WO2019063985A1

WO2019063985A1 - Flow control tool

Info

Publication number: WO2019063985A1
Application number: PCT/GB2018/052718
Authority: WO
Inventors: Anthony Laplante; Steven Duthie NICOL; Kevin Black
Original assignee: Well Engineering Technology Fzco
Priority date: 2017-09-28
Filing date: 2018-09-25
Publication date: 2019-04-04
Also published as: GB201715678D0; EP3688268A1; EP3688268B1; GB2568226A

Abstract

A flow control tool (14) for controlling the flow of fluid in a wellbore (10) is disclosed. The tool comprises a hollow body (26) defining a through-bore (28) and at least one flow port (30) extending through a wall (31) of the body for selective communication with the through-bore, and a valve element (32) mounted within the through-bore of the body and movable within the through-bore under applied fluid pressure. The valve element is movable between a circulation flow position (Fig. 2) in which the valve element closes the through-bore of the body and allows fluid communication with the at least one flow port, and a through-bore flow position (Fig. 4) in which the valve element closes the at least one flow port and allows fluid flow along the through-bore of the body. The valve element is also Iocatable in a first intermediate position (Fig. 3) in which the at least one flow port is closed and fluid flowing into the body is directed along the through-bore and out of the body along a first intermediate flow path (44) defining a first intermediate flow area thereby providing a first intermediate pressure indication, and a second intermediate position (Fig. 7) in which the at least one flow port is closed and fluid flowing into the body is directed along the through-bore and out of the body along a second intermediate flow path (46) defining a second intermediate flow area which is different to the first intermediate flow area, thereby providing a second intermediate pressure indication which is different to the first intermediate pressure indication.

Description

FLOW CONTROL TOOL

The present invention relates to a flow control tool for controlling the flow of fluid in a wellbore. In particular, but not exclusively, the present invention relates to a flow control tool for controlling the flow of fluid in a wellbore, the tool comprising a hollow body defining a through-bore, and at least one flow port extending through a wall of the body for selective communication with the through-bore, the tool having a circulation flow position in which the through-bore is closed and fluid communication with the at least one flow port allowed, and a through-bore flow position in which the at least one flow port is closed and fluid flow along the through-bore allowed.

In the oil and gas exploration and production industry, wellbore fluids comprising oil and/or gas are recovered to surface through a wellbore which is drilled from surface. The wellbore is lined with metal wellbore-lining tubing, which is known in the industry as casing. The casing is cemented in place within the drilled wellbore, and serves numerous purposes including: supporting drilled rock formations; preventing undesired

ingress/egress of fluid; and providing a pathway through which further tubing and downhole tools can pass. It is frequently necessary to direct a flow of fluid from within a bore of a tubing located within the wellbore and out through a wall of the tubing, to an annular region. The annular region may be defined between an external wall of the tubing and an internal wall of a larger diameter tubing in which it is located (e.g. casing or liner), or between the external wall of the tubing and an internal wall of a surrounding rock formation.

The reasons for circulating flow to the annular region are many, and include: for performing a pressure test in the annular region, for example to ensure adequate setting of wellbore packers associated with the tubing; for assisting in the passage of drill cuttings from a drill bit to surface along the annular region (particularly in a deviated wellbore) entrained in drilling fluid; for varying a volume of fluid delivered along a through-bore of the tubing, for example when operating a fluid driven downhole motor provided at an end of the tubing; for circulating fluid to the annular region in an emergency situation, for example to pump higher density drilling fluid into the annular region to control an unexpected 'kick'; for directing 'lost-circulation' material into an unexpectedly porous (e.g. fractured) rock formation, to restrict loss of drilling fluid into the formation; and for activating other, fluid operated tools or equipment.

Many different flow control tools exist, which serve for controlling the flow of fluid between a tubing and the annular region surrounding the tubing. These tools generally comprise a hollow body defining a through-bore, and one or more flow ports extending through a wall of the body for selective communication with the through-bore. The tools are operable to move between a circulation flow position in which the through-bore is closed and fluid communication with the at least one flow port allowed, and a through-bore flow position in which the at least one flow port is closed and fluid flow along the through- bore allowed. One such prior flow control tool is disclosed in UK Patent Publication No. GB-2302895. This document discloses a tool comprising a tubular body for location in a tubular member, which defines a through-bore and a number of circumferentially spaced ports. A valve member in the form of a piston sleeve is mounted in the bore and is movable relative to the body between a first position in which fluid may flow through the port and a second position in which the valve member closes the port, the valve member being movable between the first and second positions by application of differential fluid pressure. This is achieved by varying a flow rate of fluid along a tubing coupled to the tubular member. Movement of the valve member is provided by a cam arrangement including a

circumferentially extending cam groove and a cam follower.

Whilst prior flow control tools such as that disclosed in GB-2302895 have provided an effective means of circulating flow to annulus when required, there is need for better information on the operating status of such tools, in particular, better information on a current position of the tool, enabling an operator to make a more informed decision on the consequences of varying a rate of flow of fluid through the tool. According to a first aspect of the present invention, there is provided a flow control tool for controlling the flow of fluid in a wellbore, the tool comprising:

a hollow body defining a through-bore, and at least one flow port extending through a wall of the body for selective communication with the through-bore; and

a valve element mounted within the through-bore of the body, the valve element being movable within the through-bore under applied fluid pressure between:

a circulation flow position in which the valve element closes the through- bore of the body and allows fluid communication with the at least one flow port, so that fluid flow along the through-bore and out of the body is prevented and fluid flowing into the body is directed through the at least one flow port; and

a through-bore flow position in which the valve element closes the at least one flow port and allows fluid flow along the through-bore of the body, so that fluid flow along the at least one flow port is prevented and fluid flowing into the body is directed along the through-bore and out of the body;

in which the valve element is locatable in:

a first intermediate position in which the at least one flow port is closed and fluid flowing into the body is directed along the through-bore and out of the body along a first intermediate flow path defining a first intermediate flow area, thereby providing a first intermediate pressure indication; and

a second intermediate position in which the at least one flow port is closed and fluid flowing into the body is directed along the through-bore and out of the body along a second intermediate flow path defining a second intermediate flow area which is different to the first intermediate flow area, thereby providing a second intermediate pressure indication which is different to the first intermediate pressure indication.

The present invention provides an operator with a better understanding of an operating status of the flow control tool than is available in prior tools. This is because the first and second intermediate pressure indications (which are generated when the valve element is in its respective first and second intermediate positions) provide information on the position in which the valve element is located. As will be described below, the valve member may transition through the intermediate positions during movement from the circulation flow position to the through-bore flow position. Accordingly, knowledge of the particular intermediate position that the valve element is in will provide an indication of the status of the tool during its movement between the circulation flow and through-bore flow positions (and thus the effect that a variation in a rate of flow of fluid supplied to the tool will produce).

