Common Drill Pipe Connection

Drill pipe connections are crucial components in drilling operations, providing the link between drill pipes. Various types of connections are used in the oil and gas industry based on specific drilling requirements. Here are some common drill pipe connections.

REG (Regular Style Connection):

The regular style connection is utilized to join inner upset drill pipes, resulting in a configuration where the drill pipe diameter is smaller than the inner diameter of the thickened portion. The main application of the API-designed regular style connection is in bit connections. Due to the placement of the drill bit at the end of the drill string, the stress concentration phenomenon in the thread is not a significant concern. Consequently, API has retained all specifications for this connection type.

IF (Internal-flush Style Connection):

The internal-flush style connection is employed to connect externally upset (EUE) or inside and outside thickened drill pipes. This creates a drill pipe joint with an inner diameter equal to or approximately equal to the inner diameter of the thickened or outside pipe. The specifications for this type include a V-0.065 flat top and bottom triangular tooth design, with a width of 0.065 inches (1.651mm). Due to the potential stress concentration associated with this type, API has gradually phased it out.

FH (Full-hole Style Connection):

The full-hole style connection connects inside and outside thickened drill pipes, resulting in a drill pipe joint with an inner diameter equal to the thickened end diameter, both of which are smaller than the inner diameter of the pipe. Despite having fewer thread specifications, it offers three models named V-0.065, V-0.05, and V-0.040, making it widely used in kellys, drill pipes, drill collars, and drilling operations.

NC (Numbered Connection):

For drill pipes with a minimum yield strength of 75,000 PSI or greater (high-strength), the API recommends a numbered connection, or NC. NCs are designed to connect pins and boxes with matching thread designations, and they are largely interchangeable when grade codes match. The thread pitch and type compatibility are crucial factors for interchangeability. Numbered connections range from NC10 to NC77, featuring varying intervals with corresponding inner and outer diameters. Checking with the tool joint manufacturer is advisable to ensure compatibility of NC and thread types.