Abstract: A debris removal system includes a tubular. A closure mechanism arranged to at least partially close an interior of the tubular. An injector mechanism having an exit arranged downhole of the closure mechanism; wherein debris removing material ejected from the injector mechanism is directable towards the closure mechanism. Also included is a method of removing debris in a downhole tubular.

Abstract: A completion assembly with a valve assembly for regulating fluid flow in a wellbore is disclosed. The completion assembly can include a base pipe with a sand screen. A flow control housing is disposed on one end of the sand screen. A first tubular port in the base pipe leads into the flow control housing, and a second tubular port is also formed in the base pipe. A flow path is formed within the flow control housing and communicates with both the base pipe and the inner annulus of the screen assembly. A valve assembly is located in the flow control housing and is in fluid communication with both the inner annulus and the base pipe. The valve assembly is positionable between multiple positions for controlling the flow through the flow control flowpath in response to fluid pressure applied to the second tubular port.

Abstract: A valve system has a main valve that is adjustable for output flow and pressure. The system also includes an output flow transducer, an output pressure transducer, and a fluid depth transducer. A microcontroller is operatively coupled to the valve, the output flow transducer, the output pressure transducer, and the fluid depth transducer. The microcontroller operates the valve to selectively control the output flow, the output pressure, and the fluid depth according to inputs received from a user.

Abstract: An intelligent completion system includes production tubing configured for production from multiple zones in a wellbore. At least one flow control valve is disposed on the production tubing for each of the multiple zones, this flow control valve capable to regulate the flow of a wellbore fluid into the production tubing. A chemical injection mandrel is disposed on the production tubing adjacent the at least one flow control valve in the each of the multiple zones, this mandrel being connected to at least one chemical injection line for injecting one or more chemicals into the wellbore. A control mechanism is connected to the at least one flow control valve and the chemical injection mandrel such that the injection mandrel and the at least one flow control valve are operated in a coordinated manner.

Abstract: A completion system including a barrier valve operatively arranged in a tubing string to selectively impede fluid flow through a lower completion. At least one control line is included for supplying a control line pressure for controlling operation of the barrier valve. The at least one control line is operatively arranged with the tubing string for enabling tubing pressure in the tubing string to determine the control line pressure. A method of operating a barrier valve is also included.

Abstract: A system for variably resisting flow of a fluid composition can include a flow passage and a set of one or more branch passages which intersect the flow passage, whereby a proportion of the composition diverted from the passage to the set of branch passages varies based on at least one of a) viscosity of the fluid composition, and b) velocity of the fluid composition in the flow passage. Another variable flow resistance system can include a flow path selection device that selects which of multiple flow paths a majority of fluid flows through from the device, based on a ratio of desired fluid to undesired fluid in the composition. Yet another variable flow resistance system can include a flow chamber, with a majority of the composition entering the chamber in a direction which changes based on a ratio of desired fluid to undesired fluid in the composition.

Abstract: Applying pulses to liquid being injected into wells makes the ground/liquid formation more homogenous, and more penetrative. A system for automatically creating the pulses is described, in which a piston is acted upon by the pressure differential (PDAF) between the supplied accumulator pressure and the formation pressure. The changing levels of the PDAF as the pulse-valve opens (and the PDAF falls) and as the pulse-valve closes (and the PDAF rises) are harnessed to actuate an inhibitor that restrain movement of the valve-piston, and delays opening and/or closing of the pulse-valve. The pulse-valve is engineered to open explosively, and thus create penetrative porosity-waves in the formation. The system includes a pressurized-gas accumulator, and injection-check-valve which can maintain pulsing even when the ground is not saturated, and the static injector, which allows non-pulsed injection only when the ground is non-saturated.

Abstract: A downhole tool comprising an inner sleeve with a plurality of sleeve ports and a housing positioned radially outwardly of the inner sleeve and having a plurality of housing ports, with the housing and inner sleeve partially defining a space radially therebetween. The space is occupied by a shifting sleeve. A fluid path extends between the interior flowpath of the tool and the space. A fluid control device, occupies at least portion of the fluid path, and may selectively permit fluid flow, and thus pressure communication, into the space to cause a differential pressure across the shifting sleeve. When a sufficient differential pressure is reached, the shifting sleeve is moved from a first position to a second position, which opens the communication paths through the housing and sleeve ports between the interior flowpath and exterior of the tool.

