The two primary purposes of drilling mud or drilling fluids are to :

1. Remove cuttings from the formation produced by the bit at the bottom of the hole and carry them to the surface. This is achieved by adjusting the rheology of the mud system.

2. Maintain hydrostatic equilibrium so that fluids and gas from the formation do not enter the well bore causing the well to flow, kick or blow out. This is achieved by adjusting the mud weight (density). High-density additives (barite, hematite) are used for preparation of kill-weight fluids, which create hydrostatic pressure that prevents water entering the well or hold the oil/gas inside and prevent blowout, and to physically stabilize the formation.

Purpose

The two primary purposes of drilling mud or drilling fluids are to :

1. Remove cuttings from the formation produced by the bit at the bottom of the hole and carry them to the surface. This is achieved by adjusting the rheology of the mud system.

2. Maintain hydrostatic equilibrium so that fluids and gas from the formation do not enter the well bore causing the well to flow, kick or blow out. This is achieved by adjusting the mud weight (density). High-density additives (barite, hematite) are used for preparation of kill-weight fluids, which create hydrostatic pressure that prevents water entering the well or hold the oil/gas inside and prevent blowout, and to physically stabilize the formation.

Other characteristics are considered important in modern drilling. Some of these include :

• Safe for the environment

• Prevent dispersion of reactive clays (gumbo)

• Ability to seal formation fractures/voids

• Non abrasive to tools and rig equipment

• Seal porous rock layer, equalize the pressure, cooling the bit, flush out the cutting & lubricating the bit

Details of Use

On a drilling rig pumping it with mud pumps through the drill string where it sprays out of nozzles on the drill bit (cleaning the bit in the process), the mud then travels back up the annular space between the drill string and the sides of the hole being drilled, up through the surface casing, and emerges at the surface.

Cuttings are then filtered out at the shale shaker and the mud enters the mud pits.

The mud is then pumped back down and is continuously recirculated. The mud is treated periodically in the mud pits to give it properties that optimize and improve drilling efficiency.