Downhole apparatus and associated methods

Abstract

A method and downhole apparatus including a downhole indexer for cyclically varying a configuration or operational mode of a downhole tool according to a predetermined sequence. The apparatus includes tubular body, an indexing member, and a balance piston. The indexing member is selectively moveable relative to the tubular body between a first axial position and a second axial position in response to a signal. The balance piston supports the indexing member at the second position.

Claims

1. A downhole indexing apparatus for cyclically varying a configuration or operational mode of a downhole tool according to a predetermined sequence, the apparatus comprising: a tubular body including a throughbore; an indexing member selectively moveable relative to the tubular body in response to a signal between a first axial position and a second axial position, wherein movement of the indexing member relative to the tubular body is defined by an indexing pin and slot coupling arrangement; an indexing fluid chamber uphole of the indexing member, wherein the indexing fluid chamber is in fluid communication with the throughbore via an indexing chamber port; and wherein the signal for moving the indexing member comprises change in a differential fluid pressure acting across the indexing member; the apparatus further comprising a balance piston for supporting the indexing member at at least one of the axial positions; wherein the indexing member is selectively movable between the first axial position and the second axial position in response to the signal, the second position comprising the supported position, and wherein the balance piston is configured to move from a passive position to an active position to support the indexing member at the second position; wherein the indexing member is biased towards the supported position by a biasing force, and the balance piston is configured to at least partially counteract the biasing force when the indexing member is in the supported position; wherein the balance piston is configured to engage or contact the indexing member at the second position, thereby reducing load on the indexing member and consequently the indexing pin.

2. The apparatus of claim 1, wherein the biasing force provides a preload at the supported position, maintaining the indexing member in the supported position, and wherein the balance piston is configured to reduce the preload at the supported position.

3. The apparatus of claim 1, wherein the biasing force comprises a fluid pressure force component, and the balance piston is configured to at least partially counteract the biasing force's fluid pressure force component.

4. The apparatus of claim 1, wherein the apparatus is configured to expose the balance piston to a similar fluid pressure as the biasing force's fluid pressure, and wherein the apparatus is configured to propel the balance piston towards the active position and the indexing member from the unsupported or first position towards the supported or second position with fluid from a same source.

5. The apparatus of claim 1, wherein the indexing fluid chamber is intermediate the biasing fluid chamber and the balance piston fluid chamber.

6. The apparatus of claim 1, further comprising a coupling arrangement for controlling movement of the indexing member, wherein the coupling arrangement comprises a protrusion and a slot, wherein the protrusion engages the slot.

7. The apparatus of claim 6, wherein the slot is configured to allow the balance piston to support at least at a portion of the biasing force and/or indexing force and/or counterforce at the first and/or second and/or third and/or fourth axial positions.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention will now be described by way of non-limiting example only with reference to the following drawings of which:

(2) FIG. 1 is a schematic illustration of an indexer with an indexing member and a balance piston, with the indexing member in a first position;

(3) FIG. 2 is a schematic illustration of the indexer of FIG. 1 with the indexing member in a second position, with the indexing member and balance piston engaged;

(4) FIG. 3 is a schematic illustration of the indexer of FIG. 1 in a third position;

(5) FIG. 4 is a schematic illustration of the indexer of FIG. 1 in a fourth position; and

(6) FIG. 5 is a schematic view of a portion of the indexing member of FIG. 1.

(7) FIG. 6 is a schematic view of a portion of the balance piston of FIG. 1.

DETAILED DESCRIPTION OF THE DRAWINGS

(8) Referring initially to FIG. 1 there is shown a portion of tool string generally designated 10 comprising an uphole end 12 and a downhole end 14. The tool string 10 includes an indexing apparatus 16 with a tubular body 18 having a throughbore 19, an indexing member 20, and a balance piston 22. It should be understood that references to a particular direction or orientation such as “down”, “up”, “upper”, “lower”, “above”, “below”, “side” and the like used throughout the following description apply to a vertical orientation of the tool string 10 and are not intended to be limiting in any way. For example, the tool string 10 may be utilised in vertical, deviated and/or horizontal wellbores.

