Threaded connector with an asymmetric spiral thread

Abstract

A threaded tubular connection for an oil and gas well casing is obtained by screwing a male tool joint onto a female tool joint. The connection includes threaded portions (16a, 18a) such that the male threaded portion and the corresponding female threaded portion each include a helix that is provided with a load-bearing flank, a thread crest, an insertion flank, and a thread root, such that the pitches (LFLp, LFLb) of the load-bearing flanks and the pitches (SFLp, SFLb) of the insertion flanks satisfy the following condition: [Mathematical Formula 22] SFLb = LFLb = SFLp = LFLp = k. The tooth widths (Wtp) of the male helix and the tooth widths (Wtb) of the female helix are such that [Mathematical Formula 23] or [Mathematical Formula 24] and [Mathematical Formula 25] Wtp + Wtb < k.

Description

Technical Field

[0001] The present invention relates to connectors or assemblies for pipes intended to be connected by threads, and to pipes used in industry, in particular to threaded assemblies or joints for tubing or production pipe fittings or casing strings intended to equip exploration, well logging or production strings for oil or gas wells, and to threaded assemblies or joints for any application where it may be necessary to assemble pipelines or pipe fittings, for example in the geothermal energy industry or steam production. The threaded assembly according to the invention is particularly suitable for assembling metal pipes for oil or gas well casings, as described below. Background Art

[0002] In the present text, the words "assembly" or "connection" or "joining" or "joint", etc., have the same meaning, unless otherwise specified in a particular context. "Pipe" means any type of pipe or tubular member or pipe fitting existing or suitable for industrial applications, and these pipes are generally metal pipes. In particular, these pipes are seamless pipes obtained from steel, such as those defined in API Specification 5CT, or seamless pipes according to Standard ISO11960:2004. Preferably, the connector according to the invention is obtained between pipes made of a material having a high load fracture strength, such as steel of a grade between 862 and 965 MPa (between 125 and 140 ksi).

[0003] From the point of view of mechanical properties and sealing, there are known various assemblies for oil and gas pipes, which can provide satisfactory results even under severe operating conditions. Some of these assemblies require pipes that are equipped with truncated conical male threads at both ends, and these pipes are assembled by a coupling having two corresponding truncated conical female threads. Due to the possible positive interference between the male and female threads, the advantage of this assembly mode is to rigidize the two parts of the assembly. These are threaded coupling connectors, also known as T&C connectors.

[0004] However, the outer diameter of these couplings is larger than the outer diameter of the corresponding pipes, and when these assemblies are used for casings, it is necessary to produce larger diameter boreholes. In the case of very deep wells with a depth exceeding 4000 m, the casing will need to be inserted deep into the well, and it is known that assemblies without couplings are preferred, as taught in documents US 2992019, EP 0767335 or US 2013 / 0015657. In this case, each pipe includes one end equipped with a male tool joint and a second end equipped with a female tool joint. The pipes are assembled end-to-end by the connection between the male and female tool joints. These assemblies are denoted by the term "integral".

[0005] In response to the increased need to resist internal and external pressure, integral connections are known from document US 4662659, which are provided with two staggered thread portions on either side of an intermediate support, which intermediate support is designed as a negative angle to increase the resistance to pressure. Further, on one side or on either side of the intermediate support, the document teaches sealing the area by means of a radial interference between conical surfaces, the cone angles of the conical surfaces being slightly angled γ with respect to each other. According to the document, the seal is specifically provided centrally between the two thread portions and close to the intermediate support. Document US 20190040978 presents an alternative to document US 4662659 by specifying the specific geometry of these seals on either side of the intermediate support and by modifying the shape of the threads and selecting threads with a dovetail profile.

[0006] Further, another connector is known from document US 2017 0101830, which is provided with two staggered thread portions on either side of an intermediate support. According to the document, a seal is provided between the thread portion and the intermediate support. Now, the definition of this seal reduces the performance and capacity of the intermediate support, and thus the document teaches providing an additional support surface at the distal level of the male tool joint. Alternatively, other documents propose modifying the threads to compensate for the lower performance of the intermediate support under compression. These alternative threads are thus called "dovetail" threads and in a manner that locks the thread portions together. To this end, it is proposed that the pitch value of the thread portion be different for the load flank and the insertion flank, such that the helix of the thread has: a tooth width that gradually increases with the turns of the helix from one end to the other; a hollow portion defined between the helical portions of the helix, which hollow portion decreases in the same process. Thus, the assembly of the thread portions is carried out until contact is obtained not only between the insertion flanks but also between the load flanks. Although this connector, called a "self-locking wedge thread", is very effective, it is difficult to machine and difficult to master during assembly.

[0007] Despite the various solutions known, there is a need to facilitate the machining of integral connections suitable for forming casings for very deep wells, while achieving the performance of resisting internal and external pressure cycles and the tolerances under traction and compression, while accepting the machining and assembly tolerances inherent in the oil and gas pipe field. In practice, it is obvious that the manner of applying assembly grease to the joints is a primary factor in successful connection. The threaded connector according to the present invention can better tolerate the handling variations when a certain amount of grease is applied. SUMMARY OF THE INVENTION

[0008] The advantage of the present invention is to propose an integral connector that responds to technical requirements close to those of the sleeve connector and enables an effectiveness close to that of the pipe. In particular, the connector according to the present invention can have an effectiveness equal to 96% of the effectiveness of the pipe. Effectiveness is generally 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 applied to threaded connectors with large diameters, particularly 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 proposes a connector with better adhesion in these aspects.

