GB2545919A

GB2545919A - Apparatus and method

Info

Publication number: GB2545919A
Application number: GB1523095.6A
Authority: GB
Inventors: Edward Atkins James; Linklater James; Peter Buckland Jonathan
Original assignee: MI Drilling Fluids UK Ltd
Current assignee: MI Drilling Fluids UK Ltd
Priority date: 2015-12-30
Filing date: 2015-12-30
Publication date: 2017-07-05
Anticipated expiration: 2035-12-30
Also published as: GB201523095D0; GB2545919B

Abstract

A valve assembly for use in a wellbore the assembly having a valve seat 20 having a valve seat to be sealed by at least one closure member such as a ball 10a, wherein the valve seat comprises a first resiliently deformable seat member 21 and a second resiliently deformable seat member 22 such that the first seat member deforms to allow passage of the valve closure member at a fist threshold pressure retaining the valve closure member in a cleft between the first and second seat members until the second seat member resiliently deforms at a second threshold pressure which is higher than the first allowing passage of the valve closure member past the second seat member. The apparatus may comprise a control sleeve upon which the valve seat is provided such that pressure build up above the valve closure member causes movement of the sleeve against a spring 80 allowing alignment of fluid ports 52 & 72 until the valve closure member passes the valve seat.

Description

APPARATUS AND METHOD

The present application relates, generally, to an apparatus and method relating to a valve assembly and a method of controlling fluid flow in an oil, gas or water well. In particular, the application relates to a valve seat which is adapted to maintain engagement of a closure member with the valve seat.

BACKGROUND

The use of a plug that is released into the tubular of an oil, gas or water well and which then temporarily seals the bore of said tubular is known in the art as a means of controlling fluid flow downhole. The resulting build-up of fluid pressure is, in some cases, then utilised to actuate a tool further downhole, or alternatively to create jets of fluid into the annulus for cleaning or similar purposes.

In many cases the plug is released under gravity into the tubular and carried downhole under the flow of fluid from the surface, coming to rest on the valve seat below. Often the plug is deformable to provide a better seal between the plug and the seat. This deformation further allows for the plug to be forced through the valve seat in order to clear the central bore of the tubular and permit, for example, wireline tools to be passed through. The plug is generally expelled from the valve seat either under the action of fluid pressure alone, or in tandem with a smaller plug that is dropped after the first plug, and which has smaller dimensions, thus allowing the second plug to pass freely through the seat. US7,681,650 and WO01/90529 are useful for understanding the present apparatus and method.

SUMMARY

The present application discloses a valve assembly for use in a wellbore of an oil, gas or water well, the valve assembly having a bore with an axis, the assembly having a valve seat adapted to be sealed by at least one valve closure member, wherein the valve seat comprises a first seat member adapted to seat the at least one valve closure member in a first configuration, wherein the first seat member is adapted to resiliently deform from the first configuration to a second configuration to allow passage of the at least one valve closure member past the first seat member, and a second seat member adapted to seat the at least one valve closure member in a first configuration, wherein the second seat member is adapted to resiliently deform from the first configuration to a second configuration to allow passage of the at least one valve closure member past the second seat member, wherein the first and second seat members are axially spaced from one another at an axial distance, and wherein the seat is adapted to retain the at least one valve closure member between the first and second seat members.

The bore optionally allows passage of fluid through the valve assembly. The valve closure member optionally moves through the valve seat when subjected to fluid pressure differentials across the valve seat.

Optionally the seat members simultaneously urge the valve closure member in opposite axial directions from opposite axial ends of the valve closure member when the valve closure member is retained between the seat members. Optionally the first and second seat members are adapted to seat against the valve closure member at the same time, optionally on opposite sides of the valve closure member. Optionally the resilient action of the valve seat members urging the valve closure member from opposite axial directions resists movement of the valve closure member when engaged with the first and second seat members, and optionally keeps the valve closure member engaged with the seat, even in deviated or horizontal wellbores.

Optionally seating of the valve closure member on one or both of the first and second seat members closes the bore and prevents axial flow of fluid through the bore past the valve closure member on the seat member. Optionally each seat member circumferentially surrounds a portion of the valve closure member during deformation of the seat member, optionally maintaining a fluid-tight seal denying fluid passage between the seat members and the valve closure member when the valve closure member is seated, and optionally during the deformation of each seat member. Optionally each seat member is annular, having an inner diameter and an outer diameter which are optionally circular. Optionally the valve closure member moves through the annular seat members during deformation.

Optionally the first and second seat members can optionally comprise mutually parallel rings extending circumferentially around the inner surface of the control sleeve, and spaced apart axially by a short distance, optionally less than the diameter of the valve closure member, so that both of the seat members can engage the valve closure member at the same time when the valve closure member is seated.

Optionally the valve assembly has a closure member catcher device adapted to catch and retain valve closure members that have passed through the seat members.

An inner radial dimension of each seat member in the first configuration is optionally smaller than the maximal radial dimension of the valve closure member. Optionally in each seat member, the first configuration is the resting configuration in the absence of any forces applied to the seat member. Optionally the inner diameter of each seat member in the second configuration is larger than the inner diameter of the seat member in the first configuration.

The first and second seat members are optionally adapted to deform resiliently away from one another in opposite axial directions when the valve closure member is retained between them, and the first and second seat members are optionally adapted to press on the valve closure member from opposite axial directions to resist movement of the valve closure member relative to the seat when said valve closure member is retained between the first and second seat members. The resilience of the seat members is optionally adapted to maintain sealing engagement of the valve closure member against the seat when the valve closure member is retained between the first and second seat members.

Each seat member optionally maintains a consistent outer radial dimension in both of the first and second configurations, and during deformation. Optionally each seat member (and optionally the seat as a whole) is formed from a resilient material such that the inner radial dimension of each seat member optionally expands, optionally circumferentially during deformation and axial passage of the valve closure member through the seat member, such that the radial thickness and optionally the volume of the seat member (and optionally the seat) reduces transiently during deformation.

The inner diameter and radial thickness (and optionally the volume) of the first and second seat members (and the seat as a whole) optionally recover resiliently to the first configuration after axial passage of the valve closure member through the seat. The first and second seat members optionally extend radially inward from the inner surface of the bore. Optionally each seat member (and the seat) remains in a static axial position within the bore during deformation of the seat member.

Optionally the deformation of the seat member is an elastic deformation within the elastic limits of the seat member, which resiliently returns to its first configuration with its original inner and outer diameter after passage of the valve closure member through the seat member. Optionally the first seat member is disposed above the second seat member, and the second seat member has a higher elastic modulus than the first seat member. The second seat member can simply have a larger mass than the first and can be made of the same material, but in a stiffer structure less susceptible to deformation. Alternatively the second seat member can be made from a stiffer material than the first.

Optionally each of the first and second seat members extends radially inward from the inner surface of the bore. Each of the first and second seat members optionally has an upper surface and a lower surface. Each of the first and second seat members can optionally form a ring having a hemispherical profile, for example a convex annular bulge extending radially inwards into the bore on an inner surface of the bore. Optionally the upper surface and lower surfaces of the first and second seat members extend from the inner surface of the seat along an arcuate profile having a radius and meet in an apex at approximately the axial midpoint of each seat member. The apex can optionally comprise the narrowest part of a throat of the bore through the seat member. The seat members optionally meet at a cleft which has a wider radial diameter than the throat of the bore, so that the first and second seat members expand radially inwards into the bore from the wider cleft. Optionally the radius of the first and second seat members is constant. Optionally the radius of one is different from the other. Optionally the radius of the first seat member (optionally upstream from the second seat member) is smaller than the radius of the second seat member. Optionally the upper and lower surfaces of the first and second seat members terminate in angles that are generally larger than 90 degrees with respect to the axis of the bore.

Optionally the valve seat and the seat members are integrally formed from the same resilient material.

