Exxon Production Research Company

James B Day

Mark C Moyer

Jeffrey Roberts Bailey

Anthony J Buonodono

Richard P McBride

Alan J Hirshberg

A threaded connection with improved fatigue-life useful for connecting adjacent sections of a pipe string subject to bending, tensile, and compressive stresses such as a drill collar string is disclosed. The connection comprises a pin member which is threadedly engageable with a corresponding box member. In the preferred embodiment, the inventive connection is designed to have bending strength ratio ('BSR') of about 3.20 or greater, and more preferably, in a range between about 3.20 and about 4.00. The preferred thread form of the connection is a V-type thread form having two flank angles of 30 degrees and a 0.038 inch root radius. Other design features may be used in combination with the threaded connection to further improve the connection's fatigue-life. Such design features include a tapered pin bore, an increased root radius for selected box threads, an internal box stress relief groove, a box bore stress relief groove, an extended pin relief groove, and modification of the API boreback box design to provide an increased number of threads having full threaded engagement.

Drill collar connections

Threaded pipe sections are connected to form a casing joint having proper sealing positioning at proper makeup torque. This improved connection includes a first pipe section having a standard API triangle mark at a predetermined position on its exterior surface for the proper axial engagement of the pin member with the coupling or box member. The box member is plated with a metal substantially comprising tin. A thread lubricant containing Teflon.TM. is applied to the threads of the pin and/or the threads of the box. The pin member and the box member are helically rotated together up to a minimum of an empirically predetermined torque range. While inexpensive, this improvement provides a simple method to determine visually on the rig floor, or at the pipe rack, whether the joint is properly made up to thereby provide effective gas sealing of the API buttress tapered threaded joint.

High gas sealibility makeup for API buttress connections

Threaded pipe sections are connected to form a tubular joint having proper sealing positioning at proper make-up torque. This improved connection includes a first pipe section having a registry mark of a prescribed width at a predetermined position on its exterior surface for the proper axial engagement of the pin member with the coupling or box member. This position is principally determined from finite element analysis. This position is the same for all pin members of a similar size, grade, weight and thread form and therefore can be applied with a template. The pin member and box member are continuously threaded together up to a minimum of an empirically predetermined torque range. This torque range is predetermined by a combination of finite element analysis and experimentation of representative joints for a certain type, size, weight and grade of pipe section. If required, the range is adjusted by empirically determined friction factors to account for different platings, surface treatment and lubricants. While inexpensive, this improvement provides a simple method to visually determine on the rig floor or at the pipe rack whether the joint is properly made up to thereby provide effective sealing of the API tapered threaded joint.

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New Orleans, LA, United States of America

James B Day