Page 106 - TTEG 19th Edition Directory 2021
P. 106

• CENTRALIZERS: Spring steel guides attached to the casing which help keep it centered in the hole and thus provide for a uniform cement sheath around the casing pipe.
• CHRISTMAS TREE: Valves, pipes, and fittings assembled at the top of a completed well used to control the flow of oil and gas.
• CIRCULATE: Cycling of the drilling fluid through the drill string and wellbore while drilling is temporarily suspended. This is done to condition the drilling fluid and wellbore before drilling proceeds.
• CLOSE IN: To shut in (temporarily) a well that is capable of production.
• COMPLETE A WELL: Finish the work on a well and bring it to a productive state.
• CONDENSATE: Mixture of pentanes and heavier hydrocarbons that may be contaminated with sulfur
compounds and is recovered or recoverable form an underground reservoir. It is gaseous in its virgin
state but is liquid under the conditions at which its volume is measured.
• CONTRACT DEPTH: Depth that well must be drilled to fulfill the contract.
• CORE: Cylindrical sample taken from a formation for the purpose of examination or analysis.
• CRATERING OR SLOUGHING: When the walls of a hole cave in.
• CROOKED HOLE: Wellbore that has deviated from the vertical inadvertently.
• CUTTINGS: Fragments of rock dislodged by the bit and brought to the surface in the drilling mud.
• DERRICK: Load-bearing towerlike framework over an oil/gas well which holds the hoisting and lowering
• DERRICKHAND: Crew member whose work station is in the derrick while pipe is being hoisted or lowered
into the hole. He is usually next in line of authority under the driller.
• DEVELOPMENT WELL: Well drilled for oil and gas within a proven field or area for the purpose of
completing the desired pattern of production.
• DIRECTIONAL DRILLING: Controlled drilling at a specified angle from the vertical.
• DISCOVERY WELL: Exploratory well which discovers a new oil/gas field (see WILDCAT).
• DOGHOUSE: Small house located on the rig floor or nearby that is used as an office for the driller and as
a storage place for small tools.
• DOG LEG: A sharp change of direction in the wellbore or an elbow caused by such a change in direction.
• DOWNTIME: When rig operations are temporarily suspended because of repairs or maintenance.
• DRAWWORKS: Hoisting mechanism on a drilling rig which spools off or takes in the drilling line and thus
raises or l lowers the drill string and bit.
• DRILLERS: Employee directly in charge of a particular crew as opposed to a toolpusher who is in charge
of all the crews on a rig. Operation of drilling and hoisting equipment constitutes the driller’s main duties.
• DRILLING FOREMAN: Usually the man in charge of a number of rigs; sometimes the operator’s
• DRILL PIPE: Steel pipe, in approximately 30-foot (9-meter) lengths, screwed together to form a
continuous pipe extending from the drilling rig to the drilling bit at the bottom of the hole. Rotation of
the drill pipe and bit causes the bit to bore through the rock.
• DRILL STEM TEST (DST): Conventional method of testing a formation to determine its potential
productivity before installing production casing in a well. A testing tool is attached to the bottom of the drill pipe and placed opposite the formation to be tested which has been isolated by placing packers above and below the formation. Fluids in the formation are allowed to flow up through the drill pipe by establishing an open connection between the formation and the surface.
• DRILL STRING: String of individual joints of pipe that extends from the bit to the kelly and carries the mud down to, and rotates, the bit.

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