Threaded connection partially in a self-locking engagement

Abstract

A threaded connection partially in a self-locking arrangement includes a first and a second tubular component provided respectively with male and female threaded zone at their respective ends. Only a portion of a first portion with varying thread width of the male threaded zone cooperates by self-locking tightening with only a portion of the second portion with varying thread width of the female threaded zone when made up one into the other. The connection is able to withstand high torques required for special applications such as drilling with casing or intermediate casing.

Claims

1. A threaded connection comprising: a first and a second tubular component, the first tubular component being provided with a pipe body and a male member at a distal end of the pipe body, the second tubular component being provided with another pipe body and a female member at a distal end of that pipe body, such that a male member comprises, on an external peripheral surface, at least one male threaded zone and finishes in a male terminal surface, and a female member comprises, on an internal peripheral surface, at least one female threaded zone and finishes in a female terminal surface, the male threaded zone comprising a male thread having a first portion in which the width of a thread crest increases continuously over an entirety of the first portion in a direction oriented from the male terminal surface towards the pipe body of the first tubular component, a tooth closest to the male terminal surface presenting a minimum crest width value of the male thread, and the female threaded zone comprising a female thread having a second portion in which the width of a thread crest increases continuously over an entirety of the second portion along a direction oriented from the female terminal surface towards the pipe body of the second tubular component, a tooth closest to the female terminal surface presenting a minimum crest width value of the female thread, wherein each tooth of the first portion is between two adjacent teeth of the second portion when the connection is made up, and wherein only part of the first portion cooperate with only a part of the second portion in accordance with a self-locking make-up arrangement in order to provide a locking region in the threaded connection.

2. The threaded connection according to claim 1, wherein the locking region comprises a number of threads in self-locking arrangement, wherein first and second portions comprise a number of threads strictly greater than the number of threads of the locking region.

3. The threaded connection according to claim 1, wherein the male threaded zone has a male distal portion defined by a different wedge ratio than in the locking region, the distal portion including the tooth that is closest to the male terminal surface, the male distal portion being adjacent to the first portion.

4. The threaded connection according to claim 3, wherein the female threaded zone has a female distal portion defined by a different wedge ratio than in the locking region, the female distal portion including the tooth which is closest to the female terminal surface, the female distal portion being adjacent to the second portion.

5. The threaded connection according to claim 4, wherein the tooth of the female distal portion which is closest to the female terminal surface has the same crest width as the tooth of the male distal portion which is closest to the male terminal surface.

6. The threaded connection according to claim 1, wherein a lead of a male stab flanks is constant in the first portion and gets a distinct value in a distal portion of the male threaded zone, the distinct value being lower or equal to the value of a lead of a male load flanks which remains constant in the first and distal portions, the male distal portion being adjacent to the first portion.

7. The threaded connection according to claim 1, wherein a lead of the male load flanks is constant in the first portion and gets a distinct value in a distal portion of a male threaded zone a value greater or equal to the value of a lead of a male stab flanks which remains constant in the first and distal portions, the male distal portion being adjacent to the first portion.

8. The threaded connection according to claim 1, wherein the male threaded zone has a male proximal portion defined by a different wedge ratio than in the locking region, the proximal portion including the tooth that is farthest to the male terminal surface, the male proximal portion being adjacent to the first portion.

9. The threaded connection according to claim 1, wherein the female threaded zone has a female proximal portion defined by a different wedge ratio than in the locking region, the proximal portion including the tooth that is farthest to the female terminal surface, the female proximal portion being adjacent to the second portion.

10. The threaded connection according to claim 1, wherein a lead of a male stab flanks is constant in the first portion and gets in a proximal portion of the male threaded zone a value lower or equal to the value of a lead of a male load flanks which remains constant in the first and proximal portions, the male proximal portion being adjacent to the first portion.

11. The threaded connection according to claim 1, wherein a lead of a male load flanks is constant in the first portion and gets in a proximal portion of the male threaded zone a value greater or equal to the value of a lead of a male stab flanks which remains constant in the first and proximal portions, the male proximal portion being adjacent to the first portion.

12. The threaded connection according to claim 1, wherein a wedge ratio changes at two locations on both the male threaded zone and the female threaded zone.

