Threaded connection for exploration and production of a hydrocarbon well

Abstract

A threaded connection comprising 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.

Description

THREADED CONNECTION FOR EXPLORATION AND PRODUCTION OF A HYDROCARBON WELLFIELD 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.

[0005] The threaded connection is free from a final make-up stop shoulder, such as a cylindrical final make-up stop shoulder or a helical 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. This makes the rotational make-up of the threaded connection “indeterminate” and, as a result, the position of the pin relative to the box may vary more during make-up for a given torque range to be appliedthan 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.

[0006] In addition, threaded connections with a final make-up stop shoulder typically 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 is in practice determined by the dimensions of the hydrocarbon well. Since a final make-up stop shoulder requires space in radial direction, there is less space available for the inner diameter of the threaded connection forming the channel through which the hydrocarbon fluid flows. A smaller inner diameter results in a smaller channel and therefore a smaller production capacity.BACKGROUND OF THE INVENTION

[0007] The make-up of this type 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 threaded connection 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

[0008] 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

[0009] 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 comprising 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 comprising 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 second box thread at final make-up of the threaded connection, 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 makeup of the threaded connection, the first pin thread comprises a first pin stab flank, the second pin thread comprises a second pin stab flank, the first box thread comprises a first box stab flank, the second box thread comprises a second box stab 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, and the second pin thread and the second box thread are configured to have the second pin stab flank and the second box stab flank spaced from each other upon said stabbing of the pin into the box.

[0010] 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.

[0011] 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.

[0012] 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.

[0013] 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.

[0014] Upon said stabbing of the pin into the box, the second pin stab flank and the second box stab flank are spaced from each other in axial direction with respect to the longitudinal axis of the threaded connection.

[0015] Due to the fact that the stab flanks of the first pin thread and the first box thread (forming the large diameter pin / box thread step) have contact upon stabbing of the threaded connection and the stab flanks of the second pin thread and the second box thread (forming the small diameter pin / box thread step) are spaced from each other, the forces created between the pin and the box having contact with each other upon stabbing are absorbed by the first pin stab flank and the first box stab flank and transferred through the pin and the box via the first pin thread and the first box thread. Since the first pin thread and the first box thread are located at the large diameter pin / box thread step, said forces are absorbed and transferred over a relatively larger surface area when compared with the small diameter pin / box thread step. This leads to lower stresses in the first pin thread and the first box thread and therefore a lower risk to damage the first pin thread and the first box thread. The term relatively larger surface area relates to the fact that the stab flanks of one turn of the first pin thread and the first box thread located at the large diameter pin / box thread step have a larger surface area when compared with the stab flanks of one turn of the second pin thread and the second box thread located at the small diameter pin / box thread step.

[0016] Furthermore, the stabbing of the threaded connection is controlled by first pin thread and the first box thread of the large diameter pin / box thread step having contact upon said stabbing of the pin into the box. This has the advantage that since the large diameter pin / box thread step is designed to control the stabbing, the design of the second pin thread and the second box thread ofthe small diameter pin / box thread step can be dedicated to control other aspects, such as compression and tension resistance of the threaded connection. This is made possible by ensuring that no forces created by the pin and the box having contact with each other upon stabbing are absorbed and transferred by the second pin thread and second box thread.

[0017] In addition, since the stabbing of the threaded connection is controlled by the large diameter pin / box thread step, deviation of the small diameter pin / box thread step with respect to the large diameter pin / box thread step does not form a risk, or at least a reduced risk, to misalignment of the threaded connection during make-up.

[0018] 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.

[0019] In an embodiment of the threaded connection according to the invention, the first pin thread and the first box threads are configured to control said stabbing of the pin into the box and the second pin thread and the second box threads are not configured to control said stabbing of the pin into the box.

[0020] In an embodiment of the threaded connection according to the invention, the first pin thread comprises a first pin load flank, the second pin thread comprises a second pin load flank, the first box thread comprises a first box load flank, the second box threads comprises a second box load flank, 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 pin into the box, and 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.

