Threaded connector for oil well casing string

Abstract

Threaded tubular connector for an oil and gas well casing obtained by fitting a male and a female tool joint, which, starting from the free edge (19) of the male tool joint, comprises in succession: an inner metal-to-metal seal (25, 26), a first threaded portion (16a, 18a), an intermediate shoulder (22, 24), an intermediate metal-to-metal seal (27, 28), a second threaded portion (16b, 18b), the free edge (19) being at a non-zero axial distance (d) from the female tool joint, each of the threaded portions comprising helical lines having a load flank, a thread crest, an engagement flank and a thread root, such that the load flank pitches (LFLp1, LFLb1) and the engagement flank pitches (SFLp1, SFLb1) of the first threaded portion, and correspondingly the load flank pitches (LFLp2, LFLb2) and the engagement flank pitches (SFLp2, SFLb2) of the second threaded portion, satisfy the condition: [Mathematical formula 12] SFLb1 = LFLb1 = SFLb2 = LFLb2 = SFLp1 = LFLp1 = SFLp2 = LFLp2.

Description

TECHNICAL FIELD

[0001] The present invention relates to a pipe connector or assembly for connection by means of a thread, to industrial pipes, in particular to a threaded assembly or coupling for equipping a pipe string or production pipe accessories or a casing string for the exploration, prospecting or exploitation of oil or gas wells, and to a threaded assembly or coupling for any application where it may be necessary to assemble pipes or pipe accessories, such as in the geothermal industry or steam production. The threaded assembly according to the invention is particularly suitable for a metal pipe assembly for an oil or gas well casing as described below.

[0002] In the present text, except in a specific context, the terms "assembly", "connector", "coupling" or "joint" are used with the same meaning. "Pipe" means any type of pipe or tubular part or pipe accessory existing or suitable for use in industry, and these pipes are generally metal pipes. In particular, these pipes are seamless pipes made of steel, such as the pipes defined in API Specification 5CT or pipes that also comply with ISO Standard 11960:2004. Preferably, the connector according to the invention is obtained between pipes made of a material having a high fracture strength, such as steel having a grade between 862 MPa and 965 MPa (i.e., between 125 ksi and 140 ksi). BACKGROUND ART

[0003] Numerous types of assemblies for oil or gas pipes are known, which, from the point of view of mechanical properties and tightness, provide satisfactory results even under severe operating conditions. Some of these assemblies require pipes with male truncated cone threads at both ends, which are assembled by means of a coupling having two corresponding female truncated cone threads. The advantage of this type of assembly is that the two parts of the assembly are rigid due to the positive interference that may occur between the male and female threads. These are threaded connectors also known as T&C connections.

[0004] However, the outer diameter of these couplings is greater than the outer diameter of the corresponding pipes, and when these assemblies are used in a casing, it is required to drill a wellbore with an increased diameter. In the case of ultra-deep wells with a depth exceeding 4000 meters, where the casing needs to be lowered deeper into the well, assemblies without couplings are preferred, as taught in documents US 2992019, EP 0767335 or also US 2013 / 0015657. In this case, each pipe includes one end provided with a male tool joint and a second end provided with a female tool joint. The pipes are assembled end to end by connecting the male tool joint and the female tool joint. These assemblies are designated by the term "monolithic connector".

[0005] In order to meet the need for higher compressive resistance against internal and external pressures, an integral connector is known from document US 4662659, which has two offset threaded portions on both sides of an intermediate shoulder, and the intermediate shoulder is designed with a negative angle to increase the compressive resistance. In addition, this document teaches that the sealing area is provided on one side of the intermediate shoulder or on both sides of the intermediate shoulder by radial interference between conical surfaces, and the cone angles of these conical surfaces are slightly changed by an angle γ relative to each other. According to this document, this kind of sealing is specifically arranged in the center between the two threaded portions and close to the intermediate shoulder. Document US 2019 0040978 proposes the following alternative to document US 4662659: setting the specific geometry of these seals on both sides of the intermediate shoulder, modifying the thread shape and selecting a thread with a dovetail profile.

[0006] In addition, another connector is also known from document US 2017 0101830, which has two offset threaded portions on both sides of an intermediate shoulder. According to this document, a seal is provided between the threaded portion and the intermediate shoulder. Nowadays, the definition of this kind of seal reduces the performance and capacity of the intermediate shoulder, so this document teaches to provide an additional shoulder surface at the distal end of the male tool joint. Alternatively, other documents propose to modify the thread to compensate for the lower performance of the intermediate shoulder under compression. Therefore, these alternative threads are called "dovetail" threads and are assembled to lock the threaded portions together. For this purpose, it is proposed that the pitch values of the threaded portions are different for the load-bearing flank and the stabbing flank, so that the helix of this kind of thread presents a tooth width that gradually increases from one end to the other end along the turns of the helix, and the grooves defined between the spires of the helix also gradually decrease. Therefore, the assembly of the threaded portion is carried out until contact is obtained not only between the stabbing flanks but also between the load-bearing flanks. Although this kind of connector called "wedge-locking self-locking thread" is very effective, it is very difficult to machine and control during assembly.

[0007] Despite various known solutions, there is still a need as follows: to facilitate the machining of an integral connector suitable for forming a casing for ultra-deep wells, still achieve the performance in terms of compressive resistance against internal and external pressure cycles and tolerances under tension and compression, while accepting the machining and assembly tolerances inherent in the tubing or gas pipe field. In fact, it has also become obvious that the way of applying assembly grease to the joint is the primary factor for successful connection. The threaded connector according to the present invention allows better tolerance of the operating variations when applying a certain amount of grease. SUMMARY OF THE INVENTION

[0008] The advantages of the present invention are that it provides a one-piece connector which meets the technical requirements close to those of a sleeve connector and can have an efficiency close to that of a pipe. In particular, the connector according to the present invention can have an efficiency equivalent to 96% of the pipe efficiency. Generally, the efficiency is defined as the relationship between the critical cross-section of the connector and the cross-section of the regular part of the pipe between the two ends of the component. The critical cross-section of the connector is equal to the minimum critical cross-section of the male tool joint or the female tool joint.

[0009] The present invention is preferably applicable to threaded connectors with large diameters, and particularly applicable to pipes with an outer diameter greater than 177.8 mm (7 inches), preferably greater than 254 mm (10 inches), such as 406.4 mm (16 inches).

[0010] The present invention provides a connector with better adhesion in these aspects.

