Patent Description:
The present description relates generally to threaded connections in drill string components, such as drilling tubulars and downhole tools. More specifically, the description relates to multiple tapered threaded connections provided on drilling tubulars and other drill string (or downhole) tools.

This section provides background information to facilitate a better understanding of the various aspects of the invention. It should be understood that the statements in this section of this document are to be read in this light, and not as admissions of prior art.

In oil and gas drilling a drill bit is generally threadably attached to the end of a drill stem and rotated in order to form a borehole. A drill stem is traditionally comprised of a variety of sub-assemblies and tubulars such as the Bottom Hole Assembly (BHA), Heavy Weight Drill Pipe (HWDP) and drill pipe. The BHA may include a variety of downhole tools and tubulars such as a rotary steerable tool, a mud motor, Measurement-While-Drilling (MWD) tools, Logging-While-Drilling (LWD) tools, a configuration of stabilizers, reamers, jars, shocks, agitators, and multiple drill collars among other modern drilling technologies. Connected to the BHA is a configuration of drilling tubulars including HWDP and drill pipe which couple the drill bit and BHA back to the surface completing the drill string and affording for surface rotation, compression and tension to be applied to the drill bit in advancing the borehole. Having a sufficiently hollow inside diameter the assembled drill string also functions as a conduit for pumping drilling fluid through the drill string to clean the borehole, provide hydraulic power to downhole tools and provide cooling of heat generated by the drill bit or downhole tools. It is common that all of these drill string tubulars and sub-assemblies are threadably attached to one another to allow for sequential assembly of the drill string at surface as the borehole is advanced further. This then also allows for the sequential disassembly of the drill string upon reaching the target borehole depth or if the need to service downhole components arises and the drill string must be tripped out and removed from the borehole and subsequently reassembled to be tripped back in after servicing the necessary downhole components on surface. In addition to tubular members, a drill string may also comprise one or more tools connected to adjacent tubular members or to other tools. Examples of such tools making up a drill string include drill collars, motors (such as mud motors), jar tools (for freeing stuck pipe), joints (for connecting tubulars and/or tools to each other), stabilizers, subs (short pipe joints), shock subs, reamers etc. Various other drill pipe tools will be known to persons skilled in the art. It will also be understood that each of these tools, like the tubulars, have opposing ends that are adapted to be connected to adjacent tubular members or other tools to form the drill string. For the purpose of the present description, the term "drill string components" will be understood to mean tubular members or other tools that are used to form a drill string.

During drilling operations it is desirable that all of the aforementioned threaded connections between adjacent drill string tubulars possess sufficient mechanical capabilities to withstand the loads placed on them during drilling operations (e.g. torsional, tensile, compressive loads). Traditionally these threaded connections have been known as rotary shouldered connections and have a taper between <NUM> to <NUM> inches per foot (<NUM> to <NUM> per <NUM>), a given threadform and a single torque bearing shoulder. Modern variants of rotary shouldered connections have introduced a secondary torque bearing shoulder on the nose of the pin connection which contacts the rear of the box connection when the pin connection is threadably engaged with the box connection.

To maximize the torsional capability of the rotary shouldered connection the taper of modern connections may range from. <NUM> to <NUM> inches per foot (<NUM> to <NUM> per <NUM>) as described in <CIT>.

The largest issue with low taper thick walled connections have been difficulties in the handling and threading together of adjoining drilling tubulars. Due to the low taper, the male connection end does not stab deep into the female connection end. This results in many revolutions of the male connection end to fully engage into the female connection end. This adds undesirable time to the threading process on surface which is costly, and typically results in increased damage to the threads and a high repair cost.

It is desirable that a rotary shouldered connection provide the necessary mechanical strength capabilities during drilling operations and effective handling characteristics during assembly and disassembly of the drill string tubulars and subassemblies.

In attempts to provide such a rotary shouldered connection a double or triple step/start thread design on low taper connections have been used. The issue with this type of connection is that the male connection end stabs on a pair of thread flanks instead of on multiple thread flanks. These connections are equally difficult to manufacture and dimensionally control, leading to high repair and service cost. These multi step/start threads have also exhibited poor ability to hold torsional energy and often back-off and unthread with relatively low amounts of reverse torque applied. These connections have ultimately been phased out of common usage in the industry.

<CIT> discloses a tubular threaded joint with trapezoid threads having a convex bulged thread surface. <CIT> discloses a tubular connection with a helically extending torque shoulder. <CIT> discloses an oilfield tubular connection with increased compression capacity. <CIT> describes a threaded connection for use on oil field tubular. The connection comprises a dual helical thread having a first, straight threaded portion and a second, angled portion, the threaded connection comprising a pin connection and a box connection both of which have thread free sections. The thread free section on the pin and the box are comprised of frustoconical surfaces and cylindrical surfaces.

<CIT> describes a threaded pipe coupling for connection with a conventional threaded pipe end so as to effect improved sealing against internal fluid pressure and against external fluid pressure as may be required in an oil or gas well.

<CIT> describes a threaded interconnect structure incorporating respective matching internal and external threaded portions of members to be threadedly interconnected, with the thread geometry defining a profile having contiguous straight thread and tapered thread sections. The taper is in excess of standard - taper-threaded profiles and comprises comparatively fewer threads, with the sealing action in the tapered section being mechanically aided by the straight thread sections during make up of the joint.

<CIT> describes a joint which may be quickly made and broken and which is especially adapted for pipelines. Tapered mating portions of a telescopic joint are provided with a continuous helical thread of which certain turns have been partially truncated.