[0021] In an embodiment of the threaded connection according to the invention, the second pin thread and the second box thread are configured to not overlap in axial direction with respect to the longitudinal axis of the threaded connection upon said stabbing of the pin into the box. This reduces the risk that the second pin thread and the second box thread are damaged during make-up by undesired contact between the second pin thread and the second box thread upon stabbing the pin into the box.

[0022] In an embodiment of the threaded connection according to the invention, the second pin thread and the second box thread are located at a distance di from each other in axial direction with respect to the longitudinal axis of the threaded connection upon said stabbing of the pin into the box.

[0023] In an embodiment of the threaded connection according to the invention, the second pin thread and the second box thread are configured to have no overlap between the small diameter pin thread step and the small diameter box thread step in axial direction with respect to the longitudinal axis of the threaded connection upon said stabbing of the pin into the box.

[0024] In an embodiment of the threaded connection according to the invention, at least part of the first pin stab flank comprises a beveled first pin stab surface, at least part of the first box stab flank comprises a beveled first box stab surface, and the first pin thread and the first box thread are configured to have contact between the beveled first pin stab surface and the beveled first box stab surface upon said stabbing of the pin into the box.

[0025] The beveled first pin stab surface and the beveled first box stab surface facilitate that the first pin thread and the first box thread absorb and transfer the forces created upon said stabbing of the pin in the box. In addition, the beveled first pin stab surface and the beveled first box stab surface improve the alignment of the pin and the box.

[0026] In an embodiment of the threaded connection according to the invention, the beveled first pin stab surface is located at a first pin starting section of the first pin thread and the beveled first box stab surface is located at a first box starting section of the first box thread.

[0027] In an embodiment of the threaded connection according to the invention, the first pin starting section of the first pin thread extends from a first pin thread starting position until, and including, 0,5 and 2 thread turns of the first pin thread, and the first box starting section of the first box thread extends from a first box thread starting position until, and including, 0,5 and 2 thread turns of the first box thread.

[0028] In an embodiment of the threaded connection according to the invention, the first pin thread comprises a first pin crest and a first pin root, the beveled first pin stab surface extends from the first pin crest until the first pin root, the first box thread comprises a first box crest and a first box root, and the beveled first box stab surface extends from the first box crest until the first box root.

[0029] In an embodiment of the threaded connection according to the invention, the beveled first pin stab surface has a positive pin flank angle and the beveled first box stab surface has a positive box flank angle.

[0030] In an embodiment of the threaded connection according to the invention, the second pin stab flank is free from a beveled second pin stab surface and the second box stab flank is free from a beveled second box stab surface.

[0031] In an embodiment of the threaded connection according to the invention, at least part of the second pin stab flank comprises a beveled second pin stab surface, and at least part of the second box stab flank comprises a beveled second box stab surface.

[0032] In an embodiment of the threaded connection according to the invention, 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.

[0033] In an embodiment of the threaded connection according to the invention, the first pin thread is positioned along a first pin taper angle, the second pin thread is positioned along a second pin taper angle being smaller than the first pin taper angle, the first box thread is positioned along a first box taper angle, and the second box thread is positioned along a second box taper angle being smaller than the first box taper angle.

[0034] As a result, the large diameter pin / box thread step has a greater taper angle when compared with the small diameter pin / box thread step. This allows a deeper stabbing of the pin into the box, which improves the alignment of the pin and the box. In addition, a greater taper angle allows contact along a larger surface area between the first pin thread and the first box thread upon said stabbing of the pin in the box. Furthermore, the amount of turns of rotational make-up required from said stabbing until final make-up can be reduced.

[0035] A lower taper angle of the small diameter pin / box thread step allows that a larger box wall thickness is applied in the region between the large diameter pin / box thread step and the small diameter pin / box thread step. Said larger box wall thickness can be used in advantage for a specific function, such as a radial metal-to-metal seal. Said larger box wall thickness can be used to obtain a more robust radial metal-to-metal seal.

