Exxon Production Research Company

Richard P McBride

Jeffrey Roberts Bailey

Mark C Moyer

James B Day

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.

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Houston, TX, United States of America

Richard P McBride