<CIT> describes a coupling for joining together tubular sections. The coupling includes a water exclusion seal which is a pressure energised elastomeric seal positioned in a groove near each end of the coupling to form a seal between the unthreaded area at each end of the coupling and the unthreaded cylindrical area adjacent each end of the tubular section. <CIT> discloses tubular connection. <CIT> discloses oilfield tubular connection with increased compression capacity.

According to one aspect of the invention there is provided a pair of drill string connectors as claimed in claim <NUM>. Another aspect of the invention provides a method as claimed in claim <NUM>.

In certain embodiments as described herein there is provided a multiple tapered threaded connection having a longitudinal axis. A female connection end has internal threads. The internal threads have a first end, a second end, a first portion and a second portion. The first portion of the internal thread is adjacent the first end of the internal thread and has a first taper. The second portion of the internal thread is adjacent the second end of the internal thread and has a second taper that is different from the first taper. A male connection end has external threads. The external threads have a first end, a second end, a first portion and a second portion. The first portion and the second portion of the male connection correspond to the first portion and the second portion of the female connection. The first portion of the external threads is adjacent the first end of the external threads and has a first taper corresponding to the first taper of the female connection. The second portion of the external threads is adjacent the second end of the external threads and has a second taper that corresponds to the second taper of the female connection.

The second taper is steeper than the first taper. The first taper may have a taper of <NUM> inches per foot (<NUM> per <NUM>) and the second taper may have a taper of <NUM> inches per foot (<NUM> per <NUM>) to the longitudinal axis.

In one embodiment, transitional threads are provided between the first taper and the second taper for creating a continuous thread. The transitional threads may be shorter in height than the internal threads of the female connection end and the external threads of the male connection end. This can help to prevent excessive damage to the threads during stabbing operations.

In one embodiment, the male connection end includes a male external shoulder configured to engage a female external shoulder on a mating female connection end when the male connection end is threadably engaged with the female connection end.

In a further embodiment, the male connection end includes a male external shoulder configured to engage a female external shoulder on a mating female connection end and a male internal shoulder axially spaced from the male external shoulder configured to engage a female internal shoulder on the female connector end axially spaced from the female external shoulder when the male connection end is threadably engaged with the female connection end.

In one embodiment, each thread within the first portion of the internal threads and the first portion of the external threads includes a crest, a root, a load flank extending between the crest and the root and a stab flank extending between the crest and the root. Each thread within the second portion of the internal threads and the second portion of the external threads includes a crest, a root, a load flank extending between the crest and the root and a stab flank extending between the crest and the root. The stab flank on the internal threads is more proximate the female connection end external shoulder. The load flank on the external threads is more proximate the male connection end external shoulder.

In one embodiment each thread within the first portion of the internal threads and the first portion of the external threads includes a crest, a root, a load flank extending between the crest and the root and a stab flank extending between the crest and the root. Each thread within the second portion of the internal threads and the second portion of the external threads includes a crest, a root, a load flank extending between the crest and the root and a stab flank extending between the crest and the root. The stab flank on the internal threads is more proximate the female connection end external shoulder. The load flank on the external threads is more proximate the male connection end external shoulder. The thread crest, root, load flank and stab flank of threads within the first portion of the internal and external thread correspond to the thread crest, root, load flank and stab flank of the threads within the second portion of the internal and external thread.

In another embodiment there is also provided a multiple tapered threaded connection. A female connection end has internal threads. The internal threads have a first end, a second end, a first portion with a first taper, a second portion with a second taper and a third portion with a third taper. The first portion is adjacent the first end of the internal threads. The second portion is adjacent to the first portion. The third portion is adjacent to the second portion and the second end of the internal threads. The taper of adjacent portions are different from each other. A male connection end has external threads. The external threads have a first end, a second end, a first portion with a first taper, a second portion with a second taper and a third portion with a third taper. The first portion is adjacent the first end of the external threads. The second portion is adjacent to the first portion. The third portion is adjacent to the second portion and the second end of the external threads. Each of the first taper, the second taper and the third taper correspond to the first taper, the second taper and the third taper of the female connection.

In one embodiment, transitional threads are provided between the first taper and the second taper and between the second taper and the third taper for creating a continuous thread. The transitional threads may be shorter in height than the internal threads of the female connection end and the external threads of the male connection end. This can help to prevent excessive damage to the threads during stabbing operations.

In one embodiment, the second taper is steeper than the third taper.

In one embodiment, the third taper is steeper than the second taper and the second taper is steeper than the first taper.

In one embodiment, the first taper and the third taper are the same.

In one embodiment, the first taper and the third taper are the same and the second taper is steeper than the first taper and the third taper.

In one embodiment, the first taper is steeper than the third taper.

In one embodiment , the third taper is steeper than the second taper.

In one embodiment, the third taper is steeper than the first taper.

In one embodiment, the second taper is steeper than the first taper and the first taper is steeper than the third taper.

In one embodiment, the second taper is steeper than the third taper and the third taper is steeper than the first taper.

In another embodiment there is also provided a multiple tapered threaded connection. A female connection end has internal threads. The internal threads have a first end, a second end and at least three portions. Each of the at least three portions have a taper such that the taper of adjacent portions are different from each other. A male connection end has external threads. The external threads have a first end, a second end and at least three portions corresponding to the at least three portions of the female connection. Each of the at least three portions have a taper corresponding to the taper of the at least three portions of the female connection. The taper of adjacent portions are different from each other.

