Pipe joints or couplings – Particular interface – Tapered
Patent
1992-04-28
1994-07-05
Brown, David H.
Pipe joints or couplings
Particular interface
Tapered
285333, F16L 2500
Patent
active
H00013293
ABSTRACT:
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.
REFERENCES:
patent: 2745685 (1956-05-01), Moore
patent: 3100657 (1963-08-01), Pistole et al.
patent: 4076436 (1978-02-01), Slator et al.
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patent: 4549754 (1985-10-01), Saunders et al.
patent: 4892337 (1990-01-01), Gunderson et al.
patent: 5169183 (1992-12-01), Hallez
"Don't Ruin These New Drill Collars!", H. M. Rollins, Oil & Gas Journal, Mar. 14, 1966, pp. 81-100.
"Deep Drilling Practices in Mississippi", W. L. Kirk, Journal of Petroleum Technology, Jun. 1972, pp. 633-642.
"Tool-Joint Thread Redesign Cuts Stress, Increases Fatigue Life", F. J. Carlin and D. Saunders, Oil & Gas Journal, Jul. 22, 1985, pp. 75-78.
"A Contractor's History of Drillstring Failures in the Anadarko Basin", S. D. Hampton, SPE Conference Paper, New Orleans Conference, Mar. 15-18, 1987, pp. 177-189.
"Guides for Evaluating Drill Collar OD, ID, and Connection Combinations and Oil Field Thread Form", Drilco Drilling Assembly Handbook, Smith International, Inc., 1988, pp. 77-95 and 96-99.
"Larger Drillstrings Could Improve Contractor Profits", R. L. Dudman and R. A. Dudman, World Oil, Mar. 1990, pp. 83-91.
"Properties of Drill Collars, Section 3", Recommended Practice for Drill Stem Design and Operating Limits, API Recommended Practice 7G, American Petroleum Institute, Aug. 1, 1990, pp. 33-43.
"Tool Joints, Section 4; Drill Collars, Section 6; and Rotary Shouldered Connections, Section 9", Specification for Rotary Drilling Equipment, API Specification 7, American Petroleum Institute, Aug. 1, 1990, pp. 11-15, 18-23, 27-29, and 71.
Smith International, Inc. letter by D. W. Brinegar, Aug. 30, 1991 and referenced Drilco Tool Report excerpts, circa 1953, pp. 1-4 and 53.
Bailey Jeffrey R.
Day James B.
McBride Richard P.
Moyer Mark C.
Bell Keith A.
Brown David H.
Exxon Production Research Company
Van Tassel Kurt D.
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