"Apparatus and Method for Controlling the Flow of Downhole Fluids"

The present invention concerns an apparatus and a method for controlling the flow of downhole fluids.

Fig. 1 shows a prior art method for the production of hydrocarbons. A borehole 12 is drilled and a production tubing or pipe 22 is then run into the borehole 12 to allow hydrocarbon production from three zones, A, B and C in a hydrocarbon formation 10. The pipe 22 has a number of ports 23a, 23b, 23c through which hydrocarbons can be produced. The pipe 22 in the region of each port 23a, 23b, 23c is surrounded by a respective sandscreen 24a, 24b, 24c that restricts ingress of formation particles such as rocks and sand above a predetermined size through each port 23 and into the pipe 22. The annulus between the borehole 12 and the production tubing 22 is isolated by a packer 25 in the transition region between each zone, A, B, C to substantially restrict the cross-flow of hydrocarbons between any one zone and an adjacent zone.

Arrows 27 show the direction of fluid flow from each zone in the formation 10, through the respective sandscreen 24 and into the throughbore of the pipe 22 via the ports 23. Flow control devices (not shown) can be incorporated into the pipe 22 in the region of the ports 23 to selectively control the flow of fluid through the ports 23 from each zone of the formation 10. However, incorporating individual flow control devices in the pipe 22 associated with each port 23 as is known in the prior art, can significantly increase the cost and complexity of the production tubing.

According to a first aspect of the invention, there is provided an apparatus for controlling the flow of downhole fluids, the apparatus comprising:

a body having a throughbore, a first port and a second port spaced relative to the first port, wherein each port extends through a sidewall of the body to enable fluid communication between the throughbore and an exterior of the body; a flow control device, arranged to control the flow of fluids through the first and second ports; and an actuator associated with the flow control device for selective actuation of the flow control device to control the flow of downhole fluids.

The flow control device can be actuable between: an open configuration in which there is fluid communication between the throughbore and the exterior of the body via the first and second ports; and a closed configuration in which fluid communication between the throughbore and the exterior of the body is substantially restricted. The flow control device can be arranged in the closed configuration to substantially obturate the ports.

The flow control device can also be actuable in a plurality of intermediate configurations between the open and the closed configurations. The intermediate configurations can permit a degree of fluid communication between the throughbore and the exterior of the body such that the area of the ports is restricted to a certain degree relative to the fully open position.

Thus, fluid flow through the ports can be choked to control the flow of fluids downhole.

The flow control device can comprise a sliding sleeve.

The apparatus preferably permits control of the flow of downhole fluids from two production zones in a subterranean formation. The first port can be capable of communicating with a first production zone and the second

port can be capable of communicating with a second production zone. Preferably, the first and second production zones are distinct separate zones within the formation.

The body can be a tubular body. The second port can be spaced axially relative to the first port. The tubular body can be provided with appropriate end connections to enable connection of the apparatus as part of a pipe string.

The body can be coupled to a first portion and a second portion of slotted screen. The slotted screen typically has a greater radial extent than the body. The first portion of slotted screen can communicate with the first port and extend axially in one direction and the second portion of slotted screen can communicate with the second port and extend axially in an opposing direction. The portions of slotted screen can be sandscreen.

A first fluid flow path can be defined between the first portion of slotted screen and the first port and a second fluid flow path can be defined between the second portion of slotted screen and the second port. The first fluid flow path can be arranged to allow flow of fluids therethrough in an opposing direction relative to the flow of fluids through the second fluid flow path.

The portion of slotted screen can be incorporated as part of a sandscreen sub. Each end of the body can be coupled to a sandscreen sub. The slotted screen can be coaxial with the body. The size of the slotted screen mesh can be determined according to the maximum acceptable size of formation particles travelling through the ports and into the throughbore.