[0011] The subject of the present invention is a threaded tubular connector for drilling and / or exploiting oil and gas wells, which includes a first pipe equipped with a male tool joint at a first distal end and a second pipe equipped with a female tool joint at a second distal end. The male tool joint can be assembled with the female tool joint by screwing. The first pipe is assembled to the second pipe, together defining a longitudinal axis. The male tool joint includes a male threaded part, and the female tool joint includes a female threaded part that meshes with the male threaded part when the connector is assembled. The male threaded part and the female threaded part each include at least one helix equipped with a load flank, a thread crest, an insertion flank, and a thread root, such that for at least two consecutive turns of the corresponding helices of the male and female threaded parts, the pitch LFLp of the load flank and the pitch SFLp of the insertion flank of the male threaded part and the pitch LFLb of the load flank and the pitch SFLb of the insertion flank of the female threaded part satisfy the following conditions:

[0012]

Mathematical formula 1

[0013] SFLp = LFLp = SFLb = LFLb = k

[0014] And such that along the longitudinal axis, in these at least two consecutive turns, the tooth width (Wtp) of the helix of the male threaded part and the tooth width (Wtb) of the helix of the corresponding female threaded part satisfy:

[0015]

Mathematical formula 2

[0016]

[0017] Or

[0018]

Mathematical formula 3

[0019]

[0020] And

[0021]

Mathematical formula 4

[0022] Wtp + Wtb < k

[0023] Preferably, the connecting member can satisfy the following conditions:

[0024]

Mathematical formula 5

[0025]

[0026] Even the following conditions

[0027]

Mathematical formula 6

[0028]

[0029] The tooth width of the helix of the male thread portion can be between 2.5 mm and 3.5 mm. And for example, the tooth width of the helix of the female thread portion can be between 3.7 mm and 4.5 mm.

[0030] Preferably, the tooth widths of the helixes of the male thread portion and the female thread portion can satisfy the following conditions on at least two consecutive turns of these helixes:

[0031]

Mathematical formula 7

[0032] Wtp + Wtb < k - 0.1 mm

[0033] So that these at least two turns may not be self-locking.

[0034] The tooth widths of the complete helixes of the male thread and the corresponding female thread can satisfy the following conditions: for each turn (n), the tooth width (Wtpn) of the male thread and the tooth width (Wtbn) of the female thread are such that for each n:

[0035]

Mathematical formula 8

[0036] Wtpn + Wtbn < k - 0.1 mm

[0037] Advantageously, a part of the inserted flank can be parallel to a part of the load-bearing flank, where the inclination of these parts with respect to the longitudinal axis has a tolerance of ±0.25°. Thus, the inserted flank can contribute to bearing the compressive load.

[0038] The flanks of the helix of the male thread portion that are inserted and load-bearing can be linear respectively, and are connected to the adjacent thread crest and thread root by a bending radius respectively. In this case, the flanks of the helix of the female thread portion that are inserted can also include a linear section, which is connected to the thread crest by a section inclined with respect to the inserted flank to form a convex surface, such that the two sections form an obtuse angle (86d) between 190° and 260°, for example approximately 225°, therebetween. This convex surface makes it possible to ensure non-contact with the thread root 61 and a part of the recessed bending transition 62.

[0039] The thread root of the helix of the male thread portion can include two sections: a first male thread root section, which is located on one side of the inserted flank; a second male thread root section, which is located on one side of the load-bearing flank, and such that the radial distance of the first male thread root section is equal to or greater than the radial distance of the second male thread root section, the radial distance being evaluated with respect to the thread crest adjacent to the thread root of the helix of the male thread portion.

[0040] The load-bearing flank of the helix of the male thread portion can form an angle between 1° and 5°, preferably between 1.25° and 3.75°, with respect to the normal of the longitudinal axis, and is parallel to the load-bearing flank of the helix of the female thread portion, and the inclination tolerance of these load-bearing flanks with respect to the longitudinal axis is + / ﹣0.25°.

[0041] In particular, the load-bearing flank of the helix of the male thread portion can form an angle less than or equal to 90° with the adjacent thread root of this helix.

[0042] For example, the helix of the female thread portion can be frustoconical, preferably completely frustoconical, for example having a taper between 5% and 15%, preferably between 8% and 12%. In this case, the helix of the male thread portion can also include at least one frustoconical portion, which has the same taper as the helix of the female thread portion.

[0043] According to a specific embodiment of the present invention, the pitch LFLp of the load-bearing flank and the pitch SFLp of the inserted flank can be between 5 mm and 20 mm, preferably between 6 mm and 8 mm.

[0044] In a preferred embodiment of the present invention, the male thread portion and the corresponding female thread portion can each include a single helix. In this case, the helix of the male thread portion and the corresponding female thread portion can include at least 3 turns, preferably at least 4 turns.

[0045] For ease of assembly, the thread crests and thread roots of the male thread portion and the female thread portion may have a taper that is less than the taper of the thread portion. For example, they may be parallel to the longitudinal axis of the connecting member. In this case, the radial height of the insertion 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

[0046] Other features and advantages of the present invention will become apparent upon reading the following detailed description with reference to the accompanying drawings, which show:

[0047]

Figure 1

[0048]

Figure 2

[0049]

Figure 3

[0050]

Figure 4

[0051]

Figure 5

[0052]

Figure 6

[0053]

Figure 7

[0054]

Figure 8

[0055]

Figure 9

[0056]

Figure 10

[0057]

Figure 11

[0058]

Figure 12

[0059]

Figure 13

[0060]

Figure 14

[0061]

Figure 15

[0062] As Figure 1 shows, the first pipe 12 includes a pipe body 120. The first pipe 12 has an axial length of several meters, for example, a length of about 10 m to 15 m. It 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, which is generally denoted as the nominal outer diameter. The first pipe includes a second axial end 122 opposite to the first axial end 121. The outer diameter of the second axial end 122 is greater than the outer diameter of the pipe body 120.

[0063] 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 provided 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 this second end.

[0064] In the following description, the connection member 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 shows a connection member according to the present invention. Such a connection member is called a semi-flush connection member as long as the outer diameter at the level of the formed connection member is less than 105% or even 103% of the outer diameters of the pipe bodies 120, 140. The present invention is applicable to connection members that can be flush, that is, the outer diameter at the level of the connection member is less than 101% of the nominal outer diameter ODnom.

