Torque and torsion limiting tool

Abstract

A downhole tool (30) particularly for controlling torque and torsion and also for absorbing/dampening vibration in a downhole string is provided and comprises an inner mandrel (1, 7, 11, 15) and an outer mandrel (14, 13, 12, 19) and a coupling mechanism (8) to couple the inner and the outer mandrel, the coupling mechanism comprising one or more longitudinally elongate members (8) acting between the inner and outer mandrel, wherein the one or more longitudinally elongate members are substantially fixed in their longitudinal length but substantially do not resist relative compressive longitudinal movement occurring between the inner and outer mandrels. The coupling mechanism is arranged such that compression of the inner and outer mandrels results in compression of the one or more longitudinally elongate members without necessarily resulting in relative rotation of the inner and outer mandrels.

Claims

1. A downhole tool comprising an inner mandrel: an outer mandrel, and a coupling mechanism to couple the inner and the outer mandrel, the coupling mechanism comprising a plurality of longitudinally elongate members acting between the inner and outer mandrel, wherein the longitudinally elongate members comprise cables having a longitudinal length greater than their diameter; wherein the plurality of cables are arranged around the longitudinal axis of the downhole tool; wherein one end of the plurality of cables is securely mounted to the inner mandrel and the other end of the plurality of cables is securely mounted to the outer mandrel; wherein the plurality of cables are fixed in their longitudinal length when tension is applied to one end relative to another such that the cables resist the tension applied along their length, but wherein said cables permit relative compressive longitudinal movement occurring between the inner and outer mandrels and said cables do not resist relative compressive longitudinal movement occurring between the inner and outer mandrels such that the plurality of cables provide a differential in their reaction to tension and compression; wherein the coupling mechanism permits at least a degree of relative rotational movement between the inner and outer mandrel; the downhole tool further comprising a biasing device acting between the inner and outer mandrel, wherein the biasing device is a separate component from the plurality of cables; and wherein the coupling mechanism is arranged such that compression of the inner and outer mandrels results in the plurality of cables flexibly collapsing, but said compression does not result in relative rotation of the inner and outer mandrels.

2. A downhole tool according to claim 1, wherein compression of the inner and outer mandrels results in telescoping movement of the inner mandrel into the outer mandrel without resulting in relative rotation of the inner and outer mandrels.

3. A downhole tool according to claim 1, wherein the coupling mechanism permits relative rotational movement between the inner and outer mandrels between a first configuration in which the downhole tool is un-torqued and a second configuration in which the downhole tool is fully torqued.

4. A downhole tool according to claim 3, wherein when the tool is in the second configuration the inner mandrel is stroked into the outer mandrel.

5. A downhole tool according to claim 1, wherein the plurality of cables will collapse when compressed at one end relative to the other.

6. A downhole tool according to claim 1, wherein the plurality of cables are inelastic when in tension and do not increase in longitudinal length when tension is applied to one end relative to another.

7. A downhole tool according to claim 1, wherein the downhole tool is adapted to be included in a downhole tool string comprising a downhole drill bit.

8. A downhole tool according to claim 7, wherein the downhole tool is adapted to be included in a downhole tool string further comprising a downhole mud motor.

9. A downhole tool according to claim 1, wherein the plurality of cables are arranged equi-spaced around a co-diameter of the longitudinal axis of the downhole tool.

10. A downhole tool according to claim 1, wherein: the plurality of cables are arranged equi-spaced around a co-diameter of the longitudinal axis of the downhole tool such that the upper ends of the plurality of cables terminate on an upper plane that is perpendicular to the longitudinal axis of the downhole tool and the lower ends of the plurality of cables terminate on a lower plane that is perpendicular to the longitudinal axis of the downhole tool; and wherein the upper and lower planes are spaced apart by a longitudinal distance between the said upper and lower ends; and relative rotation of the said upper ends on their upper plane about the longitudinal axis of the downhole tool with respect to the lower ends on their lower plane results in the plurality of cables comprising a helical configuration having a first longitudinal distance between the upper and lower planes.