[0011] The present invention relates to a threaded tubular connector for drilling and / or exploiting oil and gas wells, comprising a first pipe with a male tool joint at a first distal end and a second pipe with a female tool joint at a second distal end. The male tool joint can be assembled with the female tool joint through fitting. The first pipe is assembled to the second pipe to jointly define a longitudinal axis X. When assembling the threaded tubular connector, the male tool joint sequentially includes, from the free edge of the first distal end of the first pipe towards the body of the first pipe: a male inner sealing surface, a first male thread portion, a male shoulder, a male intermediate sealing surface, and a second male thread portion. The female tool joint includes a female inner sealing surface for forming an inner seal through radial interference with the first male sealing surface, a first female thread portion meshing with the first male thread portion, a female shoulder abutting against the male shoulder, a female intermediate sealing surface for forming an intermediate seal through radial interference with the male intermediate sealing surface, and a second female thread portion meshing with the second male thread portion. In the assembled position, the free edge of the first distal end is at a non-zero axial distance (d) from the female tool joint. Each of the first male thread portion and the second male thread portion includes at least one helix equipped with a load flank, a thread crest, an engaging flank, and a thread root, such that the pitch LFLp1 of the load flank and the pitch SFLp1 of the engaging flank of the first male thread portion, and correspondingly the pitch LFLp2 of the load flank and the pitch SFLp2 of the engaging flank of the second male thread portion satisfy the following conditions:

[0012] [Mathematical formula 1]

[0013] SFL p1 = LFL p1 = SFL p2 = LFL p2 = k1

[0014] where k1 is a constant for at least two complete turns of each helix.

[0015] Preferably, each of the female thread portions may include at least one helix having a load flank, a thread crest, an engagement flank, and a thread root, such that the pitch LFLb1 of the load flank and the pitch SFLb1 of the engagement flank of the first male thread portion, and correspondingly the pitch LFLb2 of the load flank and the pitch SFLb2 of the engagement flank of the second male thread portion satisfy the following conditions:

[0016] [Mathematical formula 2]

[0017] SFL b1 = LFL b1 = SFL b2 = LFL b2 = k2

[0018] where k2 is a constant for at least two complete turns of each helix.

[0019] Preferably, the constants k1 and k2 may be equal.

[0020] For example, the first female thread portion may include an annular groove which, for example, can have a radial width less than the constant k2 and which is at a radial distance from the said at least two complete turns of the helix of the first female thread portion defined above.

[0021] Preferably, the helix of the first female thread portion may be frustoconical, or even completely frustoconical, for example having a taper between 5% and 15%, preferably between 8% and 12%. In this case, the helix of the first male thread portion may include a frustoconical portion and a cylindrical portion near the inner sealing surface, the frustoconical portion having the same taper as the helix of the first female thread portion.

[0022] Advantageously, the helix of the second female thread portion may be frustoconical, preferably completely frustoconical, for example having a taper between 5% and 15%, preferably between 8% and 12%. Also in this case, the helix of the second male thread portion may include a frustoconical portion having the same taper as the helix of the second female thread portion and a cylindrical portion near the intermediate sealing surface.

[0023] Preferably, the inner seal may be an annular-ring-to-cone seal, for example the male inner sealing surface is conical while the female inner sealing surface includes an annular portion. Advantageously, the intermediate seal may be of a different type from the inner seal. The intermediate seal may be a cone-to-cone seal, the female intermediate sealing surface and the male intermediate sealing surface being conical, in particular having substantially the same taper.

[0024] More particularly, the female inner sealing surface may successively include a first arc of radius R1 and a second arc of radius R2 from the body of the second tube towards the second distal end, such that the radii R1 and R2 satisfy the following conditions:

[0025] [Mathematical formula 3]

[0026] R1 < R2

[0027] The engaging flank and the load - bearing flank of the helix of the male thread portion may include straight - line portions, which are respectively connected to the adjacent thread crest and thread root through a transition radius, such that the engaging flank of the female thread portion may include at least one straight - line portion parallel to the engaging flank of the male thread portion, and this is the case for both the first thread portion and the second thread portion.

[0028] The present invention is also beneficial when the second distal end portion of the second tube can be upset to obtain an additional thickness. Advantageously, both distal end portions of the second tube are upset.

[0029] Alternatively and / or combinably, the outer diameter of the second distal end portion of the second tube may be less than 103% of the outer diameter of the second tube. Such a connector is referred to as an "embedded direct - connection type".

[0030] In a preferred embodiment of the present invention, the male thread portion, and correspondingly the female thread portion, may each include a single helix. In this case, the helix of the male thread portion, and correspondingly the female thread portion, may include at least 3 turns, preferably at least 4 turns. However, in a variant, the first male thread portion and / or the second male thread portion may include a plurality of helices, the plurality of helices extending along the same portion of the longitudinal axis, and the plurality of helices are such that the starting points of the plurality of helices may be evenly distributed, for example, in a plane perpendicular to the longitudinal axis of the threaded tubular connector. Therefore, the pitch of each helix is larger than the pitch in a single - helix configuration.

[0031] For ease of assembly, the taper of the thread crest and thread root of the male thread portion and the female thread portion may be less than the taper of the thread portion. For example, they may be parallel to the longitudinal axis of the connector. In this case, the radial height of the engaging flank of the male thread portion may be greater than the radial height of the load - bearing flank of the male thread portion. Brief Description of the Drawings

[0032] Other features and advantages of the present invention will be apparent from the following detailed description read in conjunction with the accompanying drawings, in which:

[0033] Figure 1 : An external view of the first tube according to the present invention;

[0034] Figure 2 : A longitudinal sectional view of the second tube according to the present invention;

[0035] Figure 3 : Figure 1 A partial longitudinal sectional view of the male tool joint of the first tube in ;

[0036] Figure 4 : Figure 2 Partial longitudinal sectional view of the female tool joint of the second pipe in

[0037] Figure 5 : Figure 1 The male tool joint of the first pipe in Figure 2 Partial longitudinal sectional view after the male tool joint of the first pipe in

[0038] Figure 6 : Partial longitudinal sectional view of the female non-threaded middle part of the female tool joint according to the present invention;

[0039] Figure 7 : Partial longitudinal sectional view of the male non-threaded middle part of the male tool joint according to the present invention;

[0040] Figure 8 : Partial longitudinal sectional view of the female non-threaded inner part of the female tool joint according to the present invention;

[0041] Figure 9 : Partial longitudinal sectional view of the male non-threaded inner part of the male tool joint according to the present invention;