[0036] Each of the first pin taper angle, the second pin taper angle, the first box taper angle, and the second box taper angle is measured with respect the longitudinal axis. Each of the first pin taper angle, the second pin taper angle, the first box taper angle, and the second box taper angle is an acute angle.

[0037] In an embodiment of the threaded connection according to the invention, the first pin thread comprises a first pin pitch line which extends under the first pin taper angle relative to the longitudinal axis, the second pin thread comprises a second pin pitch line which extends under the second pin taper angle relative to the longitudinal axis, the first box thread comprises a first box pitch line which extends under the first box taper angle relative to the longitudinal axis, and the second box thread comprises a second box pitch line which extends under the second box taper angle relative to the longitudinal axis.

[0038] In an embodiment of the threaded connection according to the invention, the first pin taper angle and the first box taper angle are between, and including, 1,5 degrees and 3,5 degrees with respect to the longitudinal axis of the threaded connection, and the second pin taper angle and the second box taper angle are between, and including, 0,5 degrees and 2,5 degrees with respect to the longitudinal axis of the threaded connection.

[0039] In an embodiment of the threaded connection according to the invention, the first pin taper angle is between, and including, 1,5 times and 2,5 times the second pin taper angle, and the first box taper angle is between, and including, 1,5 times and 2,5 times the second box taper angle.

[0040] In an embodiment of the threaded connection according to the invention, the first pin taper angle is equal to the first box taper angle and the second pin taper angle is equal to the second box taper angle.

[0041] In an embodiment of the threaded connection according to the invention, the first pin thread comprises a first pin number of thread turns, the second pin thread comprises a second pin number of thread turns being smaller than said first pin number of thread turns, the first box thread comprises a first box number of thread turns, and the second box thread comprises a second box number of thread turns being smaller than said first box number of thread turns.

[0042] In an embodiment of the threaded connection according to the invention, the first pin number is between, and including, 5 thread turns and 10 thread turns, the second pin number is between, and including, 2 thread turns and 5 thread turns, the first box number is between, and including, 5 thread turns and 10 thread turns, and the second box number is between, and including, 2 thread turns and 5 thread turns.

[0043] In an embodiment of the threaded connection according to the invention, the first pin number of thread turns is between, and including, 1,5 times and 3,5 times the second pin number of thread turns, and the first box number of thread turns is between, and including, 1,5 times and 3,5 times the second box number of thread turns.

[0044] In an embodiment of the threaded connection according to the invention, the pin comprises a pin sealing surface located between the large diameter pin thread step and the small diameter pin thread step, the box comprises a box sealing surface located between the large diameter box thread step and the small diameter box thread step, and the pin sealing surface and the box sealing surface are configured to cooperate with each other during said rotational make-up to form a radial metal- to-metal seal at said final make-up of the threaded connection.

[0045] In an embodiment of the threaded connection according to the invention, the pin sealing surface is in axial direction along the longitudinal axis of the threaded connection located between the large diameter pin thread step and the small diameter pin thread step, and the box sealing surface is in axial direction along the longitudinal axis of the threaded connection located between the large diameter box thread step and the small diameter box thread step.

[0046] In an embodiment of the threaded connection according to the invention, the pin comprises a further pin sealing surface, the box comprises a further box sealing surface, and the further pinsealing surface and the further box sealing surface are configured to cooperate with each to form a further radial metal -to-metal seal.

[0047] In an embodiment of the threaded connection according to the invention, the first pin thread and the first box thread are configured to create flank interference in axial direction with respect to the longitudinal axis at final make-up of the threaded connection, and the second pin thread and the second box thread are configured to create flank interference in axial direction with respect to the longitudinal axis at final make-up of the threaded connection.

[0048] In an embodiment of the threaded connection according to the invention, the first pin thread and the first box thread are configured to create flank interference between the first pin stab flank and the first box stab flank and / or between the first pin load flank and the first box load flank at final make-up of the threaded connection, and the second pin thread and the second box thread are configured to create flank interference between the second pin stab flank and the second box stab flank and / or between the second pin load flank and the second box load flank at final make-up of the threaded connection.