Abstract: A method for controlling the influx of fluids into a multizone well in which each inflow zone is provided with an inflow control device, comprises: assessing the flux of oil, gas, water and other effluents from the well; monitoring production variables, including ICD position and/or fluid pressure in each inflow zone upstream of each ICD and/or downstream of each ICD; sequentially adjusting the position of each of the ICDs and assessing the flux of crude oil, natural gas and/or other well effluents; monitoring production variables; deriving a zonal production estimation model for each inflow zone of the well; and adjusting each ICD to control the influx of crude oil, natural gas and/or other effluents into each inflow zone on the basis of data derived from the zonal production estimation model for each inflow zone of the well.

Abstract: A barrier valve system includes one or more barrier valves, a connection sub having a first portion and a second portion connecting one or more control lines to each other, and a replacement portion of the connection sub connectable to the first portion subsequent to retrieval of the second portion. The replacement portion has a port from an outside diameter of the replacement portion to an inside diameter of the replacement portion and seals disposed to define an annular space between the replacement portion and the first portion encompassing only valve opening ports in the first portion.

Abstract: A wellbore tubular port closure system includes a mechanism to delay the opening of the port after the port closure has been actuated to open. A method and apparatus incorporate the wellbore tubular port closure system with a port opening delay mechanism configured to act after actuation of the pressure responsive mechanism to delay full movement of the port-closure to the port-open position until after a selected time has lapsed.

Abstract: A downhole flow control device includes, a first member defining a first portion of a flow path, and a second member defining a second portion of the flow path, the flow path has a cross sectional flow area defined at least partially by the first member and the second member, a length of the flow path is greater than a largest dimension of the cross sectional flow area, and the cross sectional flow area is adjustable by movement of at least a portion of the first member relative to the second member.

Abstract: One or more embodiments of a selectively openable and closable downhole tool. The wherein, the downhole tool can include an outer tubular member having an annulus port formed therethrough. The downhole tool can also include an inner tubular member. The inner tubular member can include an inner port. The inner port and annulus port can be selectively aligned to form a flow path therethrough by moving the inner tubular member relative to the outer tubular member. The downhole tool can also include a logic drum configured to selectively move the inner tubular member. The downhole tool can also include a piston assembly configured to move the logic drum.

Abstract: A method of actuating a well tool includes the steps of: increasing pressure in a fluid line of a fluid metering device; closing a pilot-operated valve in response to the pressure increasing step; and discharging a predetermined volume of fluid from the metering device in response to the pressure increasing and valve closing steps. A fluid metering device for a well tool includes a piston separating chambers; and a pilot-operated valve which selectively prevents fluid communication between the chambers in response to at least a predetermined pressure being applied to a fluid line of the metering device, and which permits fluid communication through the valve between the chambers in response to pressure in the fluid line being less than the predetermined pressure. A greater pressure may be applied to the fluid line to thereby bypass the metering device and allow fluid to discharge from the line.

Abstract: A technique facilitates controlling flow in a wellbore. One or more flow control valve assemblies may be designed for coupling with downhole well equipment. Each flow control valve assembly comprises a flow control valve which cooperates with a control module. The control module comprises a plurality of electrically controlled valves arranged to control flow of actuating fluid to the flow control valve. Each flow control valve assembly also comprises a hydraulic override system to enable hydraulic actuation of the flow control valve to a predetermined position when, for example, no electrical power is available for the electrically controlled valves of the control module.

Abstract: An angled or inline choke for flowing drilling fluid to a choke and kill manifold, wherein the choke has a body with a bore, a connection can be sealed to the body and can have a connection bore in communication with the bore. A locking plate can index the connection to the body. The choke can have a cavity with a piston. A port can be in communication with the cavity to provide a hydraulic fluid to the piston. A choke bean in the bore can flow drilling fluid to the choke and kill manifold. A tip can connect to the choke bean with a rod. When the hydraulic fluid passes into the port, the piston can move within the bore and compress a choke element around the tip to cause restriction of the drilling fluid, enabling for control of a pressure of the drilling fluid.

