| 摘要 |
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 precison 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 thread 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 strees conditions. Makeup on the right 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. |