An isolator can be provided on the exterior of the body located between the first and second ports. The isolator can substantially fluidly isolate the first and second ports by obturating an external annulus surrounding the apparatus. The isolator can comprise a packer. The packer can be swellable upon contact with downhole fluids.

The actuator can be arranged to actuate movement of the flow control device into the open configuration.

The flow control device can be biased into the open configuration. The flow control device can be retained in the closed configuration by a restraint. The flow control device can be initially retained in the closed configuration by restraining movement of the flow control device relative to the body. The actuator can be arranged to remove or change the configuration of the restraint and permit relative movement of the flow control device and the body, such that the flow control device moves from the closed configuration to the open configuration.

The actuator can be accommodated by at least one of the body or the flow control device.

The flow control device can be sealed against the body and relative movement of the flow control device and the body can be constrained to the axial direction.

A compartment of compressible fluid can be provided between the flow control device and the body. The compressible fluid can be sealed within the compartment at a lower pressure relative to the predetermined downhole pressure. For example, the compressible fluid can comprise a

gas such as air and the pressure of the compressible fluid can be surface atmospheric pressure.

The seals isolating the compressible fluid compartment can enclose a greater area towards one end of the flow control device than towards the other end. Therefore, when the restraint is removed the flow control device can act as a piston urged to compress the fluid compartment as a result of the difference in seal areas.

Removal or modification of the restraint typically allows compression of the fluid compartment driven by the flow control device and permits relative movement of the body and the flow control device into the open configuration. The fluid compartment can be held against compression by the restraint. The restraint can act to restrict relative movement of the flow control device and the body. The restraint can comprise a selectively breakable member such as a Kevlar string to maintain the relative position of the body and the flow control device in the closed configuration. According to this example, the actuator can include a heat source to cause the Kevlar string to melt.

The actuator can comprise a remote actuation system to remove the action of the restraint and actuate relative movement of the flow control device and the body. Thus actuation can optionally be initiated without need for either electric or hydraulic cables run from the surface.

In some embodiments, the actuator can comprise a pump, such as an electric pump, configured to create a pressure differential across a component of the device (e.g. across the flow control device) when the pump is activated, which causes the flow control device to change configurations. In some embodiments, the compressible fluid

compartment can incorporate a bleed valve, optionally controlled by a solenoid or other switching device, which can be activated to open or close the valve, and therefore create or maintain a pressure differential that causes the flow control device to change configurations.

The actuator can be coupled to a power source. The power source can be a battery. The power source can be housed in a sidewall of the body or the flow control device.

The actuator can include a reader electrically coupled to an electronics pack, wherein the reader is arranged to read a signal from a remote source and wherein the signal can be processed by the electronics pack to selectively actuate movement of the flow control device into the open configuration.

The reader can comprise an antenna arranged to remotely communicate using radio frequency identification.

Alternatively or additionally, the actuator can comprise a pressure sensor electrically coupled to an electronics pack and wherein the pressure signal can be processed by the electronics pack to selectively actuate movement of the flow control device into the open configuration.

Alternatively and/or additionally, the actuator can comprise an electronic circuit and a timer switch coupled to the flow control device to actuate movement into the open configuration after a predetermined period of time.

The apparatus can also include a backup actuation system. The backup actuation system can be mechanically controlled. Thus, intervention

equipment such as a shifting tool run on slickline or coiled tubing can be deployed into the well to manually actuate movement of the flow control device into the open configuration.

According to a second aspect of the invention there is provided a method of producing fluids through slotted screen, the method comprising the steps of:

(a) providing a first portion of slotted screen and a second portion of slotted screen, each portion of slotted screen being coupled to a tubular having a throughbore and first and second ports extending through a sidewall of the tubular;

(b) defining a first fluid flow path between the first portion of slotted screen and the first port in one direction and defining a second fluid flow path between the second portion of slotted screen and the second port in an opposing direction; and

(c) flowing fluids through the first and second ports into the throughbore of the tubular to thereby produce fluids through the first and second portions of slotted screen.

