PRESSURE ACTUATED DOWNHOLE DEVICE

Abstract

A downhole valve, such as a safety valve or sub-sea safety valve (SSSV). The downhole valve comprising: a housing; a flow path between a valve inlet and a valve outlet; a valve mechanism; and a piston member; wherein the valve mechanism is operable by actuation of the piston member to selectively open and close the flow path between the valve inlet and valve outlet; and the piston member is actuatable by a pressure differential between an annulus pressure at the valve and a pressure at the valve outlet and/or in a portion of the flow path closest to the valve outlet. The valve can comprise an opening for receiving the annular pressure that is isolated from the valve inlet and valve outlet. The downhole valve can be configured such that it prevents operation of the valve mechanism to open and/or close the flow path by a pressure differential between the valve inlet and valve outlet.

Claims

1-28. (canceled)

29. A downhole valve, comprising: a housing; a flow path between a valve inlet and a valve outlet; at least one valve mechanism; and at least one piston member; wherein: the at least one valve mechanism is operable by actuation of the at least one piston member to selectively open and close the flow path between the valve inlet and valve outlet; and the at least one piston member is actuatable by a pressure differential between an annulus pressure at the valve and a pressure at the valve outlet and/or in a portion of the flow path closest to the valve outlet and/or the pressure at the valve outlet.

30. The downhole valve of claim 29, wherein operation of the valve mechanism to open and/or close the flow path is unaffected by the pressure applied at the valve inlet and/or the downhole valve is configured such that the valve mechanism is not operable to open and/or close the flow path by changes in pressure at the valve inlet alone.

31. The downhole valve of claim 29, wherein: the valve outlet is configured to be in fluid communication with a downhole pump or other artificial lift system that is provided uphole of the downhole valve, in use, and the pump or other artificial lift system is operable to vary the pressure at the valve outlet and/or the differential between an annulus pressure at the valve and a pressure at the valve outlet to thereby actuate the at least one valve mechanism.

32. The downhole valve of claim 29, wherein the annulus is or comprises a volume that is radially outwardly of the valve, between the valve and a wellbore wall, casing, liner or tubular in which the valve is located or locatable, in use.

33. The downhole valve of claim 29, comprising an opening for receiving the annular pressure to actuate the piston member that is isolated from the valve inlet and valve outlet.

34. The downhole valve of claim 29, comprising: at least one first pressure chamber in fluid communication with the annulus and isolated from the flow path from the valve inlet to the valve outlet; and at least one second pressure chamber, in fluid communication with the valve outlet and/or with at least part of the flow path from the valve inlet to the valve outlet, wherein each first and second pressure chamber is separated by a respective piston member.

35. The valve according to claim 29, wherein the valve mechanism comprises a sliding sleeve, a poppet, a ball, or a flapper.

36. The valve according to claim 29, comprising biasing means configured to bias the piston member against the pressure from the annulus and/or configured to bias the valve mechanism into the closed configuration.

37. The valve according to claim 36, wherein the biasing means is configured to bias the valve mechanism towards or against the pressure at the inlet or against being operated by a pressure differential between the valve inlet and valve outlet.

38. The valve according to claim 29, wherein one or more of the valve mechanisms comprises a downhole or valve inlet end surface and a sloping face that extends obliquely radially outwardly from the downhole or valve inlet end surface of the valve mechanism, such that a diameter of the downhole or valve inlet end surface of the valve mechanism is less than a diameter of the valve mechanism at the other end of the sloping face.

39. The valve according to claim 29, wherein the valve mechanism comprises a sub-chamber located behind the downhole or inlet end face and/or the sloping face and/or within the valve mechanism, wherein the sub-chamber is in fluid communication with a downstream or uphole or annulus pressure and/or the first pressure chamber.

40. The valve according to claim 29, wherein the valve mechanism defines a through passage from an inlet end of the valve mechanism to an outlet end of the valve mechanism and the valve comprises a feed passage in fluid communication between the valve inlet and a feed passage outlet, wherein at least one of: the feed passage outlet faces a side wall of the valve mechanism when the valve mechanism is in a closed configuration; or at least the feed passage outlet and/or a portion of the feed passage immediately adjacent the feed passage outlet and/or the flow of fluid therein is perpendicular, angled or oblique to a direction of motion of the valve mechanism.

41. The valve according to claim 29, configured such that, when in the open configuration, there is a pressure drop across the valve.

42. The valve according to claim 29, wherein the valve comprises a plurality of piston members configured such that fluid from the valve inlet applies a force on at least one of the piston members that opposes the force applied on at least one other of the piston members.

43. The valve according to claim 42, wherein the fluid from the valve inlet applies a force on the at least one of the piston members in a direction so as to close the at least one valve mechanism and applies a force on the at least one other of the valve mechanisms in a direction so as to open the at least one valve mechanism, wherein the force on the at least one of the piston members is the same as the force on the at least one other piston member and/or the differential between the force on the at least one of the piston members and the force on the at least one other piston member is less than a biasing force applied by the biasing means.

44. The valve according to claim 43, wherein a valve outlet side surface area or diameter of the at least one piston member is different to a valve outlet side surface area or diameter of the at least one other piston member.

45. The valve according to claim 29, wherein the valve is a bi-directional valve and is configured to be remotely operable by pressure supplied from the remote location into a configuration in which the downhole device allows fluid flow through the downhole device from uphole to downhole and operable by operation of the pump into a configuration in which the downhole device allows fluid flow through the downhole device from downhole to uphole.

46. The valve according to claim 45, comprising an other operating mechanism that is configured to receive pressure from the remote location to selectively open or close the flowpath, the other operating mechanism comprising a shuttle sleeve and a plurality of seals, the shuttle sleeve being configured to receive pressure from downhole at one of the seals and pressure from uphole at an other of the seals.

47. The valve of claim 46, wherein the seals are unidirectional seals, wherein the seal that receives pressure from downhole is configured to resist the pressure from downhole whilst the seal that receives the pressure from uphole is configured to resist the pressure from uphole.

48. The valve of claim 46, wherein: the effective diameter or inner diameter of the seal of the other operating mechanism that receives the pressure from downhole is less than a seal diameter of the at least one valve mechanism; and/or the effective diameter or outer diameter of the seal of the other operating mechanism that receives the pressure from the remote location is greater than the seal diameter of the at least one valve mechanism.

49. A downhole assembly comprising: the valve of claim 29; and a pump or other artificial lift system, such as an ESP; and/or a packer, such as a seal bore packer.

50. The assembly of claim 49, wherein at least part of the valve is coupled to between the pump and the packer such that at least part of the valve is uphole of the packer and downhole of the pump, in use.

51. The assembly of claim 49, wherein: the packer comprises a support member that defines a through bore and a sealing element for sealing between the support member and the wall of the wellbore, casing, liner or outward tube so as to close the annulus; the valve inlet is arranged to receive fluid from downhole of the sealing element in use; and the pump is configured to pump fluid from the flow path and/or the valve outlet of the valve into the annulus uphole of the sealing element.

