Thread profile of threaded joint

Abstract

A thread profile for a pin and a box of a threaded joint for hydrocarbon well exploration and production, comprising at least one helically extending thread on the pin and at least one helically extending thread on the box. The thread has a stab flank having a stab flank height, a load flank having a load flank height, and a crest. The stab flank includes a stab flank impact surface abutting the stab flank to the crest. The stab flank impact surface has a first stab flank radius. The thread has: [Equation 1] JPEG2026507665000035.jpg11156 [Number 2] According to TIFF2026507665000036.tif10158, where SFR1 is the first stub flank radius, SFH is the stub flank height, and LFH is the load flank height.

Description

[Technical Field]

[0001] The present invention relates to a thread profile of a threaded joint for the exploration and production of hydrocarbon wells, the threaded joint comprising the thread profile, a pin and a box of the threaded joint, as well as a method of forming the threaded joint. [Background technology]

[0002] Threaded joints for hydrocarbon well exploration and production generally include a pin at the free end of a first tubular member and a box at the free end of a second tubular member, the pin including male tapered threads on its outer surface and the box including female tapered threads on its inner surface.

[0003] The male and female tapered threads extend helically along the outer surface of the pin of the first tubular member and the inner surface of the box of the second tubular member, respectively, where the male and female tapered threads correspond to each other to facilitate threaded engagement between the first and second tubular members.

[0004] To form (or fasten) a threaded joint, in the first stage of fastening, the pin is inserted (or pierced) into the box, and then in the second stage of fastening, the pin is rotated in the fastening direction relative to the box, where the male tapered thread engages with the female tapered thread.

[0005] From an operational standpoint, it is advantageous for the thread profile of a threaded joint to be arranged to allow for a deeper penetration of the pin into the box. This allows for a portion of the male thread to pass axially through a portion of the female thread before the second stage of tightening begins. The more threads that pass each other in the first stage of tightening, the fewer turns are required to reach the end of the second stage of tightening. Therefore, a deeper penetration can be used to reduce the time required to tighten the joint, thereby reducing operational costs.

[0006] It is known that deeper penetration is possible by providing the pin and box with relatively steep male and female tapered threads, respectively. However, this method of providing deeper penetration is disadvantageous because a steeper taper generally requires a tubular member with a greater wall thickness. Therefore, a steeper taper generally involves a compromise in the inner and / or outer diameter of the threaded joint.

[0007] Additionally, during the second stage of fastening, rotating the pin relative to the box to reach the final fastening position can damage the threads. This damage can occur, for example, if the first tubular member is not properly axially aligned with the second tubular member. In particular, misalignment of the first tubular member relative to the second tubular member can result in so-called "cross-threading" and / or the threaded portions can come into contact with each other, creating high contact pressures as the tubes rotate. The latter can result in wear of the threads.

[0008] Attempts have been made to reduce the risk of damage to the threads of the joint.

[0009] Patent Document 1 discloses a threaded joint for pipes that has misalignment resistance and high shoulder torque resistance. The threaded joint includes a pin and a box. The pin and the box include a contact surface having a threaded portion and a metal contact portion without threads. At least one of the contact surfaces has a specific surface roughness, a Zn-Ni alloy plating layer, a Cu-Sn-Zn alloy plating layer, and a solid lubricant. A coating layer is provided. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] U.S. Patent No. 2021364119 AA Summary of the Invention [Problem to be solved by the invention]

[0011] It is an object of the present invention to provide an improved, or at least alternative, thread profile suitable for threaded joints for hydrocarbon well exploration and production. In particular, it is an object of the present invention to provide a thread profile that may help reduce operating costs and reduce the risk of damage to the joint's threads. More particularly, it is an object of the present invention to provide a thread profile that allows for a relatively deep penetration while limiting the risk of wear. [Means for solving the problem]

[0012] This object is achieved in a first aspect of the present invention by means of a thread profile for a pin and a box of a threaded joint for the exploration and production of hydrocarbon wells, said profile comprising at least one helically extending thread of said pin and at least one helically extending thread of said box, said thread having a stab flank with a stab flank height, a load flank with a load flank height, and a crest, wherein: the stub flank includes a stub flank impact surface that abuts the stub flank at a crest, the stab flank impact surface has a first stab flank radius; - the thread is

[0013]

number

[0014]

number

[0015] Providing a thread profile for a threaded joint according to the invention allows the joint to function well in the first stage of make-up as well as in the second stage, in particular the invention allows for good penetration ability and also reduces the risk of damage to the threads of the joint, especially due to wear.

[0016] In particular, the lower load flank height than the stab flank height and the ratio of the first stab flank radius to the stab flank height of 20% to 40% enable the formation of a first contact angle at the stab flank collision surface in the first stage of tightening, where the pin is tilted as it moves axially relative to the box. This configuration helps to form a second contact angle at the stab flank collision surface in the second stage of tightening, where the rotational movement to tighten the threaded joint causes the stab flank collision surface to tilt in the radial and helical directions. In particular, with the present invention, the sliding distance (i.e., the distance the screws need to slide relative to each other from the start of the second stage to the final fastened position) is relatively short, and at the same time, the contact pressure may be evenly distributed over the entire stab flank impact surface. Therefore, the risk of wear on these surfaces may be reduced.

[0017] Additionally, it was the inventors' insight that the thread configuration of the present invention tends to axially align the pin with the box early, i.e., in the first stage of fastening, and the tubular members are likely to be axially aligned with each other before the second stage of fastening begins. Thus, the risk of cross-threading and / or high contact pressures may be further reduced.

[0018] Generally, a "tubular member" is a (substantially) cylindrical hollow body having a longitudinal axis. Typically, such tubular members are formed from steel. The tubular member includes a cylindrical wall having a wall thickness. The cylindrical wall defines an inner wall surface and an outer wall surface.

[0019] The tubular member includes a first pin or a first box at a first axial end thereof and a second pin or a second box at a second axial end opposite the first axial end. Often, the pin or box at the first axial end corresponds to the pin or box at the second axial end. In particular, the tubular member may include a pin at the first axial end and a corresponding box at the second axial end.

[0020] The pin includes an external thread that is disposed on an outer surface of the pin and that tapers to a smaller outer diameter toward the free end of the pin.

