Threaded Tubular Fittings

Abstract

A threaded tubular coupling for drilling or operating a hydrocarbon well is provided. [Solution] A threaded tubular joint comprising: a metal pin member (3) having a longitudinal axis (2), a tapered two-step wedge pin thread (4) with a dovetail-type wedge thread, and a pin sealing surface (7) located between the small diameter pin thread step (5) and the large diameter pin thread step (6); and a metal box member (9) having a tapered two-step wedge box thread (10) with a dovetail-type wedge thread, and a box sealing surface (13) located between the small diameter box thread step (11) and the large diameter box thread step (12), wherein the joint does not have any final assembly stop shoulders that define the final assembly position of the pin member relative to the box member, and the small diameter wedge thread set and the large diameter wedge thread set are sized to have a first axial gap (21) and a second axial gap (22).

Description

[Technical field]

[0001] The present invention relates to a threaded tubular joint for drilling or operating a hydrocarbon well. The tubular joint is used to connect two tubing sections together to form a larger tube. This type of tubing can be drilling tubing, casing, liner or other oilfield tubing frequently used to drill, complete or produce wells.

[0002] Generally, in male-female threaded tubular joints, the male component of the joint is referred to as the "pin member" and the female component is referred to as the "box member." The term "assembly" refers to engaging the pin member within the box member and threading the members together by applying a torque.

[0003] The pin and box members typically have cooperating sealing surfaces which, after assembly is complete, contact one another to form a metal-to-metal seal which seals the interior of the connected tube sections from the exterior.

[0004] With reference to the thread geometry, the term "load flank" refers to the opposite facing sidewall of the thread at the outer end of each of the pin or box members on which the threads are formed, which supports the weight of the lower tube (i.e., a tensile load) when placed in a vertical position (e.g., suspended in a wellbore). Similarly, the term "stab flank" refers to the opposite facing sidewall of the thread at the outer end of each of the pin or box members, which supports the force pressing the joint together (i.e., a compressive force), such as the weight of the upper tubular member during initial assembly of the joint, or the force applied to press the lower tubular member against the bottom of a wellbore. [Background technology]

[0005] A "wedge thread" is characterized by a thread that increases in width in opposite directions relative to the pin and box members, regardless of the particular thread form. The rate of change of thread width along the joint is commonly defined by a variable known as the "wedge ratio." Wedge ratio (although not technically a ratio) refers to the difference between the stub flank lead and the load flank lead, which results in the change in thread width along the joint. Thread "lead" refers to the differential distance between thread components on successive threads. Thus, "stub flank lead" is the distance between the stub flanks of successive thread pitches along the axial length of a threaded tubular joint.

[0006] A detailed discussion of wedge ratios is provided in US Patent No. 5,399,323 to Mallis and assigned to the assignee of the present invention, which is incorporated herein by reference in its entirety.

[0007] Wedge threads are disclosed in U.S. Patent No. 5,393,433 issued to Blose, U.S. Patent No. 5,393,433 issued to Reeves, U.S. Patent No. 5,393,433 issued to Ortloff, and U.S. Patent No. 5,393,433 issued to Mott, all of which are assigned to the assignee of the present invention and are incorporated by reference in their entireties herein.

[0008] While various wedge thread joints exist that have a final assembly stop shoulder that defines the final assembled position of the pin member relative to the box member when rotational assembly is completed, wedge threads generally do not have such a final assembly stop shoulder, which makes their assembly "indeterminate" and as a result the position of the pin member relative to the box member can vary much more for a given torque range applied during assembly than is the case for tubular joints that have a final assembly stop shoulder.

[0009] As described above, "assembly" refers to screwing the pin member and the box member together, and final assembly refers to a state in which the assembly is completed by screwing the pin member and the box member together to a desired torque amount.

[0010] The fact that the assembly of a tubular fitting having a radial metal-to-metal seal and a wedge thread and no final assembly stop shoulder is indeterminate is a major problem because radial metal-to-metal seals require very precise relative positioning of the sealing faces of the male and female elements. For proper operation, precise positioning of the sealing faces is necessary to create the correct contact pressure. Thus, the sealing faces need to be positioned in specific positions relative to each other, and variations in their final position may cause the sealing faces to not create the required contact pressure.

[0011] In tubular fittings with wedge threads, the wedging effect between the threads will dominate the assembly process, therefore the axial position of the seal face is usually measured relative to the threads.

