Improvement of Static and Dynamic Sag Performance of Water-Based Drilling Mud Using Combined Nano-Barite and Nano-Ilmenite Particles

Abstract Barite sag poses a considerable challenge in the drilling of high-temperature and high-pressure (HTHP) wells under static and dynamic conditions. Barite particles detach from the base drilling mud during this process. This leads to changes in the weight of the drilling mud, which may result in severe well control problems, including mud loss, borehole instability, and pipe sticking. This study used a synthesized weighing agent comprising combined nano barite (nBaSO4) and nano ilmenite (nFeTiO3), which was subsequently integrated into water-based drilling mud (WBDM) to mitigate barite sagging. The high area-to-volume ratio of the synthesized weighting components necessitates only small quantities of weighting materials to formulate optimal gravity drilling mud. Drilling mud samples were formulated by incorporating different concentrations (0.2, 0.5, and 0.8 lb/bbl) of nFeTiO3 into a base mud consisting of weighted nBaSO4. Static and dynamic tests were conducted at 120 °C and 49 °C, respectively, to assess the sag tendency of the nBaSO4 mud systems and to identify the optimal weight concentration of nFeTiO3 for sag mitigation. The mud systems were measured by measuring the mud pH, density, and rheological properties at 49 °C. A filtration test was performed at 120 °C to determine the influence of nFeTiO3 on nBaSO4 wellbore sealing effectiveness. The research showed that adding nFeTiO3 to nBaSO4-weighted drilling mud made the mud denser and lowered the pH to the best range of 9.5–11.5. Under 49 °C temperature conditions, there was an appreciable increase in the rheological properties of the nBaSO4-based drilling mud with an increasing weight concentration of nFeTiO3. Adding nFeTiO3 to the nBaSO4-based mud resulted in a significant decrease in the sag factor. 0.8 lb/bbl nFeTiO3 effectively inhibited barite drooping under static and dynamic sag conditions, resulting in sag factors of 0.511 and 0.38, respectively. HTHP filtration data demonstrated that nFeTiO3 did not significantly influence the filtration efficiency of nBaSO4. This study found that using combined nBaSO4 and nFeTiO3 could help stop barite sag problems and improve wellbore stability. Deploying this mud under HTHP conditions could be effective, economical, and safe.