Features and steps of the first aspect of the invention can also be applicable to the second aspect of the invention where appropriate.

The apparatus and method of the first and second aspects of the invention is especially, though not exclusively suited for use in deviated or horizontal wells.

Embodiments of the present invention will now be described with reference to the accompanying figures in which:

Figure 2 is a sectional view of an apparatus in a closed configuration;

Figure 3 is a sectional view of the apparatus of Figure 2 in an open configuration;

Figures 4 to 6 are detailed sectional views of a left hand portion, a middle portion and a right hand portion of the Figure 2 apparatus respectively; and

Figures 7 to 9 are detailed sectional views of a left hand portion, a middle portion and a right hand portion of the Figure 3 apparatus respectively.

An apparatus 100 is shown in a closed configuration in figures 2 and 4 to 6. The apparatus 100 comprises a generally cylindrical hollow inner sleeve 102 and a generally cylindrical hollow outer tubular 104. The inner sleeve 102 is housed within the throughbore of the outer tubular 104 and the inner sleeve 102 has a coaxial throughbore 46 through which hydrocarbons can be produced. The inner sleeve 102 is made up from several individual lengths of joined tubing: an inner tubular 50, an inner casing 70, an RFID antenna 72, an inner casing 80 and an inner tubular 150 respectively coupled to one another. The outer tubular 104 is made up from two connected portions of outer housing 30, 130.

A right hand end of the apparatus 100 in figure 6 is located upstream of a left hand end of the apparatus in figure 4, in use. Therefore the left hand end of the apparatus 100 in Figure 4 is the closest part of the apparatus 100 to the surface in use. Starting at the upstream end shown in figure 6, the outer housing 30 that forms part of the outer tubular 104 has a pin end 36 that enables connection with a length of adjacent sandscreen (not shown). An internal end of the outer housing 30 has a threaded box end 38 to enable connection of the throughbore 46 of the outer housing 30 with an adjacent pipe length. An annular array of axial bores 32 extends parallel to the axis of the throughbore 46 in a sidewall of the outer housing

30. (The annular array of individual axial bores 32 could alternatively be a single annular channel). An outer end 32e of each bore 32 receives fluids produced through the adjacent sandscreen in use. The other end of the annular channel 32 is joined to a plurality of ports 33 (or a single annular groove) that extend radially inwardly to fluidly connect the axial bores 32 with an interior of the outer housing 30.

A part of the inner sleeve 102 in the form of the inner tubular 50 is located within the throughbore of the outer housing 30. An annular step 37 formed in the interior of the outer housing 30 retains the inner tubular 50 within the outer housing 30. preventing its passage through the outer end 32e. The inner tubular 50 is provided with a plurality of radial holes 40 to fluidly connect an interior of its throughbore 46 with an exterior of the tubular 50. Annular seals 34 are provided in grooves on an inner surface of the outer housing 30 to fluidly isolate the ports 33 from the holes 40 in the closed configuration. In this example, a diameter 44 of the inner tubular 50 between the seals 34 is 3.955 inches (10.05 centimetres).

Above the seals 34, a mid region of the inner tubular 50 has two axially spaced shallow annular groves 64, 65 formed in its outer surface. An internal surface of the outer housing 30 is provided with a radially inwardly projecting protrusion 62 shown in Figure 5 seated within the annular groove 65 on the outside surface of the inner tubular 50. The protrusion 62 is typically biased radially inwardly, and is optionally expandable, and for this purpose, it can be a split ring or circlip. The upper end of the outer housing 30 has a spur 30s, that has an external thread for threaded connection to another portion of outer housing 130 (internally threaded) and the two portions are sealed together in the region of the spur by means of seals 58. An upper end of the spur 30s has a radial threaded bore to receive an anchor screw 54, which is therefore located between

the exterior of the outer casing 30 and the interior of the outer housing 130.

