EA040390B1 - PIPE SCREW CONNECTION - Google Patents

Description

The invention relates to the field of pipe threaded connections and couplings or assemblies of pipes connected by means of a thread.

In particular, the present invention relates to pipes used in industry, and, in particular, to assemblies or threaded joints used in pipeline strings for tubing, or for tubular production equipment, or for casing, or liner, or riser. for the exploitation, or exploration or development of oil or gas wells.

The threaded assembly described herein is particularly applicable to the assembly of metal pipes used in oil or gas well casing. The casing string is required to maintain the stability of the wellbore, prevent contamination of the aquifers, and control pressures in the wellbore during drilling, production and/or workover operations.

These casing pipes are manufactured from steel in accordance with API 5CT specifications for casing and tubing. For example, the steel may be one of the L80, P110, or Q125 grades.

Such threaded pipe connections are subjected to various combinations of stresses, which may vary in intensity or change direction, such as, for example: axial tension, axial compression, bending force from internal pressure, twisting force, etc. Thus, threaded pipe connections are designed to withstand these stresses, resist failure, and provide a tight seal.

Many types of oil and gas pipe assemblies are known to provide satisfactory results in terms of mechanical performance and tightness even under difficult operating conditions.

The first problem associated with casing strings for oil or gas wells is their installation in the well without damaging their internal and external surfaces. The casing strings are a series of pipes, the first string of pipes of the casing string having a larger outer diameter than the second string of pipes of the casing string intended to be connected to the first string, but installed deeper in the well. Casing strings are structurally designed so that as the depth of their stay in the well increases, their diameter gradually decreases. However, the transition must be smooth.

Thus, a new casing string having a specific outside diameter needs to be inserted into a previously installed casing string having a larger diameter and a specific inside diameter. In order to avoid damage to the inner surface of the casing already installed in the well, the outer diameter of the new row of casing must be controlled. The API standards provide guidance on this. Naturally, all rows of casing must also meet the efficiency requirement at each junction of two adjacent casing pipes. Connection efficiency, or bonding efficiency, is defined as the ratio of bond tensile strength to pipe tensile strength, a ratio that is evaluated under the most severe well conditions such as high external pressure, high internal pressure, high compression or high tension.

Known assemblies include pipes with male threads at both ends, assembled by couplings having two corresponding female threads. The advantage of this type of assembly is that it stiffens the two components of the assembly due to the positive thread interference created between the male and female threads.

However, the outer diameter of these sleeves is larger than the outer diameter of the respective pipes, and when these assemblies are used for casing pipes, the sleeves require a larger borehole to be drilled to accommodate the outer diameter of the sleeves.

To eliminate this disadvantage, assemblies without a coupling or adapter sleeve are usually used, referred to as semi-equal bore, equal bore or integral assemblies, or joints, or connections. Each of the tubular elements of these integral assemblies has one male end and one female end.

Integral assemblies are typically made on pipes having an appropriately sized end, suitably expanded OD at the female end and swaged OD at the male end, to provide a joint thickness sufficient to provide mechanical strength to the joint. Expansion and compression make the connection more efficient. Both help to minimize the maximum outside diameter and thus the minimum inside diameter at the joint. Thus, this connection allows to maintain a certain level of performance under displacement, to facilitate installation in the wellbore without damaging the existing casing string, and to meet the standard for a full bore or semi-straight integral connection. An equal bore connection is such that the outer diameter of the joint exceeds the nominal outer diameter of the pipes by about 1%; for a half-way connection, this value is approximately 2-3%.

Reference may be made to WO 2014/044773 which describes an integral semi-equal to threaded tubular connection comprising a first tubular having a tubular male end and a second tubular having a tubular female end. Each of the female and male ends contains two taper threads in the axial direction and an eccentric seal. The purpose of this document is to improve the performance of the connection in tension by providing a specific ratio between the areas of critical sections.

However, in this industry, the tolerances for the target size of the nominal diameter, the swaging and expansion process, and the ovality tolerances, are such that it may happen that in some cases, due to deflection of the free end (tip end) of the female end when making up the connection, the outer diameter female free end can locally create an outer sharp annular edge. The same can occur due to deflection of the free end (terminal end) of the male end when making the connection: the inner diameter of the male free end can locally create an internal sharp annular edge. Thus, when installing a tubing into a casing string or one casing string into another casing string, friction can occur between this sharp annular edge and the additional tubing or casing string. Friction can cause premature casing or tubing failure, even premature production wear. Friction can lead to poor sealing efficiency.

Thus, there is a need to improve integral threaded tubular connections to improve both the sealing efficiency and the tensile strength of the connection, while improving the wear resistance of the tubing and casing.

One aim of the present invention is to overcome these disadvantages.

It is a specific object of the present invention to provide a threaded pipe joint capable of absorbing axial and radial loads, as well as withstanding radial deformation that can occur under high radial loads, while being compact, especially in the radial direction.