[0065] In the described example, the first tube 12 and the second tube 14 are identical, and each tube includes a male tool joint 18 at its respective first ends 121 and 141, and each tube also includes a female tool joint 16 at its respective second ends 122 and 142.

[0066] Before machining the male tool joint 18, the first distal ends 121, 141 are tapered. Tapered into a cone results in a reduction in the inner diameter of the first ends 121, 141 starting from the narrowing portion 13 that forms a transition between the tube body and the first end. Preferably, the inner diameter of the first end is limited relative to the nominal inner diameter of the tube body such that after the connector is assembled, the inner diameter at the level of the connector is greater than 94% of the nominal inner diameter. The first ends 121, 141 extend between the free edge 19 and the tube body. This first end carrying the male tool joint 18 has an axial length between the free edge 19 and the tube body, and this axial length is approximately 20 cm to 30 cm.

[0067] Similarly, before machining the female tool joint 16 at the level of the second distal ends 122, 142, the second end undergoes radial expansion. As Figure 1 and 2 shown, the radial expansion 15 occurs at a distance from the free edge 17 of the second axial ends 122, 142 such that the second axial ends 122, 142 have an axial length between the free edge 17 and the tube body, and this axial length is approximately 20 cm to 30 cm.

[0068] 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. They are separated 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 support shoulder 22 in the non-threaded intermediate portion 20. The male intermediate support 22 defines an annular surface in a plane perpendicular to the axis X. Preferably, the male threaded portions 18a and 18b each include a single spire that forms a single helix. Preferably, the pitch of the helix of each threaded portion is the same.

[0069] Between the free edge 19 and the first threaded portion 18a, the male non-threaded inner portion 30 includes an inner sealing surface 25.

[0070] Between the male intermediate support 22 and the second male threaded portion 18b, the male non-threaded intermediate portion 20 includes an intermediate sealing surface 26.

[0071] The female tool joint 16 includes two threaded portions, namely 16a and 16b. These two threaded portions extend along two successive portions along the axis X. They 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 support shoulder 24 in the non-threaded intermediate portion 21. The female intermediate support 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 portion forming a single helix. Preferably, the pitches of the helices of each of the male threaded portion and the female threaded portion are the same.

[0072] Between the pipe body 14 and the first threaded portion 16a, the female tool joint 16 includes a female non-threaded internal portion 31, and the female non-threaded internal portion 31 includes an internal sealing surface 27.

[0073] Between the intermediate support surface 24 and the second female threaded portion 16b, the female non-threaded intermediate portion 21 includes an intermediate sealing surface 29.

[0074] In the assembled position of the connection, in Figure 5 in,

[0075] - The free edge 19 is held at a non-zero axial distance "d" from the female tool joint 16, for example, greater than 0.1 mm;

[0076] - The helix of the first male threaded portion 18a meshes with the helix of the first female threaded portion 16a,

[0077] - The helix of the second male threaded portion 18b meshes with the helix of the second female threaded portion 16b,

[0078] - The male intermediate support 22 is in abutting contact with the female intermediate support 24,

[0079] - The male internal sealing surface 25 is in radial interference contact with the female internal sealing surface 26 to form an internal metal-to-metal seal that protects the connection from internal pressure loads,

[0080] - The male intermediate sealing surface 27 is in radial interference contact with the female intermediate sealing surface 28 to form an intermediate metal-to-metal seal that protects the connection from external pressure loads,

[0081] - The axial distance between the free edge 17 of the female tool joint and the male tool joint is non-zero.

[0082] The connection according to the present invention includes a single axial support orthogonal to the axis X, which is obtained by the contact between the intermediate supports 22 and 24, and its main function is to mark the end of the make-up of the connection.

[0083] The radial thickness of the surfaces in contact with these intermediate supports 22 and 24 is less than 20% of the cross-section of the pipe 120 or 140, which is delimited between ODnom and IDnom. The machining of the male and female tool joints allows manufacturing tolerances, which makes it possible to use any compatible pipe, the dimensions ODnom and IDnom of which comply with the dimensional tolerances specified in the API standard. However, the intermediate supports can still absorb a part of the compression stress of the connection, but their dimensions do not allow them to absorb all of the compression load.

[0084] On either side of the internal metal-to-metal seal, the radial distance between the male non-threaded internal part 30 and the female non-threaded internal part 31 is non-zero. The internal metal-to-metal seal is created at a distance from the edge of this internal non-threaded area 30 - 31.

[0085] Except at the level of the contact obtained for the abutment of the intermediate metal-to-metal seal and the support shoulders 22 and 24, there is a non-zero radial distance between the male non-threaded intermediate part 20 and the female non-threaded internal part 21. The intermediate metal-to-metal seal is created at a distance from the edge of this intermediate non-threaded area 20 - 21.

[0086] As Figure 2 shown, the internal metal-to-metal seal is subject to more stress than the intermediate seal. The intermediate seal is used to ensure the seal under external compressive stress. Between the second threaded part and the intermediate support, the intermediate seal thus has the thickness of the male and female tool joints 18 and 16 at the level of this sealing surface, which allows it to have a high contact stability, especially in the case of high tensile loads: the surfaces do not separate.

[0087] Specifically, in Figure 6 and Figure 7 according to an embodiment of the invention, the intermediate seal is of the cone-to-cone type. The male intermediate sealing surface 27 and the female intermediate sealing surface 28 are frustoconical with the same taper. Alternatively, these surfaces 27 and 28 can have substantially the same taper, in the sense that the taper of one surface can be between + and - 1% of the taper of the other surface. For example, the tapers of these surfaces 27 and 28 are between 15% and 25%, for example equal to 20% + / - 1%, or both equal to 20%.