11. A downhole tool according to claim 10, wherein further relative rotation of the upper ends on their upper plane about the longitudinal axis of the downhole tool with respect to the lower ends on their lower plane results in the plurality of cables comprising a tighter helical configuration having a second longitudinal distance between the upper and lower planes.

12. A downhole tool according to claim 11, wherein the said second longitudinal distance is shorter than the said first longitudinal distance.

13. A downhole tool according to claim 10, wherein the plurality of cables are arranged such that their pitch is not constant.

14. A downhole tool according to claim 10, wherein the pitch of the plurality of cables increases as the inner mandrel telescopes or strokes further into the outer mandrel.

15. A downhole tool according to claim 1, wherein rotation of the upper end of the plurality of cables relative to the lower end results in the inner mandrel being pulled or stroked into the outer mandrel thereby decreasing the length of the downhole tool and thereby reducing the torque experienced by one or more other components included in the same downhole tool string as the downhole tool.

16. A downhole tool according to claim 1, wherein the downhole tool is a torque restriction tool.

17. A downhole tool according to claim 1, wherein the biasing device acts to bias the inner mandrel out of the outer mandrel and acts to resist relative compressive movement of the inner mandrel into the outer mandrel.

18. A downhole tool according to claim 1, wherein the biasing device comprises one or more spring devices.

19. A downhole tool according to claim 18, wherein the one or more spring devices comprises a plurality of belleville springs.

20. A downhole tool according to claim 1, wherein the biasing device is arranged to enable rotation of the inner mandrel relative to the outer mandrel once a level of relative torque is experienced by the inner and outer mandrel and thus the biasing device permits the said rotation of one end of the plurality of cables relative to the other.

21. A downhole tool according to claim 1, wherein the biasing device is arranged to enable rotation of the inner mandrel relative to the outer mandrel once a pre-determined level of relative torque is experienced by the inner and outer mandrel and thus the biasing device permits the said rotation of one end of the plurality of cables relative to the other.

22. A downhole tool according to claim 1 wherein the downhole tool comprises a downhole torque control tool.

23. A downhole tool according to claim 1 wherein the downhole tool comprises a downhole shock absorber tool.

24. A downhole tool according to claim 1 wherein the downhole tool comprises a downhole axial vibration dampener tool.

25. A downhole tool according to claim 1 wherein the downhole tool comprises a downhole torsion control tool.

26. A downhole tool according to claim 1 wherein the downhole tool comprises a downhole torsional vibration dampener tool.

27. A downhole tool according to claim 1 wherein the downhole tool comprises a combined downhole torque control, torsional control and axial vibration dampener.

28. A downhole tool according to claim 1, wherein the biasing device is arranged to absorb or dampen shock and/or vibration experienced by the downhole tool in use, and therefore provides the tool with a dual shock absorbing and torque control function.

29. A downhole tool according to claim 1, wherein the inner mandrel is arranged telescopingly within the outer mandrel.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

(2) FIG. 1 is a cross sectional side view through a torque control tool in accordance with the present invention, wherein the torque control tool is shown in an at rest configuration where there is no relative torque occurring between an upper end and a lower end of the torque control tool and the torque control tool is fully stroked out and is at its maximum overall length;

(3) FIG. 2 is a cross sectional side view of the torque control tool of FIG. 1 wherein the torque control tool is being shown in FIG. 2 in a fully stroked in configuration resulting from relative torque occurring between the upper and the lower ends of the torque control tool being above a predetermined level (and possibly also a combination of weight being applied on bit) and thus the torque control tool is shown in a full stroked in configuration and is therefore shown at its minimum length;

(4) FIG. 3 is an exploded perspective view of a number of the components particularly the internal components of the lower half of the torque control tool of FIG. 1 and FIG. 2 in order to aid the understanding of the reader in terms of how those components will be arranged when the torque control tool is assembled;

(5) FIG. 4 is a perspective side view of the outer components of the torque control tool when in the configuration as shown in FIG. 1;

(6) FIG. 5 is a perspective side view of the torque control tool of FIG. 4 but with a lower outer sleeve (shown as component 19 in FIG. 4) omitted so that the reader can see the internal components as assembled in situ;

