Examining the Effect of Carbon-Based Nanomaterials on the Electrical Resistivity, Rheological Properties, and Cuttings Carrying Index of Bentonite-Based Drilling Fluids

Abstract When the circulating drilling fluid cannot exert enough hydrostatic pressure to prevent formation fluids from entering the wellbore and carrying drill cuttings, or when mud filtrate invades a drilling formation, it alters its physicochemical properties, causing wellbore instability and uneconomic drilling outputs. Nanomaterials have improved water-based drilling fluids rheology, filtration, and cuttings removal. However, more research needs to be performed on how nanomaterials can be used to quantify the physical properties of a fluid–rock system by measuring their electrical resistivity and cuttings transport performance. This research investigates the impact of electrical resistivity, rheological characteristics, and the cuttings-carrying index (CCI) of water-based bentonite drilling mud (BF mud) modified with carbon-based nanoparticles (CNPs) at varying temperatures. Bentonite (BT) concentration was varied from 2 to 6% by water weight at 25, 50, 75, and 100 °C. The CNPs were varied at 0.25, 0.50, and 0.75% by the total weight of the drilling mud to alter the rheological properties, improve the CCI, and decrease the electrical resistivity of the BF. The power law rheological model was used to characterize the rheological behavior, and results demonstrated that all the mud formulations exhibited non-Newtonian pseudoplastic behavior and remain preferred for drilling muds because their flow behavior index and consistency factor are within the field limits. The results also indicate that the electrical resistivity of the BF mud decreased with increasing temperature, BT content, and CNP content. With a CNP content of 0.75% at 85 °C, the electrical resistivity of 6% BT of 4.5 Ω-m reduced to 2.4 Ω-m by 46.7%, indicating the CNP's potential to seal permeable zones and prevent expensive loss of drilling muds. In addition, at an elevated temperature of 100 °C, the PV of the BF mud with 0.75% of CNPs in 6% BT increased from 6.6 to 15.1 cP by 56.3%, highlighting the effect of increased surface area to volume ratio and Brownian motion exerted by the CNPs. At all temperature ranges, the CNPs significantly enhanced the BF's CCI as their content increased. The study showed that CNPs improved the formation of the rock-BF system's rheology, cutting removal, and resistivity. These changes improved the drilling process and the physicochemical characteristics of the drilling fluid.