Double shoulder threaded connector for well pipe having removable insert

Abstract

A tool joint for a pipe string, comprises a box end having a female threaded section proximate a longitudinal end of a pipe segment. A threaded section is formed on an interior wall of the pipe segment proximate a base of the female threaded section. The threaded section has formed therein at least one locking bore for receiving a locking pin. The at least one receiving bore is oval shaped and elongated in a longitudinal direction of the pipe segment. A shoulder sleeve has on its exterior surface threads for engaging the threaded section, and at least one pin bore through a wall of the shoulder sleeve. At least one locking pin is passed through the pin bore to engage the at least one locking bore when the at least one pin bore is rotationally and longitudinally aligned with the at least one locking bore.

Description

DOUBLE SHOULDER THREADED CONNECTOR FOR WELL PIPEHAVING REMOVABLE INSERTBackground

[0001] This disclosure relates to the field of threaded connections used in pipe such as drill pipe. More particularly, the disclosure relates to so-called “double shoulder” threaded connections.

[0002] Subsurface wells such as for oil and gas are drilled with a rotary drill bit rotated by a string of drill pipe and other drilling tools connected within the string of drill pipe. The drill pipe string is made-up of individual segments or “joints”, each about 30 feet (10 m) in length. The segments are secured to each other end to end by a tool joint containing a threaded connection, called a rotary shoulder connection. The tool joints and its connections must withstand the normal torque encountered during drilling, and also provide sealing to prevent drilling fluid being pumped down the drill pipe from leaking out the joints. Leakage out the tool joints causes wear due to the abrasiveness of the drilling fluid, which would lead to early failure.

[0003] The rotary shoulder connection is made-up of a pin (male) end on one pipe segment and a box (female) end on an adjacent tool joint segment. The pin end has external threads and an external annular make-up shoulder. The box end has internal threads and a rim or face that makes up against the make-up shoulder. In conventional drill pipe, there is no internal shoulder in the box end for contact by the nose or face of the pin. When the tool joint ends are connected (made-up”) at the surface, normally they will be made-up to a torque that exerts a pressure that is about one-half the yield strength between the box face and pin make-up shoulder.

[0004] Should additional torque be encountered while drilling, such as due to the bit or pipe becoming stuck, it is possible for the yield strength of the pin and box to be exceeded. Consequently, it is very important to have tool j oints with high torque withstanding abilities, preferably in excess of the drill pipe itself. To address theforegoing torque requirements, various forms of “double shoulder” tool joints have been developed. See, for example, U.S. Pat. No. 4,548,431 issued to Hall et al. and U.S. Pat. No. 6,030,004 issued to Schock et al.

[0005] A limitation to using double shoulder tool joints is that the internal diameter of the pipe segments may be reduced, as contrasted with single shoulder tool joints on the same diameter and wall thickness pipe. FIG. 1 illustrates the geometry of the box end of a double shoulder tool joint 10, wherein the outer shoulder is shown at 18, the inner shoulder is shown at 16, the thread section is shown at 20, the outer tool joint (and pipe) wall is shown at 12 and the inner pipe wall is shown at 14. It may be observed that the presence of the inner shoulder 16 provides the pipe segment with an inner diameter DI that is considerably less than the inner diameter of a comparable external diameter pipe segment single shoulder tool joint, shown at 24 in FIG. 2, wherein the internal diameter D2 is larger than the corresponding diameter DI of the double shoulder tool joint 10 for a same pipe diameter and outer shoulder 22 diameter as the double shoulder tool joint 10 in FIG. 1.

[0006] Certain types of downhole tools, for example and without limitation, measurement while drilling tools, valves, motors and the like may be located within the inner bore of a rotary shoulder connection. Thus, the tool joint 10 shown in FIG. 1 may restrict the diameter of downhole tools that can fit within the center bore 11 of the pipe segment, which diameter is limited by the minimum tool joint inner diameter DI. It is desirable to maintain the inner bore of the drill pipe string as large as possible for use with certain drilling tools. Therefore, there exists a need for a double shoulder tool joint that can be fitted to or formed with a drill pipe segment having larger internal diameter and access by such drilling tools to the larger internal diameter.Summary

[0007] One aspect of the present disclosure is a rotary shoulder connection for a pipe string.A tool joint according to this aspect comprises a box end having a female threaded section disposed proximate a longitudinal end of a pipe segment. A threaded section is formed on an interior wall of the pipe segment proximate a base of the female threaded section. The threaded section has formed therein at least one locking bore for receiving a locking pin.The at least one receiving bore is oval shaped and elongated in a longitudinal direction of the pipe segment. A shoulder sleeve has on its exterior surface threads for engaging the threaded section, and at least one pin bore through a wall of the shoulder sleeve. At least one locking pin is passed through the pin bore to engage the at least one locking bore when the at least one pin bore is rotationally and longitudinally aligned with the at least one locking bore.