The threaded pipe connection according to the present invention comprises a pipe female end extending from the main body of the first tubular element, this pipe female end having a female male thread between the female shoulder and the female free end; and a female female thread, wherein the female shoulder is a female intermediate shoulder located between the female male thread and the female female thread;

a tubular male end extending from the main body of the second tubular element, this tubular male end contains a male male thread, a male female thread and a male shoulder, said male male thread is adapted for mutual blocking by thread engagement with a female male thread, said male female thread is adapted for interlocking by thread engagement with the female female thread, and wherein the tubular female end comprises a first machined outer surface of the female end next to the female free end, the second outer diameter (JOB2) is higher than at least one thread root of the female female thread, whereby the second the outer diameter (JOB2) is larger than the first outer diameter (JOB) of the first machined outer surface, and the female free end is not in axial contact with the pipe long male end.

According to the present invention, the female free end may flex slightly during make-up due to the absence of any axial abutment to the tubular male end during make-up. The female free end is longitudinally spaced from any part of the tubular male end when the connection is screwed.

Preferably, the first machined outer surface may extend above at least one thread root of the female male thread. The second outer diameter (JOB2) of the tubular female end may be located above the intermediate shoulder.

For example, an outer surface of a tubular female end having a larger outer diameter than the first outer diameter (JOB) may extend at least over a portion extending from the first critical cross-section of the box-like element (BCCS1) to the second critical cross-section of the box-like element (BCCS2, BCCS3) tubular female end.

Advantageously, the second outer diameter (JOB2) may be constant over the second cylindrical surface, and the first machined outer surface comprises a cylindrical surface defined by this first outer diameter. The outer surface of the pipe

- 2 040390 female end, having a larger outer diameter than the first outer diameter (JOB), may not be exclusively cylindrical, it may also have an externally frustoconical part, a cylindrical part and/or an internally frustoconical part.

For example, the second cylindrical surface may extend above the intermediate shoulder and/or above the second critical cross-section of the box-like element (BCCS2) located in the first root of the engaged thread of the female female thread adjacent to the internal shoulder and/or above the portion of the female female thread, whereby the first the machined outer surface extends above the female male thread portion.

The tubular female end may further comprise a female outer sealing surface, and accordingly the tubular male end may comprise a male outer sealing surface, whereby the male and female outer sealing surfaces form an external metal-to-metal seal when the threaded pipe connection is screwed, whereby the outer diameter of the female pipe the end above this female outer sealing surface is equal to the first outside diameter (JOB). Thus, the female outer sealing surface can be located between the female male thread and the female free end. Alternatively, the female outer sealing surface may be located between the female male thread and the intermediate shoulder.

According to one embodiment of the present invention, the male free end may be longitudinally spaced from the inner shoulder when the connection is screwed. Preferably, the female intermediate shoulder and the male intermediate shoulder can abut each other when the connection is screwed.

Male and female threads, respectively external and internal, can preferably be radially offset relative to the longitudinal axis of the threaded connection. Thus, even with the same taper angle of both the male and female threads, the conical envelope of the female male thread will not coincide with the conical envelope of the female female thread.

Preferably, the machined outer surface of the female end and the cylindrical surface having said second outer diameter (JOB2) can be connected to a tapered surface forming a fit angle α2 of 1 to 10°, preferably 5 to 7°, such as 6° .

The cylindrical surface having said second outer diameter (JOB2) can be connected to the main body of the first tubular element having a nominal outer diameter (OD) with a tapering surface forming an opening angle α1 of 2 to 5°, for example equal to 3° .

The tubular female end may further comprise a female inner sealing surface, the tubular male end may respectively comprise a male inner sealing surface, wherein the female inner sealing surface is located between the female female thread and the inner shoulder, the male inner sealing surface is located between the male female thread and the male free end , whereby the male and female internal sealing surfaces form an internal metal-to-metal seal when the threaded pipe connection is screwed.

According to one embodiment of the present invention, the tapering surface with opening angle α1 may extend above the groove located between the female female thread and the female inner sealing surface.

Preferably, the difference (JOB2-JOB) of the second outer diameter (JOB2) and the first outer diameter (JOB) can be set to between 30% and 130% of the diametral interference of the outer metal-to-metal seal, preferably between 25% and 115% of the maximum diametral interference, at In this case, this maximum diametral interference is the highest value among the diametral interference of the male thread, internal metal-to-metal seal, and external metal-to-metal seal.

The ratio (JOB2/OD) of the second outer diameter (JOB2) and the nominal outer diameter of the main body of the first tubular may be from 100.5% equal bore to 104%, preferably from 101.0 to 103.5%, even more preferably from 101 .5 to 102.5%, for example equal to 102.3%.

Due to the advantage of the specific design of the present invention, after threaded engagement of the female pipe end with the male pipe end at the end of the make-up of the threaded pipe connection, the external diameter of the female pipe end in both places above the male thread and the female thread remains less than the same threshold value of 105%, and preferably less than 103% of the nominal outer diameter of the main body.