52. The assembly of claim 51, wherein the pump is configured so as to create and/or vary the pressure differential between the annulus and the valve outlet and/or the flow channel in the valve and/or create and/or vary the pressure differential between the first pressure chamber and the second pressure chamber of the valve by selectively pumping fluid from the flow path and/or the valve outlet of the valve into the annulus uphole of the packer.

53. The assembly of claim 52, wherein the pump is configured to open the valve by pumping fluid from the flow path and/or the valve outlet of the valve into the annulus uphole of the packer; and configured to close the valve by reducing or stopping the pumping of fluid from the flow path and/or the valve outlet of the valve into the annulus uphole of the packer.

54. An assembly comprising: a downhole pump; and a pressure actuated downhole valve, wherein the valve comprises: a housing; a flow path between a valve inlet and a valve outlet; at least one valve mechanism; and at least one piston member; wherein: the at least one valve mechanism is operable by actuation of the at least one piston member to selectively open and close the flow path between the valve inlet and valve outlet; and the at least one piston member is actuatable by a pressure differential and/or a pressure change at the valve outlet produced by the pump.

55. The assembly of claim 54, wherein the pressure differential produced by the pump is a pressure differential between an annulus pressure at the valve and a pressure at the valve outlet and/or in a portion of the flow path closest to the valve outlet.

56. A method of operating the assembly of claim 49, wherein the method comprises at least one of: controlling the pump or other artificial lift system so that the pump or other artificial lift system operates above a threshold so as to cause a pressure or pressure differential, such as a pressure differential between the annulus and the valve outlet or a pressure at a valve outlet, to thereby actuate the valve mechanism so as to open the flow path through the valve; or controlling the pump or other artificial lift system so that the pump or other artificial lift system is inactive or operating below the threshold so as to reduce or remove the pressure differential, such as the pressure differential between the annulus and a valve outlet, flow path or second pressure chamber of the valve, or to increase the pressure at the valve outlet to thereby actuate the valve mechanism so as to close the flow path.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0073] 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:

[0074] FIG. 1 is a simplified, diagrammatic, longitudinal cross-sectional view of a downhole assembly comprising a pressure operated valve;

[0075] FIG. 2 is a simplified cut-away view of a pressure operated valve.

[0076] FIG. 3 is a simplified cross section of the valve of FIG. 2 in the downhole assembly of FIG. 1;

[0077] FIG. 4 is a simplified cross section of the valve of FIG. 2;

[0078] FIG. 5 is a simplified cross-sectional view of an alternative pressure operated valve in a closed configuration;

[0079] FIG. 6 is a simplified cross-sectional view of the pressure operated valve of FIG. 5 is an open configuration;

[0080] FIG. 7 is a simplified cross-sectional view of an alternative pressure operated valve in a closed configuration;

[0081] FIG. 8 is a simplified cross-sectional view of an alternative pressure operated valve in an open configuration;

[0082] FIG. 9 is a flowchart illustrating a method of operation of a pressure operated valve, such as those of any of FIGS. 2 to 8;

[0083] FIG. 10 is a cross sectional view of an alternative pressure operated valve in a closed configuration;

[0084] FIG. 11 is a perspective view of the pressure operated valve of FIG. 10;

[0085] FIG. 12 is a cross sectional view of the pressure operated valve of FIG. 10 in a closed configuration;

[0086] FIG. 13 is a detailed cross sectional view of the pressure operated valve of FIG. 10 in a closed configuration;

[0087] FIG. 14 is a cross sectional view of the pressure operated valve of FIG. 10 in an open configuration;

[0088] FIG. 15 is a detailed cross sectional view of the pressure operated valve of FIG. 10 in an open configuration;

[0089] FIG. 16 is a cross sectional view of the pressure operated valve of FIG. 10 in a test configuration;

[0090] FIG. 17 is a detailed cross sectional view of the pressure operated valve of FIG. 10 in a test configuration;

[0091] FIG. 18 is a detailed cross sectional view of the pressure operated valve of FIG. 10 in a test configuration; and

[0092] FIG. 19 is a cross sectional view of the pressure operated valve of FIG. 10 with a burst valve opened.

DETAILED DESCRIPTION OF DRAWINGS

[0093] FIG. 1 shows an assembly 5 comprising a safety valve 10 disposed between a packer 15 and a pump 20. Although, only half of the assembly 5 is shown, it will be appreciated that another half of components such as the valve 10, packer 15, pump 20 and production tubing 30 will be present. In this example, the pump 20 is provided uphole of the valve 10, which is in turn provided uphole of the packer 15. The pump 20 in this example is a cable deployed electric submersible pump (ESP) that is connected to the surface by a control line 25. However, in other embodiments, other types of pump or artificial lift system could be used, such as a jet pump, a capillary string, a syphon string, a velocity string, or the like. In embodiments, the pump or other artificial lift system comprises a cable, line or conduit deployed or operated device. The assembly is provided downhole inside tubing 30, in this case production tubing that is incorporated in a production string used to produce well fluids.

[0094] The pump comprises an electric motor 37 provided downhole of a pump section 40 that is operable by the motor 37. The electric motor 37 is powered and controlled from the surface using the control line 25. Although an electric motor 37 is provided in this example, it will be appreciated that other types of motor could be used, such as a hydraulic pump (e.g. a hydraulic submersible pump (HSP).

[0095] The packer 15 is a seal bore packer that comprises a support member 41 that defines a bore therethrough and a sealing member 42 that bears between the production tubing 30 and the support member 41 of the packer 15. The valve 10 and pump 20 are spaced apart from an inner wall of the tubing 30 so as to define part of an annulus 105. The sealing member 42 of the packer 15 seals the annulus. As such, the packer 15 separates fluid communication from downhole (through the bore of the packer 15) and uphole (i.e. from pump outlets of the pump 20). In other words, fluid from downhole of the packer 15 can be sucked up through the bore of the packer 15 by the pump 20 but fluid in the annulus 105 upstream of the packer 15 is prevented from returning downhole by the sealing member 42. The valve 10 can either be run in (and retrieved) with the packer 15 or provided separately. The valve 10, packer 15 and pump 20 can connect together using any suitable coupling method, such as using snap latches and/or the like.

[0096] FIG. 2 shows an example 10a of the valve 10 and FIG. 3 shows the valve 10a of FIG. 2 assembled into the assembly 5a, comprising the packer 15 and pump 20. FIG. 4 shows a more detailed cross section of the valve 10a shown in FIGS. 2 and 3. Although FIG. 3 shows only part of the valve mechanism 65a and valve housing 35a for clarity of illustration, it will be appreciated that these extend around in three dimensions, as shown in FIG. 2, and will comprise corresponding parts in the lower half of the production tubing 30.

