Pressure Operated Valve Assembly

Abstract

A valve assembly comprises an actuation fluid inlet, an actuation fluid outlet and a valve member moveable between a closed position in which the actuation fluid outlet is closed, and an open position in which the actuation fluid outlet is opened. A locking arrangement is provided for locking the valve member in its closed position, wherein the locking arrangement is operable in response to a first predetermined fluid pressure event associated with at least the actuation fluid inlet to release the locking arrangement to permit the valve member to be moved to its open position in response to a second subsequent predetermined fluid pressure event associated with at least the actuation fluid inlet.

Claims

1. A downhole pressure operated valve assembly, comprising: an actuation fluid inlet for receiving an actuation fluid from a source; an actuation fluid outlet for delivering the actuation fluid to a target; a valve member moveable between a closed position in which the actuation fluid outlet is closed, and an open position in which the actuation fluid outlet is opened; a locking arrangement for locking the valve member in its closed position; and a release member operable in response to a first predetermined fluid pressure event associated with at least the actuation fluid inlet to release the locking arrangement to permit the valve member to be moved to its open position in response to a second predetermined fluid pressure event associated with at least the actuation fluid inlet.

2. The downhole pressure operated valve assembly according to claim 1, wherein the release member is operable to be moved in response to the first pressure event from a locking position in which the locking arrangement is held locked to a release position in which the locking arrangement is released.

3. The downhole pressure operated valve assembly according to claim 2, wherein the release member is operable to be moved in response to the first pressure event from the locking position to an intermediate position prior to being moved to the release position, and wherein the release member is operable to retain the locking arrangement in a locked configuration when said release member is located in its intermediate position.

4-5. (canceled)

6. The downhole pressure operated valve assembly according to claim 3, wherein the release member is operable to move from the locking position to the intermediate position in response to a period of increasing or increased pressure, and subsequently moved from the intermediate position to the release position in response to a period of decreasing or decreased pressure.

7. The downhole pressure operated valve assembly according to any preceding claim, wherein the release member is defined by an axial piston member or structure, wherein at least one portion of the release member is in pressure communication with the fluid inlet, and wherein at least one portion of the release member is in pressure communication with a remote location such that movement of the release member is associated with a pressure differential applied between the fluid inlet and the remote location.

8. (canceled)

9. The downhole pressure operated valve assembly according to claim 3, wherein the release member is moveable in a first direction from its locking position to the intermediate position, and moveable in a second direction from its intermediate position to its release position.

10. The downhole pressure operated valve assembly according to claim 3, wherein the release member is moveable over a first distance between the locking position and the intermediate position, and moveable over a second distance between the intermediate position and the release position, wherein the second distance is larger than the first distance.

11. (canceled)

12. The downhole pressure operated valve assembly according to claim 1, wherein the locking arrangement extends laterally between the valve member and the release member.

13. The downhole pressure operated valve assembly according to claim 1, wherein the locking arrangement comprises at least one locking member which extends between the valve member and the release member.

14. The downhole pressure operated valve assembly according to claim 1, wherein the locking arrangement engages a locking profile provided on the valve member to lock the valve member in its closed position.

15. The downhole pressure operated valve assembly according to claim 14, wherein the release member defines a locking surface, wherein when the locking arrangement is aligned with the locking surface the locking arrangement is held in engagement with the locking profile of the release member.

16. The downhole pressure operated valve assembly according to claim 13, wherein the release member defines a release surface, wherein when the release member is moved during the first pressure event the release surface becomes aligned with the locking arrangement, to permit movement of the locking member from the locking profile of the valve member.

17. The downhole pressure operated valve assembly according to claim 1, wherein the locking arrangement comprises a plurality of stacked locking members extending between the release member and valve member.

18-20. (canceled)

21. The downhole pressure operated valve assembly according to claim 1, wherein the valve member comprises an axial piston, wherein at least one portion of the valve member is in pressure communication with the fluid inlet, and wherein at least one portion of the valve member is in pressure communication with a remote location such that movement of the valve member is associated with a pressure differential applied between the fluid inlet and the remote location.