Optionally the valve assembly has a valve assembly housing, the housing optionally having a bore with an axis. Optionally the housing forms part of the wellbore conduit and is optionally connected by threaded connections to the wellbore conduit, optionally at each of the uphole and downhole ends. Optionally the axis of the valve assembly housing is coaxial with the axis of the wellbore. Optionally the axis of the valve assembly is coaxial with the axis of the housing.

The assembly optionally has at least one outlet port adapted to be actuated between open and closed configurations to permit and restrict fluid communication between the bore and an external surface of the valve assembly, for example, an annulus between the external surface of the assembly and the inner surface of a wellbore conduit of an oil or gas well. Optionally the outlet port extends radially through a wall, optionally through the wall of the valve assembly housing. Optionally the outlet port is obturated by a control sleeve which moves axially relative to the outlet port. Optionally the outlet port can slide axially within the bore, but in certain embodiments the outlet port remains static with respect to the bore and the control sleeve is a sliding sleeve which slides axially relative to the outlet port to open and close it. Optionally the control sleeve has an aperture which is adapted to move at least partially within the bore to control fluid communication with the outlet port. Thus the movement of the control sleeve relative to the outlet port is adapted to increase and/or decrease the degree of alignment of the outlet with the aperture on the control sleeve as the control sleeve moves relative to the outlet port. The degree of alignment between the aperture and the outlet can vary such that in some configurations, the outlet can be partially open (i.e. partially aligned with the aperture on the control sleeve) and in others it can be fully open (fully aligned with the aperture on the control sleeve). Optionally the control sleeve has seals (optionally annular seals above and below the aperture on the control sleeve) which seal off the outlet port from the bore when the control sleeve and outlet port are in the closed configuration. Optionally, the valve seat is provided in the control member, i.e. on the control sleeve.

Optionally the valve assembly comprises an outlet sleeve, which can be fixed relative to the outlet port, and which can include an aperture in fluid communication (and optionally aligned) with an inner end of the outlet port, whereby fluid passing through the outlet sleeve passes through the aperture therein, and thereafter through the outlet port, optionally flowing into the annulus outside the housing. The outlet sleeve is optionally fixed within the bore of the housing in a replaceable manner, and can be removed and replaced in the event of erosion of the aperture in the outlet sleeve. The outlet port is optionally sealed, optionally by resilient seals compressed between the outlet sleeve and outlet port. Optionally, the control sleeve is received within the bore of the outlet sleeve, and slides axially relative to the static outlet sleeve, which remains stationary relative to the outlet port.

Optionally more than one outlet port can be provided in the housing, and more than one corresponding aperture can be provided in the outlet sleeve and control sleeve.

Optionally the outlet sleeve is fixed in position by at least two fixing members. Optionally the fixing members are inserted radially inwards through the wall of the housing and into receiving holes in the outlet sleeve, thereby securing the outlet sleeve in position in the housing. Optionally the at least two fixing members are disposed on circumferentially opposing sides of the outlet sleeve. Optionally the fixing members are threaded. Optionally the outlet sleeve is restrained from both rotational and axial movement, optionally relative to the housing, and optionally relative to the other components of the valve assembly.

Optionally the first configuration of the valve assembly is a closed configuration. Optionally in the closed configuration, the outlet port through the valve assembly housing is closed off from the bore by the control sleeve, and all fluid flows through the central bore of the valve assembly, optionally unimpeded by a valve closure member. Optionally in the closed configuration fluid is prevented from flowing along the outer surface of the control sleeve, between the control sleeve and the outlet sleeve and into the radial ports by at least one circumferential seal, optionally more than one seal. Optionally the seals are annular seals. Optionally the seals are resilient seals, such as o-rings. Optionally the seals are metal-to-metal seals.

Optionally the valve assembly comprises a resilient device. Optionally the resilient device comprises a compression spring. Optionally the resilient device can be one of a coil spring; a Belleville spring; a wave spring, without excluding any other resilient device. Optionally the resilient device biases the valve assembly towards a closed configuration. Optionally the resilient device circumferentially surrounds at least a portion of the control sleeve and urges it axially within the bore. Optionally the resilient device is axially restrained at its uphole end by a circumferential shoulder or other portion of the control sleeve. Optionally the resilient device is held in compression within the bore of the housing between an upwardly facing lower shoulder fixed in the bore of the housing at a downhole end of the resilient device and a portion of the control sleeve at the upper end of the resilient device. Optionally the resilient device can engage against a spring retainer at either end of the resilient device, which can optionally engage the lower shoulder and the control sleeve. The spring retainer optionally circumferentially surrounds a portion of the control sleeve. Optionally the spring retainers centralise the control sleeve within the bore.

The control sleeve can optionally comprise a single sleeve, or an assembly of sleeves connected together to move together as a control sleeve assembly. The different features of the control sleeve can be provided on one or more of the assembly of sleeves in the control sleeve assembly.

In one example, the control sleeve can be fixed rotationally in the bore such that it moves axially with respect to the outlet port, but does not rotate relative to the outlet port.

Optionally the valve closure member comprises a ball, but could also comprise a dart, a bar or any other plugging device which can travel by gravity or with fluid flow through the bore to engage the seat and obturate fluid flow through the bore. Optionally the valve closure member has a generally spherical structure, and/or optionally a generally consistent sealing diameter to engage with the seat.

Optionally the valve closure member is non-deformable at the pressures used for the operation of the various examples, but could be deformable or at least partially comprised of a deformable material. Optionally there are two valve closure members. Optionally each valve closure member has the same sealing diameter. Optionally a first valve closure member has a larger diameter than a second valve closure member. Optionally the second valve closure member has an outer diameter adapted to pass through the seat members without seating the second valve closure member in the valve.

Optionally the profile of the first seat member comprises an arc, having a radius. Optionally the profile of the second seat member comprises an arc, having a radius. Optionally the first seat member is formed in an arc having a smaller radius than the second seat member. Optionally the second seat member is formed in an arc having a smaller radius than the first seat member. Optionally both seat members comprise arcs with the same radius.

Optionally at least one seat member, optionally the second seat member, and optionally both seat members, form a bore of optionally smaller diameter than the diameter of at least one valve closure member.

Optionally both of the seat members extend radially inwards from the inner surface of the control member, creating a throat in the seat, which is narrower than both the bore of the control member, and the valve closure member. Optionally the valve closure member has a diameter no larger than the inner diameter of the control member, and although it is retained by the seat, can pass freely through the remainder of the valve assembly without restriction.

Optionally the seating of the valve closure member in the seat causes a build-up of fluid pressure uphole of the valve assembly. Optionally the pressure acts in a downhole direction on the uphole surface of the valve closure member and on the seat. Optionally, at a first threshold pressure, the fluid pressure differential across the seated valve closure member overcomes the biasing force of the resilient device urging the control sleeve in the opposite direction (i.e. upwards) and the control sleeve optionally shifts axially downwards in the bore relative to the outlet port into an open configuration, optionally compressing the resilient device, while retaining the valve closure member in the seat. Optionally, in the open configuration, the control sleeve seats against a shoulder formed in the bore of the housing to limit the axial travel. Optionally the shifting of the control sleeve relative to the outlet port(s) into the open configuration connects the outlet port(s) with the bore, (optionally through the alignment of the apertures in the control sleeve and the outlet sleeve with the outlet port) allowing fluid flow from the bore through the outlet port(s). Although the first seat member has deformed to allow passage of the ball through it at the first threshold pressure, the second seat member below it has a higher shear force, and resists deformation at the first threshold pressure, thereby preventing passage of the ball through the second seat member, and retaining it between the first and second seat members, and sealing the throat. Thus at the first threshold pressure, the valve closure member is optionally retained in the seat and continues to obturate the bore of the valve assembly. The seat is optionally adapted to release the valve closure member in response to fluid pressure above the seated valve closure member at a second threshold pressure higher than the first threshold pressure. In one example, the control sleeve remains in the open configuration with the outlet port(s) in fluid communication with the bore subject to continued fluid pressure above the seated valve closure member. The force of the resilient device is optionally relatively weak, and the first threshold fluid pressure necessary to compress the spring is optionally below the second threshold fluid pressure necessary to deform the seat members and drive the seated valve closure member through the seat. Hence, at the first threshold pressure, the bore is obturated by the valve closure member, which remains in the seat when the valve is in the open configuration.

