Using Gilsonite in Oil-Based and Synthetic Muds

Oil-based muds (OBM) and synthetic-based muds (SBM) give excellent shale inhibition, but fluid loss and wellbore strengthening still need attention. Gilsonite is one of the most common fluid loss additives in these systems.

Why gilsonite suits OBM

Gilsonite is partly soluble and partly dispersible in oil. At downhole temperature, the particles soften and seal pores, providing very low HPHT filtrate.

Typical dosage

4–10 lb/bbl, depending on temperature and fluid loss target.

Mixing tips

• Add to the active system slowly through the hopper.
• Allow shear and time for dispersion.
• For high concentrations, pre-mix in a pill tank.

Effect on rheology

Gilsonite can slightly increase viscosity in OBM. Monitor plastic viscosity and yield point, and adjust organophilic clay as needed.

Choosing softening point

Use a grade with a softening point a little above bottom-hole temperature for best sealing. See selecting softening point for wells.

Example calculation

For a 1,200 bbl OBM system treated at 6 lb/bbl:
1,200 × 6 = 7,200 lb ≈ 3,270 kg ≈ 131 bags of 25 kg.

Monitoring checklist

Product

Our drilling fluid grade gilsonite is supplied in 25 kg bags and 1 MT jumbo bags.