- 3 040390

The present invention and its advantages will be better understood by reading the detailed description of specific embodiments given as non-limiting examples and illustrated by means of the accompanying drawings, in which FIG. 1 is a partial cross-sectional view of a threaded connection in accordance with one embodiment of the present invention in the connected state;

fig. 2 is a partial cross-sectional view of the female tubular shown in FIG. 1;

fig. 3 is a partial cross-sectional view of the male tubular shown in FIG. 1; and fig. 4 is a partial cross-sectional view of a threaded connection according to a second embodiment of the present invention in a connected state;

fig. 5 and 6 are partial cross-sectional views of a threaded connection in accordance with alternatives of a particular embodiment of the present invention in the connected state;

fig. 7 is a schematic view of the deflection of the female tubular shown in FIG. 2 after make-up with the male tubular shown in FIG. 3.

For clarity, the sectional views are partial in the sense that they are sectional views along a plane transverse to the longitudinal axis X-X' of the tubular, and only one of the two sections of the tubular is shown.

One embodiment of a threaded pipe connection 10 having a longitudinal axis X-X' is illustrated in FIG. 1; the specified threaded pipe connection 10 contains the first pipe element 22 and the second pipe element 32 with the same longitudinal axis X-X' in the connected state.

The first tubular element 22 is made with a main body 21, referred to as a female main body, and a tubular female end 20, referred to as a box element. The box element 20 extends from the female main body 21. The box element 20 includes a terminal end 25 of said first tubular element 22. The terminal end 25 represents the female free end of the box element 20. The female main body 21 has a nominal outer diameter that is substantially constant along its length. of this main body 21 along the axis XX'. Preferably, the internal nominal diameter ID of this female main body 21 is essentially constant along the length of this main body 21 along the axis XX'.

The second tubular 32 is provided with a main body 31, referred to as the male main body, and a male tubular end 30, referred to as the pin. The pin 30 extends from the male main body 31. The pin 30 forms the end end 35 of said second tubular 32. The end 35 is the male free end of the pin 30. The male main body 31 has a nominal outside diameter that is substantially constant along its length. of this main body 31 along the axis XX'. Preferably, the internal nominal diameter of this male main body 31 is substantially constant along the length of this main body 31 along the axis XX'.

The main bodies 21 and 31 have the same nominal inside diameter ID and nominal outside diameter OD and hence the same pipe width. Preferably, both the outer nominal diameter OD and the inner nominal diameter ID of the main bodies 21 and 31 are substantially constant along the length of these main bodies 21 and 31 along the axis XX'.

Threaded pipe connection 10, as shown, is an integral connection, as opposed to assemblies or couplings using a coupling or adapter sleeve. The expanded zone of the first tubular element 22, having a larger outer diameter than the nominal outer diameter of the main bodies 21 and 31, forms a box-shaped element 20. The swaged zone of the second tubular element 32, which has a smaller diameter compared to the nominal inner diameter of the male main body 24, forms a nipple element 30.

In order to make such a female end, the first tubular element is first expanded using, for example, cold forming techniques, to increase the outside diameter of the entire box element and obtain a conical tapered outer surface 80 forming an angle α1 between 3 and 4°, for example equal to 3° , with an outer cylindrical surface of the enclosing main body 21.

In order to make such a male end, the second tubular is first crimped using, for example, cold forming techniques to reduce the internal diameter of the entire pin and obtain a conical inner surface 90 forming an angle α3 between 3 and 4°, for example equal to 3°, with an inner cylindrical surface of the male main body 31.

The threaded pipe connection 10 may be a threaded equal bore or semi-full bore integral joint.

As illustrated in detail in FIG. 2, the free end 25 is preferably an annular surface extending perpendicular to the axis XX'. The box element 20 contains

- 4 040390 on its inner profile, the female outer sealing surface 27 and the female outer thread 26, while the female outer sealing surface 27 is located between the female free end 25 and the female external thread 26. relative to the female external thread 26.

The female threaded section 23 extends between the female shoulder 24 and the female free end 25.

In accordance with FIG. 1, 2, and 4, the box-shaped element 30 further comprises a female female thread 28, a female internal sealing surface 29, and an additional shoulder 18 - said inner shoulder 18. The female shoulder 24 is located between the female male thread 26 and the female female thread 28, while the female female the sealing surface 29 is located between the female female thread 28 and the inner shoulder 18. The inner shoulder 18 is connected to the joint surface 81 formed between the inner shoulder 18 and the female main body 21. In accordance with these embodiments, the female threaded section 23 is a female external threaded section 23, while the female female thread 28 is located on the female female thread 43 formed between the female shoulder 24 and the inner shoulder 18.

The inner profile of the box member 20 is machined on the inner surface after expansion. The outer profile of the nipple element 30 is machined on the outer surface after compression.

Female male and female threads 26 and 28 are offset in the radial direction and separated by a female shoulder 24 in the axial direction. The female shoulder 24 preferably extends as an annular surface perpendicular to the axis XX'.