When the valve is to be closed, optionally closure of the radial ports is achieved by admitting (e.g. dropping) a second, third, or further valve closure member(s) into the bore, e.g. from surface. Optionally the travel of the further valve closure member is halted by the first valve closure member retained in the bore between the first and second seat members. The axial spacing between the seat members and the radial ports is optionally adapted for the dimensions of the valve closure members, such that when the further valve closure member engages with the valve closure member retained between the seat members, the further valve closure member seals off or substantially restricts the bore, advantageously at a location uphole of the radial outlet ports, optionally preventing any diversion of fluid flow through the radial outlet ports. Optionally, the choking of fluid flow in the bore leads to a build-up of fluid pressure to a second pressure threshold uphole of the further valve closure member. Optionally this fluid pressure can be further increased from the surface pumps as required. Optionally this increased fluid pressure to the second pressure threshold acts on the further valve closure member and urges it in a downhole direction. The further valve closure member optionally in turn presses down on the valve closure member retained between the seat members. Optionally this results in the downhole valve closure member retained between the seat members being forced through the second seat member, which optionally deforms into the second configuration as the valve closure member passes through it. Optionally, the further valve closure member has a smaller outer diameter than the inner diameter of the seat members, and hence can pass through the valve seat without seating. Optionally the valve closure members are then caught in the closure member catching device further downhole.

Optionally the expulsion of all the valve closure members relieves the pressure on the resilient device in the valve assembly and results in the valve assembly returning to its first, closed configuration, with fluid travelling axially through the bore rather than radially through the outlet ports.

In one example, the outlet sleeve of the valve assembly comprises a leading edge at its uphole facing end. Optionally this leading edge is formed as a circumferential chamfered shoulder extending radially inwards into the bore. The shoulder optionally has a maximum diameter at its uphole end, and optionally narrows in diameter towards its downhole end, optionally to at least the same internal diameter as the bore of the control sleeve, such that the leading edge forms a funnel, having a throat that narrows to a diameter at its downhole end that is at least as narrow as the inner diameter of the bore of the control sleeve. Optionally the leading edge is formed on a cap, which is optionally threadedly connected to the outlet sleeve.

One effect of the leading edge is to reduce the thrust acting on the moving part of the valve (i.e. the control sleeve) in the downhole direction. The restriction in the inner diameter of the chamfered shoulder acts to reduce the drag forces experienced by the downhole portion of the valve assembly. Pressure experienced by the uphole face of the valve assembly is correspondingly reduced in this arrangement relative to the pressure experienced by the assembly when a leading edge is not formed in the fixed sleeve. Thus the arrangement is less sensitive to accidental actuation without a valve closure member being seated in the bore.

The leading edge increases the velocity of the fluid and correspondingly decreases the fluid pressure, in accordance with Bernoulli’s principle.

The present application also discloses a method of diverting fluid flow in a wellbore of an oil, gas, or water well, the method including flowing fluid through a valve assembly comprising a bore with an axis, and a valve seat having first and second seat members, the bore being in fluid communication with the wellbore; admitting a valve closure member into the valve assembly; resiliently deforming the first seat member to allow passage of the at least one valve closure member past the first seat member; seating the valve closure member on the valve seat in the valve assembly; and retaining the valve closure member seated on the seat between the first seat member and the second seat member.

Optionally the closure of the bore of the valve assembly by the valve closure member actuates the valve assembly from a first configuration (optionally axial flow) to a second configuration (optionally radial flow of fluid through a radial outlet port in a side wall of the valve assembly.

Optionally the first and second seat members are axially spaced from one another at an axial distance adapted to retain the at least one valve closure member between the first and second seat members.

Optionally the valve closure members are dropped down the wellbore, or can be released from above the seat from another location within the well. They fall under gravity or are carried by fluid flow towards the valve seat.

The various optional features of the valve assembly as defined above can be used with the method.

Examples of the present apparatus and method are particularly useful in highly deviated wells, as once seated the ball remains engaged in the seat and obturates the bore regardless of the orientation of the borehole, and regardless of the force of fluid pressure from uphole. Retention of the seal helps to avoid premature disengagement of a downhole tool, or and improves consistency of cleaning in the annulus in circulation examples.

The various aspects of the apparatus and method disclosed herein can be practiced alone or in combination with one or more of the other aspects, as will be appreciated by those skilled in the relevant arts. The various aspects can optionally be provided in combination with one or more of the optional features of the other aspects of the apparatus and method. Also, optional features described in relation to one aspect can typically be combined alone or together with other features in different aspects. Any subject matter described in this specification can be combined with any other subject matter in the specification to form a novel combination.

Various aspects of the apparatus and method will now be described in detail with reference to the accompanying figures. Still other aspects, features, and advantages of the present apparatus and method are readily apparent from the entire description thereof, including the figures, which illustrates a number of exemplary aspects and implementations. The apparatus and method is also capable of other and different examples and aspects, and its several details can be modified in various respects, all without departing from the spirit and scope of the present disclosure.

Accordingly, each example herein should be understood to have broad application, and is meant to illustrate one possible way of carrying out the apparatus and method, without intending to suggest that the scope of this disclosure, including the claims, is limited to that example. Furthermore, the terminology and phraseology used herein is solely used for descriptive purposes and should not be construed as limiting in scope. Language such as "including", "comprising", "having", "containing", or "involving" and variations thereof, is intended to be broad and encompass the subject matter listed thereafter, equivalents, and additional subject matter not recited, and is not intended to exclude other additives, components, integers or steps. Likewise, the term "comprising" is considered synonymous with the terms "including" or "containing" for applicable legal purposes. Thus, throughout the specification and claims unless the context requires otherwise, the word “comprise” or variations thereof such as “comprises” or “comprising” will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.

Any discussion of documents, acts, materials, devices, articles and the like is included in the specification solely for the purpose of providing a context for the present disclosure. It is not suggested or represented that any or all of these matters formed part of the prior art base or were common general knowledge in the field relevant to the present disclosure.

In this disclosure, whenever a composition, an element or a group of elements is preceded with the transitional phrase "comprising", it is understood that we also contemplate the same composition, element or group of elements with transitional phrases "consisting essentially of”, "consisting", "selected from the group of consisting of”, “including”, or "is" preceding the recitation of the composition, element or group of elements and vice versa. In this disclosure, the words “typically” or “optionally” are to be understood as being intended to indicate optional or non-essential features of the apparatus and method which are present in certain examples but which can be omitted in others without departing from the scope of the disclosure.

All numerical values in this disclosure are understood as being modified by "about". All singular forms of elements, or any other components described herein are understood to include plural forms thereof and vice versa. References to directional and positional descriptions such as upper and lower and directions e.g. “up”, “down” etc. are to be interpreted by a skilled reader in the context of the examples described to refer to the orientation of features shown in the drawings, and are not to be interpreted as limiting the apparatus and method to the literal interpretation of the term, but instead should be as understood by the skilled addressee. In particular, positional references in relation to the well such as “up” and similar terms will be interpreted to refer to a direction toward the point of entry of the borehole into the ground or the seabed, and “down” and similar terms will be interpreted to refer to a direction away from the point of entry, whether the well being referred to is a conventional vertical well or a deviated well.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

Figure 1 shows a cutaway view of a valve assembly in a first (outlet port closed and central bore open) configuration with no valve closure member seated;

Figure 2 shows the valve assembly of Figure 1 with a first valve closure member seated on the valve seat;

Figure 3 shows the valve assembly of Figure 2 with a further valve closure member disposed uphole of and abutting the first valve closure member;

Figure 4 shows a perspective view of a control sleeve of the Figure 1 assembly;

Figure 5 shows a view along the axis of the valve assembly;

Figure 6 shows an axial view of a valve seat of the Figure 1 assembly;

Figure 7 shows a side view of the valve seat;

Figures 8-10 show views of a second example of a valve assembly similar to Figures 1-3.