13. The threaded connection according to claim 1, wherein a lead of a male stab flanks changes at two locations on the male threaded zone and a female stab flanks changes at two locations on a female threaded zone, and wherein a lead of male load flanks and a lead of a female load flanks remain constant along the whole male threaded zone, and respectively female threaded zone.

14. The threaded connection according to claim 1, wherein the male threaded zone comprise dovetail thread, and the minimum value (CWTpmin) of the width of the tooth which is closest to the male terminal surface fulfill at least one of the below equations $\begin{array}{cc}0.8202*\mathrm{TH}\le \mathrm{CWTpmin}& \left(a\right)\\ \mathrm{CWTpmin}\le \mathrm{BTG}-\left(\mathrm{PLH}*\tan \left(\alpha \right)\right)-(\left[\mathrm{PLH}+\left(\mathrm{LFP\_p}1*\tan \left(\varnothing \right)\right)-\left(\mathrm{BTG}*\tan \left(\varnothing \right)\right]*\tan \left(\alpha \right)\right)& \left(b\right)\end{array}$ wherein: BTG is the female minimum thread gap, of a thread gap not involved in the locking region $\mathrm{BTG}=\frac{\mathrm{SFP\_p}1}{2}-\left(\frac{n}{2}*\left({\mathrm{LFP}}_{p1}-{\mathrm{SFP}}_{p1}\right)\right)$ wherein: n is a number of locking thread of the locking region, SFP_p1 is stab flank lead in the first portion, LFP_p1 is load flank lead in the first portion,
LFP.sub.p1−SFP.sub.p1 is also called wedge ratio TH is a nominal thread height in the first portion, PLH is a distance from the pin pitch line to root in the first portion, the pin pitch line is determined by all points at mid height of the flanks, the flanks having a constant lead in that first portion, α is a load and respectively stab flank angle with a perpendicular to the axis of the connection, and Ø is a taper angle, wherein the taper angle is an angle between a generatrix of male and female threaded zones and the axis of the connection.

15. The threaded connection according to claim 1, wherein the male and female threaded zones have a taper generatrix forming an angle with the axis of the connection in the range from 1 degree to 5 degrees.

16. The threaded connection according to claim 1, wherein the teeth of the male and female threaded zones have a dovetail profile, and the crests of the teeth and roots of the male and female threaded zones are parallel to the axis of the threaded connection.

17. The threaded connection according to claim 1, wherein the teeth of the male and female threaded zones have a dovetail profile such that respective load flanks and stab flanks being at an angle of a same angle value a compare to a perpendicular to an axis of the connection, that α angle being between 1° and 6°.

18. The threaded connection according to claim 1, wherein only one of the crest of the teeth of the male threaded zone with roots of the female threaded zone, or roots of the teeth of the male threaded zone with the crests of the female threaded zone are interfering, in the locking region, such that the diameter interference at the root/crest interference may be above 0.0025 times the pipe body nominal outer diameter.

19. The threaded connection according to claim 1, wherein the threaded connection is free from any distal abutment surface, a free end of the male member being away from the female member, and respectively a free end of the female member being away from the male member.

20. The threaded connection according to claim 1, wherein both male and female member are free of any additional sealing surfaces beside the locking region.

21. The threaded connection according to claim 1, wherein the threaded connection is semi flush, and the first and a second tubular component are integral, each first and second tubular component comprising a male member and a female member.

22. The threaded connection according to claim 1, wherein the part of the first portion and respectively the part of the second portion of the threaded zones of respectively the male member and the female member cooperating by self-locking in the locking region each representing more than 30% and less than 80%, in number of teeth of the respective threaded zone.

23. The threaded connection according to claim 1, wherein all teeth of the male and or female threaded zone have the same height, except the tooth presenting a minimum crest width.

24. The threaded connection according to claim 1, wherein the male threaded zone and the female threaded zone are respectively a single continuous thread.

25. The threaded connection according to claim 1, wherein the male threaded zone and the female threaded zone are single start thread.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The characteristics and advantages of the invention are disclosed in more detail in the following description made with reference to the accompanying drawings.

(2) FIG. 1 is a partial diagrammatic view of a connection comprising a self-locking threading in accordance with the invention.

(3) FIG. 2 is a detailed longitudinal sectional view of a female member of a tubular component of a connection in accordance with the invention.

