WO2001012949A2

WO2001012949A2 - Downhole flapper valve assembly

Info

Publication number: WO2001012949A2
Application number: PCT/GB2000/003200
Authority: WO
Inventors: Clive John French
Original assignee: French Oilfield Services Limited
Priority date: 1999-08-17
Filing date: 2000-08-17
Publication date: 2001-02-22
Also published as: EP1144803A2; GB9919270D0; WO2001012949A3; EP1144803A3; AU6707800A

Abstract

A tool assembly is disclosed which, in a preferred embodiment, is an isolation valve (10). The valve (10) is configurable in closed and open configurations and allows, for example, pressure testing of tubing above the valve (10) and isolation of upper and lower sections of the tubing. The valve (10) generally includes a concave valve flap (12), tubular housing (14), upper sleeve (16), annular seal assembly (18), first and second lower sleeves (20, 22) and a lower sleeve locking assembly (24). The valve flap (12) is movable from a closed configuration, where it lies substantially perpendicular to the housing (14), to an open configuration, where it lies in a recess (84) in the housing (14). This is achieved by supplying hydraulic control fluid through control conduits (17, 19) to move the sleeves (16, 20, 22) and displace the flap (12) into the recess (84), which is uncovered by the lower sleeves (20, 22).

Description

TOOL ASSEMBLY

The present invention relates to a tool assembly. In particular, but not exclusively, the present invention relates to a tool assembly including a hydraulically operated downhole tool such as a valve assembly. When it is desired to carry out work on a partially cased or fully cased borehole of an oil or gas well there is a requirement for an isolation barrier to be provided, typically a valve or weighted fluid. Furthermore, when tubing is installed on a production well, Health and Safety regulations require that a barrier is installed as a part of the completion.

The operation of existing hydraulically actuated tools, such as isolation valves of the ball valve type, is typically controlled by a combination of a hydraulic control line and one or more return springs. The ball valve may be disposed in a length of tubing such as a section of a borehole liner, and may be actuated to an open configuration to allow fluid flow through the liner, by pressurising a control fluid in a control line coupled to the ball valve carriage. The ball valve may be actuated to a closed configuration, preventing fluid flow through the liner, by reducing the pressure of the control fluid in the control line. This causes the return spring, which is compressed when the ball valve is opened, to act upon the ball valve carriage, thereby rotating the ball valve to the closed configuration.

However, such assemblies comprise a relatively large number of mechanical components and moving parts, increasing the risk of failure.

Other valves may be bore-pressure actuated, however the requirement for the valves to remain closed during, for example, completion testing, when the valve will experience elevated bore pressures, and to open only after testing is completed, requires provision of relatively complex arrangements and typically requires provision of a number of seals in the tubing above the valve, which seals may experience relatively high differential pressures, with the attendant risk of failure and leakage.

It is amongst the objects of the present invention to obviate or mitigate at least one of the foregoing disadvantages .

According to a first aspect of the present invention, there is provided a tool assembly comprising: a hydraulically actuated downhole tool for disposition in a borehole of a well, the tool being configurable in at least a first and a second tool configuration; a first hydraulic control conduit coupled to the tool, for selectively supplying a control fluid to the tool to maintain the tool in said first tool configuration; a second hydraulic control conduit coupled to the tool, for selectively supplying control fluid to the tool for actuating the tool to the second tool configuration; and control means for controlling the supply of control fluid to the tool via the hydraulic control conduits, to control actuation of the tool between said first and second tool configurations .

According to a second aspect of the present invention, there is provided a downhole tool assembly for disposition in a borehole of a well, the tool comprising; a hydraulically actuated tool configurable in at least a first and a second tool configuration; a first hydraulic control conduit coupled to the tool, for selectively allowing the supply of a control fluid to the tool, to allow the tool to be maintained in said first tool configuration; and a second hydraulic control conduit coupled to the tool, for selectively allowing the supply of control fluid to the tool, to allow actuation of the tool to the second tool configuration.

Thus the present invention may allow control of the actuation of a downhole tool between two or more tool configurations by selectively supplying a control fluid to the tool assembly via a selected one of the control conduits . The control fluid may be supplied via control conduits connected to surface. Alternatively, the control fluid may be supplied via control conduits connected to a control device adapted to be located downhole, where control fluid is adapted to be supplied from the control device in response to fluid pressure pulses within the borehole. Such pressure pulses may be main or annulus pressure pulses; such a control device is disclosed in co- pending United Kingdom Patent Application No. 0014409.7 and United States Patent Application No. 09\591,743. The control device may typically be located above or below a packer; where located below a packer, the device may be activated by annulus pressure; application of tubing pressure may result in the supply of control fluid via the second control conduit . The control fluid may be hydraulic fluid. The use of hydraulic control fluid supplied, for example, from surface to maintain the tool in the first configuration and to actuate the tool from the first to the second position obviates the requirement to provide heavy locking or retaining arrangements, such as return springs and shear couplings. Further, the independence of operation from bore or annulus pressure reduces the complexity of the sealing arrangements which must be provided. Further advantageously, in drilling or completion workover phases, the assembly can be run in hole and set on wireline as part of a packer or plug assembly. This provides an additional barrier which can be run as part of a tubing, casing string or liner and may be employed to assist in well control in the event of a "kick", or used for formation isolation. In the event that an unexpectedly high pressure formation is encountered, this creates a "kick" in the bore, which may result in a sudden influx of formation fluid into the bore, with potentially disastrous consequences .