The downstream end of the outer housing 130 shown in Figure 4 has an external pin end 136 enabling the apparatus 100 to be connected to a second sandscreen sub (not shown). The outer housing 130 also has a threaded internal box end 138 to allow the throughbore 46 to be connected to an adjacent length of pipe. In a similar manner to the upstream end of the apparatus 100, an annular channel or a number of axial bores 132 extend parallel to the axis 46 within a sidewall of the outer housing 130 and the bores 132 fluidly connect with an interior of the outer housing 130 by means of a plurality of radially spaced ports 133 (or an annular groove). Annular seals 134 are disposed on either side of the ports 133 to fluidly isolate the ports 133.

In the closed configuration, the exterior of the inner sleeve 102 covers and thereby obturates the ports 33, 133. A swell packer 42 is located between each set of ports 33, 133 in an annular recess in the exterior of the outer housing 30.

As shown in Figure 5, the inner tubular 50 is attached by set screws to an inner casing 70 and sealed against it by means of annular seals 58 provided in annular grooves in the inner casing 70. The inner casing 70 has an annular stepped external surface towards its upstream end to allow connection of a primary anchor 56 to the casing 70 of the inner sleeve

102. A Kevlar string 55 is retained in tension between the primary anchor 56 and the anchor screw 54 connected to the spur 30s on the outer housing 30. Typically a high resistance wire coil (not shown) surrounds the Kevlar string 55.

At its widest outer diameter, the exterior of the inner casing 70 is provided adjacent and slidable against an inner surface of the outer housing 130.

In the closed configuration, the Kevlar string 55 holds and thus restrains the inner sleeve 102 from movement relative to the outer tubular 104.

A sidewall of the inner casing 70 houses a pressure sensor 52 that communicates with the throughbore 46 of the apparatus 100.

The inner casing 70 is screwed to a radio frequency identification (hereinafter RFID) antenna 72 and is sealed against it by means of annular seals 73 located in annular grooves in the inner casing 70. The RFID antenna 72 is cylindrical and comprises an inner liner and a coiled conductor in the form of a length of copper wire that is concentrically wound around the inner liner in a helical coaxial manner. Insulating material circumscribes an exterior of the coiled conductor. The liner and the insulating material are formed from a non-magnetic and non- conductive material such as fibreglass, rubber or the like. The RFID antenna 72 is formed such that the insulating material and coiled conductor are sealed from the outer environment and the throughbore 46.

An electronics pack 7Op is typically accommodated in a sidewall of the inner casing 70 and is electrically connected to the RFID antenna and the pressure sensor 52. The electronics pack 7Op, the RFID antenna 72 and the pressure sensor 52 are all electrically connected to and powered by a battery pack 70b typically located in a sidewall of the inner casing 70. The electronics pack 7Op can optionally be provided with a timer so that once the RFID antenna 72 has read a signal that corresponds to an actuation command, the step of actuation can be carried out at a predetermined time interval after the command is received.

The RFID antenna 72 is screwed to another portion of inner casing 80 and sealed against it by means of the annular seals 73 located in grooves in the inner casing 80. As shown in Figure 4, the inner casing 80 is attached by set screws to an inner tubular 150 and the two are sealed together by annular sleeve seals 84. An outer diameter 55 of the inner tubular 150 between the sleeve seals 84 amounts to 3.950 inches (10.03 centimetres). A plurality of holes 140 extend through the sidewall of the inner tubular 150.

An annular chamber 57 is located between the seals 34 and the sleeve seals 84. The chamber 57 is formed in the annulus between an exterior of the inner sleeve 102 and an interior of the outer tubular 104. The chamber 57 is typically filled with compressible material such as gas (e.g. air) at surface atmospheric pressure. The outer housing 130 has an inner annular step 87 that defines an end of the chamber 57.

