Patent Description:
In the oil and gas industry the actuation or operation of downhole equipment, such as valves, sleeves, tools and the like may be achieved in many different ways, such as hydraulically, pneumatically, electrically, mechanically etc. In hydraulic systems hydraulic power may be provided from surface, or other location remote from the downhole equipment, via one or more hydraulic control lines. Such control lines may extend externally of a tubing string, such as a completion or production tubing string, and thus located within a wellbore annulus and exposed to ambient wellbore pressure.

As with any hydraulic system there is always a risk of leakage, either from the system into the environment, or, where pressure conditions dictate, from the environment into the hydraulic system. In circumstances where the ambient (for example annulus) pressure exceeds that within the control lines, for example where the ambient fluid has a higher density, in the event of a leak the control line may become pressurised. Such pressurisation may cause undesired actuation of the associated downhole equipment.

<CIT> discloses systems and methods for selectively operating multiple hydraulic pressure controlled devices (PCDs) within a borehole using a common inflow and outflow line and a common cycling line. A control system is used wherein each of the PCDs is operationally associated with a separate sleeve controller. The sleeve controller for each PCD controls whether the individual PCD can be actuated by hydraulic pressure variations in the common inflow and outflow lines.

<CIT> discloses a multicycle hydraulic control valve. A control and actuation system for a well tool includes a control valve having one or more metal-to-metal seals, which open while differential pressure exists across the seals to thereby selectively connect pressure sources to an actuator to operate the well tool.

Both seals may be closed while a connection between the actuator and the pressure sources is switched by the control valve. The control valve may include a member having areas formed thereon acted upon by various pressures to facilitate operation of the control valve.

<CIT> discloses a hydraulic control system for operating a flow tube in a subsurface safety valve is disclosed. An isolation piston is used in conjunction with an operating control line and an engagement control line. Both control lines run from the surface. The isolation piston is spring loaded to equalize pressure across a dynamic piston to allow the flow tube to be shifted by a power spring to allow in turn the subsurface safety valve to close. Application of pressure on the engagement control line directs pressure applied through the operating control line to the top of the dynamic piston thus shifting the flow tube downwardly to open the subsurface safety valve.

<CIT> discloses a hydraulic control system for downhole tools that enables convenient selection and actuation of a well tool assembly from among multiple well tool assemblies installed in a well. Each well tool assembly includes a control module having a selecting device and a fluid metering device. A predetermined range of pressure levels on one of multiple hydraulic lines causes the well tool assembly to be selected for actuation, a differential between pressure on that hydraulic line and pressure on another hydraulic line determines a manner of actuating the selected well tool assembly, and pressure fluctuations on one of the hydraulic lines causes fluid to be transferred from another hydraulic line to an actuator of the well tool assembly.

An aspect of the present disclosure relates to a downhole fluid control apparatus, according to appended claim <NUM>.

In one example a first pressure differential applied between the first and second conduits may facilitate a first operation of the downhole device, and a second pressure differential applied between the first and second fluid conduits may facilitate a second operation of the downhole device.

When the valve member is in its first configuration the first and second conduits are in pressure communication with each other, and thus pressure balanced. The first configuration may thus also be defined as a balanced configuration. Any leakage of ambient fluid/pressure into one of the first and second conduits will not be permitted to develop a pressure differential between said conduits, which may otherwise cause an unintentional operation of the downhole device.

Furthermore, as the actuator is also in pressure communication with the ambient region, any leakage of ambient fluid/pressure into one of the first and second conduits will not cause the actuator to operate, as said actuator will also be pressure balanced, avoiding or minimising risk of the actuator reconfiguring the valve from its first position.

Accordingly, in the event of any exposure (for example via a leak) to ambient pressure when the valve is in its first configuration the actuator and conduits may be considered to be pressure balanced. This may permit the apparatus to function in a "fail-as-is" mode of operation.

In some examples the valve may be reconfigured from its first configuration to its second configuration by elevating the pressure in both the first and second conduits above the ambient pressure. In such an arrangement a subsequent pressure differential may be achieved by further elevating the pressure in one of the first and second fluid conduits. A pressure differential may be achieved by reducing the pressure in one of the first and second fluid conduits. A pressure differential may be achieved by retaining pressure in one of the first and second conduits while venting or relieving pressure in the other of the first and second conduits.

In some examples the first and second pressure differentials may be provided in opposing directions. For example, the first pressure differential may comprise providing a higher pressure in one of the first and second conduits, and the second pressure differential may comprise providing a higher pressure in the other of the first and second conduits.

