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Title:
HIGH TORQUE THREADED PIPE CONNECTION
Document Type and Number:
WIPO Patent Application WO/2013/101852
Kind Code:
A1
Abstract:
Unique features are disclosed for use in a Threaded Pipe Connection that increase the torque and bend strength.

Inventors:
WATTS, John D. (8301 Gutherie Dr, Austin, Texas, 78750, US)
Application Number:
US2012/071687
Publication Date:
July 04, 2013
Filing Date:
December 26, 2012
Export Citation:
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Assignee:
WATTS, John D. (8301 Gutherie Dr, Austin, Texas, 78750, US)
International Classes:
F16L25/00
Foreign References:
US20100032166A1
US7510219B2
US20030160446A1
US7484776B2
US20030038476A1
US20110008101A1
US20100237612A1
US20060152000A1
US20030168858A1
Download PDF:
Claims:
1. A threaded pipe coupling (21) having tapered coupling threads (26,2?) formed within opposite ends of the coupling to mate with pin threads (40, 41 ), the coupiiii g having mid-length threads (20) formed with ID (22), and a ring (1 ) having a OD (2), a ring ID (3) and ends (4,5) comprising:

The ring OD being precisely dimensioned to press-fit into the mid-length thread ID to effect a predetermined hoop stress within the ring.

2. A metal ring (J) having a precisely dimensioned OD (2) and a predetermined length (6), for mounting mid-length within a pipe coupling (21 ), having mid-length threads (20), the threads having an ID (22) comprising:

The OD being dimensioned for a press-fit within the pipe coupling, the mid-length threads with a precision ID being dimensioned to receive the ring and effect a predetermined

compressive hoop stress within the ring.

3. The pipe coupling of claim L further comprising

The box. threads being formed to mate with pin threads formed on pipe commercially available.

4. The pipe coupl ing of claim 1 , further comprising:

The box threads being formed to mate with special size pin threads,

5. The pipe coupling of claim 1 , further comprising:

The thread ID at mid-length being formed by truncation of the mid-length threads.

6. The pipe coupling of claim 1 , having a predetermined thread length (46) and the ring having a length (6), further comprising:

The ring having a predetermined length such that when the coupling and ring are properly assembled with the pin threads, predetermined bi -axial stresses are developed within the ring and the pin ends.

7. The pipe coupling of claim 6 wherein the ring ends are coated with a malleable material (52), further comprising :

The malleable material being softer than the ring material and suitable to withstand the intended service; the coating material being malleable enough conform with and seal against the pin end surfaces upon assembly of the coupling with the pin ends upon assembly of the coupling with the pin threads.

8. The ring of claim 2, having ring ends (55,56) formed with circular ridges (64), former comprising;

Each ring end being formed with one or more circular ridges projecting axially and around the ring such thai the ridges will indent and seal against the pin ends as the ring and pins are assembled with the coupling.

9. A pipe connection (99) including a coupling (100) formed with box threads (101., 102) and mating pin threads (103,104) formed on pins (1 iO, ! 1 1) having pin noses (1 12, 1 13), comprising:

Thai upon assembly of the pins with the coupling, the pin noses have predetermined hoop stresses within and are forced against each other with sufficient force to generate a

predetermined biaxial stress within the pin ends sufficient to delay yielding of the noses to a predetermined stress value.

10. A pin dimensioned in accord with claim 9.

1.1. A coupling dimensioned in accord with claim 9.

12. The connection of claim 9, further comprising:

The predetermined biaxial stress being sufficient to increase the assembly torque that the connection can withstand without yieiding of the pin ends, to a predetermined torque value.

13. The connection of claim 9, further comprising:

The predetermined biaxial stress being sufficient to increase the axial strength thai the connectio can withstand without yi eiding of the pin ends, to a predetermined value.

14. The pipe connection of claim 9, having a gasket (1 1.4), further comprising:

The gasket being positioned between the pin ends to assist the sealing of fluids there between.

15. The pipe connection of claim 14, further comprising:

The gasket being too thin to be extruded, from between the pi ends.

16. A high strength threaded pipe coupling (138) having a box (149), a pin (i41 ),having a pin nose (148) and a pin end (140), a shoulder (142) and a coupling bore (146) formed within the box, the shoulder positioned to abut the pin end upon makeup of the connection, comprising:

The coupling bore formed within the box dimensioned and positioned to radially compress the pin nose sufficiently upon makeup of the connection, to effect a predeterm ined hoop stress within the pin end; the hoop stress in combination with the axial stress being sufficient to created a biaxial stress in the pin end thai will enable the pin end to withstand a higher load than a pin end with no hoop stress could withstand, and the box being formed of a higher strength material than the pin is formed of

17. A pipe coupling (21 ) having threads (26,27) for mating with pin threads (40,41 ) formed on pins (38,39), the pins having pi noses (44,45), comprising;

The box and pin threads being dimensioned for radial interference upon assembly together to effect hoop stresses in the pin ends upon assembly that in combination with the forces on the pin ends, are sufficient to effect predetermined biaxial stresses in the pin ends.