[0021] The box includes an internal thread that is provided on the inner surface of the box and that tapers to an increasing inner diameter toward the free end of the box.

[0022] The male tapered thread extends helically along the outer surface of the pin. The male tapered thread includes a male valley root, a male crest, a male load flank, and a male stub flank. The male valley root may have a straight surface. The male valley root extends along a male valley root taper angle relative to the longitudinal axis of the pin. The male valley root taper may have a single male valley root taper angle. Thus, the male valley root may extend along a (single or constant) conical male valley root generatrix. The male crest extends along a male crest taper angle relative to the longitudinal axis of the pin. The male crest taper may have a single male crest taper angle. Thus, the male crest may extend along a (single or constant) conical male crest generatrix. In particular, the conical male valley root generatrix and the conical male crest generatrix may extend in the same direction or parallel to each other. The conical male valley bottom generatrix is ​​closer to the longitudinal axis of the pin than the conical male peak generatrix.

[0023] The male stub flank faces the free end of the pin. The male load flank faces away from the free end of the pin.

[0024] The female tapered thread extends helically along the inner surface of the box. The female tapered thread includes a female root, a female crest, a female load flank, and a female stab flank. The female root may have a straight surface. The female root extends along a female root taper angle relative to the longitudinal axis of the box. The female root taper may have a single female root taper angle. Thus, the female root may extend along a (single or constant) conical female root generatrix. The female crest extends along a female crest taper angle relative to the longitudinal axis of the box. The female crest taper may have a single female crest taper angle. Thus, the female crest may extend along a (single or constant) conical female crest generatrix. In particular, the conical female root generatrix The conical female crest generatrix and the conical female peak generatrix may extend in the same direction or parallel to each other. The conical female valley generatrix is ​​further from the longitudinal axis of the box than the conical female peak generatrix.

[0025] The point forming the root generating surface may be taken for each thread at the root, at the midpoint of the axial distance between the opposing load and stub flanks. The point forming the crest generating surface may be taken for each thread at the crest, at the midpoint of the axial distance between the load flanks facing opposite the stub flank.

[0026] The female stub flank faces the free end of the box, and the female load flank faces away from the free end of the box.

[0027] The male tapered threads of the pin and the female tapered threads of the box each include a plurality of threads.

[0028] The thread profile of the present invention includes at least one thread on the pin and at least one (corresponding) thread on the box. According to convention in the art, a "thread" may refer to one turn of the thread extending 360 degrees around the circumference of the pin or box. Thus, the thread profile of the present invention may include more than one (i.e., multiple) helically extending thread on the pin and more than one (i.e., multiple) helically extending thread on the box. Thus, the threads on the pin may together form a (first) helical length of the pin's thread, and the threads on the box may together form a (second) helical length of the box's thread. The helical length of the pin's thread may be a portion of the entire (uninterrupted) thread of the pin or may form the entire (uninterrupted) thread. Similarly, the helical length of the box's thread may be a portion of the entire (uninterrupted) thread of the box or may form the entire (uninterrupted) thread.

[0029] The helical length of the thread of the pin and, respectively, the box, may include multiple secondary threads. In such cases, the helically extending thread having a stab flank strike surface with a first stab flank radius is referred to as a "primary helically extending thread" or "primary thread." In this regard, it should be understood that the secondary thread may have different characteristics than the primary thread. In particular, the secondary thread may have a stab flank that does not have a stab flank strike surface and / or may have a stab flank radius that is different from the first stab flank radius of the primary thread.

[0030] "Matching helical threads" may mean threads on the box configured to collide with the helical threads on the pin during a first stage of fastening and to rotationally engage with the helical threads on the pin during a second stage of fastening.

[0031] The stub flank of the present invention includes a stub flank impact surface. In particular, the male stub flank may include a male stub flank impact surface, and the female stub flank may include a female stub flank impact surface.

[0032] The male stub flank may include a male stub flank impact surface, a central male stub flank surface, and an internal male stub flank surface. The male stub flank impact surface abuts (or connects) the central male stub flank surface to the male crest. The internal male stub flank surface abuts (or connects) the central male stub flank surface to the male valley root.

[0033] The female stub flank may include a female stub flank impact surface, a central female stub flank surface, and an interior female stub flank surface. The female stub flank impact surface abuts (or connects) the central female stub flank surface to the female crest. The interior female stub flank surface abuts (or connects) the central female stub flank surface to the female crest. The face abuts (or connects) to the female valley floor.

[0034] Both the male and female stab flank impact surfaces may have a convex cross-section with a first stab flank radius, particularly when viewed tangentially to the longitudinal axis of the pin and / or box. More particularly, the stab flank impact surfaces are convex in cross-section. "Convex cross-section" may mean that the flank surfaces are outwardly rounded in cross-section, e.g., like the outside of a circle. Conversely, the internal male and female stab flank surfaces may have a concave cross-section with a second stab flank radius, particularly when viewed tangentially to the longitudinal axis of the pin and / or box. More particularly, the internal stab flank surfaces are concave in cross-section. "Concave cross-section" may mean that the flank surfaces are inwardly rounded in cross-section, e.g., like the inside of a bowl.

[0035] The stub flank impact surface may describe a circular arc. In particular, the stub flank impact surface may describe a circular arc that starts at the central stub flank surface and terminates at a crest. Similarly, the internal stub flank surface may describe a circular arc. In particular, the internal stub flank surface may describe a circular arc that starts at the central stub flank surface and terminates at a root.

[0036] The central (male and / or female) stub flank surfaces may include a linear surface or may be straight, particularly when viewed tangentially to the longitudinal axis of the pin and / or box. More particularly, the central stab flank surface begins where the curved surface of the stab flank impact surface changes to a linear surface, and the central stab flank surface terminates where the stab flank changes from the linear surface of the central stab flank surface to the curved surface of the internal stab flank surface. The central male and female stab flank surfaces may extend at an angle of 2 to 9 degrees, particularly 5 degrees, relative to a plane perpendicular to the longitudinal axes of the pin and box, respectively. A relatively large central stab flank surface may provide improved compression resistance while maintaining the advantages associated with the first and second stages.

[0037] The stub flank has a (total) stub flank height. Thus, a male stub flank may have a (total) male stub flank height, and a female stub flank may have a (total) female stub flank height. The stub flank height is equal to the radial distance between the crest and root adjacent to the stub flank. The stub flank height may be measured closer to the stub flank than the load flank. In particular, the stub flank height may be defined by the stub flank impact surface, the central stub flank surface, and the inner stub flank surface.