Abstract: A downhole tool includes a pressure housing deployed in the bore of a drill collar. At least three fins are deployed on the housing and in the tool annulus. At least one of the fins includes a floating blade deployed thereon. The blade includes a plurality of radial pistons deployed therein. The pistons are configured such that the surface area of the radially outward facing piston surfaces is greater than the surface area of the radially inward facing piston surfaces. This piston configuration causes the surface area of the radially outward facing blade surface to be less than the radially inward facing blade surface. In operation, hydrostatic pressure exerts a differential force on the pistons and the floating blade thereby urging the pistons radially inward towards the housing and the blade radially outward towards the drill collar.

Abstract: A tool that is usable in a well and may include an operator, a switch, a resilient device and an indexer. The switch may be configured to selectively communicate a first force to the operator, thereby actuating the tool. The resilient device may exert a second force. The indexer may cycle through a sequence of positions in response to alternating between the second force and a third force. The sequence includes a predetermined position configured to actuate the switch, thereby communicating the first force to the operator to actuate the tool.

Abstract: The present invention refers to a wellhead valve system for adjusting the flow, for example, of hydrocarbon, comprising a hydraulic control valve (10) for opening the wellhead made up of a valve body (11) provided with a pipe (14,15) for the passage of a flow (F) of fluids, having an inlet opening (12) and an outlet opening (13), interposed between the inlet opening (12) and the outlet opening (13) being an adjustable orifice (16); an actuator (24) adapted to command the valve (10) to close and open, in which the actuator (24) operates on opening and closing means (20) of the adjustable orifice (16); and a position gauge (17) adapted to determine the degree of opening of the adjustable orifice (16), and is characterized in that the position gauge (17) is integral with the opening and closing means (20) of the adjustable orifice (16).

Abstract: An internal blowout preventer used in drilling rigs for the discovery and production of hydrocarbons from the earth is disclosed. The internal blowout preventer has two independently and remotely operable blowout preventer valves in the same body, providing for greater service life and higher reliability during drilling operations. The two valves are loaded into the internal blowout preventer housing from a single end, and are operable by an actuator assembly.

Abstract: The apparatus consists of a tubular housing carried into the well on a workstring. A series of spaced isolation modules is provided for each zone and carried into the well on a tubular conduit. The first, or most downstream module includes first and second sealing mechanisms to isolate the first zone to be treated. A full bore valve is provided that is activated to closed position by an activating component in response to a source of a first level of pressure to isolate the first zone from other parts of the well bore. A port within the housing is initially blocked but selectively opened concurrently with the activation of the first sealing means to manipulate the second sealing mechanism to fully isolate the selected zone and the module. As the module is activated, a second full bore valve is activated to seal the interior of the housing upstream of the first module by manipulation of the tubular string.

Abstract: A technique is provided for utilizing a hydraulic fluid metering control module in cooperation with a downhole component. The downhole component is shifted via hydraulic fluid delivered through first and/or second control lines to an actuator of the downhole component. The hydraulic fluid metering control module works in cooperation with the actuator and the control lines to enable shifting of the actuator according to a controlled, incremental process.

Abstract: A selectively communicatable hydraulic nipple is provided which includes an upper and lower communications component adapted to communicate with tools landed inside the hydraulic nipple. Each communications component communicates with a control line used by the hydraulic nipple. An operator is allowed to selectively communicate with tools landed inside the nipple via the upper and lower communications components via the nipple control line. As a result, should the TRSCSSV control line loose integrity, the operator has the option of utilizing the nipple control line to continue oil and gas production without the need for well modifications. Alternatively, an operator could land a chemical injection tool, with an injection string suspended therefrom, in the nipple and inject chemicals into the well via the nipple control line.

Abstract: Apparatus for controlling a downhole device such as a choke, the apparatus comprising a housing, a mandrel connected to the downhole device and moveable within the housing to move the device between different positions, and a detent mechanism to selectively lock the mandrel in one of the positions within the housing. The first and second positions are typically defined by physical stops on the apparatus such as shoulders, or dogs and grooves etc, and are typically placed at set positions that define the different configurations of the device. Thus, the movement of the downhole device is governed by the detent mechanism, rather than by variable factors such as pressure changes.

Abstract: A well system includes a valve interconnected in a casing string and selectively configurable between first and second configurations via a line external to the casing string, the valve in the first configuration being operable to selectively permit and prevent fluid flow between the casing string exterior and interior, and in the second configuration to selectively filter and prevent fluid flow between the casing string exterior and interior. A method of selectively stimulating a formation includes: positioning a casing string in a wellbore intersecting the formation, the casing string including a valve operable via an external line to selectively permit and prevent fluid flow between the casing string interior and exterior; and stimulating an interval set of the formation by opening the valve, flowing a stimulation fluid from the casing string into the interval set, and then configuring the valve to filter formation fluid which flows into the casing string.

