A cement slurry prepared on location (or trucked in) cements the well casing. Drilling fluids lubricate the drill bit, remove cuttings, prevent open wellbore collapse and maintain hydrostatic equilibrium for blowout protection. Water- and oil-based "muds" are used. Dispersants, flocculants, surfactants and rust inhibitors may be added to the drilling fluid.
Drilling fluids are typically stored in a series of partitioned, rectangular steel tanks. The tank fluid volume should be continuously monitored since level variations may indicate a pending blowout. Tank conditions include agitated media, suspended solids and media that will coat floats, displacers and probes.