Patent Description:
Screens are used in tubular systems to separate particulate from fluids. Such systems are used in the downhole completion field to separate sand and other particulate from fluids, e.g. production fluids or hydrocarbons, such as oil, water and gas.

As outlined in <CIT> (BP EXPLORATION), in the course of completing an oil and/or gas well, it is common practice to run a string of casing into the well-bore and then to run the production tubing inside the casing. The casing is perforated across one or more hydrocarbon bearing zones (hereinafter 'producing zones') to allow produced fluids to enter the casing bore. After the well is completed and placed in production, formation sand from unconsolidated formations may be swept into the flow path along with produced fluids. This sand is relatively fine and causes erosion of tubing, downhole equipment and surface equipment. In some completions, however, the well bore is uncased, and an open face is established across the producing zone, in particular, in horizontal well completions. Similarly, after the well is completed and placed in production, formation sand from unconsolidated formation may be swept into the flow path along with produced fluids.

With either cased or uncased well-bores, one or more sand screens may be installed in the flow path between the production tubing and the producing zone(s). A packer may be set above and below the sand screen to seal off the annulus in the producing zone from non-producing zones of the formation. The annulus around the screen may be packed with a relatively coarse sand or gravel which acts as a filter to reduce the amount of fine formation sand reaching the screen. Nevertheless, the remaining sand contained in the produced fluids may impinge on a screen with sufficient velocity so as to cause erosion of the screen. As the velocity of the flow of the produced fluids is increased, the rate of erosion also increases. Where the fluid flow rate from one portion of the formation is greater than the fluid flow rate from another portion of the formation, the screen will erode more rapidly opposite the high flow rate portion than it will opposite the lower flow rate portion.

<CIT>discloses a sand screen comprising a perforated base pipe and an erosion resistant microporous sleeve. The erosion resistant microporous material of the sleeve is selected from the group consisting of microporous polymeric foams, microporous metal foams, microporous carbide monoliths, and microporous nitride monoliths.

<CIT>discloses a screen device including a foam body having a passageway that extends longitudinally through the foam body, the foam body having an open cell structure such that at least two surfaces of the foam body are in fluidic communication with one another through the foam body.

<CIT> discloses a multi-zone gravel pack system with a pipe coupling and an integrated valve. The system has a first outer tubular member and a first inner tubular member. The first outer tubular member and the first inner tubular member can define a first space therebetween. The apparatus can further include a second outer tubular member and a second inner tubular member. The second outer tubular member and the second inner tubular member can define a second space therebetween. A first coupling flowpath can be positioned between the first and second spaces.

<CIT> discloses a well screen having slurry flow paths. The well screen includes support rods extending in the axial direction of the screen disposed cylindrically at a predetermined interval in the circumferential direction of the screen, a wire wound on the outer periphery of said support rods so as to form slits of a predetermined width, one or more flow paths for gravel-containing slurry provided inside of the wire and extending in the axial direction of the screen, and openings for communicating the flow paths with the outside of the screen.

In well completions having screened pipe, the screened pipe typically comprises base pipe (or inner pipe) overlaid by a screen (or outer jacket). The base pipe can be solid or slotted. The outer screen has hole or port dimensions selected to filter out particles above a desired size during production. The screen can be attached to the base pipe by axial support rods welded to an outer surface of the base pipe, which rods are then overlaid circumferentially by wire with a triangular cross-section. The points of the triangular wire are welded to the axial support rods. Between the rods, at least partly annular spaces are created between the circumferential wire wrap screen and the base pipe.

There has been identified a need for the base pipe to be isolated from the through-bore initially so that some other operations can be performed. Therefore, if the base pipe is solid, the openings that provide through-bore communication need to be initially closed. If the base pipe is perforated/slotted, the perforations need initially to be sealed. Prior to production, there may be a wish to stimulate the well by injecting fluids into the hydrocarbon (HC) formation in a reverse direction to production. Since injection involves pumping of high pressure/flow rate fluids through the screen in a reverse direction, the screen must be able to withstand erosion in both directions (covering injection followed by production). In addition there may be a wish to distribute injected fluids in a uniform manner across the hydrocarbon formation (if possible) to seek to ensure all portions of the formation are equally stimulated.

There may be a desire that the annulus between the screen and the base pipe of all adjacent sand screen joints can be or is inter-connected.

It is an object of the aspect of the present invention to obviate or at least mitigate one or more problems and/or disadvantages in the prior art.

According to an aspect of the present invention there is provided a downhole screen assembly for use in the production of fluids, according to the appended claims.

There is provided a screen or screen assembly, such as a downhole/sand screen or screen assembly, comprising a pipe and a sleeve and at least one support provided between the pipe and the sleeve, wherein the at least one support has a cross-section comprising first and second points, vertices, surface discontinuities and/or corners.

Such support shape may provide enhanced erosion resistance.

The pipe may be referred to as a base pipe or production tubing.

The pipe may be perforated and/or comprise a plurality of ports.

Alternatively the pipe may be solid, e.g. comprise a solid tubular wall or tubular wall section(s).

The first and second points, vertices, surface discontinuities and/or corners (hereinafter 'points') may comprise a pair of points.

The first and second points may face in substantially opposing directions, e.g. along a radial direction, e.g. of the pipe and/or the sleeve.

The at least one support may comprise a plurality of supports, e.g. axial supports and/or support rods.

The supports may be disposed in an annular space between the pipe and the sleeve.

The sleeve may be provided around the pipe.

In one implementation the/each support may have a cross-section comprising a polygon having at least four sides and/or which is a parallelogram, rectilinear, or beneficially square or diamond shape.

In another implementation the/each support may have a cross-section comprising a polygon having six sides, e.g. a polygon having opposing triangular end portions and a rectilinear or square mid-portion.

A first point may be welded to the pipe, e.g. an outer surface of the pipe.

A second point may be welded to the sleeve, e.g. an inner surface(s) of the sleeve.

There is provided a screen or screen assembly, such as a downhole/sand screen or screen assembly, wherein the screen comprises wire having a cross-section comprising first and second points, vertices, surface discontinuities and/or corners.

Such wire shape may provide enhanced erosion resistance.

The first and second points may face in substantially opposing directions, e.g. along a radial direction, e.g. of a pipe and/or a sleeve.

The screen may comprise a pipe and a sleeve (the sleeve comprising the wire/screen), and at least one support.

The pipe may be perforated and/or comprise a plurality of ports. Alternatively the pipe may be solid, e.g. comprise a solid tubular wall or tubular wall section(s).

The supports may be disposed in an annular space between the pipe and the sleeve. The sleeve may be provided around the pipe.

In one implementation the/each wire may have a cross-section comprising a polygon having at least four sides and/or which is rectilinear or beneficially square or diamond shape.