(4) FIG. 3 is a detailed longitudinal sectional view of a male member of a tubular component of a connection in accordance with the invention.

(5) FIG. 4 is a detailed longitudinal sectional view of a connection in accordance with the invention, near the male free end.

(6) FIG. 5 is a detailed view of a male teeth of a male member in accordance with the invention.

(7) FIGS. 6 to 9 are graphs according to different embodiments of the invention showing the evolution of the leads between the load flanks and the stab flanks for respectively the male member and female member along the threads of the male and female member in accordance with FIG. 1 as a function of the distance from the distal end surface of the male member, when the connection is made up. Graphs of FIGS. 6 to 9 represent lead values of respectively male stabbing flanks (SFP_p), male loading flanks (LFP_p), female stabbing flanks (SFP_b), and female loading flanks (LFP_b) along y-axis, with x-axis representing the location of the thread along a longitudinal axis of the tubular component, between box face 8 and pin face 7 when the connection is made-up.

DETAILED DESCRIPTION

(8) The threaded tubular connection shown in FIG. 1 comprises a tubular component provided with a male member 1 and a tubular component provided with a female member 2. Both male member 1 and female member 2 are provided with tapered threaded zones 3, 4 that cooperate for mutual connection by make-up of the two components. FIG. 1, the threaded connection is shown fully made up.

(9) The male member finishes in a male terminal surface 7, forming an axial free end of the male member or pin face. The male terminal surface 7 is also a free axial surface of the first tubular component. The female member 2 finishes in a female terminal surface 8, forming an axial free end of the female member or box face. The female terminal surface 8 is also a free axial surface of the second tubular component. The male terminal surface 7 and the female terminal surface 8 are oriented radially with respect to the longitudinal axis X of the connection. None of the male terminal surface 7 and the female terminal surface 8 are placed in abutment contact at the end of make up.

(10) Preferably, both tubular component are integral, as they are both provided with a pipe body, a male member at one first distal end of the pipe body, and at an opposite distal end of the pipe body with a female member. Both tubular components are made out of steel. Threaded zones are respectively machined, wherein a surface treatment is provided to the female member only, and dope is additionally placed around the male member before make up. Alternatively, both the male member and the female member may be surface treated. For example, a surface treatment may be Zinc Phosphate treatment.

(11) For example, grade of the material is between 80 ksi (550 MPa) and 140 ksi (965 MPa). For example, grade is above 100 ksi (690 MPa), for example 125 ksi (860 MPa).

(12) According to the present invention, connection efficiency under both tension and compression are above 70% of the pipe body yield strength.

(13) Pipe body may be with an outer diameter between 3½″ (88.90 mm) to 16″ (406.4 mm), and pipe body wall width of 8 to 22 mm.

(14) According to examples of the invention, the pipe body outer diameter may be 13⅝″ (330.2 mm), with a pipe body wall width of 0.625″(15.8 mm).

(15) Threaded zones may be single start. Each threaded zone may have a unique single threaded spire. A unique threaded spire means a spire with no interruption.

(16) When made up, the connection of the invention is comprising a locking portion 10 wherein respective part of the threaded zones 3 and 4 are in a known “self-locking” configuration wherein both male threaded zone and female threaded zone present at least in that locking region 10 a progressive variation of the axial width of the thread crests and of the intervals between the threads such that a progressive axial tightening is produced during make-up until a final locking position.

(17) The term “self-locking” configuration means the characteristics detailed below for the teeth in the locking region. The male threads (or teeth) 32, like the female threads (or teeth) 42, have a constant lead although their crest width respectively decreases towards their respective terminal surface 7, 8 such that during make-up, some of male 32 and female 42 threads (or teeth) finish by locking into each other in a determined position. Thread in the locking configuration, are such that all the stab flanks and all the load flanks of the male threads (or teeth) lock against one another respectively the stab flanks and the load flanks of the corresponding female threads (or teeth).

(18) At the end of makeup, in the locking region 10, there is no axial gap between axial flanks, both Load flanks and Stab flanks. Axial flanks define essentially radially compared to the axis of the connection. Moreover, design of the connection according to the invention is such that there is no radial gap between at least male thread crest and female thread root in the locking region. Thus, the locking region forms a seal by generating enough contact to trap dope and withstand high pressure. Crests and roots are in interfering contact, and axial flanks interfere too.