[0088] The male intermediate sealing surface 27 is connected on one side through the convex-concave bending portion 32 to the cylindrical surface 33 adjacent to the second threaded portion 18b, and on the other side through another convex-concave bending portion 34 to another cylindrical surface 35 adjacent to the male support shoulder 22. The cylindrical surface 35 is connected to the male support shoulder 22 through the bending radius 36. The convex-concave bending portions 32 and 34 are arranged such that they protrude on the side adjacent to the male intermediate sealing surface 27 and are recessed when they are respectively connected to their respective adjacent cylindrical surfaces. In practice, the convex-concave bending portions 32 and 34 make the outer diameter at the level of the cylindrical surface 33 adjacent to the threaded portion 18b greater than the outer diameter of the cylindrical surface 35 adjacent to the male support 22.

[0089] Similarly, the female intermediate sealing surface 28 is connected on one side through the convex-concave bending portion 37 to the cylindrical surface 38 adjacent to the second female threaded portion 16b, and on the other side through another convex-concave bending portion 39 to another cylindrical surface 40 adjacent to the female support shoulder 24. The convex-concave bending portions 37 and 39 are arranged such that they protrude on the side adjacent to the female intermediate sealing surface 28 and are recessed when they are respectively connected to their respective adjacent cylindrical surfaces. In practice, the convex-concave bending portions 37 and 39 make the inner diameter at the level of the cylindrical surface 38 adjacent to the female threaded portion 14b greater than the inner diameter of the cylindrical surface 40 adjacent to the female support 24.

[0090] 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 and have a bending radius between 3 mm and 30 mm.

[0091] More specifically, the cylindrical surface 40 is connected to the female support shoulder 24 through the recessed transition portion 41. The recessed transition portion 41 has a frustoconical portion tangent to a bending radius of less than 1 mm, and the bending radius of the recessed transition portion 41 is tangent to the female support shoulder 24 to avoid stress concentration near the female support shoulder 24.

[0092] To avoid stress concentration near the male support shoulder 22, the male support shoulder is connected to the cylindrical surface 43 adjacent to the end of the first male threaded portion 18a through the large-radius recessed transition portion 42.

[0093] Similarly, the female support shoulder 24 is connected to the adjacent cylindrical surface 45 of the first female threaded portion 16a by a bending radius 44. In practice, assuming that the male threaded portion and the female threaded portion are obtained by machining respectively, the cylindrical surface 45 is adjacent to a groove 46 having a cylindrical bottom for removing the tool for machining the threads of the first female threaded portion 16a. The cylindrical bottom groove 46 having a cylindrical bottom defines an inner diameter larger than the inner diameter of the cylindrical surface 45. The groove 46 includes a frustoconical surface that joins the cylindrical surface 45.

[0094] Specifically, in Figure 8 and Figure 9 according to an embodiment of the present invention, the inner seal is of the ring-to-cone type. In this example, the male inner seal surface 25 is frustoconical while the female inner seal surface 26 is annular. In Figure 8 the female inner seal surface 26 is a curve obtained by a plurality of adjacent convex bending portions tangent to each other. In one example, it includes two adjacent bending portions having radii R1 and R2 respectively, such that the bending portion R1 is closer to the pipe body 140 than the bending portion R2, and the radius R1 is shorter 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 the side of the pipe body 140 by a bending radius 48, and the radii R1 and R2 are at least three times longer than the radius of the bending radius 48. On the opposite side, it is connected to the adjacent cylindrical surface 50 of the first female threaded portion 16a by a convex-concave surface that is tangentially connected to the cylindrical surface 50 on the one hand and tangentially connected to the seal surface 26 on the other hand.

[0095] In order to contact the female inner seal surface 26, the male inner seal surface 25 includes a frustoconical portion having a taper between 10% and 20%. At the inner peripheral level of the male tool joint 12, the inner surface of the male tool joint is chamfered 51 such that the inner non-threaded portion 30 has a smaller thickness, and even if the inner seal causes internal flexure of the seal ring defined between the inner seal surface 25 and the free end 19, the male tool joint 18 basically does not change the inner channel diameter, which is called the connection offset diameter.

[0096] The male inner seal surface 25 is tangentially connected to a convex surface 52 having a large bending radius, and the convex surface 52 itself is connected to the free edge 19 perpendicular to the axis X through an interface 53. On the side opposite to the free edge 19, the male seal surface is tangentially connected to a cylindrical surface 54 located upstream of the start of the threads of the first male threaded portion 18a. This cylindrical surface 54 allows the tool to start machining the threads.

[0097] The major radius R2 is determined to overcome stress and the plasticization of the female tool joint 16 above the internal seal. Thus, this radius R2 is intended to manage the seal for loads with very high contact pressures. When the contact pressure is more moderate, the deflection of the sealing ring of the male tool joint is also more moderate, so the position of the sealing point moves towards the inside of the pipe body 140, making the value of the radius R2 no longer necessary. Therefore, for these operating points, a radius R1 smaller than the radius R2 is used. The radial thickness of the sealing surface along the axis X enables the use of a smaller thickness to machine the internal female sealing surface 26. Thus, the machining of the female tool joint can be carried out on the pipe, regardless of their outer diameter, and for a given pipe thickness, the effectiveness of the female tool joint automatically increases. The bending radius 48 also enables the reduction of the amount of material thickness required to machine the female tool joint, thus improving the connection effectiveness for a given pipe thickness.

[0098] During make-up, the male internal sealing surface 25 makes first contact with the radius portion R2. Since the first contact may be rough, increasing the value of R2 can limit the risk of wear. Once the contact is established, the remaining make-up is completed by moving the contact between the male internal sealing surface 25 and the radius portion R1. This specific configuration of the female internal sealing surface 26 improves the performance of the connector according to the invention and the number of make-up disconnections that can be tolerated.

[0099] In the remainder of the description, we will now describe the threads.

[0100] In Figures 1 to 9 the illustrated embodiment, all of the male thread portions 18a, 18b and the female thread portions 16a and 16b each include a single helix.

