Threaded connection for exploration and production of a hydrocarbon well

Abstract

A threaded connection for exploration and production of a hydrocarbon well, wherein the threaded connection comprises a pin and a box extending along a longitudinal axis, the pin comprises a two-step pin thread comprising a large diameter pin thread step having a first pin thread and a small diameter pin thread step having a second pin thread, and the box comprises a two-step box thread comprising a large diameter box thread step having a first box thread and a small diameter box thread step having a second box thread.

Description

104095-5039THREADED CONNECTION FOR EXPLORATION AND PRODUCTION OF A HYDROCARBON WELL FIELD OF THE INVENTION

[0001] The invention relates to a threaded connection for exploration and production of a hydrocarbon well.

[0002] The threaded connection comprises a pin and a box extending along a longitudinal axis. The pin comprises a two-step pin thread comprising a large diameter pin thread step having a first pin thread and a small diameter pin thread step having a second pin thread. The box comprises a two-step box thread comprising a large diameter box thread step having a first box thread and a small diameter box thread step having a second box thread.

[0003] The first pin thread and the first box thread are varying-thread-width threads which cooperate with each other during rotational make-up of the threaded connection to create thread interference between the first pin thread and the first box thread at final make-up of the threaded connection. The second pin thread and the second box thread are varying-thread-width threads which cooperate with each other during rotational make-up of the threaded connection to create thread interference between the second pin thread and the second box thread at final make-up of the threaded connection.

[0004] The thread interference between the cooperating pin and box threads is formed by a wedging effect created during rotational make-up between the varying-thread-width threads. Varying-thread-width threads are disclosed in U.S. Pat. No. RE 30,647 issued to Blose, U.S. Pat. No. RE 34,467 issued to Reeves, U.S. Pat. No. 4,703,954 issued to Ortloff, and U.S. Pat. No. 5.454,605 issued to Mott.BACKGROUND OF THE INVENTION

[0005] The make-up of this ty pe of threaded connection comprises two subsequent phases. In the first phase (also referred to as the stabbing phase), the pin and box are aligned, and the pin is stabbed into the box until a final stabbing position is reached in which the pin is in contact with the box. During said stabbing of the pin into the box, the pin and box are only moved relative to each other in axial direction with respect to the longitudinal axis. In the subsequent second phase (also referred to as the rotational make-up phase), the pin and the box are rotated relative to each in order to thread the pin and box together until final make-up of the threadedconnection has been reached. During said rotational make-up of the threaded connection, the pin and the box are rotated relative to each other about the longitudinal axis and move relative to each other in axial direction as result of the rotational make-up. The term final make-up refers to the situation in which the rotational make-up has been completed by threading the pin and the box together up to a desired amount of torque or up to a predetermined position of the pin and the box relative to each other. At final make-up, the pin and the box do not move relative to each other.SUMMARY OF THE INVENTION

[0006] The known threaded connections have the disadvantage that the threads of the pin and the box are relatively susceptible to damage. This reveals itself amongst others when the pin and box are reused to assemble and disassemble the threaded connection several times. This increases the risk of an impaired functioning of the threaded connection. This may result in a shorter lifetime or a reduced reusability of the threaded connection or even leakage of hydrocarbon fluid during use of the threaded connection. The invention is based on the insight that a significant part of the damage to the pin and the box is caused by the make-up process of the threaded connection.BRIEF DESCRIPTION OF THE INVENTION

[0007] The invention has the objective to provide an improved, or at least alternative, threaded connection for exploration and production of a hydrocarbon well. Said threaded connection comprises a pin having a two-step pin thread comprising a large diameter pin thread step having a first pin thread and a small diameter pin thread step having a second pin thread, and a box having a two-step box thread comprising a large diameter box thread step having a first box thread and a small diameter box thread step having a second box thread, wherein the pin and the box extend along a longitudinal axis, the first pin thread and the first box thread are varying-thread-width threads which cooperate with each other during rotational make-up of the threaded connection to create thread interference between the first pin thread and the first box thread at final make-up of the threaded connection, the second pin thread and the second box thread are varying-thread-width threads which cooperate with each other during rotational make-up of the threaded connection to create thread interference between the second pin thread and the secondbox thread at said final make-up of the threaded connection, the pin comprises an external pin sealing surface, the box comprises an external box sealing surface, the external pin sealing surface and the external box sealing surface are configured to cooperate with each other during said rotational make-up to form an external radial metal-to-metal seal at said final make-up of the threaded connection, the first pin thread comprises a first pin stab flank and a first pin load flank, the second pin thread comprises a second pin stab flank and a second pin load flank, the first box thread comprises a first box stab flank and a first box load flank, the second box thread comprises a second box stab flank and a second box load flank, the first pin thread and the first box thread are configured to have contact between at least part of the first pin stab flank and at least part of the first box stab flank upon stabbing of the pin into the box, the second pin thread and the second box thread are configured to have the second pin stab flank spaced from the second box stab flank and have the second pin load flank spaced from the second box load flank upon said stabbing of the pin into the box, and the pin and the box are configured to, during said rotational make-up of the threaded connection, force the external pin sealing surface against the external box sealing surface and thereby move the first pin stab flank and the first box stab flank away from each other and place at least part of the first pin load flank in contact with at least part of the first box load flank, while the second pin stab flank remains spaced from the second box stab flank and the second pin load flank remains spaced from the second box load flank.

[0008] During stabbing of the pin into the box, the pin and box are aligned and only moved relative to each other in axial direction with respect to the longitudinal axis.

[0009] Upon stabbing of the pin into the box relates to the situation that a final stabbing position of the pin relative to the box has been reached in which there is contact between the pin and the box. Said final stabbing position is reached before the rotational make-up of the threaded connection is started.

[0010] During rotational make-up of the threaded connection, the pin and the box are rotated relative to each other about the longitudinal axis and move relative to each other in axial direction as result of the rotational make-up.

