Couplings for standard A.P.I. tubings and casings

• US 5,263,748 A
• Filed: 09/30/1992
• Issued: 11/23/1993
• Est. Priority Date: 05/19/1982
• Status: Expired due to Term

• Current Assignee: Kenneth J. Carstensen
• Original Assignee: Kenneth J. Carstensen
• Inventors: Carstensen, Kenneth J.
• Primary Examiner(s): Arola, Dave W.
• Application Number:
  US07/954,683
• Time in Patent Office: 419 Days
• Field of Search: 285/333, 285/334, 285/355, 285/390, 285/369, 285/383
• US Class Current: 285/333
• CPC Class Codes: E21B 17/042 Threaded
• CPC Class Codes: E21B 17/08 Casing joints
• CPC Class Codes: E21B 19/16 Connecting or disconnecting pipe couplings or joints E21B19/20 takes precedence
• CPC Class Codes: F16L 15/003 with sealing rings
• CPC Class Codes: Y10T 29/49716 Converting
• CPC Class Codes: Y10T 29/49771 Quantitative measuring or gauging
• CPC Class Codes: Y10T 29/4987 Elastic joining of parts
• CPC Class Codes: Y10T 29/49881 of separate helix [e.g., screw thread]

Abstract

A pipe coupling system including a modified collar (12) into which a first pipe (40) and a second pipe (30) are inserted. In a first embodiment, a ring (22) resides within the collar which can serve as a torque shoulder or a metal to metal seal. In a second embodiment, a composite element (22'"'"') is formed of three concentric rings, a first ring (41) being composed of a Teflon® like material, a second ring (44) being composed of a Torlon® or Peek® like material, and a third ring (42) composed of a Teflon® like material. The adjoining surfaces (60,61) of the rings (41,42,44) form leakage paths to relieve accumulated pressure within the collar thread voids (51). A slip on gauge (52) is disclosed for prescreening pipe to insure that it is within the tolerances required for the present system. A bucking plug (8) is disclosed for insuring that the first pipe (40) is inserted within the collar (12) to the proper depth.

Claims

1. A threaded coupling for connecting adjacent sections of standard A.P.I. tubing or casing to upgrade the coupling for use under greater stress and pressure conditions than A.P.I. standards for use of the same tubing or casing comprising:

a pair of A.P.I. standards tubular products having thread tapers and diameters that are pre-screened to be within selected cumulative dimensional limits relative to nominal insertion in a collar;

a collar having a length within ±

0.010" of nominal and converging threads from each external end having precisely defined cumulative dimensional limits of approximately an order of magnitude less than the cumulative dimensional limits of the tubular products, the collar having a central threaded region with threads truncated at a predetermined internal diameter, the pair of tubular products being threaded into the collar to a spacing between the ends of about 0.750" to about 1.000"; and

a ring having an outer diameter mating with a press fit with the truncated threads in the central region of the collar, the ring having an inner diameter substantially flush with the inner diameter of the tubular products.

2. A coupling as set forth in claim 1 above, wherein the ring has an axial length of between 0.750" and 1.000" and is in contact with the inserted ends of both tubular products.

3. A coupling as set forth in claim 2 above, wherein the ring is axially segmented into two synthetic resin rings with an interposed rigid ring for use with internally coated tubular products.

4. A coupling as set forth in claim 2 above, wherein the ring is compressed by the ends of the inserted tubular products to a pre-loaded level that establishes a metal to metal seal that is retained under the operating load of a string of tubular products.

5. A coupling as set forth in claim 4 above, wherein the abutting surfaces between the ring and tubing or casing include at least one extreme end surface of reduced surface contact area to increase the surface pressure for the metal to metal seal.

6. A coupling as set forth in claim 1 above, wherein the ring of about 0.880" in axial length for 8" round or buttress thread.

7. A collar for coupling standard A.P.I. threaded tubular goods comprising:

a tubular element having an outer surface concentric with a central axis and an interior threaded region, the tubular element having end recesses of predetermined inner diameter and converging tapered threaded regions for mating with A.P.I. threads, the converging threaded regions having thread taper, location of pitch diameter, height and angle tolerances at least twice more precise than tolerances permitted by A.P.I. standards for like parameters, the converging threaded regions merging at a central region at which the threads are truncated so that their inner surfaces lie along a predetermined circumference.

8. A collar as set forth in claim 7 above, wherein four thread tops in the central region are truncated to provide a central inner diameter at a circumference that is less than the inner diameter at any other threads.

9. A collar as set forth in claim 8 above, wherein the taper is precise to ±

0.001 in/in and the pitch diameter location is precise to ±

0.025".