Female male and female threads 26 and 28 are provided on a tapered surface, for example with a taper between 1/19 and 1/8, preferably between 1/18 and 1/16. More specifically, the angle of taper between the taper axis of the female threads and the longitudinal axis XX' of the joint is approximately 10°, so that the inner diameter of the box-like element 20 decreases from the free end 25 towards the female main body 21.

Female male and female threads 26 and 28 may have the following features: the same pitch, the same negative flank angle, the same trapezoidal tooth profile, the same longitudinal length.

The thread shape of each of the threaded portions will not be described in detail. Each tooth of the threads may typically have a tap side, a back side, a crest face, and a root face. The teeth of both threaded sections can be oblique, wherein the tuck sides have a negative angle and the tuck sides have a positive angle, or the tuck sides have a positive angle and the tuck sides have a negative angle. Alternatively, the teeth of both threaded portions may be trapezoidal teeth.

Preferably, the threads of both threaded portions are not wedge-shaped. Wedge-shaped threads, regardless of the specific thread form, are characterized by the use of turns that increase in width in one direction.

Preferably, the threads according to the present invention have bearing sides and insert sides with exactly the same pitch and lead.

Preferably, the threads of the present invention provide a diametrical interference.

The female male and female threads 26 and 28 are adapted to interlock by thread engagement with the respective components of the pin element 30. The mutual interlock by thread engagement ensures that at least 2 and preferably at least 3 turns of the female thread engage in the helical groove, passing between the corresponding 2-3 turns of the male thread. Seen in longitudinal section, along the axis XX', each tooth of the male thread is located between two adjacent teeth of the female thread, which can be observed for at least 3 turns of the threaded section.

Thus, as illustrated in detail in FIG. 3, the nipple element 30 comprises in succession from the male free end 35 on its outer profile: a male internal sealing surface 39, a male internal thread 38, a male shoulder 34, a male external thread 36, a male external sealing surface 37 and a contact surface 91 with the male main body 31. The male threaded portion 33 extends between the interface 91 and the male shoulder 34. According to the embodiments of FIG. 1-4, the male threaded portion 33 is the male male threaded portion 33, while the male female thread 38 is on the male female threaded portion 53 formed between the male shoulder 34 and the male free end 35.

According to the present invention, the male free end 35 does not abut against the tubular female end when the connection is screwed.

The male and female threads 36 and 38 are radially offset and axially separated by a male shoulder 34. The male shoulder 34 preferably extends as an annular surface perpendicular to axis XX'.

The female male and female threads 26 and 28 are adapted to interlock by thread engagement respectively with the male male and female threads 36 and 38 so that they respectively taper at the same taper angle. The male and female threads 36 and 38 have the same pitch and lead as the male and female threads 26 and 28, respectively.

In accordance with the first embodiment of the present invention, each of the female external and internal threads 26 and 28 contains a leading part 26a and 28a, respectively, on the side closest to the female main body 21, and an outgoing part 26b and 28b, respectively, on the opposite side.

Each of the male and female threads 36 and 38 has a leading part 36a and 38a, respectively, on the side closest to the male main body 31, and an outgoing part 36b and 38b, respectively, on the opposite side. Each male part 26a and 28a respectively on the box element 20 engages with the output part 36b and 38b respectively on the pin element 30, and each male part 36a and 38a respectively on the pin element 30 engages with the outgoing part 26b and 28b respectively on the box element 20. the thread and the output thread are not ideal in the sense that they do not have the full height observed for the threaded part between the respective male and female parts.

As shown in FIG. 1-4, the female and male threads contain the specified incoming and outgoing parts. According to one alternative, not shown, the connection may contain only full height threads.

In the screwed-on state of the joint 10, the first engagement thread root of the female thread is the position of the first thread cavity, if successive thread roots are considered, starting from the female male and female thread engagement 26a or 28a, where the corresponding thread of the male thread 36 or 38 engages. that, in the screwed state, at least part of the bearing side of the female thread is in contact with the corresponding bearing side of the male thread. Considering successive thread cavities, starting with the engagement portions 26a and 28a respectively, the first position of the contact face of the female thread is adjacent to the first engaged thread cavities of the female male thread and respectively the female female thread.

In the screwed state of connection 10, the first engaged thread root of the male thread is the position of the first thread root, if successive thread roots are considered, starting from the leading part 36a or 38a of the male male and female threads, respectively, where the corresponding thread of the female thread 26 or 28 engages. that, in the screwed state, at least part of the bearing side of the male thread is in contact with the corresponding bearing side of the female thread. Considering successive thread cavities, starting with the engagement portions 36a and 38a respectively, the first position of the contact side of the male thread is adjacent to the first engagement thread cavity of the male male thread and, respectively, the male internal thread.

In accordance with FIG. 1 and 4, the first engagement thread root of the female male thread is located in the engagement portion 26a, and the first engagement thread cavity of the female female thread is located in the engagement portion 28a. Accordingly, the first engagement thread root of the male male thread is located in the engagement portion 36a, and the first engagement thread cavity of the male internal thread is located in the engagement portion 38a.