[0042] Figure 10 : Partial longitudinal sectional view of the male threaded part of the male tool joint according to the present invention;

[0043] Figure 11 : According to Figure 10 Partial longitudinal sectional view of one tooth of the male threaded part of

[0044] Figure 12 : Partial longitudinal sectional view of the female threaded part of the female tool joint according to the present invention;

[0045] Figure 13 : According to Figure 12 Partial longitudinal sectional view of one tooth of the female threaded part of

[0046] Figure 14 : Figure 10 The male threaded part in Figure 12 Partial longitudinal sectional view of the female threaded part in the assembled position in

[0047] Figure 15 : Partial longitudinal sectional view of the groove formed in the female threaded part of the female tool joint according to the present invention for evacuating the excess pressure of the grease. Detailed Description of the Invention

[0048] As Figure 1As can be seen, the first pipe 12 includes a pipe body 120. The first pipe 12 has an axial length of several meters, for example, it is about 10 to 15 meters long. The first pipe extends along the longitudinal axis X. At the first axial end 121 of the first pipe 12, the first pipe 12 includes a male tool joint 18. The pipe body 120 includes an outer diameter, generally denoted as the nominal outer diameter. Opposite to the first axial end 121, the first pipe includes a second axial end 122. The outer diameter of the second axial end 122 is greater than the outer diameter of the pipe body 120.

[0049] Figure 2 A longitudinal sectional view of the second pipe 14 identical to the first pipe 12 is shown. The second pipe 14 includes a pipe body 140, and the pipe body 140 is equipped with a male tool joint at the first axial end 141 and a female tool joint 16 at the second axial end 142. The male tool joint is machined on the outer surface of the first axial end 121. The outer diameter of the second axial end 142 is greater than the outer diameter of the pipe body 140. The female tool joint is machined on the inner surface of the second end.

[0050] In the following description, the connection formed between the female tool joint 16 of the second pipe 14 and the tool joint 18 of the first pipe 12 will be described. For example, Figure 5 A connection according to the present invention is shown. Such a connection is called a semi - flush connection because the outer diameter at the formed connection is less than 105% or even 103% of the outer diameters of the pipe bodies 120, 140. The present invention is applicable to a standard flush connection, that is, for this, the outer diameter at the connection is less than 101% of the nominal outer diameter ODnom.

[0051] In the described embodiment, the first pipe 12 and the second pipe 14 are the same, and each includes a male tool joint 18 at its respective first ends 121, 141, and the first pipe and the second pipe also each include a female tool joint 16 at their respective second ends 122, 142.

[0052] Before machining the male tool joint 18, the first distal ends 121, 141 are tapered. The taper causes the inner diameter of the first ends 121, 141 to decrease starting from the narrowing portion 13 that forms the transition between the pipe body and the first end. Preferably, the inner diameter of the first end is limited relative to the nominal inner diameter of the pipe body such that after the connection is assembled, the inner diameter at the connection is greater than 94% of the nominal inner diameter. The first ends 121, 141 extend between the free edge 19 and the pipe body. The first end carrying the male tool joint 18 has a certain axial length of about 20 to 30 centimeters between the free edge 19 and the pipe body.

[0053] Similarly, before machining the female tool joint 16 at the second distal ends 122, 142, the second ends are subjected to a diameter expansion. As Figure 1 and Figure 2 shown, the diameter expansion 15 occurs at a distance from the free edges 17 of the second axial ends 122, 142 such that the second axial ends 122, 142 have a certain axial length of about 20 cm to 30 cm between the free edges 17 and the pipe body.

[0054] The male tool joint 18 includes two threaded portions, namely 18a and 18b respectively. These two threaded portions extend along two successive portions along the axis X. These two threaded portions are spaced apart from each other by a non-threaded intermediate portion 20. The male threaded portions 18a and 18b are radially offset with respect to the axis X. In fact, the male tool joint 18 includes a male shoulder 22 in the non-threaded intermediate portion 20. The male intermediate shoulder 22 defines an annular surface in a plane perpendicular to the axis X. Preferably, each of the male threaded portions 18a and 18b includes a single helix forming a single thread. Preferably, the pitches of the helical lines of each threaded portion are equal.

[0055] Between the free edge 19 and the first threaded portion 18a, the male non-threaded inner portion 30 includes an inner sealing surface 25.

[0056] Between the male intermediate shoulder 22 and the second male threaded portion 18b, the male non-threaded intermediate portion 20 includes an intermediate sealing surface 27.

[0057] The female tool joint 16 includes two threaded portions, namely 16a and 16b respectively. These two threaded portions extend along two successive portions along the axis X. These two threaded portions are spaced apart from each other by a non-threaded intermediate portion 21. The female threaded portions 16a and 16b are radially offset with respect to the axis X. In fact, the female tool joint 16 includes an intermediate shoulder 24 in the non-threaded intermediate portion 21. The female intermediate shoulder 24 defines an annular surface in a plane perpendicular to the axis X. Preferably, each of the male threaded portions 18a and 18b includes a single helix forming a single thread. Preferably, the pitches of the helical lines of each male threaded portion and each female threaded portion are equal.

[0058] Between the pipe body 14 and the first threaded portion 16a, the female tool joint 16 includes a female non-threaded inner portion 31 which includes an inner sealing surface 26.

[0059] Between the intermediate shoulder surface 24 and the second female threaded portion 16b, the female non-threaded intermediate portion 21 includes an intermediate sealing surface 28.

[0060] In the assembled position of the connection, in Figure 5 which,

[0061] - The free edge 19 is held at a non-zero axial distance "d" from the female tool joint 16, which axial distance is for example greater than 0.1 mm;

[0062] - The helix of the first male thread portion 18a meshes with the helix of the first female thread portion 16a;

[0063] - The helix of the second male thread portion 18b meshes with the helix of the second female thread portion 16b;

[0064] - The male intermediate shoulder 22 is in abutting contact with the female intermediate shoulder 24;

[0065] - The male internal sealing surface 25 is in radial interference contact with the female internal sealing surface 26 to form a metal-to-metal internal seal that protects the connection from internal pressure loads;

[0066] - The male intermediate sealing surface 27 is in radial interference contact with the female intermediate sealing surface 28 to form a metal-to-metal intermediate seal that protects the connection from external pressure loads;

[0067] - The free edge 17 of the female tool joint is at a non-zero axial distance from the male tool joint.