[0038] The load flanks of the present invention may include an outer load flank surface, a central load flank surface, and an inner load flank surface. In particular, the male load flanks may include an outer male load flank surface, a central male load flank surface, and an inner male load flank surface, and the female load flanks may include an outer female load flank surface, a central female load flank surface, and an inner female load flank surface.

[0039] The outer male road flank surface abuts (or connects) the central male road flank surface to the male crest, and the inner male road flank surface abuts (or connects) the central male road flank surface to the male valley floor.

[0040] The outer female road flank surface abuts (or connects) the central female road flank surface to the female crest, and the inner female road flank surface abuts (or connects) the central female road flank surface to the female root.

[0041] Both the external male and external female load flanks are particularly suitable for use with pins and / or When viewed tangentially to the longitudinal axis of the box, the internal male and female load flank surfaces may have a convex cross-section with a first load flank radius, and conversely, the internal male and female load flank surfaces may have a concave cross-section with a second load flank radius, particularly when viewed tangentially to the longitudinal axis of the pin and / or box.

[0042] The central (male and / or female) load flank surfaces may include a linear surface or may be straight, particularly when viewed tangentially to the longitudinal axis of the pin and / or box. More particularly, the central load flank surface begins where the load flank changes from the curved surface of the outer load flank surface to a linear surface, and the central load flank surface terminates where the load flank changes from the linear surface of the inner load flank surface to a curved surface of the inner load flank surface. The central male and female load flank surfaces may extend at an angle of 2 to 9 degrees, particularly 5 degrees, relative to a plane perpendicular to the longitudinal axis of the pin and box, respectively. A relatively large central load flank surface may provide improved pull resistance while maintaining the advantages associated with the first and second stages.

[0043] A load flank has a (total) load flank height. Thus, a male load flank may have a (total) male load flank height, and a female load flank may have a (total) female load flank height. The load flank height is equal to the radial distance between the crest and root adjacent to the load flank. The load flank height may be measured closer to the load flank than the stub flank. In particular, the load flank height may be defined by an outer load flank surface, a central load flank surface, and an inner load flank surface.

[0044] The stab flank height and the load flank height may be constant along the axial direction. Thus, the stab flank height and the load flank height may have a single stab flank height and a single load flank height, respectively. For example, the stab flank height (or the load flank height) of the threads of the thread profile located near the free end of the pin or box may be the same as the stab flank height (or the load flank height) of the threads of the thread profile away from the free end of the pin or box.

[0045] The (first) longitudinal axes of the first tubular member, the pin, and the male tapered thread are the same. Similarly, the (second) longitudinal axes of the second tubular member, the box, and the female tapered thread are the same. The threads of the thread profile may extend helically around the first and / or second longitudinal axes. In particular, the threads of the pin may extend helically around the longitudinal axis of the pin, and the threads of the box may extend helically around the longitudinal axis of the box.

[0046] Within the context of the present disclosure, the term "radial" may mean perpendicular to the longitudinal axis. Thus, the term "radially" may mean a direction perpendicular to the longitudinal axis.

[0047] Within the context of the present disclosure, the term "axial" may mean along a longitudinal axis. Thus, the term "axially" may mean a direction along a longitudinal axis.

[0048] The parameters described in this disclosure (e.g., first stab flank radius, second stab flank radius, first contact angle, second contact angle, etc.) may be measured at a longitudinal cross section of a threaded joint.

[0049] Within the context of this disclosure, a thread profile according to the present invention refers to the (male / female) taper of a threaded joint. It may include one or more of the features described for the screw.

[0050] Embodiments according to the first, second, third, fourth and fifth aspects of the present invention are described below.

[0051] In one embodiment according to the first aspect of the invention, the stab flank impact surface is convex in cross section, particularly when viewed tangentially to the longitudinal axis, and in particular from the (substantially axially extending) linear surface of the crest to the (substantially) radially extending portion of the stab flank.

[0052] In one embodiment according to the first aspect of the present invention, the thread has no chamfered or beveled edges between the crest and the stab flank. In particular, the stab flank, and more particularly the stab flank impact surface, has no chamfered or beveled edges near the crest. Even more particularly, the male stub flank has no chamfered or beveled edges near the male crest, and the female stub flank has no chamfered or beveled edges near the female crest.

[0053] In one embodiment according to the first aspect of the present invention, the thread further comprises:

[0054]

number

[0055] In one embodiment according to the first aspect of the present invention, the thread further comprises:

[0056]

number

[0057] An advantage of the above embodiments according to equations (3) and / or (4) is that in the second stage of fastening, the risk of wear may be further reduced. In particular, there may be a lower maximum (or peak) contact pressure, which will be described in more detail below.

[0058] In one embodiment according to the first aspect of the invention, the stab flank impact surface has a (radial) stab flank impact height and the thread has

[0059]

number

[0060] In one embodiment according to the first aspect of the present invention, the thread further comprises:

[0061]

number

[0062] In one embodiment according to the first aspect of the present invention, the thread further comprises:

[0063]

number

[0064] In one embodiment according to the first aspect of the present invention, the thread further comprises:

[0065]

number

[0066] In one embodiment according to the first aspect of the present invention, the thread further comprises:

[0067]

number

[0068] In one embodiment according to the first aspect of the present invention, the thread further comprises:

[0069]

number

[0070] In one embodiment according to the first aspect of the present invention, the difference between the (male) first stab flank radius of the (male) stab flank collision surface of the at least one thread of the pin and the (female) first stab flank radius of the (female) stab flank collision surface of the at least one thread of the box is less than 10%.

[0071] In one embodiment according to the first aspect of the present invention, a (male) first stub flank radius of a (male) stub flank collision surface of at least one thread of the pin and a (female) first stub flank radius of a (female) stub flank collision surface of at least one thread of the box are equal to each other.

[0072] In one embodiment according to the first aspect of the present invention, the stab flank of the thread is a vertical stab flank (i.e., a stab flank extending substantially perpendicular to the longitudinal axis) or a negatively inclined stab flank. In particular, the stab flank may extend at a stab flank angle of (-)10 to 0 degrees. This stab flank angle is formed between the stab flank and a surface of the pin and / or box extending perpendicular to the longitudinal axis.

