Patent Description:
The present invention relates to threaded pipes and connectors for such pipes which may be used in the oil and natural gas industry. For example, a pipe can have an end with a pin that fits into a box at one end of a connector, the pipe and connector being connected by threading. The connector can have a second box for a second pipe with a second pin, so that the pipe and the second pipe are connected via the connector.

<CIT> purportedly describes a tubular joint or connector of box and pin members having two-step tapered threads. Two metal to metal seals of complementary engaging sealing surfaces are provided. Reverse angle torque shoulders at the end of the pin member and the interior termination of the box member and hooked threads further characterize the joint and box and pin members.

<CIT> purportedly describes a screw joint coupling for oil pipes. A main sealing portion is provided with a sealing portion which is axially convex at an end of a male screw, and with a sealing portion which is tapered at an inner side of a female screw, and an end point of the male screw butting an end part of a stopper formed at the inner side of the female screw.

<CIT> purportedly describes a tubular connection that has cooperating internal frusto-conical sealing surfaces on a counterbore of the box member and a free end of the pin member. The internal sealing surface of the pin member inclines inwardly substantially at fourteen degrees from the axis of the tubular connection adjacent the end of the pin member. The angle of the incline of the box internal sealing surface is substantially the same as that of the pin internal surface. A pilot surface or bull nose disposed from a distal-proximate end to the distal end of the pin member inclining to a lesser extent than the angle of the incline of the internal surface of the pin member being substantially parallel to the axis of the connection; defines an increased end-of-pin flat thickness.

<CIT> purportedly describes a threaded tubular connection with a male threaded element and a female threaded element. The male threaded element has male threading and a free end, with a non-threaded lip between the threading and the free end. The female threaded element has an internal tapered female threading and a non-threaded portion between the female threading and a lug. The female threaded element comprises an annular axial abutment surface. After complete makeup of the male threading in the female threading, the free end bears against the annular axial abutment surface, which other bearing surfaces radially interfere and are under metal-metal contact pressure to constitute metal-metal sealing surfaces.

In the `<NUM> patent, another axial abutment surface thus is formed on a front surface of the free end of the male threaded element, and a single lip sealing surface is disposed on the lip at an axial distance from the end of the threading. The lip comprises, between the distal axial abutment surface and the single lip sealing surface, an appendix having a peripheral surface facing the female threaded member that is distinct from the lip sealing surface.

<CIT> purportedly describes a tubular connection including a pin and box member. The pin member has a first thread structure and a helical torque shoulder spaced axially along the pin member from the first thread structure. The box member has a second thread structure and a second helical torque shoulder spaced axially along the box member from the second thread structure. Upon rotation, the helical torque shoulders engage one another.

<CIT> describes a threaded connection for pipes, such as oil and gas pipes.

During make-up of a premium connection between a threaded tube with a pin, such as a pipe, and a threaded tube with a box, such as a connector, the following sequence occurs: (<NUM>) the pin on the pipe is stabbed into the connector until thread crests touch; (<NUM>) the pin is then screwed into the box until the pin seal surface initially touches the box seal surface, to define a position referred to as "hand tight"; (<NUM>) the pin is further screwed into the box until an end of the pin, a so-called torque shoulder, just touches a corresponding torque shoulder on the box, to define a position referred to as "shoulder tight", with this additional turning from the hand tight to the shoulder tight positions causing an interference fit between the pin and box seals; and (<NUM>) then the pin is further tightened to create an additional torque to define a final made up position is referred to as "power tight".

A distance between the pin torque shoulder and box torque shoulder when the connection is at the hand tight position is called "standoff. " The standoff is eliminated once the shoulder tight position is reached. A large standoff may be problematic because the pin seal surface and box seal surface are in contact while the standoff is being eliminated. If a large amount of turning is needed to reduce a large standoff, galling of the seal surfaces occurs, thereby compromising the seals.

An object of the present invention is to provide torque shoulder that secures or traps the pin in the box thereby reducing or eliminating movement of the pin with respect to the box. For example, the torque shoulders will prevent the pin from moving, bending or deforming in the radial direction.

An alternate or additional object is to provide a connection that is easy to manufacture.

The present invention provides a threaded tubular connection according to claim <NUM>.

The present invention also provides a method for forming a threaded tubular connection according to claim <NUM>.

A preferred embodiment of the present invention will be elucidated with reference to the following drawings, in which:.

