Water-based bentonite drilling fluids modified by novel biopolymer for minimizing fluid loss and formation damage

Cellulose nanoparticles (CNPs), including cellulose nanocrystals (CNCs) and cellulose nanofibers (CNFs), were used as an environmentally friendly and high performance additive in water-based bentonite drilling fluids for minimizing fluid loss and formation damage. The effects of CNP dimension and concentration on the rheological and filtration properties of the fluids were investigated. With half of the bentonite in the fluid replaced by a small fraction of CNPs, the resultant fluids showed excellent shear thinning behavior and the fluids' viscosity, yield point, and gel strength increased with the concentrations of CNPs. The addition of CNPs did not produce a pronounced effect in loss of the fluids under low temperature and low pressure (LTLP) conditions. However, reduced fluid loss and formation damage were observed with use of CNPs at a higher temperature and pressure condition, demonstrating CNP's potentials for high temperature and high pressure well applications. Additionally, CNCs and CNFs functioned differently in the rheological and filtration properties of the fluids, attributed to their distinct morphology and surface functionality, which could be controlled to maximize the performance of the fluids. (C) 2016 Elsevier B.V. All rights reserved.