[0011] Final make-up refers to the situation in which the rotational make-up has been completed by threading the pin and the box together up to a desired amount of torque or up to a predetermined position of the pin and the box relative to each other. At final make-up, the pin and the box do not move relative to each other.

[0012] When the first pin stab flank and the first box stab flank are moved away from each other, the first pin stab flank and the first box stab flank are positioned at a distance from each other. Said distance between the first pin stab flank and the first box stab flank may also be referred to as a first stab flank clearance between the first pin stab flank and the first box stab flank.

[0013] When the external pin sealing surface and the external box sealing surface come into contact during rotation make-up of the threaded connection, the forming of the external radial metal-to-metal seal is started. As a result, fluid-like dirt (e g. mud) present in the threaded connection will not be able to leave the threaded connection via said external pin / box sealing surfaces. If fluid-like dirt gets trapped in the threaded connection during make-up, this can lead to high stresses within the threaded connection. This tends to result in damage to threads of the pin and the box.

[0014] As the interaction of the external pin sealing surface with the external box sealing surface during rotational make-up moves the first pin stab flank and the first box stab flank away from each other, space is created in the large diameter pin / box thread step for the fluid-like dirt to flow away from the external radial metal-to-metal seal. The second pin stab flank remaining spaced from the second box stab flank and the second pin load flank remaining spaced from the second box load flank allows that the fluid-like dirt can flow away. It allows that (part of) the fluid-like dirt can flow out of the large diameter pin / box thread step and may even allow that (part of) the fluid-like dirt flows into the small diameter pin / box thread step. This reduces the risk of damage to threads of the pin and the box caused by fluid-like dirt being trapped in the threaded connection during rotational make-up.

[0015] In addition, in varying-thread-width threads the final make-up is reached based on thread interference. If (too much) fluid-like dirt remains in the threaded connection during make-up, this can lead to higher unwanted fluid pressures trapped in the threaded connection that could lead to false make-up readings relating the degree of thread interference when analysing if final make-up has been reached. As such, the pushing out of fluid-like dirt is in particular important in threaded connections having varying-thread-width threads.

[0016] In an embodiment of said threaded connection, the pin comprises an internal pin sealing surface, the box comprises an internal box sealing surface, the internal pin sealing surface and the internal box sealing surface are configured to cooperate with each other during saidrotational make-up to form an internal radial metal-to-metal seal at said final make-up of the threaded connection.

[0017] In an embodiment of said threaded connection, the pin and the box are configured to, during said rotational make-up of the threaded connection, place the internal pin sealing surface in contact with the internal box sealing surface after said placing in contact of at least part of the first pin load flank with at least part of the first box load flank.

[0018] In an embodiment of said threaded connection, the pin and the box are configured to, during said rotational make-up of the threaded connection, place the internal pin sealing surface in contact with the internal box sealing surface after said placing in contact of the external pin sealing surface with the external box sealing surface.

[0019] In an embodiment of said threaded connection, the first pin thread comprises a first pin crest and a first pin root; the second pin thread comprises a second pin crest and a second pin root; the first box thread comprises a first box crest and a first box root; the second box thread comprises a second box crest and a second box root; and the pin and box are configured such that, at the start of said rotational make-up of the threaded connection, the first pin crest is spaced from the first box root, the first pin root is spaced from the first box crest, the second pin crest is spaced from the second box root, and the second pin root is spaced from the second box crest.

[0020] In an embodiment of said threaded connection, the second pin thread comprises a second pin crest and a second pin root, the second box thread comprises a second box crest and a second box root, the second pin thread and the second box thread are configured to have crest-root interference between the second pin thread and the second box thread at said final make-up of the threaded connection, and the pin and the box are configured to, during said rotational makeup of the threaded connection, place the second pin crest in contact with the second box root and / or place the second pin root in contact with the second box crest after said placing in contact of the internal pin sealing surface with the internal box sealing surface.

[0021] In an embodiment of said threaded connection, the first pin thread comprises a first pin crest and a first pin root, the first box thread comprises a first box crest and a first box root, the first pin thread and the first box thread are configured to have crest-root interference between the first pin thread and the first box thread at said final make-up of the threaded connection, the pin comprises an intermediate pin sealing surface, the box comprises an intermediate box sealing surface, the intermediate pin sealing surface and the intermediate box sealing surface areconfigured to cooperate with each other during said rotational make-up to form an intermediate radial metal-to-metal seal at said final make-up of the threaded connection, and either:- the pin and the box are configured to, during said rotational make-up of the threaded connection, place the intermediate pin sealing surface in contact with the intermediate box sealing surface after said placing in contact of the first pin crest with the first box root and / or said placing in contact of second the pin root with the second box crest, OR- the pin and the box are configured to, during said rotational make-up of the threaded connection, place the first pin crest in contact with the first box root and / or place the first pin root in contact with the first box crest after said placing in contact of the intermediate pin sealing surface with the intermediate box sealing surface.

[0022] In an embodiment of said threaded connection, the pin and the box are configured to, during said rotational make-up of the threaded connection, place the first pin crest in contact with the first box root and / or place the first pin root in contact with the first box crest after said placing in contact of the second pin crest with the second box root and / or said placing in contact of the second pin root with the second box crest.

[0023] In an embodiment of said threaded connection, the pin and the box are configured to, during said rotational make-up of the threaded connection, place the intermediate pin sealing surface in contact with the intermediate box sealing surface after said placing in contact of the second pin crest with the second box root and / or said placing in contact of the second pin root with the second box crest.

[0024] In an embodiment of said threaded connection, the pin and the box are configured to, during said rotational make-up of the threaded connection, place the first pin stab flank in contact with the first box stab flank after said placing in contact of the first pin crest with the first box root and / or said placing in contact of the first pin root with the first box crest.

[0025] In an embodiment of said threaded connection, the pin and the box are configured to, during said rotational make-up of the threaded connection, place the second pin stab flank in contact with the second box stab flank and place the second pin load flank in contact with the second box load flank after said placing in contact of the second pin crest with the second box root and / or said placing in contact of the second pin root with the second box crest.