In another implementation the/each wire may have a cross-section comprising a polygon having six sides, e.g. a polygon having opposing triangular end portions and a rectilinear or square mid-portion.

A first point may be welded to a support or to the pipe, e.g. to an outer surface of the support or pipe.

A second point may face radially out, e.g. towards a formation or inner facing surface of a borehole.

There is provided a screen or screen assembly, such as a downhole/sand screen or screen assembly, wherein the screen comprises wire having a cross-section comprising a rectilinear shape or parallelogram.

The rectilinear shape or parallelgram may comprise a rectangle or in a preferred implementation may comprise a square or diamond shape.

The wire may be disposed such that a line of symmetry of the rectilinear shape is provided along a radial direction of the screen.

The screen may comprise a pipe and a sleeve (the sleeve beneficially comprising the wire/screen), and at least one support.

A side of the wire may be welded to the supports(s).

There is provided a screen or screen assembly, such as a downhole/sand screen or screen assembly, comprising coated and/or hardened wire.

In one implementation the coating may be tungsten carbide, e.g. hardide tungsten carbide.

The coating may be applied or deposited by chemical vapour deposition (CVD) - which may be applied to steel.

The wire may be heat treated so as to harden.

The screen may comprise a pipe and a sleeve, the sleeve comprising the wire, and optionally at least one support.

The wire may be provided in coated and/or hardened lengths and made-up or assembled in longer lengths so as to provide the sleeve.

There is provided a screen or screen assembly, such as a downhole or sand screen or screen assembly, comprising a pipe and a plurality of ceramic discs around the pipe.

Such may provide enhanced erosion resistance.

The ceramic discs may be stacked on each other.

The pipe may comprise a plurality of ports, e.g. slots, e.g. circumferentially and/or axially spaced thereupon.

One or more of the discs may be arranged so as to provide circumferential/annular spaces between the pipe and the respective disc.

Between adjacent circumferential/annular spaces the disc(s) may be arranged such that there is no gap (e.g. radial gap) between the pipe and the disc. Such arrangement may be provided by portions of the disc having reduced internal diameter, e.g. such that the pipe and the disc(s) radially abut or contact one another at said portions.

The space(s) may extend longitudinally between adjacent discs.

The space(s) may be aligned, e.g. rotationally aligned, with at least one port in the pipe.

A valve member may be provided between a port and a respective space.

The/each valve member may comprise a slidable member, e.g. a longitudinally slideable member.

Each valve member may comprise at least one further port and/or at least one reed valve which may be (longitudinally) selectively alignable with or out of alignment with a port of the pipe.

The screen or screen assembly may also comprise an inner sleeve. The inner sleeve may be slidable relative to the pipe.

An outer surface of the inner sleeve may abut or contact an inner surface of the pipe.

The inner sleeve may comprise at least one yet further port or further reed valve which may be (longitudinally) selectively alignable with or out of alignment with a port of the pipe.

There is provided a screen or screen assembly, such as a downhole/sand screen or screen assembly, comprising a pipe and/or tubular and a sleeve, wherein the pipe and/or tubular comprises a plurality of slotted ports or longitudinally extending ports.

Such arrangement may provide enhanced erosion resistance.

The sleeve may comprise a microporous sleeve.

The pipe may comprise a base pipe or production tubing.

The tubular may comprise a further sleeve, e.g. inner sleeve, e.g. sliding sleeve.

There is provided a screen or screen assembly, such as a downhole screen or screen assembly, comprising a pipe or sleeve, wherein the pipe comprises a solid or non-perforated pipe.

The solid or non-perforated pipe may comprise an opening(s) or port(s) at or adjacent an end(s) thereof, e.g. to deliver injection fluid to a formation.

The microporous sleeve may be an erosion resistant microporous sleeve.

The microporous sleeve may comprise a material selected from a metal foam or a ceramic foam.

The microporous sleeve may comprise a material selected from the group consisting of microporous polymeric foams, microporous metal foams, microporous carbide monoliths, in particular, silicon carbide, tungsten carbide, or titanium carbide monoliths or microporous nitride monoliths, such as boron nitride.

The microporous sleeve may intimately contact and/or be bonded to an outer surface of the pipe.

There is provided a screen or screen assembly, such as a downhole/sand screen or screen assembly, comprising a pipe and a sleeve, wherein the pipe comprises openings or ports (such as longitudinal or axial opening(s) or slot(s)) and the sleeve comprises a foam or microporous material, the sleeve being bonded with or to an exterior surface of the pipe.

Such arrangement may provide relatively even distribution of injection fluids.

The pipe may be referred to as a base pipe.

The openings or slots may comprise or be referred to as daisy passages.

The opening or slots may, in use, fluidically communicate with the sleeve.

There is provided a screen or screen assembly, such as a downhole/sand screen or screen assembly, comprising a pipe having at least one port or perforation or hole, the/each port or perforation or hole having an associated valve.

The pipe may comprise a plurality of ports or perforations or holes (hereinafter "port"), each port having an associated valve.

The/each valve may, in use, initially be provided to isolate the inner diameter of the pipe from the outer diameter of the pipe.

Upon opening the valve(s) the provision of multiple ports in the pipe may provide improved distribution of injection fluid.

The/each valve may comprise a valve member.

The/each valve member may be deployable by or comprise a sliding sleeve and/or be deployable by pressure of fluid flow, in use.

The sliding sleeve may slide relative to an inner surface of the pipe.

The sliding sleeve may comprise a port(s) which may be controllably aligned with ports of the pipe.

The valve member(s) may be biased into a closed position, e.g. by biasing means.

In one implementation the valve member(s) may comprise a spherical member(s), e.g. biased spherical member(s).

The/each spherical member may be provided, e.g. movably provided, within a space provided by a port in the pipe and a recessed portion in a sleeve.

In yet another implementation the valve member(s) may comprise a flap, e.g. thin metallic or steel flap or reed valve.

In still yet another implementation the valve member(s) may comprise one or more sliding sleeve(s).

There is provided a screen or screen assembly, such as a downhole/sand screen or screen assembly, comprising a pipe having at least one port or perforation or hole, and at least one sleeve provided within the pipe, the screen having at least one respective port or perforation or hole which in a closed position is not aligned or is misaligned with the at least one port or perforation or hole in the pipe but which in an open position is alignable or aligned with the at least one port or perforation or hole in the pipe.

The/each sleeve (internal sleeve) may comprise a shift sleeve.

The/each sleeve may beneficially be provided internal of or within the pipe.

The/each sleeve may be slidable relative to the pipe so as to move from a closed to open position and optionally vice versa.

The pipe may comprise a plurality of ports or perforations or holes.

