Downhole apparatus

Abstract

There is provided a sandscreen joint (110) capable of providing zonal isolation. The ends of the portion of the (110) are capable of extension on activation of the sandscreen (110), including transition areas (135), which are coated with an elastomer sleeve (134). On activation of the sandscreen (110), the sleeve (134) is pushed out into contact with the bore wall and serves to isolate the zone on one side of the activated sleeve (134) from the zone on the other side of the sleeve (134). Thus, the provision of the sleeve (134) on the activated sandscreen (110) may prevent fluid from flowing axially along the bore between the bore wall and sandscreen. This may serve to protect the weave at the transition area (135), preventing axial flow through the transition areas (135).

Claims

1. A method of producing downhole apparatus, comprising: forming openings in a sheet, and then at least partially closing the openings, the sheet being adapted to form an element of a tubular member; forming the tubular member with the sheet as an element on an outer surface thereof; forming a shroud around a filter media of a sand screen with the tubular member, the sand screen expandable or otherwise configurable in an activated extended configuration, and on activation of the sand screen from a retracted configuration, the at least partially closed openings in the sheet open to permit flow in through the shroud; providing an inflatable element beneath the filter media, a base pipe beneath the inflatable element and an inflation valve for controlling flow of inflation fluid between the base pipe and the inflatable element, the inflation valve being initially closed to maintain the sand screen in the retracted configuration and the at least partially closed openings in the closed configuration; and, providing an indexing profile and a follower pin for controlling movement of the inflation valve.

2. The method of claim 1, comprising initially forming the openings in the sheet by any one of punching, die casting and machining.

3. The method of claim 1, comprising closing at least one of the openings over a portion of the length of the opening or completely over the length of the opening.

4. The method of claim 1, comprising using the tubular member to provide a degree of protection for the filter media member during run-in of the sand screen.

5. The method of claim 1, comprising providing the tubular member with a smooth outer surface for minimising friction between the tubular member and a bore wall as the tubular member is run into the bore.

6. The method of claim 1, comprising providing the sheet in tubular form when the openings are formed, or providing the sheet in planar form when the openings are formed.

7. The method of claim 1, comprising providing the sheet in tubular form when the openings are at least partially closed, or providing the sheet in planar form when the openings are at least partially closed, and subsequently configuring the planar sheet in a tubular form.

8. The method of claim 1, comprising at least partially closing the openings by reducing the surface area of the sheet.

9. The method of claim 1, comprising providing the sheet in tubular form, and partially closing the openings by running the sheet through a die.

10. The method of claim 1, wherein the follower pin is disposed in a first leg of the indexing profile when the inflation valve is initially closed, and the follower pin is movable to a second leg of the indexing profile to open the inflation valve.

11. The method of claim 10, further comprising providing the indexing profile with a third leg, wherein the follower pin is movable to the third leg to close and lock the inflation valve.

12. The method of claim 1, further comprising polishing the tubular member with the at least partially closed openings in the closed configuration.

13. A downhole apparatus comprising: a filter media; at least one expandable apparatus having a retracted configuration and operable to radially extend in response to activation thereof; a protective cylindrical shroud provided over the filter media, the protective cylindrical shroud defining a tubular member comprising a wall including slots formed therethrough, the slots assuming an initial closed form when the at least one expandable apparatus is in the retracted configuration and configured to move to an open form to define inflow openings through the wall in response to activation of the at least one expandable apparatus which is configured to expand the tubular member an inflatable element beneath the filter media, a base pipe beneath the inflatable element and an inflation valve for controlling flow of inflation fluid between the base pipe and the inflatable element, the inflation valve being initially closed to maintain the expandable apparatus in the retracted configuration and the slots in the initial closed form; and an indexing profile and a follower pin for controlling movement of the inflation valve.