[0026] In an embodiment of said threaded connection, the first pin thread and the first box thread form a first set of cooperating dovetail threads, and the second pin thread and the second box thread form a second set of cooperating dovetail threads.

[0027] In an embodiment of said threaded connection, the threaded connection is free from any final make-up stop shoulder defining a final make-up position for the pin relative to the box at said final make-up of the threaded connection.

[0028] The feature that the threaded connection is free from a final make-up stop shoulder defining a final make-up position for the pin relative to the box at said final make-up of the threaded connection could in other words be defined as that the threaded connection is configured for indeterminate rotational make-up.

[0029] In an embodiment of said threaded connection, the pin comprises a pin terminal end and an unthreaded pin base section, the two-step pin thread is located between the pin terminal end and the unthreaded pin base section, the box comprises a box terminal end and an unthreaded box base section, the two-step box thread is located between the box terminal end and the unthreaded box base section, the external pin sealing surface is located between the unthreaded pin base section and the first pin thread, and the external box sealing surface is located between the box terminal end and the first box thread.

[0030] In an embodiment of said threaded connection, the internal pin sealing surface is located between the second pin thread and the pin terminal surface, and the internal box sealing surface is located between the unthreaded box base section and the second box thread.

[0031] In an embodiment of said threaded connection, the intermediate pin sealing surface is located between the first pin thread and the second pin thread, and the intermediate box sealing surface is located between the first box thread and the second box thread.

[0032] In an embodiment of said threaded connection, the first pin thread and the first box thread are configured to have the first pin load flank and the first box load flank spaced from each other upon said stabbing of the pm into the box.

[0033] In an embodiment of said threaded connection, the second pin thread and the second box thread are configured to have the second pin load flank and the second box load flank spaced from each other upon said stabbing of the pin into the box.

[0034] In an embodiment of said threaded connection, the external pin sealing surface and the external box sealing surface are configured to, during said rational make-up of the threadedconnection, provide with the external pin sealing surface a counterforce acting on the external box sealing surface to move the first pin stab flank and the first box stab flank away from each other.

[0035] It will be clear to the skilled person that in a further embodiment said threaded connection may comprise the features of any combination of the above described embodiments of said threaded connection.

[0036] The invention further relates to a method of making up said threaded connection, wherein said method comprises the steps of placing at least part of the first pin stab flank in contact with at least part of the first box stab flank upon stabbing of the pin into the box and before rotational make-up of the threaded connection is started, while having the second pin stab flank spaced from the second box stab flank and the second pin load flank spaced from the second box load flank upon said stabbing of the pin into the box, and forcing the external pin sealing surface against the external box sealing surface, during the rotational make-up of the threaded connection, and thereby moving the first pin stab flank and the first box stab flank away from each other and placing at least part of the first pin load flank in contact with at least part of the first box load flank, while the second pin stab flank remains spaced from the second box stab flank and the second pin load flank remains spaced from the second box load flank.

[0037] The invention further relates to a threaded connection for exploration and production of a hydrocarbon well, said threaded connection comprising:- a pin having a single-step pin thread comprising a pin thread, and- a box having a single-step box thread comprising a box thread, wherein- the pin and the box extend along a longitudinal axis,- the pin thread and the box thread are varying-thread-width threads which cooperate with each other during rotational make-up of the threaded connection to create thread interference between the pin thread and the box thread at final make-up of the threaded connection,- the pin comprises an external pin sealing surface,— the box comprises an external box sealing surface,— the external pin sealing surface and the external box sealing surface are configured to cooperate with each other during said rotational make-up to form an external radial metal-to-metal seal at said final make-up of the threaded connection, — the pin thread comprises a pin stab flank and a pin load flank.- the box thread comprises a box stab flank and a box load flank,- the pin thread and the box thread are configured to have contact between at least part of the pin stab flank and at least part of the box stab flank upon stabbing of the pin into the box, and- the pin and the box are configured to, during said rotational make-up of the threaded connection, force the external pin sealing surface against the external box sealing surface and thereby move the pin stab flank and the box stab flank away from each other and place at least part of the pin load flank in contact w ith at least part of the box load flank.BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Embodiments of said threaded connection and said method will be described by w ay of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, and in which:

[0039] Figure 1 A schematically shows a cross sectional view along the longitudinal axis of one side of an embodiment of said threaded connection at final make-up,

[0040] Figure IB schematically shows a cross sectional view along the longitudinal axis of the complete threaded connection of figure 1A,

[0041] Figure 2 schematically shows a cross sectional view along the longitudinal axis of the box of the threaded connection of figure 1 A,

[0042] Figure 3 schematically show s a cross sectional view along the longitudinal axis of the pin of the threaded connection of figure 1 A,

[0043] Figure 4 schematically shows a cross sectional view along the longitudinal axis of the threaded connection of figure 1 A upon stabbing of the pin into the box,

[0044] Figure 5A schematically shows an enlarged view of part of the first pin thread and the first box thread during a first stage of the rotational make-up of the threaded connection of figure 1A,

[0045] Figure 5B schematically shows an enlarged view of part of the second pin thread and the second box thread during a first stage of the rotational make-up of the threaded connection of figure 1A,

[0046] Figure 6A schematically shows an enlarged view of part of the first pin thread and the first box thread during a second stage of the rotational make-up of the threaded connection of figure 1A,

[0047] Figure 6B schematically shows an enlarged view of part of the second pin thread and the second box thread during a second stage of the rotational make-up of the threaded connection of figure 1A,

[0048] Figure 7A schematically shows an enlarged view of part of the first pin thread and the first box thread during a third stage of the rotational make-up of the threaded connection of figure 1A,

[0049] Figure 7B schematically shows an enlarged view of part of the second pin thread and the second box thread during a third stage of the rotational make-up of the threaded connection of figure 1A,

[0050] Figure 8A schematically shows an enlarged view of part of the first pin thread and the first box thread during a fourth stage of the rotational make-up of the threaded connection of figure 1A.