The/each sleeve (internal sleeve) may comprise a plurality of respective ports or perforations or holes.

The presence of multiple ports/perforations/holes may allow for improved distribution of injection fluid.

The screen may comprise an (outer) sleeve or screen sleeve, e.g. comprising wire.

There is provided a screen or screen assembly, such as a downhole/sand screen or screen assembly, comprising a pipe and a plurality of sleeves.

The sleeves (inner sleeves) may be provided within the pipe.

The sleeves may each comprise a sliding/shift sleeve.

There may be provided first and second sleeves, e.g. one provided within the other.

Movement, e.g. sequential movement, of the sleeves may cause alignment or misalignment, of ports in the pipe and the sleeve(s), e.g. opening or closing, of the screen.

Sliding movement of a first sleeve may cause sliding movement of a second sleeve, e.g. to open the screen.

Sliding movement of a second sleeve may cause sliding movement of a first sleeve, e.g. to close the screen.

There is provided a screen or screen assembly, such as a downhole/sand screen or screen assembly, comprising a pipe comprising at least one port/perforation/hole, the or each port having a respective seal or plug.

The pipe may comprise a plurality of ports.

In a closed disposition the respective seal or plug may be received or be provided within or adjacent to the respective port.

In an open disposition the respective seal or plug may be provided distal the respective port.

A transition from a closed disposition to an open disposition may be achieved at or above a predetermined threshold flow rate of fluid acting on the plug.

The seal(s) or plug(s) may be carried by a sleeve, e.g. on an outer surface of a shifting/sliding sleeve provided within the pipe.

There is provided a screen assembly, such as a downhole/sand screen assembly, comprising at least a first screen and a second screen.

The first screen and second screen are longitudinally disposed relative to one another.

The first screen may be selected to be provided in high(er) flow areas, e.g. production and/or injection fluid flow areas.

The first screen may have a higher erosion resistance than the second screen.

The first screen may comprise or include a microporous material, e.g. ceramic material, for example, a foamed ceramic or metal, or ceramic discs.

The second screen may be selected to be provided in low(er) flow areas, e.g. production and/or injection fluid flow areas.

The second screen may comprise wire having a cross-section comprising a triangular shape.

Alternatively the second screen may comprise wire having a cross-section comprising a square shape.

There is provided a screen or screen assembly, such as a downhole/sand screen or screen assembly, comprising a pipe and a sleeve, wherein the screen or pipe comprises a port(s) and the sleeve comprises a solid or wall portion(s) or baffles at or near the port(s).

The solid or wall portions or baffles may be provided radially outward of the port(s).

The port(s) may be provided on the pipe and/or at each end of the pipe; in the latter case the pipe optionally having a solid wall.

The solid or wall portion(s) may be provided radially adjacent the port(s), e.g. radially outward of the port(s).

This arrangement may provide that injection flow, e.g. high rate injection flow, may meet or hit a solid or wall portion, change direction and flow axially along an annulus between the pipe and the sleeve. In this way an area of highest erosion is deflected to an area of pipe having a solid outer wall.

The first screen may comprise a first pipe and a first sleeve. The second screen may comprise a second pipe and a second sleeve.

The first and second pipes are coupled by a coupling, e.g. a threaded coupling.

The first and second sleeves are coupled by a centraliser, and/or optionally by or via first and second support rings.

The centraliser forms a portion of the fluid flow path.

There is provided a screen assembly, such as a downhole/sand screen assembly, comprising first and second screens longitudinally disposed relative to one another, wherein a centraliser is provided between adjacent ends of the first and second screens.

A first support ring may be provided between an end of a sleeve of the first screen and a first end of the centraliser.

A second support ring may be provided between an end of a sleeve of the second screen and a second end of the centraliser.

There is provided a screen assembly, such as a downhole/sand screen assembly, comprising first and second screens longitudinally disposed relative to one another, wherein a further screen or screen portion is provided between adjacent ends of the first and second screens.

A first support ring may be provided between an end of a sleeve of the first screen and a first end of the further screen.

A second support ring may be provided between an end of a sleeve of the second screen and a second end of the further screen.

There is provided a screen or screen assembly, such as a downhole/sand screen or screen assembly comprising a pipe and a plurality of ceramic discs stacked on each other, wherein at least one spacer is provided between two adjacent discs, wherein the/each at least one spacer is aligned with a respective hole or slot or perforation in the pipe.

There is provided a screen or screen assembly, such as a downhole/sand screen or screen assembly, comprising a pipe and a plurality of ceramic discs stacked on each other, wherein at least one spacer is provided between at least two adjacent discs, wherein the/each spacer is shaped to diffuse fluid flow exiting a hole or slot or perforation in the pipe.

The spacer may comprise first and second surfaces.

The first and second surfaces may be concave.

The first and second surfaces may face in opposing directions.

Each of the first and second surfaces may be radially diverging.

The discs may be provided around the pipe.

Beneficially each spacer may be integrally formed with a disc.

Beneficially each disc and/or each spacer may be made from a ceramic material.

In one implementation a plurality of longitudinally adjacent discs may provide a plurality of circumferentially adjacent spacers. Such may be rotationally aligned with a hole/slot/perforation in the pipe.

Adjacent discs may be spaced from one another, e.g. by the spacer(s).

The spacer(s) may be provided on a surface or face of the/each disc.

Spacer(s) may be provided around the surface or face of the/each disc.

There is provided a screen assembly, such as a downhole/sand screen assembly, comprising a plurality of screens, wherein each screen comprises a pipe and a shifting sleeve, wherein the assembly is arranged such that the shifting sleeves are capable of being opened (and/or closed) sequentially.

The sleeves may be opened in sequence from the furthest downhole towards surface.

There is provided a downhole apparatus or assembly, or screen or screen assembly, such as a downhole/sand screen assembly, comprising a pipe having a port and an inner sleeve and a pin within the port.

The pin may cause rotational locking or alignment between the pipe and the sleeve.

There is provided a screen, or screen assembly, such as a downhole/sand screen or screen assembly, having enhanced erosion resistance.

It will be appreciated that the foregoing general solutions of the present invention may be combined. It will be appreciated that any feature or features of one general solution of the present invention may be adopted or used in another general solution.

Any feature(s) of any one general solution may be combined with any feature(s) of any other general solution. Thus feature(s) defined in relation to one general solution may be provided in combination with feature(s) of any other general solution.

It will be appreciated that the pipe (or tubular) and/or the screen, first and/or second screens and/or the further screen may each comprise a hollow cylindrical shape, and may be disposed substantially co-axially, the sleeve typically surrounding the pipe.

The screen or screen assembly may be configurable for one or more of fluid injection, stimulation, fracturing and/or production.