22-23. (canceled)

24. The downhole pressure operated valve assembly according to claim 1, wherein the valve member is operable to be moved in response to the second pressure event from its closed position to an intermediate position, prior to being moved to its open position, wherein the fluid outlet remains closed by the valve member when said valve member is located in its intermediate position.

25-26. (canceled)

27. The downhole pressure operated valve assembly according to claim 24, wherein the valve member is operable to move from the closed position to the intermediate position in response to a period of increasing or increased pressure, and subsequently moved from the intermediate position to the open position in response to a period of decreasing or decreased pressure.

28. The downhole pressure operated valve assembly according to claim 24, wherein the valve member is moveable in a first direction from its closed position to the intermediate position, and moveable in a second direction from its intermediate position to its open position.

29. The downhole pressure operated valve assembly according to claim 24, wherein the valve member is moveable over a first distance between the closed position and the intermediate position, and moveable over a second distance between the intermediate position and the open position, wherein the second distance is larger than the first distance.

30-31. (canceled)

32. The downhole pressure operated valve assembly according to claim 1, comprising a flow path extending between the actuation fluid inlet and outlet, wherein the locking arrangement is at least partially located with this flow path.

33. (canceled)

34. The downhole pressure operated valve assembly according to claim 1, comprising a pressure transfer arrangement for facilitating transfer of pressure within a region of a wellbore and a source of actuation fluid.

35. The downhole pressure operated valve assembly according to any preceding claim 1, comprising a biasing arrangement for biasing the release member in one direction. 36-40. (canceled)

41. The downhole pressure operated valve assembly according to claim 1, comprising a biasing arrangement for biasing the valve member in one direction, wherein the biasing arrangement comprises a fluid biasing arrangement and opposing sides of the valve member are exposed to a fluid biasing arrangement.

42. (canceled)

43. The downhole pressure operated valve assembly according to claim 41, wherein a first side of the valve member defines a first sealing area and a second side of the valve member may defines a second sealing area, wherein the first and second sealing areas are exposed to the fluid biasing arrangement.

44. The downhole pressure operated valve assembly according to claim 43, wherein the first and second sealing areas are different such that a bias effect in one direction is achieved from the common fluid biasing arrangement.

45. The downhole pressure operated valve assembly according to claim 44, wherein an intermediate region between the first and second sealing areas is in pressure communication with the fluid inlet of the valve assembly.

46. (canceled)

47. A method for downhole actuation, comprising: providing a valve member of a pressure operated valve assembly in a closed position in which an actuation fluid outlet is closed to prevent actuation fluid from reaching a target location; locking the valve member in its closed position by use of a locking arrangement and a release member; communicating fluid hum a fluid source to an actuation fluid inlet of the pressure operated valve assembly; establishing a first predetermined pressure event associated with at least the actuation fluid inlet to operate the release member to unlock the valve member; and establishing a second predetermined pressure event associated with at least the actuation fluid inlet to operate the valve member to move to an open position and permit actuation fluid to flow from the fluid source to the target location.

48. The method according to claim 47, wherein at least one pressure event is achieved by pressure directly applied at the fluid inlet.

49. The method according to claim 47, wherein at least one pressure event is achieved by application of a pressure differential with reference to the pressure at the fluid inlet.

50. The method according to claim 47, wherein the first and second pressure events are sequential.

51. The method according to claim 47, wherein at least one of the first and second pressure events comprises a pressure variation.

52. The method according to claim 47, wherein at least a portion of the second pressure event may be defined during the first pressure event.

