Hectorite Inorganic Nanoparticle as a Shear-Thixotropic Plugging Agent in Water-Based Drilling Fluids

In this research, we demonstrated an artificial nano-scale clay particles, Hectorite, as a shear-thixotropic plugging agent for lost circulation control in water-based drilling fluids. We compared the shear-thixotropic properties of hectorite and other nanoparticles, as well as the inorganic plugging properties of hectorite and CaCO3 in water-based drilling fluids. In stress-shear rate test, the rheological models of several nanoparticles were consistent with H–B model, but Hectorite had the highest R2 value of 0.97. According to the fitting results, Hectorite had an intermediate n value with good shear-thinning behavior, which was also confirmed by the viscosity-shear rate test, the largest k value with the best thickening properties, and a higher yield point of 6.44 Pa with better suspension performance. In thixotropic test, the recovered G′ of 1% Hectorite in three interval thixotropy test (3ITT) performed better than other nanoparticles, and its thixotropic ring area had the biggest value at 3089 Pa/s. In particle plugging tests (PPT), 0.8% Hectorite (6.8 mL) leaked less than 2% CaCO3 (72.5 mL) in 40–60 mesh quartz sand at 90 °C and 4 MPa after 30 min. The flat surface of the Hectorite filter cake was seen in SEM pictures, which helped to explain its effective plugging properties.