The pipe may comprise production tubing.

The pipe may comprise a first tubular. The pipe may be permeable or impermeable.

The pipe may comprise a perforated tubular member or tubular member having a plurality of ports or may comprise a solid walled tubular member.

The screen or sleeve (e.g. outer sleeve) may comprise a second tubular. The screen or sleeve (e.g. outer sleeve) may be permeable.

The pipe may be disposed within a or the sleeve (e.g. outer sleeve).

The pipe may define an axial through-bore.

An annulus may be provided between the pipe and the sleeve (e.g. outer sleeve).

The (further) sleeve(s), e.g. sliding sleeves, may comprise further tubulars.

The wire may be circumferentially disposed or wound.

Embodiments of the present invention will now be described by way of example only and with reference to accompanying drawings which are:.

Referring to <FIG>, there is illustrated a screen or sand screen, generally designated 5a, operatively positioned in a subterranean well-bore 10a adjacent to a formation 15a which has been lined with protective casing 20a. The casing 20a has been perforated 21a to permit fluid flow between formation 15a and well-bore 10a. Screen 5a is suspended from pipe or production tubing 25a which extends to a well-head 30a and comprises a permeable sleeve 31a formed from wire.

During production of fluids - represented by arrows 35a - from the formation 15a, the fluids enter the screen 5a and are transported to the well-head through the tubing 25a. Any sand in the fluid 35a should be filtered out by the screen 5a and not permitted to flow into the pipe 25a. The screen 5a is gradually eroded over time as the fluid 35a flows through the screen 5a. Higher rates of flow of the fluid 35a through the screen 5a cause faster erosion of the screen 5a. The screen 5a can also be used for injection of fluids into the formation - in a direction opposite to the arrows 35a.

If the rate of flow of the fluid through a particular perforation 21a is greater than the rate of flow of the fluid 35a through the other perforations 21a - as is frequently the case in gas wells - a portion 45a of the screen 5a opposite the high flow rate perforation 21a will erode faster than another portion or portions of the screen 5a. When the portion 45a of the screen 5a has eroded enough to permit sand and other debris to enter the tubing, the entire screen 5a must be replaced at great cost to the well operator, even though most of the screen 5a is not yet eroded.

Referring next to <FIG>, there is illustrated an alternative screen or sand screen, generally designated 5b. The screen 5b is shown within a well-bore 10b of an earth formation 15b. The screen 5b has a cylindrical sleeve or foam body 50b, which in one implementation is an open cell foam body which surrounds a pipe or tubular 25b positioned within a through-bore or void 55b that extends longitudinally through the foam body or sleeve 50b. The foam body or sleeve 50b is an open cell structured foam which allows fluid to flow therethrough from an outside of the screen 5b, defined by an outer surface, to the void 55b. The cell structured foam provides filtering of fluid passing therethrough. Perforations or ports 40b in the pipe 25b allow fluid passing through the screen 5b to flow to an inside of the through-bore 55b. Once the fluid is on an inside of the through-bore 55b the fluid can flow longitudinally through the pipe 25b in either direction. Fluid initially on the inside of the throughbore 55b can also flow out through the perforations 40b, through the open cell structured foam and to the outside.

Referring now to <FIG> there is shown a screen, such as a downhole/sand screen, 5c according to the prior art. The screen 5c comprises a pipe (tubular) 25c and a sleeve (permeable sleeve) 31c and a plurality of circumferentially disposed supports 32c provided between the pipe 25c and the sleeve 31c, wherein each support 32c has a cross-section comprising a triangular shape.

Further the sleeve 31c comprises wire 33c which has a cross-section comprising a further triangular shape. The wire 33c is circumferentially disposed or wound.

There will now be illustrated, by way of non-limiting example only, a number of screens or screen assemblies which may find utility in well-bore completions as shown in <FIG> and/or <FIG>.

Referring now to <FIG>, there is shown a screen or screen assembly <NUM>, such as a downhole/sand screen or screen assembly, comprising a pipe <NUM> and a sleeve <NUM> and at least one support <NUM> provided between the pipe <NUM> and the sleeve <NUM>, wherein the at least one support <NUM> has a cross-section comprising first and second points or vertices or surface discontinuities or corners <NUM>. Such support shape can provide enhanced erosion resistance.

The pipe <NUM> can be referred to as a base pipe or production pipe or tubing. The pipe is perforated and comprises a plurality of ports <NUM>. The first and second points, vertices, surface discontinuities or corners <NUM> (hereinafter 'points')comprise a pair of points <NUM>. The first and second points <NUM> face in substantially opposing directions along a radius or radial direction.

The at least one support <NUM> comprises a plurality of supports <NUM>, i.e. axial supports and/or support rods. The supports <NUM> are disposed in an annular space between the pipe <NUM> and the sleeve <NUM>.

In one implementation (shown in <FIG>) the/each support <NUM> has a cross-section comprising a polygon having at least four sides, parallelogram, rectilinear, square or diamond shape.

In another implementation (shown in <FIG>) the/each support <NUM>' has a cross-section comprising a polygon having six sides, i.e. a polygon having opposing triangular end portions and a rectilinear or square mid-portion.

A first point <NUM>; <NUM>' is welded to the pipe <NUM>; <NUM>', i.e. an outer surface of the pipe. A second point <NUM>; <NUM>'; <NUM>; <NUM>' is welded to the sleeve <NUM>; <NUM>' i.e. an inner surface of the sleeve <NUM>.

The support(s) is/are typically made from steel.

Referring next to <FIG>, there is shown a screen or screen assembly <NUM>, such as a downhole/sand screen or screen assembly, comprising wire <NUM> having a cross-section comprising first and second points or vertices or surface discontinuities or corners <NUM>. Such wire shape can provide enhanced erosion resistance.

The first and second points, vertices, surface discontinuities or corners <NUM> (hereinafter 'points') comprise a pair of points <NUM>. The first and second points <NUM> face in substantially opposing directions, e.g. along a radius or radial direction.

The screen <NUM> comprises a pipe <NUM> and a sleeve <NUM> (the sleeve <NUM> comprising the wire233/screen), and at least one support <NUM>. The pipe <NUM> can be referred to as a base pipe or production tubing. The at least one support <NUM> comprises a plurality <NUM> of supports, e.g. axial supports and/or support rods. The supports <NUM> are disposed in an annular space <NUM> between the pipe <NUM> and the sleeve <NUM>.

In one implementation (shown in <FIG>) the/each wire <NUM> has a cross-section comprising a polygon having at least four sides or diamond shape.

In another implementation (shown in <FIG>) the/each wire <NUM>' has a cross-section comprising a polygon having six sides, e.g. a polygon having opposing triangular end portions and a rectilinear or square mid-portion.