[0068] The connection according to the invention includes a single axial shoulder orthogonal to the axis X, which axial shoulder is obtained by the contact between the intermediate shoulders 22 and 24, and its main function is to mark the end of the connection assembly.

[0069] The radial thickness of the contact surface of these intermediate shoulders 22 and 24 is less than 20% of the cross-section of the pipe 120 or 140, which cross-section is defined between ODnom and IDnom. The machining of the male and female tool joints allows manufacturing tolerances, thus allowing the use of any pipe conforming to the specifications, the dimensions of which ODnom (nominal outside diameter) and IDnom (nominal inside diameter) comply with the specification tolerances defined in the API standard. Although the intermediate shoulders allow the absorption of part of the compression stress of the connection, their dimensions do not allow the absorption of all the compression loads.

[0070] On both sides of the metal-to-metal internal seal, the male non-threaded internal part 30 is at a non-zero radial distance from the female non-threaded internal part 31. The metal-to-metal internal seal is formed at a distance from the edge of this internal non-threaded area 30 - 31.

[0071] Except for the contact obtained for the metal-to-metal intermediate seal and for the abutment of the shoulders 22 and 24, the male non-threaded intermediate part 20 is at a non-zero radial distance from the female non-threaded internal part 21. The metal-to-metal intermediate seal is formed at a distance from the edge of the intermediate non-threaded area 20 - 21.

[0072] From Figure 2As can be seen, the metal-metal internal seal receives more stress than the intermediate seal. The intermediate seal is useful for ensuring the sealing performance under external pressure stress. Between the second threaded portion and the intermediate shoulder, the intermediate seal thus has the thickness of the male tool joint 18 and the female tool joint 16 at the sealing surface, which allows it to have high contact stability, especially under high tensile loads: no surface detachment occurs.

[0073] Specifically, in Figure 6 and Figure 7 according to an embodiment of the present invention, the intermediate seal is a cone-to-cone type seal. The male intermediate sealing surface 27 and the female intermediate sealing surface 28 are frustum-conical with the same taper. Alternatively, these sealing surfaces 27 and 28 may have substantially the same taper, meaning that the taper of one surface may be between the taper of the other surface + and - 1%. For example, the tapers of these surfaces 27 and 28 are between 15% and 25%, such as equal to 20% + / - 1%, or both equal to 20%.

[0074] The male intermediate sealing surface 27 is connected to the cylindrical surface 33 adjacent to the second threaded portion 18b on one side through the convex-concave bending portion 32, and is connected to the other cylindrical surface 35 adjacent to the male shoulder 22 on the other side through another convex-concave bending portion 34. The cylindrical surface 35 is connected to the male shoulder 22 through the transition radius 36. The convex-concave bending portions 32 and 34 are arranged such that they are convex on the side adjacent to the male intermediate sealing surface 27, and are concave when connected to their respective adjacent cylindrical surfaces. In fact, the convex-concave bending portions 32 and 34 make the outer diameter at the cylindrical surface 33 adjacent to the threaded portion 18b larger than the outer diameter of the cylindrical surface 35 adjacent to the male shoulder 22.

[0075] Similarly, the female intermediate sealing surface 28 is connected to the cylindrical surface 38 adjacent to the second female threaded portion 16b on one side through the convex-concave bending portion 37, and is connected to the other cylindrical surface 40 adjacent to the female shoulder 24 on the other side through another convex-concave bending portion 39. The convex-concave bending portions 37 and 39 are arranged such that they are convex on the side adjacent to the female intermediate sealing surface 28, and are concave when connected to their respective adjacent cylindrical surfaces. In fact, the convex-concave bending portions 37 and 39 make the inner diameter at the cylindrical surface 38 adjacent to the female threaded portion 16b larger than the inner diameter of the cylindrical surface 40 adjacent to the female shoulder 24.

[0076] The convex-concave surfaces 32, 34, 37, and 39 are tangentially connected. The convex-concave surfaces 32, 34, 37, and 39 include bending portions that are tangentially connected to each other with a bending radius between 3 mm and 30 mm.

[0077] More specifically, the cylindrical surface 40 is connected to the female shoulder 24 through a concave transition portion 41. The concave transition portion 41 has a frustoconical portion with a tangential connection to a bending radius less than 1 mm, and the bending radius of the concave transition portion 41 is tangent to the female shoulder 42 to avoid stress concentration near the female shoulder 24.

[0078] To avoid stress concentration near the male shoulder 22, the male shoulder is connected to the cylindrical surface 43 adjacent to one end of the first male thread portion 18a through a concave transition portion 42 with a large radius.

[0079] Similarly, the female shoulder 24 is connected to the adjacent cylindrical surface 45 of the first female thread portion 16a through a transition radius 44. In fact, in view of the male and female thread portions being obtained by machining respectively, the cylindrical surface 45 is adjacent to a groove 46 with a cylindrical bottom, and the groove is used to take out the tool for machining the thread of the first female thread portion 16a. The inner diameter determined by the groove 46 with a cylindrical bottom is larger than the inner diameter of the cylindrical surface 45. The groove 46 includes a frustoconical surface connected to the cylindrical surface 45.

[0080] In detail, in Figure 8 and Figure 9 According to an embodiment of the present invention, the inner seal is an annulus-to-cone seal. In this embodiment, the male inner seal surface 25 is frustoconical, and the female inner seal surface 26 is annular. In Figure 8 The female inner seal surface 26 is a curved portion obtained by a plurality of adjacent convex curved portions tangent to each other. In one embodiment, it includes two adjacent curved portions with radii R1 and R2 respectively, such that the curved portion R1 is closer to the pipe body 140 than the curved portion R2, and the radius R1 is smaller than the radius R2. Preferably, the radii R1 and R2 are greater than 30 mm. The annular female inner seal surface 26 is connected to the cylindrical surface 47 on one side of the pipe body 140 through a bending radius 48 that is at least one-third of the radii R1 and R2. On the opposite side, the annular female inner seal surface is connected to the adjacent cylindrical surface 50 of the first female thread portion 16a through a convex-concave surface, which is tangentially connected to the cylindrical surface 50 on the one hand and tangentially connected to the seal surface 26 on the other hand.

[0081] To contact the female inner seal surface 26, the male inner seal surface 25 includes a frustoconical portion with a taper between 10% and 20%. At the inner circumference of the male tool joint 12, the inner surface of the male tool joint is chamfered 51, so that the inner non-threaded portion 30 has a smaller thickness. Even if the inner seal causes an inner offset of the seal ring defined between the inner seal surface 25 and the free end 19, the male tool joint 18 will not significantly change the inner channel diameter, which is called the connector offset diameter.