In one embodiment, transitional threads are provided between the at least three portions for creating a continuous thread. The transitional threads may be shorter in height than the internal threads of the female connection end and the external threads of the male connection end. This can help to prevent excessive damage to the threads during stabbing operations.

In another embodiment there is also provided a multiple tapered threaded connection. A female connection end has internal threads. The internal threads have a first end, a second end and at least two portions. Each of the at least two portions has a taper such that the taper of adjacent portions are different from each other. A male connection end has external threads. The external threads have a first end, a second end and at least two portions. Each of the at least two portions having a taper such that the taper of adjacent portions are different from each other. At least a portion of at least one portion of the internal threads of the female connection end corresponds to at least a portion of at least one portion of the external threads of the male connection end such that a threaded connection is made between the at least one portion of the internal threads and the at least one portion of the external threads.

In one embodiment, the internal threads of the female connection end have two portions and the external threads of the male connection end have three portions. At least a portion of at least one of the two portions of the internal threads corresponds to at least a portion of at least one of the three portions of the external threads.

In another embodiment, the internal threads of the female connection end have three portions and the external threads of the male connection end have two portions. At least a portion of at least one of the two portions of the external threads corresponds to at least a portion of at least one of the three portions of the internal threads.

In one embodiment, transitional threads are provided between the at least two portions for creating a continuous thread. The transitional threads may be shorter in height than the internal threads of the female connection end and the external threads of the male connection end. This can help to prevent excessive damage to the threads during stabbing operations.

Thus, in one aspect, there is provided. a pair of drill string connectors for forming a threaded connection between first and second drill string components, the pair of drill string connectors comprising:.

These and other features will become more apparent from the following description in which references are made to the following drawings, in which numerical references denote like parts. The drawings are for the purpose of illustration only and are not intended to in any way limit the scope of the invention to the particular embodiments shown.

As used herein, the term "taper" refers to a change in diameter over a given length and may be expressed in various units of measurement and methods. In the context of the present description, a taper is provided along at least a portion of an elongate member, such as a drill string tubular.

The units of measurement and methods of describing tapers as used herein are not meant to limit the scope of the invention and should be interpreted in the broadest sense possible. For instance, a taper of <NUM> inches per foot (<NUM> per <NUM>) would be equivalent to roughly <NUM> (or, generally, <NUM>) inches per inch and would also be equivalent to <NUM> radial inch per foot (<NUM> radial mm per <NUM>) or a half angle taper of <NUM> (or, generally, <NUM> or <NUM>) degrees from the longitudinal axis. As would be known to persons skilled in the art, a taper that is measured in, for example, inches per foot, refers to the change in diameter of the surface of the tapered portion about the longitudinal axis of the elongate member or an axis parallel to the longitudinal axis.

In the present description, tapers may be described in a relative sense using the term "different". It will be understood that such term is intended to indicate a variation or change in a given taper. In one example, a taper may be characterized as being "different" from another taper if it comprises a variation of approximately <NUM>" or more per foot (<NUM> per <NUM>).

Tapers may also be described herein with the relative terms "steeper" or "shallower". In particular, these terms are intended to characterize the angle of the taper, or portion of the taper, with respect to the longitudinal axis of the elongate member on which the taper is provided. It will be understood that a taper may be characterized as "steep" if it forms more of an angle with the longitudinal axis than a taper that forms a lesser angle with the longitudinal axis, with the opposite being the case for a "shallow" taper.

The phrase "multiple taper" as used herein is intended to refer to a taper that includes a difference in steepness along its length. That is, a taper having one portion that is steeper than another portion will be referred to as a multiple taper.

The term "adjacent" as used herein is intended to be non-limiting and should be construed to mean "neighboring" or "nearest in physical proximity", and should not be construed to require physical contact.

The terms "male connection" and "female connection" should be interpreted equivalent to "pin connection" and "box connection", respectively, as these terms are known in the art. Thus, a pin or male connection end comprises a portion at one end of a tubular having a threaded external surface. Similarly, a box or female connection end comprises a portion at one end of a tubular having a threaded internal surface.

Any references herein to "top" or "bottom" are made for purposes of clarity and should not be interpreted to imply any direction relative to a borehole or other external frames of reference.

Any references herein to sequencing, such as "first", "second", "third" etc., are made solely for the purpose of facilitating the description of relative locations and relationships between features and should not be interpreted to imply any particular ordering, capability, priority or physical location of features relative to a borehole or other external frames of reference.

As would be understood by persons skilled in art, the use herein of the term "stub" or "stubbed" generally describes a thread form that has been manufactured with a truncated thread form height but is otherwise accurate to said thread form.

The use of the term "correspond" or "corresponding" when describing a relationship between male and female connection features should be interpreted as indicating that the features being described are substantially compatible and complementary but not necessarily identical in terms of location, diameter, length, taper or thread form. Thus, as would be understood by persons skilled in the art, a male threaded element will be referred to one that "corresponds" to a given female threaded portion if the two elements can be connected to each other in a threaded manner.

A tapered threaded connection, as defined herein, is formed by a first longitudinal member having a female connection end that is threadably connected to a male connection end of another longitudinal member. Thus, a multiple tapered threaded connection is formed by a multiple tapered female connection end that is threadably connected to a multiple tapered male connection end. Such multiple tapered connection, including a multiple tapered male end and a multiple tapered female end, is described herein and illustrated in the accompanying figures. It will be understood that, for the purposes of the present description, the term "longitudinal member" may refer to a drill string tubular or a coupling used to connect to at least one drill string tubular forming a drill string. It will be appreciated that the connection described herein may be used for any connection between tubular members or for any connection between tubular members and other tools etc. that form a drill string.