[0097] The valve 10a is beneficially operated by drawdown using the pump 20 without a dedicated control line that can be difficult to deploy and would be difficult to route past the pump 20 to reach the surface. Furthermore, the valve 10a is configured so as not to be operated by pressure differential between a valve inlet 45a and valve outlet 50a (i.e. a differential between uphole and downhole pressures) and is instead only operable between open and closed configurations by pressure differentials generated by the pump 20.

[0098] The valve 10a comprises a housing 35a, the valve inlet 45a and the valve outlet 50a connected by a valve bore 55a that is defined by the housing 35a of the valve 10a. The valve inlet 45a is configured for connection to the packer 15 bore whilst the valve outlet 50a is configured for fluid connection to a pump inlet 60 (see FIG. 3). In this way, when the valve 10a is in the open configuration, then fluid can pass from the bore in the packer 15, through the valve inlet 45a, the valve bore 55a and the valve outlet 50a to the pump inlet 60. Thereafter, the fluid can be pumped by the pump mechanism out from pump outlets 120 (see FIG. 3) into the annulus 105.

[0099] The valve 10a comprises a valve mechanism 65a, in this case in the form of a poppet, that is slidably located within the valve bore 55a. The use of a poppet is beneficial as it copes well with unloading under pressure and may provide a higher flow rate for a given size, but it will be appreciated that other suitable mechanisms could be used. A valve seat 70a in the valve bore 55a is configured to engage a sealing surface 72a of the valve mechanism 65a (i.e. the poppet) when the valve 10a is in the closed configuration in order to limit the range of motion of the valve mechanism 65a and to seal the valve bore 55a closed. An end stop 75 is provided to limit the range of motion of the valve mechanism 65a when the valve 10a is in the open configuration. A biasing member 115 is provided to bias the valve mechanism 65a into the closed configuration in which the sealing surface 72 of the valve mechanism 65a seals against the valve seat 70 in order to close the valve bore 55.

[0100] In this case, the biasing member 115 is in the form of a coiled spring that bears between a piston member 80a and a spring seat in the valve housing 35a so as to bias the valve mechanism 65a towards the valve 10a closed configuration. Although a biasing member 65a in the form of a coil spring is described, other biasing arrangements could be used to produce the same result.

[0101] The valve mechanism 65a is provided with the integral piston member 80a, in this case in the form of a radially protruding flange. A pump end portion 82a of a side wall of the valve mechanism 65a that is on an opposite side of the piston member 80a to the valve seat 70 is configured to seal against the wall of the valve bore 55. The wall of the valve bore 55a comprises a recessed part 85a having a diameter that is wider than adjacent portions of the valve bore 55. A radially outer part of the piston member 80a is provided with a piston 87 seal that seals against the recessed part 85 of the bore 55. In this way, the outer wall of the valve mechanism 65a and the recessed part 85 of the bore 55a define a chamber that is separated into a first chamber 90 and a second chamber 95 by the piston member 80a. The housing 35a is provided with a through channel 100a between the first chamber 90 and the annulus 105 located between the radially outer surface of the housing 35a of the valve 10a and a radially inner surface of the tubing 30. In this way, the first chamber 90 is in fluid communication with, and at the same pressure as, the annulus 105. Rather than taking the specific form shown, the through channel may be implemented using a control line or other conduit or mechanism to ensure that the first chamber 90 follows the pressure in the annulus 105. For example, if the valve is deployed at the bottom of a feedthrough packer, then a control line may extend between the first chamber 90 and a feedthrough of the feedthrough packer in order to sense pressure in the annulus 105.

[0102] The pump end portion 82 of the valve mechanism 65a that forms the second chamber 95 is provided with a through passage 110 that is in fluid communication with the pump inlet 60 via the portion of the valve bore 55a that is closest to the valve outlet 50. In this way, the second chamber 95 is at the same pressure as the pump inlet 60. This arrangement allows the valve 10a to be operated responsive to operation of the pump 20.

[0103] In particular, when the pump 20 is operational, it will suck fluid in fluid from the valve bore 55a via the pump inlet 60 and expel the fluid via pump outlets 120 into the annulus 105. This causes a pressure drop at the pump inlet 60 with respect to the pump outlets 120, which conversely experience an increase in pressure. This in turn creates a pressure differential between the pump inlet 60 (and thereby the valve outlet 50a, the portion of the valve bore 55a closest to the valve outlet 55a and the second chamber 95) and the pump outlet 120 (and thereby the annulus 105 and the first chamber 90).

[0104] As such, the piston member 80a experiences a pressure differential between the relatively high annulus 105 pressure on one side and the relatively lower valve bore 55a pressure and the force applied by the biasing member 115 on the other. When the pressure differential on the piston member 80a reaches a certain threshold that depends, amongst other factors, on the force exerted by the biasing member 115, the piston member 80a and thereby the valve mechanism 65a are moved to compress the biasing member 115 due to the higher pressure in the annulus 105 when the pump 20 is operational. This results in the sealing surface 72 of the valve mechanism 65a being moved away from the valve seat 70a to thereby open the valve 10a and allow fluid flow from the valve inlet 45 through the valve bore 55 to the valve outlet 50/pump inlet 60.

[0105] Optionally, even when in the open configuration, the valve mechanism 65a acts to inhibit flow (e.g. by being located within the valve bore 55) and thereby cause a certain pressure drop across the valve 10a. In this way, it may be easier for the pump 20 to maintain the pressure differential needed to hold the valve mechanism 65a open, as the opening of the valve 10 may result in a rise in the pressure in the valve bore 55.

[0106] When the pump 20 is switched off or its output or operation is reduced such that the differential pressure drops below the threshold (e.g. due to fluid from the valve inlet 45a passing into the valve bore 55a whilst the valve 10a is still open to equalise the pressure), then the biasing member 115 acts to return the valve mechanism 65a into the closed configuration in which the sealing surface 72 of the valve mechanism 65a is returned to seal against the valve seat 70 to thereby close the valve 10a and prevent fluid flow from the valve inlet 45a through the valve bore 55a to the valve outlet 50a/pump inlet 60.

[0107] In this way, the valve 10a is reversibly operable between the open and closed configurations by operation of the pump 20 and without a dedicated control line for the valve 10a such as an electrical or hydraulic control line that runs between the valve 10a and the surface. As such, the valve 10a can be conveniently located downhole of the pump 20 without having to make provisions for the running of a control line for the valve 10a past the pump 20.

[0108] The valve mechanism 65 (e.g. the poppet 65a) is provided with a chamber 125 behind an end surface 130 of the valve mechanism 65a that is closest to the packer 15 (e.g. the downhole end). The chamber 125 is provided with one or more communication channels 135 so that the chamber 125 receives downstream (e.g. uphole) pressure (e.g. from the first chamber 90). Furthermore, the outer surface of the valve mechanism 65 slopes obliquely radially outwardly as it extends away from the end surface 130 of the valve mechanism 65 that is closest to the packer 15 (e.g. the downhole end). In this way, the surface area of the chamber 125 is larger than the area of the surface at the end 130 of the valve mechanism 65 that is closest to the packer 15. At least part of the sloping section of the valve mechanism 65 optionally forms the sealing surface 72 of the valve mechanism 65.