In some examples the first and second pressure differentials may be provided in a common direction, and provided by different magnitudes of pressure differential.

The downhole fluid control apparatus may be locatable within a wellbore. The ambient region may contain a wellbore fluid, such as a completion fluid, produced fluid, gas or the like. The ambient pressure may comprise hydrostatic pressure. The ambient pressure may comprise formation pressure. The ambient pressure may be controlled and/or affected from a remote location, for example from a surface location.

In some examples where fluid communication is provided the apparatus may comprise a filter within a fluid communication path, to minimise risk of contamination of the actuator from material carried in the fluid within the ambient region. The actuator may be in pressure communication with the ambient region via a pressure transfer arrangement, for example via a piston arrangement, diaphragm or the like, thus providing pressure communication without also requiring fluid communication. This may minimise risk of the actuator being contaminated, for example with debris and the like within the ambient region.

The first and second conduits may form part of respective first and second control lines which extend between the pressure source and the downhole device. In some examples the first and second conduits may form an integral part of respective first and second control lines. Alternatively the first and second conduits may be separately provided and coupled in-line with respective first and second control lines. In this respect the first and second conduits may include opposing end connectors, such as threaded connectors or the like.

The first and second conduits may be provided within or through the housing of the apparatus. In one example the first and second fluid conduits may be provided by bores, for example drilled bores, through the housing.

The first and second fluid conduits may be in communication with the valve via one or more respective communication paths, such as bores, tubes, channels or the like.

The valve may comprise a valve member moveable between a first position in which the valve is configured in its first configuration, and a second position in which the valve is configured in its second configuration. When the valve member is in its first position a communication path may be established between the first and second conduits. When the valve member is in its second position any fluid communication path may be sealed to prevent communication between the first and second conduits.

In some examples the valve member may be axially moveable between its first and second positions.

The housing may define a valve bore, and the valve member may be moveable, for example axially moveable, within the valve bore. The valve bore may define a first valve port in communication with the first conduit and a second valve port in communication with the second conduit. The valve member may be moveable within the valve bore to selectively permit and prevent communication between the first and second valve ports.

The valve may comprise or define a spool valve.

The housing may define an actuator bore, wherein the actuator is moveable, for example axially moveable, within the actuator bore. The actuator bore may be separately provided from the valve bore. However, in some examples the actuator bore and valve bore may be provided as a common bore extending within, for example through, the housing. The valve and actuator may be separated by a sealing arrangement, such as an annular sealing arrangement. The sealing arrangement may permit the actuator and valve to be inter-engaged.

The actuator bore may comprise one or more ambient ports to facilitate or permit the actuator to be in communication with the ambient region.

The actuator bore may define a first actuator port in communication with the first conduit and a second actuator port in communication with the second conduit. The first and second actuator ports may permit the actuator to be in communication with the first and second conduits.

The actuator may function to move, for example axially move, the valve member. In some examples the actuator may be coupled to the valve member. The actuator may comprise the valve member.

The actuator may be moveable in a first direction to cause the valve to be reconfigured from its first configuration to its second configuration. The actuator may be moveable in a second direction to cause the valve to be reconfigured from its second configuration to its first configuration. The second direction may be opposite to the first direction.

Pressure within the first and/or second conduit may act on the actuator to bias said actuator in the first direction. Ambient pressure may resist movement of the actuator in the first direction. This arrangement may permit the actuator to be moved in the first direction when the pressure within the first and/or second conduit exceeds ambient pressure.

The actuator may be configured such that ambient pressure may resist movement of the actuator in its first direction, but said ambient pressure prevented from causing movement of the actuator in its second direction. Accordingly, ambient pressure may be prevented from operating/moving the actuator rod.

The actuator may be biased in the second direction by a biasing arrangement, such as a spring or the like.

The actuator may comprise an actuator piston assembly operable by pressure provided via one or both of the first and second conduits.

The actuator piston assembly may comprise an actuator rod. The actuator rod may be moveable, for example axially moveable within the housing, for example within the actuator bore. The actuator rod may be secured to the valve, for example to the valve member of the valve. The actuator rod may comprise a unitary component. The actuator rod may comprise multiple components secured or arranged together.

In some examples ambient pressure may be communicated to the actuator via the actuator rod, for example via one or more internal bores within the actuator rod.