The following cross-sections are sections of the box element and the nipple element, respectively, transverse to the axis XX', and are respectively named:

BCCS1 - section of the box element in the first root of the engaged thread of the female male thread,

BCCS2 - section of the box element in the first root of the engaged thread of the female female thread,

PCCS1 - section of the pin element in the first root of the engaged thread of the male internal thread,

PCCS2 is the section of the pin element in the first root of the engaged thread of the male male thread.

As shown in FIG. 1-4, BCCS1 is in the lead 26a; BCCS2 is in the leading part 28a; PCCS1 is located in the leading part 38a; and PCCS2 is in the leading part 36a. Thus, BCCS1 is closer to the female shoulder 24 than to the female free shoulder.

end 25. BCCS2 is closer to the female inner sealing surface 29 than to the female shoulder 24. PCCS1 is closer to the male shoulder 34 than to the male free end 35, and PCCS2 is closer to the male outer sealing surface 35 than to the female shoulder 24. covered shoulder 34.

The critical cross section of the box element is the cross sectional area of the box element 20 undergoing maximum tension transmitted through all threads and determines the effectiveness of the connection. The critical cross-section of the pin element is the cross-sectional area of the pin element 30 undergoing full tension transmitted through all threads and determines the effectiveness of the connection. Typically, the connection is made so that the critical cross section of the box element is in general 95-105% of the critical cross section of the pin element.

In accordance with the embodiments shown in FIG. 1-4, with two threaded sections 23, 43 and 33 and 53 respectively, the critical cross section of the box element can be evaluated by BCCS1 and BCCS2, and accordingly the critical cross section of the pin element can be evaluated by PCCS1 and PCCS2. Alternatively, the critical cross section of the box element and the critical cross section of the pin element may be defined elsewhere.

For example, according to FIG. 2, the critical cross-section of the box-like member can be determined at location BCCS1 and at another cross-section BCCS3 perpendicular to axis XX' in the groove 50 formed between the female thread 28 and the female sealing surface 29. For example, according to FIG. 3, the critical cross-section of the pin element can be determined at PCCS1 and at another cross-section PCCS3 perpendicular to axis XX' in the groove 52 formed between the male male thread 36 and the interface 91.

As illustrated, the female outer sealing surface 27 is conical and the male outer sealing surface 37 is conical. The taper of the conical surfaces 27 and 37 may be between [10; 60%], for example equal to 20 or 50%. Alternatively, the taper of the conical surfaces 27 and 37 may be mismatched. In the screwed state of connection 10, the female and male outer sealing surfaces 27 and 37 create a metal-to-metal seal.

The female inner sealing surface 29 is a convex convex surface, such as a toroidal surface, defined by a torus radius of 10 to 100 mm, such as 60 mm; and the male inner sealing surface 39 is tapered, for example with a taper ranging from 10% to 60%, for example equal to 20% or 50%. Both ends of the convex convex surface of the female inner sealing surface 29 may be on a line forming an angle with the axis XX', such that this angle is equal to the angle of the conical male inner sealing surface 39 with the axis XX'. In the screwed state of connection 10, female and male inner sealing surfaces 29 and 39 create a metal-to-metal seal. Alternatively, the outer and inner metal-to-metal seals may both be of the cone-to-cone type with substantially the same taper. Alternatively, the female and male outer sealing surfaces 27 and 37 may form a metal-to-metal torus-cone seal.

To achieve a metal-to-metal seal, a diametrical interference is required between the female and male sealing surfaces. The amount of diametrical interference is the maximum difference between the outer diameter of the male sealing surface and the inner diameter of the female sealing surface, the diameters being considered at the same place along the axis XX', in the make-up state of the connection, but these diameters are diameters before make-up. The diametral interference is determined prior to make-up based on the finite element analysis and the predicted final position of the respective pin in the box element at the end of make-up.

For example, the diametral interference of an external metal-to-metal seal is between 0.5 and 1.7 mm; preferably between 0.7 and 1.45 mm, and even more preferably between 0.81 and 1.33 mm. For example, the diametral interference of an internal metal-to-metal seal is between 0.5 and 1.7 mm; preferably between 0.7 and 1.45 mm, and even more preferably between 0.81 and 1.22 mm. For example, the diametral interference of the inner metal-to-metal seal is set to be less than the diametral interference of the outer metal-to-metal seal. However, alternatively, the diametral interference of the inner metal-to-metal seal may be set equal to the diametral interference of the outer metal-to-metal seal.

Deflection of the box free end 25 on the outside of the joint caused by the outer metal-to-metal seal and deflection of the nipple free end 35 inside the joint caused by the inner metal-to-metal seal are limited by specific features of the invention.

In this specification, unless otherwise indicated, all outside diameter and inside diameter dimensions are considered before make-up, as they are after machining. Due to manufacturing tolerances, all dimensions are specified with tolerances of +/-0.2 mm

- 7 040390 compared to the target value.

Advantageously, the outer surface of the box element 20 is partially machined. Above the female outer sealing surface 27, the box-shaped member is machined to provide a locally cylindrical surface 58 with a first outer diameter JOB. Cylindrical surface 58 is cylindrical within the machining tolerances of metal parts.

