| 摘要 |
An oilfield tubular string 10, 60, 60A comprising a plurality of elongate joints having one or both ends threaded. The joints may be connected by a coupling including a generally sleeve shaped coupling body having a tapered upstream thread profile and a tapered downstream thread profile for threaded engagement with a mating profile of a respective joint. The coupling body includes a low stress flex groove 30 having a selected box thread runout bevel angle, and all transitions in the flex groove between surfaces are radiused to greater than 0.100 inches to minimize stress risers. A pin-in-box connection between tubular joints includes mating tapered threads 72, engagement of end shoulder 74, 76, 78, and 80, and a low stress flex groove 82. The present invention allows the elongate joints to be used as both a casing string and a drill string, thereby saving significant time and expense. |