The actuator assembly may comprise a first piston head moveably mounted in a first piston bore section within the housing. The first positon bore section may be formed or provided by the actuator bore. The first piston head may be generally annular in form. The first piston head may divide the first piston bore section into a first conduit chamber and a first ambient chamber. The first conduit chamber may be in pressure (for example fluid) communication with the first conduit, and the first ambient chamber may be in pressure (for example fluid) communication with the ambient region. Accordingly, the first piston head may move in the first piston bore section in accordance with a pressure differential across said first piston head between the first conduit and ambient chambers.

The first piston head may be mounted around the actuator rod, for example circumscribing the actuator rod. The first piston head may be coupled to the actuator rod such that movement of the first piston head may cause movement of the actuator rod, and thus the valve. In one example the first piston head may be coupled to the actuator rod via a unidirectional connection. The unidirectional connection may permit the first piston head to drive the actuator rod in the first direction, and prevent the first piston head from driving the actuator rod in the second direction. The unidirectional connection may permit the first piston head to be coupled with the actuator rod during movement of the first piston head in the first direction, but decoupled during movement of the first piston head in the second direction. The unidirectional connection may comprise an upset portion (e.g., a no-go profile) on the actuator rod, wherein the first piston head engages the upset portion when moved in the first direction, and disengaged from the upset portion when moved in the second direction.

The actuator assembly may comprise a second piston head moveably mounted in a second piston bore section within the housing. The second positon bore section may be formed or provided by the actuator bore. The second piston bore section may be isolated from the first bore section by a sealing arrangement. The first and second piston heads may be arranged in a series configuration.

The second piston head may be generally annular in form. The second piston head may divide the second piston bore section into a second conduit chamber and a second ambient chamber. The second conduit chamber may be in pressure (for example fluid) communication with the second conduit, and the second ambient chamber may be in pressure (for example fluid) communication with the ambient region. Accordingly, the second piston head may move in the second piston bore section in accordance with a pressure differential across said second piston head between the second conduit and ambient chambers.

The second piston head may be mounted around the actuator rod, for example circumscribing the actuator rod. The first and second piston heads may be axially spaced apart along the actuator rod. The second piston head may be coupled to the actuator rod such that movement of the second piston head may cause movement of the actuator rod, and thus the valve. In one example the second piston head may be coupled to the actuator rod via a unidirectional connection. The unidirectional connection may permit the second piston head to drive the actuator rod in the first direction, and prevent the second piston head from driving the actuator rod in the second direction. The unidirectional connection may permit the second piston head to be coupled with the actuator rod during movement of the second piston head in the first direction, but decoupled during movement of the second piston head in the second direction. The unidirectional connection may comprise an upset portion (e.g., a no-go profile) on the actuator rod, wherein the second piston head engages the upset portion when moved in the first direction, and disengaged from the upset portion when moved in the second direction.

The downhole fluid control apparatus may comprise a downhole hydraulic control apparatus.

The downhole device may comprise any downhole device. For example, the downhole device may comprise a valve, such as a ball valve. The downhole device may comprise a sliding sleeve device.

The first operation of the downhole device may comprise an opening operation, for example a valve opening operation of the downhole device. The second operation of the downhole device may comprise a closing operation, for example a valve closing operation of the downhole device.

A second aspect of the present disclosure relates to a method for downhole fluid control, according to appended claim <NUM>.

The method may comprise establishing a pressure differential between the first and second conduits when the valve is configured in its second configuration to operate the downhole device. In one example the method may comprise, when the valve is in its second configuration, establishing a first pressure differential between the first and second conduits to facilitate a first operation of the downhole device. The method may comprise, when the valve is in its second configuration, establishing a second pressure differential between the first and second conduits to facilitate a second operation of the downhole device.

The method may be performed with the fluid control apparatus of any other aspect.

In some examples the downhole fluid control apparatus may be capable of use in other applications which are not restricted to a downhole environment. For example, the apparatus may be used in other applications where there is potential for leakage to/from a fluid system that may cause unintentional operation of devices or equipment.

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

Aspects of the present disclosure relate to apparatus and methods for providing fluid control in a wellbore. Such aspects may provide advantages in terms of preventing or minimising the risk of wellbore pressure, which may leak into the associated hydraulic system, from causing unintentional operation of one or more downhole devices.

<FIG> diagrammatically illustrates a drilled wellbore <NUM> with a casing string <NUM> cemented therein via a cement sheath <NUM>. The wellbore <NUM> is illustrated as a vertical bore section, although could be a deviated and/or horizontal bore section. Furthermore, the wellbore <NUM> may alternatively be an open hole wellbore (i.e., absent any casing string).