[0012] When having a tubular fitting with two-step threads, one thread step must be selected as the reference thread step to axially position the sealing faces. Since both wedge thread steps are indeterminate, it is not known which thread step will determine the assembly and therefore the positioning of the sealing faces. If the positioning of the sealing faces is not based on the thread step that governs the assembly process, the axial position of the sealing faces relative to each other in the final assembly cannot be ensured. This can cause seal isolation and can lead to tightness issues. [Prior art documents] [Patent documents]

[0013] [Patent Document 1] U.S. Patent No. 6,206,436 [Patent Document 2] U.S. Reissue Patent No. 30,647 [Patent Document 3] U.S. Reissue Patent No. 34,467 [Patent Document 4] U.S. Patent No. 4,703,954 [Patent Document 5] U.S. Patent No. 5,454,605 Summary of the Invention

[0014] It is an object of the present invention to provide an improved, or at least alternative, threaded tubular joint. The tubular joint according to the present invention includes a longitudinal axis, a metal pin member, and a metal box member. The pin member has a tapered two-step wedge pin thread, the thread including a small diameter pin thread step, a large diameter pin thread step, and a pin seal surface located between the small diameter pin thread step and the large diameter pin thread step. The small diameter pin thread step and the large diameter pin thread step each include an external dovetail wedge thread. The metal box member has a tapered two-step wedge box thread, the thread including a small diameter box thread step, a large diameter box thread step, and a box seal surface located between the small diameter box thread step and the large diameter box thread step. The small diameter box thread step and the large diameter box thread step each include an internal dovetail wedge thread. The wedge threads of the two-step wedge pin thread and the wedge threads of the two-step wedge box thread have a stub flank and a load flank. The smaller diameter pin thread step and the box thread step are configured to cooperate during rotational assembly of the tubular fitting to form a smaller diameter wedge thread set. The larger diameter pin and box thread steps are configured to cooperate during rotational assembly of the tubular fitting to form a larger diameter wedge thread set. The pin sealing surface and the box sealing surface are configured to form a radial metal-to-metal seal. The tubular fitting does not have any final assembly stop shoulders that define a final assembly position of the pin member relative to the box member. One of the smaller diameter wedge thread set and the larger diameter wedge thread set is configured to cooperate during rotational assembly of the tubular fitting. One of the small diameter wedge thread set and the large diameter wedge thread set is sized to have a first axial gap between its wedge threads in a main portion of the rotary assembly of the tubular coupling, and the other of the small diameter wedge thread set and the large diameter wedge thread set is sized to have a second axial gap between its wedge threads in said main portion of the rotary assembly of the tubular coupling. The first axial gap is greater than the second axial gap. The main portion of the rotary assembly of the tubular coupling relates to the application of a torque to the tubular coupling during assembly, the torque being 20-80% of an optimum assembly torque.

[0015] The rotational assembly of the tubular joint, and thus the positioning of the pin and box sealing faces relative to each other, is determined by the wedge thread set that is energized first. Since the first axial clearance is larger than the second axial clearance, the wedge thread set with the second axial clearance will certainly be energized first and therefore will dominate the assembly. Thus, by selecting the wedge threads with the second axial clearance as the reference thread set, it is ensured that the reference thread set is the one that dominates the assembly. This allows a more accurate positioning of the pin and box sealing faces relative to each other to be achieved when the assembly is of a tubular joint with two-step wedge threads and the final assembly stop shoulder is not completed.

[0016] The specifications for tube sections with threaded tubular fittings sold in the art always indicate an optimum assembly torque for completing the rotational assembly of the fitting, the optimum assembly torque being between the maximum assembly torque and the minimum assembly torque.

[0017] The second axial clearance wedge thread set is actually sufficiently biased to govern assembly at a torque of about 20% of the optimum assembly torque. When 80% torque is reached, the pin and box members are actually in their final positions relative to each other. This means that when torques greater than (and up to) 80% of the optimum assembly torque are applied during assembly, there is not any (significant) displacement between the pin and box members. As a result, the pin and box sealing surfaces have actually reached their final positions relative to each other when a torque of 80% of the optimum assembly torque is applied during assembly.

[0018] When a torque of 20-80% of the optimum assembly torque is applied during assembly, due to the fact that the second axial clearance is smaller than the first axial clearance, it is ensured that the wedge thread set with the second axial clearance dominates the assembly from the moment of full bias until the pin and box sealing faces reach their final position relative to each other.

[0019] In one embodiment of the tubular fitting, the first axial clearance and the second axial clearance are 0 mm at the optimum make-up torque, which means that the load flanks of the minor wedge thread set and the major wedge thread set each touch each other at the optimum make-up torque and the stab flanks of the minor wedge thread set and the major wedge thread set each touch each other at the optimum make-up torque.

