Properly designed drilling fluid is a key element in achieving safe and effective drilling operations. Rheological parameters of drilling fluid determine the equivalent circulation density, the pump pressure, and hole cleaning efficiency. Also, they have a significant role in predicting the stability of drilling fluid under static and low shear rates. The chemical composition of the drilling fluid controls the rheological parameters. Recently, studies have shown that a small concentration of nanosized materials in the drilling fluid can substantially impact the rheological parameters of the drilling fluids.

In this study, various nanoparticles (NPs) with different shapes, sizes, and surface charges were used to investigate their impact on the viscous properties of water-based drilling fluid. Bentonite and KCl water-based drilling fluids were used as the base fluids. NPs such as Iron oxide, Silica (SiO2), and multi-walled carbon nanotubes (MWCNT) were added to these base fluids. Also, surface functionalization of the NPs with polymer and functional groups such as -OH and -COOH groups was done to compare the effect of bare NPs with surface functionalized NPs. Hershel-Buckley model with dimensionless shear rates was used to calculate the low and high shear curvature exponents, surplus stress, and yield stress of the samples.

Results indicate that NPs alter drilling fluid’s viscous properties based on their sizes, shapes, and surface charges. Moreover, the functionalization of NPs also modifies the properties based on the functional group attached to the NPs surface. This work shows that changing the size, shape, and surface charge of NPs has impact on viscous parameters, and NPs with different properties can fine-tune the fluid’s viscous properties based on the requirement for drilling fluid.

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