[0082] The male inner sealing surface 25 is tangentially connected to the convex surface 52, which has a relatively large bending radius and is itself connected to the free edge 19 determined perpendicular to the axis X through the boundary connecting part 53. On the opposite side of the free edge 19, the male sealing surface is tangentially connected to the cylindrical surface 54 upstream of the thread starting point of the first male thread part 18a. This cylindrical surface 54 allows the tool for machining the thread to start.

[0083] The main radius R2 is determined so as to overcome the plasticization and stress of the female tool joint 16 above the inner seal. Therefore, this radius R2 is used for seal management against the load at the very high contact pressure. When the contact pressure is relatively moderate, the offset of the sealing ring of the male tool joint is also relatively moderate, and the position of the sealing point thus moves into the pipe body 140, so that the value of the radius R2 is no longer necessary. Therefore, for these working points, the radius R1 smaller than the radius R2 is used. The radial thickness of the sealing surface along the axis X enables it to allow a smaller thickness to machine the female inner sealing surface 26. Therefore, regardless of the pipe outer diameter, the female tool joint can be machined on the pipe, and for a given pipe thickness, the efficiency of the female tool joint is automatically improved. The bending radius 48 also allows reducing the thickness amount of the material required to machine the female tool joint, thus allowing an increase in the efficiency of the connecting piece for a given pipe thickness.

[0084] During the assembly process, the male inner sealing surface 25 first contacts the radius part R2. Due to the fact that this first contact may be very difficult, the fact of having an increased value of R2 makes it possible to limit the wear risk. Once the contact is established, the remaining assembly work is completed by moving the contact between the male inner sealing surface 25 and the radius part R1. This special configuration of the female inner sealing surface 26 improves the number and performance of the assembly fractures that the connecting piece according to the present invention can withstand.

[0085] In the following description, the thread will now be described.

[0086] In Figures 1 to 9 the illustrated embodiment, all the male thread parts 18a, 18b and the female thread parts 16a, 16b each respectively include a single helix.

[0087] However, in a variant, the male thread part and its complementary thread part can include the same number of helices with a number greater than 2 helices, and this is still within the scope of the present invention.

[0088] The helix is determined by a helical protrusion. The helix includes a load-bearing flank, a thread crest, an engaging flank and a thread root. The thread root, like the thread crest, is defined between the load-bearing flank and the engaging flank, such that

[0089] - on the helix carried by the male tool joint 18, the thread root is closer to the longitudinal axis X in the radial direction than the thread crest;

[0090] - On the helix carried by the female tool joint 16, the root of the thread of the helix is more radially distant from the longitudinal axis X than the crest of the thread.

[0091] The longitudinal cross-sectional profile of such a helical projection is said to be generally trapezoidal, as the crest of the thread extends axially between the load-bearing flank and the engaging flank accordingly.

[0092] Figure 10 The frustum 74 is shown on two turns of the helix of the first male thread portion 18a and accordingly the second male thread portion 18b. The structure of the helix described below is reproduced on at least a plurality of turns, on at least 3 turns, while maintaining the dimensions, shape and proportions specified below.

[0093] The helix of the male thread portion includes a load-bearing flank LFp, a thread crest 60, an engaging flank SFp and a thread root 61. The root 61 and the crest 60 form a section parallel to the longitudinal axis X. The thread root 61 is connected to the engaging flank SFp by a concave bending transition 62. The concave bending transition 62 causes the thread root 61 and the engaging flank SFp to form an angle greater than 90°. The engaging flank SFp is straight and forms an angle 63 with respect to the normal N of the longitudinal axis X. The thread root 61 is connected to the load-bearing flank LFp at one end of the thread root 61 by a second concave bending transition 64, which end is opposite to the end where the thread root is connected to the engaging flank SFp. The second concave bending transition 64 causes the thread root 61 to form an angle less than 90° with the load-bearing flank LFp. The load-bearing flank LFp is straight and forms an angle 65 with respect to the normal N of the longitudinal axis X.

[0094] This angle 65 is equal to the angle 63 plus or minus a machining tolerance of + / -0.25°. The engaging flank SFp is selected to be parallel to the load-bearing flank LFp so that the engaging flank bears a part of the load observed in the connecting piece under a certain compressive stress.

[0095] For example, the angle 63 is between 1° and 5°, preferably between 1.25° and 3.75°.

[0096] More specifically, in Figure 11 the bending transition 62 is controlled so as to be able to ensure the radial dimension of the engaging flank SFp. However, the thread root 61 may include a step having two staggered cylindrical portions 61a and 61b such that the cylindrical portion 61a adjacent to the bending transition 62 is more radially distant from the longitudinal axis X than the cylindrical portion 61b adjacent to the load-bearing flank LFp.

[0097] The crest 60 is connected to the engaging flank SFp by a convex bending transition portion 66. The crest 60 is connected to the load-bearing flank LFp by a complex convex surface 67, which includes a frustoconical portion 68 adjacent to the cylindrical portion of the crest 60, and the frustoconical portion 68 is connected to the load-bearing flank LFp by a bending radius 69.

[0098] The radial height of the engaging flank SFp is greater than the radial height of the load-bearing flank LFp, so that the external thread portion includes a frustoconical portion in one direction, in which a virtual line (pitch diameter line) PL passing through the midpoints of the successive engaging flanks SFp and load-bearing flanks LFp of the helix defines a taper angle 70 with respect to the longitudinal axis X. In this frustoconical portion, the helix is defined between the surfaces of two virtual frustoconical envelope surfaces 71 and 72 that are respectively parallel to the pitch diameter line PL. The virtual lower envelope surface 71 passes through the tangent points between the root 61 of each turn of the helix in this frustoconical portion and the bending transition portion 62 adjacent to the engaging flank SFp. The virtual upper envelope surface 72 passes through the tangent points between the convex bending transition portion 66 adjacent to the engaging flank SFp and the thread crest 60.

[0099] The taper angle 70 is such that the taper of the male thread portion 18a and / or 18b is between 5% and 15%, preferably between 8% and 12%.

[0100] In addition to the above-mentioned frustoconical portion 74, the helix also includes a cylindrical portion 73 located at one end of the helix, and the cylindrical portion 73 extends over more than one turn, preferably less than three turns, especially less than two turns. In the described embodiment, the end of the helix having the cylindrical portion 73 is arranged on the end side closest to the free edge 19 in the axial direction of the male thread portion. In particular, each of the first male thread portion 18a and the second male thread portion 18b includes such a cylindrical portion 73 adjacent to the frustoconical portion 74 of the helix.