[0073] The present invention is particularly relevant to joints having thread profiles with vertical stab flanks, or more particularly, negative stab flanks. During impact in the first stages of make-up, these types of stab flanks tend to catch on each other rather than slip axially past each other, in contrast to threads utilizing positive stab flanks.

[0074] In one embodiment according to the first aspect of the invention, the load flanks of the threads are generally perpendicular or negative load flanks, particularly when viewed tangentially to the longitudinal axis of the pin and / or box. Specifically, the load flanks may extend at a load flank angle between (-)10 and 0 degrees. The load flank angle is formed between the load flank and a plane extending perpendicular to the longitudinal axis of the pin and / or box.

[0075] According to convention in the art, a negatively inclined flank is one that tends to increase the axial width of the crest of the thread compared to the base of the thread. When both the stab flank and the load flank are positively inclined, the thread has a narrower crest in cross section than the base. When the load flank is negatively inclined and the stab flank is positively inclined, the thread is a hook thread. When both the stab flank and the load flank are negatively inclined, the thread comprises a dovetail-shaped cross section.

[0076] In one embodiment according to the first aspect of the invention, the thread profile comprises a dovetail-shaped cross-section, particularly when viewed tangentially to the longitudinal axis of the pin and / or box.

[0077] In one embodiment according to the first aspect of the present invention, the at least one helically extending thread of the pin has an axial thread width that decreases axially toward the free end of the pin, and the at least one helically extending thread of the box has an axial thread width that decreases axially toward the free end of the box. In particular, the axial distance between the threads of the pin decreases axially from the free end of the pin toward the tubular member containing the pin, and the axial distance between the threads of the box decreases axially from the free end of the box toward the tubular member containing the box. More particularly, at the end of the second stage of fastening, the stub flanks contact each other and / or the load flanks contact each other, and a final fastened position is reached based on stub flank interference and load flank interference.

[0078] In such embodiments, the stab flank may bear a significant portion of the axial compressive load applied to the joint during hydrocarbon well exploration and production. As explained below, the inventors have found that the above embodiment works particularly well in combination with an embodiment having a thread profile according to equations (3) or (4) above. In addition to the advantages discussed above, threaded joints utilizing such thread profiles can have good resistance to axial compression regardless of the wall thickness of the tubular member.

[0079] In one embodiment according to the first aspect of the present invention, the thread has a root, the stab flank includes a stab flank inner surface, the stab flank inner surface having a concave cross section with a second stab flank radius, particularly when viewed tangentially to a longitudinal axis of the pin and / or box, and the thread further comprises:

[0080]

number

[0081] In one embodiment according to the first aspect of the present invention, the thread further comprises:

[0082]

number

[0083] Therefore, the first stub flank radius is equal to the second stub flank radius.

[0084] In one embodiment according to the first aspect of the present invention, the thread profile includes a plurality of helically extending threads on the pin and a plurality of helically extending threads on the box, wherein the plurality of helically extending threads on the pin are adjacent to one another and the plurality of helically extending threads on the box are adjacent to one another.

[0085] In one embodiment according to the first aspect of the present invention, the pin thread is a primary pin thread, the box thread is a primary box thread, the thread profile further comprises a plurality of secondary pin threads and a plurality of secondary box threads, the pin primary thread and the pin secondary threads together form the helical length of the pin thread, the box primary thread and the box secondary threads together form the helical length of the box thread, the pin primary thread is provided on at least 50%, particularly at least 80%, of the pin thread helical length, and the box primary thread is provided on at least 50%, particularly at least 80%, of the box thread helical length.

[0086] In the above aspect, the primary and secondary helically extending pin threads together form a (first) helical length of the pin thread, and the primary and secondary helically extending box threads together form a (second) helical length of the box thread. The primary threads of the pin may be adapted to rotationally engage with the primary threads of the box, and the secondary threads of the pin may be adapted to rotationally engage with the secondary threads of the box.

[0087] In one embodiment according to the first aspect of the present invention, the primary helical thread is located axially closer to the free end of the pin than the secondary helical thread. In particular, the primary helical thread starts near the free end of the pin and extends to the center (in the n-axis direction) of the pin thread. In this embodiment, the primary box thread may be located axially farther from the free end of the box than the secondary helical box thread. In particular, the primary box thread starts near the body side of the tubular member and extends to the center (in the n-axis direction) of the box thread.

[0088] In one embodiment according to the first aspect of the invention, the primary pin threads are adapted to impinge on the primary box threads and are free to impinge on the secondary threads.

[0089] In one embodiment according to the first aspect of the present invention, the secondary threads of the pin are configured to avoid collision with the primary threads of the box. Additionally, the secondary threads of the box may be configured to avoid collision with the primary threads of the pin.

[0090] In one embodiment according to the first aspect of the invention, the secondary threads of the pin are configured to avoid collision with the secondary threads of the box, particularly during the first stage of fastening.

[0091] For example, the secondary threads may have a lower stab flank height than the stab flank of the primary threads. In particular, the secondary threads of the box may have a lower stab flank height than the secondary threads of the pin.

[0092] In the above embodiments having both primary and secondary threads, the first stage of fastening may be controlled primarily by the primary threads, where the primary threads may help align the pin to the box and prevent cross-threading. Thus, only a small portion of the overall thread profile may include features that promote easy piercing. In this way, fewer machining steps may be required to produce the thread profile.

[0093] In one embodiment according to the first aspect of the present invention, the crests of the threads are parallel to the longitudinal axis. do.

[0094] In one embodiment according to the first aspect of the present invention, the roots of the threads are parallel to the longitudinal axis.

[0095] In a second aspect of the present invention, there is provided a threaded joint for hydrocarbon well exploration and production, the threaded joint comprising a pin and a box, the threaded joint comprising a thread profile according to the first aspect of the present invention. In particular, the threaded joint may have a thread profile according to any of the embodiments described with respect to the first aspect.