[0051] Figure 8B schematically shows an enlarged view of part of the second pin thread and the second box thread during a fourth stage of the rotational make-up of the threaded connection of figure 1 A,

[0052] Figure 9A schematically shows an enlarged view of part of the first pin thread and the first box thread during a fifth stage of the rotational make-up of the threaded connection of figure 1A.

[0053] Figure 9B schematically shows an enlarged view of part of the second pin thread and the second box thread during a fifth stage of the rotational make-up of the threaded connection of figure 1 A,

[0054] Figure 10A schematically shows an enlarged view of part of the first pin thread and the first box thread during a sixth stage of the rotational make-up of the threaded connection of figure 1A, and

[0055] Figure 10B schematically shows an enlarged view of part of the second pin thread and the second box thread during a sixth stage of the rotational make-up of the threaded connection of figure 1A.DETAILED DESCRIPTION OF THE DRAWINGS

[0056] The figures 1A and IB show cross sectional views along the longitudinal axis 14 of an embodiment of the threaded connection 1 according to the invention at final make-up 17. The threaded connection 1 is configured for the exploration and production of a hydrocarbon well. Figure 2 shows a cross sectional view along the longitudinal axis 14 of the box 8 of the threaded connection 1 of figure 1 A. Figure 3 shows a cross sectional view along the longitudinal axis 14 of the pin 2 of the threaded connection 1 of figure 1 A,

[0057] The pin 2 and the box 8 extend along a longitudinal axis 14. The axial direction 55 and the radial direction 56 with respect to the longitudinal axis 14 is indicated in figure 1A. The inner diameter Di and the outer diameter Do of the threaded connection 1 are indicated in figure IB.

[0058] The pin 2 comprises a two-step pin thread 3 with a large diameter pin thread step 4 having a first pin thread 5 and a small diameter pin thread step 6 having a second pin thread 7. The box 8 comprises a two-step box thread 9 with a large diameter box thread step 10 having a first box thread 11 and a small diameter box thread step 12 having a second box thread 13.

[0059] The pin 2 comprises a pin terminal end 51 and an unthreaded pin base section 52. The two-step pin thread 3 is located between the pin terminal end 51 and the unthreaded pin base section 52. The box 8 comprises a box terminal end 53 and an unthreaded box base section 54. The two-step box thread 9 is located between the box terminal end 53 and the unthreaded box base section 54.

[0060] The first pin thread 5 and the first box thread 11 are varying-thread-width threads 15 which cooperate with each other during rotational make-up of the threaded connection 1 to create thread interference between the first pin thread 5 and the first box thread 11 at final makeup 17 of the threaded connection 1. The second pin thread 7 and the second box thread 13 are varying-thread-width threads 15 which cooperate with each other during rotational make-up of the threaded connection 1 to create thread interference between the second pin thread 7 and the second box thread 13 at final make-up 17 of the threaded connection 1.

[0061] The first pin thread 5 and the first box thread 11 form a first set of cooperating dovetail threads 49. The second pin thread 7 and the second box thread 13 form a second set of cooperating dovetail threads 50.

[0062] The first pin thread 5 comprises a first pin stab flank 21 and a first pin load flank 22. The second pin thread 7 comprises a second pin stab flank 23 and a second pin load flank 24. The first box thread 11 comprises a first box stab flank 25 and first box load flank 26. The second box thread 13 comprises a second box stab flank 27 and second box load flank 28.

[0063] The first pin thread 5 and the first box thread 11 are configured to create flank interference in axial direction 55 with respect to the longitudinal axis 14 at final make-up 17 of the threaded connection 1. The second pin thread 7 and the second box thread 13 are configured to create flank interference in axial direction 55 with respect to the longitudinal axis 14 at final make-up 17 of the threaded connection 1.

[0064] More specifically, the first pin thread 5 and the first box thread 11 are configured to create flank interference between the first pin stab flank 21 and the first box stab flank 25 and between the first pin load flank 22 and the first box load flank 26 at final make-up 17 of the threaded connection 1. The second pin thread 7 and the second box thread 13 are configured to create flank interference between the second pin stab flank 23 and the second box stab flank 27 and between the second pin load flank 24 and the second box load flank 28 at final make-up 17 of the threaded connection 1.

[0065] The first pin thread 5 and the first box thread 11 are configured to create crest-root interference in radial direction 56 with respect to the longitudinal axis 14 at final make-up 17 of the threaded connection 1. The second pin thread 7 and the second box thread 13 are configured to create crest-root interference in radial direction 56 with respect to the longitudinal axis 14 at final make-up 17 of the threaded connection 1.

[0066] The pin 2 comprises an external pin sealing surface 18. The box 8 comprises an external box sealing surface 19. The external pin sealing surface 18 and the external box sealing surface 19 are configured to cooperate with each other during said rotational make-up to form an external radial metal -to-metal seal 20 at said final make-up 17 of the threaded connection 1. The external pin sealing surface 18 is located between the unthreaded pin base section 52 and the first pin thread 5. The external box sealing surface 19 is located between the box terminal end 53 and the first box thread 11.

[0067] The pin 2 comprises an internal pin sealing surface 30. The box 8 comprises an internal box sealing surface 31. The internal pin sealing surface 30 and the internal box sealing surface 31 are configured to cooperate with each other during said rotational make-up to form an internalradial metal-to-metal seal 36 at said final make-up 17 of the threaded connection 1. The internal pin sealing surface 30 is located between the second pin thread 7 and the pin 2 terminal surface. The internal box sealing surface 31 is located between the unthreaded box base section 54 and the second box thread 13.

[0068] The pin 2 comprises an intermediate pin sealing surface 46. The box 8 comprises an intermediate box sealing surface 47. The intermediate pin sealing surface 46 and the intermediate box sealing surface 47 are configured to cooperate with each other during said rotational make-up to form an intermediate radial metal-to-metal seal 48 at said final make-up 17 of the threaded connection 1. The intermediate pin sealing surface 46 is located between the first pin thread 5 and the second pin thread 7. The intermediate box sealing surface 47 is located between the first box thread 11 and the second box thread 13.