Ambient pressure within the throughbore 46 of the apparatus 100 is acting on a greater area at the upstream end of the inner sleeve 102 than at the downstream end of the inner sleeve 102 because of the difference in the outer diameter 44 of the inner tubular 50 at the seals 34 and the outer diameter 85 of the inner tubular 150 at the sleeve seals 84. Therefore, the higher pressure of downhole fluid within the throughbore 46 compared to the pressure of air within the chamber 57 creates a pressure differential, which acts to urge the inner sleeve 102 to move in the downstream direction. However, the inner sleeve 102 is connected to the outer tubular 104 by means of the Kevlar string 55. The Kevlar string 55 acts as a restraint to restrict relative movement of the outer tubular 104 and the inner sleeve 102 because the string 55 connects the anchor screw 54 of the outer housing 30 to the primary anchor 56 of the inner casing 70.

Thus, in the closed configuration the ports 33, 133 are isolated from the holes 40, 140 and the inner sleeve 102 is held against downstream movement relative to the outer tubular 104.

Prior to use, the external pin ends 36, 136 of the apparatus 100 are each joined to sandscreen subs (not shown). Each sandscreen sub comprises a portion of slotted screen that allows hydrocarbons to be produced therethrough, but substantially restricts ingress of rocks and sands. The sandscreen sub attached to the pin end 36 extends axially upstream and the sandscreen sub is arranged to define a fluid flow path between the slotted screen and the annular chamber 32. The sandscreen sub attached to the pin end 136 extends axially downstream and the sandscreen sub is arranged to define a fluid flow path between the slotted screen and the annular chamber 132.

The interior of the apparatus 100 is joined at either end to lengths of pipe (not shown) with pin connections that engage with the threaded box connections 38, 138. The individual lengths of pipe are joined and sealed to one another to form a continuous hollow tubing referred to as a production tubing. Across its full length, the production tubing can incorporate several sand screen subs and associated apparatus 100. Other downhole devices can also be incorporated into the production tubing as appropriate. The apparatus 100 is located at a predetermined position along the production tubing so that once run in, the adjacent slotted screen of the sand screen subs is positioned in respective production zones of the surrounding formation that contain hydrocarbon reservoirs of interest.

An RFID (not shown) for use in conjunction with the RFID antenna 72 can be a 32 millimetre glass transponder with the model number RI-TRP- WRZB-20 produced by Texas Instruments and suitably modified for use downhole. The RFID tag comprises a miniature electronic circuit having a transceiver to and a small antenna within the hermetically sealed casing. The tag should be hermetically sealed and capable of withstanding high temperatures and pressures. Ceramic or fibreglass tags are preferable and should be able to withstand a pressure of 20 000 psi (138 MPa). Oil filled tags are also well suited to use downhole as they have a good collapse rating. The RFID tags are programmed at the surface by an operator to generate a unique signal and command. According to the present example, the RFID tag has been programmed at the surface by the operator to transmit information instructing that the apparatus 100 is to be moved in to the open configuration. Similarly, prior to being included in the apparatus 100 at the surface each of the electronics packs coupled to the respective RFID antenna 72 is separately programmed to respond to a specific signal.

Once the well is ready to be completed, the production tubing containing the apparatus 100 and the sand screen subs is run downhole, typically in the closed configuration in which the ports 33, 133 are substantially obturated by the inner sleeve 102 to restrict fluid flow into the throughbore 46. The apparatus 100 is arranged such that the sandscreen sub attached to the pin end 36 has a region of slotted screen extending axially upstream in an upstream hydrocarbon zone of a formation. The sandscreen sub attached to the pin end 136 is arranged with a region of slotted screen in a separate downstream zone of the formation. Once the apparatus 100 is located downhole, hydrocarbons are absorbed by the swellable packer 42 to fluidly isolate the upstream and downstream reservoir zones.