<FIG> shows a traditional torque shoulder and metal-to-metal seal combination as known in the art. Box <NUM> includes box seal surface <NUM> and box torque shoulder <NUM>. Pin <NUM> includes pin seal surface <NUM>, nose <NUM> and pin torque shoulder <NUM>. As shown in <FIG>, pin seal surface <NUM> is located at an end of pin <NUM>. The nose <NUM> of pin <NUM> is wedged between pin seal surface <NUM> and pin torque shoulder <NUM> when the connection is formed. The connection of pin <NUM> and box <NUM> defines a longitudinal axis of the pipe and connector (not shown). An axis X is perpendicular to the longitudinal axis and runs through the end of the torque shoulders <NUM>, <NUM> at pin nose <NUM>. Pin torque shoulder <NUM> and box torque shoulder <NUM> each include a single shoulder surface that is angled with respect to perpendicular axis X. An interior angle A formed between torque shoulders <NUM>, <NUM> and perpendicular axis X may be, for example, approximately -<NUM>°, that is, <NUM>° in the clockwise direction from axis X. This angle of incline is known in the prior art. In this example the pin nose <NUM> is tightly wedged between box seal surface <NUM> and box torque shoulder surface <NUM>. See for example, <CIT>.

<FIG> shows a premium connection as known in the prior art. <FIG> shows a close up of the connection of <FIG> when the torque shoulders <NUM>, <NUM> just begin to contact. A gap Sc exists between an outer surface of pin <NUM> and a counter-bore surface of box <NUM> and is necessary for ease of assembly. While angle A is beneficial to lock the pin <NUM> and box <NUM> together after assembly, <FIG> shows that, during further screwing of the connection, angle A causes the pin <NUM> to crash into the box <NUM>. This undesirable contact can prevent proper positioning of the connection during assembly and may cause damage to seal surfaces <NUM>, <NUM> or torque shoulders <NUM>, <NUM>.

In accordance with the present invention, a premium connection is provided that includes advantages over the prior art, for example, movement of the pin may be controlled and the undesirable contact and damage to seal surfaces discussed above may be reduced. The premium connection includes pin and box torque shoulders with a plurality of surfaces, for example, each torque shoulder may have a top and bottom torque shoulder surface with respect to the orientation shown in <FIG>. Another feature according to the present invention also includes seal surfaces that are spaced apart from the shoulder surfaces as shown in <FIG>, <FIG> and <FIG>. A further feature includes a space existing between an edge of the pin and an edge of the box or connector even after the pin is in a final position. See <FIG> and <FIG> and <FIG>.

In a preferred embodiment, both torque shoulders, top and bottom, of the pin and box may contact each another at the same time. Thus, the connector provides a neutral trap for the pin. In another preferred embodiment, top torque shoulder surfaces of the pin and box may contact one another prior to bottom torque shoulder surfaces of the pin and box contacting one another. In this embodiment, the pin may bend downward. In a further preferred embodiment, bottom torque shoulder surfaces of the pin and box may contact one another prior to the top torque shoulder surfaces of the pin and box contacting one another. In this embodiment, the pin may bend upward. See <FIG> and <FIG>. As a result, the movement of the pin can be controlled as desired.

<FIG> shows a cross section view of an oil pipe <NUM> and a connector <NUM>, in a first stage, the stabbed position. <FIG> show the connection with oil pipe <NUM> and connector <NUM>, in a second stage, after rotation has occurred. Oil pipe <NUM> has a pin <NUM> with a threaded section <NUM>, a pin seal surface <NUM> and a torque shoulder <NUM> at a free end. Pin torque shoulder <NUM> includes first surface 26a and second surface 26b. Connector <NUM> has two boxes <NUM>, <NUM>'. Each box <NUM>, <NUM>' has a threaded section <NUM>, a box seal surface <NUM> and a torque shoulder <NUM> on a radially inwardly projection <NUM>. Box torque shoulder <NUM> includes first surface 126a and second surface 126b. In this embodiment, the first box shoulder surface 126a is complementary with the first pin shoulder surface 26a and the second box shoulder surface 126b is complementary with the second pin shoulder surface 26b.

Connector <NUM> has two free ends <NUM> and <NUM>' as shown in <FIG>. As described above, in the stabbed position, oil pipe <NUM> is stabbed or placed into connector <NUM> until threaded section <NUM> of pin <NUM> contacts threaded section <NUM> of boxes <NUM>, <NUM>'. Rotation has not yet occurred between pin <NUM> and boxes <NUM>, <NUM>'. The rotation of pin <NUM> and boxes <NUM>, <NUM>' forms the connection.

