Oil and Gas Well Drilling and Servicing » Glossary of Terms - B

This is an abridged version of the Dictionary of Petroleum Terms provided by Petex and the University of Texas Austin. © Petex 2001

v: line with a Babbitt metal. n: a lead/tin alloy with some copper and antimony.

v: reverse backlash of tongs, left on a pipe or collar, during the pipe spinning operations.

back off
v: to unscrew one threaded piece (such as a section of pipe) from another.

back-in unit
n: a portable servicing or workover rig that is self-propelled, using the hoisting engines for motive power. Because the driver's cab is mounted on the end opposite the mast support, the unit must be backed up to the wellhead.

n: 1. a cylindrical steel bar (similar to the handle or bail of a bucket, only much larger) that supports the swivel and connects it to the hook.

n: a long, cylindrical container fitted with a valve at its lower end, used to remove water, sand, mud, drilling cuttings, or oil from a well in cable-tool drilling.

ball-and-seat valve
n: a device used to restrict fluid flow to one direction. It consists of a polished sphere, or ball, usually of metal, and an annular piece, the seat, ground and polished to form a seal with the surface of the ball. Gravitational force or the force of a spring holds the ball against the seat. Flow in the direction of the force is prevented, while flow in the opposite direction overcomes the force and unseats the ball.

v: to plug open perforations by using ball sealers.

n: barium sulfate, BaSO4; a mineral frequently used to increase the weight or density of drilling mud. Its relative density is 4.2 (meaning that it is 4.2 times denser than water). See barium sulfate, mud.

barium sulfate
n: a chemical compound of barium, sulfur, and oxygen (BaSO4), which may form a tenacious scale that is very difficult to remove. Also called barite.

(bbl) n: 1. a measure of volume for petroleum products in the United States. One barrel is the equivalent of 42 U.S. gallons or 0.15899 cubic meters (9,702 cubic inches).

n: a device placed in the drill or work string that catches debris when a drillable object is being milled or drilled downhole.

n: a steel or other structural member.

Beam Pumping Unit

beam pumping unit
n: a machine designed specifically for sucker rod pumping. An engine or motor (prime mover) is mounted on the unit to power a rotating crank. The crank moves a horizontal member (walking beam) up and down to produce reciprocating motion. This reciprocating motion operates the pump.

n: a flexible band or cord connecting and wrapping around each of two or more pulleys to transmit power or impart motion.

belt guard
n: a protective grill or cover for a belt and pulleys.

bent sub
n: a short cylindrical device (generally angular) installed in the drill stem between the bottommost drill collar and a downhole motor.


n: the cutting or boring element used in drilling oil and gas wells.

bit program
n: a plan for the expected number and types of bits that are to be used in drilling a well.

bit record
n: a report that lists each bit used during a drilling operation.

bit sub
n: a sub inserted between the drill collar and the bit.

v: to drain off liquid or gas, generally slowly, through a valve called a bleeder. To bleed down, or bleed off, means to release pressure slowly from a well or from pressurized equipment.


n: one or more pulleys, or sheaves, mounted into a common framework in order to rotate on a common axis. The crown block is an assembly of sheaves mounted on beams at the top of the derrick or mast. The traveling block is an assembly of sheaves mounted in a framework that allows the block to move up and down by use of the drilling line that is reeved over the crown block sheaves and through the traveling block sheaves.

n: an uncontrolled flow of gas, oil, or other well fluids from the well.

Blowout Preventer

blowout preventer (BOP)
n: one or more valves installed at the wellhead to prevent the escape of pressure either in the annular space between the casing and the drill pipe or in open hole (for example, hole with no drill pipe) during drilling or completion operations. See annular blowout preventer and ram blowout preventer.

blowout preventer control panel
n: controls, opens and closes the blowout preventers. See blowout preventer.

blowout preventer control unit
n: a device that stores hydraulic fluid under pressure in special containers and provides a method to open and close the blowout preventers.

blowout preventer stack (BOP stack)
n: the assembly of well control equipment including preventers, spools, valves, and nipples connected to the top of the wellhead.

abbr: blowout preventer.

