초록 ▼

Precision makeup at high speed of the most used forms of pipe and casing for production wells is assured by a novel coupling system. A pipe collar is provided with an internal precision makeup ring whose length along the pipe axis assures precise positioning and engagement. When the nose of the pipe

Precision makeup at high speed of the most used forms of pipe and casing for production wells is assured by a novel coupling system. A pipe collar is provided with an internal precision makeup ring whose length along the pipe axis assures precise positioning and engagement. When the nose of the pipe is engaged with metal-to-metal contact against a reference shoulder on the precision ring a side surface on the nose end of the pipe engages a center seal ring disposed in the side wall of the collar between the reference shoulder and the threaded portion. This seal constitutes an effective barrier against the leakage of high internal pressures into the thread engagement region. End seals are mounted in grooves in the end recess portions of the collar, outside the threaded engagement region, to provide seals against external pressure, which can also vent internal pressures that are in excess of a predetermined threshold. With this arrangement, a modified standard collar or a manufactured collar can be placed on a pipe or casing off the drill rig floor, with the axial length of the precision ring being selected to assure makeup tightness adjusted to particular axial stress conditions. Makeup on the rig floor requires only stabbing of the next pipe section into the collar and engagement until metal-to-metal contact is achieved and seals are concurrently established. Pipes and collars can readily be prescreened to eliminate a minor proportion of elements whose thread tapers vary more than is permissible for the given conditions.

대표청구항 ▼

A coupling collar for A. P. I. standard round or buttress thread tubing or casing having a nose surface at the end thereof, a side bevel adjacent the nose and having a specified angle relative to the longitudinal axis of the tubing or casing, a threaded region of pitch and thread depth in accordance

A coupling collar for A. P. I. standard round or buttress thread tubing or casing having a nose surface at the end thereof, a side bevel adjacent the nose and having a specified angle relative to the longitudinal axis of the tubing or casing, a threaded region of pitch and thread depth in accordance with specified tolerances between the bevel and a last scratch mark, the threads diminishing to zero in the bevel and last scratch mark regions, the collar including threaded portions tapering oppositely from a central region with specified taper angles, the collar having tolerances closer than the tubing or casing tolerances and terminating in end recess portions adjacent the threaded portions and within which the ends of tubings or casings are to be matingly received, the end recess portions having inner diameters larger than the outer diameters of fully inserted tubings or casings, the collar comprising: a central metal reference ring member coupled to the collar and having an inner diameter corresponding to the inner diameter of the tubings or casings and oppositely facing reference shoulders lying in planes perpendicular to the central axis of the collar and spaced apart by a predetermined distance related to an acceptable range of taper and size variations for the unmodified A. P. I. tubing or casing such that engagement of the nose of an unmodified A. P. I. tubing or casing against a reference shoulder of the ring member is determinative of the degree of thread engagement desired for the tubings or casings relative to the collar; means defining central grooves in the collar, each disposed between a different one of the reference shoulders and the adjacent threaded portion and having a depth no greater than the depth of the threads; a pair of central seal means, each positioned in a different central groove and proportioned to be engaged and compressed by the side bevel of the nose of the A. P. I. tubing or casing and to extend into the start of the threads on the side bevel when the nose of the tubing or casing is in contact with the ring member to provide a seal against internal pressures that cannot be displaced by such internal pressures; means defining end grooves in each of the end recess portions outside the threaded portions of the collar; and a pair of end seals each disposed in a different one of the end grooves, the end seals each engaging the adjacent received A. P. I. tubing or casing in the region of the last scratch mark thereof and being dimensioned to be compressed into the inital threads in the last scratch mark region when the nose of the tubing or casing is in contact with the ring member to provide a seal against external pressures, the end seals being configured to deform outwardly into the end recess portion in response to internal pressures and thereafter return to position to provide sealing, whereby the collar is both adequately mechanically engaged in the threaded load bearing region and the threaded region is sealed at both ends such that the collar can matingly receive unmodified A. P. I. tubings or casings without the presence of weakened regions due to the introduction of mechanical stress risers in the collar and provides sealing of the threaded portions under varying conditions of operation.