Prevention of hematite settling using synthetic layered silicate while drilling high-pressure wells

Hematite (Fe2O3) is used as a weighting material to increase the density of the drilling fluid. Hematite has a higher density (5.05 g/cm(3)) compared with barite (4.2 g/cm(3)). Because of the high specific gravity and particle size, hematite can separate and settle down at higher temperatures (> 250 degrees F). The objective of this paper is to assess the usage of laponite which is synthetic layered silicate to solve the settling of hematite particles in water-based mud (WBM). Laponite was added to the WBM in different concentrations 0, 0.25, 0.5, 0.75, and 1 lb./bbl. Static and dynamic sag tests were performed to determine the optimum quantity of laponite. The viscoelastic and rheology properties were evaluated to compare between WBM-blank and WBM-laponite. The filtration test was performed at 250 degrees F and 300-psi pressure difference to assess the effect of adding laponite on the filter cake thickness and filtration volume. The results showed that adding 1 lb./bbl of laponite was enough to eliminate the sag issue in both vertical and 45 degrees inclination. The sag factor was reduced from 0.594 to 0.502 at the vertical condition and from 0.62 to 0.51 for the 45 degrees inclined condition. For the dynamic sag, the viscometer sag shoe test (VSST) decreased from 2.1 to 0.21 lb./gal after adding 1 lb./bbl of laponite. It was observed that the apparent viscosity (AV) and yield point (YP) increased by 16% and 33% after adding 1 lb./bbl of the laponite respectively, while there was no change in plastic viscosity (PV) which resulted in increasing the YP/PV ratio which is a good indication of fluid stability and better hole cleaning performance. For the filtration properties, there was no significant change in filter cake thickness and filtration volume.