Preferably, the downhole tool is an isolation valve, such as a downhole safety valve. The valve may be a flap or disk type valve. The valve may be generally circular in plan and arcuate in cross-section. Alternatively, the valve may be a ball type valve. In other embodiments, the downhole tool may be a circulation or bypass valve or a system of valves, an annulus isolation unit such as an inflatable packer, a gun system, and/or any other hydraulically operable tool. For brevity and ease of understanding, reference will be made primarily herein to a tool in the form of an isolation valve though it will be understood by those of skill in the art that the various preferred features of the invention may have equal utility in other tool forms .

The assembly may advantageously be used in any high or standard temperature well . A string carrying the assembly may be run into a borehole with the valve in a closed position, and when the valve has been used to carry out its desired function, the valve may be moved to the open position to open the assembly up to full bore diameter. Typically, the valve is run into a completion tubing on the base of a packer or a wireline set lock mandrel, and may be used as a downhole safety valve or in a method of testing the tubing. The valve may be able to be cycled open when required. In alternatives, the valve may be run on completion tubing, casing, drill pipe or the like and may be tested against to determine pressure integrity of the tubing, casing, drill pipe or the like.

Conveniently, in the first tool configuration, the tool is in a closed or deactivated configuration, and in the second tool configuration, the tool is in an open or activated configuration. The tool may be disposed in one or more other tool configurations intermediate the first and second tool configurations. The valve may be run in and located at depth at a packer or below a packer in the case of a completion being run. The valve may be used to assist in the running of a completion to set a packer, test well tubing, and once finished may be moved to the open configuration and isolated. If a completion is to be pulled, the valve may advantageously be run in on a wireline in the closed configuration, and the well isolated, following which the completion may be pulled and replaced above the valve. Once the completion has be rerun and tested, the valve may be moved to the open configuration to allow fluid flow. This advantageously avoids the requirement of making a wireline run to pull, for example, a conventional plug. It will be understood that references herein to a "completion" are to production tubing and associated apparatus run into a casing lined borehole for recovery of well fluids and conducting associated operations.

The tool assembly may form part of or be mounted to a string of tubular members. Conveniently, the tubular members may be casing, lining, production tubing, drill tubing or other tubing to be run into a borehole; for brevity, reference will be made hereinafter to tubing. Where the tool is in the form of an isolation valve, in the first tool configuration, the valve may be closed and sealed to prevent fluid flow through the tubing. This may therefore advantageously allow the valve to hold fluid pressure from both above and below the valve. In the second tool configuration, the valve may be open to allow fluid flow through the tubing. The isolation valve may be maintained in the closed and sealed configuration by maintaining the pressure of control fluid in the first hydraulic control conduit substantially constant, or at least above a predetermined level. The isolation valve may be actuated to the open configuration by supplying fluid to the tool assembly via the second hydraulic control conduit. If necessary, fluid may bleed from the tool assembly via the first hydraulic control conduit. This arrangement permits precise control of the valve operation.

The tool assembly may comprise at least two axially movable sleeves disposed within the tubing. There may be an upper sleeve disposed above the valve member and a lower sleeve disposed below the valve member. Control fluid supplied to the tool assembly via the first control conduit may assist in maintaining the lower sleeve with an upper face in sealing contact with the valve member, and to maintain the valve in the closed configuration.

Supplying control fluid to the tool assembly via the second hydraulic control conduit may cauce the lower sleeve to move axially downwardly, clear of the valve member, and the upper sleeve to move axially downwardly towards the valve member, to displace the valve member to the second, open configuration. The lower sleeve may be adapted to move axially in response to a lower fluid pressure of the control fluid in the second hydraulic control conduit than the upper sleeve such that the lower sleeve is displaced axially downwardly before the upper sleeve is moved axially downwardly to displace the valve member to the open configuration.