Referring first to <FIG>, a multiple tapered threaded connection <NUM> is formed from a female connection, or "box" end <NUM>, provided at an end of a first longitudinal member and a male connection, or "pin" end <NUM>, provided at an end of a second longitudinal member. Referring to <FIG>, the female connection end <NUM> has internal threads <NUM>.

Referring to <FIG>, the male connection end <NUM> has external threads <NUM> that correspond to internal threads <NUM> of the female connection end <NUM>, shown in <FIG>.

Referring to <FIG>, internal thread <NUM> has a first or "top" end <NUM>, a second or "bottom" end <NUM>, a first portion <NUM> and a second portion <NUM>. The first portion <NUM> of the internal thread <NUM> is located proximal to the first end <NUM> of internal thread <NUM> and has a first taper, shown at <NUM>. Second portion <NUM> of the internal thread <NUM> is located proximal to the second end <NUM> of the internal thread <NUM> and has a second taper, shown at <NUM>. In this way, the female or box connection end <NUM> is provided with a female end or box profile.

In <FIG>, the first portion <NUM> and the second portion <NUM> are illustrated as being of substantially the same length; however, it will be understood by persons skilled in the art that first portion <NUM> and second portion <NUM> may also be of different lengths.

In <FIG>, the second taper <NUM> of the internal thread <NUM> is illustrated as being steeper than first taper <NUM>. However, according to other aspects of the description, such as illustrated in <FIG> and <FIG>, the first taper <NUM> may be steeper than second taper <NUM>. In either case, by providing different tapers in the thread, the stress distribution within the connection may be altered in a desirable fashion. In this regard, the effect of the taper angle on stress distribution was discussed above. This feature of the present description is also discussed further below.

Referring to <FIG>, a male connection end <NUM> of the present description has an external thread <NUM> having a first end <NUM>, a second end <NUM>, a first portion <NUM> and a second portion <NUM>. When connected to a female connection end, first portion <NUM> and second portion <NUM> of male connection end <NUM> are positioned so as to correspond, respectively, with first portion <NUM> and second portion <NUM> of the female connection end <NUM>, as illustrated in <FIG>. Referring to <FIG>, the first portion <NUM> of the male connection end <NUM> is located proximal to the first end <NUM> of external thread <NUM> and has a first taper shown at <NUM>. Similarly, the second portion <NUM> of the male connection end <NUM> is located proximal to the second end <NUM> of external thread <NUM> and has a second taper <NUM>. In this way, the male or pin connection end <NUM> is provided with a male end or pin profile. As will be understood, in order for the pin end to engage the box end, the pin profile will correspond at least generally to the box profile. Thus, for forming a connection between the pin an box ends, threads <NUM> and <NUM> would be adapted to correspond with, and thereby threadably engage each other, the first taper <NUM> of the box end would correspond with the first taper <NUM> of the pin end, and the second taper <NUM> of the box end would correspond with the second taper <NUM> of the pin end.

In <FIG>, first portion <NUM> and second portion <NUM> are illustrated as being substantially the same length; however, it will be understood by persons skilled in the art that first portion <NUM> and second portion <NUM> may also be of different lengths.

In <FIG>, second taper <NUM> is illustrated as being steeper than first taper <NUM>. However, according to other aspects, such as illustrated in <FIG> and <FIG>, the first taper <NUM> may be steeper than second taper <NUM>. As discussed above, by providing different tapers, the stress distribution within the connection may be altered in a desirable fashion.

As shown in <FIG>, first tapers <NUM> and <NUM> of the box and pin ends, respectively, create a connection <NUM> that is thick-walled in both the pin and box portions. As would be understood, such an arrangement would serve to maximize torque capability of the connection in higher stressed regions of connections. As also shown in <FIG>, according to the illustrated aspect of the description, the second tapers <NUM> and <NUM> of the box and pin ends, respectively, comprise steeper tapers, which permit deep stabbing in lower stressed regions of connections <NUM>. Such an arrangement allows for a quick make-up and reduces damage without compromising the overall torque carrying capabilities of the connections <NUM>.

According to one aspect, and as shown in <FIG>, the first tapers <NUM> and <NUM> may have a taper of <NUM> inches per foot (<NUM> per <NUM>) while the second tapers <NUM> and <NUM> may have a steeper taper of <NUM> inches per foot (<NUM> per <NUM>). In another aspect, the first tapers may be <NUM> inches per foot (<NUM> per <NUM>) while the second tapers are <NUM> inches per foot (<NUM> per <NUM>). Other tapers for both the first and second tapers are encompassed by the present description. Generally, in one aspect, the ratio of the second tapers to the first tapers is from about <NUM>:<NUM> to about <NUM>:<NUM>. This range includes the ratios <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, and <NUM>:<NUM>. The steeper taper of second tapers <NUM> and <NUM> allows for deeper stabbing of male connection end <NUM> into female connection end <NUM> while the shallower taper of first tapers <NUM> and <NUM> allows for a thicker wall for each of male connection end <NUM> and female connection end <NUM>. As discussed further below, in other aspects, the present description encompasses situations where one of the first or second taper has a taper of <NUM> inches per foot (<NUM> per <NUM>), that is, no taper.