The machined cylindrical surface 58 extends on both sides of the female outer sealing surface 27. In all embodiments, the cylindrical surface 58 extends from the female free end 25 to the female male thread portion 26. The cylindrical surface 58 has a first outer diameter JOB.

In accordance with the present invention, the second outer diameter JOB2 is defined at a location above at least one thread root of the female female thread 28.

All additional ratios or differences below are considered based on the target value of each outer diameter or inner diameter.

For example, the ratio (JOB/OD) of the first outer diameter JOB and the nominal outer diameter OD is between 100.5% and 103.5%, preferably between 100.8% and 103.2%, such as 101.97%.

The cylindrical portion 58 is connected to an outwardly tapering surface 82 forming an angle .alpha..sub.2 with the axis XX'. The angle α2 is between 5 and 7°, eg 6°. The outwardly tapering surface 82 is connected to another cylindrical surface 60 with an outer diameter equal to the second outer diameter JOB2. The conical tapering outer surface 80 with angle α1 directly abuts the second cylindrical surface 60 with the second outer diameter JOB2. The second cylindrical surface 60 has a length along the axis XX' equal to at least half the length, and preferably less than 150% of the length, of the first machined cylindrical surface 58, preferably from 70 to 100% of the length of the first machined cylindrical surface 58.

The ratio (JOB2/OD) of the second outer diameter JOB2 and the nominal outer diameter OD is between 100.5 and 104%, preferably between 101.0 and 103.5%, even more preferably between 101.5 and 102.5%, for example, it is equal to 102.3%.

The ratio (JOB2/JOB) of the second outer diameter JOB2 and the first outer diameter JOB is between 100.05% and 101%, preferably between 100.1% and 100.4%, for example 100.32%.

As shown in FIG. 1 and 2, the barrel 58 extends from the free end 25 to a location above the male thread 26 away from the BCCS1 location. A cylindrical surface 60 with a constant diameter equal to the second outside diameter of JOB2 extends above the intermediate shoulder 24 and up to the location BCCS2. According to this embodiment, the outwardly tapering surface 82 extends above the BCCS1 site. The tapered tapered outer surface 80 extends from the BCCS2 to the main body 21, extending over the groove 50, enclosing the inner sealing surface 29 and the inner shoulder 18 and beyond.

In FIG. 4 shows another embodiment of the present invention, slightly different from the embodiment of FIG. 1-3 in the sense that the tapered tapering outer surface 80 extends from the BCCS2 to a location which is between the female inner sealing surface 29 and the inner shoulder 18 about the axis XX'.

Fig. 5 differs from the embodiments in FIG. 1-4 in the sense that the male metal-to-metal seal is located between the female male thread 26 and the intermediate shoulder 24. In accordance with a specific embodiment in FIG. 5 and 6, the female and male outer sealing surfaces 27' and 37', respectively, may also be referred to as female and male intermediate sealing surfaces 27' and 37', respectively. The female outer sealing surface 27' is located between the female male thread 26 and the female female thread 28, and preferably between the female male thread 26 and the intermediate shoulder 24. Accordingly, the male outer sealing surface 37' is located between the male male thread 36 and the male female thread 38, and preferably between the male male thread 36 and the intermediate shoulder 34.

In the embodiment of FIG. 5, a cylindrical portion 58 extends from the free end 25 to above the outer metal-to-metal seal 27', with the tapered portion 82 extending at least above the intermediate shoulder 24. The cylindrical portion 60, with a constant diameter equal to the second outer diameter J0B2, is located along at least above the outgoing portion 28b of the female female thread 28. Referring to FIG. 5, the cylindrical portion 60 extends over the portion of the female internal thread 28, while the tapered portion 80 extends and ends in front of the location above the inner metal sealing surface 29, the inner metal sealing surface 29 being formed at a location where the outer diameter is equal to

- 8 040390 min outside diameter.

In the embodiment of FIG. 6, an alternative embodiment in FIG. 5, the cylindrical portion 58 extends from the free end 25 to a location above the male thread 26 away from the BCCS1 location, with both the BCCS1 location and the outer metal sealing surface 27' below the tapered portion 82. Referring to FIG. 6, a cylindrical portion 60 extends over a portion of the female female thread 28, while a tapered portion 80 extends at least over the inner metal sealing surface 29.

The female free end 25 does not have any contact with any part of the tubular male end in the screwed state. As shown in FIG. 1 and 4, the female free end 25 faces the interface 91 located between the male end and the male main body 31, but the free end 25 remains at a non-zero distance from this interface 91 in the screwed state. As shown in FIG. 5 and 6, the joint surface 91 is not represented, the female free end does not contact any part of the tubular male end in the screwed state. According to the present invention, the female free end 25 does not abut against the tubular male end when the connection is screwed.

The present invention may also be carried out in combination with a particular external design of the box element, a special design of the pin element.

Advantageously, the inner surface of the pin element 30 is partially machined. Below the male inner sealing surface 39, the pin member is machined to locally provide a first machined inner cylindrical surface 68. The inner cylindrical surface 68 is cylindrical within the machining tolerances of metal parts.