[0020] In one embodiment of the tubular joint, the pin member includes a further pin sealing surface and the box member includes a further box sealing surface, the further pin sealing surface and the further box sealing surface being configured to cooperate with each other to form a further radial metal-metal seal, and a wedge thread set with a first axial clearance is located between the radial metal-metal seal and the further radial metal-metal seal. The assembly of the wedge thread set between the radial metal-metal seal and the further radial metal-metal seal is influenced by both radial metal-metal seals, especially in the situation where said wedge thread set is provided with a dovetail wedge thread. A radial disturbance in both radial metal-metal seals will move the pin member inwards and the box member outwards. This may have an effect on the wedge threads of said wedge thread set. If a dovetail wedge thread is used, the pin and box members This movement would cause further wedging between the dovetailed wedge threads. If a second axial clearance wedge thread set were located between both radial metal-to-metal seals, this could result in premature termination of the assembly, thus isolating the seals.

[0021] In one embodiment of the tubular joint, the tubular joint includes only one radial metal-to-metal seal.

[0022] In one embodiment of the tubular coupling, the first axial gap is twice as large as the second axial gap.

[0023] In one embodiment of the tubular fitting, the wedge threads of the wedge thread set having the first axial clearance include a first stub flank gap at their stub flank and a first load flank gap at their load flank, and the wedge threads of the wedge thread set having the second axial clearance include a second stub flank gap at their stub flank and a second load flank gap at their load flank.

[0024] In one embodiment of the tubular fitting, the first stab flank gap is smaller than the second stab flank gap. The wedge thread set with the first axial clearance may have a much lower torque interference when assembled compared to the wedge thread set with the second axial clearance. Making the first stab flank gap smaller than the second stab flank gap will result in a higher torque interference in the wedge thread set with the first axial clearance.

[0025] In one embodiment of the tubular fitting, the first stab flank clearance is equal to the second stab flank clearance minus 0.010-0.015 mm (or 0.013 mm). This tends to create a preferred higher torque interference in the wedge thread set with the first axial clearance.

[0026] In one embodiment of the tubular fitting, the first stab flank clearance is equal to the second stab flank clearance minus 0.0004 to 0.0006 inches (or 0.0005 inches).

[0027] In one embodiment of the tubular fitting, the first load flank gap is greater than the second load flank gap.

[0028] In one embodiment of the tubular fitting, the second load flank clearance is 0 mm (meaning the load flanks are in contact with each other), which has a positive effect in governing the rotational assembly using a wedge thread set with a second axial clearance.

[0029] In one embodiment of the tubular fitting, the first stab flank clearance is 0.010-0.015 mm (or 0.013 mm), the first load flank clearance is 0.035-0.040 mm (or 0.038 mm), and the second stab flank clearance is 0.023-0.028 mm (or 0.025 mm), which allows for more precise control of the rotational assembly.

[0030] In one embodiment of the tubular fitting, the first stab flank clearance is 0.0004 to 0.0005 inches (or 0.0005 inches), the first load flank clearance is 0.0014 to 0.0016 inches (or 0.0015 inches), and the second stab flank clearance is 0.0009 to 0.0011 inches (or 0.001 inches).

[0031] In one embodiment of the tubular fitting, the first load flank gap is greater than the first stab flank gap.

[0032] In one embodiment of the tubular fitting, the second stab flank clearance is greater than the second load flank clearance.

[0033] In one embodiment of the tubular fitting, the first axial gap is defined by a first stub flank gap and a first load flank gap, and the second axial gap is defined by a second stub flank gap and a second load flank gap.

[0034] In one embodiment of the tubular fitting, the pin member includes a pin free end, and the wedge thread set having a first axial clearance is located closer to the pin free end than the wedge thread set having a second axial clearance.

[0035] In one embodiment of the tubular fitting, the pin member includes a pin free end, and a set of wedge threads having a first axial clearance are located further from the pin free end than a set of wedge threads having a second axial clearance.

[0036] The features of the tubular coupling embodiments described above may be combined to form any number of any combination of the embodiments.

[0037] The invention further relates to a method for assembling a threaded tubular joint according to the invention, the method comprising the steps of selecting a wedge thread set having a second axial clearance as a reference thread set for rotational assembly of the tubular joint, and controlling assembly of the threaded tubular joint based on the reference thread set to position the pin sealing surface and the box sealing surface relative to each other.

[0038] In one embodiment of the method, the step of positioning the pin sealing surface and the box sealing surface relative to one another is controlled by applying a torque to the tubular joint from 20% of an optimum assembly torque to 80% of an optimum assembly torque.