14. The downhole apparatus of claim 13, wherein the expandable apparatus comprises a sand screen.

15. The downhole apparatus of claim 13, wherein the tubular member is formed in accordance with claim 1.

16. The downhole apparatus of claim 13, wherein the tubular member is formed by part cutting portions of a sheet such that on extension of the sheet the part cut portions open to create inflow openings.

17. The downhole apparatus of claim 13, wherein the slots include enlarged ends, and wherein the enlarged ends are open both when the slots are in the open form and when the slots are in the closed form.

18. The down hole apparatus of claim 17, wherein the slots further comprise a pair of elongated edges extending between the enlarged ends, wherein the elongated edges are spaced from one another when the slots are in the open form and wherein the elongated edges engage one another when the slots are in the closed form.

19. The downhole apparatus of claim 13, wherein the follower pin is disposed in a first leg of the indexing profile when the inflation valve is initially closed, and wherein the follower pin is movable to a second leg of the indexing profile to open the inflation valve and movable to a third leg of the indexing profile to close and lock the inflation valve, wherein the first second and third legs of the indexing profile are generally parallel, axially-extending slots interconnected with one another by oblique slots.

20. The downhole apparatus of claim 13, wherein the tubular member is polished with the slots in the initial closed form.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) These and other aspects of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:

(2) FIG. 1 is a schematic illustration of part of a completion including three sand screens;

(3) FIG. 2 is a part cut-away view of part of one of the screens of FIG. 1;

(4) FIG. 3 corresponds to FIG. 2 but shows the screen in an activated configuration;

(5) FIGS. 4a and 4b show a sandscreen joint in accordance with an embodiment of the present invention;

(6) FIGS. 5 and 6 show details of the joint of FIGS. 4a to 4b;

(7) FIGS. 7a, 7b and 7c, and 8a and 8b show combined sandscreen and zonal isolator joints in accordance with embodiments of the present invention;

(8) FIGS. 9a and 9b show a plan view of a sheet defining a plurality of openings, for use in forming a shroud, in accordance with an embodiment of the present invention;

(9) FIGS. 10a, 10b and 10c show a slot form of the sheet of FIGS. 9a and 9b;

(10) FIG. 11 is a partially exploded view of a section of sandscreen in accordance with an embodiment of the present invention;

(11) FIG. 12 is a part cut-away view of the sandscreen section of FIG. 11;

(12) FIG. 13 is a sectional view of the sandscreen of FIG. 11;

(13) FIG. 14 is a partially exploded view of a section of alternative sandscreen in accordance with an embodiment of the present invention;

(14) FIG. 15 is a part cut-away view of the sandscreen section of FIG. 14;

(15) FIG. 16 is a sectional view of the sandscreen of FIG. 14;

(16) FIG. 17 is a sectional view of a sandscreen in accordance with an embodiment of the present invention;

(17) FIGS. 18a and 18b, and 19a and 19b, are views of a sandscreen having stacked inflatable elements, in accordance with an embodiment of the present invention;

(18) FIGS. 20a and 20b are sectional views of a sandscreen having multi-cell inflatable elements, in accordance with an embodiment of the present invention;

(19) FIGS. 21a and 21b are end view of sandscreens in accordance with an embodiment of the present invention;

(20) FIGS. 21c and 21d are sectional views of inflatable elements in accordance with embodiments of the present invention;

(21) FIG. 22 is a perspective view of part of a sandscreen made in accordance with an embodiment of the present invention;

(22) FIGS. 23 and 23a to 23e are part-sectional views of a valve for downhole apparatus in accordance with an embodiment of the present invention;

(23) FIGS. 23aa to 23ee are schematic illustrations of the relationship between the indexing profile and the follower pin of the apparatus of FIGS. 23a to 23e;

(24) FIGS. 24a to 24d are sectional view of a flow valve arrangement for downhole apparatus in accordance with an embodiment of the present invention;

(25) FIGS. 25a to 25c are sectional views of a bore lining arrangement in accordance with an embodiment of the present invention;

(26) FIGS. 26a to 26d are sectional view of a cementing arrangement in accordance with an embodiment of the present invention;

(27) FIG. 27 is a schematic illustration of a cementing arrangement in accordance with another embodiment of the invention; and

(28) FIGS. 28a and 28b of the drawings are schematic illustrations showing certain features of one of the inflatable elements of the arrangement of FIG. 27.