Abstract: A method according to one or more aspects of the present disclosure comprises disposing a tool in a wellbore, the tool comprising a displacement unit for pumping a fluid at least partially through the tool, a first flowline hydraulically connected to the displacement unit through a valve network, and a second flowline hydraulically connected to the displacement unit; pumping a fluid from the first flowline to the second flowline; monitoring a pressure at a chamber of the displacement unit; and monitoring flowing pressure in the first flowline across the valve network from the displacement unit.

Abstract: A tool that is usable with a well includes a valve element, a mechanical operator, a pressure chamber and a regulator. The valve element has a first state and a second state. The mechanical operator responds to a predetermined signature in an annulus pressure relative to a baseline level of the annulus pressure to transition the valve element from the first state to the second state. The pressure chamber exerts a chamber pressure to bias the mechanical operator to transition from the second state to the first state. The baseline level is capable of varying over time, and the regulator regulates the chamber pressure based on the baseline level.

Abstract: An intelligent completion system includes a production tubing configured for production from multiple zones in a wellbore; at least one flow control valve disposed on the production tubing for each of the multiple zones, wherein the at least one flow control valve regulates flow of a wellbore fluid into the production tubing; a chemical injection mandrel disposed on the production tubing adjacent the at least one flow control valve in the each of the multiple zones, wherein the chemical injection mandrel is connected to at least one chemical injection line for injecting one or more chemicals into the wellbore; and a control mechanism connected to the at least one flow control valve and the chemical injection mandrel such that the injection mandrel and the at least one flow control valve are operated in a coordinated manner.

Abstract: Phase-controlled well flow control. A well system includes a flow control device which regulates flow of a fluid in the well system, the flow control device being responsive to both pressure and temperature in the well system to regulate flow of the fluid. A flow control device includes a flow regulator for regulating flow of a fluid through the flow control device, and an actuator which is operative to actuate the flow regulator in response to a predetermined relationship between a phase of the fluid and both pressure and temperature exposed to the actuator. A method of controlling a phase change of a fluid in a well system includes the steps of: flowing the fluid through a flow control device in the well system; and adjusting the flow control device in response to both pressure and temperature in the well system.

Abstract: A device or system for controlling fluid flow in a well includes a flow restriction member that transitions from a first effective density to a second effective density in response to a change in composition of the flowing fluid. The flow restriction member may increase in effective density as the water cut of the flowing fluid increases and/or disintegrate when exposed to a selected fluid in the flowing fluid. The flow restriction member may be formed of a water-absorbing material and/or a porous material. The pores may be water permeable but not oil permeable. A method for producing fluid from a subterranean formation includes controlling a flow of fluid into a wellbore tubular with a flow restriction member. The method may include reducing a flow of water into the wellbore tubular when a percentage of water in the flowing fluid reaches a predetermined value.

Abstract: Applying pulses to liquid being injected into wells makes the ground/liquid formation more homogenous, and more penetrative. A system for automatically creating the pulses is described, in which a piston is acted upon by the pressure differential (PDAF) between the supplied accumulator pressure and the formation pressure. The changing levels of the PDAF as the pulse-valve opens (and the PDAF falls) and as the pulse-valve closes (and the PDAF rises) are harnessed to actuate an inhibitor that restrain movement of the valve-piston, and delays opening and/or closing of the pulse-valve. The pulse-valve is engineered to open explosively, and thus create penetrative porosity-waves in the formation. The system includes a pressurized-gas accumulator, and injection-check-valve which can maintain pulsing even when the ground is not saturated, and the static injector, which allows non-pulsed injection only when the ground is non-saturated.

Abstract: A system and method for obtaining a clean fluid sample for analysis in a downhole tool are provided. In one example, the method includes directing fluid from a main flowline of the downhole tool to a secondary flowline of the downhole tool. While the fluid is being directed into the secondary flowline, sensor responses corresponding to the fluid in the secondary flowline are monitored to determine when the sensor responses stabilize. The secondary flowline is isolated from the main flowline after the sensor responses have stabilized. A quality control procedure is performed on the fluid in the secondary flowline to determine whether the captured fluid is the same as the fluid in the main flowline. Additional fluid from the main flowline is allowed into the secondary flowline if the captured fluid is not the same.