[0069] The threaded connection 1 is free from a final make-up stop shoulder defining a final make-up position for the pin 2 relative to the box 8 at said final make-up 17 of the threaded connection 1. This makes the rotational make-up of the threaded connection 1 “indeterminate” and, as a result, the position of the pin 2 relative to the box 8 may vary more during make-up for a given torque range to be applied than for threaded connections having a final make-up stop shoulder. Hence, the make-up of threaded connections with a final make-up stop shoulder differs from the make-up of threaded connections without a final make-up stop shoulder.

[0070] The make-up of the threaded connection 1 comprises two subsequent phases. In the first phase (also referred to as the stabbing phase), the pin 2 and the box 8 are aligned, and the pin 2 is stabbed into the box 8 until a final stabbing position 29 is reached in which the pin 2 is in contact with the box 8. During said stabbing of the pin 2 into the box 8, the pin 2 and box 8 are only moved relative to each other in axial direction 55 with respect to the longitudinal axis 14. In the subsequent second phase (also referred to as the rotational make-up phase), the pin 2 and the box 8 are rotated relative to each in order to thread the pin 2 and box 8 together until final make-up 17 of the threaded connection 1 has been reached. During said rotational make-up of the threaded connection 1, the pin 2 and the box 8 are rotated relative to each other about the longitudinal axis 14 and move relative to each other in axial direction 55 as result of the rotational make-up. The term final make-up 17 refers to the situation in which the rotational make-up has been completed by threading the pin 2 and the box 8 together up to a desired amount of torque or up to a predetermined position of the pin 2 and the box 8 relative to each other. At final make-up 17, the pin 2 and the box 8 do not move relative to each other.

[0071] In another embodiment of the threaded connection 1, the threaded connection 1 comprises single-step threads instead of two-step threads 3, 9. With reference to the figures 1-4, said threaded connection with single-step threads may have the below described configuration.

[0072] The single-step pin thread of the pin 2 has the large diameter pin thread step 4 having the first pin thread 5 and does not have the small diameter pin thread step 6 having the second pin thread 7. The single-step box thread of the box 8 has the large diameter box thread step 10 having the first box thread 11 and does not have the small diameter box thread step 12 having the second box thread 13. The pin 2 has the external pin sealing surface 18 and the box 8 has the external box sealing surface 19. The first pin thread 5 and the first box thread 11 are configured to have contact between at least part of the first pin stab flank 21 and at least part of the first box stab flank 25 upon stabbing of the pin 2 into the box 8. The pin 2 and the box 8 are configured to, during rotational make-up of the threaded connection 1 , force the external pin sealing surface 18 against the external box sealing surface 19 and thereby move the first pin stab flank 21 and the first box stab flank 25 away from each other and place at least part of the first pin load flank 22 in contact with at least part of the first box load flank 26.

[0073] In one example of said threaded connection 1 having single-step threads, the pin 2 has the intermediate pin sealing surface 46 and does not have the internal pin sealing surface 30, and the box 8 has the intermediate box sealing surface 47 and does not have the internal box sealing surface 31.

[0074] In another example of said threaded connection 1 having single-step threads, the pin 2 has the internal pin sealing surface 30 and does not have the intermediate pin sealing surface 46, and the box 8 has the internal box sealing surface 31 and does not have the intermediate box sealing surface 47.

[0075] In yet another example of said threaded connection 1 having single-step threads, the pin 2 comprises an alternative pin sealing surface which combines the functions of the internal pin sealing surface 30 and the intermediate pin sealing surface 46, and the box 8 comprises an alternative box sealing surface which combines the functions of the internal box sealing surface 31 and the intermediate box sealing surface 47.

[0076] Figure 4 shows a cross sectional view along the longitudinal axis 14 of the threaded connection 1 of figure 1A upon stabbing of the pin 2 into the box 8. The first pin thread 5 and the first box thread 11 are configured to have contact between at least part of the first pin stabflank 21 and at least part of the first box stab flank 25 upon stabbing of the pin 2 into the box 8. The second pin thread 7 and the second box thread 13 are configured to have the second pin stab flank 23 spaced from the second box stab flank 27 and have the second pin load flank 24 spaced from the second box load flank 28 upon said stabbing of the pin 2 into the box 8.

[0077] Said stabbing of the pin 2 into the box 8 relates to the situation that a final stabbing position 29 of the pin 2 relative to the box 8 has been reached in which there is contact between the pin 2 and the box 8. Said final stabbing position 29 is reached before the rotational make-up of the threaded connection 1 is started.

[0078] The pin 2 and the box 8 are configured to, during said rotational make-up of the threaded connection 1 , force the external pin sealing surface 18 against the external box sealing surface 19 and thereby move the first pin stab flank 21 and the first box stab flank 25 away from each other and place at least part of the first pin load flank 22 in contact with at least part of the first box load flank 26, while the second pin stab flank 23 remains spaced from the second box stab flank 27 and the second pin load flank 24 remains spaced from the second box load flank 28.

[0079] When the first pin stab flank 21 and the first box stab flank 25 are moved away from each other, the first pin stab flank 21 and the first box stab flank 25 are positioned at a distance from each other. Said distance between the first pin stab flank 21 and the first box stab flank 25 may also be referred to as a first stab flank clearance between the first pin stab flank 21 and the first box stab flank 25.

[0080] When the external pin sealing surface 18 and the external box sealing surface 19 come into contact during rotation make-up of the threaded connection 1, the forming of the external radial metal-to-metal 20 seal is started. As a result, fluid-like dirt (e.g. mud) present in the threaded connection 1 will not be able to leave the threaded connection 1 via said external pin / box sealing surfaces 18, 19. If fluid-like dirt gets trapped in the threaded connection 1 during make-up, this can lead to high stresses within the threaded connection 1. This tends to result in damage to threads of the pin 2 and the box 8.