Referring to <FIG>, a transitional thread <NUM> may optionally be provided as a junction between the thread of first taper <NUM> and the thread of the second taper <NUM> of internal thread <NUM>. In this way, the thread <NUM> is continuous. In one aspect, the transitional thread <NUM> may comprise between two and four thread rotations; however, it will be understood by persons skilled in the art that more or fewer transitional thread rotations may be used. The number of rotations of the transitional thread <NUM> can, for example, vary based upon the diameter of the connection, the connection length, and/or the pitch of the threads.

Referring to <FIG>, and in a similar manner as discussed above, a transitional thread <NUM> may also be provided on the pin end, so as to form a junction between the threads of first taper <NUM> and second taper <NUM> of external thread <NUM>, so as to result in the external thread being continuous. The transitional thread <NUM> of external thread <NUM> of the pin end may optionally be designed to cooperate with the transitional thread <NUM> of the internal thread <NUM> of the box end. However, in other aspects of the present description, the transitional threads <NUM> and <NUM> may be independent of each other with no engagement there-between.

Generally, transitional thread <NUM> may comprise two to four thread rotations; however, it will be understood by persons skilled in the art that more or fewer transitional thread rotations may be provided. The number of rotations of the transitional thread <NUM> can vary based upon the diameter of the connection, the connection length and/or the pitch of the threads.

Referring to <FIG> and <FIG>, another aspect of the description is illustrated. As shown in <FIG>, the first portion <NUM>, with first taper <NUM>, and the second portion <NUM>, with second taper <NUM>, of external thread <NUM> of pin end <NUM> may optionally be spaced apart from each other by a relatively blank space or spacer segment <NUM>. As will be understood, where a spacer segment <NUM> is included, the thread <NUM> would not be continuous. The size or length of the spacer segment <NUM> may vary. Referring to <FIG>, first portion <NUM>, with first taper <NUM>, and second portion <NUM> with second taper <NUM>, of internal thread <NUM> of box end <NUM> may be similarly spaced apart from each other by a spacer segment <NUM>, thereby resulting in internal thread <NUM> being discontinuous. As described above, the size of spacer segment <NUM> may also vary. In one aspect, the profiles of the pin and box ends may be sized to correspond with each other. As will be understood, the spacer segments <NUM> and <NUM> are provided as an alternative to the transitional threads discussed above. It will also be understood that in some aspects one of the pin and box may include a transitional thread while the other of the pin and box may include a spacer segment.

<FIG> illustrates another optional aspect of the present description, wherein the first taper <NUM> of the pin end <NUM> has a taper of zero inches per foot (<NUM> per <NUM>), or in other words no taper, whereas the second taper <NUM> is greater than zero. As will be understood, the profile of the cooperating box end shown in <FIG> would have a complementary profile, wherein the first taper <NUM> of the box end <NUM> has a taper of zero inches per foot (<NUM> per <NUM>) and the second taper <NUM> is complementary to the second taper <NUM> of the pin end <NUM>. In one aspect, the second taper <NUM> of the pin end <NUM> and the second taper <NUM> of the box end may each have a taper of two inches per foot (<NUM> per <NUM>). It will, however, be appreciated by persons skilled in the art that the second tapers <NUM> and <NUM> may have any value. Similarly, it will be appreciated that the first tapers <NUM> and <NUM> may also have any value.

Referring to <FIG><FIG>, another optional aspect of the description is illustrated, wherein the transitional threads <NUM> and <NUM>, of the box and pin ends, respectively, are stubbed or shortened in height. In the result, and according to this optional aspect, the transitional threads <NUM> and <NUM> are made shorter in height than the remainder of the internal thread <NUM> and external thread <NUM>, respectively. Since it is expected that the transitional threads <NUM> and <NUM> would generally bear the brunt of damage during the stabbing procedure, by stubbing the threads, it is possible to restrict such damage and thereby mitigate damage to internal thread <NUM> and external thread <NUM>.

Another aspect of the multiple tapered threaded connection, generally identified by reference numeral <NUM>, will now be described with reference to <FIG>.

Referring to <FIG>, there is shown a multiple tapered threaded connection <NUM> having a female connection or box end <NUM> and a male connection or pin end <NUM>. Referring to <FIG>, the female connection end <NUM> is provided with an internal thread <NUM>. Referring to <FIG>, the male connection end <NUM> is provided with an external thread <NUM> that is complementary to and adapted to cooperate with the internal thread <NUM> of the female connection end <NUM>. Referring to <FIG>, internal thread <NUM> has a first end <NUM>, a second end <NUM>, a first portion <NUM>, and a second portion <NUM> similar to what was described above. However, in the aspect illustrated in <FIG>, the internal thread <NUM> is provided with a further, third portion <NUM>. As shown, first portion <NUM> is located at first end <NUM> of internal thread <NUM> and has a first taper <NUM>. Second portion <NUM> is located at second end <NUM> of internal thread <NUM> and has a second taper <NUM>. The third portion <NUM> of the internal thread <NUM> is located between the first and second portions <NUM> and <NUM> and is provided with a third taper <NUM>. In this aspect, the taper of each portion is different from that of the immediately adjacent portion. Thus, for example, the first taper <NUM> and second taper <NUM> are different from each other and the second taper <NUM> and third taper <NUM> are different from each other. It will be understood that, in other aspects of the description, the first and second tapers, <NUM> and <NUM> may be the same or different.