Reference is made herein to the valve element closing the through-bore of the body, when in the circulation flow position. It will be understood that the valve element may substantially close the through-bore, in that fluid communication along the bore past the valve element may be substantially entirely (and optionally entirely) restricted. Similarly, reference is made to the valve element closing the at least one flow port of the body, when in the through-bore flow position. It will be understood that the valve element may substantially close the at least one flow port, in that fluid flow along said port is substantially entirely (and optionally entirely) restricted.

Whilst reference is made herein to the flow of fluid out of the tool along the at least one flow port, it will be understood that, once in the circulation flow position, the tool may not be dependent upon fluid pressure to maintain it in the circulation flow position, and so that return flow of fluid from an external location to within the bore of the hollow body may be possible. Thus the tool may serve for opening up fluid flow from an external location to within the body bore.

The flow control tool may have a particular use in the oil and gas exploration and production industry, and may be adapted to be located within a wellbore of an oil and/or gas well. The flow control tool may be a downhole tool. The flow control tool may be a circulation tool. The flow control tool may be adapted to be deployed into a wellbore on a string of tubing, which may be any tubing that can be deployed into a wellbore. Examples include a drill string, production tubing and a workover or tool string (a tubing 'string' comprising lengths of tubing coupled together end-to-end).

The valve element may be locatable in a further position in which the valve element partially closes the at least one flow port, so that there is a restricted flow of fluid along the at least one flow port. In this position of the valve element, fluid flow along the through- bore of the body may remain closed, or may be partially opened.

Reference is made herein to the generation of pressure indications. It will be understood that, in the context of the present invention (in which fluid is supplied into the through- bore of the tool at a particular flow rate), a 'back-pressure' can be measured within the fluid upstream of the tool, which is caused by the restriction that the tool presents to the flow of fluid along tubing carrying the tool. The supply of fluid into the through-bore of the tool applies a fluid pressure force on the tool. The back-pressure will vary depending upon the extent of the restriction that is presented, for a given flow rate of fluid. Thus the different flow areas of the first and second flow paths which are provided by the tool (depending upon whether the valve element is in the first or second intermediate position) will generate different, detectable back-pressures in the fluid upstream of the tool.

Recognising these different back-pressures enables information to be obtained relating to an operating condition of the tool.

The first and second intermediate pressure indicators may be increases in back-pressure (which may be referred to as pressure spikes) of fluid supplied to the tool. The pressure spikes may be detectable, for example by pressure monitoring equipment which may be located at surface. The first intermediate flow area may be greater than the second intermediate flow area. The second pressure indicator may therefore be higher than the first pressure indicator, and may be a higher increase in back-pressure (i.e. a higher pressure spike). The tool may be arranged so that movement of the valve element from the circulation flow position to the through-bore flow position requires a movement of the valve element to the first intermediate position. The tool may therefore be arranged to move sequentially from the circulation flow position, to the first intermediate flow position and then to the through- bore flow position. The tool may be arranged so that movement of the valve element from the through-bore flow position to the circulation flow position requires a movement of the valve element to the second intermediate position. The tool may therefore be arranged to move sequentially from the through-bore flow position, to the second intermediate flow position and then to the circulation flow position. The different pressure indications which are generated depending upon whether the valve element is in the first intermediate position or the second intermediate position can therefore be used to determine whether the tool is about to cycle to from the circulation flow position to the through-bore flow position, or vice-versa.

The tool may be arranged so that the valve element is cycled sequentially between: the circulation flow position; the first intermediate position; the through-bore flow position; the second intermediate position; and back to the circulation flow position. The tool may be arranged so that it is cycled through a further first intermediate flow position and back to the through-bore flow position prior to movement to the second intermediate position. This may provide an operator with additional redundancy, for example in the event that he or she is required to cycle the flow rate through the tool for an unrelated purpose, and which could otherwise cycle the tool back to the circulation flow position (which may not be desirable).

The circulation flow position of the valve element may be axially spaced along a length of the body from the through-bore flow position. The first intermediate position may be axially spaced along a length of the body from the second intermediate position. The first and second intermediate positions may both be axially spaced along a length of the body from the circulation flow position and/or the through-bore flow position. The valve element may be locatable in a plurality of first intermediate positions prior to return movement to the circulation flow position. The first intermediate positions may be at common axial positions along a length of the body, but may be circumferentially spaced.

In the through-bore flow position of the valve element, fluid may flow along a main flow path of a flow area which is greater than both the first and second intermediate flow areas. The main flow area may be a bypass flow area, which may bypass around a portion of the valve element. The main flow path, and/or the first and second flow paths, may extend along an exterior of the valve element, and may be defined between the exterior of the valve element and an interior of the hollow body, or a component disposed within the through-bore surrounding the valve element. The valve element may be at least partly hollow, and may be at least partly tubular. The valve element may comprise a bore extending in a direction along a length of the element. The bore may extend substantially parallel to a main axis of the element, and may be coaxial with the main axis.

The valve element may comprise a flow restrictor, which may be or may act as a choke. The flow restrictor may define an axial end of the valve element, or may be provided at or adjacent an axial end of the element. The flow restrictor may close an axial end of the bore of the valve element. In the circulation flow position of the valve element, the flow restrictor may close the through-bore of the body. In the through-bore flow position of the valve element, the fluid may bypass around the flow restrictor (and may flow along the main/bypass flow area). The tool may comprise a hollow flow directing component, which may form the component disposed within the through-bore surrounding the valve element. The flow directing component may be tubular, and may be generally annular. The flow directing component may cooperate with the flow restrictor to selectively close the through-bore. The hollow flow directing component may be disposed within the through-bore, and may be secured against movement relative to the body. The hollow flow directing component may be sealed relative to the body. In an alternative, the flow directing component may be defined by the hollow body. In the circulation flow position of the valve element, the flow restrictor may abut (and may optionally sealingly abut) the flow directing component to close the through-bore. The flow directing component may define the first intermediate flow path. The flow directing component may define a bore having a portion of a first diameter which forms a boundary of the first intermediate flow path. The flow directing component may define the second intermediate flow path. The flow directing component bore may have a portion of a second diameter which forms a boundary of the second intermediate flow path, the second diameter being different (optionally smaller) to the first diameter. The flow directing component may define the main/bypass flow path. The flow directing component may define a bore having a portion of a diameter which forms a boundary of the main flow path, the diameter optionally being greater than both the first and second diameters. The flow directing component may cooperate with the flow restrictor so that, depending upon the (axial) position of the flow restrictor within the flow directing component, fluid flowing along the through-bore flows through the main flow path, the first intermediate flow path, or the second intermediate flow path. The flow directing component may define at least one flow port, which is arranged to align with the at least one flow port of the hollow body. Where the hollow body comprises a plurality of flow ports, the flow directing component may comprise a corresponding number of flow ports, each one arranged to align with a corresponding one of the body flow ports. The flow directing component may define a channel which communicates with the at least one flow port of the body.