The machined inner cylindrical surface 68 extends on both sides of the male inner sealing surface 39. In accordance with the embodiments of FIG. 1-4, the inner cylindrical surface 68 extends from the male free end 35 to a portion of the male female thread 38. The inner cylindrical surface 68 has a first inside diameter JIP. In accordance with the present invention, the second inside diameter JIP2 is defined at a location above at least one thread root of the male male thread 36, wherein the second inside diameter JIP2 is less than the first inside diameter JIP of the first machined inside surface 68.

The inner cylindrical surface 68 is connected to an inwardly tapering surface 92 forming an angle .alpha..sub.4 with the axis XX'. The angle α4 is between 5 and 7°, eg 6°. The inwardly tapering surface 92 is connected to another inner cylindrical surface 70 having a constant diameter equal to the second inner diameter JIP2. The tapered tapering inner surface 90 obtained by the swaging process, with an angle α3, directly abuts the second inner cylindrical surface 70 with the second inner diameter JIP2. The second inner cylindrical surface 70 has a length along the axis XX' equal to at least half the length, preferably less than 150% of the length, of the first machined inner cylindrical surface 68, preferably from 70 to 100% of the length of the first machined inner cylindrical surface 68.

For example, the ratio (JIP/ID) of the first inner diameter (JIP) and the nominal inner diameter (ID) of the second tubular 31 is between 98% and 101.5%, preferably between 98.5 and 100.5%, even more preferably between 99.2 and 100.3%, for example equal to 99.73%.

The ratio (JIP2/ID) of the second inner diameter (JIP2) and the nominal inner diameter of the main body of the first tubular is between 98.5 and 100%, preferably between 98.9 and 99.9%, for example 99.3%.

The ratio (JIP2/JIP) of the second inner diameter (JIP2) and the first inner diameter (JIP) is between 99 and 99.9%, for example 99.5%.

As shown in FIG. 1, 3 and 4, the inner barrel 68 extends from the male free end 35 to a location above the female thread 38 away from the PCCS1 location. A second inner cylindrical portion 70 with a constant diameter equal to the second inner diameter JIP2 starts at PCCS1 and extends to a location above the male male thread 36, between PCCS2 and the midpoint of the male male thread along axis XX'. According to this embodiment, the inwardly tapering surface 92 extends over several, i. 1-4 threads of female thread 38, for example. The tapered tapered inner surface 90 connects directly to the second inner cylindrical surface 70 and terminates below the male male thread 36. The nominal inside diameter ID is defined below the interface 91 between the male end and the male main body 31, with the male outer sealing surface 27 and the groove 52 formed between the male outer sealing surface 37 and the outer thread 36.

As shown in FIG. 1-4 if the nominal outer diameter OD is 355.6mm and the nominal

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Claims (13)

