Oil & Gas Terms in Category B

Bob tail

Any short truck.


A device used to blend slurries or gels, usually mobile equipment.

Bridge over

A phenomenon that sometimes occurs when a well blows out.

Rocks, sand, clay, and other debris clog the hole and stop the blowout.

Blank liner

A liner without perforations.


A definite amount of oil, mud, acid, or other liquid in a tank or pipe.

Bradenhead gas

Commonly called casinghead gas; gas that is produced with oil or from the casing head of an oil well.


Heavy lifting mechanism used on rigs to provide a mechanical pulling and running advantage.

Bradenhead squeeze

A process used to repair a hole in the casing by pumping cement down tubing or drill pipe.

First, the casinghead, or bradenhead, is closed to prevent fluids from moving up the casing.

Then the rig’s pumps are started.

Pump pressure moves the cement out of the tubing or pipe and, since the top of the casing is closed, the cement goes into the hole in the casing.

The tubing or pipe is pulled from the well and the cement allowed to harden.

The hardened cement seals the hole in the casing.

Although the term “bradenhead squeezing” is still used, the term “bradenhead” is obsolete.

See annular space, casinghead, squeeze.


A device employed to catch debris from drillable tools, perforators, and so on

Bottoms up


A complete trip from the bottom of the wellbore to the top


Pertaining to the mud and cuttings that are calculated or measured to come from the bottom of the hole since the start of circulation.

Circulation may be initiated after a static period, such as a trip, or from a given depth while drilling.

This latter type is particularly useful to mud loggers and others trying to discern the lithology being drilled, so mud loggers or mud engineers often retrieve what is referred to as a “bottoms-up sample” of the cuttings or the drilling fluid.


The sample obtained at the bottoms-up time or a volume of fluid to pump, as in “pump bottoms-up before drilling ahead.”




A valve or pipe through which bleeding is done.


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.

Bump down

To have too long a length of rods between the pumping unit and the pump seat so that the pump hits bottom on the down stroke.

Bumper jar

A device made up in the drill string that, when actuated, delivers a heavy downward blow to the string.

A bumper jar has a hollow body that moves upward when the drill string is picked up.

When the string is dropped quickly, the jar body produces a sharp downward blow on the tubing or pipe made up below the jar.

If downward blows can free a fish, a bumper jar can be very effective.

Bull plug

A threaded nipple with a rounded, closed end used to stop up a hole or close off the end of a line.