The valve element may comprise at least one flow port extending through a wall of the element, for permitting fluid communication between the through-bore of the body and the at least one flow port of the body. The valve element may comprise a plurality of flow ports. In the circulation flow position, the at least one valve flow port may open on to a channel extending around an external surface of the valve element, the channel communicating with the at least one flow port of the body. In this way, a rotational orientation of the valve element relative to the body may not impact upon fluid

communication between the body through-bore and the at least one flow port of the body. Where the valve element comprises a plurality of flow ports, the channel may facilitate communication with all of the flow ports. The at least one valve flow port may be disposed transverse to the valve element bore. When the valve element is in the through- bore flow position, the at least one valve element flow port may facilitate fluid a bypass flow of fluid around or past the valve element. In this position of the valve element, the at least one valve element flow port may communicate with the bore of the hollow flow component, so that fluid can bypass the flow restrictor.

The valve element may be biased towards the circulation flow position, and may be biased by a spring. The valve element may take the form of a piston. The valve element may be sealed relative to the body so that fluid directed into the bore imparts a fluid pressure force on the valve element to move the valve element within the through-bore. The tool may comprise a first seal of a first seal area for sealing the valve element relative to the body, and a second seal of a second seal area which is smaller than the first seal area, for sealing the valve element relative to the body. A differential pressure area may therefore exist between the spaced first and second seals, so that a fluid pressure force is imparted upon the valve element which tends to move (translate) the valve element within the body bore. Where the valve element is biased towards the circulation flow position, the fluid pressure force may act to counter a biasing force imparted upon the valve element.

The hollow body may be substantially tubular. The at least one flow port of the hollow body may be disposed transverse (optionally perpendicular) to the body through-bore.

The valve element may be translatable within the through-bore relative to the hollow body; The valve element may be rotatable within the through-bore relative to the hollow body.

The tool may comprise a control device for controlling a position of the valve element relative to the hollow body. The control device may be or may comprise a cam track and follower arrangement The cam track may be provided on one of an external surface of the valve element and an internal surface of the hollow body (or a component mounted within the bore of the hollow body), and the follower may be provided on the other one of the internal surface of the hollow body (or a component mounted within the bore of the hollow body) and the external surface of the valve element. The follower may engage within the cam track to control a position of the valve element. The cam track may extend around a circumference of the one of the external surface of the valve element and the internal surface of the hollow body (or component mounted within the bore of the hollow body). The cam track may be provided on or in a tubular member such as a sleeve, which is mounted to the valve element. The tubular member may be mounted for rotation relative to the valve element. This may avoid a requirement to rotate the valve element to move it between different positions. The follower may be a pin. The cam track may define a plurality of detents or restraints for the follower. The detents may be axially and/or circumferentially spaced. The cam track may comprise a circulation flow detent which may correspond to the circulation flow position of the valve element. When the follower is in the circulation flow detent, the valve element may be in the circulation flow position. The valve element may be urged to the circulation flow position, in which the follower is in the circulation flow detent. The cam track may comprise a through-bore flow detent. When the follower is in the through- bore flow detent, the valve element may be in the through-bore flow position. The valve element may be urged to the through-bore flow position under an applied fluid pressure force, against the biasing force. The cam track may define first and second intermediate detents. When the follower is in the first intermediate detent, the valve element may be in the first intermediate position. When the follower is in the second intermediate detent, the valve element may be in the second intermediate position. Where the valve element is locatable in further positions (e.g. further intermediate positions and/or further through- bore flow positions), the cam track may comprise further detent positions corresponding to each such further position. According to a second aspect of the present invention, there is provided a flow control tool for controlling the flow of fluid in a wellbore, the tool comprising:

a valve element mounted within the through-bore of the body, the valve element comprising:

a first axial end and a second axial end;

a bore extending from the first axial end in a direction along a length of the valve element, which bore communicates with the through-bore of the hollow body;

a flow restrictor which closes the second axial end of the bore;

at least one flow port extending through a wall of the valve element and which communicates with the valve element bore, the at least one flow port located between the first axial end of the valve element and the flow restrictor; in which the valve element is movable within the through-bore under applied fluid pressure between:

a circulation flow position in which the flow restrictor of the valve element closes the through-bore of the hollow body, and in which the valve element allows fluid communication between the through-bore of the hollow body and the at least one body flow port via the at least one valve element flow port, so that fluid flow along the through-bore and out of the body is prevented and fluid flowing into the body is directed through the at least one valve element flow port to the at least one body flow port; and

a through-bore flow position in which the valve element closes the at least one body flow port and allows fluid to bypass the flow restrictor, so that fluid flow along the at least one body flow port is prevented and fluid flowing into the body is directed along the through-bore and out of the body.

The tool may comprise a hollow flow directing component, which may be disposed within the body through-bore surrounding the valve element. The flow directing component may be tubular, and may be generally annular. The flow directing component may cooperate with the flow restrictor to selectively close the through-bore. The hollow flow directing component may be disposed within the through-bore, and may be secured against movement relative to the body. The hollow flow directing component may be sealed relative to the body. In an alternative, the flow directing component may be defined by the hollow body. In the circulation flow position of the valve element, the flow restrictor may abut (and may optionally sealingly abut) the flow directing component to close the through-bore. The flow directing component may define a first intermediate flow path. The flow directing component may define a bore having a portion of a first diameter which forms a boundary of the first intermediate flow path. The flow directing component may define a second intermediate flow path. The flow directing component bore may have a portion of a second diameter which forms a boundary of the second intermediate flow path, the second diameter being different (optionally smaller) to the first diameter. The flow directing component may define a main/bypass flow path. The flow directing component may define a bore having a portion of a diameter which forms a boundary of the main flow path, the diameter optionally being greater than both the first and second diameters. The flow directing component may cooperate with the flow restrictor so that, depending upon the (axial) position of the flow restrictor within the flow directing component, fluid flowing along the through-bore flows through the main flow path, the first intermediate flow path, or the second intermediate flow path. Further features of the flow control tool of the second aspect of the present invention may be derived from the text set out elsewhere in this document, in particular that relating to the first aspect of the invention.

In a further aspect of the present invention, there is provided a method of controlling the flow of fluid in a wellbore using the flow control tool of the first or second aspect of the invention. Further features of the method may be derived from the text set out elsewhere in this document, in particular that relating to the first and second aspects of the invention.