Abstract: Disclosed herein is a device for controlling flow within, e.g., a production well or an injection well. The device consists of a movable flow passage and a stationary variable choke or valve that is sensitive to flow parameters and automatically adjusts itself to provide a predetermined flow rate through the device.

Abstract: A marginal oil extraction system having an upper extraction unit, an extraction container, and a lower valve assembly. The marginal oil extraction system uses at least some of these components to cheaply extract oil from a stripper oil well. In some cases the system is capable of separating the oil from the water in the well with a solid barrier and can cheaply remove the oil from above the solid barrier. The system is cheap to install, easy to maintain and provides efficient access to what would otherwise be an inaccessible asset.

Abstract: A method and a device in connection with an actuator intended for use in connection with a fluid flow or fluid reservoir, in particular an actuator that is designed to be used in connection with a drainage pipe (8) for the production of oil and/or gas in an oil and/or gas reservoir. An osmotic cell (9) is used to operate the actuator (10). The osmotic cell is placed in the fluid flow, whereby the necessary force and motion for the actuator (10) to adjust or drive a fluid control device or valve are achieved by utilizing the osmotic pressure difference between the solution in the cell (9) and an external fluid flow/reservoir in relation to the cell.

Abstract: A method of actuating a well tool includes the steps of: increasing pressure in a fluid line of a fluid metering device; closing a pilot-operated valve in response to the pressure increasing step; and discharging a predetermined volume of fluid from the metering device in response to the pressure increasing and valve closing steps. A fluid metering device for a well tool includes a piston separating chambers; and a pilot-operated valve which selectively prevents fluid communication between the chambers in response to at least a predetermined pressure being applied to a fluid line of the metering device, and which permits fluid communication through the valve between the chambers in response to pressure in the fluid line being less than the predetermined pressure. A greater pressure may be applied to the fluid line to thereby bypass the metering device and allow fluid to discharge from the line.

Abstract: A downhole tool (10) comprises a body (12) defining a bore. The body includes a valve arrangement (18) including flow ports (24) in the wall of the body. The ports may be opened or closed. In addition, a variable flow restriction (30) is provided in the bore (14), the degree of restriction tending to decrease as flow across the restriction increases. The variable flow restriction may be utilized to actuate the valve arrangement.

Abstract: A hydraulic actuator is connected between a downhole tool and a hydraulic control line for operating the downhole tool through an actuation sequence. The hydraulic actuator comprises a valve shuttle section having an inlet port in connection with the hydraulic control line, a first function port and a second function port. The hydraulic actuator also has a shuttle movable between positions providing fluid communication between the inlet port and the first function port and the inlet port and the second function port. Additionally, the hydraulic actuator has a pilot assembly in fluid connection with the hydraulic control line and in operational connection with the shuttle. The pilot assembly is movable in response to an actuation cycle comprising applying pressure from the hydraulic control line and bleeding the pressure off.

Abstract: 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.

Abstract: A flow control valve for use in a downhole completion tubing string, where the control valve prevents cross flow between producing zones. The control valve comprises a housing forming a plenum therein, a tubular member having a perforated end disposed in the housing, and a plug assembly disposed in the end of the tubular member having perforations. The plug assembly comprises a shaft reciprocatingly disposed in the tubular member. Produced fluids flow within the tubular member, through the perforations to the plenum, and outside of the control valve through corresponding perforations formed in the disk and housing. When pressure in the completion tubing string exceeds produced fluid pressure, the plug will close thereby preventing fluid flow from the completion tubing to the tubular member.

Abstract: Apparatuses and methods for improving the reliability of pinpoint stimulation operations are disclosed. The pinpoint stimulation improvement apparatus includes an elastomeric element and a spring positioned on an inner surface of the elastomeric element. A flow limiter is coupled to the elastomeric element.

Abstract: Systems for operating one or more sliding sleeve valves in an incremental, step-type fashion between open and closed positions, permitting the valve or valves to be choked to progressively smaller flow areas. The systems of the present invention also permit the valve or valves to be fully closed without having to progress through incremental steps.

