Marubeni Tubulars, Inc.

Ultra Premium Oilfield Services, Ltd.

Nkk Corporation

Edward O Banker

Erich F Klementich

Fu J Hou

Teruo Suzuki

Ryan Broussard

Jeffrey K Bouche

A tubular connection is formed by a box member and a pin member, each of which has a tapered constant pitch thread. A profile defined by the thread of at least one of the pin member and the box member results in a pitch line that is a stepped pitch line. The stepped pitch line configuration may produce a wide radial band of substantive contact between the stab flanks of the pin member and box member upon full make-up of the connection.

Tubular connection and associated threadform

A tubular connection includes a pin member and a box member. The pin member has a first thread structure and a helical torque shoulder spaced axially along the pin member from the first thread structure. The box member has a second thread structure and a second helical torque shoulder spaced axially along the box member from the second thread structure. The first thread structure and the second thread structure are sized and located to control a stab position of the tubular connection, and in the stab position the first helical torque shoulder does not engage or axially overlap with the second helical torque shoulder. A method of joining tubular members utilizing a helical torque shoulder is also provided.

Tubular connection with helically extending torque shoulder

The tubular connection includes a pin member having external tapered threads extending from a pin nose to a pin base and a box member having internal tapered threads extending from a box base to a box nose. The tapered threads are square or near square threads having stab and load flanks with accommodating grooves. The stab flanks have corner chamfers which engage upon stabbing the pin member into the box member. The comer chamfers increase the clearances between the threads and grooves and guide the crests to the root openings upon relative rotation of the pin and box members. The stab flanks may have an increased thread width at the thread pitch line forming cam flanks which cam the threads into the grooves. The crests and roots of the threads interferingly engage. The pin nose and box base engage to form a metal-to-metal seal and a primary torque shoulder which during power tight make-up causes the load to shift from the stab flanks to the load flanks. The pin nose and box base lock up such that upon the application of further torque, the threads lock up from the pin nose back to the pin base thereby transferring substantially all of the remaining applied torque to the threads whereby the seal becomes insulated from any additional make up torque.

Tubular connection

The metal-to-metal sealing system includes a first seal configuration on one member of the connection and a second seal configuration on the other member. Each seal configuration includes an annular groove and an adjacent annular tooth. The annular groove and annular tooth form three frustoconical surfaces with the groove having an annular undercut surface and the annular tooth having an annular shoulder surface. A seal cylindrical surface and a pre-ramp cylindrical surface extend from the mouth of the groove and a frustoconical ramp forms the transition surface between the seal and pre-ramp cylindrical surfaces. Further, at the base of the outer side of the annular tooth, there extends a cylindrical surface along the main body of the member. Upon makeup of the connection, the ramps and seal cylindrical surfaces guide and align the seal configurations. Initially the center frustoconical surfaces interferingly engage. Upon further tightening of the connection, the teeth are funneled into the grooves with the teeth being wider than the width of the grooves causing the other frustoconical surfaces to interferingly engage. Upon final power tightening of the connection, the annular shoulder surface and undercut surfaces engage whereby upon final makeup, up to seven seals are formed. Six of the sealing surfaces on each seal configuration are cut by a single plunge cut of a carbide tool insert.

Method for producing sealing surfaces on a tubular member

Sealing system

The present invention pertains to an improvement in buttress-threaded tubular connections. In particular, the connection is improved by controlling the tubular member thread pitch diameter tolerance to .+-.0.0015 inch, to provide a thread bearing contact pressure which is relatively constant over the entire length of the connection. In addition, the improved connection provides a reduction in hoop stress of about 20% over known buttress-threaded tubing connections. The present invention typically includes the use of variable make-up in combination with the control of the tubular member thread pitch diameter tolerance.

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Houston, TX, United States of America

Edward O Banker