[0101] However, in a variant, although still within the scope of the invention, the male thread portion and its complementary thread portion may include one helix and the same number of helices more than 2.

[0102] The helix is defined by a helical protrusion. The helix includes a load-bearing flank, a thread crest, an insertion flank, and a thread root. Like the thread crest, the thread root is defined between the load-bearing flank and the insertion flank, such that

[0103] - 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;

[0104] - on the helix carried by the female tool joint 16, the thread root of this helix is farther from the longitudinal axis X in the radial direction than the thread crest.

[0105] As long as the thread crest axially extends between the load-bearing flank and the insertion flank respectively, the longitudinal cross-sectional profile of the helical protrusion is said to be substantially trapezoidal.

[0106] Figure 10 Denotes the frustoconical portion 74 on two turns of the helix of the first male thread portion 18a and the second male thread portion 18b. The structure described below for the helix is replicated on at least several turns, at least 3 turns, while maintaining the dimensions, shapes and proportions listed below.

[0107] The helix of the male thread portion includes a load-bearing flank LFp, a thread crest 60, an insertion flank SFp and a thread root 61. The thread crest 60 and the thread root 61 form a section parallel to the longitudinal axis X. The thread root 61 is connected to the insertion flank SFp by a recessed bending transition 62. The recessed bending transition 62 causes the thread root 61 and the insertion flank SFp to form an angle greater than 90°. The insertion 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 recessed bending transition 64, which is opposite to the end where the thread root is connected to the insertion flank SFp. The second recessed bending transition 64 causes the thread root 61 and the load-bearing flank LFp to form an angle less than 90°. The load-bearing flank LFp is straight and forms an angle 65 with respect to the normal N of the longitudinal axis X.

[0108] The angle 65 is equal to the angle 63 plus or minus the machining tolerance, i.e., + / −0.25°. The insertion flank SFp is selected to be parallel to the load-bearing flank LFp such that the insertion flank bears a part of the load observed in the connection under a certain compressive stress.

[0109] The angle 63 is, for example, between 1° and 5°, preferably between 1.25° and 3.75°.

[0110] More specifically, in Figure 11 , the bending transition 62 is controlled to be able to ensure the radial dimension of the insertion flank SFp. However, the thread root 61 may include a stepped portion having two staggered cylindrical portions 61a and 61b such that the cylindrical portion 61a adjacent to the bending transition 62 is farther from the longitudinal axis X in the radial direction than the cylindrical portion 61b close to the load-bearing flank LFp.

[0111] The thread crest 60 is connected to the insertion flank SFp by a protruding bending transition 66. The thread crest 60 is connected to the load-bearing flank LFp by a composite convex surface 67, which includes a frustoconical portion 68 adjacent to the cylindrical portion of the thread crest 60, and the frustoconical portion 68 is connected to the load-bearing flank LFp by a bending radius 69.

[0112] The radial height of the insertion flank SFp is greater than the radial height of the load flank LFp, such that the male thread portion includes a frustoconical portion in a direction of a cone angle 70 defined by an imaginary line PL (pitch line) passing through the centers of the successive insertion flanks SFp and load flanks LFp of the helix with respect to the longitudinal axis X. In this frustoconical portion, the helix is defined between surfaces of two imaginary frustoconical envelopes 71 and 72 that are respectively parallel to the pitch line PL. The imaginary lower envelope 71 passes through the tangent point between the root 61 of each turn of the helix in this frustoconical portion and the curved transition 62 adjacent to the insertion flank SFp. The imaginary upper envelope 72 passes through the tangent point between the protruding curved transition 66 adjacent to the insertion flank SFp and the crest 60 of the thread.

[0113] The 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%.

[0114] In addition to the above frustoconical portion 74, the helix also includes a cylindrical portion 73 located at one end of the helix, which cylindrical portion 73 extends over more than one turn, preferably less than three turns, especially less than two turns. In the described embodiment, this end of the helix having the cylindrical shape 73 is provided on the side of the male thread portion axially closest to the free edge 19. In particular, the first male thread portion 18a and the second male thread portion 18b each include this cylindrical portion 73 adjacent to the frustoconical portion 74 of the helix.

[0115] The cylindrical portion 73 of the helix is such that the successive roots 61 of this cylindrical portion are parallel and collinear with each other. The imaginary lower envelope 71 becomes parallel to the axis X in this cylindrical portion, while the imaginary upper envelope 72 maintains the same taper for both the frustoconical portion 74 and the cylindrical portion 73.

[0116] 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 end of the helix axially farthest from the free edge 19). In particular, the first male thread portion 18a and the second female thread portion 18b each include this incomplete portion 75 adjacent to the frustoconical portion 74, which frustoconical portion 74 is located between the incomplete portion 75 and the cylindrical portion 73. This incomplete portion 75 results in a smaller height of the thread, and the successive crests 60 of this incomplete portion are parallel and collinear with each other. The imaginary upper envelope 72 becomes parallel to the 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 71 has the same taper as observed in the frustoconical portion 74.

[0117] The presence of the cylindrical portion 73 makes it possible to limit the radial volume of the male threaded portion within the thickness of the wall forming the male tool joint. Thus, a greater minimum thickness can be ensured respectively at the level of the internal male sealing surface 25 and the intermediate male sealing surface 27. The sealing performance is improved by this configuration of the male threaded portion.

[0118] Furthermore, the presence of the cylindrical portion 73 adjacent to the frustoconical portion 74 makes it possible to avoid any sudden change in the stiffness of the male non-threaded internal portion 30. This configuration can avoid premature plasticization of the connecting piece area that bears the maximum stress.

[0119] The helix of the male threaded portion is such that the pitch SFLp of the insertion flank is constant in the frustoconical portion 74 and is also constant in the incomplete portion 75. In particular, the pitch in the frustoconical portion 74 and the incomplete portion 75 is the same. In the frustoconical portion 74 and the incomplete portion 75, the pitch LFLp of the insertion flank is the same, and this pitch LFLp is also equal to the pitch SFLp of the insertion flank.

