drilling mud: a mixture of clays and chemicals and water; pumped down the drill pipe to lubricate and cool the drilling bit and to flush out the cuttings and to strengthen the sides of the hole
Fluids continuously circulated down the wellbore, to cool and lubricate the drill bit, lubricate the drill pipe, carry rock cuttings to the surface and control down hole pressure
Fluid used to lubricate the bit and convey drill cuttings to the surface with rotary drilling equipment Usually composed of bentonite slurry or muddy water Can become contaminated, leading to cross contamination, and may require special disposal
circulating fluid or gas which forces cuttings out of the wellbore to the surface