Gilsonite additive is an asphaltene hydrocarbon in granular form. Its particle size varies between 4- and 100-mesh. Gilsonite additive is commonly used to control lost circulation. It is effective at bottomhole temperatures (BHTs) between 60° and 230°F (16° and 110°C). Typical additive concentrations range from 5- to 50-lb/sk of cement. The low specific gravity of Gilsonite additive helps improve its ability to control lost circulation. However, this feature can also cause the additive to separate to the top of thin slurries and slurries containing dispersants. Adding 2% or more bentonite to the slurry will help prevent separation.
Gilsonite additive can provide the following benefits:
When perforated, it is shatter-resistant.
It does not significantly affect the setting time of cement.
Gilsonite additive can provide higher strength than heavier additives with high water requirements.