A tubular string <NUM>, such as a completion string, extends within the wellbore <NUM>, with an annulus <NUM> defined between the tubular string <NUM> and the casing string <NUM>. First and second control lines <NUM>, <NUM> extend along an outer surface of the tubular string <NUM>, and thus in the annulus <NUM>, and provide a fluid communication path between a surface located pressure source (not shown) and a downhole device <NUM>, which in the present example is a ball valve, although any downhole device may be provided. In the present example a first pressure differential established between the first and second control lines <NUM>, <NUM> provides a first operation of the ball valve <NUM>, for example an opening operation of the ball valve <NUM>. A second pressure differential established between the first and second control lines <NUM>, <NUM> provides a second operation of the ball valve <NUM>, for example a closing operation of the ball valve <NUM>. In the present example the first pressure differential may comprise the pressure in the first control line <NUM> exceeding the pressure in the second control line <NUM>, and conversely the second pressure differential may comprise the pressure in the second control line <NUM> exceeding the pressure in the first control line <NUM>. The first and second pressure differentials may be achieved via suitable pressure control at surface, for example.

As the ball valve <NUM> is operated by a pressure differential between the first and second control lines <NUM>, <NUM>, should one of the control lines <NUM>, <NUM> become exposed to annulus pressure, for example due to a leak, there is a risk of the ball valve <NUM> being operated unintentionally. To minimise this risk, a fluid control apparatus <NUM> according to an aspect of the present disclosure is coupled in-line with the first and second control lines <NUM>, <NUM>.

<FIG> provides a diagrammatic cross-sectional view of the fluid control apparatus <NUM>, provided in an initial balanced configuration. In such a configuration any pressure differential between the first and second control lines <NUM>, <NUM> may be prevented. This balanced configuration may be established during running of the tubular string <NUM>, and up until operation of the valve <NUM> is required, at which stage the apparatus <NUM> may be reconfigured, which will be described in detail below.

The apparatus <NUM> includes a housing <NUM> with first and second conduits <NUM>, <NUM> in the form of drilled bores extending through the housing <NUM>. The first conduit <NUM> includes opposing threaded end connectors <NUM>, <NUM> which facilitates inline connection with the first control line <NUM> (<FIG>). Similarly, the second conduit <NUM> includes opposing threaded end connectors <NUM>, <NUM> with facilitate inline connection with the second control line <NUM> (<FIG>).

The apparatus <NUM> also comprises a primary bore <NUM> extending through the housing <NUM>, aligned generally parallel with the bores forming the first and second conduits <NUM>, <NUM>. An assembly <NUM> is axially moveably mounted within the primary bore <NUM> and includes a valve <NUM> coupled with an actuator <NUM>.

The valve <NUM> includes a valve seal insert <NUM> which is fixed relative to the housing <NUM> via a wire connection <NUM>. The valve seal insert <NUM> includes a first pair of seals <NUM> (e.g., O-rings) which straddle a port <NUM> which is in fluid communication with the first conduit <NUM>, wherein the valve seal insert <NUM> includes an aligned port <NUM> which provides a communication path to the inner diameter of said valve seal insert <NUM>. The valve seal insert <NUM> includes a second pair of seals <NUM> (e.g., O-rings) which straddle a port <NUM> which is in fluid communication with the second conduit <NUM>, wherein the valve seal insert <NUM> includes an aligned port <NUM> which provides a communication path to the inner diameter of said valve seal insert <NUM>. It will be noted that first and second pairs of seals <NUM>, <NUM> include a common seal member.

The valve <NUM> further includes a valve member or spool <NUM> which is axially moveable within the valve seal insert <NUM>, wherein the valve spool <NUM> includes an annular recess <NUM> on an outer surface thereof.

The valve <NUM> is illustrated in a first configuration in <FIG>, with the valve spool <NUM> located at a first position. When configured as shown in <FIG> the annular recess <NUM> of the valve spool <NUM> is positioned to provide communication between the ports <NUM>, <NUM> in the valve seal insert <NUM>, thus presenting the first and second conduits <NUM>, <NUM> in communication with each other. In this respect, the first and second conduits <NUM>, <NUM> are pressure balanced, such that a pressure differential therebetween is not permitted.