A first point <NUM>; <NUM>' is welded to a support <NUM>; <NUM>', e.g. an outer surface of the support <NUM>; <NUM>'. A second point <NUM>; <NUM>' faces radially out, e.g. towards a formation or inner facing surface of a well-bore.

The wire <NUM>; <NUM>' is typically made from steel.

Referring next to <FIG> there is shown a screen or screen assembly <NUM>, such as a downhole/sand screen or screen assembly, wherein the screen <NUM> comprises wire <NUM> having a cross-section comprising a rectilinear or square shape. Such wire shape can provide enhanced erosion resistance.

The rectilinear shape comprises a rectangle or in this preferred implementation comprises a square. The wire <NUM> is disposed such that a line of symmetry of the rectilinear shape is provided along a radial direction of the screen <NUM> or pipe <NUM>.

The screen <NUM> comprises a pipe <NUM> and a sleeve <NUM> (the sleeve comprising the wire/screen), and at least one support <NUM>. A side of the wire <NUM> is welded to the support(s) <NUM>.

Referring next to <FIG> there is shown a screen or screen assembly <NUM>', such as a downhole/sand screen or screen assembly. The screen <NUM>' is similar to the screen <NUM>, like ports being identified by like numerals but suffixed ‴.

Referring next to <FIG> there is shown a screen or screen assembly <NUM>", such as a downhole/sand screen or assembly. The screen <NUM>" is similar to the screen <NUM>; <NUM>' like ports being identified by like numerals, but suffixed ʺʺ. In the screen <NUM>" of <FIG> the pipe <NUM> comprise a tubular having a solid wall, i.e. which is not perforated.

Where wrap wires <NUM>; <NUM>'; <NUM>" of a square cross-section are used to construct the filter media the smooth passage created under such will reduce turbulence and tend flow to continue longitudinally. This can promote a more even distribution of injection fluid through the wire wrap <NUM>; <NUM>'; <NUM>".

The construction of the filter media can be used in situations where the base pipe is perforated (shown in <FIG> and <FIG>) or where the base pipe is imperforated (shown in <FIG>) and flow enters the annulus between the base pipe and the wrap wires at a point lower down the sand screen joint.

It will be appreciated any combination of shape of wire (wire wrap) and/or support is possible, e.g. wire and/or supports selected from triangular, diamond shape, hexagonal, elongate hexagonal, square or rectangular cross-sectional shape (though not both triangular). It will be appreciated that any such combination of wire and support shape may provide enhanced erosion resistance in at least one of injection and production.

Regarding the wire of the screen or screen assembly of <FIG>, <FIG>, <FIG>, <FIG>, or indeed <FIG>, the wire comprises coated and/or hardened wire <NUM>; <NUM>'; <NUM>; <NUM>'; <NUM>"; 333c. The wire can beneficially be made from steel.

The screen comprises a pipe and a sleeve, the sleeve comprising the wire, and optionally at least one support.

In one implementation the coating is tungsten carbide, e.g. hardide tungsten carbide. The coating is applied or deposited by chemical vapour deposition (CVD), which can be applied to steel. The wire can be heat treated so as to harden.

The wire can be provided in coated and/or hardened lengths and made-up or assembled in longer lengths so as to provide the sleeve.

Referring next to <FIG> and <FIG> there is shown a screen or screen assembly <NUM>; <NUM>', such as a downhole or sand screen or screen assembly, comprising a pipe <NUM>; <NUM>' and a plurality of ceramic discs <NUM>; <NUM>' around the pipe <NUM>; <NUM>'. High hardness of the ceramic provides enhanced erosion resistance.

The ceramic discs <NUM>; <NUM>' are stacked on each other. Gaps between the discs <NUM>; <NUM>' determine a size of particulate to be filtered, and can be modified to suit a well and a specification of an operator.

The pipe <NUM> can be referred to as a base pipe or production tubing. In one implementation (see <FIG>) the pipe <NUM> is perforated and/or comprises a plurality of ports <NUM>. The pipe <NUM> is slotted. In another implementation (see <FIG>) the pipe <NUM>' is non-permeable or solid.

The pipe <NUM> comprises a plurality of ports <NUM>, e.g. slots, e.g. circumferentially and axially spaced thereupon.

One or more of the discs <NUM>; <NUM>' are arranged so as to provide circumferential/annular spaces <NUM>; <NUM>' between the pipe <NUM>; <NUM>' and the respective disc <NUM>; <NUM>'.

Between adjacent circumferential/annular spaces <NUM>; <NUM>' the disc(s) <NUM>; <NUM>' are arranged such that there is no gap between the pipe <NUM>; <NUM>' and the disc <NUM>; <NUM>'. Such arrangement is provided by portions of the disc <NUM>; <NUM>' having reduced internal diameter, i.e. such that the pipe <NUM>; <NUM>' and the disc(s) <NUM>; <NUM>' radially abut or contact one another at said portions.

The space(s) <NUM>; <NUM>' extend longitudinally between adjacent discs <NUM>; <NUM>'. The space(s) <NUM>; <NUM>' are aligned, i.e. rotationally aligned, with at least one port <NUM> in the pipe <NUM>; <NUM>'.

A valve member <NUM> is provided between a port <NUM> and a respective space <NUM>. The/each valve member <NUM> comprises a slidable member, i.e. longitudinally slidable member. Each valve member <NUM> comprises at least one further port <NUM> and/or at least one reed valve <NUM>, which is/are (longitudinally) selectively alignable with or out of alignment with a port <NUM> of the pipe <NUM>.

The screen or screen assembly also comprises an inner sleeve <NUM> (see <FIG>). The inner sleeve <NUM> is slidable relative to the pipe <NUM>. An outer surface of the inner sleeve <NUM> abuts or contacts an inner surface of the pipe <NUM>.

The inner sleeve <NUM> comprises at least one yet further port <NUM> and/or further reed valve <NUM>, which is/are (longitudinally) selectively alignable with or out of alignment with a port <NUM> of the pipe <NUM>.

Referring to <FIG>, there is shown a screen or screen assembly <NUM>, such as a downhole screen or screen assembly, comprising a pipe <NUM>' and/or sleeve comprising discs <NUM>', wherein the pipe comprises a solid or non-perforated pipe <NUM>'. Such arrangement can provide enhanced erosion resistance. The solid or non-perforated pipe <NUM>' can comprise or be provided with an opening(s) or port(s) at or adjacent an end(s) thereof, e.g. to deliver injection fluid to a formation.