[0008] Some embodiments further comprise a locking ring to retain the at least one locking pin in the at least one pin bore.

[0009] Some embodiments further comprise a plurality of circumferentially spaced apart pin bores in the shoulder sleeve and a plurality of corresponding circumferentially spaced apart locking bores in the threaded section.

[0010] In some embodiments, a pitch of the threaded section and the threads on the shoulder sleeve, and a number of and circumferential spacing of the pin bores and the locking bores chosen to enable axially locating the shoulder sleeve in the box end to a predetermined precision.

[0011] Some embodiments further comprise a pin end disposed on an opposed longitudinal end of the pipe segment. The pin end comprises an inner shoulder surface at the opposed longitudinal end, a threaded section adjacent to the inner shoulder surface and increasing in diameter in a direction away from the shoulder surface, and an outer shoulder surface adjacent to an end of the threaded section opposed to the inner shoulder.

[0012] Other aspects and possible advantages will be apparent from the description and claims that follow.Brief Description of the Drawings

[0013] FIG. 1 shows an example of a box end of a double shoulder tool joint known in the art.

[0014] FIG. 2 shows an example of a box end of a single shoulder tool joint known in the art.

[0015] FIG. 3 shows a box end of a double shoulder tool joint according to the present disclosure.

[0016] FIG. 4 shows an oblique view of circumferential locating bores in the pipe wall of the box end of FIG. 4.

[0017] FIG. 5 shows a pin end of a double shoulder tool joint according to the present disclosure.Detailed Description

[0018] An example embodiment of a box end 30 of a tool joint according to the present disclosure is shown in cross section view in FIG. 3. The box end 30 may comprise a longitudinal end of a pipe segment having an inner wall 33 and an outer wall 32, wherein the inner wall 33 defines a minimum internal diameter D2 comparable to the inner diameter of a pipe segment having a single shoulder threaded connector. The longitudinal end of the pipe segment may have formed therein a threaded connector 44 of pitch, taper and minimum / maximum diameters comparable to a single shoulder threaded connector wherein the shoulder is an outer shoulder such as shown at 42 in FIG. 3. The inner wall 33 may comprise a threaded section 40. An externally threaded threaded shoulder sleeve 34 may be threadedly engaged to the threaded section 40, such that a longitudinal end 34A of the shoulder sleeve 34 may perform the same function as the torque (inner) shoulder of a double shoulder threaded connector (tool joint) as shown in FIG. 1. The threaded shoulder sleeve 34 may be removed from the box end 30 to enable insertion of downhole tools (not shown) having diameter larger than an internal diameter D3 of the shoulder sleeve 34, and smaller than the internal diameter D2 of the inner wall 33. A length 38 of the shoulder sleeve 34 may be chosen to enable the shoulder sleeve 34 to support the maximum axial and torsional loading expected on a similarly sized double shoulder tool joint (see FIG. 1).

[0019] It will be appreciated that a consideration in making a double shoulder tool joint is the depth 36 of the inner shoulder (longitudinal end 34A of the shoulder sleeve 34) with respect to the outer shoulder 42. According to the present disclosure, the shoulder sleeve may 34 be rotated to cause it to move axially within the tool joint 30 until the shouldersleeve is located at the desired axial position (to provide the correct depth 36), in order to suitably contact the inner shoulder on a mating pin end (see FIG. 5). In the present example embodiment, the shoulder sleeve 34 may be subsequently rotationally locked within the threaded section 40 by one or more lock pins 46 passed through one or more circumferentially spaced apart pin bores 47 in the shoulder sleeve 34, into one or more circumferentially spaced apart locking bores 44 in the threaded section 40. The pin bores 47 may be, for example, circularly shaped and provide tight fit for the lock pins 46, which may also have substantially circular cross section shape. The locking bores 44 may be oval shaped, elongated in the longitudinal direction of the box end 30 wherein the lock pins 46 may fit within the locking bores 44 so as to limit rotation of the threaded sleeve 34, while enabling engagement of the lock pins 46 with the locking bores 44 over a limited axial position range. In this way, the shoulder sleeve 34 may be rotated into its chosen axial position within the box end 30 and further rotated until the closest orientation at which the pin bores 47 align with the locking bores 44. The lock pin(s) 46 may be inserted into one or more of the aligned pin bores 46 and locking bores 44. The lock pin(s) may be held in place within the pin bore(s) 46 by a corresponding retaining clip 48, e.g., an internal snap ring or retaining rings. An example of the oval shape of the locking bores 44 may be observed in FIG. 4. It will be appreciated that the precision with which the depth 36 may be set corresponds to, among other parameters, the pitch of the threads on the shoulder sleeve 34 and the threaded section 40, and the number of and circumferential spacing between adjacent pin bores 46 and locking bores 44.