[0109] In this way, the downstream pressure acts on the sloping part of the valve mechanism (e.g. the sealing surface) and acts to keep the valve mechanism 65 (e.g. the poppet 65a) closed when the pump is not operational or operating below the threshold, regardless of the pressure differential acting across the valve 10a between the valve inlet 45a and the valve outlet 50a, e.g. at least under normal or rated operating pressures of the valve 10a. In this way, the valve 10a is operable between the open and closed configurations only by operation of the pump 20 (e.g. by the differential pressure between the annulus 105 and the pump inlet 60/valve outlet 50a) and not by the differential pressure between the valve inlet 45a and valve outlet 50a. In this way, the valve 10a may be more surely operable only by the pump 20 and resists or prevents mis-operation between the open and closed configurations due to the differential pressure between the valve inlet 45a and the valve outlet 50a.

[0110] Although a particularly beneficial arrangement is described above, it will be appreciated that other valves that operate on similar principles are possible. For example, although a beneficial valve 10a in which the valve mechanism 65 is a poppet 65a is described above, other valve mechanisms 65 such as sliding sleeves, flapper valves, ball valves, and/or the like, could be used.

[0111] An alternative example that is similar to that of FIGS. 2 and 3 but in which the valve mechanism 65 is a sliding sleeve 65b is shown in FIGS. 4 to 6. Like reference numerals are used to indicate components of the example of FIGS. 4 to 6 that perform a similar function to those shown in FIGS. 2 and 3 but suffixed with ‘b’ rather than ‘a’.

[0112] FIGS. 5 and 6 show a cross sectional view of an alternative valve 10b. FIG. 5 shows a detailed cross section of the valve 10b in a closed configuration, whilst FIG. 6 shows the valve 10b in an open configuration.

[0113] The valve 10b comprises a housing 35b that houses a valve mechanism 65 in the form of a sliding sleeve 65b that is slidably mounted in the valve bore 55b. In this example, the sliding sleeve 65b comprises a hollow elongate generally cylindrical tubular member with a longitudinally extending bore 200 therethrough. The sliding sleeve 65b comprises one or more piston members 80b in the form of a flange that comprises a piston seal 87 on a radially outer surface thereof. The flange forming the piston member 80b extends radially outwardly from the sliding sleeve 65b such that the piston seal 87 engages and seals against an inner wall of a recessed part 85b of the valve bore 55b. The piston seal 87 in this example is in the form of an O-ring but it will be appreciated that other seal types could be used. In this way, the recessed portion 85b is divided into a first chamber 90b and a second chamber 95b by the piston member 80b, the relative volumes of which are variable by sliding movement of the piston member 80b. Similarly to the embodiment of FIGS. 2 and 3, the valve mechanism 65b is biased towards and/or into the closed configuration by a biasing member 115b such as a spring. Optionally, more than one piston member 80b, recessed parts 85b and corresponding first and second chambers 90b, 95b could be provided if more force is required to move the valve mechanism 65b.

[0114] As in the example of FIGS. 2 and 3, the portion of the housing 35b that forms the wall of the first chamber 90b comprises an opening 100b that extends form the first chamber 90b and is open on an outer surface of the valve 10b. In this way, the first chamber 90b is in fluid communication with the annulus 105 via the opening 100b. The second chamber 95b is in fluid communication with the pump inlet 60 via a portion of the valve bore 55b and the valve outlet 50b.

[0115] In this way, the valve mechanism 65 in the form of the sliding sleeve 65b is selectively and reversibly movable back and forth between the closed configuration shown in FIG. 5 and the open configuration shown in FIG. 6 by operation of the pump 20 to vary the pressure differential between the annulus 105 and the valve outlet 50/pump inlet 60.

[0116] Operation of the pump 20 acts to pump fluid from the valve bore 55b through the pump inlet 60 and out from the pump outlets 120 into the annulus 105. This creates a pressure differential between the annulus 105 (and thereby the first chamber 90b) and the pump inlet 60 (and thereby the valve outlet 50b, at least part of the valve bore 55b and the second chamber 95b), with the annulus 105 being at a higher pressure than the pump inlet 60. If the pressure differential exceeds a certain threshold (determined in part by the biasing member 115 and friction) then the piston member 80b and thereby the valve mechanism 65 (i.e. the sliding sleeve 65b) is driven from the closed configuration shown in FIG. 5 to the open configuration shown in FIG. 6. If the pressure differential reduces below the threshold, then the valve mechanism 65 (i.e. the sliding sleeve 65b) is returned from the open configuration shown in FIG. 6 to the closed configuration shown in FIG. 5 under the action of the biasing member 115. In this way, the valve 10b is reversibly and selectively operable between the open and closed configurations by the pump 20.

[0117] In the example of FIGS. 5 and 6, a feed passage 210 extends from the valve inlet 45b to an opening 215 proximate an end of the valve mechanism 65 (i.e. the sliding sleeve 65b) that is furthest from the pump 20, in use. The opening 215 opens out part way along an inner side wall of the valve bore 55b, towards the end of the valve bore 55b that is furthest from the pump 20, in use. The opening 215 and/or a portion of the feed passage 210 closest to the opening 215 is arranged such that it faces perpendicularly or at least obliquely (e.g. 45° or more) to a direction in which the valve mechanism 65b moves.

[0118] The valve mechanism 65, i.e. the sliding sleeve 65b, is arranged such that, in the closed configuration shown in FIG. 6, a side wall of the sliding sleeve 65b closes and seals the opening 215. In particular, the sliding sleeve 65b comprises a pair of inlet seals 220, 225 that seal between a radially outer surface of the side wall of the sliding sleeve 65b and the inner side wall of the valve bore 55b. In this example the inlet seals 220, 225 comprise O-rings but other types of seals could be used.

[0119] In the open configuration shown in FIG. 6, the inlet seals 220, 225 and an open end 230 of the sliding sleeve 65b that is at an opposite end of the sliding sleeve 65b to the pump 20, in use, are located on a pump side of the opening 215. In this way, the opening 215 is in fluid communication with the valve bore 55 and the open end 230 of the sliding sleeve 65b such that fluid from the valve inlet 45b can flow through the feed passage 210, out through the opening 215 into the valve bore 55 and down through the bore 200 that runs longitudinally through the sliding sleeve 65b to the valve outlet 50b and thereby the pump inlet 60.

[0120] In the closed configuration shown in FIG. 5, one of the inlet seals 220 and the open end 230 of the sliding sleeve 65b that is at an opposite end of the sliding sleeve 65b to the pump 20, in use, are located on a side of the opening 215 that is away from the pump 20, in use, and the other of the inlet seals 225 is located on the opposite side of the opening 215 (i.e. the side of the opening 215 that is toward the pump 20, in use). As such, one of the pair of inlet seals 220 is located on one side of the opening 215 and the other of the inlet seals 225 is located on the other side of the opening, with the outer side wall of the sliding sleeve 65b spanning the two inlet seals 225, to thereby seal closed the opening 215 and to isolate the open end 230 of the sliding sleeve 65b from the opening 215.