This second stage of makeup is known as the hand tight position in which the threads <NUM>, <NUM> or seal surfaces <NUM>, <NUM> just begin to touch one another. Threads <NUM> of pin <NUM> engage threads <NUM> of box <NUM>. Pin seal surface <NUM> and box seal surface <NUM> just begin to touch. A gap or standoff "Sa" exists between the first surfaces 26a, 126a of pin torque shoulder <NUM> and box torque shoulder <NUM> and a gap or standoff "Sb" exists between the second surfaces 26b, 126b of pin torque shoulder <NUM> and box torque shoulder <NUM> in the hand tight position. In this embodiment, the standoff Sa is, for example, approximately <NUM> in. and the standoff Sb is, for example, approximately <NUM> in. The standoffs Sa and Sb may vary as a result of the designed seal interference and seal angles and do not have to be equal.

A nose <NUM> extends at an end of pin <NUM>. Nose <NUM> is located between an inner surface <NUM> and an outer surface <NUM> of pin <NUM> and along a length of torque shoulder <NUM> in a direction of axis P, an axis that is perpendicular to the longitudinal axis. The nose <NUM> is a vertex connecting first surface 26a and second surface 26b of torque shoulder <NUM>. In this embodiment, first surface 26a extends in one direction from outer surface <NUM> to nose <NUM> and in a second direction around an outer circumference of pipe <NUM>. Second surface 26b extends in one direction from inner surface <NUM> to nose <NUM> and in a second direction around an inner circumference of pipe <NUM>. The location of nose <NUM> is different from the position of nose <NUM> shown in <FIG>. In <FIG>, the nose is located at one end of the torque shoulder <NUM> at an outer surface of the pin <NUM> and at or near the pin seal surface <NUM>. As shown in <FIG>, nose <NUM> is not located at one end of the pin torque shoulder <NUM>. Instead nose <NUM> is in a middle or central part of pin torque shoulder <NUM> with regard to a length of shoulder <NUM> in the profile view. The shape of nose <NUM> may vary and can be, for example, angular, socket, a flattened edge, a bull nose, bulb, cone, rounded, fishtail, etc. A depression <NUM> is located along a length of torque shoulder <NUM> in a direction perpendicular to the longitudinal axis and is a vertex connecting first surface 126a and second surface 126b. In this embodiment, the geometry of nose <NUM> and depression <NUM> are complementary so nose <NUM> and depression <NUM> fit together when pin <NUM> is screwed into connector <NUM>; depression <NUM> contacts nose <NUM> and pin shoulder <NUM> contacts box shoulder <NUM>.

The difference in width between standoff Sa and standoff Sb occurs because nose <NUM> is not initially aligned with depression <NUM> with respect to the longitudinal axis. As shown in <FIG> and <FIG>, nose <NUM> is situated below depression <NUM>. This offset between nose <NUM> and depression <NUM> forces pin <NUM> to bend upwards as nose <NUM> is received in depression <NUM>. Bending pin <NUM> forces nose <NUM> into depression <NUM> and results in a tighter connection. In a different embodiment, nose <NUM> may be situated above depression <NUM> so the pin is forced to bend downwards thereby also resulting in a tighter connection. See, for example, <FIG>.

<FIG> show the third stage of make-up, a first shoulder tight position, which occurs after further rotation of pin <NUM> with respect to box <NUM>. The seal surfaces <NUM>, <NUM> are forced together by screwing pin <NUM> into box <NUM> until torque shoulders <NUM>, <NUM> contact one another. In this preferred embodiment, for example, the complementary second surfaces 26b, 126b just contact one another. As a result, the standoff Sb between second surfaces 26b, <NUM> is eliminated. However, standoff Sa between complementary first surfaces 26a, 126a still exists. Additional rotation has not yet occurred after the point of contact between shoulders <NUM>, <NUM> so there is no additional torque force applied to shoulders <NUM>, <NUM>, in this position. A distance S1 in the radial direction exists between the edge of pin <NUM> and surface BS of box <NUM>. The relative angles of seal surfaces <NUM>, <NUM>, force apart an edge of pin <NUM> and surface BS of box <NUM> by an amount of seal interference S1 designed into the connection to provide sufficient contact pressure in order to form a leak tight seal.