DETAILED DESCRIPTION OF THE DRAWINGS

(29) Reference is first made to FIG. 1 of the drawings, which is a schematic illustration of part of a well bore completion including three sand screens joints 10, in accordance with embodiments of the present invention. Features of such screens 10 may be utilised in combination with various aspects and embodiments of the present invention, as will be described. Of course the completion will include many other elements and devices not shown in the drawing, such as a shoe on the leading end of the completion, packers for zonal isolation, hangers, valves and the like, and some of these may form further aspects and embodiments of the invention.

(30) The screens 10 are run into the hole as part of a completion string and in a retracted or smaller diameter configuration and subsequently activated to assume a larger diameter configuration, in which the outer surface of the screens approaches and preferably engages the bore wall, whether this be formed by casing, liner, or an unlined bore section.

(31) FIG. 2 of the drawings illustrates a part cutaway view of part of one of the screens of FIG. 1, showing the screen 10 in an initial retracted configuration. The screen 10 comprises a rigid metal base pipe 12 providing mounting for six activation elements or chambers 14 which extend axially along the outer surface of the base pipe 12. The chambers 14 have metal walls and are arranged side-by-side around the base pipe 12 and may be inflated or deformed by filling the chambers 14 with high pressure fluid such that the chambers 14 assume an activated configuration, as illustrated in FIG. 3 of the drawings.

(32) A drainage/support layer 16 is located externally of the chambers 14, the layer 16 comprising six support strips 18 of aperture curved steel sheet. Like the chambers 14, the strips 18 are arranged side-by-side and extend axially along the screen 10, but are circumferentially offset relative to the chambers 14, as illustrated in the drawings, such that when the chambers 14 are extended the strips 18 bridge the gaps 20 formed between the chambers 14.

(33) The drainage layer 16 supports a filter media in the form of a weave 22. The weave 22 may comprise a single length of material wrapped around the drainage layer with the longitudinal edges overlapping, or may comprise two or more lengths of strips of material. A protective cylindrical shroud 24 is provided over the weave 22.

(34) The flow of inflation fluid into the chambers 14 is controlled by appropriate valve arrangements 30 (FIG. 1). A valve 30 is associated with each joint 10. The flow of production fluid from the surrounding formation may also be controlled by the valve 30.

(35) Reference is now also made to FIGS. 4a and 4b, which illustrate a sandscreen joint 110 in accordance with an embodiment of the present invention. It should be noted that the central section of the joint 110 as illustrated in FIGS. 4a and 4b is shown substantially shortened; the central section, over which the filter media 122 is exposed (through the screen shroud 124) represents more than 75% of the total length of the joint 110. FIG. 4a shows the screen 110 in an un-activated or retracted configuration (corresponding to the configuration illustrated in FIG. 2), whereas FIG. 4b shows the screen in an activated or extended configuration, (corresponding to FIG. 3).

(36) The sandscreen joint 110 is provided with threaded pin and box-type connections 132 at each end. One end of the joint 110 also includes the valve arrangement 130 for controlling the inflation of the activating elements provided in the joint, and also for controlling the flow of fluid from the surrounding formation, through the screen and into the base pipe 112. The valve arrangement may be similar to that described in GB2492193A, or may be one of the other valve arrangements as described herein. The general arrangement of activating elements, drainage layer, weave and shroud may be substantially as described above with reference to FIGS. 2 and 3, or alternatively or in addition may be in accordance with one of the various alternative arrangements described herein.

