Effect of Qusaiba shale formation on high-pressure high-temperature drilling fluids properties

Abstract

Drilling operations encounter various problems, many of which affect mud quality and may delay or suspend drilling. Wellbore instability is one of the many problems that drilling engineers face while using water-based drilling fluids (WBDF). When WBDFs contact active clay minerals, they may hydrate and swell, damaging the wellbore. In this study, the effects of Saudi Qusaiba shale kaolin clay on WBDF characteristics were examined. Kaolin clay was used as drilled formation cutting at different concentrations (5, 10, 20, and 30 lb/bbl). A detailed study examined how kaolin clay affects mud. Drilling fluid density, alkalinity, rheological, viscoelasticity, filtration behavior, and particle settling were examined before and after adding kaolin clay particles. Experimentally, the higher temperature of the practical environment was simulated by bringing the temperature up to 250 °F. The results showed that there are two clusters of kaolin clay below and above 10 lb/bbl. Kaolin clay concentrations over 10 lb/bbl had a negative effect on fluid characteristics, whereas lower amounts had very little effect. The apparent viscosity (AV) increased by 3% and 16% at 5 and 10 lb/bbl, but it jumped to 72% and 89% after 20 and 30 lb/bbl of kaolin clay. At 20 and 30 lb/bbl of kaolin clay, the yield point (YP) increased by 213% and 377%, respectively. Time sweep indicated continual gel strength increase. The addition of kaolin clay reduced the alkalinity of the WBDF which allowed the clay minerals to swell. Furthermore, the filter cake thickness and filtration volume showed a gradual increment as the concertation of the kaolin clay increased due to the accumulation of the clay solid in the filter cake layer.