[0120] For the first male threaded portion 18a, the pitch SFLp1 of the insertion flank and the pitch LFLp1 of the load-bearing flank are equal to a constant k1. Similarly, for the second male threaded portion 18b, the pitch SFLp2 of the insertion flank and the pitch LFLp2 of the load-bearing flank are equal to the same constant k1. According to the invention, this constant k1 is, for example, between 5 mm and 20 mm, preferably between 6 mm and 8 mm.

[0121] Preferably, the tooth width Wtp of the male threaded portion, which is defined as the measurement along the longitudinal axis X of the distance between the insertion flank SFp and the load-bearing flank LFp at the intersection point with the pitch line PL, is such that the width of the tooth is less than half of the constant kl, and in particular less than 40% of the value k1.

[0122] Figure 12 The frustoconical portion 94 is shown on two turns of the helix of the first female threaded portion 16a and the second female threaded portion 16b. The structure described below for the helix is replicated in at least several turns, at least 3 turns, while maintaining the dimensions, shapes and proportions listed below.

[0123] The helix of the female thread portion includes a load flank LFb, a thread crest 80, an insertion flank SFb, and a thread root 81. The crest 80 and the root 81 form a section parallel to the longitudinal axis X. The thread root 81 is connected to the insertion flank SFb by a recessed bending transition 82. The recessed bending transition 82 causes the thread root 81 and the insertion flank SFb to form an angle greater than 90°. In the same way as at the level of the male thread root 61, the thread root 81 may include a stepped portion having two staggered cylindrical portions 81a and 81b such that the cylindrical portion 81a adjacent to the recessed bending transition 82 is radially closer to the longitudinal axis X than the cylindrical portion of this thread root 81 adjacent to the load flank LFp.

[0124] The insertion 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 the end of the thread root 81 opposite to the end where the thread root is connected to the insertion flank SFb by a second recessed bending transition 84. The second recessed 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.

[0125] The angle 85 is equal to the angle 83 plus or minus a machining tolerance, i.e., ±0.25°.

[0126] The angle 85 is equal to the angle 65 plus or minus a machining tolerance, i.e., ±0.25°.

[0127] The angle 83 is equal to the angle 63 plus or minus a machining tolerance, i.e., ±0.25°.

[0128] The angle 83, for example, lies between 1° and 5°, preferably between 1.25° and 3.75°.

[0129] In Figure 13 more detail, the crest 80 is connected to the insertion flank SFb by a protruding bending transition 86. The bending transition 86 includes a tangential bending radius 86a tangent to the insertion flank SFb, a tangential bending radius 86c tangent to the crest 80, and a frustoconical surface 86b tangentially connected to the tangential connection portions 86a and 86c on either side. The frustoconical surface 86b forms an obtuse angle 86d with respect to the insertion flank SFb, for example, between 190° and 240°, preferably an opening angle of approximately 225°. The frustoconical surface 86b forms a chamfer that facilitates the insertion of the male tool joint into the female tool joint. The frustoconical surface 86b reduces the axial width of the crest 80 such that an additional volume is defined between the frustoconical surface 86b and the complementary profile of the male thread portion, and this volume also helps to reduce the grease pressure in the thread.

[0130] The crest 80 is connected to the load-bearing flank LFb by a compound convex surface 87 which includes a frustoconical portion 88 adjacent to the cylindrical portion of the crest 80, the frustoconical portion 88 being connected to the load-bearing flank LFb by a bending radius 89.

[0131] The radial height of the load-bearing flank LFb is greater than the radial height of the inserted flank SFb such that the female thread portion includes a frustoconical portion in a direction of a cone angle 90 relative to the longitudinal axis X along an imaginary line PL (pitch line) passing through the centers of the successive inserted flanks SFb and the load-bearing flank LFb of the helix.

[0132] The taper of this imaginary line is the same as the taper defined by the frustoconical portion 75 of the male thread portion, and these lines PL are superposed in the assembled position of the connector, as Figure 14 shown.

[0133] In this frustoconical portion 94 of the female thread portion, the helix is defined between the surfaces of two imaginary frustoconical envelopes 91 and 92 which are respectively parallel to the pitch line PL. The imaginary upper envelope 91 passes through the tangent point between the root 81 of each turn of the helix in the frustoconical portion 94 and the curved transition portion 82 adjacent to the inserted flank SFb. The imaginary upper envelope 92 passes through the tangent point between the protruding curved transition portion 86 adjacent to the inserted flank SFb and the crest 80.

[0134] The angle 90 is such that the taper of the female thread portion 16a and / or 16b is between 5% and 15%, preferably between 8% and 12%.

[0135] In addition to the above-mentioned frustoconical portion 94, the helix also includes an incomplete portion at the end of the helix, the incomplete portion 95 extending over more than one turn, preferably less than three turns, especially less than two turns. In the described embodiment, this end of the helix is provided on one side of the end of the female thread portion, which end is axially furthest 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 an incomplete portion 95 adjacent to the frustoconical portion 94 of the helix.

[0136] The incomplete portion 95 gives the thread a smaller height, and the successive crests 80 of the incomplete portion 95 are parallel and collinear with each other. The imaginary lower envelope 92 becomes parallel to the axis X in the incomplete portion 95. In the incomplete portion 95, the imaginary upper envelope 91 has the same taper as observed in the frustoconical portion 94.

[0137] In the assembled position of the male tool joint and the female tool joint, the incomplete portion 95 of the female thread portion meshes with the cylindrical portion 73 of the corresponding male thread portion.

[0138] In an embodiment according to the invention, the frustoconical portion 94 of the female thread portion includes more turns than the frustoconical portion 74 of the male thread portion. In fact, the incomplete portion 75 of the male thread portion engages in the frustoconical portion of the female thread portion in the assembled position of the connector.