Referring to <FIG> there is shown a screen or screen assembly <NUM>, such as a downhole/sand screen or screen assembly, comprising a pipe <NUM> and a sleeve <NUM>, wherein the pipe <NUM> comprises openings or slots (e.g. longitudinally or axially opening(s) or slot(s)) <NUM> and the sleeve <NUM> comprises a foam or microporous material the sleeve <NUM> being bonded with or to an exterior surface of the pipe. Such arrangement can provide enhanced erosion resistance. Such arrangement can provide relatively even distribution of injection fluids.

The pipe can be referred to as a base pipe or production tubing. The openings or slots can comprise daisy passages. The opening or slots, in use, fluidically communicate with the sleeve.

Referring to <FIG>, there is shown a screen or screen assembly <NUM>', such as a downhole/sand screen or screen assembly, comprising a pipe <NUM>' and a microporous sleeve <NUM>', wherein the pipe <NUM>' comprises a plurality of slotted ports <NUM>' or longitudinally extending ports <NUM>'. Such arrangement can provide enhanced erosion resistance, and operates in a similar manner to the screen of <FIG>.

The pipe is typically referred to as base pipe or production tubing.

Where provided the microporous sleeve <NUM>; <NUM>'can be an erosion resistant microporous sleeve. The microporous sleeve <NUM>; <NUM>' comprises a material selected from a metal foam or a ceramic foam. The microporous sleeve <NUM>; <NUM>' comprises a material selected from the group consisting of microporous polymeric foams, microporous metal foams, microporous carbide monoliths, in particular, silicon carbide, tungsten carbide, or titanium carbide monoliths or microporous nitride monoliths, such as boron nitride. The microporous sleeve <NUM>; <NUM>' intimately contacts and/or is bonded to an outer surface of the pipe <NUM>; <NUM>'.

Referring now to <FIG>, <FIG>, <FIG> and <FIG> there is shown screens or screen assemblies <NUM>; <NUM>; <NUM>; <NUM>', such as a downhole/sand screen or screen assembly, comprising a pipe <NUM>; <NUM>; <NUM>; <NUM>' having at least one port <NUM>; <NUM>; <NUM>; <NUM>' or perforation or hole, the/each port <NUM>; <NUM>; <NUM>; <NUM>' or perforation or hole having an associated valve <NUM>; <NUM>; <NUM>; <NUM>'.

The pipe <NUM>; <NUM>; <NUM>; <NUM>' can be referred to as a base pipe or production tubing. The/each valve <NUM>; <NUM>; <NUM>; <NUM>' can be a check valve.

The pipe <NUM>; <NUM>; <NUM>; <NUM>' comprises a plurality of ports <NUM>; <NUM>; <NUM>; <NUM>' or perforations, each port <NUM>; <NUM>; <NUM>; <NUM>' or perforation having an associated valve <NUM>; <NUM>; <NUM>; <NUM>'.

The/each valve <NUM>; <NUM>; <NUM>; <NUM>' is, in use, initially provided to isolate the inner diameter of the pipe <NUM>; <NUM>; <NUM>; <NUM>' from the outer diameter of the pipe <NUM>; <NUM>; <NUM>; <NUM>'. Upon opening the valve(s) <NUM>; <NUM>; <NUM>; <NUM>' the provision of multiple ports/perforations/holes in the pipe <NUM>; <NUM>; <NUM>; <NUM>' provides improved distribution of injection fluid. The/each valve <NUM>; <NUM>; <NUM>; <NUM>' comprises a valve member.

The/each valve member <NUM>; <NUM>; <NUM>' is deployable by a sliding sleeve <NUM>; <NUM>; <NUM>' and/or by pressure of fluid flow, in use.

The sliding sleeve <NUM>; <NUM>; <NUM>' can slide relative to an inner surface of the pipe <NUM>; <NUM>; <NUM>'. The sliding sleeve <NUM>; <NUM>; <NUM>' comprises a port(s) <NUM>; <NUM>; <NUM>' which is controllably aligned with ports <NUM>; <NUM>; <NUM>' of the pipe <NUM>; <NUM>; <NUM>'.

The valve member(s) <NUM>; <NUM>; <NUM>' may be biased into a closed position, e.g. by biasing means <NUM>; <NUM>; <NUM>'.

In one implementation (see <FIG>) the valve member(s) <NUM> comprises a spherical member(s) or balls, e.g. biased spherical member(s). The/each spherical member or ball is provided, i.e. movably provided, within a space provided by a port in the pipe and a recessed portion in a sleeve.

Referring to Figure <NUM>(d), when run-in hole the balls are press-fitted within a hole(s) in the base pipe, as shown. The balls are supported by a sliding sleeve preventing differential pressure from a outside passing through the filter media and forcing them through the base pipe. Pressure is isolated between the outside and the inside of the base pipe via seals positioned on the outer diameter (OD) of a (long) sliding sleeve.

Referring to <FIG>, when ready to open the sand screen up to flow, a short shift of the base pipe will cause the recessed area in the sliding sleeve to push the balls out of their respective holes in the base pipe; the new surface against which the balls rest prevents differential pressure from the outside passing through the filter media and pushing the balls back into the press fitted condition. Flow ports in the (long) sliding sleeve are now exposed below the balls and a seal in the port within the base pipe provides a pressure check preventing differential pressure from production flow passing into the sand screen. A (weak) spring excerpts (gentle) pressure on the ball allowing it to seal at low differential pressures.

Referring to <FIG>, when subjected to injection flow the balls lift off of their respective seats and compress the (weak) spring allowing flow to pass into the filter media.

Referring to <FIG> in the screen <NUM>, the perforated base pipe <NUM> can be sealed off by a number of sliding sleeves <NUM>. These can all be locked in place (opened and closed) by means of latch fingers. Each sleeve <NUM> has a shift profile with a kick-down shoulder on the rear of the sleeve <NUM> above it, meaning that as the sift tool can be pulled through, the shift tool pulls open the sleeve and auto-out from the above kick-down shoulder whereupon it latches into the next profile and opens that, and so on.

Referring to <FIG> there is shown a screen or screen assembly <NUM>', similar to the screen <NUM> of <FIG>, like ports being identified by the numerals but suffixed ‴.

In the screen <NUM>', the topmost sleeve <NUM>' has a shifting pole. The rest of the sleeves <NUM>' are closely linked so that they all open at the same time, but are segmented to account for concentricity, friction, bends etc..

In another implementation the valve member(s) comprise a flap, i.e. thin metallic or steel flap, or reed valve.

Referring next to <FIG> there is shown a screen or screen assembly <NUM>, such as a downhole/sand screen or screen assembly, comprising a pipe <NUM> having at least one port or perforation or hole <NUM>, and a sleeve <NUM> provided within the pipe <NUM>, the sleeve <NUM> having at least one respective port or perforation or hole <NUM> which in a closed position is not aligned or is misaligned with the at least one port or perforation or hole <NUM> in or on the pipe <NUM> but which in an open position is alignable or aligned with the at least one port or perforation or hole <NUM> in or on the pipe <NUM>. The pipe <NUM> can be referred to as a base pipe or production tubing.