[0096] In a third aspect of the present invention, there is provided a pin of a threaded joint for hydrocarbon well exploration and production, the pin including at least one helically extending thread, the at least one thread having a stab flank having a stab flank height, a load flank having a load flank height, and a crest, wherein: the stub flank includes a stub flank impact surface that abuts the stub flank at a crest, the stab flank impact surface has a first stab flank radius; - the thread is

[0097]

number

[0098]

number

[0099] In a fourth aspect of the present invention, there is provided a box of a threaded joint for hydrocarbon well exploration and production, the box having at least one helically extending thread, the at least one thread having a stab flank having a stab flank height, a load flank having a load flank height, and a crest, wherein: the stub flank includes a stub flank impact surface that abuts the stub flank at a crest, the stab flank impact surface has a first stab flank radius; - the thread is

[0100]

number

[0101]

number

[0102] In a fifth aspect of the invention, there is provided a method of forming a threaded joint, the method comprising: - providing a pin and a box having a thread profile according to a first aspect; - inserting said pin into said box in a first fastening stage; - rotating the pin in a fastening direction relative to the box in a second fastening stage; Includes:

[0103] In one embodiment according to the fifth aspect of the invention, the step of rotating occurs after the step of inserting has reached a final insertion position, where the longitudinal axes of the pin and box are aligned and deeper penetration is no longer possible.

[0104] It will be apparent to one skilled in the art that the second, third, fourth and fifth aspects of the present disclosure may include features relating to the first aspect of the invention in any combination of the above-mentioned aspects of the first aspect of the invention.

[0105] For a better understanding of the present invention and to show how the same may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings in which: [Brief explanation of the drawings]

[0106] [Figure 1] 1 shows a schematic longitudinal cross-sectional view of a threaded joint according to the present disclosure; [Figure 2] 1 shows a cross-sectional view of the threads of a prior art threaded joint. [Figure 3] 1 shows a cross-sectional view of a thread profile of a threaded joint according to the present invention. [Figure 4A-4B] 1 provides a detailed view of the threads of a thread profile of a threaded joint according to the present invention; [Figure 5A] 1 shows a thread according to the present invention in which a first contact angle is formed. [Figure 5B] 1 shows a thread according to the present invention in which a second contact angle is formed. [Figure 6] 1 shows a graph illustrating contact pressures on threads of various samples during the first stage of make-up. [Figure 7] 10 shows a graph illustrating contact pressures on threads of various samples during the second stage of make-up. DETAILED DESCRIPTION OF THE INVENTION

[0107] 1 shows a longitudinal cross-section of a threaded joint 100 in a first stage of make-up. The threaded joint 100 includes a pin 1 and a box 2. The pin 1 is part of a first tubular member (not shown) and the box 2 is part of a second tubular member (not shown).

[0108] The threaded joint 100 includes thread profiles 11 , 21 including a male tapered thread 11 on an outer surface 101 of the pin 1 and a female tapered thread 21 on an inner surface 201 of the box 2 .

[0109] The male tapered thread 11 includes a plurality of male threads 14. The male tapered threads 14 spirally converge toward the free end 13 of the pin 1, where the outer diameter of the pin 1 decreases toward the free pin end 13 of the pin 1. The female tapered thread 21 includes a plurality of female threads 24. The female tapered threads 24 spirally diverge toward the free end 23 of the box 2, where the inner diameter of the box 2 increases toward the free end 23 of the box 2.

[0110] As can be seen from Figure 1, pin 1 has a first longitudinal axis 12 and box 2 has a second longitudinal axis 22. In Figure 1, pin 1 is thrust into box 2, where pin 1 is moved axially 3 relative to box 2. As shown in Figure 1, in the first stage of fastening, first and second longitudinal axes 12, 22 may be offset (i.e., misaligned) relative to one another.

[0111] The male tapered thread 11 includes a male valley root 16, a male crest 17, a male load flank 18, and a male stub flank 15. The male valley root 16 extends along a male valley root taper angle α1 relative to the longitudinal axis 12 of the pin 1. The male valley root taper has a single male valley root taper angle α1. Therefore, the male valley root 16 extends along a constant conical male valley root generatrix 161. The male crest 17 extends along a male crest taper angle that is equal to the male valley root taper angle α1. Therefore, the male crest also extends along a constant conical male crest generatrix (not shown). The conical male valley root generatrix 161 and the conical male crest generatrix extend in the same direction. The conical male valley root generatrix 161 is closer to the longitudinal axis 12 of the pin 1 than the conical male crest generatrix.

[0112] The female tapered thread 21 extends helically along the inner surface 201 of the box 2. The female tapered thread 21 includes a female root 26, a female crest 27, a female load flank 28, and a female stub flank 25. The female stub flank 25 corresponds to the male stub flank 15. The female root 26 extends along a single female root taper angle β1 relative to the longitudinal axis 22 of the box 2. Thus, the female root 26 extends along a constant conical female root generatrix 261. The female crest 27 extends along a female crest taper angle (not shown) that is equal to the female root taper angle β1. Thus, the female crest 27 also extends along a constant conical female crest generatrix. The conical female root generatrix 261 and the conical female crest generatrix extend parallel to each other. The conical female valley bottom generatrix 261 is located farther from the longitudinal axis 22 of the box 2 than the conical female peak generatrix.

[0113] The male crest 17 and the male valley root 16 are parallel to the longitudinal axis 11 of the pin 1. The female crest 27 and the female valley root 26 are parallel to the longitudinal axis 21 of the box 2.

[0114] The male stub flank 15 of each thread 14 faces toward the free end of the pin 13. The male load flank 25 faces away from the free end 13 of the pin 1. Similarly, the female stub flank 25 faces toward the free end 23 of the box 2. The female load flank 28 faces away from the free end 23 of the box 2.

[0115] The stub flanks 15, 25 include stub flank impact surfaces 151, 251, central stub flank surfaces 152, 252, and internal stub flank surfaces 153, 253. The stub flank impact surfaces 151, 251 have a rounded cross section with a first stub flank radius 1511, 2511, particularly when viewed tangentially to the longitudinal axis. The internal stub flank surfaces 153, 253 have a rounded cross section with a second stub flank radius 1531, 2531, particularly when viewed tangentially to the longitudinal axis. The stab flank impact surfaces 151, 251 are convex and arcuate. The internal stub flank surfaces 153, 253 are concave and arcuate. The first stub flank radius 1511, 2511 is the same as the second stub flank radius 1531, 2531.

