The removal of solids is necessary before a drilling fluid can be returned to the drill bit. Recirculated drilling fluids must be returned to as near the optimum drilling properties as economically practical. The more effective the mechanical solids removals, the less dilution and chemical treatment is required. If the total annular return is discarded after one pass by the bit, of course no separation effort is necessary. In most situations this latter is impossible for either economic or ecological consideration, or for both. The basic components of a simple mud circulation system is shown in Figure 1. The components for solids removal are listed as follows:

The removal of solids is necessary before a drilling fluid can be returned to the drill bit. Recirculated drilling fluids must be returned to as near the optimum drilling properties as economically practical. The more effective the mechanical solids removals, the less dilution and chemical treatment is required. If the total annular return is discarded after one pass by the bit, of course no separation effort is necessary. In most situations this latter is impossible for either economic or ecological consideration, or for both. The basic components of a simple mud circulation system is shown in Figure 1. The components for solids removal are listed as follows:

• Suction tanks

• Mud pumps

• Shale shakers

• Hydrocyclone desander

• Hydrocyclone desilter

• Centrifuge

Settling tanks Mud pits are required for holding an excess volume of mud at the surface. The volume mud in the circulating system is usually between 300 and 700 barrels. Mud pits are made of steel, and have dimensions of 5 feet (1.64 m) wide and 40 feet (13.1 m) long and 3 feet (0.98m) deep. Three such pits are usually provided, and they are coupled together with conduits of 12 (305.8 mm) to 18 (457.2 mm) inches diameter pipe. Mud is pumped into these tanks to allow sand to settle and any trapped gas bubbles in the mud to escape. At the edge of the mud pits, mud guns are mounted for jetting down onto the surface of the mud. Mud guns are usually operated by an auxiliary mud-mixing pump.

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