1. n. [Drilling]

A variation of air drilling in which a small amount of water trickles into the wellbore from exposed formations and is carried out of the wellbore by the compressed air used for air drilling. The onset of mist drilling often signals the impending end of practical air drilling, at which point the water inflow becomes too great for the compressed air to remove from the wellbore, or the produced water (usually salty) becomes a disposal problem.

See related terms: air drilling,  mist