[0081] As the interaction of the external pin sealing surface 18 with the external box sealing surface 19 during rotational make-up moves the first pin stab flank 21 and the first box stab flank 25 away from each other, space is created in the large diameter pin / box thread step 4, 10 for the fluid-like dirt to flow away from the external radial metal-to-metal seal 20. The second pin stab flank 23 remaining spaced from the second box stab flank 27 and the second pin loadflank 24 remaining spaced from the second box load flank 28 allows that the fluid-like dirt can flow away. It allows that (part of) the fluid-like dirt can flow out of the large diameter pin / box thread step 4, 10 and may even allow that (part of) the fluid-like dirt flows into the small diameter pin / box thread step 6, 12 and out of the threaded connection 1. This reduces the risk of damage to threads of the pin 2 and the box 8 caused by fluid-like dirt being trapped in the threaded connection 1 during rotational make-up. In addition, the make-up sequence tends to create a more even distribution of the stresses during the entire make-up process instead of only at the end of make-up process.

[0082] In varying-thread- width threads 15 the final make-up 17 is reached based on thread interference. If (too much) fluid-like dirt remains in the threaded connection 1 during make-up, this can lead to higher unwanted fluid pressures trapped in the threaded connection 1 that could lead to false make-up readings relating the degree of thread interference when analysing if final make-up has been reached. As such, the pushing out of fluid-like dirt is in particular important in threaded connections having varying-thread-width threads.

[0083] Due to the fact that the stab flanks 21, 25 of the first pin thread 5 and the first box thread 11 (forming the large diameter pin / box thread step 4, 10) have contact upon stabbing of the threaded connection 1 and the stab flanks 23, 27 of the second pin thread 7 and the second box thread 13 (forming the small diameter pin / box thread step 6, 12) are spaced from each other, the forces created between the pin 2 and the box 8 having contact with each other upon stabbing are absorbed by the first pin stab flank 21 and the first box stab flank 25 and transferred through the pin 2 and the box 8 via the first pin thread 5 and the first box thread 11. Since the first pin thread 5 and the first box thread 11 are located at the large diameter pin / box thread step 4, 10, said forces are absorbed and transferred over a relatively larger surface area when compared with the small diameter pin / box thread step 6, 12. This tends to lead to lower stresses in the first pin thread 5 and the first box thread 11 and therefore a lower risk to damage the first pin thread 5 and the first box thread 11. The term relatively larger surface area relates to the fact that the stab flanks 21, 25 of one turn of the first pin thread 5 and the first box thread 11 located at the large diameter pin / box thread step 4, 10 have a larger surface area when compared with the stab flanks 23, 27 of one turn of the second pin thread 7 and the second box thread 13 located at the small diameter pin I box thread step 6, 12.

[0084] Furthermore, the stabbing of the threaded connection 1 is controlled by the first pin thread 5 and the first box thread 11 of the large diameter pin / box thread step 4. 10 havingcontact upon said stabbing of the pin 2 into the box 8. This has the advantage that since the large diameter pin / box thread step 4, 10 is designed to control the stabbing, the design of the second pin thread 7 and the second box thread 13 of the small diameter pin / box thread step 6, 12 can be dedicated to control other aspects, such as removal of fluid-like dirt from the threaded connection 1 during rotational make-up. This is made possible because no forces created by the pm 2 and the box 8 having contact with each other upon stabbing tend to be absorbed and transferred by the second pin thread 7 and second box thread 13.

[0085] Since the stabbing of the threaded connection 1 is controlled by the large diameter pin / box thread step 4, 10, deviation of the small diameter pin / box thread step 6, 12 with respect to the large diameter pin / box thread step 4, 10 does not tend to form a risk, or at least a reduced risk, to misalignment of the threaded connection 1 during make-up.

[0086] Threaded connections with a final make-up stop shoulder tend to have a lower production capacity due to the space required by the final make-up stop shoulder. The maximum outer diameter of the threaded connection 1 is in practice determined by the dimensions of the hydrocarbon well. Since a final make-up stop shoulder requires space in radial direction 56, there is less space available for the inner diameter of the threaded connection 1 forming the channel through which the hydrocarbon fluid flows. A smaller inner diameter results in a smaller channel and therefore a smaller production capacity.

[0087] The figures 5A and 5B show an enlarged view of part of the first pin thread 5 and the first box thread 11 and part of the second pin thread 7 and the second box thread 13, respectively, during a first stage of the rotational make-up of the threaded connection 1 of figure 1 A.

[0088] In said first stage, the rotational make-up of the threaded connection 1 has just started and there is no contact between the external pin sealing surface 18 and the external box sealing surface 19. There is contact betw een at least part of the first pin stab flank 21 and at least part of the first box stab flank 25 of the pin 2 into the box 8. The first pin load flank 22 and the first box load flank 26 spaced from each other. The second pin stab flank 23 remains spaced from the second box stab flank 27 and the second pin load flank 24 remains spaced from the second box load flank 28.

[0089] The first pin crest 41 is spaced from the first box root 44 and the first pin root 42 is spaced from the first box crest 43. The second pin crest 37 is spaced from the second box root 40 and the second pin root 38 is spaced from the second box crest 39.

[0090] The figures 6A and 6B show an enlarged view of part of the first pin thread 5 and the first box thread 11 and part of the second pin thread 7 and the second box thread 13. respectively, during a second stage of the rotational make-up of the threaded connection 1 of figure 1 A.

[0091] In said second stage, the rotational make-up of the threaded connection 1 is continued and the external pin sealing surface 18 has been placed in contact with the external box sealing surface 19. The external pin sealing surface 18 is forced against the external box sealing surface 19 to move the first pin stab flank 21 and the first box stab flank 25 away from each other. The second pin stab flank 23 remains spaced from the second box stab flank 27 and the second pin load flank 24 remains spaced from the second box load flank 28.