[0049] In an embodiment of the threaded connection according to the invention, the first pin thread and the first box thread are configured to create crest-root interference in radial direction with respect to the longitudinal axis at final make-up of the threaded connection, and the second pin thread and the second box thread are configured to create crest-root interference in radial direction with respect to the longitudinal axis at final make-up of the threaded connection.

[0050] In an embodiment of the threaded connection according to the invention, the pin comprises a pin terminal end, the first pin thread comprises a first pin thread width which increases in axial direction with respect to the longitudinal axis of the threaded connection and away from the pin terminal end, the second pin thread comprises a second pin thread width which increases in axial direction with respect to the longitudinal axis of the threaded connection and away from the pin terminal end, the box comprises a box terminal end, the first box thread comprises a first box thread width which increases in axial direction with respect to the longitudinal axis of the threaded connection and away from the box terminal end, and the second box thread comprises a secondbox thread width which increases in axial direction with respect to the longitudinal axis of the threaded connection and away from the box terminal end.

[0051] It will be clear to the skilled person that the threaded connection according to the invention may comprise the features of any combination of the above described embodiments of the threaded connection according to the invention.

[0052] The invention further relates to a method of making up a threaded connection according to the invention, comprising the step 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.BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Embodiments of the threaded connection and the method according to the invention will be described by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, and in which:

[0054] Figure 1A schematically shows a cross sectional view along the longitudinal axis of one side of an embodiment of the threaded connection according to the invention at final make-up,

[0055] Figure IB schematically shows a cross sectional view along the longitudinal axis of the complete threaded connection of figure 1A,

[0056] Figure 2A schematically shows a cross sectional view along the longitudinal axis of the box of the threaded connection of figure 1A,

[0057] Figure 2B schematically shows an enlarge view of section II-B of figure 2A,

[0058] Figure 2C schematically shows an enlarge view of section II-C of figure 2 A,

[0059] Figure 3A schematically shows a cross sectional view along the longitudinal axis of the pin of the threaded connection of figure 1A,

[0060] Figure 3B schematically shows an enlarge view of section III-B of figure 3A,

[0061] Figure 3C schematically shows an enlarge view of section III-C of figure 3A, and

[0062] 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.DETAILED DESCRIPTION OF THE DRAWINGS

[0063] 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 16. The threaded connection 1 is configured for the exploration and production of a hydrocarbon well.

[0064] The threaded connection 1 comprises a pin 2 and a box 8 extending along a longitudinal axis 14. The axial direction 24 and the radial direction 25 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.

[0065] 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.

[0066] The first pin thread 5 and the first box thread 11 are vary ing-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 make-up 16 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 16 of the threaded connection 1.

[0067] The first pin thread 5 comprises a first pin stab flank 18 and a first pin load flank 26. The second pin thread 7 comprises a second pin stab flank 19 and a second pin load flank 27. The first box thread 11 comprises a first box stab flank 20 and first box load flank 28. The second box thread 13 comprises a second box stab flank 21 and second box load flank 29.

[0068] The first pin thread 5 and the first box thread 11 are configured to create flank interference in axial direction 24 with respect to the longitudinal axis 14 at final make-up 16 of the threaded connection 1. The second pin thread 7 and the second box thread 13 are configured to create flankinterference in axial direction 24 with respect to the longitudinal axis 14 at final make-up 16 of the threaded connection 1.

[0069] 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 18 and the first box stab flank 20 and / or between the first pin load flank 26 and the first box load flank 28 at final make-up 16 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 19 and the second box stab flank 21 and / or between the second pin load flank 27 and the second box load flank 29 at final make-up 16 of the threaded connection 1.

[0070] The first pin thread 5 and the first box thread 11 may be configured to create crest-root interference in radial direction 25 with respect to the longitudinal axis 14 at final make-up 16 of the threaded connection 1. The second pin thread 7 and the second box thread 13 may be configured to create crest-root interference in radial direction 25 with respect to the longitudinal axis 14 at final make-up 16 of the threaded connection 1.