[0039] Embodiments of a threaded tubular joint and a method of assembling a threaded tubular joint will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, in which: [Brief description of the drawings]

[0040] [Figure 1A] 1 shows a schematic cross-sectional view of a first embodiment of a tubular coupling according to the invention; [Figure 1B] 1B shows a schematic cross-sectional view of a pin member of the tubular joint of FIG. 1A. [Figure 1C] 1B shows a schematic cross-sectional view of a box member of the tubular joint of FIG. 1A. [Figure 1D] 1B shows a schematic enlarged view of portion D of FIG. 1A during rotational assembly. [Figure 1E] 1B shows a schematic enlarged view of portion E of FIG. 1A during rotational assembly. [Figure 1F] 1D shows a first alternative embodiment in accordance with FIG. [Figure 1G] 1C shows a schematic diagram of a first alternative embodiment with respect to FIG. 1E. [Figure 1H] 1D shows a second alternative embodiment. [Figure 1I] 1C shows a schematic diagram of a second alternative embodiment with respect to FIG. 1E. [Diagram 2] 2 shows diagrammatically a cross-sectional view of a second embodiment of a tubular coupling according to the invention; [Diagram 3] 3 shows diagrammatically a cross-sectional view of a third embodiment of a tubular coupling according to the invention; [Figure 4] 3 shows diagrammatically a cross-sectional view of a fourth embodiment of a tubular coupling according to the invention; [Diagram 5] 1B shows a schematic diagram of a graph for assembling the tubular joint of FIG. 1A; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0041] Figure 1A shows a cross-sectional view of a first embodiment of a tubular coupling 1 according to the invention. The tubular coupling 1 comprises a longitudinal axis 2, a metal pin member 3, and a metal box member 9. The tubular coupling 1 is shown after rotational assembly of the tubular coupling 1 is completed.

[0042] 1B shows a cross-sectional view of pin member 3. Pin member 3 has a tapered two-step wedge pin thread 4 including a small pin thread step 5, a large pin thread step 6, and a pin seal surface 7 located between small pin thread step 5 and large pin thread step 6. Small pin thread step 5 and large pin thread step 6 each include an external dovetail wedge thread 8. Pin member 3 has a free pin end 34.

[0043] 1C shows a cross-sectional view of box member 9. Metal box member 9 has a tapered two-step wedge box thread 10 including a small box thread step 11, a large box thread step 12, and a box sealing face 13 located between small box thread step 11 and large box thread step 12. Small box thread step 11 and large box thread step 12 each include an internal dovetail wedge thread 14. Box member 9 has a free box end 35.

[0044] 1A, the small diameter pin thread step 5 and the box thread step 11 are configured to cooperate during rotational assembly of the tubular fitting 1 from small diameter wedge thread set 15. The large diameter pin thread step 6 and the box thread step 12 are configured to cooperate during rotational assembly of the tubular fitting 1 from large diameter wedge thread set 16.

[0045] The pin sealing surface 7 and the box sealing surface 13 are configured to form a radial metal-to-metal seal 17. The pin member 3 includes a further pin sealing surface 23 and the box member 9 includes a further box sealing surface 24. The further pin sealing surface 23 and the further box sealing surface 24 are configured to form a further radial metal-to-metal seal 25.

[0046] The tubular coupling 1 does not have any final assembly stop shoulder that defines the final assembly position of the pin member 3 relative to the box member 9. The box member 9 has an over-assembly stop shoulder 36 to limit damage to the tubular coupling 1 in the event of over-rotation assembly.

[0047] When rotational assembly of the tubular coupling 1 is complete, the pin member 3 is positioned relative to the box member 9 as shown in Figure 1A. The pin free end 34 of the pin member 3 is positioned away from the overassembly torque shoulder 36 of the box member 9. Thus, there is no abutment of the pin free end 34 against the overassembly stop shoulder 36. This makes the rotational assembly of the tubular coupling 1 "indeterminate."

[0048] The small diameter wedge thread set 15 is sized to have a first axial gap 21 between its wedge threads 8, 14 in the main portion of the rotating assembly of the tubular fitting 1. The large diameter wedge thread set 16 is sized to have a second axial gap 22 between its wedge threads 8, 14 in the main portion of the rotating assembly of the tubular fitting 1. Because the first axial gap 21 is greater than the second axial gap 22, the large diameter wedge thread set 16 determines the positioning of the pin sealing surface 7 and the box sealing surface 13 relative to one another.

[0049] A major part of the rotational assembly of the tubular coupling 1 involves applying a torque to the tubular coupling 1 during assembly, which torque is between 20 and 80% of the optimum assembly torque.