(19) According to the present invention, only a specific number of threads of each of the male 32 and female 42 threads are in that specific locking configuration, and are involved in the locking portion 10. The locking portion 10 is away from the first and last thread of the threaded zone. At least first and last thread of both the male 32 and female 42 threads are not in a locking configuration.

(20) More precisely, FIG. 6, the male threaded zone 3 comprise a first portion 11 wherein the lead SFP_p between the male stabbing flanks 31 is constant at a value SFP_p1, and the lead LFP_p between the male load flanks 30 is also constant but at a different value LFP_p1. In the example of FIG. 6, LFP_p1 is strictly superior to SFP_p1. For example, in one embodiment of the invention:
LFP_p1=9.7 mm
SFP_p1=9.4 mm

(21) Thus a wedge ratio of the first portion, which is the difference between the load flank lead and the stab flank lead here equals 0.3 mm.

(22) Within the scope of the invention, other stab flank lead and load flank lead values are acceptable.

(23) Similarly the female threaded zone 4 comprise a second portion 12 wherein the lead LFP_b between the load flanks 41 is constant at a value LFP_b1, and the lead SFP_b between the stabbing flanks 40 is also constant but at a different value SFP_b1, with the feature that the lead between the load flanks 41 is greater than the lead between the stabbing flanks 40.

(24) Further, as represented FIG. 6, the respective leads SFP_p1 and SFP_b1 between the male 31 and female 40 stabbing flanks are equal and smaller than the respective leads LFP_p1 and LFP_b1 between the male 30 and female 41 load flanks, which are themselves equal.

(25) FIGS. 3 and 6, the male threaded zone 3 comprises, in addition to the first portion 11, a male distal portion 13, adjacent to the first portion 11 and located on the side of the first portion closest to the male free end surface 7. The male threaded zone 3 also comprises a male proximal portion 15 adjacent to the first portion 11, but located on the other side of the first portion, the one farthest of the male free end surface 7. Each of the male distal portion 13 and the male proximal portion 15 comprise a portion of thread covering at least 360°, and preferably two turns. The male distal portion 13 and the male proximal portion 15 distinguish from the first portion 11, by the lead of at least one of the stab flank and/or the load flank is/are distinct from the values observed in the first portion.

(26) In the example of FIG. 6, Male distal portion 13 and the male proximal portion 15 distinguish from the first portion 11 by only the lead of the stabbing flank SFP_p, the lead of the load flank LFP_p remaining at a same value LFP_p1 all along the threaded portion. In particular, FIG. 6, lead of the male stabbing flanks in the distal portion 13 and the proximal portion 15 are equal and equal to the lead of the male load flanks LFP_p1. And the lead of the male stabbing flank in the first portion 11 reach a value SFP_p1 inferior to the male load flank lead LFP_p1.

(27) Thus, a male wedge ratio along the male distal and proximal portions equals 0, whereas a non-null wedge ratio exists within the male first portion 11.

(28) As an alternative to the embodiment of FIG. 6, FIG. 7 proposes a strictly positive, non-null, wedge ratio in the first portion and null wedge ratio along the male distal and proximal portions obtained by the sole increase of the Load flanks lead in the first portion relative to both distal and proximal male portions. According to this alternative embodiment, along both distal and proximal male portions, Load Flank lead equals Stab Flanks lead, Stab Flank leads remaining constant all along the threaded portion.

(29) Along another embodiment of the invention, alternative to FIG. 6, as shown FIG. 8, wedge ratio in the male distal and proximal portion is strictly above 0, non-null, and strictly below the wedge ratio observed along the first portion. The lead of the stab flank within the male distal and respectively proximal portion being lower to the lead of the load flanks in that male distal portion and respectively proximal portion, while the lead of the Load flank in the male distal portion remains constant and equals to the lead of the Load flanks in the first portion.

(30) Another embodiment according to the invention could cover a varying wedge ratio within the male distal and proximal portion, such varying value remaining strictly below the wedge ratio of the first portion. Values of wedge ratio and/or pattern of variation of wedge ratio along the distal and proximal portion may be identical or not.