[0116] The stub flanks 15, 25 have stub flank heights 154, 254. The load flanks 18, 28 have load flank heights 158, 258. The stub flank heights 154, 254 and the load flank heights 158, 258 are constant along the axial direction 3. The load flank heights 158, 258 are smaller than the stub flank heights 154, 254.

[0117] The stab flank impact surfaces 151, 251 have radial stab flank impact heights 159, 259. The stab flank impact height is equal to the difference between the stab flank height and the load flank height. The male stab flank impact surface 151 is adapted to contact the female stab flank impact surface 251 during the first stage of make-up.

[0118] The stub flank impact heights 159 and 259 are the heights between the stub flank impact surfaces 152 and 251. It should be noted that the stab flank impact height is related to the radial distance over which the impact may occur. The stab flank impact height is not necessarily the radial distance over which the entire stab flank impact surface extends. The stab flank impact surface may extend a radial distance greater than the stab flank impact height. In particular, the stab flank impact surface terminates where the stab flank surface no longer describes a circular arc and where the central stub flank surface begins, which describes a linear surface.

[0119] The tapered pin thread 11 and the tapered box thread 21 have dovetail-shaped cross sections. Specifically, the threads 14, 24 are wider in the axial direction 3 at the crests 17, 27 than at the roots 16, 26. More specifically, the threads 14, 24 are wider in the axial direction 3 at the stab flank strike surfaces 151, 251 than at the central stab flank surfaces 152, 252. Furthermore, the tapered pin thread 11 has an axial thread width that decreases in the axial direction 3 toward the free end 13 of the pin 1. The tapered internal thread 21 has a corresponding axial thread width that decreases in the opposite axial direction 6 toward the free end 23 of the box 2. Thus, the threaded joint 100 includes threads 11, 21 having varying widths in the axial direction 3. The axial spacing between the threads 14, 24 increases from the tubular member toward the free ends 13, 23 of the pin 1 and box 2, respectively. In particular, the screws 11, 21 have a load flank lead and a stab flank lead, and there is a difference between the load flank lead and the stab flank lead. In particular, the load flank lead may be greater than the stab flank lead. Both the load flank lead and the stab flank lead may be constant.

[0120] All threads 14, 24 have stab flank impact surfaces 151, 251 having the same first stab flank radius 1511, 2511. As can be seen from FIG. 1 , the threaded joint 100 is free of obstacles in the vicinity of the threads 11, 21. In particular, because the threads have varying axial widths, the threaded joint can be tightened in the second tightening stage based on the interference of the stab flanks 15, 25 and on the interference of the load flanks 18, 28, instead of requiring the box 2 to have a box stop shoulder (where the final tightening position of the joint is achieved by the intermediate shoulder of the pin or the free end 13 of the pin 1 contacting a corresponding stop shoulder on the box). In particular, the threaded joint 100 is free of a box stop shoulder that could impede the penetration of the pin 1 into the box 2 in the first tightening stage.

[0121] FIG. 2 shows a cross-sectional view of threads 14, 24 of a prior art threaded joint during the first stage of make-up. Threads 14, 24 include stab flanks 15, 25, crests 17, 27, and stab flank impact surfaces 151, 251 that abut crests 17, 27 against stab flanks 15, 25. Both stab flank impact surfaces 151, 251 have cross-sections with relatively small radii. As shown in FIG. 2 , the stab flanks contact each other, where male stub flank 15 is inclined to move radially relative to female stub flank 25, and male crest 17 is inclined to move toward female root 26. Additionally, FIG. 2 shows that as a result of contact between stab flanks 15, 25, forces are concentrated near the crests of threads 14, 24, and reaction forces are primarily directed in the axial direction 3. Therefore, to prevent damage to threads 11, 21, a relatively small portion of stab flanks 15, 25 must be positioned to sustain these forces.

[0122] Unlike FIG. 2, the thread profiles of FIGS. 3-5B include stab flank impact surfaces 151, 251 having arcuate cross sections with relatively large radii. In particular, the first stab flank radius 1511, 2511 is 0.46 mm. The first stab flank radius 1511 is selected to help the stab flanks 15, 25 easily pass each other in the axial direction 3 during the first stage of fastening, as shown in FIG. 5A, while at the same time ensuring that the male stub flank 15 does not overextend beyond the female stub flank 25 in the axial direction 3 during the second stage of fastening, as shown in FIG. 5B. Therefore, the sliding distance in the axial direction 6 and radial direction 7 over which the stab flanks 15, 25 slide relative to each other during the second stage of fastening is 0.46 mm. The distance is relatively short.

[0123] During the first stage of fastening, a first contact angle 4 is formed at the stab flank impact surfaces 151, 251. As shown in FIG. 5A, the first contact angle 4 is formed between line 9, which is tangent to the point where the stab flank impact surfaces 151, 251 impact, and line 8, which is in a plane perpendicular to the longitudinal axis 22. The first contact angle 4 is approximately 42 degrees. The first contact angle is established at the point where the greatest radial misalignment of the pin 1 with respect to the box 2 exists.

[0124] 3, 4A, and 5A, the longitudinal axis 12 of pin 1 is parallel to, but not coaxial with, the longitudinal axis 22 of box 2. Because threads 11, 21 are tapered (crowns 17, 27 extend along constant conical generatrices 161, 261) and stab flank heights 154, 254 are higher than load flank heights 158, 258, female crest 27 forms the radial boundary of male crest 17. In particular, crests 17, 27 extend parallel to longitudinal axes 12, 22, respectively.

[0125] At the start of the second stage of fastening, male stub flank 15 is positioned farther away within box 2 than corresponding female stub flank 25. Male stub flank 15 is sealed against female stub flank 25. A second contact angle 5 is now formed at stab flank collision surfaces 151, 251. In this case, longitudinal axes 12, 22 are coaxial. Second contact angle 5 is formed between line 9, which is tangent to the point where stab flank collision surfaces 151, 251 meet, and line 8. Second contact angle 5 is greater than first contact angle 4. In particular, second contact angle 5 is approximately 51 degrees.

[0126] The first contact angle and the second contact angle may be measured at a longitudinal cross-section of the fitting 100 .

[0127] 4A and 4B, contact pressure is generated primarily at the center of the stab flank impact surfaces 151, 251, with reaction forces extending primarily axially and radially through the threads 14, 24. In particular, the contact pressure is distributed evenly across the stab flank impact surfaces 151, 251. In particular, as a result of the contact between the impact surfaces 151, 251, the force is more evenly distributed through the threads 14, 24 than in the example shown in FIG.

