although several options exist, new materials are always desired to improve efficiency or enhance high pressure, high temperature (HPHT) performance. Recently identified nano-structured biomaterials, such as nanocelluloses, have been used in the development of advanced materials systems because of their outstanding mechanical, structuring, and thermal properties; they are also potent viscosifiers at relatively low concentrations (~0.5 wt %). This paper explores the rheological, thermal, and fluid loss properties of as-produced and covalently modified cellulose nanofibers in saline water-based fluids. Results are compared to a commercial xanthan gum viscosifier as used in saline water-based drilling fluids.
Cellulose nanofibrils were produced from kraft pulp wood fibers by using known methods based on mechanical shearing. Using a standard concentration in water, measurements were made of complex rheology, filtration (API LPLT test), and equivalent and total surface charge. The nanocellulose materials were then modified by means of simple chemical reactions to tailor the surface properties, and then compared to the original material. The same battery of tests was run in control experiments performed with a commercial xanthan gum-based viscosifier.
By modifying the surface of nanocellulose with new covalently bound functional groups, a wide range of fluid behaviors was achieved through the control of the resulting changes in surface chemistry. Unlike nanomaterials based on graphitic carbon, such as nanotubes and graphene, cellulose features a natural polymer backbone chemistry having three available hydroxyl sites on each cellulose repeat unit. The secondary alcohol group at position 6 on the β-D-glucopyranose ring is especially well-suited for site-selective reactions, such as oxidation. The new surfaces created with each new functional group provide different modes of interaction with salt ions, water molecules, and other biopolymers in the fluid to change fluid properties.
This work introduces a new renewable, non-toxic, and potentially less expensive alternative to synthetic polymers for viscosity and filtration control in high-performance water-based drilling and completion fluids. Furthermore, nanocellulose materials can be modified through simple chemical reactions to provide improved performance or to tailor their effects and interactions with other components.