[0092] The first pin crest 41 is spaced from the first box root 44 and the first pin root 42 is spaced from the first box crest 43. The second pin crest 37 is spaced from the second box root 40 and the second pin root 38 is spaced from the second box crest 39.

[0093] The figures 7 A and 7B show an enlarged view of part of the first pin thread 5 and the first box thread 11 and part of the second pin thread 7 and the second box thread 13, respectively, during a third stage of the rotational make-up of the threaded connection 1 of figure 1 A.

[0094] In said third stage, the rotational make-up of the threaded connection 1 is continued and the external pin sealing surface 18 is forced against the external box sealing surface 19 to move the first pin stab flank 21 and the first box stab flank 25 further away from each other. At least part of the first pin load flank 22 is in contact with at least part of the first box load flank 26. The second pin stab flank 23 remains spaced from the second box stab flank 27 and the second pin load flank 24 remains spaced from the second box load flank 28.

[0095] The figures 8A and 8B show an enlarged view of part of the first pin thread 5 and the first box thread 11 and part of the second pin thread 7 and the second box thread 13, respectively, during a fourth stage of the rotational make-up of the threaded connection 1 of figure 1 A.

[0096] In said fourth stage, the rotational make-up of the threaded connection 1 is continued and the internal pin sealing surface 30 has been placed in contact with the internal box sealing surface 31. Subsequently, the second pin crest 37 is placed in contact with the second box root 40 and the second pin root 38 is placed in contact with the second box crest 39. The first pin crest 41 is spaced from the first box root 44 and the first pin root 42 is spaced from the first box crest 43. This further facilitates the flow of fluid-like dirt out of the threaded connection 1.

[0097] The figures 9A and 9B show an enlarged view of part of the first pin thread 5 and the first box thread 11 and part of the second pin thread 7 and the second box thread 13. respectively, during a fifth stage of the rotational make-up of the threaded connection 1 of figure 1 A.

[0098] In said fifth stage, the rotational make-up of the threaded connection 1 is continued and the intermediate pin sealing surface 46 has been placed in contact with the intermediate box sealing surface 47. Subsequently, the first pin crest 41 is placed in contact with the first box root 44 and the first pin root 42 is placed in contact with the first box crest 43.

[0099] In other embodiments of the threaded connection 1 of figure 1A, the intermediate pin sealing surface 46 is placed in contact with the intermediate box sealing surface 47 after the first pin crest 41 has been placed in contact with the first box root 44 and the first pin root 42 has been placed in contact with the first box crest 43.

[0100] It is also possible that the second pin crest 37 is placed in contact with the second box root 40 and the second pin root 38 is placed in contact with the second box crest 39 after the first pin crest 41 has been placed in contact with the first box root 44 and the first pin root 42 has been placed in contact with the first box crest 43.

[0101] The figures 10A and 10B show an enlarged view of part of the first pin thread 5 and the first box thread 11 and part of the second pin thread 7 and the second box thread 13, respectively, during a sixth stage of the rotational make-up of the threaded connection 1 of figure 1 A.

[0102] In said sixth stage, the rotational make-up of the threaded connection 1 is continued and the first pin stab flank 21 is placed in contact with the first box stab flank 25. In addition, the second pin stab flank 23 is placed in contact with the second box stab flank 27 and the second pin load flank 24 is placed in contact with the second box load flank 28. The first pin / box stab flanks 21, 25 are placed in contact at the same time that the second pin / box stab flanks 23, 27 and the second pin / box load flanks 24, 28 are placed in contact. In other embodiments of the threaded connection 1 of figure 1A, the first pin I box stab flanks 21, 25 are placed in contact before or after the second pin / box stab flanks 23, 27 and the second pin / box load flanks 24, 28 are placed in contact.

[0103] The rotational make-up of the threaded connection 1 is subsequently continued to create thread interference between the first pin thread 5 and the first box thread 11 and between the second pin thread 7 and the second box thread 13 and is stopped when final make-up 17 is reached.

[0104] As required, detailed embodiments of the present invention are disclosed in the figures; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which can be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure.

[0105] The terms "a" or "an", as used herein, are defined as one or more than one. The terms multiple and plurality, as used herein, are defined as two or more than two. The term another, as used herein, is defined as at least a second or more. The terms including and / or having, as used herein, are defined as comprising (i.e., open language, not excluding other elements or steps). Any reference signs in the claims should not be construed as limiting the scope of the claims or the invention.

[0106] It will be apparent to those skilled in the art that various modifications can be made to said threaded connection 1 and said method as show n in the figures without departing from the scope as defined in the claims.

Claims

CLAIMS1. Threaded connection for exploration and production of a hy drocarbon well, said threaded connection comprising:- a pin having a two-step pin thread comprising a large diameter pin thread step having a first pin thread and a small diameter pin thread step having a second pin thread, and- a box having a two-step box thread comprising a large diameter box thread step having a first box thread and a small diameter box thread step having a second box thread, wherein - the pin and the box extend along a longitudinal axis,- the first pin thread and the first box thread are varying-thread-width threads which cooperate with each other during rotational make-up of the threaded connection to create thread interference between the first pin thread and the first box thread at final make-up of the threaded connection,- the second pin thread and the second box thread are vary ing-thread-width threads which cooperate with each other during rotational make-up of the threaded connection to create thread interference between the second pin thread and the second box thread at said final make-up of the threaded connection,- the pin comprises an external pin sealing surface,- the box comprises an external box sealing surface,- the external pin sealing surface and the external box sealing surface are configured to cooperate with each other during said rotational make-up to form an external radial metal -to-metal seal at said final make-up of the threaded connection, - the first pin thread comprises a first pin stab flank and a first pin load flank, - the second pin thread comprises a second pin stab flank and a second pin load flank,- the first box thread comprises a first box stab flank and a first box load flank, - the second box thread comprises a second box stab flank and a second box load flank,- the first pin thread and the first box thread are configured to have contact between at least part of the first pin stab flank and at least part of the first box stab flank upon stabbing of the pin into the box,- the second pin thread and the second box thread are configured to have the second pin stab flank spaced from the second box stab flank and have the second pin load flank spaced from the second box load flank upon said stabbing of the pin into the box, and— the pin and the box are configured to, during said rotational make-up of the threaded connection force the external pin sealing surface against the external box sealing surface and thereby move the first pin stab flank and the first box stab flank away from each other and place at least part of the first pin load flank in contact with at least part of the first box load flank, while the second pin stab flank remains spaced from the second box stab flank and the second pin load flank remains spaced from the second box load flank.