[0128] Importantly, the first stab flank radius 2511 should be selected so that when the surfaces 151, 251 contact, the first contact angle 4 is not too large, as this may adversely affect the second contact angle 5, which may also become too large and increase the sliding distance in the second stage of fastening. Additionally, it should be understood that having a larger first contact angle 4 also adversely affects the contact pressure in the second stage of fastening.

[0129] As shown in FIG. 1 , the thread profiles 11, 21 of the threaded joint 100 may have secondary threads 19, 29, i.e., a secondary pin thread 19 and a secondary box thread 29. The secondary pin thread 19 is located a second axial distance from the pin free end 13. The primary pin thread 14 is located a first axial distance from the pin free end 13. Similarly, the secondary box thread 29 is located a second axial distance from the box free end 23. The primary box thread 24 is located a first axial distance from the box free end 23. The second axial distance is greater than the first axial distance. The stub flank height 154 of the secondary pin thread 19 is less than the stub flank height 254 of the secondary box thread 29.

[0130] Fourteen different example thread profiles, namely A through N, were analyzed to optimize the stab flank of the threaded joint 100. Table 1 below presents the results of the analysis.

[0131] [Table 1]

[0132] The examples have first stub flank radii ranging from 0.05 to 0.69 mm. Each example utilizes a constant thread taper angle of 2.33 degrees. Additionally, a compressive pin force of 1.5 tons was applied to each example during the analysis. This weight corresponds to the typical weight of two to three stacked tubular members inserted into Box 2 in a wellbore. Additionally, in all of the examples, the first stub flank radius is equal to the second stub flank radius.

[0133] In particular, the example relates to a thread profile having a 5-degree negative (center) stab flank and a negative (center) load flank. In this example, the load flank lead is greater than the stab flank lead. Thus, the axial thread width of the threads decreases axially toward the free ends of the pin and box. Furthermore, the axial distance between the threads increases axially from the free ends toward the tubular member containing the pin and box. At the end of the second stage of tightening, the stab flanks contact each other and / or the load flanks contact, where the final tightening position is achieved based on flank-to-flank interference. Notably, the tested example does not have a final tightening shoulder.

[0134] In a threaded joint where the final fastening position is achieved based on the stab flank and the load flank, interference, compression, and tension resistance must be provided by the threads. In particular, resistance to compressive loads is provided primarily by the stab flank, and resistance to tensile loads is provided primarily by the load flank. In the case of compression resistance, a large ratio of the central stab flank surface to the load flank height is advantageous, since compression resistance depends on the total surface size of the thread supporting the compressive load. A central stab flank surface height of 100% relative to the load flank height is considered to show resistance to compressive loads nearly equal to resistance to tensile loads. do.

[0135] In light of the above, Table 1 also includes an index of compression resistance for each example in the final fastener. A joint with a higher compression resistance is considered better than a joint with a lower compression resistance. In this regard, it should be understood that increasing the first stub flank radius generally involves a compromise in the size of the center stub flank surface.

[0136] As shown by Table 1, the ratio of the center stub flank height to the load flank height for the example decreases as the radius of the stab flank impact surface increases.

[0137] In Table 1, Examples A-E and M-N relate to thread profiles that result in a relatively unconcentrated distribution of contact pressure, meaning that the contact pressure is primarily located away from the center of the stab flank impact surface.

[0138] As can be seen from Table 1, the first and second contact angles of Examples A to E are smaller than those of Examples F to N. The larger the first contact angle, the more likely it is that the colliding stab flank surfaces can pass each other during the first stage of fastening. The smaller the first contact angle, the higher the risk of the joint catching during the first stage of fastening.

[0139] Examples F to N show good stabili- ty compared to Examples A to E. After all, a first contact angle of 30 degrees or more is sufficient to have smooth stabili- ty in the first stage of fastening.

[0140] Figure 6 shows a graph of normalized contact pressure versus normalized contact distance for various example thread profiles during the first stage of make-up. Figure 7 shows a graph of normalized contact pressure versus normalized contact distance for various example thread profiles during the second stage of make-up.

[0141] In both Figures 6 and 7, the center of the X-axis represents the center of the stub flank impact surface. Thus, the larger the first stub flank radius, the larger the first contact angle. Thus, Example L exhibits better puncture resistance than Example K, which exhibits better puncture resistance than Example J, and so on.

[0142] A larger primary contact angle allows for easier piercing, while also tending to result in a longer sliding distance in the second stage of fastening.

[0143] In FIG. 7, graphs that are biased to the right tend to require a longer sliding distance in the second stage to reach the final fastening position.

[0144] Figure 6 shows the contact pressure distribution for Examples F through L during the first stage of tightening. It can be seen from Figure 6 that the peak contact pressure increases across Examples F through L. For thread profiles with first stab flank radii of 0.41 mm through 0.56 mm (Examples H through K), the contact pressure for these examples is relatively evenly distributed across the contact distance at the center of the first stab flank impact surface. In contrast, the contact pressure distribution for Examples F and G, with first stab flank radii of 0.30 mm and 0.36 mm, respectively, is biased to the left along the X-axis.

[0145] 6, that is, among Examples F to L, Example I exhibits the most concentrated contact pressure distribution. Furthermore, Example I has a lower peak contact pressure than Examples J to L.

[0146] In FIG. 7, examples K and L show relatively high torque during the second stage of fastening compared to examples F to J. It can be seen that peak contact pressures occur. High peak contact pressures over short distances can cause damage to the threads. Furthermore, in Examples F-J, the peak contact pressure tends to decrease as the first stub flank radius increases. In particular, Example I exhibits a centralized contact pressure distribution and has the smallest peak in contact pressure.

[0147] Comparing the graphs in Figures 6 and 7, it can be seen that Examples G, H, I, and J perform well in the first and second stages of fastening. In particular, Examples G, H, I, and J exhibit a centralized contact pressure distribution in both stages of fastening and a relatively low peak contact pressure in the second stage of fastening. Examples H, I, and J exhibit an even more centralized contact pressure distribution and a relatively short sliding distance in the first and second stages of fastening. More particularly, Example I performs well in the first stage of fastening and exhibits the lowest peak contact pressure in the second stage of fastening.