(37) In addition to allowing fluid to flow into the bore and then through the various elements of the sandscreen and into the base pipe 112, the sandscreen joint is also capable of providing zonal isolation. In particular, the ends of the portion of the joint 110 that are capable of extension on activation of the sandscreen 110, including the transition area 135, are coated with an elastomer sleeve 134. On activation of the sandscreen 110, the sleeve 134 is pushed out into contact with the bore wall and serves to isolate the zone on one side of the activated sleeve 134 from the zone on the other side of the sleeve 134. Thus, the provision of the sleeve 134 on the activated sandscreen prevents production fluid from flowing axially along the bore between the bore wall and sandscreen, and indeed axially through the portion of the sandscreen between the base pipe and the bore wall. This serves to protect the weave at the transition area 135, preventing axial flow through the transition area, which it has been found is the area where the weave tends to be weakest, and where the weave might otherwise be vulnerable to erosion damage.

(38) Flow into the sandscreen joint 110 from the surrounding formation may thus only take place through the fully extended portion of the screen, between the sleeves 134, where the sandscreen typically contacts and supports the bore wall. Flow through the weave will thus tend to be substantially radial, allowing the weave to operate at maximum efficiency.

(39) Where similar sandscreen joints 110 are coupled end-to-end, the sleeves 134 create isolated zones or annuli between the bore wall and the sections of the sandscreens which are not extended into contact with the bore wall. Thus, production fluid will not tend to flow from the surrounding formation and into these zones, minimising the risk of flow-induced collapse of the unsupported surrounding bore wall.

(40) The sleeve 134 may be positioned over the valve which controls flow of production fluid into the base pipe and thus may offer a degree of protection for the valve and assist in balancing flow from the formation, through the bore wall, and into the screen; the sleeve 134 prevents fluid from flowing radially and directly through the weave and into the valve; the fluid must flow axially along the screen before reaching the valve.

(41) To enhance the sealing capabilities of the elastomer sleeve 134, the outer surface of the sleeve defines circumferentially extending ridges or ribs 131. Surprisingly, it has been found that this improves the sealing effect achieved by the activated sleeves 134. It is believed that this is due to a coupling effect between adjacent ribs.

(42) Details of the sleeve 134 are shown in FIGS. 5 and 6 of the drawings, the detail of FIG. 6 illustrates the rounded form of the ribs 131. In this particular example, the ribs 131 and the associated troughs have been machined with a 5 mm radius in a sleeve 134 that is 10 mm thick.

(43) In use, a sandscreen joint 110 provided with elastomeric sleeves 134 may be provided in combination with screens which do not feature any sealing arrangement, the sandscreen joints 110 with sleeve 134 only being provided on completion where zonal isolation is desired.

(44) In the sandscreen joint 110 as described above zonal isolation is provided by mounting the elastomer sleeves 134 on the ends of the permeable screen section. However, if desired the screens and zonal isolation may be provided separately within a joint, or in separable joint sections, as illustrated in FIGS. 7 and 8. In FIGS. 7a and 7b, the illustrated sandscreen joint 110a has two screen sections 133a provided towards the end of the joint 110a, with a stand-alone zonal isolation barrier section 134a being provided in a central portion of the joint 110a. The screen sections 133a and the barrier section 134a may be activated under the control of a common inflation valve, or each section may be provided with a dedicated valve.

(45) FIG. 7c of the drawings illustrates a sectional view of the barrier section 134a which, in addition to the inflatable elements 114, features an inner and an outer elastomer sleeve 136a, 136b, which arrangement has been found to provide a more robust barrier than a single layer sleeve.

(46) In FIGS. 8a and 8b, a joint 110c comprising a single base pipe includes a single central screen section 133c and two separate zonal isolation barrier sections 134c towards the end of the joint 110c, activation of both the screen section and the barrier sections being controlled by a common inflation valve.

(47) The screen joints may be combined as desired in order to match the geology or profile of a particular well. The ability to combine a screen and a zonal isolation barrier in a single joint facilitates making up the completion string and also facilitates maximisation of inflow area when compared with conventional completion arrangements.