The actuator <NUM> comprises an actuator rod <NUM> formed from multiple parts threaded together (although in other examples a unitary rod may be provided), wherein one end of the actuator rod <NUM> is coupled with the valve spool <NUM>, such that axial movement of the actuator rod <NUM> causes corresponding axial movement of the valve spool <NUM>. The actuator rod <NUM> extends through an annular seal portion <NUM> of the valve seal insert <NUM>, which seals against both the inner surface of the primary bore <NUM> and the actuator rod <NUM>. The annular seal portion <NUM> thus functions to sealingly isolate the actuator <NUM> from the valve <NUM>.

The actuator <NUM> further comprises a first piston head in the form of a first annular piston <NUM> axially moveable within a first piston bore section <NUM> and sealingly engaged with both the inner surface of the primary bore <NUM> and an outer surface of the actuator rod <NUM>. The first annular piston <NUM> divides the first piston bore section <NUM> into a first conduit chamber <NUM> and a first ambient chamber <NUM>. The first conduit chamber <NUM> is in communication with the first conduit <NUM> via a communication path <NUM>, and the first ambient chamber <NUM> is in communication with an ambient region externally of the apparatus (specifically the annulus <NUM> shown in <FIG>) via a bore <NUM> extending through the actuator rod <NUM> (alternatively a port may be provided through the housing <NUM>). Threaded connections between adjacent components of the actuator rod <NUM> may provide a suitable communication path from the bore <NUM> to the first ambient chamber <NUM>. Accordingly, the first annular piston <NUM> is moveable in accordance with a pressure differential between the first conduit <NUM> and the annulus <NUM>. In the configuration of <FIG> the first annular piston <NUM> is positioned such that the first conduit chamber <NUM> is at its minimum volume and the first ambient chamber <NUM> is at its maximum volume.

The first annular piston <NUM> is engaged with the actuator rod <NUM> via a unidirectional connection which provides an axial connection between the first annular piston <NUM> and the actuator rod <NUM> when the first annular piston <NUM> is moved in a first direction illustrated by arrow <NUM>, and prevents any axial connection when the first annular piston <NUM> is moved in a reverse second direction illustrated by arrow <NUM>. In the present example the unidirectional connection includes an upset profile <NUM> provided on the actuator rod <NUM>, wherein the first annular piston <NUM> engages the upset profile <NUM> when said piston <NUM> is moved in the first direction <NUM>, and is permitted to disengage the upset profile <NUM> when the first annular piston <NUM> is moved in the second direction <NUM>.

The unidirectional connection permits the first annular piston <NUM> to cause the actuator rod <NUM> to move and operate the valve <NUM> when the pressure in the first conduit <NUM> exceeds annulus pressure (moving the actuator rod in the first direction <NUM>). However, when ambient pressure exceeds the pressure within the first conduit <NUM> the first annular piston may move in the second direction independently of the actuator rod <NUM>.

The actuator <NUM> further comprises a second piston head in the form of a second annular piston <NUM> axially moveable within a second piston bore section <NUM> and sealingly engaged with both the inner surface of the primary bore <NUM> and an outer surface of the actuator rod <NUM>. The first and second piston bore sections <NUM>, <NUM> are separated by an annular sealing member <NUM> which is fixed relative to the housing <NUM>.

The second annular piston <NUM> divides the second piston bore section <NUM> into a second conduit chamber <NUM> and a second ambient chamber <NUM>. The second conduit chamber <NUM> is in communication with the second conduit <NUM> via a communication path <NUM>, and the second ambient chamber <NUM> is in communication with an ambient region externally of the apparatus (specifically the annulus <NUM> shown in <FIG>) via the bore <NUM> extending through the actuator rod <NUM> (alternatively a port may be provided through the housing <NUM>). Threaded connections between adjacent components of the actuator rod <NUM> may provide a suitable communication path from the bore <NUM> to the second ambient chamber <NUM>. Accordingly, the second annular piston <NUM> is moveable in accordance with a pressure differential between the second conduit <NUM> and the annulus <NUM>. In the configuration of <FIG> the second annular piston <NUM> is positioned such that the second conduit chamber <NUM> is at its minimum volume and the second ambient chamber <NUM> is at its maximum volume.

In a similar manner to the first annular piston <NUM>, the second annular piston <NUM> is engaged with the actuator rod <NUM> via a unidirectional connection, specifically an upset profile <NUM>.

The actuator rod <NUM> is biased to move in the second direction <NUM> via a spring <NUM> which in the example shown in <FIG> acts between an end <NUM> of the actuator rod <NUM> and an annular sealing member <NUM> which is fixed to the housing <NUM>. A spring may alternatively be provided at a different location within the apparatus <NUM>.