In the aspect of the description illustrated in <FIG> and <FIG>, each of first taper <NUM>, second taper <NUM> and third taper <NUM> are different from each other. In the example illustrated, second taper <NUM> is steeper than third taper <NUM>, and third taper <NUM> is steeper than first taper <NUM>. As also shown, first portion <NUM>, second portion <NUM> and third portion <NUM> may be of different lengths. However, it will be understood by persons skilled in the art that first portion <NUM>, second portion <NUM> and third portion <NUM> may be of the same or different lengths. Thus, each of the portions may be of any length irrespective of the others.

Referring again to <FIG>, male connection end <NUM> has external thread <NUM> having a first end <NUM>, a second end <NUM>, a first portion <NUM>, a second portion <NUM> and a third portion <NUM>. First portion <NUM>, second portion <NUM> and third portion <NUM> of male connection end <NUM> correspond, respectively, to first portion <NUM>, second portion <NUM> and third portion <NUM> of female connection end <NUM>, shown in <FIG>. As shown in <FIG>, first portion <NUM> is adjacent first end <NUM> of external thread <NUM> and has a first taper <NUM>, which corresponds to first taper <NUM> of female connection end <NUM>. Second portion <NUM> is adjacent second end <NUM> of external thread <NUM> and has a second taper <NUM> that corresponds to second taper <NUM> of female connection end <NUM>. As shown, third portion <NUM> is positioned between first portion <NUM> and second portion <NUM> and has a third taper <NUM> that corresponds to third taper <NUM> of female connection end <NUM>.

As shown in <FIG> and <FIG>, each of first taper <NUM>, second taper <NUM> and third taper <NUM> are different from each other. In the example illustrated, second taper <NUM> is steeper than third taper <NUM>, and third taper <NUM> is steeper than first taper <NUM>.

In the connection shown in <FIG> which is outside the scope of the claims , the first taper <NUM> and second taper <NUM> are the same, while the third taper <NUM> is different from the first and second tapers <NUM>, <NUM>. In comparing the examples illustrated in <FIG>, it is noted that the first taper <NUM> and second taper <NUM> are each shown to be steeper in <FIG> than in the example shown in <FIG>.

In the examples shown, first portion <NUM>, second portion <NUM> and third portion <NUM> are illustrated as being of different lengths; however, it will be understood by persons skilled in the art that first portion <NUM>, second portion <NUM> and third portion <NUM> may, independently, be of the same or different lengths.

Referring to <FIG>, which illustrates a connection comprising a pin end <NUM> and a box end <NUM>, the first tapers <NUM> and <NUM> create a connection that is relatively thick-walled, thereby allowing for maximizing torque capability in the higher stressed regions of the connection <NUM>. Second tapers <NUM> and <NUM> and third tapers <NUM> and <NUM> have steeper tapers, thereby permitting deep stabbing in the lower stressed regions of the connection <NUM>. As discussed above, this arrangement of tapers allows for a quick make-up and reduces damage without compromising the overall torque carrying capabilities of the connection <NUM>.

It will be appreciated that the provision of the third taper, located between the first and second tapers, further enhances the tailored characteristics of the connection described herein.

In one example, and for illustration purposes only, the first tapers <NUM> and <NUM> may have a taper of <NUM> inches per foot (<NUM> per <NUM>) while the third tapers <NUM> and <NUM> have a steeper taper of <NUM> inches per foot (<NUM> per <NUM>) and the second tapers <NUM> and <NUM> have a further steeper taper of <NUM> inches per foot (<NUM> per <NUM>). The steeper taper of third tapers <NUM> and <NUM> and second tapers <NUM> and <NUM> allows for deeper stabbing of male connection end <NUM> into female connection end <NUM> while the shallower taper of first tapers <NUM> and <NUM> provides a thicker wall for each of male connection end <NUM> and female connection end <NUM>. By providing different tapers, the stress distribution within the connection may be altered or adjusted as needed for a particular application. Thus, by providing different tapers, the stress distribution within the connection may be altered in any desirable fashion.

Referring to <FIG>, it is noted that a transitional thread <NUM> may optionally be provided so as to form a junction between the thread of the first taper <NUM> and the third taper <NUM>, thereby allowing the internal thread <NUM> to be continuous across the first and third portions <NUM> and <NUM>. Similarly, a transitional thread <NUM> may be provided to connect the threads of second taper <NUM> and the third taper <NUM>, so as to allow internal thread <NUM> to remain continuous across the third and second portions <NUM> and <NUM>. Generally, the transitional threads <NUM> and <NUM> may comprise two to four thread rotations; however, it will be understood by persons skilled in the art that more or fewer transitional thread rotations may be provided. The number of transitional thread <NUM> and <NUM> rotations can vary based upon the diameter of the connection, the connection length, and the pitch of the threads.

In a similar manner to above, and referring to <FIG>, a transitional thread <NUM> may be provided to connect the thread of first taper <NUM> with the thread of third taper <NUM> to maintain external thread <NUM> continuous across the first and third portions <NUM> and <NUM>. A transitional thread <NUM> connects the threads of the third taper <NUM> and the second taper <NUM>, thereby allowing external thread <NUM> to be continuous across third and second portions <NUM> and <NUM>. Generally, the transitional threads <NUM> and <NUM> may comprise two to four thread rotations; however, it will be understood by persons skilled in the art that more or fewer transitional thread rotations may be provided. The number of transitional thread <NUM> and <NUM> rotations can vary based upon the diameter of the connection, the connection length, and the pitch of the threads. In the event that more transitional thread rotations are required in one or more locations, the threads of the third portion <NUM> may act as a transitional thread between first portion <NUM> and second portion <NUM> and the threads of third portion <NUM> may act as a transitional thread between first portion <NUM> and second portion <NUM>.