(48) Reference is now made to FIGS. 8, 9 and 10 of the drawings, which illustrate an area of a metal sheet 123 which may be used to form a shroud 124 for a sandscreen in accordance with an embodiment of the present invention. FIG. 9a illustrates the form of the sheet 123 as it would be used to form a shroud, such as the shroud 24 described above, including a multitude of initially closed openings in the form of staggered or overlapping axial slots 140. On activation of the sandscreen, the shroud and thus the sheet is circumferentially extended, such that the slots 140 open to the form illustrated in FIG. 9b.

(49) The slots 140 are initially formed in the sheet by punching, and the initial slot form 140a may be as illustrated in FIG. 10a, with the slot ends being enlarged to produce an open-ended form and avoid or minimise stress concentrations. However, following the punching of the slots, the sheet 123 is subject to a lateral compression force which causes the slots to close and assume the form 140b as illustrated in FIG. 10b. This is the form the slots take when the sheet is formed into a shroud. On activation of the sandscreen, the slots 140 are extended and assume the form 140c as illustrated in FIG. 10c.

(50) This slot form offers the operator numerous advantages. In the closed-up form 140b, the slots 140 restrict fluid access from the exterior of the screen to the screen interior. Thus, the weave and other filter elements of the sandscreen are isolated from the fluid in the well, which is likely to comprise drilling fluid carrying fine suspended solids which otherwise might plug or fill the weave. Also, if the shroud comes into contact with the bore wall as the completion string is being run into the well, any filter cake or the like on the well bore wall will be kept away from the weave. If the slots in the shroud were open, it is possible that filter cake and other material could be pushed and packed into the weave, limiting its permeability.

(51) The closed slots 140 also tend to produce a completion string which generates less friction when it contacts the bore wall, thus facilitating running in and increasing the likelihood of the completion being run to the target depth. The closed slots 140 are also far less likely to catch or hang-up on sharp or rough edges as might be present at milled casing windows or multi-lateral junctions.

(52) Reference is now made to FIGS. 11, 12 and 13 of the drawings which illustrate a further alternative sandscreen 210 in accordance with an embodiment of the present invention. This screen 210 shares many features with the screen 10 described with reference to FIGS. 2 and 3, however in this case the weave is provided in the form of six separate weave strips 222, each strip being mounted on a respective support strip 218, each of which defines flow apertures 219.

(53) The support strips 218 collectively form a support/drainage layer. The strips 218 are apertured and dimpled to permit fluid to flow through and under the strips 218, although the edges of each strip are free of openings and dimples to permit a seal to be formed between the edge and the underlying element.

(54) One edge of each support strip 218 is fixed and sealed to a respective activating element 214, for example by a bead of glue or a weld. The other edge sits over an adjacent activating element 214 and is free to move across the surface of the element 214 as the elements 214 are activated. However, the “free” edge of each support strip 218 remains substantially in sealing contract with the underlying activating element 214. Thus, fluid flowing from the surrounding formation through the shroud 224, through the weave 222, into the gaps 220 between the activated elements 214, and then into the base pipe 212, must pass through the weave 222 and also through the apertures 219 in the support strips 218.

(55) This arrangement offers substantial advantages when fabricating the screen joint 210. In particular, the support strips 218 and the associated weave strips 222 may be fabricated and then mounted on the elements 214 as unitary parts. This contrasts with typical conventional sandscreen assemblies, in which a single long (c10m) and flexible length of weave must be wrapped around a tubular assembly and secured in place using, for example, ties, clamps and spot welds. The advantages are particularly apparent in relation to weave materials with more challenging handling characteristics, for example reverse Dutch twill, which is relatively stiff and does not cope well with tension, as would be experienced by a conventionally wound weave on activation of the screen joint.

(56) Reference is also made to FIGS. 14, 15 and 16 of the drawings, which show a sandscreen joint 310 which is similar to the joint 210 described above, however in the sandscreen 310 the weave strip 322 associated with each support strip 318 is twice as wide as the associated support strip 318, and when the support strips 318 are mounted on the activating elements 314 the free edge of the associated weave strip 322 is positioned to over-lie the adjacent support strip 318, as is perhaps best illustrated in FIG. 16.