The sleeve <NUM> (internal sleeve) comprises a shift sleeve. The sleeve <NUM> is slidable relative to the pipe <NUM> so as to move from a closed to open position and optionally vice versa.

The pipe <NUM> comprises a plurality of ports or perforations or holes <NUM>. The/each sleeve <NUM> (internal sleeve) comprises a plurality of respective ports or perforations or holes <NUM>. The presence of multiple ports/perforations/holes allows for improved distribution of injection fluid. The screen <NUM> comprises an (outer) screen sleeve <NUM>, e.g. comprising wire.

Referring again to <FIG> there is shown a screen or screen assembly <NUM>, such as a downhole/sand screen or screen assembly, comprising a pipe <NUM>, and a plurality of inner sliding sleeves 785a; 785b provided within the pipe <NUM>.

The pipe <NUM> can be referred to as a base pipe or production tubing.

The sleeves 785a, 785b are provided within the pipe <NUM>. The sleeves 785a, 785b each comprise a sliding/shift sleeve. There are provided first and second sleeves 785a; 785b, one within the other.

Movement, i.e. sequential movement of the sleeves, causes alignment or misalignment, of ports in the pipe <NUM> and the sleeve(s) 785a; 785b, e.g. opening or closing, of the screen. Sliding movement of a first sleeve 785a causes sliding movement of a second sleeve 785b, i.e. to open the screen <NUM>. Sliding movement of a second sleeve 785b causes sliding movement of a first sleeve 785a, i.e. to close the screen <NUM>.

Referring yet again to <FIG> there is shown a screen or screen assembly <NUM>, such as a downhole/sand screen or screen assembly, comprising a pipe <NUM> comprising at least one port/perforation/hole <NUM>, the or each port <NUM> having a respective seal <NUM>.

The pipe <NUM> can be referred to as a base pipe or production tubing. The pipe <NUM> comprises a plurality of ports <NUM>.

In a closed disposition the respective plug <NUM> is received or be provided within or adjacent to the respective port <NUM>. In an open disposition the respective plug <NUM> is provided distal the respective port <NUM>. The plug(s) <NUM> are carried by a sleeve 785a, i.e. on an outer surface of a shifting/sliding sleeve provided within the pipe <NUM>.

Referring to <FIG> there is shown a modification to the screen <NUM> of <FIG>. In the modified screen <NUM>' shown in <FIG> like parts are identified by like numerals but suffixed ‴.

In the screen <NUM>' the seal <NUM>' has plastic back-ups <NUM>'.

Referring to <FIG>, with the seal <NUM>' in place, the seal <NUM>' is compressed against the hole <NUM>' in the base pipe <NUM>'. A pressure differential from either direction will energise the seal <NUM>' and act to ensure pressure integrity. Referring to <FIG>, sliding the inner sleeve 785b' de-supports the finger sleeve 785a' and relaxes compression in the seal <NUM>'. Referring to <FIG>, the finger sleeve <NUM>' can now be slid to expose the hole <NUM>'.

There is also provided a screen assembly, such as a downhole/sand screen assembly, comprising a first screen <NUM>; <NUM>; <NUM>; <NUM>'; <NUM>"; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>'; <NUM>' <NUM>' and a second screen 5c.

The first screen <NUM> and second screen 5c are longitudinally disposed relative to one another. The first screen can be selected to be provided in high(er) flow areas, i.e. production and/or particularly injection fluid flow areas. The second screen 5c can be selected to be provided in low(er) flow areas, i.e. production and/or injection fluid flow areas. The second screen can comprise wire having a cross-section comprising a triangular shape (see <FIG>).

Referring to <FIG> there is shown a screen assembly <NUM>, such as a downhole/sand screen assembly, comprising a first screen 1005a and a second screen 1005b. The pipe <NUM> is non-perforated. The first screen 1005a has a higher erosion resistance than the screen 1005b. The first screen 1005a is a screen, e.g. comprising ceramic discs. The second screen 1005b can be a screen according to the prior art.

<FIG> show injection and production fluid flow respectively. The pipe <NUM> comprises a port <NUM> longitudinally distal the screens 1005a, 1005b.

For sand screen configurations where production or injection flow enters or exits the base pipe <NUM> from a single point at one or either end of the sand screen <NUM>, the flow will tend to take the path of least resistance and the majority of the flow will enter or exit a section of sleeve 1031a or filter media closest to that point. By incorporating a highly erosion resistant portion of the screen 1005a closest to the flow port/s <NUM>, the erosion effect of the high volume, high velocity flow in this area can be mitigated. The screen 1005a can comprise ceramic discs. The remainder of the screen 1005b area will be less susceptible to erosion due to the reduced flow rates and velocities, therefore, can be made up of a more conventional filter media type such as metal mesh or wire wrap, e.g. of trianguler cross-section.

Referring now to Figures <NUM>(a) - (i) there is shown a screen or screen assembly <NUM>', such as a downhole/sand screen or screen assembly, comprising a pipe <NUM>' and a sleeve <NUM>', wherein the pipe <NUM>' comprises a port(s) <NUM>', and where the sleeve <NUM>' comprises a solid or wall portion(s) <NUM>' at or near the port(s) <NUM>'.

The solid or wall portions <NUM>' are provided radially outwardly of the ports <NUM>'.

The pipe <NUM>' can be referred to as a base pipe or production tubing.

The port(s) <NUM>' are provided on the pipe <NUM>' and/or at each end of the pipe, in the latter case the pipe optionally having a solid wall. The solid or wall portion(s) <NUM>' are provided radially adjacent the port(s), i.e. radially outward of the port(s).

This arrangement can provide that injection flow, i.e. high rate injection flow may meet or hit a solid or wall portion, change direction and flow axially along an annulus between the pipe <NUM>' and the sleeve <NUM>'. In this way an area of highest erosion is deflected to an area of pipe <NUM>' having a solid outer wall.

Referring next to <FIG>, there is shown a screen assembly 890a; 890b, such as a downhole/sand screen assembly, comprising first and second screens 805a; 805b longitudinally coupled together, wherein there is provided a fluid flow path 891a; 891b between the first and second screens 805a; 805b.

The first screen 805a; 805b comprises a first pipe 825a; 825b and a first sleeve 831a; 831b. The second screen 805a; 805b comprises a second pipe 825a; 825b and a second sleeve 831a; 831b. The first and second pipes 825a; 825b are coupled by a coupling, i.e. a threaded coupling 892a; 892b.