[0148] Examples IH also provide thread profiles with good compression resistance.

[0149] Where necessary, detailed embodiments of the present invention are disclosed in the drawings. However, it should be understood that the disclosed embodiments are merely exemplary and that the present invention can be embodied in various forms. Therefore, the specific structural and functional details disclosed herein should not be construed as limiting, but merely as a basis for the claims, and as a representative basis to teach those skilled in the art to various uses in substantially any suitable detailed structure.

[0150] In particular, a thread profile or threaded joint according to the present invention may include so-called "run-in" and / or "run-out" at one or both of the axial thread ends. It is further contemplated that a thread profile or thread of a threaded joint according to the present invention may include a crest-to-root clearance. It is further contemplated that in a thread profile according to the present invention, the first stab flank radius may be equal to the second stab flank radius, and / or one or more thread crests may have a reduced height (e.g., by a conical or cylindrical cut).

[0151] The terms "a" or "an," as used herein, are defined as one or more than one. The terms "multiple" or "plural," 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.

[0152] It will be apparent to those skilled in the art that various modifications can be made to the illustrated thread profiles and threaded joints according to the invention without departing from the scope defined in the claims.

Claims

1. 1. A pin and box thread profile for a threaded joint for hydrocarbon well exploration and production, comprising: at least one helically extending thread on the pin; and at least one helically extending thread on the box, the thread having a stab flank having a stab flank height, a load flank having a load flank height, and a crest, wherein: the stub flank includes a stub flank impact surface abutting the stub flank at a crest, the stab flank impact surface has a first stab flank radius; - said threads are [Equation 1] [Equation 2] in accordance with In the formula, SFR １ is the first stub flank radius, SFH is the stab flank height, and LFH is the load flank height.

2. The threads are [Equation 3] Thread profile according to claim 1 , according to

3. The threads are [Equation 4] Thread profile according to claim 1 or 2, according to

4. The stub flank impact surface has a stub flank impact height, and the thread has [Equation 5] in accordance with 10. The thread profile of any preceding claim, wherein SFCH is the stab flank impact height.

5. The threads are [Equation 6] especially, [Equation 7] More particularly, [Equation 8] Thread profile according to any one of the preceding claims, according to

6. The threads are further [Equation 9] especially, [Equation 10] Thread profile according to any one of claims 1 to 5, according to

7. Thread profile according to any one of the preceding claims, wherein the difference between the first stab flank radius of the stab flank collision surface of the at least one thread of the pin and the first stab flank radius of the stab flank collision surface of the at least one thread of the box is less than 10%, in particular the first stab flank radius of the stab flank collision surface of the at least one thread of the pin and the first stab flank radius of the stab flank collision surface of the at least one thread of the box are equal to each other.

8. Thread profile according to any one of the preceding claims, wherein the stab flank of the thread is a vertical stab flank or a negatively inclined stab flank.

9. 10. A thread profile according to any one of the preceding claims, wherein the threads include a dovetail-shaped cross-section.

10. 10. A thread profile according to any one of the preceding claims, wherein the at least one helically extending thread of the pin has an axial thread width that decreases axially towards the free end of the pin, and the at least one helically extending thread of the box has an axial thread width that decreases axially towards the free end of the box.

11. The thread has a root, the stab flank has a stab flank inner surface, the stab flank inner surface has a second stab flank radius, and the thread further comprises: [0011] in accordance with In the formula, SFR ２ Thread profile according to any one of the preceding claims, wherein x is the second stub flank radius. 【Request Item 12】 【Number 12】 12. The thread profile of claim 11, wherein:

13. The pin threads are the primary pin threads, and the box threads are the primary box threads. Thread profile according to any one of the preceding claims, wherein the thread profile further comprises a plurality of secondary threads on the pin and a plurality of secondary threads on the box, wherein the primary threads on the pin and the secondary threads on the pin together form the helical length of the pin's thread, and wherein the primary threads on the box and the secondary threads on the box together form the helical length of the box's thread, wherein the primary threads on the pin are provided on at least 50%, in particular at least 80%, of the helical length of the pin's thread, and wherein the primary threads on the box are provided on at least 50%, in particular at least 80%, of the helical length of the box's thread.

14. 14. The thread profile of claim 13, wherein the primary helically extending thread is axially closer to the free end of the pin than the secondary helically extending thread.

15. 15. The thread profile of claim 13 or 14, wherein the primary pin thread is adapted to impinge on the primary box thread and is free to contact the secondary thread.

16. Thread profile according to any one of claims 13 to 15, wherein the secondary threads of the pin are configured to avoid collision with the secondary threads of the box.

17. Thread profile according to any one of the preceding claims, wherein the crests of the threads are parallel to the longitudinal axis of the helically extending thread.

18. 10. A threaded joint for the exploration and production of hydrocarbon wells, comprising a pin and a box and comprising a thread profile according to any one of the preceding claims.

19. 1. A pin for a threaded joint for hydrocarbon well exploration and production, comprising at least one helically extending thread, said at least one thread having a stab flank having a stab flank height, a load flank having a load flank height, and a crest, wherein: the stub flank includes a stub flank impact surface abutting the stub flank at a crest, the stab flank impact surface has a first stab flank radius; - said threads are [0013] [0014] in accordance with In the formula, SFR １ is the first stub flank radius, SFH is the stub flank height, and LFH is the load flank height, of the pin.

20. 1. A box of a threaded joint for hydrocarbon well exploration and production, comprising at least one helically extending thread, said at least one thread having a stab flank having a stab flank height, a load flank having a load flank height, and a crest, the stub flank includes a stub flank impact surface abutting the stub flank at a crest, the stab flank impact surface has a first stab flank radius; - said threads are [Equation 15] [0016] in accordance with In the formula, SFR １ is the first stub flank radius, SFH is the stub flank height, and LFH is the load flank height, box.

21. - providing a pin and a box having a thread profile according to any one of the preceding claims; - inserting said pin into said box in a first fastening stage; - in a second stage of fastening, rotating the pin relative to the box in the fastening direction; A method for forming a threaded joint, comprising:

22. 22. A method of forming a threaded joint as set forth in claim 21, wherein the rotating step occurs after the final insertion position is reached in the inserting step.

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