(9) In the embodiment shown, the indexing member 20 is in the form of a sleeve, mounted coaxially within the tubular body 18. The indexing member 20 is axially moveable within the tubular body 18, acting as a cycling biasing piston. The apparatus 16 has a compression spring 24 biasing the indexing member 20 uphole. In addition, an annular biasing chamber 26 is defined downhole of the indexing member 20, also biasing the indexing member 20 uphole. The annular biasing chamber 26 is sealed from the throughbore 19, and in fluid communication with an annulus 28 external to the apparatus 16 (such as between the tool string 10 and a casing or bore wall, not shown) via a biasing chamber port 30. Fluid pressure in the biasing chamber 26 corresponds generally to the annular fluid pressure and acts on a lowermost effective area of the indexing member 16 to force the indexing member 16 uphole.

(10) Uphole of the indexing member 20 is an indexing fluid chamber 32. The indexing fluid chamber 32 acts on an uppermost effective area of the indexing member 16 to force the indexing member 16 downhole. The indexing fluid chamber 32 is in fluid communication with the throughbore 19 via an indexing chamber port 34; and sealed from the annulus 28 and the biasing fluid chamber 26. In the embodiment shown, the uppermost and lowermost effective areas of the indexing member 16 are similar, such that when throughbore and annular fluid pressure are similar, the net resultant force on the indexing member 16 is the mechanical uphole biasing force of the compression spring 24. However, in the configuration shown in FIG. 1, the throughbore pressure is substantially greater than the annular pressure. Accordingly, the downhole biasing force generated in the indexing fluid chamber 32 is substantially greater than the uphole biasing force of the combination of the mechanical spring 24 and the biasing fluid chamber 26. Accordingly, the apparatus is shown in FIG. 1 with the indexing member 20 in a first axial position, which is a lowermost axial position in the embodiment shown.

(11) The movement of the indexing member 20 relative to the tubular body 18 is defined by a guide pin 36 and slot 38 coupling arrangement. The guide pins 36 are mounted to project radially internally from the tubular body 18; and the slot 38 is formed as a radially inwardly extending recess in the indexing member 20, extending around the circumference of the indexing member 20 as a continuous recess.

(12) In the configuration shown in FIG. 1, the net downhole biasing force (resultant from the greater downhole indexing fluid chamber biasing force compared to the uphole spring and biasing chamber fluid force) propels the indexing member 20 to a lowermost position defined by the pin 36 and slot 38 arrangement. In the embodiment shown, when the indexing member 20 reaches the first position of FIG. 1, the indexing member is supported on a lower stop 40, formed as a shoulder on an inner mandrel 42 that defines the biasing chamber 26 inside the tubular body 18. The lower stop ensures that once the indexing member 20 reaches the first position if FIG. 1, a portion of the downhole net biasing force is diverted from the pin 36 and 38 slot coupling arrangement. Accordingly, higher forces, such as due to increased throughbore pressures, may be permissible, without overloading the coupling arrangement.

(13) The balance piston 22 is shown in an inactive or passive position in FIG. 1. The balance piston 22 is biased uphole by fluid pressure in the indexing chamber 32, which exceeds annular pressure in the configuration shown in FIG. 1. Accordingly the downhole balance piston biasing force generated in a balance piston chamber 48 is less than the uphole balance piston biasing force generated in the indexing chamber 32, which is in fluid communication with the annulus 28 via a balance piston chamber port 50. The balance piston 22 is pressed uphole to the passive position, where it is supported by an upper stop 52.

(14) In the embodiment shown, the indexing member 20 comprises an indexing port 44 (partially shown in FIG. 1) for selectively communicating with a port or valve 46 in the tubular body 18. The first position of FIG. 1 corresponds to a valve closed position. In FIG. 1, the body port 46 is actively maintained closed by an internal bore pressure, such as provided from above (e. g. by a pump).

(15) When it is desired to reconfigure the apparatus 16, a signal is transmitted in the form of a decrease in fluid pressure in the throughbore 19. For example, fluid pressure generated by pumping fluid from surface may be decreased, such as by decreasing pumping rate or pressure. Accordingly, fluid pressure in the indexing chamber 32, in fluid communication with the throughbore 19 via the indexing chamber port 34, decreases. When the downhole biasing force acting on the indexing member 20 generated in the indexing chamber 32 falls below the combined mechanical and biasing fluid chamber uphole biasing force acting on the indexing member 20, the indexing member is propelled from the first position of FIG. 1 to the supported or second position of FIG. 2.