(31) Similarly, FIGS. 2 and 6, the female threaded zone 4 comprises, in addition to the second portion 12, a female distal portion 14, adjacent to the second portion 12, located on the side of the second portion closest to the female free end surface 8. The female threaded zone 4 comprises a female proximal portion 16 adjacent to the second portion 12, but located on the other side of the second portion, the one farthest of the female free end surface 8. Each of the female distal portion 14 and the female proximal portion 16 comprises a portion of thread covering at least 360°, and preferably two turns. The female distal portion 14 and the female proximal portion 16 distinguish from the second portion 12, by the lead of at least one of the stab flank and/or the load flank is/are distinct from the values observed in the second portion.

(32) FIG. 6, female distal portion 14 and the female proximal portion 16 distinguish from the second portion 12, by only the lead of the stabbing flank SFL_b, the lead of the load flank LFP_b remaining at a same value LFP_b1 all along the threaded portion. In particular, lead of the female stabbing flanks in the distal portion 14 and the proximal portion 16 are equal and equal to the lead of the female load flanks LFP_b1, which is also equal to the male Load Flanks LFP_p1. The lead of the female stabbing flanks in the second portion 12 reach a value SFP_b1 inferior to the male load flank lead LFP_b1.

(33) More specifically, LFP_b1=LFP_p1 and SFP_b1=SFP_p1.

(34) FIGS. 7 and 8, female distal and proximal portions present the same type of variation of the Stab flanks lead and Load flanks lead as is the case in the male treaded portion, except that the location of changes in the female leads are not superimposed along a longitudinal axis of the connection, with the location of those changes in the male leads.

(35) According to the invention, when the connection is made up, at least one of a tooth of the male proximal portion 15 is engaged in an interval between two adjacent teeth of the second portion 12, therefore defining a transition region 20 and/or a tooth of the female proximal portion 16 is engaged in an interval between two adjacent teeth of the first portion11, therefore defining a transition region 21.

(36) A tooth engaged in an interval is to be interpreted as at least a 360° tooth engaged in at least a 360° interval. In the transition region 20 and 21, there is no contact between at least one of the stabbing flanks and/or the load flanks.

(37) Therefore, when a connection according to the invention is made up, a female locking part 10b of the second portion 12 is engaged in a self-locking configuration with the male threaded zone 3, female part 10b being adjacent to the female proximal portion 16;

(38) And/or a male locking part 10p of the first portion 11 engage in a self-locking configuration the female threaded zone 4, male part 10p being adjacent to the male proximal portion 15.

(39) Locking parts 10p and 10b are locking threads defining the locking region.

(40) Then in the made up position, respectively the male distal portion 13 and the remainder part 17 of the first portion 11, that one that is not involved in the locking region 10, are both engaged in the intervals of the female proximal portion 16;

(41) and/or the female distal portion 14 and the remainder part 18 of the second portion 12, that one that is not involved in the locking region 10, are both engaged in the intervals of the male proximal portion 15.

(42) According to the above “and/or” options, FIGS. 1 to 3 are a representation of the “and” option.

(43) In the example of FIGS. 1 to 3, on both side of the locking portion 10, there are transition regions 20, 21, where at least stab flanks start not interfering each other. Transition region 20 is where female remainder part 18 of the second portion 12 engage the male proximal portion 15. Transition region 21 is where male remainder part 17 of the first portion 11 engage the female proximal portion 16.

(44) The first portion 11 is consisting of a male locking part 10p and a remainder part 17. The second portion 12 is consisting of a female locking part 10b and a remainder part 18.

(45) FIGS. 1 to 3, from the transition region 21 to the male free end 7, the threaded connection comprises an internal threaded region 23, where the male distal portion 13 engages the female proximal portion 16. Symmetrically, from the transition region 20 and the female free end 8, the threaded connection comprises an external threaded region 22, where the male proximal portion 15 engages the female distal portion 14. In the internal threaded region 23 and external threaded region 22, a positive clearance exists between respective male and female stab flanks. For example, that clearance is at least 1 mm, and for example below 5 mm.