[0121] As the part of the feed passage 210 closest to the opening 215 extends perpendicularly to the direction of movement of the sliding sleeve 65b and faces a radially outer side wall of the sliding sleeve rather than one of the ends 230, 235 of the sliding sleeve, when the valve 10b is in the closed configuration shown in FIG. 5, the valve 10b stays closed regardless of the pressure differential between the valve inlet 45b and the valve outlet 50b. The biasing member 115 also assists with keeping the valve in the closed configuration. Thus, the valve 10b is more surely operable only by operation of the pump 20 and/or the pressure differential between the annulus 105 and the part of the valve bore 55b that is in fluid communication with the pump inlet 60, and is not or less subject to mis-operation due to variations in differential pressure between the valve inlet 45b and valve outlet 50b.

[0122] Although various examples of types of valve mechanisms 65 and methods for ensuring that the valve 10, 10a, 10b/valve mechanism 65, 65a, 65b is operable by the pump 20 and/or differential pressure between the annulus 105 and part of the valve bore 55 and is not operable by pressure differential between the valve inlet 45 and valve outlet 50 are described above, the present disclosure is not limited to these, and other possibilities could be used and/or would be apparent to a skilled person from the present disclosure.

[0123] FIGS. 7 and 8 show a cross sectional view of another alternative valve 10c. FIG. 7 shows a detailed cross section of the valve 10c in a closed configuration, whilst FIG. 8 shows the valve 10c in an open configuration.

[0124] The valve 10c comprises a valve housing 35c that defines a valve bore 55c that extends through the valve housing 35c between a valve inlet 45c and a valve outlet 50c (wherein the valve outlet 50c is configured to be in fluid communication with a pump inlet 60 of the pump 20 in use). Although the pump 20 is not shown, it could be arranged in a corresponding manner to that shown in FIG. 1 or 3. The valve 10c further comprises a valve mechanism 65c, in this case in the form of a double poppet, that is slidably located within the valve bore 55c provided in a valve housing 35c. The valve mechanism 65c comprises two sealing surfaces, namely first and second sealing surfaces 72c′ and 72c″, and two corresponding valve seats, namely first and second valve seats 70c′ and 70c″.

[0125] The valve mechanism 65c is selectively actuatable between the open configuration shown in FIG. 8 in which fluid may pass from the valve inlet 45c to the valve outlet 50c and the closed configuration shown in FIG. 7 in which fluid flow from the valve inlet 45c to the valve outlet 50c is prevented. In particular, the valve mechanism is actuatable between the open and closed configurations responsive to the pressure at the valve outlet 50c, which depends on the operation of the pump 20 that is in fluid communication with the valve outlet 50c in use, and irrespective of the pressure applied to the valve inlet 45c, i.e. the actuation of the valve mechanism 65c is unaffected by the fluid pressure at the valve inlet 45c.

[0126] The valve mechanism 65c is configured such that, when the valve mechanism 65c is in the closed configuration, the first and second valve seats 70c′ and 70c″ respectively engage the first and second sealing surfaces 72c′ and 72c″ so as to seal the valve bore 55c closed. The valve mechanism 65c is configured such that, when the valve mechanism 65c is in the open configuration, the first and valve seats 70c′ and 70c″ are spaced apart from the first and second sealing surfaces 72c′ and 72c″ respectively so as to open the valve bore 55c.

[0127] A biasing member 115 is provided to bias the valve mechanism 65c toward the closed configuration. In this case, the biasing member 115 is in the form of a coiled spring that bears between the valve mechanism 65c and a fixed spring seat (not shown) in the valve housing 35c so as to provide a basing force that biases the valve mechanism 65c towards the valve 10c closed configuration. Although a biasing member 65a in the form of a coil spring is described, other biasing arrangements could be used to produce the same result. When the pump is not being operated, then the valve mechanism 65c is biased into the closed configuration, i.e. the valve 10c defaults to the closed configuration. However, it will be appreciated that in other embodiments, the reverse could be configured, i.e. the valve defaults to open.

[0128] The valve mechanism 65c is provided with two piston members, namely first and second piston members 80c′, 80c″, in this case in the form of radially protruding flanges. The first and second piston members 80c′, 80c″ and the first and second sealing surfaces 72c′ and 72c″ are all coupled together or integral so that they are slidable together in tandem. Both the first and second piston members 80c′, 80c″ are in fluid communication with a chamber 90c formed in the valve housing 35c, the chamber 90c being in fluid communication with the valve inlet 45c.

[0129] Both the first piston member 80c′ and the second piston member 80c″ are provided between the first chamber 90c and a portion of the valve bore 55c that is in fluid communication with the valve outlet 50c. The first piston member 80c′ comprises a face 805 that faces into the chamber 90c and a face 815 that faces towards the valve bore 55c. The second piston member 80c″ comprises a face 810 that faces into the chamber 90c and a face 820 that faces towards the valve bore 55c.

[0130] The first and second piston members 80c′, 80c″ are configured to oppose each other. In this example, the first piston member 80c′ is configured such that positive fluid pressure in the chamber 90c acts on the face 805 of the first piston member 80c′ that pushes the first sealing surface 72c′ onto the first valve seat 70c′ and pushes the second sealing surface 72c″ onto the second valve seat. In contrast, the second piston member 80c′ is configured such that positive fluid pressure in the chamber 90c acts on the face 810 of the second piston member 80c″ that pushes the first sealing surface 72c′ away from the first valve seat 70c′ and the second sealing surface 72c″ away from the second valve seat 70c″.

[0131] Properties of the first and second piston members 80c′, 80c″, such as the piston diameter, piston surface area, seal friction and the like, can be selected so that the fluid in the chamber 90c applies a substantially equal force on both the face 805 of the first piston member 80c′ and the face 810 of the second piston member 80c″ (or at least such that any difference in force is always less than the biasing force applied by the biasing member for at least the operational pressure range of the valve 10c). For example, the contact area between the first sealing surface 72c′ and the first valve seat 70c′ may be at the same diameter as, or radially overlap, the contact point between the second sealing surface 72c″ and the second valve seat 70c″. In this way, the piston diameter or area of the first piston member 80c′ and the second piston member 80c″ that faces into the chamber 90c when the valve mechanism 65c is in the closed configuration may be substantially the same. In this way, the valve 10c cannot be actuated between the open and closed configurations by simply changing the pressure at the valve inlet 45c alone, as this would simply apply opposing similar or equal forces on each of the first and second piston members 80c′, 80c″ such that there is no net effect, or at least insufficient net effect to overcome the biasing force applied by the biasing member 115. Instead the valve mechanism 65c is actuatable between the open and closed configurations responsive to operation of the pump 20 to change the pressure at the valve outlet 50c regardless or irrespective of the pressure at the valve inlet 45c.