(16) When the uphole biasing force acting on the balance piston 22 generated in the indexing chamber 32 falls below the downhole biasing force acting on the balance piston generated in the balance piston chamber 48, which is in fluid communication with the annulus 28 via the balance piston port 50, the balance piston is propelled downhole towards the indexing member. When the indexing member 20 reaches the end of its uphole cycle travel as defined by the guide pin 36 and slot 38 coupling arrangement, the indexing member 20 is engaged by the balance piston 22. The balance piston 22 exerts a downhole force on the indexing member 20. The effective area of the balance piston 22 acting downhole is similar to the effective area in the biasing fluid chamber acting uphole (and also to the effective downhole and uphole areas of the indexing fluid chamber). Accordingly, the balance piston 22 substantially counter-acts or balances the entire fluid-generated uphole force component acting on the indexing member 20. Accordingly, the indexing member 20 is effectively biased against the guide pins 36 in the second position only by the compression spring 24. Accordingly, the apparatus 16 may be suitable for higher fluid pressures and fluid pressure differentials than may otherwise be possible. For example, the throughbore pressure may be negligible, such as when the toolstring 10 is run-in, such that the apparatus 16 may be safely exposed in the second position to a substantially greater annular than throughbore pressure.

(17) In other embodiments it will be appreciated that the indexing member may be additionally or alternatively biased by a motor/s and/or a hydraulic ram/s, or the like.

(18) The balance piston 22 effectively functions as an intermediate stop supporting the indexing member 20 in the second position of FIG. 2.

(19) In the embodiment shown, the second position of FIG. 2 corresponds to a similar operational state as the first position. That is, the second position corresponds to a valve closed position. In FIG. 2, the body port 46 is passively maintained closed by the biasing, such as provided from the spring 24 and biasing fluid chamber 26 pressurised by the annular 28 fluid pressure. However, it will readily be appreciated that in alternative embodiments, the second position may correspond to a different operational state (e. g. a valve open position).

(20) When it is desired to reconfigure the apparatus 16 again, fluid pressure in the throughbore 19 is increased. For example, fluid pressure generated by pumping fluid from surface may be increased, such as by increasing pumping rate or pressure. Accordingly, fluid pressure in the indexing chamber 32, in fluid communication with the throughbore 19 via the indexing chamber port 34, increases. When the downhole biasing force acting on the indexing member 20 generated in the indexing chamber 32 rises above the combined mechanical and biasing fluid chamber uphole biasing force acting on the indexing member 20, the indexing member is propelled from the second position of FIG. 2 to the third position of FIG. 3.

(21) When the uphole biasing force acting on the balance piston 22 generated in the indexing chamber 32 rises above the downhole biasing force acting on the balance piston generated in the balance piston chamber 48, which is in fluid communication with the annulus 28 via the balance piston port 50, the balance piston is propelled uphole towards the stop 52.

(22) When the indexing member 20 reaches the end of its downhole cycle travel as defined by the guide pin 36 and slot 38 coupling arrangement, the indexing member 20 reaches the first position of FIG. 1, the indexing member is supported on a lower stop 40, formed as a shoulder on an inner mandrel 42 that defines the biasing chamber 26 inside the tubular body 18. The lower stop ensures that once the indexing member 20 reaches the first position if FIG. 1, a portion of the downhole net biasing force is diverted from the pin 36 and 38 slot coupling arrangement. Accordingly, higher forces, such as due to increased throughbore pressures, may be permissible, without overloading the coupling arrangement.

(23) In the embodiment shown, the third position of FIG. 3 corresponds to a similar axial position and operational state as the first position. That is, the third position corresponds to a valve closed position. In FIG. 3, the body port 46 is actively maintained closed by an internal bore pressure, such as provided from above (e. g. by a pump). However, it will readily be appreciated that in alternative embodiments, the third position may correspond to a different axial position (e. g. a second intermediate axial position) and/or a different operational state (e. g. a valve open position).