53. A downhole actuation system, comprising first and second valve assemblies each comprising: an actuation fluid inlet; an actuation fluid outlet; a valve member moveable between a closed position in which the actuation fluid outlet is closed, and an open position in which the actuation fluid outlet is opened; a locking arrangement for locking the valve member in its closed position; and a release member operable in response to a first predetermined fluid pressure event associated with at least the actuation fluid inlet to release the locking arrangement to permit the valve member to be moved to its open position in response to a second subsequent predetermined fluid pressure event associated with at least the actuation fluid inlet, wherein: the actuation fluid inlet of the first valve assembly is in communication with an actuation fluid source; the actuation fluid outlet of the first valve assembly is in communication with the actuation fluid inlet of the second valve assembly; and the actuation fluid outlet of the second valve assembly is in fluid communication with a target.

54. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0127] These and other aspects of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0128] FIG. 1A is a diagrammatic illustration of a completion system which includes a pressure operated valve assembly according to an embodiment of the present invention, wherein the completion system includes an ICD in a closed configuration;

[0129] FIG. 1B is an enlarged view of the region B in FIG. 1A;

[0130] FIGS. 2A to 2D are diagrammatic sequential illustrations of the use of a pressure operated valve assembly in accordance with an embodiment of the present invention.

[0131] FIG. 3 illustrates the ICD of FIG. 1A in an open position;

[0132] FIGS. 4A and 4B are sequential diagrammatic illustrations of a downhole actuation system in accordance with an embodiment of the present invention; and

[0133] FIGS. 5A to 5E are sequential diagrammatic illustrations of the use of a pressure operated valve assembly in accordance with an alternative embodiment of the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

[0134] There are limitations with Composite resins, both with temperature and triaxial loading. Industry is directing the use of composites in higher temperature applications, in addition to requiring higher load capabilities. Current technology cannot meet these requirements. Historically composite technology has advanced by higher temperature resins reinforced with carbon and glass fibers at a macro level. This is industry standard.

[0135] FIG. 1 is a diagrammatic illustration of a completion system, generally identified by reference numeral 10, in accordance with an embodiment of the present invention. The completion system 10 includes threaded connectors 12, 14 at opposing ends thereof to facilitate securing in-line with a completion string (not shown).

[0136] The completion system 10 includes a pressure operated valve assembly, generally identified by reference numeral 16, and a downhole tool 18 which is to be actuated by the valve assembly 16. In the present illustrated embodiment the downhole tool is an ICD, although any other fluid actuated tool or system may be used.

[0137] An enlarged view of the completion system 10 in the region B of FIG. 1A is provided in FIG. 1B, reference to which is now made. The valve assembly 16 includes a valve housing 20 located within a pocket 22 formed in a wall 24 of the completion system 10.

[0138] A reservoir of actuation fluid 26 is provided within an annular space 28 within the wall 24 of the completion system 10, wherein the actuation fluid 26 is in communication with the valve housing 22 via an actuation fluid inlet 30, with the communication path illustrated by broken line 32.

[0139] A pressure transfer arrangement in the form of an annular piston 34 is positioned within the annular space 28, sealed against the inner and outer walls of the annular space 28 by respective inner and outer seals 36, 38. The annular piston 34 is arranged such that one side thereof is in communication with the actuation fluid 26, and an opposing side is in communication with fluid within the bore 40 of the completion system 10 via ports 42. Accordingly, the pressure of the actuation fluid 26, and thus the pressure acting at the fluid inlet 30 of the valve housing 20, may be substantially equalised with the internal pressure of the completion system 10. The provision of the annular piston 34 provides the ability to impart the completion pressure into the actuation fluid 26, while minimising the risk of fluid contamination, which may otherwise compromise the valve assembly 16.

[0140] The valve housing 20 includes or defines an actuation fluid outlet 44 which is in fluid communication with the ICD 18 via flow path 46. As will be described in more detail below, the valve assembly 16 functions to selectively deliver the actuation fluid 26 to the ICD 18 via the flow path 46 to facilitate operation or actuation of the ICD 18.