The fourth stage of make-up, a second shoulder tight position, occurs after further rotation of pin <NUM> with respect to box <NUM>. The seal surfaces <NUM>, <NUM> are further forced together by screwing pin <NUM> into box <NUM> until torque shoulder first surfaces 26a, 126a contact one another. The radial distance S1 is reduced by the amount of the radial offset between vertices <NUM>, <NUM>. Forcing the end of the pin radially outward forces the seal surfaces <NUM>,<NUM> tighter together creating a better seal. The V shape between the first and second shoulder surfaces keeps gap S1 from being zero and causing undesirable contact between the box and pin.

The fifth and final stage of making up the connection is the power tight position. During the power tight stage additional torque is applied to torque shoulders <NUM>, <NUM> but very little additional rotation occurs, about <NUM> turns, for example. Because very little additional rotation occurs, the power tight position for the connection looks like the shoulder tight position shown in <FIG>.

The amount of torque build up is a function of friction, stiffness of the pin, stiffness of the box around the seal area, the amount of thread interference, if any, the lubricant and the amount of interference in the seals. Once seal surfaces <NUM>, <NUM> contact each other, torque begins to build up rapidly. The torque build up is caused by seal surfaces <NUM>, <NUM> being wedged together. The torque continues increasing at an approximately constant rate until the shoulders <NUM>, <NUM> contact in the shoulder tight position. The torque builds up extremely rapidly after shoulders <NUM>, <NUM> contact one another. Once shoulders <NUM>, <NUM> contact, additional torque is applied until the pre-determined power tight position is reached and the desired amount of torque is achieved. Very little additional rotation of the connection is needed to reach the desired final make-up torque, for example, approximately <NUM> turns.

<FIG> shows a cross section view of a torque shoulder embodiment in accordance with the present invention. As shown in <FIG>, in the embodiment of <FIG>, pin <NUM> is designed as a male component and box <NUM> is designed as a female component so box <NUM> can receive pin <NUM>. In this embodiment, pin torque shoulder <NUM> and box torque shoulder <NUM> both have a V-shaped cross section. Pin seal surface <NUM> and box seal surface <NUM> are spaced apart from each respective torque shoulder <NUM>, <NUM>, with respect to a longitudinal axis (not shown) defined by the connection of the pipe and connector. Torque shoulders may also have cross sections of another shape or design.

The V shaped extension of pin torque shoulder <NUM> engages with the V shaped receptacle of box torque shoulder <NUM> to reduce or prevent movement of pin <NUM> in multiple directions, e.g., radially inward or outward. For example, first surfaces 26a, 126a prevent pin <NUM> from being driven upwards into a corner of box <NUM> by keeping the nose <NUM> of pin <NUM> down. And, second surfaces 26b, 126b prevent externally applied pressure from forcing pin <NUM> inward which deenergizes seal surfaces <NUM>, <NUM>.

An interior angle Va is formed between first surfaces 26a, 126a and axis P. Interior angle Va may be <NUM>°, which is <NUM>° in the counter-clockwise direction with respect to axis P. An interior angle Vb is formed between second surfaces 26b, 126b and axis P. Interior angle Vb may be -<NUM>°, which is <NUM>° in the clockwise direction with respect to axis P. Angles Va, Vb may vary and be, for example, from <NUM> to <NUM>°, -<NUM> to -<NUM>°, respectively. In addition, interior angle Va may be different from or equal to an absolute value of interior angle Vb. For example, as shown in <FIG>, angle Va is <NUM>° and is not equal to an absolute value of angle Vb which is -<NUM>° because <NUM>° # |-<NUM> °| so Va ≠ |Vb|. In another example, angle Va may be <NUM>° and angle Vb may be -<NUM>° in which case Va ≠ |Vb| because <NUM>° ≠ |-<NUM>°|.

As shown in <FIG>, nose <NUM> and depression <NUM> are located at or near a center torque shoulders with respect to a length of shoulders 26a, 26b, 126a, 126b in the direction of axis P. First pin surface 26a has the same or near similar length to second pin surface 26b and first box surface 126a has the same or similar length to second box surface <NUM>. In the <FIG> embodiment, nose <NUM> and depression <NUM> serve as the vertex of interior angles Va, Vb however, this is a non-limiting example of a preferred embodiment. The geometry of torque shoulders <NUM>, <NUM> including nose <NUM>, depression <NUM> and angles Va, Vb is variable. Different shapes and positions of vertices may be used. Different shapes or angles of surfaces 26a, 26b, 126a, 126b or Va, Vb may be used. For example, the position of nose <NUM> does not have to be in a center of torque shoulder <NUM> but instead could be located closer to inner surface <NUM> than outer surface <NUM>.