As shown in the example illustrated in <FIG>, the transitional threads <NUM>, <NUM>, <NUM> and <NUM> may be stubbed or shortened. As described above, transitional threads <NUM>, <NUM>, <NUM> and <NUM> would generally bear the brunt of the stabbing damage. Thus, by stubbing the transitional threads, it is possible to restrict damage to the transitional threads <NUM>, <NUM>, <NUM> and <NUM> and to mitigate damage to internal thread <NUM> and external thread <NUM>.

Referring to <FIG>, illustrating the pin end <NUM>, the first portion <NUM>, with first taper <NUM>, and the third portion <NUM>, with third taper <NUM>, of external thread <NUM> may be spaced apart from each other by a first spacer segment 135a. Similarly, the third portion <NUM>, with third taper <NUM>, and second portion <NUM>, with second taper <NUM>, of external thread <NUM> may be spaced apart from each other by a second spacer segment 135b. As shown in <FIG>, the external thread <NUM> is not continuous. The sizes, or lengths, of the spacer segments 135a and 135b may be the same or may vary.

In a similar manner, referring to <FIG>, illustrating the box end <NUM>, the first portion <NUM>, with first taper <NUM>, and third portion <NUM>, with third taper <NUM>, of internal thread <NUM> may be spaced apart from each other by a first spacer segment 137a. Similarly, the third portion <NUM>, with third taper <NUM>, and the second portion <NUM>, with second taper <NUM>, of internal thread <NUM> may be spaced apart from each other by a second spacer segment 137b. Thus, in this way, the internal thread <NUM> is not continuous. The sizes, or lengths, of the spacer segments 137a and 137b may be the same or may vary.

A variation of the multiple tapered threaded connection will now be described with reference to <FIG>. As shown, the multiple tapered threaded connection generally identified by reference numeral <NUM> is formed by connecting a female connection or box end <NUM> and a male connection or pin end <NUM>. Female connection end <NUM> has an internal thread <NUM> and male connection end <NUM> has an external thread <NUM>, which is adapted to cooperate with the internal thread <NUM> of the box end <NUM>. The internal thread <NUM> has a first end <NUM>, a second end <NUM>, a first portion <NUM> and a second portion <NUM>. First portion <NUM> is adjacent first end <NUM> of internal thread <NUM> and has a first taper shown at <NUM>. Second portion <NUM> is adjacent second end <NUM> of internal thread <NUM> and has a second taper shown at <NUM>. In the example shown, first portion <NUM> and second portion <NUM> are of substantially of the same length; however, it will be understood by persons skilled in the art that the first and second portions <NUM>, <NUM> may be different lengths. In the example shown, the second taper <NUM> is steeper than first taper <NUM>.

Referring to <FIG>, male connection end <NUM> has an external thread <NUM> having a first end <NUM>, a second end <NUM>, a first portion <NUM>, a second portion <NUM> and a third portion <NUM>. In the embodiment shown, first portion <NUM> is adjacent first end <NUM> of external threads <NUM> and has a first taper shown at <NUM> corresponding to first taper <NUM> of female connection end <NUM>. Second portion <NUM> is adjacent second end <NUM> of external threads <NUM> and has a second taper shown at <NUM> that corresponds to second taper <NUM> of female connection end <NUM>. Third portion <NUM> is positioned between first portion <NUM> and second portion <NUM> and has a third taper shown at <NUM>. In the example shown, the third taper <NUM> is designed to not cooperate with either the first taper <NUM> or second taper <NUM> of female connection end <NUM>. In the embodiment shown, first portion <NUM> of male connection end <NUM> corresponds to a portion of the first portion <NUM> of female connection end <NUM> and the second portion <NUM> of male connection end <NUM> corresponds to the second portion <NUM> of female connection end <NUM>. As would be understood, the phrase "corresponds to" as used herein is intended to indicate that the respective threads cooperate with each other when the box and pin ends are connected.

The third portion <NUM> of male connection end <NUM> does not cooperate with either the first portion <NUM> or the second portion <NUM> of female connection end <NUM> and there is, therefore, no threaded connection between external thread <NUM> and internal threads <NUM> at the region of the third portion <NUM> of male connection end <NUM>.

It will be understood by persons skilled in the art that any combination of corresponding portions between male connection end <NUM> and female connection end <NUM> may be provided for. In the example shown, each of first taper <NUM>, third taper <NUM> and second taper <NUM> are different from each other, wherein the second taper <NUM> is steeper than third taper <NUM>, and the third taper <NUM> is steeper than first taper <NUM>. As also shown by way of example in <FIG>, the first portion <NUM>, second portion <NUM> and third portion <NUM> may be of different lengths; however, it will be understood by persons skilled in the art that these portions may be of the same or different lengths.

A further variation of the multiple tapered threaded connection, generally identified by reference numeral <NUM>, will now be described with reference to <FIG>.

Referring to <FIG>, a multiple tapered threaded connection <NUM> has a female connection, or box end <NUM>, and a male connection, or pin end <NUM>. Female connection end <NUM> has an internal thread <NUM> and male connection end <NUM> has an external thread <NUM>. Internal thread <NUM> has a first end <NUM>, a second end <NUM>, a first portion <NUM>, a second portion <NUM> and a third portion <NUM>. First portion <NUM> is adjacent first end <NUM> of internal threads <NUM> and has a first taper shown at <NUM>. Second portion <NUM> is adjacent second end <NUM> of internal thread <NUM> and has a second taper shown at <NUM>. Third portion <NUM> is positioned between first portion <NUM> and second portion <NUM> and has a third taper shown at <NUM>. The taper of a given portion is different from the taper of the adjacent portion. Thus, first taper <NUM> and third taper <NUM> are different from each other, and third taper <NUM> and second taper <NUM> are different from each other.