[0141] An elastic tube 47, such as may be formed from Viton, is in fluid communication with a reference port 49 of the valve housing 20, wherein the elastic tube 47 is coiled or laid in a serpentine form within the pocket 22. In the embodiment shown the tube 47 is filled with a compressible fluid 51, such as Silicon oil. The pocket 22 is in communication with the space 55 external of the completion system 10 (which may be an annulus space) via a port 53, such that external pressure may act on the outer surface of the tube 47, and thus impart this pressure to the compressible fluid 51. As will be described in more detail below, the elastic tube 47 and compressible fluid 51 function as a biasing arrangement within the valve assembly 16.

[0142] The ICD 18 includes a housing 48 which includes a number of circumferentially arranged ports 50. An outer shroud 52 surrounds the ports 50, wherein the shroud 52 defines an annular flow path 54 with the housing 48. A screen material 56 (see FIG. 1A) closes an end of the annular flow-path 54 such that inflow from the space 55 surrounding the completion system (the wellbore annulus) is permitted through the screen material 56, which functions as a filter.

[0143] The ICD 18 further includes a sleeve 60 mounted internally of the housing 48, wherein the sleeve 60 includes a plurality of circumferentially arranged ports 62. In the configuration shown in FIG. 1B the sleeve 60 is in a closed position, such that the ports 62 of the sleeve 60 are misaligned from the ports 50 in the housing 48, preventing inflow. A number of O-ring seals 64, 66, 68 are axially placed along the outer surface of the sleeve 60, and when in the closed position seals 64 and 66 straddle the ports 50 to provide sealing of said ports 50. The sleeve 60 is held within this closed position by a beveled-edge snap ring 70 secured to the sleeve 60 and received within an annular recess 72 formed in the inner surface of the housing 48.

[0144] A first chamber 74 is defined between the sleeve 60 and the housing 48, wherein said first chamber 74 is provided at atmospheric pressure. O-ring seal 68 cooperates with a further seal 76 to isolate the first chamber 74.

[0145] A second chamber 78 is defined between the sleeve 60 and the housing 48 (and other wall sections of the completion system 10). The second chamber 78 is isolated via the seal 76 and a further seal 80. The flow path 46 from the fluid outlet 44 of the valve housing 20 is in communication with the second chamber 78.

[0146] As will be described in more detail below, in use, fluid pressure within the bore 40 of the completion system 10 may be varied to eventually establish communication of the actuation fluid 26, through the valve housing 20, along the flow-path 46 and into the second chamber 78. When the pressure force is sufficient the snap ring 70 will be disengaged to allow the sleeve 60 to move to open the ports 50 in the housing.

[0147] FIG. 2A is a diagrammatic cross-sectional illustration of the valve housing 20 of the valve assembly 16 of FIG. 1B. The valve assembly includes a valve member 82 in the form of an axially moveable piston mounted within a first stepped bore 83 within the housing 20. The valve member 82 is shown in FIG. 2A in a position in which the fluid outlet 44 is closed. Specifically, the valve member 82 carries a pair of O-rings 84, 85 which, when the valve member 82 is in the configuration of FIG. 2A, engage the housing 20 and straddle and seal a port 44a, which port 44a is in fluid communication with the outlet port 44 via drilled bores 44b, 44c.

[0148] The valve member 82 is shown in FIG. 2A initially secured to a fixture sleeve 85 via shear pins 86, wherein the fixture sleeve 85 is rigidly secured to the housing 20 via a connecting pin 88. The fixture sleeve 85 provides advantages in terms of manufacture. However, in other embodiments the valve member 82 may be directly secured to the housing 20 via shear pins.

[0149] The valve assembly 16 further includes a release member 90 in the form of an axially moveable piston which is located within a second stepped bore 91, wherein the release member 90 is shown in FIG. 2A initially secured to a fixture sleeve 92 via shear pins 94, wherein the fixture sleeve 92 is rigidly fixed to the housing 20. This initial position of the release member 90 may be defined as a locking position.

[0150] The release member 90 includes a large diameter region 96 which merges, via a ramped step 98, with a reduced diameter region 100. An O-ring seal 102 is provided on the reduced diameter region 100 and establishes a seal between the release member 90 and the housing 20.