[0050] The tubular fitting 1 allows the large diameter wedge thread set 16 (having the second axial clearance 22) to be selected as the reference thread set 19 for the rotational assembly of the tubular fitting 1. Thus, the rotational assembly of the tubular fitting 1 can be controlled based on the reference thread set 19 to position the pin sealing surface 7 and the box sealing surface 13 relative to each other. In a similar manner it also applies to the further pin sealing surface 23 and the further box sealing surface 24 .

[0051] The smaller wedge thread set 15 (having a first axial gap 21) is located closer to the pin free end 34 than the larger wedge thread set 16 (having a second axial gap 22).

[0052] The assembly of the tubular fitting 1 is completed when the optimum assembly torque is reached. The first axial clearance 21 and the second axial clearance 22 may be 0 mm at the optimum assembly torque. This means that in each of the small diameter wedge thread set 15 and the large diameter wedge thread set 16, the load flanks 29A, 29B contact each other at the optimum assembly torque and the stab flanks 28A, 28B contact each other at the optimum assembly torque.

[0053] Figures 1D and 1E respectively show schematic enlarged views of parts D and E of Figure 1A in the main part of the rotating assembly. Wedge thread 8 of two-step wedge pin thread 4 has stab flank 28A and load flank 29A. Wedge thread 14 of two-step wedge box thread 10 has stab flank 28B and load flank 29B.

[0054] The wedge threads 8, 14 of the smaller wedge thread set 15 include a first stub flank gap 30 at their stub flanks 28A, 28B (FIG. 1D). The wedge threads 8, 14 of the larger wedge thread set 16 include a second stub flank gap 31 at their stub flanks 28A, 28B (FIG. 1E).

[0055] The wedge threads 8, 14 of the smaller wedge thread set 15 include a first load flank gap 32 at their load flanks 29A, 29B (FIG. 1D). The wedge threads 8, 14 of the larger wedge thread set 16 include a second load flank gap 33 at their load flanks 29A, 29B (FIG. 1E).

[0056] The first stub flank gap 30 and the first load flank gap 32 are the same size. The second stub flank gap 31 and the second load flank gap 33 are the same size.

[0057] The first axial gap 21 is defined by a first stub flank gap 30 and a first load flank gap 32. The second axial gap 22 is defined by a second stub flank gap 31 and a second load flank gap 33.

[0058] 1F and 1G show a first alternative embodiment of FIGs. 1D and 1G, respectively. In this first alternative embodiment, first stub flank gap 30 is smaller than second stub flank gap 31. First load flank gap 32 is larger than second load flank gap 33.

[0059] Because first axial gap 21 is larger than second axial gap 22, smaller diameter wedge thread set 15 may have a much lower torque interference when assembled as compared to larger diameter wedge thread set 16. Having first stab flank gap 30 smaller than second stab flank gap 31 would result in a higher torque interference in smaller diameter wedge thread set 15.

[0060] In another alternative embodiment, the first load flank gap 32 is made smaller than the second load flank gap 32. In that condition, the first stab flank gap 30 would be larger than the second stab flank gap 31.

[0061] Figures 1H and 1I show a second alternative embodiment with respect to Figures 1D and 1E, respectively. In this second alternative, the first stub flank gap 30 is smaller than the second stub flank gap 31. The first load flank gap 32 is larger than the second load flank gap 33. More specifically, the second load flank gap 33 is 0 mm (meaning that the load flanks 29A, 29B are in contact with each other).

[0062] In addition, the first load flank gap 32 is larger than the first stab flank gap 30 and the second stab flank gap 31 is larger than the second load flank gap 33. This has a positive effect on the interference between the cooperating wedge threads 8, 14 of the wedge thread sets 15, 16.

[0063] The first stub flank gap 30 is 0.013 mm, the first load flank gap 32 is 0.038 mm, and the second stub flank gap 31 is 0.025 mm. In another embodiment of the tubular fitting 1, the first stub flank gap 30 is 0.010-0.015 mm, the first load flank gap 32 is 0.035-0.040 mm, and the second stub flank gap 31 is 0.023-0.028 mm.

[0064] As shown in Figure 1A, the small diameter wedge thread set 15 (having a first axial gap 21) is located between the radial metal-metal seal 17 and the further radial metal-metal seal 25. Assembly of the small diameter wedge thread set 15 is affected by both radial metal-metal seals 17, 25. Radial interference at both radial metal-metal seals 17, 25 would cause the pin member 3 to move inwardly and the box member 9 to move outwardly. Because the small diameter wedge thread set 15 includes dovetailed wedge threads 8, 14, this movement of the pin and box members 3, 9 would result in further wedging between the dovetailed wedge threads 8, 14.

