Oil & Gas Terms in Category C

Cement channel

A channel in the cement, usually caused by poor displacement of drilling mud.

Chisel tongs

Pipe tongs that grip the pipe with a chisel-like insert in the jaw of the wrench.


A finger-like device used to lock or position certain tool components by manipulating the tubing string or downhole tool

Caustic soda

Sodium hydroxide.

Used to maintain an alkaline ph in drilling mud and in petroleum fractions.

Cameron gauge

Generically, a pressure gauge usually used in lines or manifolds.

Many companies make pressure gauges.

Cameron, now cooper oil tools, makes many types of gauges.


To deepen the wellbore by way of collecting a cylindrical sample.

A core bit is used to accomplish this, in conjunction with a core barrel and core catcher.

The bit is usually a drag bit fitted with either pdc or natural diamond cutting structures, but the core bit is unusual in that it has a hole in its center.

This allows the bit to drill around a central cylinder of rock, which is taken in through the bit and into the core barrel.

The core barrel itself may be thought of as a special storage chamber for holding the rock core.

The core catcher serves to grip the bottom of the core and, as tension is applied to the drillstring, the rock under the core breaks away from the undrilled formation below it.

The core catcher also retains the core so that it does not fall out the bottom of the drillstring, which is open in the middle at that point.

Calcium chloride

A moisture-absorbing chemical compound, or desiccant used to accelerate setting times in cement and as a drying agent.


Pertaining to a wellbore in which casing has been run and cemented.

See casing.

Concentric tubing workover

A workover performed with a small-diameter tubing work string inside the normal tubing.

Equipment needed is essentially the same as that for a conventional workover except that it is smaller and lighter.

Casing string

The entire length of all the joints of casing run in a well.

Most casing joints are manufactured to specifications established by api, although non-api specification casing is available for special situations.

Casing manufactured to api specifications is available in three length ranges.

a joint of range 1 casing is 16 to 25 feet long; a joint of range 2 casing is 25 to 34 feet long; and a joint of range 3 casing is 34 to 48 feet long.

The outside diameter of a joint of api casing ranges from 4 1/2 to 20 inches.


A hoisting or pulling line operated from a cathead.

Channel (cement)

A flow area in the cement from inefficient cementing displacement of the drilling mud.

Cement plug

A portion of cement placed at some point in the wellbore to seal it.

See cementing.

Carboxymethyl cellulose

A non-fermenting cellulose product used in drilling fluids to combat contamination from anhydrite (gypsum) and to lower the water loss of the mud.

Casing pack

A means of cementing casing in a well so that the casing may, if necessary, be retrieved with minimum difficulty.

A special mud, usually an oil mud, is placed in the well ahead of the cement after the casing has been set.

Non-solidifying mud is used so that it does not bind or stick to the casing in the hole in the area above the cement.

Since the mud does not gel for a long time, the casing can be cut above the cemented section and retrieved.

Casing packs are used in wells of doubtful or limited production to permit reuse of valuable lengths of casing.