[0139] In particular, the first male thread portion 18a may include more turns than the second male thread portion 18b.

[0140] In particular, the first female thread portion 16a may include more turns than the second female thread portion 16b.

[0141] In particular, the frustoconical portion 74 of the first male thread portion 18a may include more turns than the frustoconical portion 74 of the second male thread portion 18b.

[0142] In particular, the frustoconical portion 94 of the first female thread portion 16a may include more turns than the frustoconical portion 94 of the second female thread portion 16b.

[0143] The helix of the female thread portion is such that the pitch SFLb of the insertion flank is 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. In the frustoconical portion 94 and the incomplete portion 95, the pitch LFLb of the insertion flank is the same, and this pitch LFLb is also equal to the pitch SFLb of the insertion flank.

[0144] For the first female thread portion 16a, the pitch SFLb1 of the insertion flank and the pitch LFLb1 of the load flank are equal to a constant k2. Similarly, for the second female thread portion 16b, the pitch SFLb2 of the insertion flank and the pitch LFLb2 of the load flank are equal to the same constant k2.

[0145] According to the invention, the constants k1 and k2 are equal to each other, and they may also be represented by a constant term k. Given machining tolerances, within the meaning of the present invention, k1 is equal to k2 ± 0.05 mm.

[0146] Preferably, the tooth width Wtb of the female thread portion, which is defined as the measurement along the longitudinal axis X between the insertion flank SFb and the load flank LFb at the intersection point intersecting the pitch line PL, is such that the width of the tooth is greater than the tooth width Wtp of the frustoconical portion 74 of the male thread portion.

[0147] In practice, according to the invention and in the illustrated example, it is important that the teeth defining the male thread portion have a width smaller than that of the teeth of the female thread portion. For example, in the illustrated embodiment,

[0148]

Mathematical Formula 9

[0149]

[0150] and

[0151]

Mathematical Formula 10

[0152] Wtp + Wtb < k

[0153] Preferably,

[0154]

Mathematical Formula 11

[0155]

[0156] Even

[0157]

Mathematical Formula 12

[0158]

[0159] Since the teeth of the female thread part are larger than those of the male thread part, the teeth of the female thread have a smaller plasticization tendency. Now, in the connector according to the present invention, it is more clearly seen the stress in the region 99 extending between the first tooth on the side of the inner sealing surfaces 25 and 26 and the said sealing surfaces (see Figure 5 ).

[0160] On the side where the crest 60 is connected to the inserted flank SFp, the maximum shear line that can be modeled in the connector according to the present invention under a compressive load is shown to be at 45° with respect to the crest 60. And conversely, on the side where the crest 60 is connected to the load-bearing flank LFp, the maximum shear line that can be modeled in the connector according to the present invention under a tensile load is shown to be at 45° with respect to the crest 60. The intersection between these modeled shear lines enables the definition of a maximum stress triangle above each crest of the male thread part. These triangles locate the regions with the highest plasticization risk within the female tool joint. The inventors have found that in order to maintain the effectiveness of the connection, it is necessary to limit the height of these triangles, and thus the required ratio must be selected to limit plasticization in the female tool joint having a limited thickness due to the overall connection design.

[0161] In the assembled position, as Figure 14 shown, the load-bearing flanks LFp and LFb are in contact, and an axial clearance 100 is maintained between the inserted flanks SFp and SFb. Similarly, a radial clearance 101 is maintained between the crest 60 of the male thread part and the root 81 of the female thread part, while the imaginary lines 71 and 91 overlap as long as the crest 80 of the female thread part contacts the thread root 61 of the male thread part.

[0162] The radial clearance 101 can also limit the size of the maximum stress region in the female tool joint.

[0163] 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 clearances, the tooth width satisfies the following condition:

[0164]

Mathematical formula 13

[0165] Wtp + Wtb < k - 0.1 mm

[0166] Since the male thread part is cylindrical - conical, there is very little free volume remaining between the helices of the assembled male and female thread parts. When the connecting member according to the present invention is applied with make-up grease on the male tool joint and the female tool joint before its assembly, there is little available space to avoid an increase in the grease pressure inside the connecting member. According to the present invention, in the female thread part, particularly in the first female thread part 16a, an annular groove 110 is provided to be able to receive the excess grease flowing back. The advantage of this groove is that it allows local accumulation of grease during the make-up or use of the connecting member under certain temperature and pressure conditions. The annular groove is provided in the female thread part disposed between two sealing surfaces.

[0167] In the illustrated embodiment, when there is no seal between the free edge 17 of the female tool joint and the second female thread part, no annular groove is provided in the second female thread part.

[0168] In Figure 15 it, the annular groove 110 is defined between a hypothetical inner line 92 and an outer line 91. For example, the annular groove 110 has an axial width G of approximately a constant k. The groove 110 includes a frustoconical tooth bottom 111, which has the same taper as the female thread part. The annular groove is asymmetric. On one side of the tooth bottom 111, on the side of the inner sealing surface 26, the tooth bottom 111 is connected to a straight part 112, and the angle 113 between this straight part 112 and the normal N is between 10° and 30°. On the opposite side of the tooth bottom 111, on the side of the intermediate sealing surface 28, the tooth bottom 111 is connected to another straight part 114, and the included angle 115 between this straight part 114 and the normal N is between 30° and 85°.

[0169] When the connecting member is at a very deep depth and subjected to a temperature of about 180 °C, the groove can degas the grease without causing a temporary loss of seal or a risk of local plasticization of the connecting member.

[0170] The present invention is also applicable to a threaded connecting member between a male tool joint including a single thread part and a female tool joint also including a single thread part. These connecting members according to the present invention (not shown) may include one or two metal - metal seals and axial supports.

[0171] The present invention is also applicable to threaded coupling connectors.