The first and second sleeves are coupled, i.e. by first and second support rings 893a; 894a; 893b; 894b and a centraliser or further sleeve or screen 895a; 895b.

Referring to <FIG>, there is shown a screen assembly 890a, such as a downhole/sand screen assembly, comprising first and second screens 805a longitudinally disposed relative to one another, wherein a centraliser 895a is provided between adjacent ends of the first and second screens 805a.

A first support ring 893a is provided between an end of a sleeve 831a of the first screen and a first end of the centraliser 895a. A second support ring 894a is provided between an end of a sleeve 831a of the second screen and a second end of the centraliser 895a.

Referring to <FIG>, there is shown a screen assembly 890b, such as a downhole/sand screen assembly, comprising first and second screens longitudinally disposed relative to one another, wherein a further screen 895b or screen portion is provided between adjacent ends of the first and second screens 805b.

A first support ring 893b is provided between an end of a sleeve 851b of the first screen and a first end of the further screen 895b. A second support ring 894b is provided between an end of a sleeve 831b of the second screen and a second end of the further screen 895b.

Referring to <FIG>, there is shown a screen or screen assembly <NUM>", such as a downhole or sand screen or screen assembly, comprising a pipe <NUM>" and a plurality of ceramic discs <NUM>" around the pipe <NUM>".

The ceramic discs <NUM>" are stacked on each other. Gaps between discs <NUM>" determine a size of particulate to be filtered, and can be modified to suit a well and specification of an operator.

At least one spacer <NUM>" is provided between at least two adjacent discs <NUM>", wherein the/each at least spacer <NUM>" is aligned with a respective hole <NUM>" or slot or perforation in the pipe <NUM>".

Such provides enhanced erosion resistance.

The pipe <NUM>" can be referred to as a base pipe or production tubing.

The/each spacer <NUM>" is shaped to diffuse fluid flow exiting a hole <NUM>" or slot of perforation in the pipe <NUM>". The spacer <NUM>" comprises first and second surfaces <NUM>"a, <NUM>"b. The first and second surfaces <NUM>"a, <NUM>"b are concave and face in opposing directions. Each of the first and second surface <NUM>"a, <NUM>"b is radially diverging.

The discs <NUM>" are provided around the pipe <NUM>". Beneficially each spacer <NUM>" is integrally formed with a disc <NUM>". Beneficially each disc <NUM>" and/or each spacer <NUM>" is made from a ceramic material.

As shown in <FIG>, in this implementation, a plurality of longitudinally adjacent discs <NUM>" provide a plurality of circumferentially adjacent spacers <NUM>". Such are rotationally aligned with a hole/slot/perforation <NUM>" in the pipe <NUM>".

The discs <NUM>" provide a filter media. Adjacent discs <NUM>" are spaced from one another, e.g. by the spacer(s) <NUM>". The spacer(s) <NUM>" are provided on a surface or face of the/each disc <NUM>". Spacer(s) <NUM>" are provided around the surface or face of the/each disc <NUM>". As can be seen from <FIG> an outer sleeve is provided around the discs <NUM>". The outer sleeve which can be metallic protects the discs <NUM>" during run-in.

Referring to <FIG> there is shown a screen or screen assembly, such as a downhole screen or screen assembly <NUM>.

'X' shows the distance between the inner diameter (ID) of the borehole and the outer diameter (OD) of a sand screen (dashed line). Within the (outer) sand screen (dashed line) is a pipe or base pipe A. In or on the base pipe A is a joint B. The joint B is a threaded connection between two sections of base pipe ('C' indicates threads). The joint B has an additional function - it protrudes into throughbore D and presents an incline E to act as a kick down shoulder. Sleeve F provides ports G. The ports G can be aligned with ports H in the base pipe when the sleeve F is moved. The sleeve F has a recess I on the inner surface (on the left hand side) to accept keys that lock the sleeve F to a shifting tool (not shown).

In operation, keys on a shifting tool are biased outwardly, and as the shifting tool is pulled up the throughbore D, the keys engage with the profile on the inner surface of the sleeve F. Once the shifting tool keys are locked into the sleeve F, the shifting tool is pulled to align the ports G in the sleeve F and the base pipe ports H. Once the sleeve F has reached its full extent of travel, the joint B provides a shoulder stop for the shifting sleeve F and the keys on the shifting tool B. This releases the keys and disengages the shifting tool from the sleeve F. The process can be repeated for the next sleeve etc..

This arrangement provides for "buttom-up opening" of shifting sleeves.

Referring now to <FIG>, there is shown a downhole assembly or screen or screen assembly <NUM>. Pipe A provides lateral ports H. A pin J is in the first of these ports H. The pin J can run in a groove to ensure axial alignment of the sleeve F and restrict rotation. Once the sleeve F has reached the full extent of travel, the pin J can drop into a groove to lock the sleeve F in place. The pin J acts as an anti-rotation key.

It will be appreciated that the embodiments of the present invention may be combined. It will also be appreciated that any feature or features of one embodiment of the invention may be adopted or used in another embodiment of the invention. Any feature(s) described or referenced herein may be combined with any feature(s) of any other embodiment. Thus feature(s) defined in relation to one embodiment may be provided in combination with feature(s) of any other embodiment.

It will be appreciated that the pipe (or tubular) and/or the sleeve each comprise a hollow cylindrical shape, and are disposed substantially co-axially, the sleeve typically surrounding the pipe.

Claim 1:
A downhole screen assembly (890a) for use in the production of fluids, comprising first and second screens (<NUM>, <NUM>', 805a) longitudinally coupled together by a coupling (892a), wherein the first screen (<NUM>, 805a) comprises a first pipe (<NUM>, 825a) and a first permeable sleeve (831a) and the second screen (<NUM>', 805a) comprises a second pipe (<NUM>', 825a) and a second permeable sleeve (831a), and wherein the coupling (892a) couples the first and second pipes (<NUM>, <NUM>', 825a) and provides a fluid flow path (891a) between the first and second screens (<NUM>, <NUM>', 805a),
wherein the first and second sleeves (831a) are coupled by a centraliser (895a),
wherein the centraliser (895a) forms a portion of the fluid flow path (891a) and the first and second screens (<NUM>, <NUM>', 805a) extend circumferentially around the first and second pipes (<NUM>, <NUM>', 825a), and
wherein the first pipe (<NUM>, 825a) comprises a plurality of ports (<NUM>), each port (<NUM>) having an associated valve (<NUM>),
wherein the second pipe (<NUM>', 825a) comprises a solid or non-perforated pipe (<NUM>');
wherein the centraliser (895a) is provided between adjacent ends of the first and second screens (<NUM>, <NUM>', 805a).