10. A ring structure for interposition between the nose ends of tubings or casings threaded into a collar comprising:

a pair of synthetic resin outer rings each having an inner circumference approximating that of the tubing or casing, and having an outer surface substantially mating with the nose end of the tubing or casing; and

a central ring of rigid material disposed between the outer rings and separate therefrom, the abutting, non-attached, surfaces between the outer rings and the center ring providing a pressure relief path for release of gas permeated at high differential pressure into the spaces between the ring structure and collar to relieve pressure differentials, the central ring having an inner circumference approximately that of the tubing or casing and the overall length of the ring structure being between about 0.750" and about 1.000".

11. A ring structure as set forth in claim 10 above, wherein the outer rings have slightly concave inner circumferences such as to be compressed into substantially linear surfaces flush with the inner surfaces of the tubing or casing when the tubings or casings are threaded into the collar, and wherein the overall length of the ring structure is about 0.880 inches.

12. A ring structure as set forth in claim 11 above, wherein the outer rings are of "Teflon®

" and the central ring is of "Torlon®

".

13. A coupling for oil and gas well tubing and casing of A.P.I. standard type, comprising:

a collar having a central partially threaded region having a predetermined inner diameter and including precisely placed and tapered threads relative to the external dimension of the collar; and

a pair of prescreened A.P.I. tubings or casings for mating with the collar from the opposite ends, a first tubing or casing being threaded into the collar to a preset depth from the mill end, the second tubing or casing being threaded into the field end to a gap of between 0.750" and 1.000" between the nose ends of the tubings or casings, the thread dimensions, tapers and thread forms of the pair of tubings being determined by prescreening such that dimensional makeup alone assures adequate bearing pressure despite variations in the tubing or casing, and wherein the collar is configured for receiving a ring structure inserting into the collar between the tubings or casing in the central region prior to makeup.

14. A coupling as set forth in claim 13 above, including in addition a ring of axial length between 0.750" and 1.000" in the central region of the collar, in contact with the nose ends of both the tubings or casings.

15. A coupling as set forth in claim 14 above, wherein the ring has a length of about 0.880" and the dimensions of the collar and prescreened tubing or casing provide a preload compressive pressure in excess of three times the anticipated pressure on the tubing or casing when the filed end installed tubing or casing is threaded in to a predetermined depth relative to the field end of the collar, whereby to establish metal-to-metal seals maintaining their integrity despite axial loading from downhole tubing or casing mass.

16. A coupling as set forth in claim 14 above, wherein the nose ends of the tubings or casings have reduced surface areas in contact with the ring to provide adequate preloading pressure for a reasonable tightening torque.

17. A coupling as set forth in claim 13 above, wherein the ring defines spaced apart torque shoulders for equal engagement against the nose ends of the tubings or casings, and fits with a press fit in the central region of the collar and has an inner circumference substantially flush with the inner circumference of the tubing or casing.

18. A threaded coupling for connecting adjacent sections of standard A.P.I. tubing or casing to upgrade the coupling for use under greater stress and pressure conditions than A.P.I. standards for use of the same tubing or casing comprising:

a pair of A.P.I. standard tubular products having thread tapers and diameters that are prescreened to be within selected cumulative dimensional limits relative to nominal insertion in a collar;

a collar having a length within ±

0.010" of nominal and converging threads from each external end having precisely defined cumulative dimensional limits of approximately an order of magnitude less than the cumulative dimensional limits of the tubular products, the collar having a central threaded region with threads truncated at a predetermined internal diameter, the pair of tubular products being threaded into the collar to a spacing between the ends of about 0.750" to about 1.000".

19. A threaded coupling as set forth in claim 18 above, wherein the collar is configured for receiving a ring, the ring having an outer diameter mating with a press fit with the truncated threads in the central region of the collar, the ring having an inner diameter substantially flush with the inner diameter of the tubular products.

20. A coupling as set forth in claim 18 above, wherein the coupling comprises an open J-area upon removing the ring.

21. A coupling as set forth in claim 19 above, wherein the coupling comprises a smooth bore coupling.

22. A coupling as set forth in claim 21 above, wherein the coupling comprises a smooth bore coupling with metal to metal seals between the nose ends of the tubular products and the sides of the ring.

23. A coupling as set forth in claim 21 above wherein the coupling comprises a smooth bore for internally coated pipe.

24. A threaded coupling as set forth in claim 18 above, further comprising a ring, wherein the collar is configured for receiving the ring, and wherein the ring has an outer diameter mating with a press fit with the truncated threads in the central region of the collar, and wherein the ring has an inner diameter substantially flush with the inner diameter of the tubular products, wherein upon insertion of the ring the coupling comprises a smooth bore coupling, and wherein upon removal of the ring, the coupling comprises an open J-area.

25. A coupling as set forth in claim 24 above, wherein the coupling comprises a smooth bore coupling with metal to metal seals between the nose ends of the tubular products and the sides of the ring.

26. A coupling as set forth in claim 24 above wherein the coupling comprises a smooth bore for internally coated pipe.