Embodiments of the present invention will now be described, by way of example only, in which:

Fig. 1 is a schematic side view of part of a wellbore into which a string of tubing has been deployed, the string of tubing comprising a flow control tool according to an embodiment of the present invention, for controlling the flow of fluid in the wellbore; Fig. 2 is a longitudinal cross-sectional view of the flow control tool shown in Fig. 1, drawn to a larger scale, the tool shown in the drawing with a valve element located in a circulation flow position in which fluid is circulated to an annular region exterior of the tool;

Fig. 2 A (presented on a separate sheet) is a view of the flow control tool of Fig. 2, sectioned about line A-A;

Fig. 2B is a view of a cam track forming part of a control device of the flow control tool shown in Fig. 2 (presented on a different sheet), the cam track shown opened up and so in a planar form; Fig. 3 is a view of the flow control tool which is similar to Fig. 2, but drawn to a smaller scale, and showing the valve element following movement to a first intermediate position, the drawing also showing part of a control device of the tool; Fig. 4 is a view of the flow control tool which is similar to Fig. 2, but drawn to a smaller scale, and showing the tool with the valve element in a through-bore flow position in which fluid is directed along a through-bore of the tool, the drawing also showing part of a control device of the tool; Fig. 5 is a view of the flow control tool which is similar to Fig. 2, but drawn to a smaller scale, and showing the valve element following movement to a further first intermediate position, the drawing also showing part of a control device of the tool;

Fig. 6 is a view of the flow control tool which is similar to Fig. 2, but drawn to a smaller scale, and showing the valve element following movement back to a through-bore flow position, the drawing also showing part of a control device of the tool;

Fig. 7 is a view of the flow control tool which is similar to Fig. 2, but drawn to a smaller scale, and showing the valve element following movement to a second intermediate position, the drawing also showing part of a control device of the tool;

Fig. 8 is a view of the flow control tool which is similar to Fig. 2, but drawn to a smaller scale, and showing the valve element following movement back to a circulation flow position, the drawing also showing part of a control device of the tool; and

Fig. 9 is an enlarged view of part of the flow control tool shown in Fig. 2.

Turning firstly to Fig. 1, there is shown a schematic side view of part of a wellbore 10 into which a string of tubing 12 has been deployed. The string of tubing comprises a flow control tool according to an embodiment of the present invention, the flow control tool indicated generally by reference numeral 14. The wellbore 10 is a wellbore of an oil and/or gas well, although the principles of the present invention may be employed in any other industry where it is desired to form a wellbore extending from surface into a rock formation or formations.

In the illustrated example, the string of tubing 12 is a drill string comprising a number of lengths of drill tubing 16 coupled together end-to-end, and which incorporates the flow control tool 14. The drill string 12 is shown during drilling of the wellbore 10, which typically involves rotating the drill string from surface to rotate a drill bit (not shown) provided lowermost on the drill string, to penetrate surrounding rock formations 18. As is well known in the oil and gas exploration and production industry, drilling fluid is pumped down the drill string 18 from surface, and serves numerous purposes including cooling the drill bit and transporting drill cuttings to surface along an annular region (or 'annulus') 20 defined between an exterior wall 22 of the string 12 and an internal wall 24 of the wellbore. In a variation, and as is again well know, the wellbore may be formed using a drill bit which is driven by a fluid driven motor (not shown) incorporated into the drill string 12, and which is driven by the drilling fluid that is pumped down the string from surface. In addition, whilst the present invention has been particularly shown and described in relation to a flow control tool 14 forming part of a drill string 12, the invention has a use in numerous other situations. For example, the flow control tool may be incorporated into any other type of tubing that can be deployed into a wellbore, and can be deployed into a wellbore which has already been lined with wellbore-lining tubing (casing and optionally also liner). Examples of suitable further types of tubing include production tubing, a workover string and a downhole tool string.

In the illustrated example, the flow control tool 14 acts to selectively direct drilling fluid into the annular region 20 to stimulate the flow of fluid along the annular region to surface (which may be of particular use in a deviated wellbore), and/or to perform other functions such as supplying lost-circulation material into a fractured formation. The flow control tool 14 is selectively operable to direct fluid to flow either along a through-bore of the tool, or through a flow port of the tool and into the annular region 20, as and when desired. However and as will be described below, the flow control tool 14 may also be arranged to direct part of the fluid flowing into the tool along the through-bore and part through the flow port.

The flow control tool 14 is shown in more detail in the enlarged longitudinal cross- sectional view of Fig. 2. The tool 14 generally comprises a hollow body 26 defining a through-bore 28, and at least one flow port 30 extending through a wall 31 of the body, for selective communication with the through-bore 28. In the illustrated embodiment, the tool 14 comprises four flow ports 30 spaced equidistantly around a circumference of the body 26. This is best shown in Fig. 2A (presented on a separate sheet), which is a view of the tool 14 sectioned about line A-A in Fig. 2.

The tool 14 also comprises a valve element 32 mounted within the through-bore 28 of the body 26, which is movable within the through-bore under applied fluid pressure. The valve element 32 is movable between numerous different positions, which will be described with reference also to Figs. 3 to 8, which are drawn to a slightly smaller scale than Fig. 2. Fig. 3 shows the valve element 32 following movement to a first intermediate position. Fig. 4 shows the valve element 32 in a through-bore flow position, in which fluid is directed along the through-bore 28 and out of the tool. Fig. 5 shows the valve element 32 following movement to a further first intermediate position. Fig. 6 shows the valve element 32 following movement back to a through-bore flow position. Fig. 7 shows the valve element 32 following movement to a second intermediate position. Fig. 8 shows the valve element 32 following movement back to a circulation flow position.

As will be described in more detail below, the valve element 32 of the tool 14 is movable between: the circulation flow position (shown in Figs. 2 and 8) in which the valve element closes the through-bore 28 of the body 26 and allows fluid communication with the flow ports 30, so that fluid flow along the through-bore 28 and out of the body 26 is prevented and fluid flowing into the body 26 is directed through the flow ports 30; and the through- bore flow position (shown in Figs. 4 and 6) in which the valve element 32 closes the flow ports 30 and allows fluid flow along the through-bore 28 of the body 26 (bypassing the valve element), so that fluid flow along the flow ports 30 is prevented and fluid flowing into the body 26 is directed along the through-bore 28 and out of the body. Accordingly, the tool 14 can be cycled between a position in which fluid communication along a length of the through-bore 28 of the body 26 is prevented and fluid entering the tool directed through the flow ports 30 (the circulation flow position), and a position in which fluid flow through the flow ports 30 is prevented and fluid entering the tool is directed along the length of the through-bore 28 and out of a lower end 34 of the tool 14. It will be understood that the lower end 34 of the tool 14 is that which is located further down the wellbore 10 from the surface during use and that, depending upon the geometry of the wellbore, the tool 14 may be located in a position in which it is deviated from the vertical, so that the lower end 34 is effectively closer to the surface. References to a lower (or upper) end of the tool 14 and any of its components should be interpreted accordingly.

