1. Steel pipe placed in an oil or gas well as drilling progresses to prevent the wall of the hole from caving in during drilling, to prevent seepage of fluids, and to provide a means of extracting petroleum if the well is productive.

2. Large-diameter pipe lowered into an openhole and cemented in place. The well designer must design casing to withstand a variety of forces, such as collapse, burst, and tensile failure, as well as chemically aggressive brines. Most casing joints are fabricated with male threads on each end, and short-length casing couplings with female threads are used to join the individual joints of casing together, or joints of casing may be fabricated with male threads on one end and female threads on the other. Casing is run to protect fresh-water formations, isolate a zone of lost returns or isolate formations with significantly different pressure gradients. The operation during which the casing is put into the wellbore is commonly called “running pipe.” Casing is usually manufactured from plain carbon steel that is heat-treated to varying strengths, but may be specially fabricated of stainless steel, aluminum, titanium, fiberglass and other materials.

Related Terms

• Die Collar

n: a collar or coupling of tool steel, threaded internally, that can be used to retrieve pipe from the well on fishing jobs; the female counterpart of a taper tap. The die collar is made up on the drill pipe and lowered into the hole until it contacts the lost pipe. If the lost pipe...

• Tool Joint

a heavy coupling element for drill pipe. It is made of special ahoy steel and has coarse, tapered threads and seating shoulders designed to sustain the weight of the drill stem, withstand the strain of frequent coupling and uncoupling, and provide a leakproof seal. The male section of the joint, or the pin, is attached...

• Conductor Casing

generally, the first string of casing in a well. It may be lowered into a hole drilled into the formations near the surface and cemented in place; or it may be driven into the ground by a special pile drive (in such cases, it is sometimes called drive pipe); or it may be jetted into...

• Bridge Plug

1. 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. 2. A downhole tool that is located and set to isolate the lower part of the wellbore. Bridge plugs...

• Tap

1. a tool for forming an internal screw thread. It consists of a hardened tool-steel male screw grooved longitudinally so as to have cutting edges. 2. a hole or opening in a line or vessel into which a gauge or valve may be inserted and screwed tight. v.1. to form a female thread by means...