Stability Enhancing of Water-Based Drilling Fluid at High Pressure High Temperature

Over the years, barite (BaSO₄) as weighting agent was widely used. However, it has an issue with particles settling which is known as barite sagging, that causes a variation in drilling fluid properties and operational problems. This study introduces and investigates a novel combination of Micromax (Mn₃O₄) and barite weighting materials to prevent the barite sagging in water-based mud under high pressure high temperature (HPHT) situations. Different amounts of Micromax, 0, 25 and 50 wt% from the total weighting material were added to the field formula. Static and dynamic sagging tests were conducted at 250 °F and 120 °F, respectively, to study the sagging tendency and identify the optimum combination. The mud pH and density were measured at ambient conditions. The rheological properties measurements were conducted at 120 °F and 250 °F. The filtration properties were evaluated using HPHT filtration test at 300 psi and 250 °F. The results showed that adding 25/75 wt% Micromax/barite is enough to eliminate the sag issue in both vertical and 45° inclined position, as it enforced the sagging tendency to the safe range. The 25/75 wt% Micromax/barite has no significant effect on the rheological properties compared to the 100 wt% barite, except for the 30 min gel strength which was increased by 19% for better particles suspension while no circulation. The HPHT filtration test indicated a significant decrease in the filter cake thickness and weight with the 25/75 wt% Micromax/barite without significant change in the filtration volume compared to the 100 wt% barite.