[0132] The closed configuration is shown in FIG. 7, in which the combination of the positive pressure differential between the valve inlet 45c/pressure chamber 90c and the valve outlet 50c/pump inlet 60 acting on the face 805 of the first piston member 80c′ and the biasing force applied by the biasing member 115 overcomes the effects of the pressure differential between the valve inlet 45c/pressure chamber 90c and the valve outlet 50c/pump inlet 60 acting on the opening face 810 of the second piston member 80c′, such that the first sealing surface 72c′ is forced into sealing engagement with the first valve seat 70c′ and the second sealing surface 72c″ is forced into sealing engagement with the second valve seat 70c″ so as to seal the valve bore 55c closed.

[0133] However, the piston diameter or surface area of the first piston member 80c′ that faces into the valve bore 55c may be smaller than the piston diameter or surface area of the second piston member 80c″ that faces into the valve bore 55c. For example, a diameter and/or surface area of the face 815 of the first piston member 80c′ on the valve bore 55c side of the contact point between the first sealing surface 72c′ and the first valve seat 70c′ when the valve 10c is in the closed configuration may be less than a diameter and/or surface area of the face 820 of the second piston member 80c″ that faces into the valve bore 55c from the contact point between the second sealing surface 72c″ and the second valve seat 70c″. This may be achieved, for example, by having the first and second sealing surfaces 72c′, 72c″ on sloping faces 815, 810 of the first and second piston members 80c′, 80c″, wherein the face 815 of the first piston member 80c′ reduces in diameter from the valve inlet 45c side to the valve bore 55c side whereas the face 810 of the second piston member 80c″ increases in diameter form the valve inlet 45c side to the valve bore 55c side. As a result, changing the pressure at the valve outlet 50c and thereby in the valve bore 55c will have a different effect on the first piston member 80c′ than on the second piston member 80c″. Consequently, respectively decreasing and increasing pressure at the valve outlet 50c and thereby in the valve bore 55c can be used to respectively actuate the valve mechanism 65c into the open and closed configurations. In contrast, varying the pressure at the valve inlet 45c provides substantially comparable effects on the first and second piston members 80c′, 80c″, such that the valve mechanism 65c is not actuated by changes in the valve inlet 45c pressure alone, irrespective of the magnitude of the valve inlet pressure 45c.

[0134] When the pump is operated to pump fluid from the valve outlet 50c and thereby from the valve bore 55c, the drop in pressure in the valve bore 55c acting on the different sized faces 815, 810 of the first and second piston members 80c′, 80c″ results in a force on the first and second piston members 80c′, 80c″ that, once is it sufficient to overcome the biasing force applied by the biasing member 115, causes the valve mechanism 65c to actuate into the open configuration in which the first and second sealing surfaces 72c′, 72c″ move away from their respective valve seats 70c′, 70c″, to thereby open the valve bore 55c to through flow from the valve inlet 45c to the valve outlet 50c. Conversely, when the pump 20 operation is reduced to below a certain level or stopped when the valve mechanism 65c is in the open configuration, such that the negative pressure in the valve bore 55c acting differently on the first and second piston members 80c′, 80c″ is not sufficient to overcome the biasing force applied by the biasing member 115, then the valve mechanism 65c is actuated back into the closed configuration. A method of operating a pump drawdown activated valve, such as any of the valves 10, 10a, 10b shown in any of FIGS. 2 to 8, is illustrated with respect to FIG. 9.

[0135] If the valve 10 is closed and the operator wishes to open it, then in step 805, the pump 20 is started or controlled to increase its operation until the pressure differential from the annulus 105 to the valve outlet 50 that is in fluid communication with the pump inlet 60 is greater than a predetermined threshold required for the valve mechanism to move (which may be governed by the biasing member 115, friction between the valve mechanism 65 and the walls of the valve bore 55, and/or the like). In step 810 the differential pressure from the annulus 105/first chamber 90 to the second chamber 95/valve bore 55/pump inlet 60 acts on the piston member 80 so as to move the piston member 80 and thereby the valve mechanism 65 to open the valve 10 and compress the biasing member 115.

[0136] In the embodiment of FIGS. 2 to 4, this involves the sealing surface 72 of the valve mechanism 65a being moved away from the valve seat 70a so as to open the valve bore 55a and valve outlet 50a to the valve inlet 45a, thereby creating an open fluid flow path from the valve inlet 45a, through the valve bore 55a to the valve outlet 50a and pump inlet 60. In the embodiment of FIGS. 5 and 6, this involves the sliding sleeve 65b being moved towards the valve outlet 45b/pump 20 end of the valve 10b so as to move the open end 230 and thereby the bore 200 of the sliding sleeve 65b to be in fluid communication with the opening 215, feed passage 210 and valve inlet 45b, thereby creating a fluid communication path from the valve inlet 45b through the sliding sleeve 65b to the valve outlet 50b and pump inlet 60.

[0137] If the valve 10 is open and the operator wishes to close it, then in step 815, the pump 20 is switched off or controlled to reduce operation of the pump to at least below the threshold. As the differential pressure between the annulus 105 and the valve bore 55 and pump inlet 60 equalises and drops, the force applied to the piston 80 by the differential pressure between the first chamber 90 (which is equal to or at least depends on the annulus 105 pressure) and the second chamber 95 (which is equal to or at least dependent on the pressure in the valve bore 55 and/or pump inlet 60) also drops until it is less than the closing force applied by the biasing member 115 (accounting for friction and any other effects). In this case, the biasing member 115 acts to close the valve, in step 820.

[0138] In the embodiment of FIGS. 2 to 4, this involves the sealing surface 72 of the valve mechanism 65a being moved towards and into sealing engagement with the valve seat 70a by the biasing member 115 so as to close the valve bore 55a, thereby closing the path from the valve inlet 45a, through the valve bore 55a to the valve outlet 50a and pump inlet 60. In the embodiment of FIGS. 5 to 6, this involves the sliding sleeve 65b being moved away from the valve outlet 45b/pump 20 end of the valve 10b so as to seal the open end 230 and thereby the bore 200 of the sliding sleeve 65b from the opening 215, feed passage 210 and valve inlet 45b using the inlet seal 220, thereby preventing fluid communication from the valve inlet 45b to the valve outlet 50b and pump inlet 60.

[0139] In this way, the valve 10 is selectively and reversibly movable between open and closed configurations using the pump 20, regardless of a pressure differential between the valve inlet 45 and a valve outlet 50.

[0140] Although various exemplary features are described above, it will be appreciated that variations would be apparent to a skilled person from the teaching of the present application. As such, the scope of protection is defined by the claims and not by any of the specific examples given above, which are provided for illustration only.