In use, fluid is supplied down the drill string 12 to the tool 14, and enters the through-bore 28. The fluid is typically supplied from surface, and is pumped down the drill string 12 using suitable pumping equipment (not shown), which pumps the fluid down the string at a desired flow rate and pressure. A fluid pressure force is imparted upon the valve element 32, which serves for moving the valve element between the circulation flow position and the through-bore flow position (via the intermediate positions, as will be described below). Movement of the valve element 32 between the different positions is governed by a control device, indicated generally by reference numeral 36. In the illustrated embodiment, the control device 36 comprises a cam track 37 which is provided on an external surface 38 of the valve element 32, and a follower 40 extending from an internal surface of the body 26 and which engages in the cam track 37. It will be understood that this arrangement of the cam track 37 and follower 40 may, however, be reversed.

The cam track 37 is best shown in Fig. 2B (presented on a different sheet), where the cam track has been opened up and so is shown in a planar form. Suitably, the tool 14 comprises two followers 40, both of which engage in the cam track 37. This provides for secure engagement between the body 26 and the valve element 32. The position of the followers 40 within the cam track 37 governs the position of the valve element 32 relative to the body 26, and so an operating state of the tool 14. Movement of the valve element 32 between its different positions requires movement of the followers 40 along the cam track 37, which is achieved by varying the flow rate of the fluid that is pumped along the drill string 12 and into the tool 14, and so the fluid pressure applied to the valve element 32. In general terms, movement of the valve element 32 between the circulation flow and through-bore flow positions requires an increase in the flow rate of the fluid to shift the followers 40 along the cam track 37, followed by a decrease back to a lower flow rate. Accordingly, positive action is required in order to vary the flow rate and shift the valve element 32 between its different positions.

In contrast to prior flow control tools, the tool 14 of the present invention provides improved information on an operating state of the tool, enabling an operator to make an informed decision on any action to vary a flow rate of fluid through the tool, which will impact upon its operating state as described above. For example, when the tool 14 is arranged so that fluid is flowing to the annular region 20 along the flow ports 30 (Fig. 2), an increase in the flow rate of fluid supplied to the tool 14 will have the effect of shifting the valve element 32 away from the position that it adopts when flowing to the annular region, effectively closing off flow through the flow ports 30. Similarly, when the tool 14 is arranged so that fluid is flowing along the through-bore 28 and out of the tool 14 (Fig. 4), an increase in the flow rate of fluid supplied to the tool 14 will have the effect of shifting the valve element 32 away from the position that it adopts when flowing along the through-bore 28, effectively closing off flow along the length of the through-bore.

The present invention may improve upon prior flow control tools by providing pressure indications which can be detected by the operator, and which serve for indicating an operating state of the tool 14, in particular a position of the valve element 32.

This is achieved by arranging the valve element 32 so that it can be located in a first intermediate position, shown in Fig. 3, in which the flow ports 30 are closed and fluid flowing into the body 26 is directed along the through-bore 28 and out of the body. In this configuration, and as best shown in the enlarged view of Fig. 9, the valve element 32 presents a greater restriction to fluid flow through the tool 14 than it does when it is in the circulation flow position of Fig. 2.

When the valve element 32 is in this position, fluid flows along a first intermediate flow path, indicated generally by reference numeral 44, and out of the through-bore 28 at the lower end 34. The first intermediate flow path 44 has a first intermediate flow area, which is defined between the valve element 32 and the body 26. The first intermediate flow area defined by the flow path 44 is less than a total flow area defined by the flow ports 30, which total flow area is substantially the same as a flow area defined by a restriction in the form of a nozzle 45 positioned within the valve element 32. This has the result of presenting a restriction to flow of fluid through the tool 14, when compared to the circulation flow position of Fig. 2. This causes a back-pressure (or pressure 'spike') within the fluid in the drill string 12 upstream of the tool 14, which can be detected by the operator.

Movement of the valve element 32 to the position in which fluid flows through the first intermediate flow path thus provides a first intermediate pressure indication to the operator, which indicates that the valve element 32 has moved away from the circulation flow position. The operator knows that a subsequent reduction of the flow rate of fluid through the drill string 12 and into the tool 14 will reduce the fluid pressure force applied to the valve element 32, which will then move to its through-bore flow position (Fig. 4). The first pressure indication is therefore indicative of an imminent move from the circulation flow position (where fluid is directed out of the tool 14 to the annular region 20) to the through-bore flow position (where fluid flows along the length of the tool 14 and out of the through-bore 28 at the lower end 34 of the tool).

The valve element 32 is also arranged so that it can be located in a second intermediate position, shown in Fig. 7, in which the flow ports 30 are again closed and fluid flowing into the body 26 is directed along the through-bore 28 and out of the body. In this configuration, and as best shown in the enlarged view of Fig. 10, the valve element 32 presents a greater restriction to fluid flow through the tool 14 than it does when it is in both the through-bore flow position of Fig. 2 and the first intermediate position of Figs. 4 and 9. When the valve element 32 is in this position, fluid flows along a second intermediate flow path, indicated generally by reference numeral 46, and out of the through-bore 28 at the lower end 34. The second intermediate flow path 46 has a second intermediate flow area, which is again defined between the valve element 32 and the body 26.

The second intermediate flow area defined by the flow path 44 is less than a main, bypass flow area 48 defined when the valve element 32 is in the through-bore flow position, which is best shown in the enlarged view of Fig. 11. Again, the bypass flow area is substantially the same as a flow area defined by the nozzle 45. More significantly, the second intermediate flow area is also less than the flow area defined by the first intermediate flow path 44. This presents a relatively greater restriction to flow of fluid through the tool 14, when compared to both the through-bore flow position of Figs. 4 and 11, and the first intermediate position of Figs. 4 and 9. This causes a higher back-pressure (or pressure spike) within the fluid in the drill string 12 upstream of the tool 14 than when the valve element 32 is in the first intermediate position, which can again be detected by the operator.

This provides a second intermediate pressure indication to the operator, which indicates that the valve element 32 has moved away from the fully open through-bore flow position. The operator knows that a subsequent reduction of the flow rate of fluid through the drill string 12 and into the tool 14 will reduce the fluid pressure force applied to the valve element 32, which will then move to its circulation flow position (Fig. 2). The second pressure indication is therefore indicative of an imminent move from the through-bore flow position (where fluid flows along the length of the tool 14 and out of the through-bore 28 at the lower end 34 of the tool) to the circulation flow position (where fluid is directed out of the tool 14 to the annular region 20).

As will be evident from Figs. 2 to 8, the tool 14 is arranged so that it effectively defines more than one first intermediate position for the valve element 32, and more than one through-bore flow positions. In particular, the valve element 32 is shown in first intermediate positions in Figs. 3 and 5, and in through-bore flow positions in Figs. 4 and 6. Figs. 2 to 8 show sequential operating positions for the valve element 32. It will be appreciated from this that a cycling of the fluid flow rate (and so the fluid pressure force applied to the valve element 32) in the fashion described above will move the valve element sequentially from a circulation flow position (Fig. 2) to a first intermediate position (Fig. 3), a through-bore flow position (Fig. 4), a further first intermediate position (Fig. 5), a further through-bore flow position (Fig. 6), a second intermediate position (Fig. 7), and back to a circulation flow position (Fig. 8).