[0071] 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 16 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.

[0072] 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 23 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 24 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 16 of the threaded connection 1 has been reached. During said rotational make-up of the threaded connection 1, thepin 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 24 as result of the rotational make-up. The term final makeup 16 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, the pin 2 and the box 8 do not move relative to each other.

[0073] Figure 4 shows a cross sectional view along the longitudinal axis 14 of the threaded connection 1 of figure 1 A 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 stab flank18 and at least part of the first box stab flank 20 upon said 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 flank19 and the second box stab flank 21 spaced from each other in axial direction 24 with respect to the longitudinal axis 14 upon said stabbing of the pin 2 into the box 8.

[0074] Said stabbing of the pin 2 into the box 8 relates to the situation that a final stabbing position 23 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 23 is reached before the rotational make-up of the threaded connection 1 is started.

[0075] Due to the fact that the stab flanks 18, 20 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 19, 21 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 18 and the first box stab flank 20 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 leads 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 thread11 . The term relatively larger surface area relates to the fact that the stab flanks 18, 20 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 19, 21 of one turn of the second pin thread 7 and the second box thread 13 located at the small diameter pin / box thread step 6, 12.

[0076] 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 having contact 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 fully dedicated to control other aspects, such as compression and tension resistance of the threaded connection 1. This is made possible by ensuring that no forces created by the pin 2 and the box 8 having contact with each other upon stabbing are absorbed and transferred by the second pin thread 7 and second box thread 13.

[0077] In addition, 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 form a risk, or at least a reduced risk, to misalignment of the threaded connection 1 during make-up.

[0078] The first pin thread 5 and the first box thread 11 are configured to have the first pin load flank 26 and the first box load flank 28 spaced from each other upon said 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 load flank 27 and the second box load flank 29 spaced from each other upon said stabbing of the pin 2 into the box 8.

[0079] As depicted in figure 4, the second pin thread 7 and the second box thread 13 are configured to not overlap in axial direction 24 with respect to the longitudinal axis 14 of the threaded connection 1 upon said stabbing of the pin 2 into the box 8. The second pin thread 7 and the second box thread 13 are located at a distance di from each other in axial direction 24 with respect to the longitudinal axis 14 of the threaded connection 1 upon said stabbing of the pin 2 into the box 8.This reduces the risk that the second pin thread 7 and the second box thread 13 are damaged during make-up by undesired contact between the second pin thread 7 and the second box thread 13 upon stabbing the pin 2 into the box 8.

[0080] More specifically, the second pin thread 7 and the second box thread 13 are configured to have no overlap between the small diameter pin thread step 6 and the small diameter box thread step 12 in axial direction 24 with respect to the longitudinal axis 14 of the threaded connection 1 upon said stabbing of the pin 2 into the box 8.

[0081] The box 8 and the pin 2 are shown in more detail in the figure 2A-C and 3A-C. At least part of the first pin stab flank 18 comprises a beveled first pin stab surface 30. At least part of the first box stab flank 20 comprises a beveled first box stab surface 31. As can be seen in figure 4, the first pin thread 5 and the first box thread 11 are configured to have contact between the beveled first pin stab surface 30 and the beveled first box stab surface 31 upon said stabbing of the pin 2 into the box 8.

[0082] The beveled first pin stab surface 30 and the beveled first box stab surface 31 facilitate that the first pin thread 5 and the first box thread 11 absorb and transfer the forces created upon said stabbing of the pin 2 in the box 8. In addition, the beveled first pin stab surface 30 and the beveled first box stab surface 31 improve the alignment of the pin 2 and the box 8.

[0083] The beveled first pin stab surface 30 is located at a first pin starting section 32 of the first pin thread 5. The beveled first box stab surface 31 is located at a first box starting section 33 of the first box thread 11. The first pin starting section 32 of the first pin thread 5 may extends from a first pin thread starting position 34 until, and including, 0,5 and 2 thread turns of the first pin thread 5. The first box starting section 33 of the first box thread 11 may extend from a first box thread starting position 35 until, and including, 0,5 and 2 thread turns of the first box thread 11.