When an operator wishes to move the apparatus 100 into the open configuration and initiate production through the sand screen subs, one or more of the pre-programmed RFID tags are weighted, if required, and dropped or flushed in to the well. One of the selectively coded RFID tags reaches the apparatus 100 that the operator wishes to actuate and travels through the throughbore 46 and the antenna 72 of the apparatus 100. During passage of the RFID tag through the RFID antenna 72, the antenna 72 charges the tag. The tag then transmits radio frequency signals allowing it to communicate with the RFID antenna 72. This data is processed by the electronics pack 7Op and the command to move the apparatus 100 into the open configuration is initiated. The electronics pack is electrically connected to the high resistance wire coil surrounding the Kevlar string 55 and on receipt of the command, an electric current is passed through the wire coil to thereby heat the high resistance wire to the temperature of approximately 400 degrees. This temperature is sufficiently high to melt the Kevlar string 55.

Once the Kevlar string 55 anchoring the outer tubular 104 to the inner sleeve 102 has melted, the restraint previously restricting movement of inner sleeve 102 relative to the outer tubular 104 is removed. As a result of the pressure differential created by the increased diameter 44 between the seals 34 relative to the diameter 55 between the sleeve seals 84, the inner sleeve 102 is urged by the high downhole pressure in the downstream direction to compress the air in the chamber 57. The inner sleeve 102 moves axially until a leading end of the inner casing 80 abuts the annular step 87 formed in the interior of the casing 130 and the inner tubular 150 abuts an annular step 137. As the inner sleeve 102 moves relative to the outer tubular 104, the inner tubular 50 urges the radial protrusion 62 against its inward bias and the protrusion 62 moves out of

the groove 65 to allow the inner sleeve 102 to move relative thereto. As the inner sleeve 102 is sliding down the throughbore of the outer tubular 104, the ring or circlip with the protrusion 62 slides on the outer surface of the inner sleeve, between the grooves 65 and 64. Once the inner sleeve 102 is in the open configuration the radially inwardly biased protrusion 62 locates in the other annular groove 64, located above the annular groove 65, and contracts radially to resist further relative movement of the inner sleeve 102 and the outer tubular 104. Movement of the apparatus 100 into its open configuration aligns the holes 40, 140 of the inner sleeve 102 with the ports 33, 133 respectively of the outer tubular 104 to allow fluid communication between the bores 32, 132 and the throughbore 46. The apparatus 100 is shown in its open configuration in Figures 2 and 7 to 9.

Once in the open configuration, production of hydrocarbons can commence through the sandscreen subs. Hydrocarbons from the upstream zone will flow in a downstream direction (denoted by arrows 108 in Figure 2) between the slotted screen and the ports 33. However, hydrocarbons from the downstream zone will flow in the upstream direction (denoted by arrows 107) between the slotted screen and the ports 133. Since the bores 132 through which flow occurs in the upstream direction are enclosed within the outer tubular 104, the potential for fluid flow dynamic problems is reduced. Once the produced hydrocarbons have passed through the ports 33, 133, they enter the throughbore 46 and flow in the downstream direction up the production tubing towards the surface.

According to the present embodiment, the outer tubular 104 and the inner sleeve 102 are typically manufactured from separate components that are joined to allow the movement of the inner sleeve 102 and the outer tubular 104 as a single component. However, the multi-piece inner sleeve 102

arrangement allows for a mechanical override to be built in to the apparatus 100 in the event that the remote signalling mechanism fails to melt the Kevlar string 55.

The mechanical override enables the inner sleeve 102 to be mechanically actuated so that it is moveable relative to the outer tubular 104. For example, a latch or fishing tool can be used to engage the inner sleeve 102 and the latch can be hammered, jarred or pulled to encourage failure of the anchor screw 54. The inner sleeve can be provided with a fishing neck or other formation to facilitate this. This action could remove the anchor between the inner sleeve 102 and the outer tubular 104 and allow relative movement of the inner sleeve 102 and the outer tubular 104. However, in normal use, the anchor screw 54 is designed to withstand hydrostatic forces typically experienced downhole and the normal range of dynamic forces associated with transportation and installation of the apparatus 100. Other mechanical fail safe override mechanisms can be inbuilt in the apparatus 100 to enable mechanical intervention in the event that the Kevlar string 55 fails to snap.