Advantageously, as a failsafe mechanism, if pressure is not released from one side of the valve member through one of the control conduits at the same time as it is applied to the other side of the valve member through the other one of the control conduits, the tool will be locked and unable to function, that is unable to move between the first and second configurations . The assembly may further comprise a seal mechanism including a seal for sealing the valve in one of the first and second tool configurations. The seal mechanism may be for sealing a valve member of the valve, and may further comprise means for restraining the valve member against movement when in one of the first and second tool configurations, such that the seal only experiences a compressive load up to a predetermined level. This advantageously prevents the seal from experiencing a compressive load which may otherwise tend to flatten and thus permanently deform the seal.

The means for restraining the valve member may comprise a shoulder in a wall of the tool. Conveniently the seal is provided adjacent the shoulder such that the seal is protected from axial compressive loading exerted upon the valve member. Where the valve member comprises a flap or disk type valve member, the seal may be provided at a radial outer edge, preferably in a radial outer surface of the valve member, for sealing with a wall of the tool. Alternatively, the seal may be located in a wall of the tool, for sealing with a radial outer edge of the valve member. It will be appreciated that the seal mechanism may equally have uses with alternative types of valves other than flap or disk type valves.

Preferably, the tool assembly comprises two lower interconnected sleeves. The sleeve spaced from the valve member is preferably lockable relative to the tubing, while the sleeve adjacent the valve floats, and may be urged into sealing contact with the valve member by fluid supplied to the tool via the first hydraulic control conduit.

The assembly may further comprise a tubular housing defining an internal bore in which the sleeves and the valve member are mounted. The housing may include a recess in an internal wall thereof into which the valve member may be disposed when in the open configuration. Preferably also, the upper sleeve retains the valve member in said recess. Alternatively, the housing may include a cavity in which the valve member may be disposed when in the open configuration, and may be isolated from well-bore fluids and debris therein. This structure may be provided where the valve member is not required to provide pressure integrity, when in the closed configuration, below the valve member. This may advantageously allow the valve member to be disposed, in the closed configuration, in the cavity, providing a greater internal diameter for the housing than when located in a recess, thus not reducing the housing internal diameter for passage of tools, flow of fluids and the like.

The first and second hydraulic control conduits may extend from the tool assembly and out of the borehole, and may be coupled to a hydraulic control fluid supply means on the surface for supplying control fluid to the assembly. The hydraulic control fluid supply means may form part of the control means . The control means may further comprise means for monitoring the pressure of control fluid in the hydraulic control conduits and means for measuring the volume of control fluid supplied to or bled from the assembly via the selected one of the first and second control conduits. Conveniently, the control means further comprises a computer or other electronic means for monitoring the control fluid pressures and the volume of control fluid supplied such that the operating configuration of the assembly may be controlled and monitored.

Preferably, the assembly further comprises a bypass vent which is selectively openable to permit flow between the interior and exterior of the assembly on opening and closing of the valve member, to provide a fluid path around the valve member. Thus, as the valve member is opened or closed, fluid pressure or flow may bypass the valve member. The valve member and a valve seat formed by the upper face of the lower sleeve thus do not experience the wear and erosion that would otherwise occur when the valve member was only partially open and which would impair the ability of the valve member to create an effective seal. The vent may be provided as part of a circulation sub located above the tool, said vent being selectively closable.

According to a third aspect of the present invention, there is provided a valve assembly for location in a borehole of a well, the assembly comprising: a hollow elongate member for location in the borehole; a valve adapted to be run into the hollow elongate member in a closed position and then moved to an open position; a first hydraulic control conduit for holding the valve in the closed position by application of a first control fluid to a closing and locking mechanism of the assembly; and a second hydraulic control conduit for actuating the valve to the open position, by application of a second control fluid to the closing and locking mechanism.

The hollow elongate member typically comprises a tubular member and the valve assembly may form part of or be mounted to a string of such tubular members, which may be casing, lining, production tubing, drill tubing or the like.

Conveniently, the closing and locking mechanism includes at least two axially movable sleeves disposed within the tubing. There may be an upper sleeve disposed above the valve and a lower sleeve disposed below the valve. Control fluid supplied to the valve via the first control conduit may assist in maintaining the lower sleeve with an upper face in sealing contact with the valve member, and to maintain the valve in the closed position. Further features of the at least two axially movable sleeves are defined above with reference to the first and second aspects of the present invention.

According to a fourth aspect of the present invention, there is provided a method of controlling the operation of a tool assembly, the method comprising the steps of: disposing a hydraulically actuated downhole tool in a borehole of a well; coupling first and second hydraulic control conduits to the tool; supplying fluid to the tool via said first hydraulic control conduit, to maintain the tool in a first tool configuration; and supplying fluid to the tool via said second hydraulic control conduit, to actuate the tool to a second tool configuration. According to a fifth aspect of the present invention, there is provided a valve assembly for location in a borehole of a well, the valve assembly comprising: a hydraulically actuated valve movable between at least closed and open configurations; a first hydraulic control conduit coupled to the valve, for selectively supplying control fluid to the valve to maintain the valve in the closed configuration; a second hydraulic control conduit coupled to the valve for selectively supplying control fluid to the valve for moving the valve to the open configuration; a seal mechanism for sealing the valve in the closed configuration, the seal mechanism including a seal for sealing with the valve and means for restraining the valve against movement when in the closed configuration, such that the seal only experiences a compressive load up to a predetermined level.