[0141] An example of another alternative valve 10d is shown in FIGS. 10 to 19. The valve 10d is similar to that shown in FIGS. 2 to 4 and is operated according to a pressure differential between a valve outlet 50d that connects to a pump inlet (not shown) and an annulus around the outside of the valve 10d such that it is operable based on pressure differentials generated by the pump 20 (see FIG. 1). Like the valve 10a, the valve 10d also comprises a housing 35d, a valve inlet 45d and the valve outlet 50d connected by a valve bore 55d that is defined by the housing 35d of the valve 10d. The valve inlet 45d is configured for connection to the packer 15 bore (see FIG. 1) whilst the valve outlet 50d is configured for fluid connection to a pump inlet. In this way, when the valve 10d is in the open configuration, then fluid can pass from the bore in the packer 15, through the valve inlet 45d, the valve bore 55d and the valve outlet 50d to the pump 20. Thereafter, the fluid can be pumped by the pump 20 out from pump outlets into the annulus.

[0142] The valve 10d comprises a valve mechanism 65d, in this case in the form of a poppet, that is slidably located within the valve bore 55d. A valve seat 70d in the valve bore 55d is configured to engage a sealing surface 72d of the valve mechanism 65d (i.e. the poppet) when the valve 10d is in the closed configuration in order to limit the range of motion of the valve mechanism 65d and to seal the valve bore 55d closed. In this example, the valve mechanism 65d is a knife-edge valve in which the sealing surface 72d is a sharp, radiussed, arcuate or chamfered edge and the valve seat 70d is configured to receive the edge. For example, the valve seat 70d may be formed from a relatively soft material, which may be a polymeric material, such as PEEKor a ceramic filled PTFE, or the like. However, the valve seat 70a is not limited to polymeric material and could be, for example, a metal seat such as for a metal-to-metal seal or a ceramic seat, or the like. A biasing member 115d is provided to bias the valve mechanism 65d into the closed configuration in which the sealing surface 72d of the valve mechanism 65d seals against the valve seat 70d in order to close the valve bore 55d.

[0143] The valve mechanism 65d is provided with a plurality of integral piston members 80d, in this case in the form of radially protruding flanges. Alternatively, one piston member 80d could be used. A radially outer part of the piston members 80d is provided with a piston seal 87d that seals against an inner wall of the valve bore 55d. In this way, the outer wall of the valve mechanism 65d and the inner wall of the bore 55d define a chamber that is separated into a first chamber 90d and a second chamber 95d by the piston member 80d. The housing 35d is provided with suitably located through channels 100d between the first chamber 90d and the annulus 105d located radially outwardly of the housing 35d of the valve 10d. In this way, the first chamber 90d is in fluid communication with, and at the same pressure as, the annulus 105d. Again, rather than taking the specific form shown, the through channels 100d may be implemented using a control line or other conduit or mechanism to ensure that the first chamber 90d senses pressure in the annulus 105d. For example, if the valve is deployed at the bottom of a feedthrough packer, then a control line may extend between the first chambers 90d and a feedthrough of the feedthrough packer in order to sense pressure in the annulus 105d.

[0144] The second chamber 95d is provided with a through passage 110d that is in fluid communication with the pump inlet via the portion of the valve bore 55d that is closest to the valve outlet 50d. In this way, the second chamber 95d is at the same pressure as the pump inlet. This arrangement allows the valve 10d to be operated responsive to operation of the pump 20. In particular, when the pump 20 is operational, it will suck in fluid from the valve bore 55d via the pump inlet and expel the fluid via pump outlets into the annulus 105d. This causes a pressure drop at the pump inlet with respect to the pump outlets, which conversely experience an increase in pressure. This in turn creates a pressure differential between the pump inlet 60d (and thereby the valve outlet 50d, the portion of the valve bore 55d closest to the valve outlet 55d and the second chamber 95d) and the pump outlet (and thereby the annulus 105d and the first chamber 90d). As such, the piston member 80d experiences a pressure differential between the relatively high annulus 105d pressure on one side and the relatively lower valve bore 55d pressure and the force applied by the biasing member 115d on the other. When the pressure differential on the piston member 80a reaches a certain threshold, the piston member 80d and thereby the valve mechanism 65d are moved to compress the biasing member 115d. The sealing surface 72d of the valve mechanism 65d is also moved away from the valve seat 70d to thereby open the valve 10d and allow fluid flow from the valve inlet 45d through the valve bore 55d to the valve outlet 50d.

[0145] In this regard, the valve 10d operates in substantially the same way as the valve 10a shown in FIGS. 2 to 4. However, the valve 10d differs from that of FIGS. 2 to 4 in that it comprises a further operating mechanism 200d that allows bi-directional operation of the valve 10d, which may be particularly beneficial for testing.

[0146] The further operating mechanism comprises a shuttle sleeve 205d that supports a pair of unidirectional seals 210d, 215d, one at each end of the shuttle sleeve 205d. The unidirectional seals comprise a main seal 210d and a test seal 215d. Both seals 210d, 215d seal between the outer surface of the valve mechanism (poppet) 65d and an inner wall of the valve housing 35d. The main seal 210d receives fluid, and is exposed to pressure, from downhole via the valve inlet 45d and a passage 220d through the housing 35d. The unidirectional main seal 210d is arranged to restrict the well pressure from downhole. The test seal 215d is open to the valve bore 55d and thereby the valve outlet 50d so as to receive fluid, and be exposed to pressure, provided from uphole, particularly from the surface, e.g. through the pump 20 or via a separate pressure line. The unidirectional test seal 215d is arranged to resist the pressure from above, e.g. a test pressure provided from the surface.

[0147] The shuttle sleeve 205d is provided with a first loading shoulder 230d arranged to selectively engage a first loading surface 235d on an inner wall of the housing 35d to limit the range of motion of the shuttle sleeve 205d in one direction. The shuttle sleeve 205d is also provided with a second loading shoulder 240d arranged to selectively engage a second loading surface 245d on an outer surface of the valve mechanism (poppet) 65d to limit the range of motion of the shuttle sleeve 205d in an opposite direction. A biasing member 225d biases the shuttle sleeve 205d towards the uphole pressure side such that the first loading shoulder 230d of the shuttle sleeve 205d normally engages the first loading surface of the housing 35d unless forced otherwise. As shown particularly in FIG. 18, a seal diameter 252d of the valve mechanism (poppet) 65d, an effective diameter 250d of the main seal 210d and an effective diameter 255d of the test seal 215d are in a particular relationship in which the effective diameter 250d of the main seal 210d is slightly less than the seal diameter 252d of the valve mechanism 65d and the effective diameter 255d of the of the test seal 215d is slightly greater than the seal diameter 252d of the valve mechanism 65d. In this way, the valve 10d can be di-directional whilst the sealing of the valve mechanism 65d and valve seat 70d is always boosted, regardless of the which way the pressure differential acts over the shuttle sleeve 205d. As the seal diameter 252d of the valve mechanism (poppet) 65d, the effective diameter 350d of the main seal 210d and the effective diameter 355d of the test seal 215d are all close in size (albeit different, as indicated above), e.g. within 10%, then interference with operation of the main valve opening/closing mechanism responsive to operation of the pump 20 is minimised.

