24. Kelly Line-Rotary Hose (Mud Hose)

This connects the standpipe to the goose neck and is flexible but strong enough to hold high pressures. These hoses may be pressure rated up to 12,000 psi.

25. Shale Shaker

This is a vibrating screen used to separate the drilled solids from the drilling fluid. The screen is mounted on a spring or rubber supported chassis, which is vibrated by means of an eccentric rotating shaft. Screens of different mesh size are available. Mesh sizes being measured by the number of openings per square inch. The screens are sometimes mounted as a pair, using screens of different sizes.

In double deck Shaker; mud returning from the well core comes down the flowline and into a surge tank; sometimes known as the possum belly or shaker header box; this allows a smooth flow of mud onto the screens. The shakers are usually situated over a sand trap, which is a narrow pit with sloping sides terminating in a valve, it is used to trap fine sand that may pass through the shaker screens, this pit must be dumped out periodically.

26. Desanders and Desilters

These devices remove particles from mud, which were not removed by the shakers or the sand trap. This separation is accomplished by utilising centrifugal force. The equipment is essentially a series of cones mounted on a manifold, mud is pumped into the manifold and enters the cone. The mud swirls round the inside of each cone, this rotating action causes the lighter fluids to come to one centre and rise out of a hole in the top, whereas the heavier soils go to the outside of the cone and sink down it and out of an opening in the bottom. These units are operated at low pressure (30-40 psi) but can handle high volumes, typically 250 gallons per minute per cone. The difference between desanders and desilters is mainly in the size of the cones. The smaller the cones the smaller the particles that it separates.

27. Degassers

These separate the gas that may be trapped in the drilling fluid. The principle of operation is essentially the same even though the design varies. The mud is either passed over a series of baffles or caused to swirl round in a bowl; both actions cause the mud to break up resulting in the greatest surface area possible for the gas to break out. In the swirling action the mud is spread very thinly over a surface. In addition to the increased surface area, some degassers apply a slight vacuum, this aids in the separation as the gas or air bubbles expand and break out of the fluid more easily.

28. Mud Pits

After drilling fluid has been processed by the solids control equipment; it passes into the return pit, that is connected sometimes by other pits to the suction pit. The suction pit is directly connected to the pumps allowing the mud to circulate through this system. Between the return and suction pits the mud is constantly agitated by electric paddle mixers and mud guns.

Chemicals are added to the mud via special hoppers. The suction pit may also contain a small (typically 50 bbls) slug pit used to mix special heavy mud that may be needed when tripping or to mix other small specific volumes. The pits in use are referred to as “Active Pits”. All pits are equipped with valves so that their contents may be dumped or transferred easily in-between them.