[0065] Figure 2 shows a cross-sectional view of a second embodiment of a tubular joint 1 according to the invention. This embodiment differs from Figure 1 in that the large diameter wedge thread set 16 is dimensioned to have a first axial gap 21 between its wedge threads 8, 14 in the main part of the rotating assembly of the tubular joint 1, and the small diameter wedge thread set 15 is dimensioned to have a second axial gap 22 between its wedge threads 8, 14 in said main part of the rotating assembly of the tubular joint 1. In addition, a further radial metal-metal seal 25 is located near the box free end 35. The wedge thread set with the first axial gap 21 is located further from the pin free end 34 than the wedge thread set with the second axial gap 22.

[0066] Figure 3 shows a cross-sectional view of a third embodiment of a tubular fitting 1 according to the invention. This embodiment differs from figure 1 in that the tubular fitting 1 includes only one radial metal-to-metal seal 17. The small diameter wedge thread set 15 is dimensioned to have a first axial gap 21 between its wedge threads 8, 14 in the main part of the rotating assembly of the tubular fitting 1, and the large diameter wedge thread set 16 is dimensioned to have a second axial gap 22 between its wedge threads 8, 14 in said main part of the rotating assembly of the tubular fitting 1.

[0067] Figure 4 shows a cross-sectional view of a fourth embodiment of a tubular fitting 1 according to the invention. This embodiment differs from figure 3 in that the large diameter wedge thread set 16 is dimensioned to have a first axial gap 21 between its wedge threads 8, 14 in the main part of the rotating assembly of the tubular fitting 1, and the small diameter wedge thread set 15 is dimensioned to have a second axial gap 22 between its wedge threads 8, 14 in said main part of the rotating assembly of the tubular fitting 1.

[0068] FIG. 5 shows a graph for the assembly of the tubular joint of FIG. 1A. The relationship between the rotation (N) between the pin member 3 and the box member 9 and the assembly torque (T) is shown. The optimum assembly torque (Top) is 20% of the optimum assembly torque (T 0.2 ) and 80% (T 0.8 ) levels. During assembly, the optimum displacement between the pin sealing surface 7 and the box sealing surface 13 to obtain a tight radial metal-to-metal seal 17 is applied at 20-80% of the optimum assembly torque.

