Oil & Gas Terms in Category W

Water block


A reduction in the permeability of a formation caused by the invasion of water into the pores.


A relative permeability problem usually occurring in a gas zone.

Highest potential formations for water blocks are low pressure gas sands (<0.25 psi/ft pore pressure), with small pore throats (<10 microns), lower permeability (<100 md), and when using water that has a surface tension about 50 dyne/cm.

Well logging

The recording of information about subsurface geologic formations, including records kept by the driller and records of mud and cutting analyses, core analysis, drill stem tests, and electric, acoustic, and radioactivity procedures.

See acoustic log, core analysis, driller’s log, drill stem test, electric well log, mud analysis, and radioactivity well logging.

Weak link (coiled tubing)

A weak point at the top of the bha, designed to separate before the tubing fails if the bha becomes stuck.


Abbreviation: waiting-on-engineering

Wireline probe

A diagnostic tool used to ascertain the position of a gas leak in the tubing of a gas-lift well.

Wireline entry guide

A flared-end sub run on the end of the tubing string to permit easy access of wireline tools into the tubing id.



A short length of surface-hardened pipe that fits inside the swivel and serves as a conduit for drilling fluid through the swivel.


Sometimes used to mean washover pipe.


To perform one or more of a variety of remedial operations on a producing oil well to try to increase production.

Examples of workover opera6tions are deepening, plugging back, pulling and resetting liners, squeeze cementing, and so on.


Broken or frayed strands of the steel wire that makes up the outer wrapping of wire rope.

Wireline feeler

A tool used to gauge and clean junk and debris from the casing in conjunction with a junk catcher.



A well drilled in an area where no oil or gas production exists.


(nautical) the geared sheave of a windlass used to pull anchor chain.

v: to drill wildcat wells.


The operation during which stuck drill stem or tubing is freed using washover pipe.


Shortened form of boll weevil.

See boll weevil.

Wireline probe

A diagnostic tool used to ascertain the position of a gas leak in the tubing of a gas lift well.

Wash over

To release pipe that is stuck in the hole by running washover pipe.

The washover pipe must have an outside diameter small enough to fit into the borehole but an inside diameter large enough to fit over the outside diameter of the stuck pipe.

A rotary shoe, which cuts away the formation, mud, or whatever is sticking the pipe, is made up on the bottom joint of the washover pipe, and the assembly is lowered into the hole.

Rotation of the assembly frees the stuck pipe.

Several washovers may have to be made if the stuck portion is very long.