DETAILED DESCRIPTION

Referring to the drawings, which show an example of a valve assembly 1 for use in a wellbore of an oil, gas or water well, comprises a housing 50 which can be in the form of a tubular having box and pin connections or similar, and adapted to be connected into a string of tubulars, for example a drill string, having a drill bit at the lower end. The housing 50 has a bore 50b in fluid communication with the bore of the string, and the bore 50b houses a number of valve components optionally in the form of sleeves. In this example, the bore 50b has an outlet sleeve 70 and a control sleeve 60. The outlet sleeve 70 at least partly surrounds a portion of a control sleeve 60, which has a bore 1 b with an axis that is generally co-axial with the bore 50b of the housing and the bore of the outlet sleeve 70. The bores of the sleeves 60, 70 are in fluid communication with the bore 50b of the housing 50. The outlet sleeve 70 provides a replaceable “hanger” in the bore for the connection of the other components, and protects the outlet port 52 from erosion damage. It can be readily removed and replaced when damaged by erosion, or if a different size of inner bore is needed.

The valve assembly 1 comprises a resilient device, in this example in the form of a compression spring 80 which circumferentially surrounds a downhole end of the control sleeve 60, and is held in compression to bias the control sleeve 60 upwards in the bore into a first configuration as shown in Figure 1, in which the bore is open and the outlet port 52 is closed. In the first configuration shown in Figure 1, the spring 80 is held in compression between an optional spring retainer 85 surrounding the control sleeve 60 at the spring’s downhole end and abutting against an upwardly facing shoulder in the bore (optionally formed by a sleeve in the bore), and a radially outwardly extending shoulder 61 of the control sleeve 60 at its uphole end. The spring 80 is optionally preloaded in compression in the Figure 1 state, and urges the control sleeve 60 in an uphole direction within the bore 50b until it abuts a lower end of a downhole-facing shoulder on the outlet sleeve 70, which limits its further axial travel within the bore 50b in the uphole direction. The spring 80 can be compressed further as will be described below.

The control sleeve 60 is adapted to slide axially in the bore 50b, to open and close at least one alternative fluid pathway in the assembly, in this example to divert the fluid flowing through the bore 50b of the housing and the bore 1b of the control sleeve 60 and out into the annulus of the wellbore, through an outlet port 52 in the housing 50. The outlet sleeve 70 is fixed in the bore 50b across the outlet port 52, and has an aperture 72 in the outlet sleeve which is in fluid communication with the outlet port 52. In the first configuration shown in Figure 1, the control sleeve 60 is positioned within the housing 50 such that an aperture 62 through the control sleeve 60 is out of alignment with the aperture 72 on outlet sleeve 70, closing off fluid communication between the bore 50b and the outlet port 52, and maintaining axial fluid flow F^ with the direction of flow as illustrated by the arrow, in a downhole direction within the bore 1b of the control sleeve.

The outlet sleeve 70 is fixed in both rotational and axial position by fixing members in the form of pins 54, which are inserted through the wall of the housing 50, into receiving bores in the outlet sleeve 70. The pins 54 can be removed in order to facilitate removal and replacement of the outlet sleeve 70 when necessary, for example in the event of erosion of the aperture 72. The pins 54 further extend radially inwards to engage the outer surface of the control sleeve 60, and are adapted to be received in axial slots in the outer surface of the control sleeve 60 in the bore of the outlet sleeve 70, to restrict rotational movement of the control sleeve 60 while permitting relative axial movement of the control sleeve 60 within the housing 50.

The outlet port 52 of the valve assembly 1 is actuated between open and closed configurations to permit and restrict fluid communication between the bore of the valve assembly 50b and an external surface of the valve assembly. When the outlet port 52 is in the closed configuration shown in Figure 1, the outlet port 52 is obturated by the control sleeve 60, which is urged axially upwards relative to the outlet port 52 to cover it in the first configuration. Annular seals are optionally compressed between the outlet sleeve 70 and the control sleeve 80 in axial positions above and below the outlet port, so that in the closed configuration in Figure 1, the control sleeve seals off all fluid communication between the bore 1b and the outlet port 52. The control sleeve 60 has at least one and in this case, two apertures 62 which pass radially through a wall of the control sleeve 60 at the same axial location on the control sleeve 60, and which are spaced diametrically from one another around the circumference of the control sleeve 60. When the control sleeve 60 is in the first configuration shown in Figure 1, the apertures 62 are above the apertures 72, out of axial alignment with the outlet port 52, and in this configuration, the outlet port 52 is closed and the fluid flowing through the bore 50b above the valve assembly 1 flows through the bore 1b of the control sleeve and on through the tubular string to the drill bit in a generally unobstructed manner.

When the outlet port 52 is to be opened and fluid flow is to be diverted to the outlet for example in a circulation operation, the control sleeve 60 moves axially down the bore from the first, configuration shown in Figure 1, with axial fluid flow F^ to the second configuration with radial fluid flow F2, as shown in Figure 2 to open the outlet port 52 as will be described below. The axial travel of the control sleeve 60 can result in the outlet port 52 being fully open (as shown in Figure 2), fully closed (as shown in Figure 1), or partially open (an intermediate position between the two).

In this example, the control sleeve 60 further comprises a valve seat 20 situated below the outlet sleeve apertures 62. When the control sleeve 60 is in the first configuration of Figure 1 and the outlet port 52 is closed the valve seat 20 does not offer any substantial obstruction of the fluid flow through the bore 1b. The valve seat 20 is adapted to be sealed by at least one valve closure member, for example, a ball, a dart, a plug etc, and has first and second seat members as will be described below. The valve closure member is normally dropped from surface or otherwise released into the tubular above the seat 20, and travels with the fluid flow in a downhole direction to the seat 20, where its further axial travel in the bore 50b is prevented, and it closes or substantially obturates the bore of the control sleeve 60 by seating on the seat 20. Figure 2 shows the valve assembly 1 of Figure 1, with a first valve closure member in the form of a first ball 10a seated on the valve seat 20, and in which the control sleeve 60 has travelled axially in the bore 50b under the force of the fluid pressure above the seated ball 10a to uncover the outlet port 52 by aligning the aperture 62 with the aperture 72 and the outlet port 52, so that the bore 50b is in fluid communication with the outlet port 52, and fluid is diverted by the seated ball 10a through the outlet port 52 rather than down the bore 1b of the control sleeve and onwards through the tubular string to the drill bit below the valve assembly 1.

The seat 20 has first and second seat members 21,22 in the form of parallel annular rings spaced apart by a short distance, optionally less than the diameter of the ball 10a. The first seat member 21 on the valve seat 20 is adapted to deform resiliently to allow passage of the non-deformable ball 10a through the deformable resilient seat member 21 under the force of fluid pressure above the ball 10a. The valve seat members 21,22 are adapted to seat the at least one valve closure member and are formed of resilient material, optionally as a single piece of resilient rubber or plastics material with the seat 20.