2. Threaded connection according to claim 1, wherein:- the pin comprises an internal pin sealing surface,- the box comprises an internal box sealing surface,- the internal pin sealing surface and the internal box sealing surface are configured to cooperate with each other during said rotational make-up to form an internal radial metal-to-metal seal at said final make-up of the threaded connection, and- the pin and the box are configured to, during said rotational make-up of the threaded connection, place the internal pin sealing surface in contact with the internal box sealing surface after said placing in contact of at least part of the first pin load flank with at least part of the first box load flank.

3. Threaded connection according to claim 2, wherein:- the second pin thread comprises a second pin crest and a second pin root.- the second box thread comprises a second box crest and a second box root,- the second pin thread and the second box thread are configured to have crest-root interference between the second pin thread and the second box thread at said final makeup of the threaded connection, and- the pin and the box are configured to. during said rotational make-up of the threaded connection, place the second pin crest in contact with the second box root and / or place the second pin root in contact with the second box crest after said placing in contact of the internal pin sealing surface with the internal box sealing surface.

4. Threaded connection according to any one of the preceding claims, wherein:- the first pin thread comprises a first pin crest and a first pin root,- the first box thread comprises a first box crest and a first box root,- the first pin thread and the first box thread are configured to have crest-root interference between the first pin thread and the first box thread at said final make-up of the threaded connection,- the pin comprises an intermediate pin sealing surface,- the box comprises an intermediate box sealing surface,- the intermediate pm sealing surface and the intermediate box sealing surface are configured to cooperate with each other during said rotational make-up to form an intermediate radial metal-to-metal seal at said final make-up of the threaded connection, and either:- the pin and the box are configured to, during said rotational make-up of the threaded connection, place the intermediate pin sealing surface in contact with the intermediate box sealing surface after said placing in contact of the first pin crest with the first box root and / or said placing in contact of the second pm root with the second box crest, OR - the pin and the box are configured to, during said rotational make-up of the threaded connection, place the first pin crest in contact with the first box root and / or place the first pin root in contact with the first box crest after said placing in contact of the intermediate pin sealing surface with the intermediate box sealing surface.

5. Threaded connection according to claim 4 in combination with claim 3, wherein the pin and the box are configured to, during said rotational make-up of the threaded connection, place the first pin crest in contact with the first box root and / or place the first pin root in contact with the first box crest after said placing in contact of the second pin crest with the second box root and / or said placing in contact of the second pin root with the second box crest.

6. Threaded connection according to claim 4 or 5. wherein the pin and the box are configured to, during said rotational make-up of the threaded connection, place the intermediate pin sealing surface in contact with the intermediate box sealing surface after said placing in contact of the second pin crest with the second box root and / or said placing in contact of the second pin root with the second box crest.

7. Threaded connection according to any one of the claims 4-6, wherein:- the pin and the box are configured to, during said rotational make-up of the threaded connection, place the first pin stab flank in contact with the first box stab flank after said placing in contact of the first pin crest with the first box root and / or said placing in contact of the first pin root with the first box crest.

8. Threaded connection according to any one of the claims 4-7, wherein:- the pin and the box are configured to, during said rotational make-up of the threaded connection, place the second pin stab flank in contact with the second box stab flank and place the second pin load flank in contact with the second box load flank after said placing in contact of the second pin crest with the second box root and / or said placing in contact of the second pin root with the second box crest.

9. Threaded connection according to any one of the preceding claims, wherein the first pin thread and the first box thread form a first set of cooperating dovetail threads, and the second pin thread and the second box thread form a second set of cooperating dovetail threads.

10. Threaded connection according to any one of the preceding claims, wherein the threaded connection is free from any final make-up stop shoulder defining a final make-up position for the pin relative to the box at said final make-up of the threaded connection.

11. Threaded connection according to any one of the preceding claims, wherein- the pin comprises a pin terminal end and an unthreaded pin base section,- the two-step pin thread is located between the pin terminal end and the unthreaded pin base section,- the box comprises a box terminal end and an unthreaded box base section,- the two-step box thread is located between the box terminal end and the unthreaded box base section,- the external pin sealing surface is located between the unthreaded pin base section and the first pin thread, and- the external box sealing surface is located between the box terminal end and the first box thread.

12. Threaded connection according to claim 11 and in combination with claim 2, wherein:- the internal pin sealing surface is located between the second pin thread and the pin terminal surface, and- the internal box sealing surface is located between the unthreaded box base section and the second box thread.

13. Threaded connection according to claim 11 or 12 and in combination with claim 4, wherein:- the intermediate pin sealing surface is located between the first pin thread and the second pin thread, and- the intermediate box sealing surface is located between the first box thread and the second box thread.

14. A method of making up the threaded connection of claim 1, the method comprising the steps of:- placing at least part of the first pin stab flank in contact with at least part of the first box stab flank upon stabbing of the pin into the box and before rotational make-up of thethreaded connection is started, while having the second pin stab flank spaced from the second box stab flank and the second pin load flank spaced from the second box load flank upon said stabbing of the pin into the box, and- forcing the external pin sealing surface against the external box sealing surface, during the rotational make-up of the threaded connection, and thereby moving the first pin stab flank and the first box stab flank away from each other and placing at least part of the first pin load flank in contact with at least part of the first box load flank, while the second pin stab flank remains spaced from the second box stab flank and the second pin load flank remains spaced from the second box load flank.

Images