[0148] The operation of the valve 10d can be seen from FIGS. 12 to 17.

[0149] FIG. 12 shows a cross sectional view of the valve 10d in a closed configuration. In this case, the pump 20 (FIG. 1) is either not operational or at least not operational to a level sufficient to overcome the force applied by the biasing member 115d. In this case, the pressure in the annulus 105d and thus the first chamber 90d is less than the pressure in the valve bore 55d and second chamber 95d and the piston members 80d are biased towards the left in FIG. 12.

[0150] A detail cross sectional view of the further operating mechanism 200d in the closed configuration is shown in FIG. 13. In this case, no pressure is applied from the surface such that the wellbore pressure downhole of the valve 10d as seen at the valve inlet 45d and the main seal 210d via the through passage 220d in the housing is greater than the uphole pressure as seen by the test seal 215d via the valve bore 55d and valve outlet 50d. In this case, the wellbore pressure from downhole of the valve 10d acts across a differential piston area between the seal diameter 252d of the valve mechanism 65d (e.g. of the interface of the valve seat 70d against the sealing surface 72d) and the effective diameter 250d of the main seal 210d. As the seal diameter 252d of the valve mechanism 65d is greater than the effective diameter 250d of the main seal 210d, the valve mechanism 65d is forced such that the sealing surface 72d and the valve seat 70d are further forced together, thus boosting the seal. The shuttle sleeve 205d stays right in FIGS. 12 and 13 such that the first loading shoulder 240d is engaged with the first loading surface 245d due to the pressure from downhole via the through passage 220d and the biasing member 225d.

[0151] FIGS. 14 and 15 show cross sectional views of the valve 10d in an open configuration. In this case, the pump 20 (FIG. 1) is operating such that the pressure in the valve bore 55b and thereby the second chamber 95d is reduced by the pump via the valve outlet 50d and the pressure in the annulus 105d and thereby the first chamber 90d is increased relative to the situation shown in FIGS. 12 and 13. In this case, the pressure differential created by operation of the pump 20 causes the piston members 80d to move right in FIG. 14 to overcome the biasing member 155d and move the valve mechanism (poppet) 65d and the sealing surface 72d of the valve mechanism 65d off the valve seat 70d to open the valve 10d. However, in this case, the shuttle sleeve 205d remains right in FIGS. 14 and 15 such that the first loading shoulder 240d is engaged with the first loading surface 245d due to the pressure from downhole via the through passage 220d and the action of the biasing member 225d.

[0152] FIGS. 16 and 17 show cross sectional views of the valve 10d in a test configuration in which the shuttle sleeve 205d is moved, thereby opening the valve 10d to reverse flow from the uphole side (outlet 50d) to the downhole side (the inlet 45d). In this case, an uphole pressure has been applied from the surface or other uphole location down to the valve outlet 50d, and thereby to the valve bore 55d and the test seal 215d. The uphole pressure that was applied acts across a differential piston area between the seal diameter 252 of the valve mechanism 65d and the effective diameter 255d of the test seal 215d. As the effective diameter 255d of the test seal 215d is larger than the seal diameter 252 of the valve mechanism 65d, this acts to boost the sealing of the sealing surface 72d of the valve mechanism 65d against the valve seat 70d whilst at the same time operating the shuttle sleeve 205d to the left as shown in FIGS. 16 and 17 so that the second loading shoulder 245d is pushed towards and eventually engages with the second loading surface of the valve mechanism 65d. The effect of this is to open the valve 10d up to reverse flow whilst further boosting the seal of the valve seat 70d and sealing surface 72d.

[0153] The arrangement described above may provide certain benefits. The valve can be made selectively bi-directional, whilst the sealing of the valve mechanism 65d is boosted regardless of the direction of the pressure differential across the shuttle sleeve 205d. This arrangement also minimises the number of seals required, there is no trapped pressure between the main seal 210d and test seal 215d and volume change is reduced or minimised due to the moving shuttle sleeve 205d The shuttle sleeve 205d allows the main seal 210d and test seal 215d themselves to load out onto one of the loading surfaces 240d, 250d and also means that low friction dynamic seals. 210d, 215d can be used. The particular design of the shuttle sleeve 205 allows the possibility of adjusting the biasing force due to pressure independent of the seal 210d, 215d minimum wall section, or can adjust it to be different in each direction. This arrangement allows the valve 10d to be testable from the surface or to act as a bi-directional valve such as a fluid loss valve, a barrier valve, or the like.

[0154] Beneficially a pressure operated valve opening mechanism 260d such as a burst disc, plug with O-ring seal, or ball seat, or plug with shear screws, a shear ring, a detent ring or a detent spring or the like could be used. The pressure operated valve opening mechanism 260d is operable under pressure differential applied from uphole, e.g. from the surface, to rupture or shear the opening mechanism 260d to allow access through the valve 10d, as shown in FIG. 19.

[0155] For example, although examples of valve mechanisms that comprise a poppet valve and a sliding sleeve valve are given above, it will be appreciated that other valve types such as flapper valves, ball valves and the like could be used. Furthermore, although various mechanisms for resisting, preventing or desensitizing the valve to operation by a valve inlet to valve outlet pressure differential or simply being such that the valve is unaffected by the valve inlet to valve outlet pressure differential (rather than a pressure differential caused by the operation of the pump, such as an annulus to valve bore/valve outlet/pump inlet pressure differential) are described above, it will be appreciated that other suitable mechanisms could be used and may be apparent from the present disclosure. As the apparatus functions by the creation of a differential pressure at a set depth, this can be used advantageously in any system whereby a pressure differential between the inside of the conduit and production tubing exists during operation. Alternatively, in the case of rod lift or PCP systems, a differential pressure can be exerted during the mechanical action of the solid rods by rotation and/or lifting.

[0156] Furthermore, although some of the examples described above comprise a single piston member 80a, 80b, 80c, the valve 10 could instead be provided by a plurality of piston members. In this case, each piston member could be provided between respective or common first chambers 90 and second chambers 95, such that each piston member experiences the pressure differential between the annulus 105 pressure and the combination of the valve bore 55a pressure and force applied by the biasing member 115. In this way, the combined force applied on the piston members due to the pressure differential and thereby on the valve mechanism in opposition to the force applied by the biasing member 115 can be made greater than that applied by a single piston member.

[0157] In addition, whilst various sealing mechanisms are described, such as O-rings, other sealing mechanisms could be used, such as rolling membranes, bellows, concertina seals and/or the like.

[0158] As such, while certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the invention. Indeed the novel methods and systems described herein may be embodied in a variety of other forms. Furthermore, various omissions, substitutions and changes in the form of the methods and systems described herein may be made without departing from the spirit of the invention. The accompanying claims and their equivalents are intended to cover such forms and modifications as would fall within the scope of the invention.