Abstract: A technique is provided for utilizing a hydraulic fluid metering control module in cooperation with a downhole component. The downhole component is shifted via hydraulic fluid delivered through first and/or second control lines to an actuator of the downhole component. The hydraulic fluid metering control module works in cooperation with the actuator and the control lines to enable shifting of the actuator according to a controlled, incremental process.

Abstract: A throttle valve (10), in particular for injecting a fluid into a geological formation, is described, which comprises a valve body (10) having a piston chamber (11), an annular piston (20) having a fluid channel (21), which extends from a high-pressure side (H) to a low-pressure side (L) of the throttle valve, with the annular piston (20) being displaceable within the piston chamber (11) and the fluid channel (21) being transmissive or closed depending on the position of the annular piston (20) in the piston chamber (11), and a cover plate (12) which is provided on the high-pressure side of the valve body (10) and through which the fluid channel (21) protrudes from the high-pressure side piston chamber (11), wherein the fluid channel (21) is closed in axial direction with a sealing disk (22) which can be rested tightly on the cover plate (12) on the high-pressure side, and the fluid channel (21) has a radial throttle opening (23) adjacent to the sealing disk (22).

Abstract: A SAGD system including a string defining an axial flow channel and an annular flow pathway, a fluid access structure between the axial flow channel and the annular flow pathway, and a valve disposed within the annular flow pathway. The valve being selectively closable to selectively inhibit annular flow in an uphole direction. A method for treating a SAGD formation.

Abstract: An embodiment of a method of shifting a valve between a plurality of flow condition positions, includes the steps of providing a mechanical indexer device in operational connection with a valve, the indexer device including a primary path defining a sequence through a plurality of valve positions at and between open and closed and a detent moveable along the primary path; providing at least one alternate path from a point along the primary path to a preceding position on the primary path along the sequence; shifting the valve to a subsequent position in the sequence; and shifting the valve to the preceding position in the sequence.

Abstract: Phase-controlled well flow control. A well system includes a flow control device which regulates flow of a fluid in the well system, the flow control device being responsive to both pressure and temperature in the well system to regulate flow of the fluid. A flow control device includes a flow regulator for regulating flow of a fluid through the flow control device, and an actuator which is operative to actuate the flow regulator in response to a predetermined relationship between a phase of the fluid and both pressure and temperature exposed to the actuator. A method of controlling a phase change of a fluid in a well system includes the steps of: flowing the fluid through a flow control device in the well system; and adjusting the flow control device in response to both pressure and temperature in the well system.

Abstract: An apparatus for controlling fluid flow between a wellbore tubular and a wellbore annulus includes a passage between a bore of the wellbore tubular and the wellbore annulus. The passage causes cavitations in a flowing fluid made up of mostly water. The cavitations activate a flow control device that controls fluid flow into the wellbore tubular. In one method, the flow control device includes a pressure chamber pressurized by high-pressure fluid associated with the cavitations. The pressure in the pressure chamber actuates a piston assembly coupled to a closure element that restricts fluid flow into the wellbore tubular. Alternatively, a power generator generates an electrical signal in response to the cavitations and transmits the electrical signal to the flow control device. In response to the electrical signal, the flow control element activates one or more devices that move a closure element to restrict fluid flow into the wellbore tubular.

Abstract: A float collar 10 includes a housing 12 and a generally sleeve-shaped elastomer 20. The lower plate 30 and an upper plate 32 are each supported on an elongate rod 22, and at least one of the plates is axially fixed relative to the tubular housing. The plate intended for exposure to fluid pressure includes a plurality of arcuate flow ports 34 for communication with the annulus between the tubular housing and the elastomer prior to swelling of the elastomer.

Abstract: An apparatus 30 for isolating at least a portion of a tubular for use in a wellbore comprising a first, inner tubular in the form of carrier tube 32 and a second, outer tubular in the form of protective shroud 34, coupled to the carrier tube 32. One or more aperture 46 is provided in a wall of the carrier tube 32 for permitting fluid transfer through the tube 32 and one or more aperture 50 is provided to permit fluid transfer through the shroud 34. A seal member in the form of a sealing layer 36 is disposed on a surface of the shroud 34, the sealing layer 36 defining a first configuration permitting fluid flow through the apertures 46,50 and, on exposure to a selected reactant, adopting a second configuration to restrict fluid flow through the apertures 46, 50, the sealing layer 36 adapted to return from the second configuration to the first configuration where concentration of the selected reactant falls below a selected threshold.