Evaluation of the Effects of Kaolin Clay on the Performance of Barite-Weighted Oil-Based Drilling Fluid.

Drilling fluid is an essential component that helps keep the wellbore stable during fast drilling operations. However, problems arise when drilling fluids are contaminated with cuttings from the drilled formation, which impacts the wellbore integrity and fluid characteristics. The effectiveness of drilling operations depends on understanding and managing this relationship correctly. This study examined the influence of kaolin clay as drilling cuttings on barite-weighted oil-based drilling fluid (OBDF). Different quantities of kaolin clay (0, 5, 10, and 15 wt %) were intentionally added as impurities to the OBDF. The evaluation included important characteristics of drilling mud post-hot rolling such as fluid density, emulsion stability, rheology, and filtration performance under high-pressure and high-temperature (HPHT) conditions. The rheological behavior exhibits a gradual change at low solid concentrations but has a rapid increase as the percentage of solids becomes higher. The addition of kaolin clay, comprising less than 10 wt %, had no discernible impact on the yield point (YP). However, 15 wt % of kaolin clay increased the YP by 81%. Furthermore, the increase in gel strength is more pronounced at 10 and 15 wt %. Additionally, plastic viscosity (PV) increased by 19, 35, and 73% when adding 5, 10, and 15 wt % of kaolin clay solids. Incorporating kaolin clay led to increases in both the thickness of the filter cake and the filtrate amount. Kaolin clay reduced the electrical stability but sustained over 400 V at various concentrations. This study emphasizes the importance of understanding formation-drilling fluid interactions for successful drilling operations. Tailoring drilling fluids to specific formations, such as controlling clay content, can ensure wellbore stability and efficient drilling.