[0151] One side of the release member 90 is in fluid communication with the fluid inlet 30, wherein the actuation fluid 26 (FIG. 1B) provided via the fluid inlet 30 acts against the release member 90 over the area defined by the O-ring seal 102.

[0152] The valve assembly 16 includes a locking arrangement 104 in the form of a plurality of stacked balls 106 which are located in a drilled bore 108 extending between the respective bores 83, 91, wherein the drilled bore 108 also provides fluid communication between said bores 83, 91. The uppermost ball 106a (relative to the orientation of the Figure) is located within a locking recess 110 formed in the valve member 82, whereas the lowermost ball 106b (relative to the orientation of the Figure) is engaged by the large diameter region 96 of the release member 90. Thus, in the arrangement shown in FIG. 2A the locking arrangement 104 functions to lock the valve member 82 in the illustrated closed position.

[0153] Both the valve member 82 and the release member 90 are in fluid communication with the elastic tube 47 and the compressible fluid 51 via the reference port 49. In particular a first reference chamber 112 is defined by the valve member 82 and the first bore 83, wherein the first reference chamber 112 is in communication with the reference port 49. The O-ring 85 isolates the first reference chamber 112 from the outlet port 44, such that fluid pressure acting at the reference port 49 acts on the valve member 82 over the area defined by seal 85.

[0154] A second reference chamber 114 is defined by the release member 90 and the second bore 91, wherein the first and second reference chambers 112, 114 are in fluid communication via a connecting bore 116. The O-ring 102 provided on the release member 90 isolates the second reference chamber 114 from the inlet port 30, such that fluid pressure at the reference port 49 acts on the release member 90 over the area defined by the seal 102.

[0155] When in the initial position shown in FIG. 2A, as noted above, the valve member 83 is in a closed position in which the outlet fluid port 44 is isolated from the inlet fluid port 30. Further, the release member 90 is in a locked position which rigidly secures the locking arrangement 104 to lock the valve member 82 in its closed position.

[0156] In the present embodiment operation of the valve assembly 16 is achieved by sequential pressure events associated with the fluid inlet 30. In this respect pressure at the inlet 30 is initially increased by increasing the pressure within the bore 40 (FIG. 1B) of the completion system 10. When an appropriate pressure is exceeded the shear pins 94 initially holding the release member 90 in place are sheared and the release member 90 is displaced axially in a first direction to an intermediate position, as shown in FIG. 2B. This axial displacement is resisted by the fluid 51 within tube 47, in addition to an optional spring 120. At this intermediate position the balls 106 of the locking arrangement 104 are still supported by the larger diameter region 96 of the release member 90 such that the valve member 82 remains locked.

[0157] Subsequent to this, as illustrated in FIG. 2C, pressure at the inlet 30 is reduced, such that the release member 90 is displaced in a second or return direction by the action of the fluid 51 in combination with the spring 120. When the release member 90 is fully displaced in the second direction, which may be defined as a release position, a snap ring 122 secures the release member 90 in place.

[0158] The release member 90 is permitted to travel a greater distance in the second direction such that the balls 106 of the locking arrangement 104 become aligned with the reduced diameter region 100 of the release member 90 when the release member 90 is located in its release position, allowing the valve member 82 to become unlocked, but still retained in its closed position by its shear screws 86. In such an arrangement, although a pressure event has occurred, the valve member 82 nevertheless remains closed. Accordingly, the pressure during the first pressure event may be utilised for another task or operation, without inadvertently causing the valve member 82 to open. Such other task or operation may include actuation of other tools or systems within a completion string, pressure testing within the completion string or surrounding annulus or the like.

[0159] In the present embodiment the pressure cycle of increasing and subsequently decreasing pressure at the inlet 30 may be considered to be a first pressure event. Further, although the release member 90 is described as being moved by increasing/decreasing pressure at the inlet 30, the same effect may be achieved by alternatively or additionally decreasing/increasing pressure of the fluid 51 within tube 47 to provide a variation in differential pressure applied across the release member 90. Such pressure variation in the tube 47 may be achieved by varying the pressure in the external space 55 (e.g., wellbore annulus).