Claims

1. A threaded tubular connector for drilling and / or producing oil and gas wells, said threaded tubular connector comprising a first pipe (12) equipped with a male tool joint (18) at a first distal end and a second pipe (14) equipped with a female tool joint (16) at a second distal end, said male tool joint (18) being capable of being assembled with said female tool joint (16) by screwing, said first pipe (12) being assembled to said second pipe (14), together defining a longitudinal axis, said male tool joint (18) comprising male thread portions (18a, 18b), said female tool joint (16) comprising female thread portions (16a, 16b) that engage with said male thread portions when assembling the connector, said male and female thread portions each comprising at least one helix equipped with a load flank, a thread crest, an insert flank, and a thread root, such that for at least two consecutive turns of the respective helices of said male and female thread portions, the pitch LFLp of the load flank and the pitch SFLp of the insert flank of said male thread portion and the pitch LFLb of the load flank and the pitch SFLb of the insert flank of said female thread portion satisfy the following conditions: 【Mathematical formula 14】 SFLp = LFLp = SFLb = LFLb = k Characterized in that, Along said longitudinal axis, in said at least two consecutive turns, the tooth widths (Wtp) of the helices of said male thread portions (18a, 18b) and the tooth widths (Wtb) of the helices of the corresponding female thread portions (16a, 16b) are such that: 【Mathematical formula 15】 50%< <80% or 【Mathematical formula 16】 50%< <80% and 【Mathematical formula 17】 Wtp + Wtb < k.

2. The threaded tubular connector according to claim 1, characterized in that, Satisfy the following mathematical formula conditions: 【Mathematical formula 18】 55%< <75%。 3. The threaded tubular connector according to claim 1 or 2, characterized in that, Satisfy the following mathematical formula conditions: 【Mathematical formula 19】 67%< <73%。 4. The threaded tubular connector according to claim 1, wherein, The tooth width (Wtp) of the helices of said male thread portions (18a, 18b) is between 2.5 mm and 3.5 mm.

5. The threaded tubular connector according to claim 1, characterized in that, The tooth width (Wtb) of the helices of said female thread portions (16a, 16b) is between 3.7 mm and 4.5 mm.

6. The threaded tubular connector according to claim 1, characterized in that, The tooth widths (Wtp, Wtb) of the helices of said male thread portions (18a, 18b) and the corresponding female thread portions (16a, 16b) satisfy the following conditions on said at least two consecutive turns of these helices: 【Mathematical formula 20】 Wtp + Wtb < k - 0.1 mm.

7. The threaded tubular connector according to claim 1, wherein The tooth widths of the complete helices of said male thread portions (18a, 18b) and the corresponding female thread portions (16a, 16b) satisfy the following conditions: for each turn (n), the tooth width (Wtpn) of said male thread and the tooth width (Wtbn) of said female thread are such that For each n: 【Mathematical formula 21】 Wtpn + Wtbn < k - 0.1 mm.

8. The threaded tubular connector according to claim 1, characterized in that, A part of said insert flank is parallel to a part of said load flank, wherein the tolerance of the inclination of these parts with respect to said longitudinal axis is ±0.25°.

9. The threaded tubular connector according to claim 1, characterized in that, The insert flanks and load flanks of the helices of said male thread portions (18a, 18b) are straight lines respectively and are connected to adjacent thread crests (60) and thread roots (61) through bending radii (62, 64, 66, 68).

10. The threaded tubular connector according to claim 1, characterized in that, The insert flank (SFb) of the helix of the female thread portion includes a straight section which is connected to the thread crest (80) by a section inclined with respect to the insert flank so as to form a convex surface such that the two sections form an angle (86d) between 190° and 260° therebetween.

11. The threaded tubular connector according to claim 1, wherein, The thread root (61) of the helix of the male thread portion (18a, 18b) includes two sections (61a, 61b): a first male thread root section (61a) which is located on one side of the insert flank; a second male thread root section (61b) which is located on one side of the load flank and such that the radial distance of the first male thread root section is equal to or greater than the radial distance of the second male thread root section, the radial distance being evaluated with respect to the thread crest (60) adjacent to the sections (61a, 61b) of the thread root (61) of the helix of the male thread portion.

12. The threaded tubular connector according to claim 1, wherein, The load flank of the helix of the male thread portion (18a, 18b) forms an angle with respect to the normal to the longitudinal axis, the angle being between 1° and 5°, and the load flank of the helix of the male thread portion (18a, 18b) is parallel to the load flank of the helix of the female thread portion (16a, 16b), wherein the tolerance of the inclination of these load flanks with respect to the longitudinal axis is + / −0.25°.

13. The threaded tubular connector according to claim 1, wherein The load flank of the helix of the male thread portion (18a, 18b) forms an angle less than or equal to 90° with the adjacent thread root of the helix.

14. The threaded tubular connector according to claim 1, wherein, The helix of the female thread portion (16a, 16b) is frustoconical.

15. The threaded tubular connector according to claim 14, wherein, The helix of the male thread portion (18a, 18b) includes at least one frustoconical portion, the taper of which is the same as the taper of the helix of the female thread portion (16a, 16b).

16. The threaded tubular connector according to claim 1, wherein, The pitch LFLp of the load flank and the pitch SFLp of the insert flank are between 5 mm and 20 mm.

17. The threaded tubular connector according to claim 16, wherein, The male thread portion (18a, 18b) and the corresponding female thread portion (16a, 16b) each include a single helix.

18. The threaded tubular connector according to claim 17, wherein The helix of the male thread portion (18a, 18b) and the corresponding female thread portion (16a, 16b) includes at least 3 turns.

19. The threaded tubular connector according to claim 18, wherein, The taper of the thread crest and the thread root of the male thread portion and the female thread portion is less than the taper of the thread portion.

20. The threaded tubular connector according to claim 19, characterized in that, The radial height of the insert flank of the male thread portion (18a, 18b) is greater than the radial height of the load flank of the male thread portion.

21. The threaded tubular connector according to claim 10, characterized in that, The angle is approximately 225°.

Images