18. The pipe coupling of claim 17 having a length of mid-length threads (20) positioned betwee the pin ends (53,54) as assembled, the mid-length threads having ID (22), further comprising:

The mid-length threads being truncated to form a precision ID that is interrupted between the truncated threads; ring having an OD dimensioned to press into the ID and effect a predetermined compressive hoop stress within the ring, so thai upon assembly, the pin ends are loaded against the ring ends sufficiently, to effect predetermined biaxial stresses within the ring and within the pin ends.

19. A threaded pipe coupling (21) having tapered coupling threads (26,27) formed within opposite ends of the coupling to mate with pin threads (40, 41 ), the coupling having mid-length threads (20) formed with ID (22), and a ring (1 ) having a OD (2), a ring ID (3) and ends (4,5); a metal ring (1) having a precisely dimensioned OD (2) and a predetermined length (6). for mounting a mid-length within a pipe coupling (21 ), having mid-length threads (20), the threads having an ID (22); a pipe connection (99) including a coupling ( 100) formed with box threads (101 ,102) arid mating pin threads ( 103,104) formed on pins (1 10, 11 1) having pin noses

(1 12,1 13); a high strength threaded pipe coupling (138) having a box (149), a pin (14I),having a pin nose (148) and a pin end (140), a shoulder (142) and a coupling bore (146) formed within the box, the shoulder positioned to abut the pin end upon makeup of the connection; a pipe coupling (21 ) having threads (26,27) for mating with pin threads (40, 1) formed on pins (38,39), the pins having pin noses (44,45), further comprising:

The ring OD being precisely dimensioned to press-fit into the mid-length thread ID to effect a predetermined hoop stress within the ring; the OD being dimensioned for a press- fit within the pipe coupling, the mid-length threads with a precision ID being dimensioned to receive the ring and effect a predetermined compressive hoop stress within the ring; that upon assembly of the pins with the coupling, the pin noses have predetermined hoop stresses within and are forced against each other with sufficient force to generate a predetermined biaxial stress within the pin ends sufficient to delay yielding of the noses to a predetermined stress value; the compression ID formed within the box dimensioned and positioned to radially compress the pin nose sufficiently upon makeup of the connection, to effect a predetermined hoop stress within the pin end; the hoo stress in combination with the axial stress being sufficient to created a biaxial stress in the pin end that will enable the pin end to withstand a higher load than a pin end with no hoop stress could withstand, and the box being formed of a higher strength material than the pin is formed of; the box and pin threads being dimensioned for radial interference upon assembly together to effect hoop stresses in the pin ends upon assembly that in combination with the forces on the pin ends, are sufficient to effect predetermined biaxial stresses in the pin ends.

20. The ring of claim 1,2,6,7,8,18 or 19 wherein the ring has pin threads that mesh with the box threads, such that the ring is screwed into the box threads to effect the predetermined hoop stress.

Description:
HIGH TORQUE THRE ADED COUPLING

Priority is claimed on US Provisional Application 61/580,593.

FIELD OF THE INVENTION; The present invention applies to any threaded connection, but the terms used herein are as applied to pipe couplings for use in oil and gas wells.

BACKGROUND ART; Pipe couplings have a tapered internal thread (a box) in each end for mating wit an externally threaded pipe end fa pin) to form strings of pipe ranging from 50 feet long as in a home water well, to more than 5 miles long to lower into oil and gas wells to kee the holes open with large diameter pipe known as casing, and also to convey produced fluids to the surface with small diameter pipe known as tubing. Heretofore, there has been little need to rotate a casing string with more torque than its assembly torque while being lowered into the hole, but lateral wells are now being drilled into relatively thin shale formations to produce gas and oil, said to be a 200 years supply for the United States that require high torques. Rotation of the pipe string required to get it through the bend from the vertical section of the hole to the lateral section, does require more than assembly torque plus an axial push that compounds the axial stress on the inside of the bent pipe, so there is now a need to increase the axial