(7) FIG. 6 is a more detailed close up perspective side view of the lower half of the torque control tool of FIG. 5;

(8) FIG. 7 is a perspective side view of the outer components of the torque control tool when in the configuration as shown in FIG. 2;

(9) FIG. 8 is a perspective side view of the torque control tool of FIG. 7 but with the outer sleeve (shown in FIG. 7 as component 19) being omitted so that the reader can see the internal components as assembled in situ, to aid the clarity and understanding of the reader;

(10) FIG. 9 is a closer up and more detailed perspective side view of the lower half of the torque control tool of FIG. 8 showing the internal components in more detail in situ in that configuration.

DETAILED DESCRIPTION OF INVENTION

(11) A torque control tool 30 is shown in FIG. 1 in a relaxed or at rest configuration in which there is minimal or no relative torque occurring between its two ends 22, 24 and therefore there is no or only minimal compression in the longitudinal direction occurring between its two ends 22, 24.

(12) The tool 30 comprises an upper end 22 having a suitable and typically conventional screw threaded connection such as a box connection in accordance with the American Petroleum Institute (API) standard OCTG screw threaded connection for oil field goods and furthermore having at its lower in use end 24 another suitable connection such as a screw threaded pin connection in accordance with the API OCTG screw threaded connections standard to enable the torque control tool 30 to be included in a string of downhole tubulars, typically in the bottom hole assembly (BHA), in relatively close proximity to the drill bit (not shown) which will typically be located below the lowermost end 24 and possibly connected to the lowermost end 24. In use, the torque control tool 30 will typically be located between a drill bit and a downhole mud motor or it can be located above both the drill bit and the downhole motor and as will be described, will act to prevent the mud motor and/or any other drill string or BHA components experiencing levels of torque above a particular predetermined value which may either damage one or both of the mud motor and/or any other drill string or BHA components or prevent either the mud motor or the drill bit from operating to their optimum performance.

(13) The upper box connection 22 at the upper end 22 is formed in a top sub 14 and which is fixed at its lower end to the upper end of a belleville spring housing 13 via suitable connection such as a screw threaded connection and where the lower end of the belleville spring housing 13 is in turn connected via a suitable fixed connection such as a screw threaded connection to the upper end of a top cable anchor 12. The lower end of the top cable anchor 12 is in turn connected via a suitable connection such as screw threaded connection to the upper end of an outer sleeve 19. Thus, the top sub 14, the belleville spring housing 13, the top cable anchor 12 and the outer sleeve 19 form an outer mandrel 14, 13, 12, 19 of the torque control tool 30.

(14) The torque control tool 30 further comprises an inner mandrel 1, 7, 11, 15 which mainly consists of a bottom sub 1 provided at its in use lowermost end (the right hand end as shown in FIG. 1) which is securely connected at its upper end to the lower end of a cable fixation shaft 7 and which in turn is connected at its upper end via suitable screw threaded connections to the lower end of the compression shaft 11 and which in turn is further fixedly connected such as via suitable screw threads provided at its upper end to the lower end in use of a belleville spring shaft 15. In principle therefore and in the absence of any other components, the inner mandrel 1, 7, 11, 15 can telescopically slide in and out of the outer mandrel 14, 13, 12, 19 and thus the length of the torque control tool 30 can be increased or decreased by stroking the inner mandrel out of the outer mandrel (such as shown in FIG. 1) or stroking the inner mandrel in relative to the outer mandrel (such as shown in FIG. 2).

(15) However, the torque control tool 30 further comprises a biasing device in the form of a stack of belleville springs 17 and which are provided in a chamber bounded at an upper end by a spacer 16 and at a lower end by a further spacer 16 in between the belleville spring housing 13 and the belleville spring shaft 15. Therefore, for the torque control tool 30 to move from the stroked out configuration of FIG. 1 to the stroked in configuration of FIG. 2, the belleville spring 17 must be compressed and therefore sufficient force must be applied between the lower end 24 and the upper end 22 in order to compress the belleville spring 17 and that force could be provided for example by letting down weight on bit by the operator at the surface of the wellbore.