BOP stack
n: the assembly of blowout preventers installed on a well.

n: 1. the inside diameter of a pipe or a drilled hole. v: to penetrate or pierce with a rotary tool. Compare tunnel.

n: the lowest or deepest part of a well.

bottomhole assembly
n: the portion of the drilling assembly below the drill pipe. It can be very simple, composed of only the bit and drill collars, or it can be very complex and made up of several specialty components.

bottomhole plug
n: a bridge plug or cement plug placed near the bottom of the hole to shut off a depleted, water-producing, or unproductive zone.

bottomhole pressure
n: 1. the pressure at the bottom of a borehole. It is caused by the hydrostatic pressure of the wellbore fluid and, sometimes, by any backpressure held at the surface, as when the well is shut in with blowout preventers. When mud is being circulated, bottomhole pressure is the hydrostatic pressure plus the remaining circulating pressure required to move the mud up the annulus. 2. the pressure in a well at a point opposite the producing formation, as recorded by a bottomhole pressure measuring device.

bottomhole pressure test
n: a test that measures the reservoir pressure of the well, obtained at a specific depth or at the midpoint of the producing zone. A flowing bottomhole pressure test measures pressure while the well continues to flow; a shut-in bottomhole pressure test measures pressure after the well has been shut in for a specified period of time. See bottomhole pressure.

bottomhole pump
n: any of the rod pumps, high-pressure liquid pumps, or centrifugal pumps located at or near the bottom of the well and used to lift the well fluids. See centrifugal pump, hydraulic pumping, submersible pump, sucker rod pumping.

bottom plug
n: a cement wiper plug that precedes cement slurry down the casing. The plug wipes drilling mud off the walls of the casing and prevents it from contaminating the cement. See cementing, wiper plug.

box threads
n pl: threads on the female section, or box, of a tool joint. See tool joint.

n: The braking device on the drawworks or airhoist to stop a load being lifted. It is a device for arresting the motion of a mechanism, usually by means of friction, as in the drawworks and airhoist brakes.


brake band
n: a part of the brake mechanism consisting of a flexible steel band lined with a material that grips a drum when tightened. On drawworks, the brake band acts on the drum to control the lowering of the traveling block and its load.

break circulation
v: to start the mud pump for restoring circulation of the mud column. Because the stagnant drilling fluid has thickened or gelled during the period of no circulation, higher pump pressure is usually required to break circulation.

breaker points
n: contacts that interrupt the current in the primary circuit of an electrical system such as in a spark-ignition engine.

break out
v: 1. to unscrew one section of pipe from another section, especially drill pipe while it is being withdrawn from the wellbore. During this operation, the tongs are used to start the unscrewing operation. 2. to separate, as gas from a liquid or water from an emulsion.

breakout block
n: a plate that fits in the rotary table and holds the drill bit while it is being unscrewed from the drill collar.

breakout cathead
n: a device attached to the catshaft of the drawworks that is used as a power source for the tongs used in unscrewing drill pipe; usually located opposite the driller’s side of the drawworks.

break tour
(pronounced "tower") v: to begin operating 24 hours a day. Moving the rig and rigging up are usually carried on during daylight hours only. When the rig is ready for operation at a new location, crews break tour.

bridge plug
n: a downhole tool, composed primarily of slips, a plug mandrel, and a rubber sealing element, that is run and set in casing to isolate a lower zone while an upper section is being tested or cemented.

n: water that has a quantity of salt, especially sodium chloride, dissolved in it; salt water.

buck up
v: to tighten up a threaded connection (such as two joints of drill pipe).

Bulk Mud Components in Storage

bulk mud components in storage
n: hopper type tanks for storage of drilling fluid components.

bulk tank
n: on a drilling rig, a large metal bin that usually holds a large amount of a certain mud additive, such as bentonite, that is used in large quantities in the makeup of the drilling fluid.

Bullet Perforator

bullet perforator
n: a tubular device that, when lowered to a selected depth within a well, is engaged forcing the projectiles (bullets) through the casing and cement to provide holes through which the formation fluids may enter the wellbore.

adj: in cementing operations, pertaining to a cement plug that comes to rest on the float collar.

bumper block
n: Timbers wrapped with wire mesh or other retaining medium located below the crown to act as a cushion in the event the block is raised too far.

n: 1. a pipe fitting on which the external thread is larger than the internal thread to allow two pipes of different sizes to be connected. 2. a removable lining or sleeve inserted or screwed into an opening to limit its size, resist wear or corrosion, or serve as a guide.