compressive force thai a casing connection can withstand without leakage or damage. The vast majority of casing ends have no increase of thickness, to remain cost-effec tive, which leav es no shoulder to abut the end of a coupling for added torque, but rings have been inserted within couplings between the ends of the pipe joints to contact pin ends and increase the torque that the connection can withstand, but only up to the axial yield strength of the ring or pin. end, whichever is least. The radial space available for the ring is typically between the pin end root diameter and the pipe ID, which limits its annular end area, and the torque increase it can add to the coupling. Such rings are disclosed in Huston Patent US 7,510,2.19 B2 having a torque ring in a coupling between pin ends but makes no mention of a biaxial stress, and in Fig. 3, it shows and claim clearance between the ring ends and the inner diameter of the coupling, which precludes the possibility of creating a biaxial stress there. Slack patent US 2010/0032166 A ! discloses various ways to retain a "shoulder ring" within a coupling but makes no mention of a biaxial Definitions of some terms used herein are: OD=outentiost diameter; ID means innermost diameter; in - a short tabular member; Bend :::: a curve in. a well's bore defined by a radius of curvature.

BRIEF DESCRIPTION OF THE DRAWINGS:

FIG 1 depicts a fragmentary quarter-section of a casing coupling having features the present invention.

FIG 2 is an enlarged fragmentary view of the ring in FIG L

FIG 3 depicts another embodiment of the invention.

FIG 4 is a fragmentary view of an alternate pin end.

DISCLOSURE OF THE INVENTION: Features are disclosed that substantially increase the torque and axial compressive load that a pipe connection can withstand in service, and also improve the ability of the connection to seal fluids within. The main feature of the invention is to radially compress the ring and end of the pin to effect compressive hoop stresses in either or both, so that when the ends abut upon makeup, they will be compressed both tangential iy and axially to create biaxial stresses in them, which enables the connection to withstand much higher compressive loads without yielding, than it could without the biaxial stress. Such, a higher end load enables the connection to withstand: (! ) a higher torque; (2) a higher axial load; and (3) a higher angle of bend without damage or leakage. How to create the proper hoop stress in the ring and pin ends that is necessary for the connection to withstand such higher loads and also improve in sealing ability is taught: by dimensioning the length of the ring to limit the pin lengt that enters the box of an existing standard coupling or alternately b providing a coupli ng with specially dimensioned threads that will compress the pin threads and ring ends radially to effect the required biaxial stresses. The "J-Jength" of the box thread within a API Buttress coupling is the length between the hand-tight and power tight positions of the pin end, which together with radial interference, determines the hoop-stress in the pin upon assembly. The API J- length radial interference and thread taper is the same for a range of casing sizes, so the thread interference per inch of diameter will be different and therefore, the pin hoop stress will be different for each pipe size, so a specific biaxial stress cannot be effected in the pin ends as required to prevent their yielding when forced against a torque ring. Therefore, the present invention also teaches the dimensioning of the coupling thread diameter and/ or the pin thread di meter to effect a compressive hoop stress in the pin end upon assembly, thai will act with the end load on the pin to effect a predetermined biaxial stress in the pin end that will prevent its yielding upon appl ication of the design end-load.

Also taught is a cost effective way to retain a ring within a coupling that prevents its mishandling in the field. The ring may be pre-mstalled within the coupling by first pushing the ring toward mtd-section as far as it can be pushed by hand, and then screwin a pin into the box which press- fits the ring into proper mid-section position as the pin shoulder abuts the box face. Other features may assist installation of a casing string within a lateral well such as: the ring may be formed with external threads that interfere and mate with the box threads as it is screwed to the coupling whic creates the compressive hoop stress.

DETAILED DESCRIPTION OF THE IN VENTION: As depicted in FIG I, the present invention teaches the press-fit of a ring (1 ), having a precisely dimensioned outer diameter (2), an inner diameter (3) and ends (4, 5), the ring being positioned into mid-length threads (20) of predetermined length (6) within a coupling (21), such that the ring is compressed radially to have a predetermined compressive hoop stress which: (A) Retains the ring in proper position at raid- length within the coupling, and (B) increases the force that the ends of the ring can withstand well above one axis yield stress when pins (38,39) are assembled with the coupling, which in turn, (C) increases the axially compression and torque capacity of the assembly. Space occupied by the mid-length threads is commonly known as the ll J" space within a coupling that has imperfect threads, to allow for pu!lout of threading tools. To compress the ring of the present i vention, the crests (28) of the threads in the i section are bored to an ID (22) which provides more than enough contact area with the ring outer diameter to develop the predetermined hoop stress, without yielding of the threads radially.