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

Figure 1A is a schematic illustration of a tool assembly in the form of an isolation valve, in accordance with a preferred embodiment of the present invention, run on a string of tubular members including a ported circulation sub, and coupled to control means comprising one of a computer located at surface and a downhole control device;

Figure IB is a more detailed, diagrammatic longitudinal cross-sectional view of the isolation valve of Figure 1A shown in a first tool configuration where the isolation valve is in a closed configuration; Figures 2A - 2E are longitudinal half-sectional views of parts of the tool assembly of Figure IB (Figures 2B-2E being shown enlarged) ;

Figure 3 is a view of the tool assembly of Figure IB in a second tool configuration, where the isolation valve is in an open configuration; Figure 4 is a view of part of a tool assembly in accordance with an alternative embodiment of the present invention, shown in an open configuration, with a valve flap or disk of the assembly disposed in a cavity in a wall of the assembly; Figure 5 is a schematic cross-sectional view of a tool assembly in accordance with a further alternative embodiment of the present invention, with an offset bore and a valve flap or disk located in a recess offset from the bore; Figures 6A and 6B are schematic longitudinal cross- sectional views of an alternative valve flap or disk for the tool assembly of Figure IB, shown in closed and open configurations, respectively;

Figures 7A and 7B are views of a further alternative flap or disk similar to that shown in Figures 6A and 6B.

Referring firstly to Figure 1A, there is shown a tool assembly in the form of an isolation valve in accordance with a preferred embodiment of the present invention, indicated generally by reference numeral 10. The isolation valve 10 is shown where it has been run-into a borehole of an oil or gas well (not shown) as part of a string 11 of tubular members, such as a completion string including production tubing (not shown) . The isolation valve 10 will be discussed in more detail below; however, to explain briefly, the valve 10 is configurable in first and second tool configurations, in particular, closed and open configurations. Actuation of the valve 10 between these configurations is controlled by control means in the form of either a computer 13 at surface, or a downhole control device 15 forming part of the string 11. A suitable downhole control device 15 is disclosed in co-pending UK Patent Application No. 0014409.7. The control device 15 is actuatable, for example, by tubing or annulus fluid pressure cycles, to supply tool control fluid to the valve 10 through first and second hydraulic control conduits 17 and 19, and is advantageous in that this avoids running control conduits to surface. Operation of the control device 15 can be controlled by the computer 13. Alternatively, the control conduits 17, 19 extend to surface (as shown in broken outline) and the computer 15 directly controls supply of control fluid to the valve 10.

Referring now also to Figure IB, the isolation valve

10 of Figure 1A is shown in more detail. The isolation valve 10 includes a concave flap or disk 12, which in

Figure IB is shown in a closed configuration. The valve 10 forms part of the tubing string 11 run into the borehole of an oil or gas well and allows, for example, pressure testing of the tubing above the valve 10, and isolation of upper and lower sections of the tubing as will be described in more detail below.

The valve 10 includes a tubular housing 14, forming part of the tubing string and coupled at its upper and lower ends to sequential sections of the string 11 via screw-threaded joints, as will be understood by persons skilled in the art. In particular, as shown in Figure 1A, the valve 10 is coupled at its upper end to a ported circulation sub 21, used to equalise pressure across the valve 10 during movement between the first and second tool configurations. To achieve this, the sub 21, of a kind known in the art, includes ports 23 extending through a wall of the sub 21, which ports 23 can be selectively opened to allow pressure equalisation between the interior of valve 10 and an annulus defined between the borehole and the string 11, as will be described in more detail below. The valve assembly 10 further comprises an upper sleeve 16, an annular seal assembly 18, a first lower sleeve 20, a second lower sleeve 22 and a lower sleeve locking assembly 24.

The tubular housing 14 has an irregular internal profile defining a through-bore 26. Each of the upper sleeve 16, seal assembly 18, first lower sleeve 20, second lower sleeve 22 and the sleeve locking assembly 24 are disposed sequentially along the through-bore 26 of the housing 14 and are in sealing contact with the inner wall of the housing 14 defining the through-bore 26, as will be described in more detail below. The sleeves 16, 20 and 22 together define a substantially constant diameter axial passage 28 through which fluid flow may be selectively permitted.