(57) On activation of the screen 310, the support strips 318 will separate, however the overlapping weave strips 322 ensure that any fluid passing from the formation into the base pipe 312 must pass through the weave 322, such that it is not necessary to seal the edges of the support strips 318 to the underlying activating elements 314.

(58) Reference is now made to FIG. 17 of the drawings, which illustrates a section of a sandscreen joint 410 in accordance with an embodiment of the present invention. The joint 410 may share features with the sandscreen 10 described above with reference to FIGS. 2 and 3 of the drawings, or with any of the other aspects or embodiments described herein. However, in this embodiment a short spigot or dowel 444 extends radially inwardly from the base of the mid-joint each activating element 414 to engage with the corresponding blind recess 446 formed in the outer wall of the base pipe 412. Of course dowels 444 could be provided at a plurality of locations on each element, and a typical joint (c.13 m long) may feature three axially-spaced dowels per element 414.

(59) The ends of the elements 414 may be retained as described in GB2492193A, or by any other appropriate means. However, by fixing three dowels 444 on the inner face of each activating element 414, the location of each element 414 relative to the base pipe 412 is maintained as the elements 414 are inflated. As noted above with reference to, for example, FIG. 3 of the drawings, as the activating elements 414 are inflated the gaps 420 between the elements 414 will increase. In certain circumstances it is possible that sections of the activating elements 414 would shift by moving circumferentially around the base pipe 412. This could have an impact on the form of the activated screen 410. For example, movement of the elements 414 could make it more difficult to achieve an activated screen having a circular cross section resulting in areas where the outer surface of the activated screen 410 was not in contact with the bore wall.

(60) FIGS. 18 and 19 of the drawings illustrate an alternative arrangement in which the location of activating elements 514 may be maintained relative to a base pipe 512. In FIGS. 18 and 19 only the base pipe 512 and activating elements 514 of a screen are illustrated. It will be noted that the base pipe 512 features axial scallops 546 which extend along the base pipe 512 centrally of the activating elements of 514. Thus, as the elements 514 are activated, a central inner wall portion of each element 514 extends into the respective scallop 546, as illustrated in FIGS. 19a and 19b, and therefore serves to maintain the axial positioning of the element 514 on the base pipe 512.

(61) It will also be noted from FIGS. 18 and 19 that each activating element 514 is formed of two radially stacked chambers or cells 514a, 514b. This facilitates provision of sandscreens or other arrangements capable of providing a high degree of expansion without requiring extensive deformation of the metal forming the elements 514.

(62) The individual cells or chambers of the activating elements 514 are formed of individual tubes which may be in fluid communication or may be inflated individually.

(63) An alternative form of activating element 614 is illustrated in FIG. 20, in which multiple cell activating elements 614 are formed by attaching a strip of metal to the base of a chamber and forming an aperture in the common wall, Of inflation of such an element 614, the lower cell 614a inflates and, as is apparent from FIG. 20b, provides for an enhanced degree of extension of the sandscreen 610.

(64) The arrangement of FIG. 20 offers the advantage of permitting provision of an element 614 with a relatively low initial profile, and thus an apparatus with a smaller inactivated diameter. Where two separate chambers or cells are provided, as illustrated in FIGS. 18 and 19, there is a minimum acceptable bend radius for the material, typically metal, forming the chamber walls, such that the minimum height of the edges of the retracted element is at least four times this minimum bend radius. However, the element 614 comprises only a single chamber 614b featuring the minimum bend radius, which need not be provided in connection with strip of material forming the lower cell.

(65) Reference is now made to FIGS. 21a and 21b of the drawings, which illustrate an alternative arrangement in which activating elements 714 are mounted on a base pipe 712 via smaller diameter stilts or spacers 748 which may also serve as control or electric lines. The stilts 748 space the activating element 714 from the outer surface of the base pipe 712 and thus provide a larger flow area between the base pipe 712 and the weave 722.

