Oil & Gas Glossary 1.0

A logging device used to determine accurately the depth of a well; the log measures and records the depth of each casing collar, or coupling, in a well. Since the length of each joint of casing is written down, along with the number of joints of casing that were put into the well, knowing the number and depth of the collars allows an accurate measure of well depth

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 is stuck so that it cannot rotate, rotation of the die collar on top of the pipe cuts threads on the outside of the pipe, providing a firm attachment. The pipe is then retrieved from the hole. Compare taper tap. It is not often used because it is difficult to release it from the fish should it become necessary.

A tap with a gradually decreasing diameter from the top. It is used to retrieve a hollow fish such as a drill collar and is the male counterpart of a die collar. The taper tap is run into a hollow fish and rotated to cut enough threads to provide a finn grip and permit the fish to be pulled and recovered. See tap. Compare die collar.

A spring-loaded finger in a tubing end locator.

A special coupling device inserted one or two joints above the bottom of the casing string that contains a check valve to permit fluid to pass downward but not upward through the casing. The float collar prevents drilling mud from entering the casing while it is being lowered, allowing the casing to float during its descent and thus decreasing the load on the derrick or mat. A float collar also prevents backflow of cement during a cementing operation.

A special type of nuclear log that measures the depth of each casing collar. Knowing the depth of the collars makes it easy to determine the exact depth of the formation to be perforated by correlating casing-collar depth with formation depth.

Casing collar log

A pipe coupling threaded on the inside.

A slip-type collar that is used to join plain-end pipe.

1. in piping, a metal collar with internal threads used to join two sections of threaded pipe.

To loosen a collar or other threaded connection by striking it with a hammer.

1. to recover from a well any equipment left there during drilling operations, such as a lost bit or drill collar or part of the drill string.

A single length (30 feet or 9 meters) of drill pipe, drill collar, casing, or tubing that has threaded connections at both ends. Several joints screwed together constitute a stand of pipe.

A damping apparatus used to pull tubing. The elevators latch onto the pipe just below the top collar. The elevators are attached to the hook by steel links or bails.

1. a tool placed on a drill collar near the bit that is used, depending on where it is placed, either to maintain a particular hole angle or to change the angle by controlling the location of the contact point between the hole and the collars. See packed-hole assembly.

A heavy, thick-walled tube, usually steel, used between the drill pipe and the bit in the drill stem to provide a pendulum effect to the drill stem and weight to the bit.

A short, heavy, cylindrical steel section with a rounded bottom and attached to the bottom of the casing string. It contains a check valve and functions similarly to the float collar but also serves as a guide shoe in the casing.

A short cylindrical device installed in the drill stem between the bottom-most drill collar and a downhole motor. Its purpose is to deflect the downhole motor off vertical to drill a directional hole. See drill stem.