[0101] The cylindrical portion 73 of the helix makes the successive roots 61 of this cylindrical portion parallel and collinear with each other. The virtual lower envelope surface 71 becomes parallel to the longitudinal axis X in this cylindrical portion, while the virtual upper envelope surface 72 maintains the same taper for both the frustoconical portion 74 and the cylindrical portion 73.

[0102] The helix of the male thread portion also includes an incomplete portion 75 at the opposite end of the male thread portion, i.e., at the helix end farthest axially from the free edge 19. In particular, each of the first male thread portion 18a and the second female thread portion 18b includes such an incomplete portion 75 adjacent to the frustoconical portion 74, and the frustoconical portion 74 is located between the incomplete portion 75 and the cylindrical portion 73. This incomplete portion 75 results in a smaller thread height, and the successive thread crests 60 of the incomplete portion 75 are parallel and collinear with each other. The imaginary upper envelope surface 72 becomes parallel to the longitudinal axis X in this incomplete portion 75. This incomplete portion 75 extends over more than one turn, preferably less than three turns, especially less than two turns. In the incomplete portion 75, the imaginary lower envelope surface 71 has the same taper as that observed in the frustoconical portion 74.

[0103] The presence of the cylindrical portion 73 allows the radial dimension of the male thread portion to be limited in the thickness of the wall forming the male tool joint. Therefore, a greater minimum thickness can be ensured at the male inner sealing surface 25 and the male intermediate sealing surface 27 respectively. Through this configuration of the male thread portion, the sealing performance is improved.

[0104] In addition, the presence of the cylindrical portion 73 adjacent to the frustoconical portion 74 can avoid a sudden change in the hardness of the male non-threaded inner portion 30. This configuration can avoid premature plasticization in the connecting member region that receives the maximum stress.

[0105] The helix of the male thread portion makes the pitch SFLp of the engaging flank constant in the frustoconical portion 74 and also constant in the incomplete portion 75. In particular, the pitch is the same in the frustoconical portion 74 and the incomplete portion 75. The pitch LFLp of the load-bearing flank is the same in the frustoconical portion 74 and the incomplete portion 75, and this pitch LFLp is also equal to the pitch of the engaging flank SFLp.

[0106] For the first male thread portion 18a, the pitch SFLp1 of the engaging flank and the pitch LFLp1 of the load-bearing flank are equal to a constant k1. Similarly, for the second male thread portion 18b, the pitch SFLp2 of the engaging flank and the pitch LFLp2 of the load-bearing flank are also equal to this constant k1. According to the present invention, this constant k1 is, for example, between 5 mm and 20 mm, preferably between 6 mm and 8 mm.

[0107] Preferably, the tooth width Wtp of the male thread portion is defined as the measured value of the distance along the longitudinal axis X between the engaging flank SFp and the load-bearing flank LFp at the intersection point intersecting the pitch diameter line PL, and this tooth width makes the width of the tooth less than half of the constant k1, especially less than 40% of the value of the constant k1.

[0108] Figure 12The conical portion 94 is shown on two turns of the helix of the first and second female thread portions 16a, 16b. The structure of the helix described below is reproduced on at least a plurality of turns, on at least 3 turns, while maintaining the dimensions, shape and proportions specified below.

[0109] The helix of the female thread portion includes a load flank LFb, a thread crest 80, an engaging flank SFb and a thread root 81. The thread crest 80 and the thread root 81 form a section parallel to the longitudinal axis X. The thread root 81 is connected to the engaging flank SFb by a concave bending transition 82. The concave bending transition 82 causes the thread root 81 and the engaging flank SFb to form an angle greater than 90°. As with the male thread root 61, the thread root 81 may include a step having two offset cylindrical portions 81a and 81b such that the cylindrical portion 81a adjacent to the concave bending transition 82 is closer to the longitudinal axis X in the radial direction than the cylindrical portion 81b of the thread root 81 adjacent to the load flank LFp.

[0110] The engaging flank SFp is straight and forms an angle 83 with respect to the normal N of the longitudinal axis X. The thread root 81 is connected to the load flank LFb at an end of the thread root 81 opposite to the end where the thread root 81 is connected to the engaging flank SFb by a second concave bending transition 84. The second concave bending transition 84 causes the thread root 81 and the load flank LFb to form an angle less than 90°. The load flank LFb is straight and forms an angle 85 with respect to the normal N of the longitudinal axis X.

[0111] This angle 85 is equal to angle 83 plus or minus a machining tolerance of + / -0.25°.

[0112] Angle 85 is equal to angle 65 plus or minus a machining tolerance of + / -0.25°.

[0113] Angle 83 is equal to angle 63 plus or minus a machining tolerance of + / -0.25°.

[0114] Angle 83 is, for example, between 1° and 5°, preferably between 1.25° and 3.75°.

[0115] At Figure 13As shown in more detail in, the crest 80 is connected to the engaging flank SFb by a convex bending transition 86. The bending transition 86 includes a tangential transition radius 86a with the engaging flank SFb, a tangential transition radius 86c with the crest 80, and a frustoconical surface 86b tangentially connected to the tangential connecting portions 86a and 86c on both sides. The frustoconical surface 86b forms an obtuse angle 86d with respect to the engaging flank SFb, for example, an opening angle between 190° and 240°, preferably about 225°. The frustoconical surface 86b forms a chamfer, which helps to insert the male tool joint into the female tool joint. The frustoconical surface 86b reduces the axial width of the crest 80, so that an additional space is defined between the frustoconical surface 86b and the complementary portion of the male thread portion, and this additional space can also help to reduce the grease pressure in the thread.

[0116] The crest 80 is connected to the load-bearing flank LFb by a complex convex surface 87, and the convex surface 87 includes a frustoconical portion 88 adjacent to the cylindrical portion of the crest 80, and the frustoconical portion 88 is connected to the load-bearing flank LFb by a bending radius 89.

[0117] The radial height of the load-bearing flank LFb is greater than the radial height of the engaging flank SFb, so that the female thread portion includes a frustoconical portion in one direction, and in this one direction, a cone angle 90 is determined with respect to the longitudinal axis X by an imaginary line (pitch diameter line) PL passing through the midpoints of the successive engaging flanks SFb and load-bearing flanks LFb of the helix.

