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

Abstract

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.