Rig Glossary: M–P


Make-Up or Breakout Cylinders/Winches

Hydraulic cylinders/winches on each side of the drawworks that supplies the pulling force to the tongs.

Make-Up Tongs

Large wrench like tool suspended from the derrick on the Driller side of the rotary table that is used to make-up and torque up the different drill string components.


An accessory system of piping to a main piping system that serves to divide a flow into several parts, to combine several flows into one, or to reroute a flow to any one of several possible destinations.


A portable derrick that is capable of being raised as a unit, as distinguished from a standard derrick, which cannot be raised to a working position as a unit. For transporting by land, the mast can be divided into two or more sections to avoid excessive length extending from truck beds on the highway. Also called the “Derrick”.

Master Bushing

A device that fits into the rotary table to accommodate the slips and drive the kelly bushing so that the rotating motion of the rotary table can be transmitted to the kelly.

Matting Board

A portable platform used to support equipment. It may also be used as a structural roadway to provide passage over unstable ground.

Mechanical Rig

A drilling rig in which the source of power is one or more diesel engines and in which the power is distributed to rig components through mechanical devices (such as chains, sprockets, clutches, and shafts).

Mix Mud

To add additional chemicals to the drilling fluid system.

Mixing Manifold

Also called “steam mixer” or “water mixer” is simply an enclosed chamber that is used for mixing water and steam. 

Monkey Board

The Derrickhand’s working platform. As pipe or tubing is run into or out of the hole, the Derrickhand must handle the top end of the stand, which may be as high as 90 feet (27 metres) or higher in the derrick or mast.

Monkey Board Fingers

A rack that supports the stands of pipe being stacked in the derrick or mast. It has several steel finger like projections that form a series of slots into which the Derrickhand can place a stand of drill pipe or collars after it is pulled out of the hole and removed from the drill string.


A drilled hole beside the cellar that extends slightly below the ground, to enable a closed end steel pipe to be inserted. A hole behind the rotary table used for holding joints of pipe while making connections.

Mousehole Connection

The procedure of adding a length of drill pipe to the active drill string.

Mud-Can/Mud Bucket

Device used to enclose pipe connections to deflect fluid released when a joint or stand of pipe containing liquid (wet string) is unscrewed.

Mud-Gas Separator

A device that removes gas from the mud coming out of a well when a kick is being circulated out.

Mud-Density Scale

A scale used to measure the density of a drilling fluid expressed as pounds per gallon, pounds per cubic foot, or kilograms per cubic metre. Mud weight is directly related to the amount of pressure the column of drilling mud exerts at the bottom of the hole. Also referred to as a mud balance.

Mud Line

A high-pressure steel line that mud flows through from the kicker hose to the stand pipe. The stand pipe goes up the side of the derrick.

Mud Pump

A large, high-pressure reciprocating pump used to circulate the mud on a drilling rig. A typical mud pump is a two or three-cylinder piston pump whose replaceable pistons travel in replaceable liners and are driven by a crankshaft actuated by an engine or a motor. Also called a “Triplex” or Duplex” pump.

Mud Tank

Open steel tanks used for holding drilling fluids. Some mud tanks are used for suction to the mud pumps, settling of mud sediments, and storage of reserve mud. A series of open tanks usually made of steel plate, through which the drilling mud is circulated through to remove sand and fine sediments. Also called “mud pits”.




A tubular pipe fitting threaded on both ends used for making connections between pipe joints and other tools.




A simple or complex liquid mixture of hydrocarbons that can be refined to yield gasoline, kerosene, diesel fuel, and various other products.

Oil-Base Mud

A drilling mud, such as oil-base mud or invert-emulsion mud, in which oil is the continuous phase and water is the dispersed phase. It is useful in drilling certain formations that may be difficult or costly to drill with waterbase mud.

Open Hole

1) Any wellbore in which casing has not been set.
2) Open or cased hole in which no drill pipe or tubing is suspended.
3) The portion of the wellbore that has no casing.

Out-Of-Gauge Hole

A hole that is not in gauge; that is, it is smaller or larger than the diameter of the bit used to drill it.


A circular seal common in the oil field. O-rings may be made of elastomer, rubber, plastic, or stainless steel. To seal properly, they all require enough pressure to make them deform against a sealing surface.




A material used in a cylinder on rotating shafts of an engine or pump in the stuffing box of a valve, or between flange joints to maintain a leak proof seal.

Personal Protective Equipment (PPE)

Protective clothing or equipment designed to protect the wearer’s body from job related hazards. Minimum required PPE: hardhat, safety glasses, fire retardant coveralls (FRC’s), and steel-toed boots. Additional PPE may be required depending on the job or task, such as a respirator, SCBA, face shield, apron, rubber gloves, etc.

Pick-Up Subs

Short subs that allow larger sized tubulars to be hoisted or lowered by the single sized elevators.


The male external threaded section of a tool joint. Or on a bit, the threaded bit shank.

Pinch Point

The area between two moving objects where body parts or other materials may be pinched. May also be between one moving item and one stationary item.


A long, hollow cylinder, usually steel, through which fluids are conducted. Oilfield tubular goods are casing (including liners), or drill pipe.

Pipe Dope

See Drill Collar Dope.

Pipe Racks

Horizontal supports for tubulars.

Pipe Spinner

A hydraulic or pneumatic wrench that is used to make up or breakout drill pipe, tubing, or casing on which the torque is provided by air or fluid pressure.

Pipe Tubs

Storage bins for drill pipe. Some may be hydraulic that elevate the drill pipe into position to be rolled onto the catwalk.

Pipe Upset

That part of the pipe that has an abrupt increase of dimension.

Pit-Level Indicator

One of a series of devices that continuously monitor the level of the drilling mud in the mud tanks. The indicator usually consists of float devices in the mud tanks that sense the mud level and transmit data to a recording and alarm device (a pit-volume recorder) mounted near the Driller’s position on the rig floor. If the mud level drops too low or rises too high, the alarm may sound to warn the Driller of lost circulation or a kick.

Plumb Bob

A weight, usually with a pointed tip on the bottom, which is suspended from a string and used as a vertical reference line, or plumb-line. It is essentially the vertical equivalent of a “water level”.

Polycrystalline Diamond Compact (PDC) Bit

A special type of diamond enhanced drilling bit that does not have any moving parts. Also called a drag bit.

Pulsation Dampener

An air or inert gas device that minimizes pressure surges in the output line of a mud pump. Also called a surge dampener.

Pump Seats and Valves, Liners

A device used to restrict fluid flow to one direction. It consists of a polished sphere, or ball, usually of metal, an annular piece, the seat, ground and polished to form a seal with the surface of the valve. Gravitational force or the force of a spring holds the ball against the seat. Liners are a cylinder shape pump part that a rubber swab runs in order to pump fluid.

Courtesy of Ensign Drilling Inc.