[0118] The taper of this imaginary line is the same as the taper determined by the frustoconical portion 75 of the male thread portion, as can be seen from Figure 14 These lines PL overlap at the assembled position of the connector.

[0119] In the frustoconical portion 94 of the female thread portion, the helix is determined between the surfaces of two imaginary frustoconical envelopes 91 and 92 that are respectively parallel to the pitch diameter line PL. The imaginary upper envelope 91 passes through the tangent points between the root 81 of each turn of the thread in the frustoconical portion 94 and the bending transition 82 adjacent to the engaging flank SFb. The imaginary lower envelope 92 passes through the tangent points between the convex bending transition 86 adjacent to the engaging flank SFb and the thread crest 80.

[0120] The cone angle 90 makes the taper of the female thread portion 16a and / or 16b between 5% and 15%, preferably between 8% and 12%.

[0121] In addition to the above-mentioned frustoconical portion 94, the helical line further includes an incomplete portion 95 located at one end of the helical line. The incomplete portion 95 extends over more than one turn, preferably less than three turns, and particularly less than two turns. In the described embodiment, the end of the helical line is arranged on the end side of the female thread portion that is axially farthest from the free edge 17 of the female tool joint. In particular, each of the first female thread portion 16a and the second female thread portion 16b includes such an incomplete portion 95 adjacent to the frustoconical portion 94 of the helical line.

[0122] The incomplete portion 95 results in a smaller thread height. The successive thread crests 80 of the incomplete portion 95 are parallel and collinear with each other. The imaginary lower envelope surface 92 becomes parallel to the longitudinal axis X in the incomplete portion 95. In the incomplete portion 95, the imaginary upper envelope surface 91 has the same taper as that observed in the frustoconical portion 94.

[0123] In the assembled position of the male tool joint and the female tool joint, the incomplete portion 95 of the female thread portion engages with the cylindrical portion 73 of the corresponding male thread portion.

[0124] In an embodiment according to the present invention, the frustoconical portion 94 of the female thread portion includes more turns of the helix than the frustoconical portion 74 of the male thread portion. In fact, in the assembled position of the connector, the incomplete portion 75 of the male thread portion engages with the frustoconical portion of the female thread portion.

[0125] In particular, the first male thread portion 18a may include more turns of the helix than the second male thread portion 18b.

[0126] In particular, the first female thread portion 16a may include more turns of the helix than the second female thread portion 16b.

[0127] In particular, the frustoconical portion 74 of the first male thread portion 18a may include more turns of the helix than the frustoconical portion 74 of the second male thread portion 18b.

[0128] In particular, the frustoconical portion 94 of the first female thread portion 16a may include more turns of the helix than the frustoconical portion 94 of the second female thread portion 16b.

[0129] The helix of the female thread portion makes the pitch SFLb of the engaging flank constant in the frustoconical portion 94 and also constant in the incomplete portion 95. In particular, the pitch is the same in the frustoconical portion 94 and the incomplete portion 95. The pitch LFLb of the load-bearing flank is the same in the frustoconical portion 94 and the incomplete portion 95, and this pitch LFLb is also equal to the pitch SFLb of the engaging flank.

[0130] For the first female thread portion 16a, the pitch SFLb1 of the engaging flank and the pitch LFLb1 of the load-bearing flank are equal to a constant k2. Similarly, for the second female thread portion 16b, the pitch SFLb2 of the engaging flank and the pitch LFLb2 of the load-bearing flank are equal to the same constant k2.

[0131] According to the present invention, the constants kl and k2 are equal to each other, and these constants can also be represented by a constant term k. Considering machining tolerances, in the sense of the present invention, k1 is equal to k2 + / - 0.05 mm.

[0132] Preferably, the tooth width Wtb of the female thread portion is defined as the measured value of the distance along the longitudinal axis X between the engaging flank SFp and the load-bearing flank LFp at the intersection point intersecting the pitch diameter line PL, and this tooth width makes the width of the tooth greater than the tooth width Wtp of the tapered portion 74 of the male thread portion.

[0133] In fact, according to the present invention, and in the illustrated embodiment, it is important to determine that the width of the teeth of the male thread portion is smaller than the width of the teeth of the female thread portion. For example, in the illustrated embodiment,

[0134] [Mathematical formula 4]

[0135]

[0136] And

[0137] [Mathematical formula 5]

[0138] Wtp + Wtb < k

[0139] Preferably,

[0140] [Mathematical formula 6]

[0141]

[0142] Or even

[0143] [Mathematical formula 7]

[0144]

[0145] Since the teeth of the female thread portion are wider than the teeth of the male thread portion, the plasticization tendency of the female teeth is smaller. Now, in the connector according to the present invention, in the region 99 between the first teeth engaged on the inner sealing surfaces 25 and 26 sides and the sealing surfaces, the stress can be seen more clearly (see Figure 5 ).

[0146] The maximum shear line that can be modeled under compressive load in the connection according to the invention is shown at 45° relative to the crest 60 on the side where the crest 60 is connected to the engaging flank SFp. Conversely, the maximum shear line that can be modeled under tensile load in the connection according to the invention is shown at 45° relative to the crest 60 on the side where the crest 60 is connected to the load flank LFp. The intersection between these modeled shear lines makes it possible to determine the maximum stress triangles above each crest of the male threaded part. These triangles locate the areas in the female tool joint where the risk of plasticization is the greatest. The inventors have found that in order to maintain the efficiency of the connection, it is important to limit the height of these triangles, and therefore the required ratio is selected to limit plasticization in the female tool joint with limited thickness due to the integral connection design.

[0147] In such Figure 14 In the assembly position shown, the load flanks LFp and LFb are in contact, maintaining an axial play 100 between the engagement flanks SFp and SFb. Similarly, a radial play 101 is maintained between the crest 60 of the male threaded portion and the root 81 of the female threaded portion, while the imaginary lines 71 and 91 overlap as the crest 80 of the female threaded portion contacts the root 61 of the male threaded portion.

[0148] The radial play 101 may also limit the dimensioning of the maximum stress area in the box tool joint.