[0020] FIG. 5 shows an example embodiment of a pin end 50 of a double shoulder tool joint. The pin end 50 may be conventionally formed as other double shoulder tool joints, and may comprise, at an opposed longitudinal end of the pipe segment as the box end shown in FIG. 3, a tool joint exterior surface 52 at a base of a threaded section 56. The threaded section 52 may have pitch, diameter and taper to engage the threaded section on the box end (30 in FIG. 3) of an adjacent pipe segment. An outer shoulder 54 may be formed at the longitudinal end of the tool joint exterior surface 52 as is conventional for double shoulder tool joints. An inner shoulder 58 may be disposed at a longitudinal end of the threaded section 56. The inner shoulder 58 will engage the longitudinal end (34A inFIG. 3) of the shoulder sleeve (34 in FIG. 3) when the pin end 50 is assembled to a box end (30 in FIG. 3) of an adjacent pipe segment. The pin end 50 may comprise a through bore having a diameter D3 comparable to that of a conventional double shoulder tool joint, as explained above with reference to FIGS. 3 and 4. To obtain the larger internal diameter (D2 in FIG. 3), when a segment of pipe is made, the inner wall (33 in FIG. 3) may be formed, e.g., machined or drawn over mandrel to have the larger internal diameter D2 at the box end and smaller internal diameter D3 at the pin end as shown in FIG. 5.

[0021] A tool joint according to the present disclosure may enable insertion of downhole tools into one or more drill string segments that would otherwise be excluded by reason of the necessarily smaller internal diameter of double shoulder tool joints known in the art prior to the present disclosure.

[0022] In light of the principles and example embodiments described and illustrated herein, it will be recognized that the example embodiments can be modified in arrangement and detail without departing from such principles. The foregoing discussion has focused on specific embodiments, but other configurations are also contemplated. In particular, even though expressions such as in “an embodiment," or the like are used herein, these phrases are meant to generally reference embodiment possibilities, and are not intended to limit the disclosure to particular embodiment configurations. As used herein, these terms may reference the same or different embodiments that are combinable into other embodiments. As a rule, any embodiment referenced herein is freely combinable with any one or more of the other embodiments referenced herein, and any number of features of different embodiments are combinable with one another, unless indicated otherwise. Although only a few examples have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible within the scope of the described examples. Accordingly, all such modifications are intended to be included within the scope of this disclosure as defined in the following claims.

Claims

ClaimsWhat is claimed is:

1. A tool joint for a pipe string, comprising: a box end having a female threaded section disposed proximate a longitudinal end of a pipe segment; a threaded section formed on an interior wall of the pipe segment proximate a base of the female threaded section, the threaded section having formed therein at least one locking bore for receiving a locking pin, the at least one receiving bore being oval shaped and elongated in a longitudinal direction of the pipe segment; a shoulder sleeve having on an exterior surface thereof threads for engaging the threaded section, and at least one pin bore through a wall of the shoulder sleeve; and at least one locking pin passed through the pin bore to engage the at least one locking bore when the at least one pin bore is rotationally and longitudinally aligned with the at least one locking bore.

2. The tool joint of claim 1 further comprising a locking ring to retain the at least one locking pin in the at least one pin bore.

3. The tool joint of claim 1 further comprising a plurality of circumferentially spaced apart pin bores in the shoulder sleeve and a plurality of corresponding circumferentially spaced apart locking bores in the threaded section.

4. The tool joint of claim 3 wherein a pitch of the threaded section and the threads on the shoulder sleeve, and a number of and circumferential spacing of the pin bores and the locking bores chosen to enable axially locating the shoulder sleeve in the box end to a predetermined precision.

5. The tool joint of claim 1 further comprising a pin end disposed on an opposed longitudinal end of the pipe segment, the pin end comprising an inner shoulder surface at the opposed longitudinal end, a threaded section adjacent to the inner shoulder surface and increasingin diameter in a direction away from the shoulder surface, and an outer shoulder surface adjacent to an end of the threaded section opposed to the inner shoulder.

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