(16) In practice though, the amount of force required to compress the belleville spring 17 is relatively high and therefore it is typically the case that the torque control tool 30 will not significantly shorten or be compressed simply by applying weight on bit but even if it is then the torque control 30 will simply stroke out once the weight on bit has been reduced or removed.

(17) Additionally, the torque control tool 30 has the great additional advantage over conventional torque control tools that, in use, it acts to absorb or dampen shocks and/or vibration generated by the drilling process by means of the stack of belleville springs 17 (for example, the belleville springs 17 will dampen or absorb such vibration and/or shocks) and therefore the torque control tool 30 not only acts to control the torque experienced by the BHA (as will be described subsequently) but also acts as a shock and/or vibration absorber (and therefore obviates the need to run a separate/additional shock absorber tool).

(18) Importantly, a set of fixed length and relatively non elastic cables 8 are further provided in the torque control tool 30 wherein the cables 8 are flexible cables in that they may bend about their longitudinal axis but they are relatively non-elastic in terms of their longitudinal length such that they have a relatively fixed longitudinal length and therefore cannot be substantially stretched any more than their relatively fixed longitudinal length. The cables 8 act between the inner and outer mandrel in that their upper end in use are securely locked to the top cable anchor 12 by being retained by suitable connections such as T-slot or a suitable tongue in groove coupling formed on an outer surface of a top cable guide 9 which is further secured to the top cable anchor 12. Furthermore, the lower end of the cables 8 in use are secured by suitable connections such as a T-slot or suitable tongue in groove connections provided on the outer surface of a cable fixation shaft 7 which is securely connected to the bottom sub 1 via a cable fixation sleeve 6 and a set of nuts 5 and counter nuts 4 being screwed on to the lower ends of the cables 8 to further secure them in place. As can most clearly be seen in FIG. 3, the lower inner surface of the top cable guide 9 comprises curved cable guide surfaces 26 and furthermore the upper outer surface of the cable fixation shaft 7 comprises its own cable guide surfaces 28 (which are curved in the opposite direction to the curved cable guide surfaces 26) such that the respective curved cable guide surfaces 26, 28 provide support to the upper and lower respective ends of the cables 8 when the cables 8 are arranged in the helical configuration that they adopt in use of the torque control tool 30 as shown for example in FIG. 5 and in the tighter helix of the configuration shown in FIG. 8.

(19) As can be most easily seen in FIG. 3, the top cable guide 9 is secured to the top cable anchor 12 by a circlip 10. As more clearly seen in FIG. 5, the circlip 10 will act to prevent longitudinal movement of the top cable guide 9 relative to the top cable anchor 12 and longitudinally extending splines 32 extending upwardly from the upper end of the top cable guide 9 and being substantially equi-spaced around the circumference thereof engage with a castellated groove and teeth 34 formation provided around the outer circumference of the top cable anchor 12 to prevent relative rotation from occurring between the top cable guide 9 and the top cable anchor 12. Furthermore, and as shown in FIG. 1 and in FIG. 3, a seal such as an O-ring seal 2 is located in a groove formed on the outer uppermost end of the bottom sub 1 and which acts against the inner through bore at the lower end of the outer sleeve 19 in order to ensure that no downhole fluids can enter into the annular side wall space between the inner and outer mandrels. There is further provided a (lower) radial bearing 3 for the inner surface of the outer sleeve 19 to bear against and therefore rotate against and therefore the lower radial bearing 3 helps prevent wear and tear of the outer sleeve 19 when it moves between the stroked out configuration of FIG. 1 and the stroked in configuration of FIG. 2. The lower radial bearing 3 is mounted and secured on the outer surface of the upper end of the bottom sub 1.

(20) There is a further (top) radial bearing 18 provided between the top cable anchor 12 and the outer surface of the compression shaft 11 and again the top radial bearing 18 assists in preventing wear and tear occurring between the compression shaft 11 and the top cable anchor 12 when the compression shaft 11 and top cable anchor 12 either or both of rotate with respect to one another and telescopically axially move with respect to one another.

(21) The torque control tool 30 during operation will assist in restricting the amount of torque that will be experienced by either or both of the drill bit and/or the mud motor (and any other tools) as will now be described in detail.