The valve assembly 10 is run into the borehole on the tubing string 11 with the valve flap 12 in the closed configuration, as shown in Figure IB. This prevents fluid flow through the internal passage 28 of the assembly 10 and allows for, for example, pressure testing of the tubing above the valve. The control lines 17, 19 are coupled to the assembly 10 to allow for control of the operation of the assembly 10. The first control line 17 is coupled to the assembly 10 and has an outlet at point 36. The second control line 19 is coupled to the assembly and has outlets at points 30, 32 and 34, spaced axially along the length of the housing 14. Actuation of the valve flap 12 between the closed configuration of Figure IB and an open configuration, as shown in Figure 3, is achieved by selective supply of a control fluid to the assembly 10, as will be described in more detail below.

Referring now also to Figures 2A - 2E, there are shown longitudinal half-sectional views of parts of the assembly 10 described above. Referring initially to Figure 2A, there is shown the housing 14, upper sleeve 16, annular seal assembly 18, valve flap 12, first lower sleeve 20 and the second lower sleeve 22. The valve flap 12 is maintained in the closed configuration as shown by an interaction between the annular seal assembly 18 and the first and second lower sleeves 20 and 22. The annular seal assembly 18 comprises a floating annular seal body 38, best shown in Figures IB and 2C, and first and second O-ring type elastomeric seals 40 and 42, disposed in the seal body 38. The seal 40 is in sealing contact with the wall of the housing 14, whilst the seal 42 is in sealing contact with the valve flap 12.

The first lower sleeve 20, best shown in Figure IB, includes an O-ring type elastomeric seal 44 disposed in an upper face thereof which, with the valve in the closed configuration, is in sealing contact with a lower face of the valve flap 12. Another O-ring seal 45 is provided between the sleeve 20 and the wall of the housing 14, with a further seal 47 being provided between the sleeves 20, 22 and the body 14 below the first control conduit outlet 36, and initially below the connection between the first and second sleeves 20, 22.

The upper sleeve 16 is shown in Figure 2B, and comprises a sleeve body 46 having an annular shoulder 48 extending radially therefrom, with an O-ring type elastomeric seal 50 disposed therein, providing sealing between the sleeve 16 and the housing 14. A further, smaller diameter seal 51 is provided between the sleeve body 46 and the housing 14, above the control line outlet 30. A snap ring 52 is provided on the housing 14 for engaging a recess 54 extending circumferentially around an upper end of the sleeve body 46, for locking the sleeve 16 in the extended position shown in Figure 3 and described below. Also, a coil spring 56 (shown in Figures IB and 2A) is disposed in a recess 58 in the wall of the housing 14 and acts upon a lower surface of the shoulder 48 of the sleeve body 46. The spring 56 maintains the sleeve 16 in the retracted position shown in Figure IB until such time as hydraulic fluid is supplied to the assembly 10 via the second control conduit .

Figure 2D illustrates the interaction between the first lower sleeve 20 and the second lower sleeve 22. The second sleeve 22 includes an engaging arm 60, L-shaped in cross-section, which extends from an upper end thereof and engages a corresponding arm 62 formed on a lower end of the first sleeve 20. An O-ring type elastomeric seal 64 is disposed therebetween to provide sealing between the sleeves 20 and 22. The engaging arms 60 and 62 ensure that the sleeves 20 and 22 move co-axially downwardly when the second sleeve 22 is retracted, while permitting the first sleeve 20 to float relative to the second sleeve. The sleeve locking assembly 24 is shown in Figure 2D and comprises an annular snap ring 66, which initially maintains the sleeve 22 in an axially fixed position, and a snap ring retainer 68 having an O-ring type elastomeric seal 70, to seal the retainer 68 relative to the housing 14. The snap ring 66 is disengagable from the housing 14 to allow axial movement of the sleeve 22 by the supply of control fluid to the outlet 32, which causes the snap ring retainer 68 to move axially downwardly, releasing the snap ring 66.

Figure 2E shows the tapered lower end 72 of the second lower sleeve 22 and the control fluid supply point 34, in communication with piston area 74 defined by the sleeve 22, and located between seals 76, 78.

The valve flap 12 is maintained in the closed, sealed configuration shown in Figure IB by the snap ring 66 and by the supply of control fluid via the first control line 17 to the outlet 36, at a substantially constant pressure of lOOOpsig. The control fluid acts on the piston area defined between the seals 45 and 64 to provide a pressure force axially upwardly upon the first lower sleeve 20, urging the seal 44 into sealing contact with valve flap 12 and urging the flap 12 towards the sleeve assembly 18.