The inclusion of more than one first intermediate position for the valve element 32, and more than one through-bore flow position, provides an element of redundancy in the operating cycle of the tool 14. In particular, at a time when the tool 14 is in an operating state in which fluid is being directed along the through-bore 28 and out of the tool (the through-bore flow position of Fig. 4), an operator may be required to increase a flow rate of fluid through the tool (or there may be an unintentional increase in the flow rate). For example, an increase in flow rate may be required in order to perform some further function, such as actuation of a tool (not shown) located downstream of the flow control tool 14. Inclusion of the further first intermediate position and further through-bore flow position ensures that continued through-bore flow is not subsequently disrupted, avoiding a requirement to cycle the tool 14 back through the circulation flow state. Further such intermediate options may be included in the cycle, for example yet further first

intermediate and through-bore flow positions for the valve element 32.

The tool 14 and its method of operation will now be described in more detail. The valve element 32 is tubular, and takes the form of a generally hollow piston including an internal bore 50 which extends in a direction along a length of the piston from a first axial end 52. The bore 50 is substantially parallel to a main axis 54 of the piston, and is coaxial with the main axis. The piston is biased towards the circulation flow position of Fig. 2, suitably by a spring 56, which in the illustrated embodiment is a compression spring. The piston 32 is sealed relative to the body 26 so that fluid directed into the through-bore 28 flows into the piston bore 50, and imparts a fluid pressure force on the piston to translate the piston within the through-bore 28. A first seal 58 of a first seal area seals the piston 32 relative to the body 26 towards the first end 52. A second seal 60 of a second seal area which is smaller than the first seal area seals the piston 32 relative to the body 26 towards a second axial end 62 of the piston. A differential pressure area therefore exists between the axially spaced first and second seals 58 and 60, so that a net fluid pressure force is imparted upon the piston 32 which tends to translate it axially downward (to the right in the drawings) within the through-bore 28. References to a downward translation of the piston 32 should take account of the fact that the tool 14 may be located in a deviated wellbore in which the tool is deviated from the vertical. In use, when fluid is being supplied to the tool 14 through the drill string 12, the fluid pressure force that is imparted upon the piston 32 effectively acts to counter the biasing force imparted upon the piston by the spring 56. It will therefore be understood that a sufficiently high fluid flow rate (and so fluid pressure force) must be generated in order to counter the force of the spring 56. The hollow body 26 is substantially tubular, the through-bore 28 extending along the entire length of the body. The flow ports 30 are disposed transverse to the body through-bore 28, in particular to an axis 64 of the body 26, which is coaxial with the piston axis 54. In the illustrated embodiment, the flow ports 30 are disposed perpendicular to the axis 64, but may be inclined if desired, for example to promote flow in an uphole or downhole direction. The valve element 32 is translatable within the through-bore 28 relative to the hollow body 26. The piston 32 may also be rotatable within the through-bore 28, relative to the body 26. This may facilitate cycling of the piston 32 between its different operating positions, which requires the followers 40 to travel along the circumferentially extending cam track 37. As will be appreciated, the follower 40 would then effectively act to guide both axial translation and rotational motion of the piston 32 within the through-bore 28. However, in the illustrated embodiment, the cam track 37 is provided in a separate tubular member, in the form of a sleeve 39, which is mounted to the piston 32. The sleeve 39 is rotatable relative to the piston 32 (to accommodate movement of the follower 40 along the cam track 37), but secured against translation relative to the piston.

The piston 32 also comprises at least one flow port 66 extending through a wall 68 of the piston, for permitting fluid communication between the through-bore 28 of the body 26 and the body flow ports 30. In the illustrated embodiment, the piston 32 comprises four equidistantly spaced flow ports 66, which are best shown in the sectional view of Fig. 2A. The piston flow ports 66 are also inclined in a direction towards the second axial end 62 of the piston 32, to promote bypass flow when the piston is in the though-bore flow position of Fig. 4.

In the circulation flow position of the piston 32, the valve flow ports 66 open on to a circumferential annular flow channel 70 which extends around the external surface 38 of the piston, which channel communicates with the body flow ports 30 and the valve flow ports 66. In this way, a rotational orientation of the piston 32 relative to the body 26 does not impact upon fluid communication between the through-bore 28 and the body flow ports 30. When the piston 32 is in the through-bore flow position, the valve flow ports 66 facilitate a bypass flow of fluid around or past the piston. The circulation flow position of the piston 32 is axial ly spaced along a length of the body 26 from the through-bore flow position, in a direction away from a first axial end 72 of the body. The first and second intermediate positions of the piston 32 are axially spaced apart, and are axially spaced along the length of the body 26 from the first axial end 72 relative to both the circulation flow position and the through-bore flow position of the piston 32. As can best be seen by comparing Figs. 3 and 7, the second intermediate position of the piston 32 is spaced further along the length of the body 26 from the first axial end 72 than the first intermediate position. As will be described below, this facilitates generation of the different first and second pressure indications. In the through-bore flow position of the piston 32, fluid flows along a main flow path which has a flow area that is greater than both the first and second intermediate flow areas. This is best shown in the enlarged views of Figs. 9 to 11. The main flow area is a bypass flow area, which bypasses around a portion of the piston 32. The main flow path, and the first and second intermediate flow paths, extend along an exterior of the piston 32, and are defined between the external surface 38 of the piston 32 and an interior of the hollow body 26, suitably an interior of a component disposed within the through-bore 28 surrounding the piston 32. To this end, the tool 14 comprises a hollow flow directing component, indicated generally by reference numeral 74, which takes the form of a generally annular sleeve. The piston 32 also comprises a flow restrictor 76, which effectively acts as a choke, in certain operating positions of the piston 32 (in particular the first and second intermediate positions). The restrictor 76 defines an axial end of the piston, and effectively closes an axial end 78 of the piston bore 50. The restrictor 76 is suitably tapered, in particular at a lower end, to facilitate alignment within the body 26 in the various positions of the piston 32, and cooperation with the sleeve 74.

In the circulation flow position of the piston 32, the restrictor 76 closes the through-bore of the body. This is achieved by sealing abutment with a pair of seals 80 on the sleeve 74, as best shown in Fig. 2. The flow directing sleeve 74 effectively cooperates with the restrictor 76 to selectively close the through-bore 28. In contrast, in the through-bore flow position of the piston 32 (best shown in Fig. 11), the fluid bypasses around the restrictor 76, flowing along the main/bypass flow area.