(22) The torque control tool 30 in use (assuming that the relative torque occurring between the upper end 22 and the lower end 24 is below a predetermined value) will remain in the stroked out or maximum length configuration shown in FIG. 1 because the axial force generated by the cables 8 trying to shorten the axial length of the torque control tool 30 (i.e. the cables 8 trying to stroke the inner mandrel into the outer mandrel) is not sufficient enough to sufficiently compress the belleville springs 17 much more than that shown in the at rest configuration shown in FIG. 1. However, when the torque relative between the upper end 22 and lower end 24 starts to approach a pre-determined value (which is a safe margin below the maximum torque that can be experienced by the drilling mud motor and/or drill bit or any other tool in the string), the upper end of the cables 8 will continue to be rotated relative to the lower ends of the cables 8 and thus the cables will want to adopt a tighter helix than that shown in FIG. 5. Because the longitudinal length of the cables is fixed, that will then mean that the longitudinal or axial distance between the top cable guide 9 and the cable fixation shaft 7 will start to shorten. Consequently, the inner mandrel will start to be stroked into the outer mandrel and will start to move towards the fully stroked in configuration shown in FIG. 2. However, that telescopic inward stroking of the inner mandrel relative to the outer mandrel means that the belleville springs 17 will start to be compressed and thus the belleville springs 17 will resist the stroking in of the inner mandrel relative to the outer mandrel unless and until sufficient force is applied to them to overcome their biasing action. Thus, the greater the relative torque between the upper 22 and lower 24 ends of the torque control tool 30, the shorter the longitudinal length of the torque control tool 30 becomes and thus that shortening acts to lift the drill bit off the bottom of the wellbore and therefore acts to limit the amount of relative torque experienced by the string. Moreover, the cables 8 will act in use to provide a non-constant pitch, in that a given rotational arc of movement of the upper end 22 (say of 10 degrees) when the tool 30 is toward the fully stroked out configuration (FIG. 1) will produce less of a distance of stroke than the same arc distance (i.e. 10 degrees) when the tool 30 is toward the fully stroked in configuration (FIG. 2)this is because the cables 8 act like a pendulum in a clock in that movement of the pendulum of say 10 degrees off the vertical produces less of a vertical travel than 10 degrees movement of the pendulum when it is already at for example 45 degrees off the vertical.

(23) The torque control tool 30 has a great advantage over other conventional torque limiting or restriction devices in that there is no equivalent friction to overcome that would otherwise be acting between a screw threaded nut and bolt rotation arrangement (i.e. a lead screw arrangement) because in the torque control tool 30, the cables 8 present only minimal or no resistance to longitudinal compression of them. In simple terms, longitudinal compression of the cables 8 simply result in their folding, crumpling, curling or scrunching up or otherwise flexibly collapse and therefore minimal or no energy will be lost if (only) weight on bit is applied to the upper end 22 of the torque control tool 30, the belleville springs 17 of course storing the energy provided by that weight on bit. However, should sufficient torque be experienced by the upper end 22 relative to the lower end 24, the cables 8 will tighten their helix, compressing the belleville spring 17 and therefore shortening the longitudinal length of the torque control tool 30. Furthermore, the belleville spring 17 will act to return the torque control tool 30 from the stroked in configuration of FIG. 2 to the stroked out configuration of FIG. 1 once the relative torque acting between the upper end 22 and the lower end 24 has been reduced or removed and therefore will act to return the drill bit to the face of the wellbore to be cut. Consequently, the cables 8 are adapted to transfer force in one axial direction (i.e. tension) but not in the other (i.e. compression) and so can be thought of as being inelastic in tension but not in compression.

(24) Modifications and improvements may be made to the embodiments hereinbefore described without departing from the scope of the invention. For example, other suitable types of springs or biasing devices could be employed in place of the belleville spring 17. Furthermore, other longitudinal elongate members that are substantially non-elastic could be used instead of the cables 8 and advantageously such other longitudinally elongate members would also be flexible and non-resistive in terms of their lateral (off longitudinal) movement.