[0160] Once the valve member 82 is unlocked, as described above, a second pressure event may be applied at the inlet 30. In the present embodiment this second pressure event is achieved by again increasing the pressure at the inlet (and/or decreasing the pressure of the fluid 51 within the tube 47). When a defined pressure differential across the valve member (specifically across the seals 84, 85) is achieved the shear screws 86 of the valve member 82 are sheared, permitting the valve member 82 to be moved under the action of the pressure differential to its open position, as illustrated in FIG. 2D, establishing fluid communication of the actuation fluid 26 (FIG. 1B) from the fluid inlet 30 to the fluid outlet.

[0161] As illustrated in FIG. 3, this actuation fluid 26 is delivered from the valve outlet 44, via the flow path 46 into the second chamber 78 defined between the sleeve 60 and the wall structure of the completion system 10. When sufficient pressure is achieved the beveled snap ring 70 is disengaged from recess 72 and the sleeve 60 is moved to an open position in which the ports 62 of the sleeve 60 become aligned with the ports 50 in the housing 48, opening the ICD 18. The snap ring 70 engages a second recess 130 to assist to hold the sleeve 60 in this open position.

[0162] It should be noted that in some cases the completion system 10 may be cemented within a wellbore. In such a case the effect of any pressure external of the completion system 10 may not act or sufficiently act on the fluid 51 within the tube 47. In such a case the tube 47 may effectively act like a rigid structure. However, as contingency for this to prevent hydraulic lock, the fluid 51 is selected to be compressible, such that movement of the valve member 82 and release member 90 may still be permitted. In fact, in some embodiments the tube 47 may be provided as a rigid member.

[0163] The valve housing 20 may be provided in a compact manner. In some instances more than one valve housing 20 may be provided, connected in series, as illustrated in FIG. 4, which illustrates a first valve housing 20a and a second valve housing 20b, wherein each housing 20a, 20b is configured in the same manner as housing 20 first shown in FIG. 2A, and as such no further description will be given.

[0164] The inlet 30a of the first housing 20a is in communication with an actuation fluid 26. The outlet 44a of the first housing 20a is in fluid communication with the inlet 30b of the second housing 20b. The outlet 44b of the second housing 20b is in fluid communication with a target (which may be the ICD 18 described above, or any other tool or system).

[0165] In FIG. 4A the first valve housing 20a is shown in an open configuration, achieved by application of two pressure events, as described above in relation to valve housing 20. As such, the actuation fluid may be delivered to and act at the inlet 30b of the second housing 20b. Application of a further two pressure events associated with the actuation fluid may cause the second valve housing 20b to become opened, as illustrated in FIG. 4B, permitting the actuation fluid to be delivered to the target location. Of course, any suitable number of valve housings may be utilised, permitting a greater number of pressure events to be applied prior to final delivery of the actuation fluid to a tool or system for operation thereof.

[0166] An alternative embodiment of a valve assembly 216 is illustrated in FIG. 5A, wherein the valve assembly 216 may be used in the completion system 10 of FIG. 1 (or any other completion system). The valve assembly 216 is similar to valve assembly 16 described above and as such like features share like reference numerals, incremented by 200.

[0167] The valve assembly 216 includes a housing 220 which includes or defines an inlet port 230, for example to communicate with the source of actuation fluid 26 of the system 10 FIG. 1B, and an outlet port 244, for example to communicate with the flow path 46 of the system 10 in FIG. 1A. The housing 220 further defines a reference port 249 for facilitating communication with a fluid 251 within an elastic tube 247.

[0168] The valve assembly 216 includes a valve member 282 in the form of an axially moveable piston mounted within a first stepped bore 283 within the housing 220. The valve member 282 is shown in FIG. 5A in a position in which the fluid outlet 244 is closed. Specifically, the valve member 282 carries a pair of O-rings 284, 285 which, when the valve member 282 is in the configuration of FIG. 5A, engage the housing 220 and straddle and seal a port 244a, which port 244a is in fluid communication with the outlet port 244 via drilled bores 244b, 244c.