[0069] The invention further relates to a threaded joint and a method according to any of the following clauses: 1. A threaded tubular joint for drilling or operating a hydrocarbon well, comprising: a longitudinal axis; a metallic pin member having a tapered two-step wedge pin thread including a small pin thread step, a large pin thread step, and a pin sealing surface located between the small pin thread step and the large pin thread step, wherein the small pin thread step and the large pin thread step each include an external dovetail wedge thread; a metal box member having a tapered two-step wedge box thread including a small diameter box thread step, a large diameter box thread step, and a box sealing surface located between the small diameter box thread step and the large diameter box thread step, wherein the small diameter box thread step and the large diameter box thread step each include an internal dovetail wedge thread; Including, The wedge threads of the two-step wedge pin thread and the two-step wedge box thread have a stub flank and a load flank; the small diameter pin thread step and the box thread step are configured to cooperate during rotational assembly of the tubular fitting to form a small diameter wedge thread set; the large diameter thread step pin and the box thread step are configured to cooperate during rotational assembly of the tubular fitting to form a large diameter wedge thread set; the pin sealing surface and the box sealing surface are configured to form a radial metal-to-metal seal; the tubular joint does not have any final assembly stop shoulder that defines the final assembly position of the pin member relative to the box member; A threaded tubular joint, wherein one of the small diameter wedge thread set and the large diameter wedge thread set are sized to have a first axial clearance between their wedge threads in a main portion of a rotating assembly of the tubular joint, and the other of the small diameter wedge thread set and the large diameter wedge thread set are sized to have a second axial clearance between their wedge threads in said main portion of a rotating assembly of the tubular joint, the first axial clearance being greater than the second axial clearance. 2. A threaded tubular joint according to clause 1, wherein a wedge thread set having a second axial clearance determines the positioning of the pin sealing surface and the box sealing surface relative to each other during the main part of the rotational assembly. 3. Threaded tubular joints according to clause 1 or 2, where the main part of the rotational assembly of the tubular joint is the application of a torque of 20 to 80% of the optimum assembly torque to the tubular joint during assembly. 4. A threaded tubular fitting according to any one of clauses 1 to 3, wherein the pin member includes a further pin sealing surface and the box member includes a further box sealing surface, the further pin sealing surface and the further box sealing surface are configured to cooperate with each other to form a further radial metal-to-metal seal, and a wedge thread set having a first axial clearance is located between the radial metal-to-metal seal and the further radial metal-to-metal seal. 5. A threaded tubular joint according to any one of clauses 1 to 3, wherein the tubular joint contains only one radial metal-to-metal seal. 6. the wedge threads of the wedge thread set having a first axial clearance include a first stub flank gap at their stub flanks and a first load flank gap at their load flanks; - the wedge threads of the wedge thread set having a second axial clearance have a second stub flank clearance at their stub flanks and a second load flank clearance at their load flanks; Including the right flank clearance, Threaded tubular joints according to any one of clauses 1 to 5. 7. A threaded tubular joint according to clause 6, wherein the first stub flank gap is smaller than the second stub flank gap. 8. A threaded tubular joint according to clause 6 or 7, wherein the first stub flank clearance is equal to the second stub flank clearance minus 0.010 to 0.015 mm (or 0.013 mm). 9. A threaded tubular joint according to any one of clauses 6 to 8, wherein the first load flank gap is greater than the second load flank gap. 10. A threaded tubular joint according to any one of clauses 6 to 9, wherein the second load flank clearance is 0 mm. 11. A threaded tubular fitting according to any one of clauses 6 to 10, wherein the first stub flank gap is 0.010 to 0.015 mm (or 0.013 mm), the first load flank gap is 0.035 to 0.040 mm (or 0.038 mm), and the second stub flank gap is 0.023 to 0.028 mm (or 0.025 mm). 12. A threaded tubular joint according to any one of clauses 6 to 11, wherein the first load flank gap is larger than the first stab flank gap and / or the second stab flank gap is larger than the second load flank gap. 13. A threaded tubular fitting according to any one of clauses 6 to 12, wherein the pin member includes a pin free end, and the wedge thread set having a first axial clearance is located at a location closer to the pin free end than the wedge thread set having a second axial clearance. 14. A threaded tubular fitting according to any one of clauses 1 to 12, wherein the pin member includes a pin free end, and wherein a wedge thread set having a first axial gap is located at a location farther from the pin free end than a wedge thread set having a second axial gap. 15. A threaded tubular joint according to any one of clauses 1 to 14, wherein the first axial clearance and the second axial clearance are 0 mm at the optimum assembly torque. 16. A method for assembling a threaded tubular joint according to any of clauses 1 to 15 comprising the steps of: - selecting the second axial clearance wedge thread set as a reference thread set for rotational assembly of the tubular joint; - controlling assembly of the threaded tubular joint based on a reference thread set to position the pin sealing surface and the box sealing surface relative to each other. 17. The method according to clause 16, wherein the step of positioning the pin and box sealing surfaces relative to one another is controlled by applying a torque to the tubular joint from 20% of the optimum assembly torque to 80% of the optimum assembly torque.

[0070] Although detailed embodiments of the present invention are disclosed herein as necessary, it should be understood that the disclosed embodiments are merely exemplary of the present invention, which may be embodied in various forms. Therefore, the specific structural and functional details disclosed herein should not be construed as limiting, but should be construed only as a basis for the claims, and should in fact be construed as a representative basis for teaching those skilled in the art to use the various structures in any suitable structure as detailed. Moreover, the terms and expressions used herein are not intended to be limiting, but rather to provide an understandable description of the present invention.

[0071] The terms "a" or "an," as used herein, are defined as one or more than one. The term "plurality," as used herein, is defined as two or more than two. The term "other," as used herein, is defined as at least a second or more. The terms "comprises" and / or "has," as used herein, are defined as including (i.e., open language that does not exclude other elements or steps). The appearance of any reference in the claims should not be construed as limiting the scope of the present invention.

[0072] It will be apparent to those skilled in the art that various modifications can be made to the threaded tubular joint and method without departing from the scope thereof as defined in the claims and clauses.