The seat members 21,22 are each adapted to seat the at least one valve closure member in a first configuration. In the first configuration, the first seat member is radially extended inwards into the bore to an inner diameter that is less than the diameter of the ball, and hence the larger ball seats on the first seat member 21 when it is in the first configuration. Each of the seat members 21, 22 is adapted to deform resiliently from the first radially extended configuration seating the ball 10a into a second radially compressed configuration to allow passage of the ball 10a past the seat members when the force urging the ball 10 downwards in the bore overcomes the resilience of the seat member 21, 22 reacting against it. The seat members are axially spaced from one another at an axial distance sufficient to engage the ball and retain it between the first and second seat members. The valve seat members 21, 22 extend radially inwards into the bore 1b of the control sleeve 60 and each form a ring having a generally hemispherical cross-sectional profile.

The inner radial dimension of each seat member 21, 22 in a resting configuration where no force is acting on it is smaller than the maximal radial dimension of the ball 10a. The inner radial dimension of each seat member 21, 22 is adapted to expand radially during deformation and axial passage of the ball through the seat member 21, 22, such that the radial thickness of each seat member 21, 22 reduces transiently during deformation. Thus as the ball 10a passes through the valve under the force of the fluid pressure above it, the inner faces of the seat members 21,22 are resiliently compressed in a radially outward direction by the non-deformable ball 10a acting under the force of fluid pressure directed downhole from the surface.

Each seat member 21, 22 optionally maintains a consistent outer radial dimension and volume in the resting and deformed configurations, and merely changes shape when deforming.

Figure 2 shows the resting configuration of the first (upper) seat member 21, which has resiliently recovered its original shape, inner diameter, and radial thickness after deformation and passage of the ball 10a through the narrow throat of the first (upper) seat member 21. The first seat member 21 deforms by radial compression from the first resting configuration to the second deformed configuration to allow passage of the ball 10a past the first seat member 21 to the position shown in Figure 2. The second (lower) seat member 22 is also adapted to seat the ball 10a in the configuration shown in Figure 2. The second seat member 22 is also adapted to resiliently deform by radial compression from the first resting configuration to a second deformed configuration to allow passage of the ball 10a past the second seat member 22 as will be described below. However, the force required to deform the second seat member 22 is higher than that required to deform the first seat member 21, so in the Figure 2 configuration, the second seat member 22 has not yet resiliently deformed and seats the ball 10a between the first and second seat members 21,22, which are axially spaced from one another along the axis of the bore 50b.

Each seat member 21, 22 has an upper surface and a lower surface, which extend from the inner surface of the bore 1b along an arcuate profile having a radius as is best shown in Figure 7. Each seat member 21,22 has an apex at the axial midpoint of each seat member 21, 22, which comprises the narrowest parts of a throat of the bore 1b of the control sleeve 60, and the seat members meet at a cleft between them, having a wider diameter, and the ball 10a is naturally received in the cleft between the seat members 21, 22. The cleft can optionally have an intermediate section of the seat between the two seat members 21, 22. The intermediate section of the seat can optionally extend generally parallel to the axis of the bore for a short distance between the seat members 21,22, as is best shown in Figure 7, so that the seat members 21, 22 are axially spaced apart along the seat by a short distance.

The seat members 21, 22 create a throat in the seat 20 that is narrower than the bore of the control sleeve 1 b and the sealing diameter of the ball 10a. In this example, the radius of the arcuate side profile of the first seat member 21 is 0.472”, smaller than the radius of the arcuate side profile of the second seat member 22 which in this example is 3.034”, but in other examples these radii may be equal and constant, and of course the dimensions recited are purely by way of example and are not intended to be limiting. Both arcuate side profiles are optionally symmetrical in and of themselves. The valve seat and the seat members may be manufactured from the same resilient material for increased compressive capacity, which may allow balls of larger diameter to be used and to pass through the valve seat 20. Increasing the diameter of the ball 10a may be useful to increase the surface area that forms the sealing surface between the seat members 21, 22 and the ball 10a.

Thus the seat 20 is adapted to retain the ball 10a between the first and second seat members 21, 22 in their first configuration, such that the first and second seat members 21, 22 both seat against the ball 10a at the same time and press against it from opposite sides (above and below). The first and second seat members 21, 22 each at least partly surround a portion of the ball 10a during deformation of the respective seat member.

The first and second seat members 21,22 resiliently urge the ball 10a in opposite axial directions from opposite axial ends of the ball 10a. For example, when the ball 10a is engaged in the seat 20 between the seat members 21,22, the resilient action of the valve seat members 21, 22 urging the ball from above and below the ball 10a resists movement of the ball 10a relative to the seat 20. The axial urging prevents the ball 10a from dislodging from the valve seat 20 even in deviated wells, for example horizontal, and returning in an uphole direction. It also requires greater fluid pressure to force the ball 10a through the valve in a downhole direction, thus preventing accidental and unpredictable opening of the valve due to the ball 10a passing through the valve seat 20 under the force of normal operative fluid pressures.

Seating of the ball 10a in the seat 20 during fluid flow in the bore 50b leads to a build-up of fluid pressure uphole of the valve assembly 1. The build-up of fluid pressure can be accelerated by increased pumping from the surface. At the first threshold pressure the fluid pressure differential across the seated ball 10a begins to overcome the force of the spring 80, which is continuously acting in compression to urge the control sleeve 60 towards the closed configuration. The control sleeve 60 is urged axially under the fluid pressure relative to the outlet port 52 from the initial configuration in which the outlet port is closed towards a circulating configuration in which the outlet port 52 is at least partially in fluid communication with the bore 50b.

As the fluid pressure increases and acts on the seated ball member 10a, the force of the fluid pushes the control sleeve 60 axially in a downhole direction. The pins 54 allow the control sleeve 60 to translate in an axial direction without a rotational component, thus maintaining the axial alignment of the aperture 62 with the outlet sleeve aperture 72 and the outlet port 52. The movement of the control sleeve 60 compresses the spring 80 between the shoulder 61 on the control sleeve 60 and the spring retainer 85. As the control sleeve 60 moves in a downhole direction relative to the outlet sleeve 70 and the housing 50, the aperture 62 moves into alignment with the aperture 72 and the outlet port 52. The alignment of the aperture 62 with the outlet port 52 allows the pressurised fluid to escape in a radial direction into the annulus of the wellbore for circulation of the fluid above the drill bit for example. These high pressure jets of fluid can be used for, for example, cleaning the annulus, or washing drill cuttings back to the surface. The fluid is prevented from flowing into the space between the housing 50 and the outlet sleeve 70 by a pair of seals situated just uphole (74u) and just downhole (74I) of the outlet sleeve aperture 72. The space between the control sleeve 60 and the outlet sleeve 70 is similarly sealed off. Thus, the fluid is directed to flow solely out of the outlet port 52 and is prevented from escaping through other paths.

After the circulation operation is concluded, and drilling is to resume, the ball 10a can be unseated from the seat 20. This can be initiated when the control sleeve is still in the Figure 2 configuration, with the outlet port 52 radially aligned with the control sleeve aperture 62 and the ball 10a seated on the seat 20. In order to reset the valve assembly 1 to the initial drilling configuration and to unseat the ball 10a, a second valve closure member in the form of a ball 10b is inserted into the bore 50b of the housing 50 above the seat 20while the first ball 10a is seated between the valve seat members 21,22, and is retained in the seat 20. The second or further ball 10b lands on the upper surface of the seated first ball 10a. The dimensions of the first and second balls 10a, 10b, are chosen so that when the second ball 10b has landed on and is abutting the first, seated, ball 10a, the second ball 10b substantially reduces or seals off the bore 1b of the control sleeve 60 above the aperture 62, thereby substantially obturating the control sleeve 60 and effectively preventing escape of the fluid through the outlet port 52. Complete closure of the bore above the aperture 62 is not needed, and it is sufficient for the second ball 10b to block most of the cross-sectional flow area of the bore of the control sleeve 60. A landing sleeve 69 is optionally disposed above the outlet aperture 62, on the opposite side of the outlet aperture from the seat 20, and having a narrowed bore 69b to receive the ball 10b and to create an optimal flow path which can be traversed by the ball 10b, but does not allow any substantial fluid flow, with an optional clearance between the ball 10b and the landing sleeve 69 of less than 1mm for example. Fluid pressure within the bore 50b above the second ball 10b then builds up further to a second fluid pressure threshold that is optionally higher than the first fluid pressure threshold, which again can be driven from the surface. Alternatively, the fluid pressure can be maintained at a constant value. The diameter of the second ball can be selected to offer the desired percentage of obturation of the bore 50b. The fluid pressure acts on the uphole faces of at least one of the first and/or second balls 10a, 10b. Once the fluid pressure above the obturated bore has increased to a level at which the force urging the balls 10b, 10a downwards in the bore 60b is greater than the resilient force maintaining the ball 10a on the second seat member 22, the higher force exerted by the fluid forces the first ball 10a through the second seat member 22, which resiliently deforms as the ball 10a passes through it, before returning to its original configuration. The second ball 10b optionally has a smaller diameter than the diameter of the bore through the valve seat 20, and so the second ball 10b passes more easily through the seat 20 without substantially seating on the seat members 21, 22. The balls 10a, 10b are optionally caught in a ball catcher device (not shown) after they have passed through the seat 20.