When it is desired to open the valve flap 12 to allow fluid communication through the internal passage 28, pressure between the passage 28 above valve flap 12 and the borehole annulus is first equalised by opening ports 23 of sub 21. Control fluid is then supplied via the second control line 19 to the outlets 30, 32 and 34. Simultaneously, control fluid is allowed to bleed, still at a pressure of lOOOpsig, from the outlet 36 via the first control line 17, if required. When the pressure of the fluid in the second control line 19 reaches approximately 500psig, the locking assembly 24 is released, as described above, allowing the second lower sleeve 22 to move axially downwardly under the influence of the pressure force produced by fluid from the outlet 34 acting on the relatively large piston area between the seals 76, 78, carrying the first lower sleeve 20 therewith. When the first lower sleeve 20 has been carried to the retracted configuration as shown in Figure 3 , a recess 84 in the wall of the housing 14 is uncovered in which the valve flap 12 may be disposed. The pressure of the control fluid in the second control line 19 is increased to approximately 2000psig, at which point the pressure force acting between the seals 50, 51 is sufficient to move the upper sleeve 16 axially downwardly, compressing the spring 56 to the position shown in Figure 3. This downward axial movement of the upper sleeve 16 rotates the valve flap 12 about its hinge 58 and into the recess 84, allowing fluid communication through the passage 28. When the upper sleeve 16 has moved to this position, the snap ring 52 engages the recess 54 as shown in Figure 2B, to lock the upper sleeve 16 and the valve flap 12 in the open configuration. In this configuration the assembly 10 provides an unrestricted full-bore passage 28, through which well fluid or well apparatus may pass unobstructed. Turning now to Figure 4, there is shown part of a tool assembly in accordance with an alternative embodiment of the present invention, in the form of an isolation valve indicated generally by reference numeral 10a. Like components of the valve 10a with valve 10 of Figures 1A to 3 share the same reference numerals with the addition of the letter 'a'. For brevity only the differences between the valves 10, 10a will be described.

The valve 10a includes a concave valve flap or disk 12a, however, the flap 12a is, in the open configuration shown, located in a cavity 86 in the wall of the tubular housing 14a. The cavity 86 extends part-way around the circumference of the housing 14a, and allows full bore access through the bore 28a of the valve 10a, for tool access and non-restricted fluid flow. It will be understood that this arrangement may be used where it is not required to obtain pressure integrity below the valve flap 12a, when in the closed configuration. Such may occur when, for example, the valve 10a is open at a lower end to the wellbore.

Figure 5 is a schematic cross-sectional view of a tool assembly in the form of an isolation valve 10b, similar to the valve 10 of Figures 1A to 3. Like components share the same reference numerals with the addition of the letter

¹ b¹. The valve 10b differs in that the bore 28b is offset, again for the purpose of providing full bore access. A valve flap 12b is located, in the open configuration, in a part circumferential recess 88.

Referring now to Figures 6A and 6B and 7A and 7B, there are shown schematic longitudinal cross-sectional views of alternative valve flaps or disks 12c and 12d, respectively, shown in closed configurations in Figures 6A and 7A, and open configurations in Figures 6B and 7B. Seal mechanisms are provided which protect seals of the valves from damage, as will be described below. Like components with the valve flap 12 and valve 10 of Figures 1A to 2 share the same reference numerals with the addition of the letters 'c' and 'd', respectively.

The valve flap 12c is disposed, in the closed configuration, against a shoulder 90 in the wall of housing 14c, and carries an O-ring type elastomeric seal 92, for sealing with the housing wall 94. In a similar fashion, valve flap 12d seals to a wall 94d of housing 14d by an 0- ring type elastomeric seal 92d in the housing wall 94d.

Location of the seals 92 and 92d in this fashion protects the seals from axial compressive loading exerted upon the flaps 12c and 12d which would otherwise tend to flatten the seals. In this fashion, the seals 92 and 92d experience loading only up to a predetermined level, exerted thereon by the flaps 12c and 12d when in the closed configuration, to allow the seals 92 and 92d to be located as shown.

While the seals of the valve flaps 12c and 12d are protected as described, it will be appreciated that the principle may equally be employed with valves of types other than flap or disk type valves.

Various modifications may be made to the foregoing within the scope of the present invention. For example, the isolation valve may be a ball type valve. The downhole tool may be an alternative valve type such as a circulation valve or a system of valves, or may comprise a tool such as an annulus isolation unit (for example, an inflatable packer) , a gun system, or any other hydraulically activated tool. The tool assembly may form part of a lining or other tubing string run into a borehole. A plurality of such tool assemblies may be provided spaced along a casing, lining or other tubing string to allow, for example, sequential isolation of successive sections of the casing, lining or tubing string.