When the apparatus <NUM> is in the configuration of <FIG>, the first and second conduits <NUM>, <NUM> are at a pressure which is lower than annulus pressure, such that the bias of the spring <NUM> positions the valve spool <NUM> in the illustrated first position, maintaining the first and second conduits <NUM>, <NUM> in communication and pressure balanced. As such, operation of the ball valve <NUM> (<FIG>) is not permitted.

When operation of the ball valve <NUM> is required, the pressure in both the first and second conduits <NUM>, <NUM> is elevated above annulus pressure, which, as illustrated in <FIG>, causing the first and second annular pistons <NUM>, <NUM> to be driven in the first direction <NUM>, providing corresponding movement of the actuator rod <NUM> and connected valve spool <NUM>, compressing spring <NUM>. The valve spool <NUM> is thus moved to a second position to reconfigure the valve <NUM> into a second configuration in which the ports <NUM>, <NUM> in the valve seal insert <NUM> are no longer in communication, isolating the first and second conduits <NUM>, <NUM>. When configured as shown in <FIG> the apparatus <NUM> may be considered to be arranged in an armed position.

As the first and second conduits <NUM>, <NUM> are no longer in communication a pressure differential therebetween may be provided to cause operation of the ball valve <NUM>. For example, as illustrated in <FIG> the pressure within the first conduit <NUM> may be maintained, whereas the pressure within the second conduit <NUM> may be reduced, for example bled off or vented. This may provide a closing operation of the ball valve <NUM>.

The maintained high pressure within the first conduit <NUM> holds the first annular piston <NUM> in position, maintaining the valve <NUM> in its second configuration and the isolation between the first and second conduits <NUM>, <NUM>. The second annular piston <NUM> may no longer be exposed to sufficient pressure via the second conduit <NUM> such that annulus pressure may be permitted to cause the second annular piston <NUM> to move in the second direction <NUM>. However, such movement of the second annular piston <NUM> should not apply any return force on the actuator rod <NUM> by virtue of the unidirectional connection therebetween.

Whenever required, a reverse or second pressure differential between the first and second conduits <NUM>, <NUM> may be established to provide a second operation of the ball valve <NUM>, for example an opening operation. Such a reverse or second pressure differential applied is illustrated in <FIG>, in which a high pressure is applied in the second conduit <NUM>, with the pressure in the first conduit <NUM> reduced, for example vented or bled off. In some examples the high pressure condition of both the first and second conduits <NUM>, <NUM>, as illustrated in <FIG>, may be established prior to switching between different operational pressure differentials.

Once necessary operations have been performed, and/or between performing different operations, the pressure in both the first and second conduits <NUM>, <NUM> may be reduced below annulus pressure, permitting the spring <NUM> to move the actuator rod <NUM> in the second direction, returning the valve spool <NUM> to its first position and thus the valve <NUM> to its first configuration, as illustrated in <FIG>. As such, the first and second conduits <NUM>, <NUM> may once again be provided in communication via the ports <NUM>, <NUM> in the valve seal insert <NUM> and the annular recess <NUM> in the valve spool <NUM>.

Claim 1:
A downhole fluid control apparatus (<NUM>), comprising:
first and second conduits (<NUM>, <NUM>) each providing a fluid communication path between a pressure source and a downhole device (<NUM>);
a valve (<NUM>) provided within a housing (<NUM>) and configurable between a first configuration in which the first and second conduits (<NUM>, <NUM>) are in pressure communication via the valve (<NUM>) preventing a pressure differential between the first and second conduits (<NUM>, <NUM>) being established and thereby preventing operation of the downhole device (<NUM>), and a second configuration in which the first and second conduits (<NUM>, <NUM>) are isolated from each other allowing for a pressure differential to be established between the first and second conduits (<NUM>, <NUM>), wherein the pressure differential established between the first and second conduits (<NUM>, <NUM>) operates the downhole device (<NUM>); and
an actuator (<NUM>) for operating the valve (<NUM>), the actuator (<NUM>) being in pressure communication with the first and second conduits (<NUM>, <NUM>) and with an ambient region (<NUM>) external of the apparatus (<NUM>), said ambient region (<NUM>) being a wellbore annulus (<NUM>) defined between a tubing string (<NUM>) and a casing string (<NUM>), such that when the pressure within each of the first and second conduits (<NUM>, <NUM>) is lower than the ambient pressure the valve (<NUM>) is configured in its first configuration, and when the pressure within at least one of the first and second conduits (<NUM>, <NUM>) exceeds the ambient pressure the valve (<NUM>) is configured in its second configuration.