The first and second pressure thresholds can optionally vary in different examples, but an optional first pressure threshold could be similar to what a wellbore would withstand in a normal circulation operation. In the present example, a suitable pressure to open the ports and allow flow is around 100-300psi, for example, 150psi, which is optionally sufficient to overcome the force of the spring, and the resilience of the first seat member 21, but not the resilience of the second seat member 22. The second pressure threshold is optionally higher than the first pressure threshold, and could be from 1000-2000psi, for example 1500psi and is optionally sufficient to overcome the resilience of the second seat member 22 and to shear the ball 10 from the seat 20. The spring strength is optionally chosen in light of the likely operating pressure which will influence the desired first pressure threshold.

Once the balls 10a, 10b have passed through the valve seat 20, the obstruction of fluid flow through the bores 50b, 1b is removed, and the fluid pressure drops suddenly, reducing below the level needed to compress the spring 80. The spring 80 then returns the control sleeve 60 under its upward biasing force to the initial first configuration, where the aperture 62 is situated uphole of the outlet sleeve aperture 72, out of alignment with the aperture 72 and the outlet port 52, and the outlet port 52 is closed off from the bore 50b by the control sleeve 60 and its seals. Fluid flow through the radial pathway F2 is thus prevented and flow resumes along the axial pathway Fi. Drilling can then resume with the fluid being directed to the drill bit to wash cuttings back to the surface.

In the present example, the control sleeve 60 includes a cap 67, disposed at the uphole end of the control sleeve, which in this example is threadedly connected to the control sleeve 60. The cap 67 includes a bladed component, which is urged resiliently against the inner surface of the wall of the outlet sleeve 70, and in this example is in the form of a resilient wiper 68, but a rigid scraper or similar could also or alternatively be provided. The wiper 68 can be formed from a resilient material, for example a plastic or rubber material. The wiper 68 covers the upper end of the annulus between the control sleeve 60 and the outlet sleeve 70, and reduces the amount of debris accumulating therein. As the control sleeve moves in the bore of the outlet sleeve 70, the wiper 68 scrapes against the inner surface of the outlet sleeve and cleans off debris. The inner diameter of the cap 67 is larger than the inner diameter of the valve seat 20, in order to avoid any erroneous seating of the ball 10a in the cap 67 before it reaches the seat 20.

The threaded connection of the cap 67 with the control sleeve 60 allows removal of the component for repair or replacement without requiring complete disassembly of the other valve sleeves. This also permits, for example, the insertion of components to narrow the bore of the control sleeve 60 further for use with different sizes of balls or other shapes of plugs.

At the uphole edge of the outlet sleeve 70, there is a cap 75 connected by threaded attachment to the outlet sleeve 70. The cap 75 has an upper end which offers a leading edge 40 facing in an uphole direction, against the fluid flow F. The outer wall of the cap 75 is cylindrical with parallel sides to match the inner bore 50b, but the inner wall 75w of the cap has a shaped profile which tapers radially inwards into the bore of the cap 75 to a throat 75t, which is narrower than the upper end of the bore of the cap 75, but wider than the seat 20. The inner wall of the cap 75w therefore forms a funnel in the bore, which acts to reduce turbulence and drag within the flow of the fluid, and to smooth out any eddies that would otherwise have been created by the upper end of the outlet sleeve 70. The funnel provided by the inner wall 75 directs fluid into the bore 1b, with a diameter that is at least equal to the diameter of the bore 1b, but can optionally be less than the diameter of the bore 1b.

In another optional feature, the control sleeve 60 is optionally castellated at 68 at its downhole end. In this example, these castellations 68 are in the form of arches cut out of the sleeve material, but other shapes may be used. The castellations 68 permit fluid flow through the arches to the annular space in between the control sleeve 60 and the valve housing 50, into the cavity where the spring 80 is retained.

In this case, when the control sleeve 60 moves in a downhole direction, the spring is free to compress as fluid is forced out of the cavity through the castellations 68 and into the bore 50b. Similarly, when the control sleeve 60 is travelling back in an uphole direction to its initial configuration, the spring 80 must extend, and fluid can flow through the castellations 68 into the spring cavity to fill the vacuum that the extension creates. This feature reduces the risk of hydraulic lock of the control sleeve 60. The spring retainer 85 likewise has similar formations allowing fluid communication and preventing or alleviating risks of hydraulic locking of the moving parts of the assembly 1.

An operation using the above example will now be described. During wellbore operations, for example downhole drilling, fluid is normally pumped axially down the drill string to the drill bit for cooling the bit, and for washing cuttings back to the surface. The option of diverting the fluid being pumped down the bore of the string into a radial fluid flowpath can be desirable in order to e.g. clean drill cuttings from the annulus of the wellbore. In this example, the ball 10a is dropped from the surface and travels through the bore of the string under the combined force of gravity and fluid being pumped down the well by positive displacement pumps at the surface. The ball 10a enters the bore 50b of the valve assembly 1 and passes through the cap 75 of the outlet sleeve 70. The ball 10a then passes through the cap 67 of the control sleeve 60 and the landing sleeve 69, and into the narrower bore, passing the control sleeve aperture 62 before landing on the seat 20. When engaged with the seat 20, the non-deformable ball 10a forces deformation of the resilient first (upper) seat member 21 under the initial force of fluid pressure in the bore behind the ball 10a. As the ball 10a passes through throat of the seat member 21, the seat member 21 is radially compressed by the ball 10a, such that its radial thickness is reduced and the diameter of the bore increases in a transient and reversible manner, but while the outer diameter of the seat member 21 and the volume remain unchanged. The second resilient seat member 22, being in this example larger than seat member 21, requires more force to deform and allow passage of the ball 10a. The ball 10a is thus held within a cleft in the seat 20, below the first seat member 21 and above the second seat member 22, and is retained there under the opposing axial urging forces that the seat members 21, 22 apply to the ball’s uphole- and downhole-facing surfaces.

The seating of the ball 10a in the seat 20 obturates the axial fluid flowpath Fi, as the seat members 21,22 sealingly engage with at least a circumferentially-extending portion of the surface of the ball 10a. The resulting increase in fluid pressure uphole of the valve assembly 1 and into the bore 50b applies a correspondingly increasing force to the uphole-facing surface of the seated ball 10a. Once the fluid pressure has reached a threshold where the force applied to the ball 10a is greater than the opposing biasing force of the spring 80, the control sleeve 60 begins to travel axially in a downhole direction, and is guided in an axially-travelling path by the inner ends of the pins 54 occupying axial slots on the outer surface of the control sleeve 60.

Any rotational movement of the control sleeve 60 at this point could lead to the aperture 62, through the wall of the control sleeve 60, being misaligned relative to the aperture 72, through the wall of the outlet sleeve 70, and the outlet port 52, through the side wall of the housing 50. Hence, preventing rotation via the pins 54 increases consistency of fluid flow through the open outlet port 52.