As shown in another preferred embodiment in <FIG>, first surfaces 26a, 126a are longer than second surfaces 26b, 126b and first angle Va is greater than the absolute value of second angle Vb. <FIG> shows first surfaces 26a, 126a are shorter than second surfaces 26b, 126b and first angle Va is less than second angle Vb. The geometry of first surfaces 26a, 126a, second surfaces 26b, 126b and vertices (nose, depression) <NUM>, <NUM> are designed to produce the desired results. As discussed above, the vertices <NUM>, <NUM> may be initially mis-aligned to force an end of the pin down in order to straighten out or minimize bending of the pin, for example. Or, for example, the end of pin <NUM> may need to be forced up in order to increase contact pressure on the seals <NUM>, <NUM>.

<FIG> shows another preferred embodiment of torque shoulders <NUM>, <NUM> in which the shoulders <NUM>, <NUM> have a bullet, bull nose or curved shape cross section as opposed to the V shaped cross section shown in <FIG>. First surface 26a has a first radius Ra, second surface 26b has a second radius Rb, first surface 126a has a third radius Rc and second surface 126b has a fourth radius Rd. First and third radii Ra, Rc, may be different from or equal too second and fourth radii, respectively Rb, Rd. Nose <NUM> is located between first surface 26a and second surface 26b. Depression <NUM> is located between first surface 126a and second surface 126b. As discussed above with respect to the V-shaped cross section embodiment, first surfaces 26a, 126a, second surfaces 26b, 126b and radii Ra, Rb, Rc, Rd and vertices may be adjusted to force pin <NUM> up or down to trap pin <NUM> in a desired position with respect to the box <NUM>. In another embodiment the pin may having a single surface with a single radius and the box may have a single surface with a single radius. In this embodiment, the pin radius and box radius may or may not be equal and centerlines of the radii may or may not be the same distance from the axis. If the two radii are offset radially with respect from each other then the end of the pin will be either forced upwards or downwards, depending upon how the two radii are offset.

The V shaped cross section and bull nose cross section designs of torque shoulders <NUM>, <NUM> is advantageous over the prior art because the male and female geometry traps or constrains pin in a radial position within the box and thereby reducing or preventing movement of the pin. By adjusting the design of shoulders <NUM>, <NUM>, bending, bowing or deflection of the pin may be compensated for or minimized. In addition, the contact pressure of the seal surfaces <NUM>, <NUM> maybe increased. Other benefits may be derived therefrom as well.

Preferably, first and second angles Va, Vb or first and second radii Ra, Rb are designed to be small enough so a larger component of force F acting on pin <NUM> is an axial component A and not a radial component R.

<FIG> show a torque shoulder connection for a pin and box in which the V-shaped shoulder design is inverted compared to the embodiments shown in <FIG>. In this embodiment, pin <NUM> is a female member and box <NUM> is a male member. Box <NUM> includes a box seal surface <NUM>, first shoulder surface 326a, second shoulder surface 326b. A nose <NUM> is formed between first shoulder surface 326a and second shoulder surface 326b. Pin <NUM> includes a pin seal surface <NUM>, first shoulder surface 226a and a second shoulder surface 226b. A depression <NUM> is formed between first shoulder surface 226b and second shoulder surface 226b. In this embodiment, the vertex between box surfaces 326a and 326b forms nose <NUM> and the vertex between pin surfaces 226a and 226b forms depression <NUM>. Nose <NUM> and depression are complementary surfaces so nose <NUM> is received in depression <NUM> by rotation of pin <NUM> in box <NUM> in the same manner as discussed above with respect to <FIG>. This inverted shoulder design may also apply to the bull nose embodiment shown in <FIG>.

<FIG> show a torque shoulder connection wherein the pin <NUM> and box <NUM> have different shoulder surface geometries and vertices <NUM> and <NUM> are not complementary with one another according to a further preferred embodiment of the present invention. <FIG> shows a pin <NUM> having a rounded or bull nosed shoulder surface <NUM> with a first shoulder surface 526a and a second shoulder surface 526b. A vertex <NUM> is located between the first shoulder surface 526a and second shoulder surface 526b. Box <NUM> includes a v-shaped box shoulder surface <NUM> with a first shoulder surface 426a and second shoulder surface 426b. A vertex <NUM> is located between the first shoulder surface 426a and second shoulder surface 426b. Pin <NUM> and box <NUM> contact one another in the same manner as described above with respect to <FIG>. Rotation of pin <NUM> into box <NUM> provides for contact of first shoulder surface 526a with first shoulder surface 426a and for contact of second shoulder surface 526b with second shoulder surface 426b. In the embodiments shown in <FIG>, vertex <NUM> and vertex <NUM> may not be in contact with one another due to the different surface geometries of shoulder <NUM> and shoulder <NUM>. A gap or space <NUM> will be present between vertices <NUM>, <NUM> after makeup. Also, due to the variation in geometry and design of shoulder surfaces <NUM>, <NUM>, shoulder surfaces <NUM>, <NUM> will not be in contact with one another along a portion of surfaces <NUM>, <NUM>.