the inner diameter ID is 313.94 mm, the length of the first cylindrical outer surface 58 is between 98 and 109 mm; the length of the second outer cylindrical surface 60 is between 83 and 87 mm; the first outer diameter J0B2 is between 363.52 and 364.02 mm; the first outer diameter of the JOB is between 362 and 363 mm, preferably between 362.36 and 362.86 mm; the first inner diameter of the JIP is between 313 and 313.8 mm, preferably between 313.12 and 313.37 mm; the second inner diameter of JIP2 is between 311 mm and 312.5 mm, preferably between 312 and 312.25 mm; the length of the first inner cylindrical surface 68 is between 88 and 100 mm, preferably between 89.75 and 99.75 mm; the length of the second inner cylindrical surface 70 is between 77 and 80 mm; the diametral interference of the outer metal-to-metal seal is between 1.12 and 1.32 mm, so that the difference (JOB2-JOB) of the second outer diameter of JOB2 and the first outer diameter of JOB is between 85 and 90% of the diametrical interference of the outer metal seal -metal; the diametral interference of the inner metal-to-metal seal is between 1.23 and 1.33 mm, so that the difference (JIP-JIP2) of the first inner diameter JIP and the second inner diameter JIP2 is between 91% and 116% of the inner seal diametrical interference value metal-metal; diametrical interference of the external thread, if any, is between 0 and 0.18 mm; the diametrical interference of the external thread, if any, is between 0 and 0.18 mm. In accordance with the embodiments of FIG. 1-4, the length along the X-X' axis of the second inner cylindrical surface 70 is less than the length of the second outer cylindrical surface 60. When the connection is made up, the profile of the inner diameter of the pin and the outer diameter of the box element change due to the forces resulting from the interference fit of the respective female and male sealing surfaces of the box and pin elements and the engagement of the threads. Fig. 7 is a view of the outside diameter at the nose of the box after make-up. Due to the make-up forces, the first cylindrical outer surface 58 is no longer cylindrical, but has taken on a slightly conical shape, with a maximum outer diameter near the free end 25 and a smaller diameter at the junction with the outwardly tapering surface 82. In all places along the cylindrical surface 58 and the second outer cylindrical surface 60, the outer diameter of the connection 10 remains less than the threshold value. Due to the special feature of having both first and second cylindrical outer surfaces 58 and 60, there is no direct radial contact with the box nose and casing already in place at installation. Indeed, the thickness of the box element 20 at the second critical cross section BCCS2 allows the box element to provide better casing wear resistance while providing high connection efficiency. Similarly, due to the make-up forces, the first cylindrical inner surface 68 is no longer cylindrical, but takes on a slightly conical shape with a minimum internal diameter near the male free end 35 and a larger diameter at the junction with the inwardly tapering surface 92. At all locations along the inner cylindrical surface 68 and the second inner cylindrical surface 70, the inner diameter of the joint 10 remains above a threshold value, such as a bore diameter. Due to the specific feature of having both first and second cylindrical inner surfaces 68 and 70, there is no direct radial contact with the nose of the pin and another casing string to be installed in the well. Indeed, the thickness of pin 30 at the first critical cross section of PCCS1 allows the pin to provide better casing wear resistance while providing high connection efficiency. With the extra thickness at the critical cross sections of the box and pin, the connection provides greater casing wear resistance while providing higher efficiency and performance when the connection is subjected to axial tension. The service life of the joint is also increased because the free end of the box element is not in direct radial contact. CLAIM 1. A threaded pipe connection (10) containing a pipe female end (20) extending from the main body (21) of the first tubular element (22), this female pipe end (20) contains - 10 040390 female male thread (26) between female shoulder (18, 24) and female loose end (25); and a female female thread (28), wherein the female shoulder (24) is a female intermediate shoulder located between the female male thread (26) and the female female thread (28); tubular male end (30) extending from the main body (31) of the second tubular element (32), this tubular male end (30) contains a male external thread (36), a male internal thread (38) and a male shoulder (34) specified the male external thread (36) is adapted for mutual interlocking by thread engagement with the female external thread (26), the specified male internal thread (38) is adapted for mutual interlocking by means of thread engagement with the female internal thread (28), and at the same time, the pipe female end ( 20) comprises a first machined outer surface (58) of the female end (20) next to the female free end (25), a second outer diameter (JOB2) above at least one thread root of the female female thread (28), whereby the second outer diameter (JOB2) is greater than the first outer diameter (JOB) of the first machined outer surface (58), and wherein the female free end is not in axial contact with the tubular male end, and the female free end is longitudinally spaced from any part of the tubular male end when the connection is screwed. 2. Threaded pipe connection according to claim 1, characterized in that the ratio (JOB/OD) of the first outer diameter JOB and the nominal outer diameter (OD) of the male main body is from 100.5 to 103.5%, preferably from 100.8 up to 103.2%, for example, equal to 101.97%. 3. Threaded pipe connection according to claim 1 or 2, characterized in that the first machined outer surface (58) extends above at least one thread root of the female male thread (26). 4. Threaded pipe connection according to any one of the preceding claims, characterized in that the second outer diameter (JOB2) of the female pipe end is located above the intermediate shoulder (24). 5. A threaded pipe connection according to any of the preceding claims, characterized in that the outer surface of the female pipe end, having a larger outer diameter than the first outer diameter (JOB), passes at least over a part extending from the first critical cross section of the box element ( BCCS1) to the second critical box section (BCCS2, BCCS3) of the tubular female end. 6. Threaded pipe connection according to any of the preceding claims, characterized in that the second outer diameter (JOB2) is constant over the second cylindrical surface (60) and the first machined outer surface (58) contains a cylindrical surface defined by this first outer diameter. 7. Threaded pipe connection according to claim 5, characterized in that the second cylindrical surface (60) extends above the intermediate shoulder. 8. Threaded pipe connection according to claim 5 or 6, characterized in that the second cylindrical surface (60) extends above the second critical cross-section of the box-like element (BCCS2) located in the first cavity of the engaged thread of the female female thread (28) near the internal shoulder (18). 9. Threaded pipe connection according to any one of claims 5 to 7, characterized in that the second cylindrical surface (60) extends above the female female thread part and the first machined outer surface (58) extends above the female male thread part. 10. A threaded pipe connection according to any one of the preceding claims, characterized in that the female pipe end (20) comprises a female outer sealing surface (27, 27') and the male pipe end (30) comprises a male outer sealing surface (37, 37' ), whereby the male and female outer sealing surfaces (27, 27', 37, 37') form an outer metal-to-metal seal when the threaded pipe connection is screwed, and the outer diameter of the female pipe end is higher than this female outer sealing surface (27, 27 ') is equal to the first outer diameter (JOB). 11. Threaded pipe connection according to claim 10, characterized in that the female outer sealing surface (27) is located between the female male thread and the female free end. 12. Threaded pipe connection according to claim 10, characterized in that the female outer sealing surface (27) is located between the female outer thread and the intermediate shoulder. 13. A threaded pipe connection according to any of the preceding claims, characterized in that the male free end (35) is located at a distance in the longitudinal direction from the inner -