Claims

1. A threaded tubular joint (1) for drilling or operating a hydrocarbon well, comprising: - a longitudinal axis (2), - a metal pin member (3) having a tapered two-step wedge pin thread (4) including a small pin thread step (5), a large pin thread step (6) and a pin sealing surface (7) located between said small pin thread step and said large pin thread step, said small pin thread step and said large pin thread step each including an external dovetail wedge thread (8); - a metal box member (9) having a tapered two-step wedge box thread (10) including a small diameter box thread step (11), a large diameter box thread step (12) and a box sealing surface (13) located between said small diameter box thread step and said large diameter box thread step, said small diameter box thread step and said large diameter box thread step each including an internal dovetail wedge thread (14); Including, --the wedge threads of the two-step wedge pin thread and the two-step wedge box thread have a stub flank (28) and a load flank (29); --the small diameter pin thread step and the box thread step are configured to cooperate during rotational assembly of the tubular fitting to form a small diameter wedge thread set; - said large diameter pin and box thread step are configured to cooperate during rotational assembly of said tubular fitting to form a large diameter wedge thread set (15); --the pin sealing surface and the box sealing surface are configured to form a radial metal-to-metal seal (17); --said tubular joint does not have any final assembly stop shoulder defining the final assembly position of said pin member relative to said box member; one of the small diameter wedge thread set and the large diameter wedge thread set has a first axial clearance (21) between its wedge threads in the main portion of the rotating assembly of the tubular coupling, and the other of the small diameter wedge thread set and the large diameter wedge thread set has a second axial clearance (22) between its wedge threads in the main portion of the rotating assembly of the tubular coupling, the first axial clearance being greater than the second axial clearance; said main portion of said rotational assembly of said tubular coupling comprises applying a torque to said tubular coupling during assembly that is between 20 and 80% of an optimum assembly torque, said first axial clearance and said second axial clearance being 0 mm at said optimum assembly torque; the first axial gap is defined by a first stab flank gap and / or a first load flank gap, and the second axial gap is defined by a second stab flank gap and / or a second load flank gap. Threaded tubular fittings.

2. 2. The threaded tubular joint of claim 1, wherein said wedge thread set having said second axial clearance determines the orientation of said pin sealing surface and said box sealing surface relative to one another during said main portion of said rotational assembly.

3. 3. The threaded tubular joint according to claim 1, wherein the pin member includes a further pin sealing surface (23) and the box member includes a further box sealing surface (24), the further pin sealing surface and the further box sealing surface being configured to cooperate with each other to form a further radial metal-to-metal seal, and the wedge thread set with the first axial clearance is located between the radial metal-to-metal seal and the further radial metal-to-metal seal.

4. 3. A threaded tubular joint according to claim 1, wherein the tubular joint comprises only one radial metal-to-metal seal.

5. the wedge threads of the wedge thread set having the first axial clearance include a first stub flank clearance (30) at their stub flank and a first load flank clearance (32) at their load flank; the wedge threads of the wedge thread set having the second axial clearance include a second stub flank clearance (31) at their stub flank and a second load flank clearance (33) at their load flank, Threaded tubular joint according to any one of claims 1 to 4.

6. 6. The threaded tubular joint of claim 5, wherein the first stab flank gap is smaller than the second stab flank gap.

7. 7. A threaded tubular joint as claimed in claim 5 or 6, wherein the first stab flank gap is equal to the second stab flank gap minus 0.010-0.015 mm (or 0.013 mm).

8. 8. A threaded tubular joint according to claim 5, wherein the first load flank gap is larger than the second load flank gap.

9. A threaded tubular joint according to any one of claims 5 to 8, wherein the second load flank clearance is 0 mm.

10. 10. A threaded tubular joint according to any one of claims 5 to 9, wherein the first stab flank clearance is 0.010 to 0.015 mm (or 0.013 mm), the first load flank clearance is 0.035 to 0.040 mm (or 0.038 mm) and the second stab flank clearance is 0.023 to 0.028 mm (or 0.025 mm).

11. 11. A threaded tubular joint according to any one of claims 5 to 10, wherein the first load flank gap is larger than the first stab flank gap and / or the second stab flank gap is larger than the second load flank gap.

12. 12. The threaded tubular joint according to any one of claims 1 to 11, wherein the pin member includes a pin free end (34), and the wedge thread set having the first axial clearance is located at a location closer to the pin free end than the wedge thread set having the second axial clearance.

13. 12. The threaded tubular joint according to any one of claims 1 to 11, wherein the pin member includes a pin free end (34), and the set of wedge threads having the first axial clearance is located at a location further from the pin free end than the set of wedge threads having the second axial clearance.

14. A method for assembling a threaded tubular joint according to any one of claims 1 to 13, comprising the steps of: - selecting the wedge thread set with the second axial clearance as a reference thread set for the rotational assembly of the tubular joint; - controlling the assembly of the threaded tubular joint based on the reference thread set to position the pin sealing surface and the box sealing surface relative to each other.

15. 15. The method of claim 14, wherein the step of positioning the pin sealing surface and the box sealing surface relative to one another is controlled by applying a torque to the tubular fitting from 20% of the optimum assembly torque to 80% of the optimum assembly torque.

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