As shown in FIG. I , the diameters (24, 25) of the coupling threads (26, 27) of predetermined length (46) axe dimensioned to mate with pin threads (40, 41) to radially compress the pin nose (44, 45) on the pipe joints (42, 43) sufficiently to build compressive hoop stresses i the pin nose to effect results A, B and C as described above, regarding the ring. Thus, upon assembly of the pins with the coupling, abutment of both pin ends against the ring will add torque to withstand higher axial loads and develop much higher torques against the ring with a like torque between the box and pin thread flanks, because both pin ends and the ring ends are then hiaxially stressed such that they do not yield. The ability to withstand greater axial loads also increases the connections compressive strength, enabling the connection to survive being pushed and pulled around bends having smaller radii of curvature than conventional wells have.

Pipe connection (99) embodiments in FIG 3 of the present invention, to be used with existing pipe joints previously threaded by others, may bore the mid-length threads of thai existing coupling to receive a ring disclosed herein, but if a special coupling (100) formed with box threads (101, 102) to mate with pin threads (103,104) on the pins (1 10,1 1 1 ) having pin noses (.1 12, 1 13), then the mid-length threads (usually one inc long) may he replaced with, a very short width (109) tool pullout groove (105) such that the pin ends (10? J 08) will contact each other when power tight, the pullout groove width being short enough such that the predetermined hoop stress is still effected in both pin ends which creates the biaxial stresses described above. The groove root is best formed on the same cone as the box thread root so the pin ends will be compressed the same as if by the thread, to prevent shear strain outwardly that would reduce the biaxial stress in the pin ends which in turn, would reduce the bearing strength of the pin ends. Connections that butt pin ends, but do not radially compress the pin ends, cannot generate biaxial stresses to delay compressive failure of the pin ends as taught by the present invention.

By way of .illustration only, and not to be construed as limiting in any way, an example of the increased bearing capacities of the several ring ends and the pin ends disclosed herein, may be as follows: Biaxial shear failure of a material occurs when the maximum principal shear stress is exceeded, in accord with the formula: Sp= (Sa-Sh)/2 rearranged as follows: Sa- 2*Sp Sh, where Sp ::: Principle shear stress in the material; Sa ::: axial bearing stress on end of the ring; Sh :::

compressive hoop stress Within the ring. If pipe and ring materials are API PI 10, then

Y™110,000 psi; Ultimate tensile strength- 125,000 psi; Max Sp ::: 2/3*I : 83,333 psi; and we will set Sh- «.8*Y - -.8* 1 10,000- -88.000 to allow reserve hoop strength in tire ring to withstand later applied externa! fluid pressure on the pipe. Solving the equation for the

allowable compression stress on end of th ring: Then Sa :::: 2*-83,333 (-88,000) :: - -256,666 psi which is more than twice Y, which is possible only because both the ring-ends and pin-ends become bi-axially stressed upon assembly of the connection. The axial end-load resulting from that compressive stress on the pin-end = Sa*(area of the ring end) which will also be applied by the pin load flanks to the box load flanks, so the torque increase ~ 2* end load*coefftcient of friction *(mean ring diameter/2)/ 12 ~ tV!bs.

It is well known that API SB threads, both SRound and Buttress, loosen and leak in service as explained in my US Patent 5,427,418, so the present inventio also provides features to effect a more reliable seal for any coupled connection against fluid pressures acting within or around the pipe, as depicted in FIG 2 herein that may be used with the connections above. The ring (50)

3 may be plated or coated with a malleable coating material (52) that is thick enough to flow and conform to norma! pin-end (53,54) in sealing contact, but not thick enough to be extruded from between the pin-ends and/or the ring-ends (55, 56). To extrude excessiveiy, the material must flow radially between the pin-end and the ring-end against the forces of friction (58, 59) on the pin ends and also against shear forces (60, 61) within the coating. Any coating material, whether metallic or plastic, that will not extrude excessively and will withstand the environmental factors such as chemical, thermal, stress and pressure of a given application, maybe used for seaiing. An. alternate or supplementary aid to seaiing may be the formation of one or more circular ridges portion (64) as shown in FIG 2, around the ring end or around the pin ends, that will deform to conform and seal with the other mating surface prior to contact of the remainder of the end surfaces that effect the biaxial stresses described above, A third alieraate sealing means depicted in F IG 3, is to position a ram gasket ( 1 14) of material, such as Teflon between the ring and pin ends or between pin ends that act directly against each other when assembled with a coupling that both effects a predetermined hoop stress in the pin ends when they contact each other.

FIG 4 depicts a shoulder (1 2) having ID (139) formed in a coupling ( 1 8), made of a higher strength materia! that the pipe, the shoulder positioned to butt pin end ( 140), a coupling bore (146) dimensioned to radially compress pin nose (148) on a pin (141) sufficiently to develop a predetermined biaxial stress in the pin nose, which together with the higher shoulder strength delays yielding which increases the connection, strength as described above.