[0169] The valve member 282 is shown in FIG. 5A initially secured to a fixture sleeve 285 via shear pins 286, wherein the fixture sleeve 285 is held stationary (at least in an axial direction) relative to the housing 220 via a clamping member 140, wherein the clamping member 140 is sealed relative to the housing 220 via an O-ring 142. In other embodiments the valve member 282 may be directly secured to the housing 220 via shear pins.

[0170] The valve member includes a piston head 144 which is located within the fixture sleeve 285, with a piston seal 146 provided between the piston head 144 and the fixture sleeve 285. Such an arrangement establishes a piston chamber 148 on one side of the valve member 282, and an intermediate chamber 150 which is defined between the O-ring seal 284 and the piston seal 146. A spring member 152 is located within the piston chamber 148 and acts between the clamping member 140 and the piston head 144.

[0171] The valve assembly 216 further includes a release member 290 in the form of an axially moveable piston which is located within a second stepped bore 291, wherein the release member 290 is shown in FIG. 5A initially secured to a fixture sleeve 292 via shear pins 294, wherein the fixture sleeve 292 is rigidly fixed to the housing 220. This initial position of the release member 290 may be defined as a locking position.

[0172] The release member 290 includes a large diameter region 296 which merges, via a ramped step 298, with a reduced diameter region 300. An O-ring seal 302 is provided on the reduced diameter region 300 and establishes a seal between the release member 290 and the housing 220.

[0173] One side of the release member 290 is in fluid communication with the fluid inlet 230, wherein the actuation fluid 26 (FIG. 1B) provided via the fluid inlet 230 acts against the release member 290 over the area defined by the O-ring seal 302.

[0174] The valve assembly 216 includes a locking arrangement 304 in the form of a plurality of stacked balls 306 which are located in a drilled bore 308 extending between the respective bores 283, 291, wherein the drilled bore 308 also provides fluid communication between said bores 283, 291. More particularly, the drilled bore 308 communicates with the intermediate chamber 150 formed in the first bore 283 by the valve member 282 and seals 284, 146. As such, fluid received at the inlet 230 may be communicated with this intermediate chamber 150.

[0175] The uppermost ball 306a (relative to the orientation of the Figure) is located within a locking recess 310 formed in the valve member 282, whereas the lowermost ball 306b (relative to the orientation of the Figure) is engaged by the large diameter region 296 of the release member 290. Thus, in the arrangement shown in FIG. 5A the locking arrangement 304 functions to lock the valve member 282 in the illustrated closed position.

[0176] Both the valve member 282 and the release member 290 are in fluid communication with the elastic tube 247 and the compressible fluid 251 via the reference port 249. In particular a first reference chamber 312 is defined by the valve member 282 and the first bore 283, wherein the first reference chamber 312 is in communication with the reference port 249. The O-ring 285 isolates the first reference chamber 312 from the outlet port 244, such that fluid pressure acting at the reference port 249 acts on the valve member 282 in a first direction over the area defined by seal 285. Further, a throughbore 154 extends axially through the valve member 282 such that fluid communication is provided between the first reference chamber 312 and the piston chamber 148. This arrangement permits fluid pressure acting at the reference port 249 to also act on the valve member 282 in a second, opposite direction over the area defined by the piston seal 146. In this respect the piston seal 146 defines a larger area than the O-ring seal 285, such that a larger force will be generated on the valve member in the second direction.

[0177] A second reference chamber 314 is defined by the release member 290 and the second bore 291, wherein the first and second reference chambers 312, 314 are in fluid communication via a connecting bore 316. The O-ring 302 provided on the release member 290 isolates the second reference chamber 314 from the inlet port 230, such that fluid pressure at the reference port 249 acts on the release member 290 over the area defined by the seal 302.