[0084] The first pin thread 5 comprises a first pin crest 36 and a first pin root 37. The beveled first pin stab surface 30 extends from the first pin crest 36 until the first pin root 37. The first box thread 11 comprises a first box crest 38 and a first box root 39. The beveled first box stab surface 31 extends from the first box crest 38 until the first box root 39. The beveled first pin stab surface 30 has a positive pin flank angle Oi. The beveled first box stab surface 31 has a positive box flankangle yi. A Active line 71 extending perpendicular to the longitudinal axis 14 has been added in the figures 2B and 3B in order to visualize said positive pin flank angle 9i and said positive box flank angle yi.

[0085] At least part of the second pin stab flank 19 comprises a beveled second pin stab surface 42. At least part of the second box stab flank 21 comprises a beveled second box stab surface 43. The beveled second pin stab surface 42 has a positive pin flank angle 02. The beveled second box stab surface 43 has a positive box flank angle y2. A Active line 71 extending perpendicular to the longitudinal axis 14 has been added in the figures 2C and 3C in order to visualize said positive pin flank angle 02 and said positive box flank angle y2.

[0086] In other examples of the threaded connection 1 according to the invention (not shown), the second pin stab flank 19 is free from a beveled second pin stab surface 42 and the second box stab flank 21 is free from a beveled second box stab surface 43.

[0087] The pin 2 comprises a pin terminal end 60. The first pin thread 5 comprises a first pin thread width 61 which increases in axial direction 24 with respect to the longitudinal axis 14 of the threaded connection 1 and away from the pin terminal end 60. The second pin thread 7 comprises a second pin thread width 62 which increases in axial direction 24 with respect to the longitudinal axis 14 of the threaded connection 1 and away from the pin terminal end 60.

[0088] The box 8 comprises a box terminal end 63. The first box thread 11 comprises a first box thread width 64 which increases in axial direction 24 with respect to the longitudinal axis 14 of the threaded connection 1 and away from the box terminal end 63. The second box thread 13 comprises a second box thread width 65 which increases in axial direction 24 with respect to the longitudinal axis 14 of the threaded connection 1 and away from the box terminal end 63.

[0089] The first pin thread 5 and the first box thread 11 form a first set of cooperating dovetail threads 44. The second pin thread 7 and the second box thread 13 form a second set of cooperating dovetail threads 45.

[0090] The first pin thread 5 is positioned along a first pin taper angle 0i. The second pin thread7 is positioned along a second pin taper angle 2 being smaller than the first pin taper angle 0i. Thefirst box thread 11 is positioned along a first box taper angle ai. The second box thread 13 is positioned along a second box taper angle 012 being smaller than the first box taper angle ai.

[0091] As a result, the large diameter pin / box thread step 4, 10 has a greater taper angle ai, Pi when compared with the small diameter pin / box thread step 6, 12. This allows a deeper stabbing of the pin 2 into the box 8, which improves the alignment of the pin 2 and the box 8. In addition, a greater taper allows contact along a larger surface area between the first pin thread 5 and the first box thread 11 upon said stabbing of the pin 2 in the box 8. Furthermore, the amount of turns of rotational make-up required from said stabbing until final make-up 16 can be reduced.

[0092] A lower taper angle 012, 2 of the small diameter pin / box thread step 6, 12 allows that a larger box wall thickness 54 is applied in the region between the large diameter pin / box thread step 4, 10 and the small diameter pin / box thread step 6, 12. Said larger box wall thickness 54 is in the shown threaded connection 1 used to obtain a more robust radial metal-to-metal seal 57.

[0093] Each of the first pin taper angle Pi, the second pin taper angle P2, the first box taper angle ai, and the second box taper angle 012 is measured with respect the longitudinal axis 14. Each of the first pin taper angle Pi, the second pin taper angle P2, the first box taper angle ai, and the second box taper angle 012 is an acute angle.