Advantages of the present invention include the following: a deep-set valve assembly may be provided run on tubing, liner, or casing that can be isolated as close to a formation as possible and opened or closed from surface by the application of hydraulic pressure. A valve assembly may be provided that can be operated by the use of control line from surface to open the valve. A valve assembly may be provided that is operated using hydraulic chambers acting against each other, sequenced by piston areas to control a set sequence of operations in the valve. A valve assembly may be provided that can be coupled to other devices to allow it to operate in different positions in a tubing, drilling or casing string, but still maintaining its method of operation. A valve assembly may be provided that can, by use of a hydraulic control unit and hydraulic control lines, be operated by the application of annulus pressure. A valve assembly may be provided that can set a closure disk or plate into the body of a valve increasing the bore size of the tool . A valve assembly may be provided that can be operated below a packer via a sensor above the packer and hydraulic lines run through the packer via a hydraulic control unit, such as a control device disclosed in co-pending UK Patent Application No. 0014409.7. A valve assembly may be provided that uses a vent to remove pressure and velocity surges through the tool at the moment of closure. A valve assembly may be provided that uses both applied hydraulic pressure and internal hydraulic pressure to maintain the valve in an open or closed position, locking the position of the valve. A valve assembly may be provided that maintains the maximum bore possible by reducing the number of moving parts . A valve assembly may be provided that has a plate that can be moved sequentially from the open position to the closed position as many times as possible. A disk or plate may be provided that can slide back inside the tool attached to a moving sleeve or remain pinned in position and rotated out by a torsion spring or driven back by a sleeve. A disk or plate may be provided that has a seat that has two sleeves, an upper and a lower, that move away sequentially through use of different piston sizes to allow the plate to be isolated. A valve assembly may be provided that has a lower and upper seat that once the plate is isolated can seal and prevent the ingress of debris.

Claims

1. A tool assembly comprising: a hydraulically actuated downhole tool for disposition in a borehole of a well, the tool being configurable in at least a first and a second tool configuration; a first hydraulic control conduit coupled to the tool, for selectively supplying a control fluid to the tool to maintain the tool in said first tool configuration; a second hydraulic control conduit coupled to the tool, for selectively supplying control fluid to the tool for actuating the tool to the second tool configuration; and control means for controlling the supply of control fluid to the tool via the hydraulic control conduits, to control actuation of the tool between said first and second tool configurations .

2. A downhole tool assembly for disposition in a borehole of a well, the tool comprising; a hydraulically actuated tool configurable in at least a first and a second tool configuration; a first hydraulic control conduit coupled to the tool, for selectively allowing the supply of a control fluid to the tool, to allow the tool to be maintained in said first tool configuration; and a second hydraulic control conduit coupled to the tool, for selectively allowing the supply of control fluid to the tool, to allow actuation of the tool to the second tool configuration.

3. An assembly as claimed in either of claims 1 or 2, wherein the control conduits are connected to surface.

4. An assembly as claimed in either of claims 1 or 2, wherein the control conduits are connected to a control device adapted to be located downhole, where control fluid is supplied from the control device in response to fluid pressure pulses within the borehole.

5. An assembly as claimed in any preceding claim, wherein the assembly forms part of or is mounted to a string of tubular members .

6. An assembly as claimed in any preceding claim, wherein in the first tool configuration, the tool is in a closed or deactivated configuration, and in the second tool configuration, the tool is in an open or activated configuration.

7. An assembly as claimed in any preceding claim, wherein the tool is adapted to be disposed in one or more other tool configurations intermediate the first and second tool configurations .

8. An assembly as claimed in any preceding claim, wherein the downhole tool is an isolation valve.

9. An assembly as claimed in claim 8, wherein the assembly further comprises a seal mechanism including a seal for sealing the valve in one of the first and second tool configurations.

10. An assembly as claimed in claim 9, wherein the seal mechanism is for sealing a valve member of the valve, and wherein the seal mechanism further comprises means for restraining the valve member against movement when in one of the first and second tool configurations, such that the seal only experiences a compressive load up to a predetermined level .

11. An assembly as claimed in claim 10, wherein the means for restraining the valve member comprises a shoulder in a wall of the tool.

12. An assembly as claimed in claim 12, wherein the seal is provided adjacent the shoulder such that the seal is protected from axial compressive loading exerted upon the valve member.

13. An assembly as claimed in any one of claims 8 to 12, wherein the valve includes a valve member comprising a flap or disk type valve member.

14. An assembly as claimed in claim 13 , wherein the seal is provided at a radial outer edge of the valve member, for sealing with a wall of the tool.

15. An assembly as claimed in claim 14, wherein the seal is located in a radial outer surface of the valve member.

16. An assembly as claimed in claim 13, wherein the seal is located in a wall of the tool, for sealing with a radial outer edge of the valve member .

17. An assembly as claimed in any one of claims 13 to 16, wherein the valve member is generally circular in plan and arcuate in cross-section.

18. An assembly as claimed in any one of claims 8 to 17, wherein the assembly is run into a borehole on a string carrying the assembly, with the valve in a closed position.