<FIG> shows a pin <NUM> having a v-shaped pin shoulder surface <NUM> and a box <NUM> with a rounded or bull nosed box shoulder surface <NUM>. Pin shoulder surface <NUM> has a first shoulder 526a and a second shoulder surface 526b. A vertex <NUM> is located between the first shoulder surface 526a and second shoulder surface 526b. Box shoulder surface <NUM> has a first shoulder surface 426a and second shoulder surface 426b. A vertex <NUM> is located between the first shoulder surface 426a and second shoulder surface 426b. Pin <NUM> and box <NUM> contact one another in the same manner as described above with respect to <FIG> and <FIG>. Rotation of pin <NUM> into box <NUM> provides for contact of first shoulder surface 526a with first shoulder surface 426a and for contact of second shoulder surface 526b with second shoulder surface 426b. A space <NUM> is present between vertices <NUM> and <NUM>.

In <FIG>, the pin <NUM> and box <NUM> may be designed so that vertices <NUM> and <NUM> are aligned with each other so pin shoulder surfaces 526a, 526b contact box shoulder surfaces 426a, 426b at the same time when pin <NUM> is being inserted into box <NUM> during make-up. Alternatively, the shoulder surfaces <NUM>, <NUM> and vertices <NUM>, <NUM> may be designed so first shoulder surfaces 526a, 426a contact first, then second shoulder surfaces 526b, 426b contact as pin <NUM> is further screwed into box <NUM>. In another variation, the shoulder surfaces <NUM>, <NUM> and vertices <NUM>, <NUM> may be designed so second shoulder surfaces 526b, 426b contact first, then first shoulder surfaces 526a, 426a contact as pin <NUM> is further screwed into box <NUM>.

Shoulder surfaces <NUM>, <NUM> may be designed with a variety of geometries, including, but not limited to, bull nose, bullet shaped, angular, rounded or fishtail, for example.

Claim 1:
A threaded tubular connection (<NUM>) comprising:
a pin (<NUM>), the pin (<NUM>) having external threads, a pin seal surface (<NUM>), and a pin torque shoulder (<NUM>) at a free end; and
a box (<NUM>, <NUM>') for receiving the pin (<NUM>), the box (<NUM>, <NUM>') having internal threads for interacting with the external threads, a box seal surface (<NUM>) for contacting the pin seal surface (<NUM>), and a box torque shoulder (<NUM>) for contacting the pin torque shoulder (<NUM>), the pin seal surface (<NUM>) being axially spaced apart from the pin torque shoulder (<NUM>);
the pin (<NUM>) and box (<NUM>, <NUM>') defining a longitudinal axis,
the pin torque shoulder (<NUM>) having a first pin shoulder surface (26a) and a second pin shoulder surface (26b), the first pin shoulder surface (26a) intersecting an axis perpendicular to the longitudinal axis at a first angle, the second pin shoulder surface (26b) intersecting the perpendicular axis at a second angle, the first pin shoulder surface (26a) and the second pin shoulder surface (26b) meeting at a pin vertex (<NUM>), and
the box torque shoulder (<NUM>) having a first box shoulder surface (126a) and a second box shoulder surface (126b), the first box shoulder surface (126a) intersecting an axis perpendicular to the longitudinal axis at a third angle, the second box shoulder surface (126b) intersecting the perpendicular axis at a fourth angle, the first box shoulder surface (126a) and the second box shoulder surface (126b) meeting at a box vertex (<NUM>),
the first pin shoulder surface (26a) and the first box shoulder surface (126a) being top torque shoulder surfaces and the second pin shoulder surface (26b) and the second box shoulder surface (126b) being bottom torque shoulder surfaces,
characterized in that
the pin torque shoulder geometry is not complementary with the box torque shoulder geometry and
a gap is present between the pin vertex (<NUM>) and the box vertex (<NUM>) after makeup of the threaded connection.