The spring 80 is compressed between the spring retainer 85 and the chamfered shoulder 61 in the control sleeve 60, with the compression increasing as the control sleeve 60 travels axially downwards. The control sleeve aperture 62 begins to cross the outlet aperture 72, allowing a small volume of fluid to be diverted out of the outlet port 52, which is fully aligned with the aperture 72. This diversion of fluid can sometimes slightly reduce the fluid pressure within the bore, and pumping from the surface can optionally increase accordingly in order to maintain sufficient force to continue compressing the spring 80. Once the control sleeve 60 has reached the full extent of its travel, the apertures 62, 72 and the outlet port 52 are fully aligned, and the flow of fluid is diverted along the radial flowpath shown as arrows F2 in Figure 2, through the apertures 62, 72, and outlet port 52, into the annulus of the well bore.

Full alignment is not strictly necessary for satisfactory performance, but it is convenient to shift the control sleeve 60 by the same amount each time. The axial travel of the control sleeve 60 can optionally be limited by a travel stop formed by a shoulder on the outlet sleeve 70.

Once the function of the radial flow of fluid into the annulus has been performed, and the operator wishes to return the fluid flow to an axial direction through the valve assembly 1, a second ball 10b is dropped from the surface, and travels through the string to the valve assembly 1 under the combined force of gravity and fluid flow.

The ball 10b passes through the narrowed bore of the cap 67 and lands on the uphole-facing surface of the first ball 10a, which remains retained in the seat 20.

The second ball 10b can be of a smaller diameter than the first ball 10a. The second ball 10b either partially or wholly obturates the bore 1b at a position uphole of the aperture 62, optionally blocking the bore 69b of the landing sleeve 69 which is selected to deny any substantial fluid flow past the ball 10b when it is in the landing sleeve 69.

In order to increase the force applied to the first ball 10a, the fluid pressure can be increased from the surface to a second pressure threshold which is optionally higher than the first threshold. This increases the force bearing down on the uphole-facing surface of the second ball 10b, which in turn bears down on the first ball 10a. The downhole-directed force applied by the higher second pressure threshold drives the non-deformable ball 10a down the bore 1b to begin deformation of the second valve seat member 22 and press into the narrow throat of the seat member 22. The ball 10a causes the seat member 22 to compress in a radially outward direction, transiently increasing the diameter of the bore formed by the seat member (while optionally maintaining outer diameter and volume), and allowing the ball 10a to pass through the seat 20. The second ball, 10b, is in this example of a smaller diameter than the first ball 10a, and so it passes comparatively easily through the seat 20 without seating. The balls 10a, 10b, are then optionally caught in a ball catcher downhole of the valve assembly (not shown). The second seat member 22 meanwhile returns to its initial uncompressed configuration.

Once the balls 10a, 10b have passed through the valve seat 20, the fluid pressure is relieved, and there is nothing to maintain the compression of the spring 80 which returns the control sleeve 60 to its original upper position. As the control sleeve 60 moves in an uphole direction, the wiper 68 wipes against the inner surface of the outlet sleeve 70 and cleans away debris, reducing the risk of the control sleeve 60 jamming and maintaining the smooth running of the control sleeve within the outlet sleeve 70, and keeping any debris from entering the annulus between the control sleeve 60 and the outlet sleeve 70, and degrading the seals therein. Once the control sleeve 60 has returned to its initial position, the aperture 62 is wholly out of alignment with the aperture 72 and the outlet port 52 and the fluid flow returns to an axial path, shown as arrow Fi in Figure 1.

By varying the dimensions of the balls 10a, 10b and the seat 20, it is possible to partially close the bore 1b, and merely restrict fluid passage through the valve assembly. This moves the control sleeve 60 into an intermediate position (not shown) where the aperture 62 is partly aligned with the aperture 72 and outlet port 52. This can be used to increase the pressure of the radial jets of fluid through the port 52, for example.

Figures 8-10 show an alternative embodiment of the apparatus, with the parts of the apparatus that correspond to the same parts in the first embodiment being denoted by the same reference numbers increased by 100. A valve assembly 101, for use in a wellbore of an oil, gas or water well, comprises a housing 150 having a bore 150b in fluid communication with the bore of the string of tubulars in which the valve assembly is integrated. The bore 150b houses an outlet sleeve 170 and a control sleeve 160. The outlet sleeve 170 at least partly surrounds a portion of a control sleeve 160, which has a bore 101b with an axis that is generally co-axial with the bore 150b of the housing and the bore of the outlet sleeve 170. The bores of the sleeves 160, 170 are in fluid communication with the bore 150b of the housing 150.

The valve assembly 101 operates in substantially the same way as the valve assembly 1 described above, and thus the similar components and method of operation are not described again here, for brevity, and the reader is directed to the description of valve assembly 1 above.

The uphole end of the control sleeve 160 is formed as a single component, with a chamfered uphole-facing edge narrowing into the bore 101b, which optionally has a consistent inner diameter along its length. On the outer surface of the control sleeve 160 is wiper 168, which acts to wipe or scrape the inner surface of the outlet sleeve 170 as the control sleeve 160 returns from a position where the outlet port 152 is open, to the control sleeve’s original position where the outlet port 152 is closed.

The ball 110a is dropped from the surface landing on the seat 120, and forces deformation of the resilient first (upper) seat member 121 so that it is held within a cleft in the seat 120 as described above. This obturates the axial fluid flowpath and shifts the control sleeve 160 to open the radial outlet port 152 and compress the spring 180. The second ball 110b is dropped from the surface, and lands on the first ball 110a, retained in the seat 120. The second ball 110b can be of a smaller diameter than the first ball 110a. The second ball 110b either partially or wholly obturates the bore at a position uphole of the aperture 162, but the present example has no landing sleeve 169, and hence does not allow for the same variation in diameters of balls 110b. The force applied by the higher second pressure threshold drives balls 110a, 110b through the seat 120 as previously described, allowing the return of the control sleeve 160 to the first configuration under the force of the spring 180.

Claims

1. A valve assembly for use in a wellbore of an oil, gas or water well, the valve assembly having a bore with an axis, the assembly having a valve seat adapted to be sealed by at least one valve closure member, wherein the valve seat comprises a first seat member adapted to seat the at least one valve closure member in a first configuration, wherein the first seat member is adapted to resiliently deform from the first configuration to a second configuration to allow passage of the at least one valve closure member past the first seat member, and a second seat member adapted to seat the at least one valve closure member in a first configuration, wherein the second seat member is adapted to resiliently deform from the first configuration to a second configuration to allow passage of the at least one valve closure member past the second seat member, wherein the first and second seat members are axially spaced from one another on the seat, and wherein the seat is adapted to retain the at least one valve closure member between the first and second seat members.

2. A valve assembly as claimed in claim 1, wherein the first and second seat members are adapted to seat against the valve closure member at the same time.

3. A valve assembly as claimed in any one of claims 1-2, wherein the first and second seat members are adapted to urge the valve closure member in opposite axial directions from opposite axial ends of the valve closure member when the valve closure member is retained between the first and second seat members.

4. A valve assembly as claimed in any one of claims 1-3, wherein the first and second seat members are adapted to deform resiliently away from one another in opposite axial directions when the valve closure member is retained between them, and wherein the first and second seat members are adapted to press on the valve closure member from opposite axial directions to resist movement of the valve closure member relative to the seat when said valve closure member is retained between the first and second seat members.

5. A valve assembly as claimed in any one of claims 1-4, wherein the resilience of the valve seat members is adapted to maintain sealing engagement of the valve closure member against the seat when the valve closure member is retained between the first and second seat members.

6. A valve assembly as claimed in any one of claims 1-5, wherein the first and second seat members each at least partly surround a portion of the valve closure member during deformation of the seat member.