The hollow flow directing sleeve 74 is disposed within the body through-bore 28, and is secured against movement relative to the body by pins 82. The sleeve 74 is sealed relative to the body 26 towards the lower end 34, by a seal 84. This ensures that fluid directed through the piston flow ports 66, when the piston is in the circulating flow position, is directed out through the body flow ports 30 and cannot migrate along an interface between the sleeve 76 and the body 26.

Referring again particularly to Figs. 9 to 11, it will be seen that the flow directing sleeve 74 effectively defines the main, first intermediate and second intermediate flow paths, in cooperation with the flow restrictor 76 of the piston 72. To this end, the flow directing sleeve 74 defines a bore 86 having a portion 88 of a first diameter Di which forms a boundary of the first intermediate flow path. The sleeve also has a bore portion 90 of a second diameter Th which forms a boundary of the second intermediate flow path, the second diameter being smaller than the first diameter Di. The sleeve further defines a bore portion 92 of a diameter D3 which forms a boundary of the main flow path, the diameter D3 being greater than both the first and second diameters Di and D₂. The sleeve 74 cooperates with the restrictor 76 so that, depending upon the axial position of the restrictor (and so the piston 32) within the sleeve 74, fluid flowing along the through-bore 28 flows through the main flow path, the first intermediate flow path, or the second intermediate flow path.

The flow directing sleeve 74 comprises a main part 75 defining the flow paths, and a locking part 77 which serves for securing the main part to the body 26 (via the pins 82), and which is sealed relative to the main part 75 via seals 79. As can be seen in Fig. 2A, the sleeve 74, in particular the locking part 77, defines at least one flow port 94, and in the illustrated embodiment includes four such equidistantly spaced ports. The sleeve flow ports 94 are arranged to align with the body flow ports 30. The sleeve 74, in particular the locking part 77, also defines the annular channel 70 which communicates with the piston flow ports 66, and effectively also with the body flow ports 30.

As discussed above, the tool 14 comprises a cam track and follower arrangement. The cam track 37 is provided in the sleeve 39, which is rotatable relative to the piston 32 but secured against translation. This is achieved by abutment between a shoulder 96 on the piston 32 and the spring 56. Rotation of the cam track sleeve 39 is facilitated by bearings 98 and 100 which straddle the sleeve.

The followers 40 take the form of pins, and the cam track 37 defines a plurality of detents or restraints for the followers. The detents are axially and/or circumferentially spaced, and are best shown in Fig. 2B. The detents are given the various reference numerals 102, 102a; 104 and 104a to c; 106 and 106a to c; 108 and 108a. The followers 40 are shown in the detent positions which they adopt, when the piston 32 is cycled through its different positions, in each of Figs. 2 to 8.

The cam track 37 comprises two circulation flow detents 102 and 102a, which correspond to the circulation flow position of the piston 32. When the followers 40 are in circulation flow detents 102 and 102a, the piston 32 is in the circulation flow position. The piston 32 is urged to the circulation flow position by the spring 56, in which the followers 40 are in the circulation flow detents 102 and 102a. The cam track also comprises through-bore flow detents 104 to 104c. When the followers 40 are in through-bore flow detents 104 to 104c, the piston 32 is in the through-bore flow position. The piston 32 is urged to the through-bore flow position under applied fluid pressure, against the biasing force of the spring 56, and then held in that position by the engagement of the followers 40 in the detents 104 to 104c.

The cam track also defines first intermediate detents 106 to 106c, and second intermediate detents 108 and 108a. When the followers 40 are in first intermediate detents 106 to 106c, the piston 32 is in the first intermediate position. When the followers 40 are in the second intermediate detents 108 and 108a, the piston 32 is in the second intermediate position.

In use, when the flow rate of fluid supplied to the tool 14 is cycled up and down as described above, the piston 32 is sequentially cycled between its various positions, governed by engagement of the followers 40 within the cam track 37.

Starting from the circulation flow position of Fig. 2, the followers 40 (which are spaced 180 degrees apart around the body 26) will be located in the detents 102 and 102a. Fluid entering the through-bore 28 flows down through the piston bore 50, and is directed out of the tool 14 into the annular region 20, via the aligned ports 66, 94 and 30. Flow along the through-bore 28 is shut-off.

Raising the flow rate of fluid to a level sufficient to overcome the force of the spring 56 will translate the piston 32 down, causing the followers 40 to move along track portions 110 and 110a to the first intermediate positions 106 and 106b, respectively. The piston 32 is then in the first intermediate position shown in Figs. 3 and 9. Fluid entering the through- bore 28 flows down through the piston bore 50, and bypasses around the restrictor 76, flowing through the ports 66 into and along the bore portion 88, and so along the first intermediate flow path and out of the through-bore 28 at the lower end 34 of the tool. This provides the first pressure spike, indicating to the operator that the tool is about to move the through-bore flow state, when the flow rate is reduced. Reducing the flow rate sufficiently will therefore cause the spring 56 to overcome the fluid pressure force, translating the piston 32 back in an upward direction. The followers 40 will then move along cam track portions 112, 112a to the through-bore flow detents 104, 104b. The piston 32 is then in the (fully open) through-bore flow position shown in Figs. 4 and 11. Fluid entering the through-bore 28 flows down through the piston bore 50, and bypasses around the restrictor 76, flowing through the ports 66 into and along the bore portion 92, and so along the main (bypass) flow path and out of the through-bore 28 at the lower end 34 of the tool. Raising and lowering the flow rate again cycles the piston 32 through the further intermediate position, in which the followers 40 are in the further first intermediate detents 106a and 106c, and from there to the further through-bore flow position, in which the followers 40 are in the further through-bore detent positions 104a and 104c. This provides the redundancy discussed above (which is optional).

Raising the flow rate of fluid to a level sufficient to overcome the force of the spring 56 again will translate the piston 32 down once more, causing the followers 40 to move along track portions 114 and 114a to the second intermediate positions 108 and 108a,

respectively. The piston 32 is then in the second intermediate position shown in Figs. 7 and 10. Fluid entering the through-bore 28 flows down through the piston bore 50, and bypasses around the restrictor 76, flowing through the ports 66 into and along the bore portion 90, and so along the second intermediate flow path and out of the through-bore 28 at the lower end 34 of the tool. This provides the second (higher) pressure spike, indicating to the operator that the tool is about to move back to the circulation flow state, when the flow rate is reduced.

Reducing the flow rate again will therefore translate the piston 32 back in an upward direction. The followers 40 will then move along the cam track portions 110, 110a and into the circulation flow detents 102, 102b. The piston 32 is then back in the circulation flow position of Fig. 2. The ability to generate pressure spikes providing an indication of an operating position of the piston 32, and so an operating condition of the tool 14, offers significant advantages over prior flow control tools. In particular, an operator has a good understanding of the impact that a variation in the flow rate of fluid supplied to the tool 14 will have, in terms of cycling the tool between circulation flow to annulus or along a through-bore of the tool to a location deeper in the well.