(24) When it is desired to reconfigure the apparatus 16, such as to cycle the apparatus 16 to a valve open position, fluid pressure in the throughbore 19 is decreased. For example, fluid pressure generated by pumping fluid from surface may be decreased, such as by decreasing pumping rate or pressure. Accordingly, fluid pressure in the indexing chamber 32, in fluid communication with the throughbore 19 via the indexing chamber port 34, decreases. When the downhole biasing force acting on the indexing member 20 generated in the indexing chamber 32 falls below the combined mechanical and biasing fluid chamber uphole biasing force acting on the indexing member 20, the indexing member is propelled from the third position of FIG. 3 (corresponding to the first axial position of FIG. 1) to the fourth position of FIG. 4.

(25) When the indexing member 20 reaches the end of its uphole cycle travel as defined by the guide pin 36 and slot 38 coupling arrangement, the indexing member 20 engages the balance piston 22. The balance piston 22 exerts a downhole force on the indexing member 20. The effective area of the balance piston 22 acting downhole is similar to the effective area in the biasing fluid chamber acting uphole (and also to the effective downhole and uphole areas of the indexing fluid chamber). The balance piston 22 substantially counter-acts or balances the entire fluid-generated uphole force component acting on the indexing member 20; although the indexing member 20 is effectively biased against the guide pins 36 in the fourth position by the mechanical spring 24. Furthermore, the indexing member 20 is supported by the stop 52 via the balance piston 22.

(26) In the embodiment shown, the fourth position of FIG. 4 corresponds to a different operational state as the first position. That is, the fourth position (third different axial position) corresponds to a valve open position. The body port 46 and indexing port 44 are rotationally and axially aligned. However, it will readily be appreciated that in alternative embodiments, the fourth position (third different axial position) position may correspond to a different operational state (e. g. a valve closed position).

(27) It will readily be appreciated that the apparatus 16 may be endlessly cycled or indexed between the configurations of FIGS. 1 to 4, sequentially. That is the apparatus 16 can be reconfigured from that of FIG. 4 to FIG. 1, such as by decreasing pressure in the indexing fluid chamber 32.

(28) Reference is now made to FIG. 5, which shows the relative movement of the guide pin 36 in the slot 38 between respective positions; although in the embodiment shown it will be appreciated that the guide pin 36 remains substantially static and the indexing member 20 with slot 38 moves relative to the guide pin 36 (i. e. the indexing member 20 rotates and translates relative to the tubular body 18 along the path 80 shown relative to the guide pin 36). In the embodiment shown, the slot 38 extends continuously around a circumference of the indexing member 20. The profile of the slot 38 defines a cyclical sequence corresponding to the axial positions of FIGS. 1 to 4. The cyclical sequence has three axial indexing positions within each cycle, wherein each indexing position corresponds to an operational state or configuration.

(29) In use, the indexing member is used to control the operational state or configuration of downhole apparatus. The slot 38 defines a series of peaks 51, 53, 54, 56, 58, 60. In the embodiment shown, all of the peaks correspond to a similar axial position (lowermost) of the indexing member 20 relative to the tubular body 18. However, it will readily be appreciated that variations in peak axial positions may be comprised within other embodiments.

(30) Circumferentially positioned between each peak 51, 53, 54, 56, 58, 60 is a trough 62, 64, 66, 68, 70. In the embodiment shown, the troughs comprise shallow troughs 62, 66, 68, 70 and deep troughs 64. The troughs 62, 66, 68, 70 form a stop which support at least a portion of the biasing force and/or indexing force and/or counterforce at the respective first and/or second and/or third and/or fourth axial positions.

(31) It will be appreciated that the pattern of peaks 51, 53, 54, 56, 58, 60 and troughs 62, 64, 66, 68, 70 is repeated circumferentially in the slot 38 corresponding to each guide pin 36. The relative path 80 of a guide pin 36 in the slot 38 is depicted by broken line. When the net axial biasing force acting on the indexing member 20 changes from downhole to uphole, the indexing member 20 moves axially and rotationally relative to the tubular member as defined by the path 80 from the first position 82 corresponding to FIG. 1 with the guide pin 36 in a first peak 51 to the second position 84 corresponding to FIG. 2 with the guide pin 36 in a first shallow trough 62. The balance piston 22 ensures that the guide pin 36 is not overloaded as the balance piston 22 supports the indexing member 20 at the second position 84 of FIG. 2.

(32) Subsequently, when the net axial biasing force acting on the indexing member 20 changes from uphole to downhole, the indexing member 20 moves axially and rotationally relative to the tubular member as defined by the path 80 from the second position 84 corresponding to FIG. 2 with the guide pin 36 in a first shallow trough 62 to the third position 86 corresponding to FIG. 3 with the guide pin 36 in a second peak 53.