(46) Preferably, the locking region 10 locates axially in the middle of the threaded connection. Thus part 10p of the first portion 11 locates axially in the middle of the male threaded zone 3, and respectively part 10b of the second portion 12 locates axially in the middle of the female threaded zone 4. As for an example, the locking region comprises 8 threads where the threaded connection in full comprises at least 10 threads, and preferably more than 14 threads, for example 16 threads. According to the present invention, with

(47) n=number of threads of the locking region

(48) Then the number of threads of the connection is for example at least more than 1.25 times*n; and more preferably at least more than 1.75*n; for example 2 times*n.

(49) According to a first embodiment of the invention, FIG. 6, the male stab flank lead SFP_p change respectively in the distal portion 13 and the male proximal portion 15, in order to reach a value that is the load flank lead value LFP_p1 as set in the first portion, and the female stab flank lead change respectively in the distal portion 14 and the female proximal portion 16, in order to reach a value that is the load flank lead value LFP_p1 as set in the first portion, and both the male and female load flank lead is constant all over the connection, respectively equals to LFP_p1.

(50) Variation of the male stab flank lead SFP_p curve between proximal portion 15 and first portion 11 is located at 515 and respectively reversely at 516 between first portion 11 and male distal portion 13. Variation 513 and 514 are sudden, and appear in less than one turn, preferably less than 180°. Variation of the female stab flank lead SFP_b curve between proximal portion 16 and second portion 12 is located at 513 and respectively reversely at 514 between second portion 12 and female distal portion 14. Variation 514 and 513 are sudden, and appear in less than one turn, preferably less than 180°.

(51) Variations 514 and 515 occurring at a different axial location within the threaded connection, the transition region 20 defines between variations 514 and 515. Symmetrically variations 513 and 516 occurring at a different axial location within the threaded connection, the transition region 21 defines between variations 513 and 516. Transition region 20 and 21 in accordance with the invention enables to conserve a good effective locking portion despite variations in the axial positioning of the assembled elements due to machining tolerances, the effective seal of the locking region being efficient over several teeth of that locking portion.

(52) According to that first embodiment, within the internal thread portion 23 and external threaded portion 22, both male and female thread have the same load flank lead and stab flank lead. Thus, male teeth involved in the internal thread portion 23 have all the same constant crest width CWTpmin as the female teeth involved in the external thread portion 22, which have the same crest width CWTbmin. The internal thread portion 23 comprises the teeth of the male distal portion closest to the male terminal surface 7, which are the teeth with the smallest crest width value of the whole male threaded zone 3. The external thread portion 22 comprises the teeth of the female distal portion closest to the female terminal surface 8, which are the teeth with the smallest crest width value of the whole female threaded zone 4. Both teeth have a same crest width minimum value CWTmin=CWTbmin=CWTpmin.

(53) According to the invention, in order to avoid early thread crest interference, during make up, the inventors have discover the need to control by a relation between the teeth crest width and the box rear non-locking thread gap width.

(54) Advantageously and as shown in FIGS. 4 and 5, the male and female threads (or teeth) have a dovetail profile. This profile enables to avoid the risk of jump-out, which corresponds to the male and female threads coming apart when the connection is subjected to large bending or tensile stresses. More precisely, the geometry of the dovetail threads increases the radial rigidity of their assembly compared with threads, which are usually termed “trapezoidal” threads wherein the axial teeth width reduces from the base to the crest of the threads. Advantageously, the load flanks of the thread connect to the thread crest and to the adjacent thread root by roundings such that these roundings reduce the stress concentration factor at the foot of the load flanks and thereby improve the fatigue behavior of the connection.

(55) FIG. 4, the crests of the teeth and the roots of the roots of the male and female threaded zones are parallel to the longitudinal axis X of the threaded connection. This facilitates machining.

(56) Along a longitudinal section of the threaded connection, both load flank and stab flank present a straight profile. Load flank and stab flank are respectively making an angle α with a vertical to the longitudinal axis X. Load flank angle value equals stab flank angle value, while being opposed and defined on opposed sides of a vertical to the longitudinal axis X. For example angle α is comprised between 1° and 6°, for example equals 5°. Thus the crest of a teeth is always the largest dimension of that teeth when considering the width of a teeth along the longitudinal axis X.