7. A valve assembly as claimed in any one of claims 1-6, wherein the first and second seat members comprise mutually parallel rings extending circumferentially around the inner surface of the control sleeve.

8. A valve assembly as claimed in any one of claims 1-7, wherein the first and second seat members are spaced apart by an axial distance which is less than a maximal dimension of the valve closure member.

9. A valve assembly as claimed in any one of claims 1-8, wherein an inner radial dimension of each seat member in the first configuration is smaller than the maximal radial dimension of the valve closure member.

10. A valve assembly as claimed in any one of claims 1-9, wherein each seat member maintains a consistent outer radial dimension in the first and second configurations.

11. A valve assembly as claimed in any one of claims 1-10, wherein the inner radial dimension of each seat member expands during deformation and axial passage of the valve closure member through the seat member, such that the radial thickness of the seat member reduces transiently during deformation.

12. A valve assembly as claimed in claim 11, wherein the inner diameter and radial thickness of the first and second seat members recover resiliently to the first configuration after axial passage of the valve closure member through the seat.

13. A valve assembly as claimed in any one of claims 1-12, wherein the first seat member is disposed above the second seat member, and wherein the second seat member has a higher elastic modulus than the first seat member.

14. A valve assembly as claimed in any one of claims 1-13, wherein the first and second seat members extend radially inward from the inner surface of the bore.

15. A valve assembly as claimed in any one of claims 1-14, wherein each of the first and second seat members form a ring having a hemispherical cross-sectional profile.

16. A valve assembly as claimed in any one of claims 1-15, wherein each seat member has an upper surface and a lower surface, wherein the upper and lower surfaces of the first and second seat members extend from the inner surface of the seat along an arcuate profile having a radius, and wherein the upper and lower surfaces meet in an apex at the axial midpoint of each seat member.

17. A valve assembly as claimed in claim 16, wherein the apex comprises the narrowest part of a throat of the bore through the seat member.

18. A valve assembly as claimed in claim 16 or 17, wherein the radius of the arcuate profile of the first and second seat members is constant.

19. A valve assembly as claimed in any one of claims 16-18, wherein the radius of the arcuate profile of one of the first and second seat members is less than the radius of the other seat member.

20. A valve assembly as claimed in any one of claims 1-19, wherein the valve seat and the seat members are integrally formed from the same resilient material.

21. A valve assembly as claimed in any one of claims 1-20, wherein the valve assembly comprises at least one outlet port adapted to be actuated between open and closed configurations to permit and restrict fluid communication between the bore of the valve assembly and an external surface of the valve assembly.

22. A valve assembly as claimed in claim 21, wherein the at least one outlet port is obturated by a control sleeve which moves axially relative to the outlet port, wherein the control sleeve has at least one aperture that moves in and out of register with the outlet port as the valve assembly to change between open and closed configurations.

23. A valve assembly as claimed in claim 22, wherein the valve seat is provided within the control sleeve.

24. A valve assembly as claimed in claim 23, wherein the seat members extend radially inwards from the inner surface of the control sleeve, creating a throat in the seat that is narrower than the bore of the control sleeve and the sealing diameter of the valve closure member.

25. A valve assembly as claimed in any one of claims 21-24, wherein rotation of the control sleeve relative to the outlet port is restricted.

26. A valve assembly as claimed in any one of claims 21-25, wherein seating of the valve closure member in the seat leads to a build-up of fluid pressure uphole of the valve assembly, wherein at a first threshold pressure the fluid pressure differential across the seated valve closure member overcomes the force of a resilient device biasing the control sleeve into a closed configuration, such that the control sleeve is urged axially under the fluid pressure relative to the outlet port from the closed configuration into an open configuration in which the outlet port is at least partially in fluid communication with the bore.

27. A valve assembly as claimed in claim 26, wherein at the first threshold pressure, the valve seat remains in the first configuration and continues to engage the valve closure member such that the valve closure member is retained in the seat and continues to obturate the bore of the valve assembly.

28. A valve assembly as claimed in any one of claims 21-27, wherein the valve assembly includes an outlet sleeve that is fixed in position relative the outlet of the valve assembly, wherein the outlet sleeve comprises a leading edge formation at an uphole end of the outlet sleeve, formed as radially inwardly extending shoulder having a throat that narrows to a diameter at its downhole end that is at least as narrow as the inner diameter of the bore of the control sleeve.

29. A valve assembly as claimed in any one of claims 1-28, including a shoulder extending radially into the bore above the seat.

30. A valve assembly as claimed in claim 29, wherein the shoulder has a maximum diameter at its uphole end, and tapers to a narrower diameter towards its downhole end, forming a funnel having an inner diameter at least as narrow as the bore of the valve assembly above the seat.

31. A valve assembly as claimed in any one of claims 1-30, wherein the bore is adapted to receive first and second valve closure members, wherein the second valve closure member is inserted into the bore after the first valve closure member is retained in the seat and wherein the bore is adapted to be obstructed by the second valve closure member, and wherein build-up of fluid pressure within the bore above the second valve closure member to a second fluid pressure threshold is adapted to force the first valve closure member through the second seat member.

32. A valve assembly as claimed in claim 31, wherein the second valve closure member is adapted to pass through the valve seat without seating.

33. A method of diverting fluid flow in a wellbore of an oil, gas, or water well, the method including: flowing fluid through a valve assembly comprising a bore with an axis, and a valve seat having first and second seat members, the bore being in fluid communication with the wellbore; admitting a valve closure member into the valve assembly; resiliently deforming the first seat member to allow passage of the at least one valve closure member past the first seat member; seating the valve closure member on the valve seat in the valve assembly; and retaining the valve closure member seated on the seat between the first seat member and the second seat member.

34. A method as claimed in claim 33, including seating the valve closure member between the first and second seat members such that the valve closure member obturates the bore of the valve assembly and actuates the valve assembly from a first configuration in which fluid flow is directed axially through the bore, to a second configuration in which fluid flow is directed radially through at least one outlet port disposed in a side wall of the valve assembly.

35. A method as claimed in claim 33 or 34, the method including building fluid pressure uphole of the valve assembly when the bore is obturated by the valve closure member to urge the valve assembly in a downhole direction against the biasing force of a resilient device.

36. A method as claimed in any one of claims 33-35, including inserting a second valve closure member into the bore such that it engages the first valve closure member and at least partially obturates the bore above the first valve closure member.

37. A method as claimed in claim 36, including engaging the first and second valve closure members when the second valve closure member is above the outlet port, there by obstructing the bore of the assembly above the outlet port, and increasing fluid pressure within the bore to a second pressure threshold higher than the first pressure threshold above the second valve closure member.

38. A method as claimed in any one of claims 36-37, including passing the second valve closure member through the first and second seat members without seating.

39. A method as claimed in any one of claims 33-38, including increasing the fluid pressure in the bore until it reaches a second threshold pressure higher than the first threshold pressure, wherein the second threshold pressure forces the first valve closure member through the second seat member.

40. A method as claimed in any one of claims 33-39, including returning the valve assembly to a closed configuration in which fluid travels in an axial direction through the bore by expansion of a resilient device.

41. A method as claimed in any one of claims 33-40, including retaining the first valve closure member in a cleft between the first and second valve seat members.

42. A method as claimed in any one of claims 33-41, including increasing the fluid pressure differential across the seated valve closure member to a first threshold at which the first seat member deforms to allow passage of the first valve closure member but the second seat member does not deform.

43. A method as claimed in claim 42, including further increasing the pressure differential across the seated valve closure member to a second threshold higher than the first threshold, and wherein the second seat member deforms at the second threshold to allow passage of the first valve closure member through the seat.

44. A method as claimed in any one of claims 33-43, including reducing the downward thrust acting on the valve seat by restricting fluid flow through the bore axially uphole of the seat.