[0149] For example, the clearances 100 and 101 are between 0.1 mm and 0.5 mm, preferably between 0.2 and 0.3 mm. With such axial clearance, the tooth width satisfies the following conditions:

[0150] [Mathematical formula 8]

[0151] Wtp+Wtb<k-0.1mm

[0152] Due to the cylindrical-conical shape of the male threaded part, almost no free space remains between the helical lines of the assembled male and female threaded parts. When the connection according to the invention is used with an assembly grease applied to the male and female tool joints before they are assembled, there is almost no available space to avoid an increase in grease pressure in the connection. According to the invention, however, an annular groove 110 is provided in the female threaded part, in particular in the first female threaded part 16a, to allow the receipt of excess grease that flows back. The advantage of this groove is that it allows local accumulation of grease during use of the connection or during assembly under certain temperature and pressure conditions. The annular groove is provided in the female threaded part arranged between the two sealing surfaces.

[0153] In the embodiment shown, there is no seal between the free edge 17 of the female tool joint and the second female threaded portion and no annular groove is provided in the second female threaded portion.

[0154] In Figure 15 it, the annular groove 110 is defined between a virtual inner line 92 and an outer line 91. For example, the axial width G of the annular groove 110 is approximately a constant k. The annular groove 110 includes a frustoconical bottom 111, the taper of which is the same as that of the female thread portion. The annular groove is asymmetric. On one side of the bottom 111, on the side of the inner sealing surface 26, the bottom 111 is connected to a straight portion 112, which has an angle 113 between 10° and 30° with the normal N. On the other side of the bottom 111, on the side of the intermediate sealing surface 28, the bottom 111 is connected to another straight portion 114, which has an angle 115 between 30° and 85° with the normal N.

[0155] When the connector is arranged in an ultra-deep position and subjected to a temperature of about 180 °C, the groove allows the grease to degas without causing a temporary loss of sealing or the risk of local plasticization of the connector.

Claims

1. A threaded tubular connector for oil and gas well drilling and / or production, comprising a first pipe (12) with a male tool joint (18) at a first distal end (121) and a second pipe (14) with a female tool joint (16) at a second distal end (142), the male tool joint being capable of being assembled with the female tool joint by fitting, and the first pipe being assembled to the second pipe so as to together define a longitudinal axis (X). When assembling a threaded tubular connector, the male tool joint sequentially includes, from the free edge (19) of the first distal end portion of the first pipe towards the body (120) of the first pipe: A male inner sealing surface (25), a first male thread portion (18a), a male shoulder (22), a male intermediate sealing surface (27) and a second male thread portion (18b), the female tool joint comprising a female inner sealing surface (26) for forming an inner seal by radial interference with the first male sealing surface, a first female thread portion (16a) meshing with the first male thread portion, a female shoulder (24) abutting against the male shoulder, a female intermediate sealing surface (28) for forming an intermediate seal by radial interference with the male intermediate sealing surface, and a second female thread portion (16b) meshing with the second male thread portion. In the assembled position, the free edge (19) of the first distal end is at a non-zero axial distance (d) from the female tool joint. The first male thread portion and the second male thread portion each comprise at least one helix provided with a load flank, a thread crest, an engaging flank and a thread root, such that the pitch LFLp1 of the load flank and the pitch SFLp1 of the engaging flank of the first male thread portion, and correspondingly the pitch LFLp2 of the load flank and the pitch SFLp2 of the engaging flank of the second male thread portion, satisfy the following condition: [Mathematical formula 9] SFL p1 = LFL p1 = SFL p2 = LFL p2 = k1 where k1 is a constant for at least two complete turns of each helix; The inner seal is a ring-to-cone seal, the male inner sealing surface is frustoconical and the female inner sealing surface is a curved portion obtained from a plurality of adjacent convex curved portions tangent to each other, successively comprising a first circular arc with a radius R1 and a second circular arc with a radius R2 from the body of the second pipe towards the second distal end, such that the radii R1 and R2 satisfy the following condition: [Mathematical formula 11] R1 < R2.

2. The threaded tubular connector according to claim 1, wherein, The first female thread portion and the second female thread portion each comprise at least one helix provided with a load flank, a thread crest, an engaging flank and a thread root, such that the pitch LFLb1 of the load flank and the pitch SFLb1 of the engaging flank of the first male thread portion, and correspondingly the pitch LFLb2 of the load flank and the pitch SFLb2 of the engaging flank of the second male thread portion, satisfy the following condition: [Mathematical formula 10] SFL b1 = LFL b1 = SFL b2 = LFL b2 = k2 where k2 is a constant for at least two complete turns of each helix.

3. The threaded tubular connector according to claim 2, wherein, The constants k1 and k2 are equal.

4. The threaded tubular connector according to any one of claims 2 to 3, characterized in that, The first thread region of the female tool joint comprises an annular groove (110).

5. The threaded tubular connector according to any one of claims 2 to 3, characterized in that, The helix of the first female thread portion is frustoconical, having a taper between 5% and 15%.

6. The threaded tubular connector according to claim 5, characterized in that, The helix of the first male thread portion comprises a frustoconical portion and a cylindrical portion close to the male inner sealing surface, the frustoconical portion having the same taper as the helix of the first female thread portion.

7. The threaded tubular connector according to any one of claims 2 to 3, characterized in that, The helix of the second female thread portion is frustoconical, having a taper between 5% and 15%.

8. The threaded tubular connector according to claim 7, wherein, The helix of the second male thread portion includes a frustoconical portion having the same taper as the helix of the second female thread portion, and a cylindrical portion adjacent to the intermediate sealing surface.

9. The threaded tubular connector according to any one of claims 1 to 3, characterized in that, The intermediate seal is a cone-to-cone type seal, and the female intermediate sealing surface and the male intermediate sealing surface are conical and have substantially the same taper.

10. The threaded tubular connector according to any one of claims 1 to 3, characterized in that The engaging flank and the load-carrying flank of the helix of the male thread portion are respectively linear and are respectively connected to the adjacent thread crest (60) and thread root (61) through transition radii (62, 64, 66, 68). The engaging flank of the female thread portion includes at least one linear portion parallel to the engaging flank of the male thread portion, and this is the case for both the first thread portion and the second thread portion.

11. The threaded tubular connector according to any one of claims 1 to 3, characterized in that, The second distal end portion of the second tube is upset, i.e., to obtain an additional thickness.

12. The threaded tubular connector according to any one of claims 1 to 3, characterized in that, The outer diameter of the second distal end portion of the second tube is less than 103% of the outer diameter of the second tube.

13. The threaded tubular connector according to any one of claims 1 to 3, characterized in that, The first male thread portion and / or the second male thread portion can include multiple helices such that the multiple helices extend along the same portion of the longitudinal axis, and the multiple helices enable the starting points of the multiple helices to be evenly distributed in a plane perpendicular to the longitudinal axis of the threaded tubular connector.

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