(57) The threaded connection is tapered so as to facilitate the progress of make-up. A pitch line is having a taper angle Ø with the longitudinal axis X. The pitch line defines as passing through the aligned center of the flanks of the male threaded zone having a same lead value all along the connection. According to the first embodiment, the lead of the load flanks remains at a same value all along the male threaded zone, thus the pin pitch line defines as passing through the aligned center of the load flanks. For example the taper angle Ø is for example comprised between 1 and 10°, for example equals 4.7°.

(58) Advantageously, the first gap of the female proximal portion 16 not engaging a teeth is having a gap width BTG according to the below formula

(59) $\mathrm{BTG}=\frac{\mathrm{SFP\_p}1}{2}-\left(\frac{n}{2}*\left({\mathrm{LFP}}_{p1}-{\mathrm{SFP}}_{p1}\right)\right)$
Wherein
n is the number of locking thread of the locking region
SFP_p1 is stab flank lead in the first portion
LFP_p1 is load flank lead in the first portion
LFP.sub.p1−SFP.sub.p1 is also called wedge ratio TH is a nominal thread height in the first portion PLH is the distance from the pin pitch line to root in the first portion.
When stab flank lead is constant in the first portion, pin pitch line is determined with points at mid-height of the stab flanks. To the opposite, when stab flank lead is varying in the first portion, and the load flank lead is constant in the first portion, pin pitch line is determined with points at mid-height of the load flanks.
α is the load and respectively stab flank angle with a perpendicular to the axis of the connection
Ø is the taper angle, wherein the taper angle is an angle between a generatrix of male and female threaded zones and the axis of the connection

(60) BTG is also the female minimum thread gap of thread teeth not involved in the locking region, for example of thread gap of the female proximal portion 16.

(61) The crest width of a tooth, or largest width dimension of that tooth, is such that the minimum value (CWTpmin) of the width of the crest of the tooth which is closest to the male terminal surface 7 fulfill at least one of, and preferably both of the below equations

(62) $\begin{array}{cc}0.8202*\mathrm{TH}\le \mathrm{CWTpmin}& \left(a\right)\\ \mathrm{CWTpmin}\le \mathrm{BTG}-\left(\mathrm{PLH}*\tan \left(\alpha \right)\right)-(\left[\mathrm{PLH}+\left(\mathrm{LFP\_p}1*\tan \left(\varnothing \right)\right)-\left(\mathrm{BTG}*\tan \left(\varnothing \right)\right]*\tan \left(\alpha \right)\right)& \left(b\right)\end{array}$
For example, according to the invention, and for at least the first embodiment of FIG. 6:
1.804 mm≤CWTpmin≤3.262 mm

(63) And BTG=3.5 mm

(64) FIG. 7, is an alternative embodiment of FIG. 6, wherein difference with FIG. 6 mainly explain as differential variation of the load flank lead and stab flank lead. According to a second embodiment of the invention, FIG. 7, the male load flank lead LFP_p change respectively from the distal portion 13 and the male proximal portion 15, in order to reach a value that is the load flank lead value LFP_p1 as set in the first portion, and the female load flank lead LFP_b change respectively from the distal portion 13 and the male proximal portion 15, in order to reach a value that is the load flank lead value LFP_p1 as set in the first portion, and both the male and female stab flank lead being constant all over the connection, respectively equals to SFP_p1.

(65) FIG. 8, is another alternative embodiment of FIG. 6, wherein difference with FIG. 6 mainly explain as the load flank lead of the female and male member in their respective distal portion and proximal portion is greater than the value of both the male and female load flank lead. Load flank lead is constant all over the connection, respectively equals to LFP_p1.

(66) FIG. 9 is combining male leads change as of FIG. 6 together with female leads change as of FIG. 7, with the constant feature of the axial location of the male and female leads changes being not superimposed.

(67) The invention encompass threaded connection comprising a locking portion, adjacent to a transition portion, the transition portion being adjacent to a distal or proximal portion, such that teeth are not in self-locking engagement in both the transition portion and at least one of the distal and proximal portion. For example, teeth not in self-locking arrangement are such that stab flanks are not interfering, and male or female tooth having the same minimal crest width.

(68) The invention encompass threaded connection comprising a locking portion being adjacent at both axial ends of the locking portion to transition portions, such that teeth are not in self-locking engagement in both transition portions.

(69) The minimum make-up torque required may be between 55 000 ft.lbs (74570 N.m) and 70 000 ft.lbs (94 907 N.m).