[0094] The first pin thread 5 comprises a first pin pitch line 50 which extends under the first pin taper angle Pi relative to the longitudinal axis 14. The second pin thread 7 comprises a second pin pitch line 51 which extends under the second pin taper angle P2 relative to the longitudinal axis 14. A fictive line 70 extending parallel to the longitudinal axis 14 has been added to the figures 3B-C in order to visualize the first pin taper angle Pi and the second pin taper angle P2.

[0095] The first box thread 11 comprises a first box pitch line 52 which extends under the first box taper angle ai relative to the longitudinal axis 14. The second box thread 13 comprises a second box pitch line 53 which extends under the second box taper angle 012 relative to the longitudinal axis 14. A fictive line 70 extending parallel to the longitudinal axis 14 has been added to the figures 2B-C in order to visualize the first box taper angle ai and the second box taper angle 012.

[0096] The first pin taper angle Pi and the first box taper angle ai may be between, and including, 1,5 degrees and 3,5 degrees with respect to the longitudinal axis 14 of the threaded connection 1. The second pin taper angle P2 and the second box taper angle ai may be between, and including, 0,5 degrees and 2,5 degrees with respect to the longitudinal axis 14 of the threaded connection 1. The first pin taper angle Pi is equal to the first box taper angle on and the second pin taper angle P2 is equal to the second box taper angle 012.

[0097] The first pin taper angle Pi may be between, and including, 1,5 times and 2,5 times the second pin taper angle P2. The first box taper angle on may be between, and including, 1,5 times and 2,5 times the second box taper angle 012.

[0098] The first pin thread 5 comprises a first pin number of thread turns. The second pin thread 7 comprises a second pin number of thread turns being smaller than said first pin number of thread turns. The first box thread 11 comprises a first box number of thread turns. The second box thread 13 comprises a second box number of thread turns being smaller than said first box number of thread turns.

[0099] The first pin number may be between, and including, 5 thread turns and 10 thread turns. The second pin number may be between, and including, 2 thread turns and 5 thread turns. The first box number may be between, and including, 5 thread turns and 10 thread turns. The second box number may be between, and including, 2 thread turns and 5 thread turns.

[0100] The first pin number of thread turns may be between, and including, 1,5 times and 3,5 times the second pin number of thread turns. The first box number of thread turns may be between, and including, 1,5 times and 3,5 times the second box number of thread turns.

[0101] The pin 2 comprises a pin sealing surface 55 located between the large diameter pin thread step 4 and the small diameter pin thread step 6. The box 8 comprises a box sealing surface 56 located between the large diameter box thread step 10 and the small diameter box thread step 12. The pin sealing surface 55 and the box sealing surface 56 are configured to cooperate with each other during said rotational make-up to form a radial metal-to-metal seal 57 at said final make-up 16 of the threaded connection 1.

[0102] The pin sealing surface 55 is in axial direction 24 along the longitudinal axis 14 of the threaded connection 1 located between the large diameter pin thread step 4 and the small diameter pin thread step 6. The box sealing surface 56 is in axial direction 24 along the longitudinal axis 14 of the threaded connection 1 located between the large diameter box thread step 10 and the small diameter box thread step 12.

[0103] The pin 2 comprises two further pin sealing surfaces 58A, 58B. The box 8 comprises two further box sealing surfaces 59A, 59B. The further pin sealing surfaces 58A, 58B and the further box sealing surfaces 59A, 59B are configured to cooperate with each to form two further radial metal-to-metal seals 66A, 66B.

[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 the threaded connection and method according to the invention as shown in the figures without departing from the scope as defined in the claims.

Claims

CLAIMS1. Threaded connection for exploration and production of a hydrocarbon well, said threaded connection comprising:— a pin comprising 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 comprising 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 vary ing-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 makeup of the threaded connection,— the threaded connection is free from a final make-up stop shoulder defining a final makeup position for the pin relative to the box at said final make-up of the threaded connection,— the first pin thread comprises a first pin stab flank,— the second pin thread comprises a second pin stab flank,— the first box thread comprises a first box stab flank,— the second box thread comprises a second box stab 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, and— the second pin thread and the second box thread are configured to have the second pin stab flank and the second box stab flank spaced from each other upon said stabbing of the pin into the box.