[0178] When in the initial position shown in FIG. 5A, as noted above, the valve member 283 is in a closed position in which the outlet fluid port 244 is isolated from the inlet fluid port 230. Further, the release member 290 is in a locked position which rigidly secures the locking arrangement 304 to lock the valve member 282 in its closed position.

[0179] In the present embodiment operation of the valve assembly 216 is achieved by sequential pressure events associated with the fluid inlet 230. In this respect pressure at the inlet 230 is initially increased by increasing the pressure within the bore 40 (FIG. 1B) of the completion system 10. When an appropriate pressure is exceeded the shear pins 294 initially holding the release member 290 in place are sheared and the release member 290 is displaced axially in a first direction to an intermediate position, as shown in FIG. 5B. This axial displacement is resisted by the fluid 251 within tube 247, in addition to an optional spring 320. At this intermediate position the balls 306 of the locking arrangement 304 are still supported by the larger diameter region 296 of the release member 290 such that the valve member 282 remains locked.

[0180] Subsequent to this, as illustrated in FIG. 5C, pressure at the inlet 230 is reduced, such that the release member 290 is displaced in a second or return direction by the action of the fluid 251 in combination with the spring 320. When the release member 290 is fully displaced in the second direction, which may be defined as a release position, a snap ring 322 secures the release member 290 in place.

[0181] The release member 290 is permitted to travel a greater distance in the second direction such that the balls 306 of the locking arrangement 304 become aligned with the reduced diameter region 300 of the release member 290 when the release member 290 is located in its release position, allowing the valve member 282 to become unlocked, but still retained in its closed position by its shear screws 286. In such an arrangement, although a pressure event has occurred, the valve member 282 nevertheless remains closed. Accordingly, the pressure during the first pressure event may be utilised for another task or operation, without inadvertently causing the valve member 282 to open. Such other task or operation may include actuation of other tools or systems within a completion string, pressure testing within the completion string or surrounding annulus or the like.

[0182] In the present embodiment the pressure cycle of increasing and subsequently decreasing pressure at the inlet 230 may be considered to be a first pressure event. Further, although the release member 290 is described as being moved by increasing/decreasing pressure at the inlet 230, the same effect may be achieved by alternatively or additionally decreasing/increasing pressure of the fluid 251 within tube 247 to provide a variation in differential pressure applied across the release member 290. Such pressure variation in the tube 247 may be achieved by varying the pressure in the external space 55 (e.g., wellbore annulus).

[0183] Once the valve member 282 is unlocked, as described above, a second pressure event may be applied at the inlet 230. In the present embodiment this second pressure event is achieved by again increasing the pressure at the inlet 230 (and/or decreasing the pressure of the fluid 251 within the tube 247). Such inlet pressure is communicated to the intermediate chamber 150, held between seals 284, 146. As the sealing area of seal 146 is larger than that of seal 284, a net force will be established in a first direction, and when this net force reaches a predefined magnitude (taking into account the resistance force generated by the pressure of the fluid 251 and the spring 152) the shear screws 286 of the valve member 282 are sheared, permitting the valve member 282 to be moved under the action of the net force in the first direction towards an intermediate position, as illustrated in FIG. 5D. Movement of the valve member 282 is halted at the intermediate position by a movement limiter in to form of a stem 156 extending from the clamping member 140. When in this intermediate position the O-ring seals 284, 285 still straddle the port 244a, thus maintaining the fluid outlet 244 closed.

[0184] Subsequent to this, pressure at the inlet 230 may be reduced (and/or the pressure of the fluid 251 may be increased), with such pressure variation forming part of the second pressure event. This pressure variation may result in the valve member 282 being moved in a second or reverse direction by the force dominance of the spring 152 and fluid pressure 251 to eventually position the valve member 282 in its open position, as illustrated in FIG. 5E, establishing fluid communication of the actuation fluid 26 (FIG. 1B) from the fluid inlet 230 to the fluid outlet 244. As such, final opening of the valve member 282 may be achieved during a pressure bleed-down event.

[0185] It should be noted that the valve assembly 216 may also be arranged in a series manner.

[0186] 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.