National Oilwell Varco 2015 Annual Report Download - page 30

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Table of Contents
Riser A pipe through which liquids travel upward.
Riser pipe The pipe and special fitting used on floating offshore drilling rigs to established a seal between
the top of the wellbore, which is on the ocean floor, and the drilling equipment located above the
surface of the water. A riser pipe serves as a guide for the drill stem from the drilling vessel to the
wellhead and as a conductor or drilling fluid from the well to the vessel. The riser consists of
several sections of pipe and includes special devices to compensate for any movement of the
drilling rig caused by waves. Also called marine riser pipe, riser joint.
Rotary table The principal piece of equipment in the rotary table assembly; a turning device used to impart
rotational power to the drill stem while permitting vertical movement of the pipe for rotary
drilling. The master bushing fits inside the opening of the rotary table; it turns the kelly bushing,
which permits vertical movement of the kelly while the stem is turning.
Rotating blowout preventer (Rotating Head) A sealing device used to close off the annular space around the kelly in drilling with pressure at
the surface, usually installed above the main blowout preventers. A rotating head makes it
possible to drill ahead even when there is pressure in the annulus that the weight of the drilling
fluid is not overcoming; the head prevents the well from blowing out. It is used mainly in the
drilling of formations that have low permeability. The rate of penetration through such
formations is usually rapid.
Safety clamps A clamp placed very tightly around a drill collar that is suspended in the rotary table by drill
collar slips. Should the slips fail, the clamp is too large to go through the opening in the rotary
table and therefore prevents the drill collar string from falling into the hole. Also called drill
collar clamp.
Shaker See “Shale Shaker”
Shale shaker A piece of drilling rig equipment that uses a vibrating screen to remove cuttings from the
circulating fluid in rotary drilling operations. The size of the openings in the screen should be
selected carefully to be the smallest size possible to allow 100 per cent flow of the fluid. Also
called a shaker.
Slim-hole completions (Slim-hole Drilling) Drilling in which the size of the hole is smaller than the conventional hole diameter for a given
depth. This decrease in hole size enables the operator to run smaller casing, thereby lessening the
cost of completion.
Slips Wedge-shaped pieces of metal with serrated inserts (dies) or other gripping elements, such as
serrated buttons, that suspend the drill pipe or drill collars in the master bushing of the rotary
table when it is necessary to disconnect the drill stem from the kelly or from the top-drive unit’s
drive shaft. Rotary slips fit around the drill pipe and
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