In the example shown in <FIG>, each of first taper <NUM>, third taper <NUM> and second taper <NUM> are different from each other. In this example, second taper <NUM> is steeper than third taper <NUM>, and third taper <NUM> is steeper than first taper <NUM>.

In the example shown in <FIG>, first portion <NUM>, third portion <NUM> and second portion <NUM> are of different lengths; however, it will be understood by persons skilled in the art that these portions may be of the same or different lengths.

As also illustrated in <FIG>, male connection end <NUM> has an external thread <NUM> that has a first end <NUM>, a second end <NUM>, a first portion <NUM> and a second portion <NUM>. First portion <NUM> is adjacent first end <NUM> of external thread <NUM> and has a first taper shown at <NUM>. Second portion <NUM> is adjacent second end <NUM> of external threads <NUM> and has a second taper shown at <NUM>. As shown, the first taper <NUM> of first portion <NUM> of external thread <NUM> generally corresponds to the first taper <NUM> of female connection end <NUM>. Similarly, second taper <NUM> of second portion <NUM> of external thread <NUM> generally corresponds to the second taper <NUM> of female connection end <NUM>. Third taper <NUM> of third portion <NUM> of female connection end <NUM> does not cooperate with either the first taper <NUM> or the second taper <NUM> of male connection end <NUM>. In the example shown, a portion of the first portion <NUM> of male connection end <NUM> cooperates with the first portion <NUM> of female connection end <NUM>, and the second portion <NUM> of male connection end <NUM> cooperates with the second portion <NUM> of female connection end <NUM>. The third portion <NUM> of female connection end <NUM> does not cooperate with either the first portion <NUM> or second portion <NUM> of male connection end <NUM> and there is, therefore, no threaded connection between external thread <NUM> and internal threads <NUM> at the region of the third portion <NUM> of female connection end <NUM>.

It will be understood by persons skilled in the art that any combination of corresponding portions between male connection end <NUM> and female connection end <NUM> may occur. In the examples illustrated, first portion <NUM> and second portion <NUM> are substantially of the same length; however, it will be understood by persons skilled in the art that the first and second portions <NUM> and <NUM> may be of different lengths. In the example shown, second taper <NUM> is steeper than first taper <NUM>; however, this will be understood to be an illustrative embodiment only and not limiting the of scope of the description.

In the present description, the male and/or female connection ends have been described primarily with respect to tubulars or tubular members. However, as mentioned above, a drill string may, in addition to tubular members, also include any number of other components, such as tools, subs etc., as may be needed for a particular application. It will therefore be understood that the connection ends described herein may be provided on any drill string component and not only on tubulars.

Any use herein of any terms describing an interaction between elements is not meant to limit the interaction to direct interaction between the subject elements, and may also include indirect interaction between the elements such as through secondary or intermediary structure unless specifically stated otherwise.

In this patent document, the word "comprising" is used in its non-limiting sense to mean that items following the word are included, but items not specifically mentioned are not excluded. A reference to an element by the indefinite article "a" does not exclude the possibility that more than one of the element is present, unless the context clearly requires that there be one and only one of the elements.

Claim 1:
A pair of drill string connectors (<NUM>, <NUM>) for forming a threaded connection between first and second drill string components, the pair of drill string connectors comprising:
- a first connector (<NUM>) provided on a first end of the first drill string component and a second connector (<NUM>) provided on a first end of the second drill string component, the first connector (<NUM>) being adapted to receive the second connector (<NUM>);
- the first connector (<NUM>) has a first portion (<NUM>) located proximal to the first end of the first drill string component and a second portion (<NUM>) located away from the first end and within the lumen of the first drill string component, the first connector (<NUM>) having at least one internal thread (<NUM>);
- the second connector (<NUM>) has a first portion (<NUM>) located away from the first end of the second drill string component and a second portion (<NUM>) located proximal to the first end of the second drill string component, the second connector (<NUM>) having at least one external thread (<NUM>), wherein the at least one internal thread (<NUM>) is adapted to cooperate with the at least one external thread (<NUM>) to form the threaded connection when the first connector (<NUM>) receives the second connector (<NUM>), wherein, once connected, the first portion of the second connector (<NUM>) is adjacent the first portion of the first connector (<NUM>);
- the first portion (<NUM>) of the first connector (<NUM>) has a first taper (<NUM>) and the first portion (<NUM>) of the second connector (<NUM>) has a corresponding first taper (<NUM>);
- the second portion (<NUM>) of the first connector (<NUM>) has a second taper (<NUM>) different from the first taper (<NUM>) and the second portion (<NUM>) of the second connector (<NUM>) has a corresponding second taper (<NUM>),
- the second taper (<NUM>) of the first connector (<NUM>) is steeper than the first taper (<NUM>) thereof;
- the at least one internal thread (<NUM>) of the first connector (<NUM>) has a first internal thread (<NUM>) provided on the first portion (<NUM>) thereof and a second internal thread (<NUM>) provided on the second portion (<NUM>) thereof; and
- at least one of the drill string components is more particularly a drill string tubular, a drill string tool, and/or a coupling.