(33) When the net axial biasing force acting on the indexing member 20 changes from downhole to uphole, the indexing member 20 moves axially and rotationally relative to the tubular member as defined by the path 80 from the third position 86 corresponding to FIG. 3 with the guide pin 36 in the second peak 53 to the fourth position 88 corresponding to FIG. 4 with the guide pin 36 in a first deep trough 64.

(34) Subsequently, the net axial biasing force acting on the indexing member 20 may be changed from uphole to downhole, such that the indexing member 20 moves axially and rotationally relative to the tubular member as defined by the path 80 from the fourth position 88 corresponding to FIG. 4 with the guide pin 36 in the first deep trough 64 to a fifth position 90 corresponding to the axial position of FIG. 1 with the guide pin 36 in the third peak 54.

(35) Accordingly, the indexing member 20 may be continuously endlessly cycled between rotational and axial positions relative to the tubular body 18.

(36) One skilled in the art will appreciate that various modifications of the apparatus 16 are possible. For example, the coupling arrangement may differ from the indexing pin and slot arrangements described above. For example, the coupling arrangement may comprise a pair of inter-engaging members such as a pair of inter-engaging clutch members or a cam member and a cam follower member, wherein one or both of the inter-engaging members are configured so as to define sequential indexing positions within a cycle, each indexing position corresponding to an operational state or configuration.

(37) Similarly in alternative embodiments, rather than being endlessly cycled in a clockwise or counter-clockwise direction, the indexing member may be endlessly cycled by repeatedly reversing the direction of rotation.

(38) In the embodiment shown, the indexing member is subjected to downhole or annular pressure (via a chamber comprising the spring) from a radial port. However, it will be appreciated that in other embodiments, the actuation member may be subjected to a downhole or annular pressure from an axial port or throughbore. For example, the downhole tool may be at least selectively open at a downhole end.

(39) In alternative embodiments the indexing member may be indexed between positions using one or more motor/s, such as hydraulic or electric motor/s, in addition or as an alternative to the fluid pressure propulsion or biasing of the embodiment shown. The provision of the balance piston may enable the use of a smaller motor/s or fewer motors than may otherwise be required to overcome a differential pressure acting on the indexing member.

(40) The applicant hereby discloses in isolation each individual feature described herein and any combination of two or more such features, to the extent that such features or combinations are capable of being carried out based on the present specification as a whole in the light of the common general knowledge of a person skilled in the art, irrespective of whether such features or combinations of features solve any problems disclosed herein, and without limitation to the scope of the claims. The applicant indicates that aspects of the present invention may consist of any such individual feature or combination of features. It should be understood that the embodiments described herein are merely exemplary and that various modifications may be made thereto without departing from the scope of the invention.

(41) For example, it will be appreciated that the indexing member may be cycled or indexed without substantially varying the cycling or indexing force or pressure. For example, the indexing force or indexing chamber pressure may be defined or linked to a substantially constant force or pressure, such as an annular fluid pressure or a constant bore pressure or a resilient member. The indexing member may be cycled or indexed by varying the biasing force and/or balance piston force.

(42) It will be appreciated that the balance piston may act as a safety mechanism, such as in the event that the apparatus is inadvertently indexed or cycled. For example, where an unplanned or sudden change in fluid pressure occurs, such as due to a pump failure or shut-off, the balance piston ensures that the coupling arrangement is not subjected to an overload due to a substantially relatively high downhole or annular pressure.

(43) It will be appreciated that where the balance piston shown here is uphole of the indexing member, in other embodiments, the balance piston may be located downhole of the indexing member. Similarly, where shown here as a single balance piston at least partially counteracting the biasing piston, in other embodiments an additional or alternative balance piston may at least partially counteract the indexing member. For example, the balance piston may be configured to counteract a force in an indexing chamber, such as an internal bore fluid. Such a balance piston may provide an alternative or additional biasing force, such that lower forces are transmitted to the coupling arrangement, such as at an alternative or a second intermediate position corresponding to the position of FIG. 3 (e. g. where FIG. 3 is replaced with an intermediate position, with the indexing member biased downhole, rather than an end axial position).