The present invention allows a single actuator to operate a sliding sleeve to control the flow of hydrocarbons through two sets of axially spaced ports 33, 133. To enable this development, the relative locations of the two sets of ports 33, 133 have been modified so that they are adjacent the common actuator. The apparatus 100 still allows hydrocarbons to be collected from different zones in a hydrocarbon formation because the location of the slotted screen extends axially from the apparatus 100 in opposing directions on either side. The apparatus 100 also includes a packer 42 that isolates the exterior of the production tubing between the ports 33, 133 and thus ensures that one set of ports 33 serves one area of the production zone and the other ports 133 serve another area of the

production zone. The result is a significant cost saving because a single actuator is required to operate and control a single inner sleeve 102 but still allows production from two discrete zones. Thus, the number of actuators required for a given number of sleeves 102 and porting arrangements is cut by half. This represents a significant cost saving.

Optionally, several tags can be programmed with the same operating instructions for each individual piece of apparatus 100 that is located downhole. Therefore it is likely that at least one of the tags will reach the desired antenna 72 enabling the operating instructions to be transmitted. Once the data is transferred, the other RFID tags with similar data can be ignored by the antenna 72. The tag may also be designed to carry data transmitted from antenna 72 enabling the tags to be recoded during passage through the RFID antenna 72. In particular, useful data such as temperature, pressure, flow rate and any other operating conditions can be transferred to the tag. The RFID antenna 72 can emit a radio frequency signal in response to the radio frequency signal received. This can recode the tag with information sent from the RFID antenna 72.

Optionally before running the apparatus 100 downhole, a timer within the electronics pack can be set so as to carry out the actuation command at a pre-determined time interval after the command is received. For example, the timer on the electronics pack can be sent to initiate actuation after one hour. Thus, one hour after receiving the actuation command from the pack, the inner sleeve 102 can be moved into the open configuration. The electronic pack processes the data received by the antenna 72 of the apparatus 100 as described above and recognises a flag in the data which corresponds to an actuation instruction data code stored on the electronics pack. Following the requisite time delay, the electronics pack then instructs the electronic circuit containing the coil to be completed and thus

passes current through the high resistance wire coil surrounding the Kevlar string 55.

Other methods of remote actuation of the apparatus can be used. For example, devices can be constructed to respond to pressure pulses such as mud telemetry. This is achieved by the positioning of the pressure sensor 52 within the throughbore 46. The pressure sensor 52 can also be electrically connected to the electronics pack to register a pressure signal as a command to pass current through the high resistance wire coil surrounding the Kevlar string 55.

Alternatively, the apparatus 100 could be constructed to respond to acoustic or electromagnetic signals. For example, different remote control methods of communication could be used such an acoustic signalling system offered by Halliburton, Oklahoma, USA or an electromagnetic wave system such as the cableless telemetry system offered by Expro Group of Verwood, Dorset, UK.

According to the above example, the inner sleeve 102 occupies an initial closed configuration and is subsequently moved to the open configuration. However, the inner sleeve 102 and the outer tubular 104 could be modified so as to allow the inner sleeve 102 to be moved into a variety of intermediate configurations in which the inner sleeve 102 partially obturates the ports 33, 133 to selectively restrict or choke but not completely stop the flow of fluids.

Modifications and improvements can be made without departing from the scope of the invention. The ports 33, 133 can be obturated by means other than a sleeve. For example actuation of the mechanism for moving the sleeve 102 between the closed and open configuration can cause

movement of a plate rather than the sleeve 102 to allow the ports 33, 133 to be selectively opened. A downhole power generator can provide the power source in place of the battery pack. A fuel cell arrangement can also be used as the power source.