19. An assembly as claimed in any one of claims 8 to 18, wherein the valve is adapted to be tested against to determine pressure integrity of tubing on which the assembly is run.

20. An assembly as claimed in any one of claims 8 to 19, wherein the assembly is adapted to be run into a completion in a borehole on a wireline in the closed configuration, to allow the well to be isolated, following which the completion is pulled and replaced above the valve.

21. An assembly as claimed in any one of claims 8 to 20, wherein the isolation valve is adapted to be maintained in a closed and sealed configuration by maintaining the pressure of control fluid in the first hydraulic control conduit substantially constant.

22. An assembly as claimed in any one of claims 8 to 21, wherein the tool assembly comprises at least two axially movable sleeves disposed within the tubing.

23. An assembly as claimed in claim 22 when dependent upon claim 13, wherein there is an upper sleeve disposed above the valve member and a lower sleeve disposed below the valve member.

24. An assembly as claimed in claim 23 wherein control fluid supplied to the tool assembly via the first control conduit maintains the lower sleeve with an upper face in sealing contact with the valve member, and the valve in the closed configuration.

25. An assembly as claimed in either of claims 23 or 24, wherein supplying control fluid to the tool assembly via the second hydraulic control conduit causes the lower sleeve to move axially downwardly, clear of the valve member, and the upper sleeve to move axially downwardly towards the valve member, to displace the valve member to a second, open configuration.

26. An assembly as claimed in claim 25, wherein the lower sleeve is adapted to move axially in response to a lower fluid pressure of the control fluid in the second hydraulic control conduit than the upper sleeve, such that the lower sleeve is displaced axially downwardly before the upper sleeve is moved axially downwardly to displace the valve member to the open configuration.

27. An assembly as claimed in any one of claims 23 to 26, wherein the tool assembly comprises two lower interconnected sleeves .

28. An assembly as claimed in claim 27, wherein the sleeve spaced from the valve member is lockable relative to a housing of the tool, while the sleeve adjacent the valve member floats, and is adapted to be urged into sealing contact with the valve member by fluid supplied to the tool via the first hydraulic control conduit.

29. An assembly as claimed in any one of claims 22 to 28, wherein the assembly further comprises a tubular housing defining an internal bore in which the sleeves and the valve member are mounted.

30. An assembly as claimed in claim 29, wherein the housing includes a recess in an internal wall thereof into which the valve member is disposed when in the open configuration.

31. An assembly as claimed in claim 30, wherein the upper sleeve retains the valve member in said recess .

32. An assembly as claimed in claim 29, wherein the housing includes a cavity in which the valve member is disposed when in the open configuration, such that it is isolated from well-bore fluids and debris therein.

33. An assembly as claimed in any one of claims 13 to 32, wherein the assembly further comprises a bypass vent which is selectively openable to permit flow between the interior and exterior of the assembly on opening and closing of the valve member, to provide a fluid path around the valve member .

34. An assembly as claimed in any preceding claim, wherein the control means further comprises means for monitoring the pressure of control fluid in the hydraulic control conduits and means for measuring the volume of control fluid supplied to or bled from the assembly via the selected one of the first and second control conduits .

35. An assembly as claimed in claim 34, wherein the control means further comprises a computer for monitoring the control fluid pressures and the volume of control fluid supplied such that the operating configuration of the assembly can be controlled and monitored.

36. A valve assembly for location in a borehole of a well, the assembly comprising: a hollow elongate member for location in the borehole; a valve adapted to be run into the hollow elongate member in a closed position and then moved to an open position; a first hydraulic control conduit for holding the valve in the closed position by application of a first control fluid to a closing and locking mechanism of the assembly; and a second hydraulic control conduit for actuating the valve to the open position, by application of a second control fluid to the closing and locking mechanism.

37. A method of controlling the operation of a tool assembly, the method comprising the steps of: disposing a hydraulically actuated downhole tool in a borehole of a well; coupling first and second hydraulic control conduits to the tool; supplying fluid to the tool via said first hydraulic control conduit, to maintain the tool in a first tool configuration; and supplying fluid to the tool via said second hydraulic control conduit, to actuate the tool to a second tool configuration.

38. A valve assembly for location in a borehole of a well, the valve assembly comprising: a hydraulically actuated valve movable between at least closed and open configurations; a first hydraulic control conduit coupled to the valve, for selectively supplying control fluid to the valve to maintain the valve in the closed configuration; a second hydraulic control conduit coupled to the valve for selectively supplying control fluid to the valve for moving the valve to the open configuration; and a seal mechanism for sealing the valve in the closed configuration, the seal mechanism including a seal for sealing with the valve and means for restraining the valve against movement when in the closed configuration, such that the seal only experiences a compressive load up to a predetermined level.