Various modifications may be made to the foregoing without departing from the spirit and scope of the present invention.

For example, whilst reference is made herein to the flow of fluid from within a through- bore of the tool to annulus, it will be understood that the tool may be employed for controlling the flow of fluid into the tool from the annulus. Such may be allowed once the tool has been located in its circulation flow position, by reducing the pressure of fluid in the string (for example by ceasing pumping). Similarly, flow along the tool along the through-bore from a location deeper in the well may be allowed.

The flow directing component may be defined by the hollow body, rather than provided as a separate component coupled to the body. This may be achieved by suitable machining or forming of an internal profile of the body bore.

Claims

1. A flow control tool for controlling the flow of fluid in a wellbore, the tool comprising:

in which the valve element is locatable in:

2. A flow control tool as claimed in claim 1 , in which the tool is arranged to move sequentially from the circulation flow position, to the first intermediate flow position and then to the through-bore flow position.

3. A flow control tool as claimed in either of claims 1 or 2, in which the tool is arranged to move sequentially from the through-bore flow position, to the second intermediate flow position and then to the circulation flow position.

4. A flow control tool as claimed in any preceding claim, in which the tool is arranged so that the valve element is cycled sequentially between: the circulation flow position; the first intermediate position; the through-bore flow position; the second intermediate position; and back to the circulation flow position.

5. A flow control tool as claimed in claim 4, in which the tool is arranged so that it is cycled through a further first intermediate flow position and back to the through-bore flow position prior to movement to the second intermediate position.

6. A flow control tool as claimed in any preceding claim, in which:

the circulation flow position of the valve element is axially spaced along a length of the body from the through-bore flow position;

the first intermediate position is axially spaced along a length of the body from the second intermediate position; and

the first and second intermediate positions are both axially spaced along a length of the body from the circulation flow position and the through-bore flow position.

7. A flow control tool as claimed in any preceding claim, in which the valve element is locatable in a plurality of first intermediate positions prior to return movement to the circulation flow position, the first intermediate positions being at common axial positions along a length of the body and circumferentially spaced around the body.

8. A flow control tool as claimed in any preceding claim in which, in the through- bore flow position of the valve element, fluid flows along a main flow path of a flow area which is greater than both the first and second intermediate flow areas.

9. A flow control tool as claimed in claim 8, in which the main flow area is a bypass flow area which bypasses around a portion of the valve element.

10. A flow control tool as claimed in either of claims 8 or 9, in which the main flow path and the first and second intermediate flow paths extend along an exterior of the valve element.

11. A flow control tool as claimed in claim 10, in which the flow paths are defined between the exterior of the valve element and an interior of the hollow body or a component disposed within the through-bore surrounding the valve element.

12. A flow control tool as claimed in any preceding claim, in which the valve element is at least partly hollow, comprising a bore extending in a direction along a length of the element, and in which the valve element comprises a flow restrictor which closes an axial end of the bore.

13. A flow control tool as claimed in claim 12 in which:

in the circulation flow position of the valve element, the flow restrictor closes the through-bore of the body; and

in the through-bore flow position of the valve element, the fluid bypasses around the flow restrictor.

14. A flow control tool as claimed in either of claims 12 or 13, comprising a hollow flow directing component which cooperates with the flow restrictor to selectively close the through-bore.

15. A flow control tool as claimed in claim 14 in which, in the circulation flow position of the valve element, the flow restrictor abuts the flow directing component to close the through-bore.

16. A flow control tool as claimed in either of claims 14 or 15, in which the flow directing component defines:

the first and second intermediate flow paths; and a bore having a portion of a first diameter which forms a boundary of the first intermediate flow path, and a portion of a second diameter which forms a boundary of the second intermediate flow path, the second diameter being different to the first diameter.

17. A flow control tool as claimed in claim 16, in which:

in the through-bore flow position of the valve element, fluid flows along a main flow path of a flow area which is greater than both the first and second intermediate flow areas;

and in which the flow directing component defines the main flow path, the bore of the flow directing component comprising a portion of a diameter which forms a boundary of the main flow path, said diameter being greater than both the first and second diameters.

18. A flow control tool as claimed in any one of claims 14 to 17, in which the flow directing component cooperates with the flow restrictor so that, depending upon the position of the flow restrictor within the flow directing component, fluid flowing along the through-bore flows through the main flow path, the first intermediate flow path, or the second intermediate flow path.

19. A flow control tool as claimed in any one of claims 14 to 18, in which the flow directing component defines at least one flow port which is arranged to substantially align with the at least one flow port of the hollow body.

20. A flow control tool as claimed in any preceding claim, in which the valve element comprises at least one flow port extending through a wall of the element, for permitting fluid communication between the through-bore of the body and the at least one flow port of the body, in the circulation flow position, the at least one valve flow port opening on to a channel extending around an external surface of the valve element, the channel communicating with the at least one flow port of the body.

21. A flow control tool as claimed in claim 20 in which, when the valve element is in the through-bore flow position, the at least one valve element flow port facilitates a bypass flow of fluid around the valve element.

22. A flow control tool as claimed in claim 21 , comprising a hollow flow directing component which cooperates with the flow restrictor to selectively close the through-bore, the at least one valve element flow port communicating with the bore of the hollow flow component when the valve element is in the through-bore flow position.

23. A flow control tool as claimed in any preceding claim, comprising a control device for controlling a position of the valve element relative to the hollow body, the control device comprising a cam track and follower arrangement, the cam track provided on one of an external surface of the valve element and an internal surface of the hollow body, and the follower provided on the other one of the internal surface of the hollow body and the external surface of the valve element.

24. A flow control tool as claimed in claim 23, in which the cam track comprises a circulation flow detent which corresponds to the circulation flow position of the valve element so that, when the follower is in the circulation flow detent, the valve element is in the circulation flow position.

25. A flow control tool as claimed in either of claims 23 or 24, in which the cam track comprises a through-bore flow detent which corresponds to the through-bore flow position of the valve element so that, when the follower is in the through-bore flow detent, the valve element is in the through-bore flow position.

26. A flow control tool as claimed in any one of claims 23 to 25, in which the cam track defines first and second intermediate detents, and in which, when the follower is in the first intermediate detent, the valve element is in the first intermediate position and when the follower is in the second intermediate detent, the valve element is in the second intermediate position.

27. A flow control tool for controlling the flow of fluid in a wellbore, the tool comprising: a hollow body defining a through-bore, and at least one flow port extending through a wall of the body for selective communication with the through-bore; and

a first axial end and a second axial end;

a flow restrictor which closes the second axial end of the bore;

28. A method of controlling the flow of fluid in a wellbore using the flow control tool of any preceding claim.