1. n. [Drilling Fluids]

A generic name widely used for a black, lustrous, carbonaceous resin classified as an asphaltite. Its proper name is uintaite, and it is found in Utah, USA. An important characteristic of gilsonite is its softening-point temperature. In oil-base muds, it is used as a fluid-loss control agent. Being a hydrocarbon, it is naturally wetted by the oil. In water-base muds, it is used as a shale-stabilizing additive and is difficult to evaluate unless tested at or above its softening point. As a hydrocarbon, the powder must be coupled to water by using a glycol or similar water-wetter.

See: fluid-loss control,  low-colloid oil mud,  oil-base mud,  water-based drilling fluid,  water-wet,  wettability

2. n. [Drilling Fluids]

A trademarked product of American Gilsonite Co.