2. Threaded connection according to claim 1, wherein the first pin thread and the first box threads are configured to control said stabbing of the pin into the box and the second pin thread and the second box threads are not configured to control said stabbing of the pin into the box.

3. Threaded connection according to claim 1 or 2, wherein:- the first pin thread comprises a first pin load flank,- the second pin thread comprises a second pin load flank,- the first box thread comprises a first box load flank,- the second box threads comprises a second box load flank,- 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 pin into the box, and- 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.

4. Threaded connection according to any one of the preceding claims, wherein the second pin thread and the second box thread are configured to not overlap in axial direction with respect to the longitudinal axis of the threaded connection upon said stabbing of the pin into the box.

5. Threaded connection according to any one of the preceding claims, wherein:- at least part of the first pin stab flank comprises a beveled first pin stab surface,- at least part of the first box stab flank comprises a beveled first box stab surface, and- the first pin thread and the first box thread are configured to have contact between the beveled first pin stab surface and the beveled first box stab surface upon said stabbing of the pin into the box.

6. 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 thesecond pin thread and the second box thread form a second set of cooperating dovetail threads.

7. Threaded connection according to any one of the preceding claims, wherein:- the first pin thread is positioned along a first pin taper angle,- the second pin thread is positioned along a second pin taper angle being smaller than the first pin taper angle,- the first box thread is positioned along a first box taper angle, and- the second box thread is positioned along a second box taper angle being smaller than the first box taper angle.

8. Threaded connection according to claim 7, wherein:- the first pin taper angle and the first box taper angle are between, and including, 1,5 degrees and 3,5 degrees with respect to the longitudinal axis of the threaded connection, and- the second pin taper angle and the second box taper angle are between, and including, 0,5 degrees and 2,5 degrees with respect to the longitudinal axis of the threaded connection.

9. Threaded connection according to claim 7 or 8, wherein:- the first pin taper angle is between, and including, 1,5 times and 2,5 times the second pin taper angle, and- the first box taper angle is between, and including, 1,5 times and 2,5 times the second box taper angle.

10. Threaded connection according to any one of the preceding claims, wherein:- the first pin thread comprises a first pin number of thread turns,- the second pin thread comprises a second pin number of thread turns being smaller than said first pin number of thread turns,- the first box thread comprises a first box number of thread turns, and- the second box thread comprises a second box number of thread turns being smaller than said first box number of thread turns.11 . Threaded connection according to claim 10, wherein:- the first pin number is between, and including, 5 thread turns and 10 thread turns,- the second pin number is between, and including, 2 thread turns and 5 thread turns,- the first box number is between, and including, 5 thread turns and 10 thread turns, and- the second box number is between, and including, 2 thread turns and 5 thread turns.

12. Threaded connection according to claim 10 or 11, wherein:- the first pin number of thread turns is between, and including, 1,5 times and 3,5 times the second pin number of thread turns, and- the first box number of thread turns is between, and including, 1,5 times and 3,5 times the second box number of thread turns.

13. Threaded connection according to any one of the preceding claims, wherein:- the pin comprises a pin sealing surface located between the large diameter pin thread step and the small diameter pin thread step,- the box comprises a box sealing surface located between the large diameter box thread step and the small diameter box thread step, and- the pin sealing surface and the box sealing surface are configured to cooperate with each other during said rotational make-up to form a radial metal -to-metal seal at said final makeup of the threaded connection.

14. Threaded connection according to any one of the preceding claims, wherein:- the pin comprises a further pin sealing surface,- the box comprises a further box sealing surface, and- the further pin sealing surface and the further box sealing surface are configured to cooperate with each to form a further radial metal -to-metal seal.

15. Method of making up a threaded connection according to any of the preceding claims, comprising the step 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.

Images