(66) In this embodiment it will be noted that each spacer comprises three circular cross-section pipes or tubes, the central tube being slightly larger and extending into a corresponding recess formed in the adjacent element wall. It will also be noted that the outer surface of the base pipe 712 between the elements 714 is provided with axially extending scallops or recesses 746 which further serve to increase the flow area between the base pipe 712 and weave 722, and which may also provide location for other items, in this case electronic gauges 750.

(67) FIGS. 21c and 21d are sectional views of inflatable elements 714a in accordance with embodiments of the present invention which may be utilised in various aspects of the invention. The elements 714a feature an inner and an outer cell 714b, 714c. The cells are inflatable, with the smaller inner cell 714b assuming a circular form to support a central portion of the larger outer cell 714c.

(68) Reference is now made to FIG. 22 of the drawings, which illustrates a valve section 812 as would be provided at an end section of a base pipe of a sandscreen in accordance with another embodiment of the present invention. This Figure illustrates the flow ports 852 that permit fluid to flow between the interior and the exterior of the valve section 812. An annular recess 854 is provided in the outer wall of the valve section 812 and accommodates a band of filter material 856. The filter material 856 will be of no finer gauge than the one that is provided on the screen and as such the filter material 856 will not normally provide any filtering function. However, in the event of damage or failure of the weave, the filter material 856 will prevent particulates from flowing into the flow port 852 and into the base pipe. Thus, a failure of the associated weave will not result in large volumes of particulate material flowing into the base pipe and creating problems for the operator.

(69) Reference is now made to FIGS. 23 and 23a to 23e of the drawings, which illustrate parts of a valve 930 for controlling the activation or inflation of elements 914 of a sandscreen in accordance with an embodiment of the present invention. As will be described, the valve configuration permits an operator to utilise relatively high fluid pressure to unlock the valve 930 and then utilise a lower pressure to inflate the associated activating elements 914.

(70) The valve 930 includes an indexing sleeve 960 that is axially moveable within a valve chamber 962 to control the flow of fluid between inflation ports 964 in the base pipe wall and inflation passages 966 leading to respective activating elements 914. The movement of the sleeve 960 is controlled by the interaction of a indexing profile 968 and follower pin 970 mounted on the valve body 972 (two slots 968 and respective pins 970 are provided at 180 degree spacings). The changing relationship between the slot 968 and pin 970 as the valve 930 is activated is illustrated in FIGS. 23aa to 23ee of the drawings.

(71) A compression spring 974 urges the indexing sleeve 960 in one axial direction while internal fluid pressure may act on a piston 976 to urge the sleeve 960 in the opposite direction.

(72) FIG. 23a illustrates the configuration of the valve when the sandscreen is being run in hole. It will be noted that the inflation ports 964 are isolated by the indexing sleeve 960 and appropriate seals 978. However, to provide for hydrostatic balance during running-in-hole (RIH) the inflation passages 966 are initially in fluid communication with the exterior of the sandscreen via a breather port 980 and sleeve passages 982. Furthermore, the sleeve 960 is initially locked in position by the piston 976, which is fixed in position relative to the valve body 972 by a releasable retainer, such as a shear ring or the illustrated shear pins 984.

(73) If it is desired to unlock the indexing sleeve 960, an elevated fluid pressure is applied to the interior of the string. This pressure is communicated, through actuating ports 986, to a chamber 988 on one side of the piston 976, and if the pressure is sufficient the pins 984 will shear and the piston 976 and sleeve 960 will move. However, only a limited movement of the piston 976 and sleeve 960 is possible, as the pin 970 is already located close to the end of the first leg of the indexing profile 968, as illustrated in FIGS. 23aa and 23bb, which correspond to FIGS. 23a and 23b.

(74) On bleeding off internal pressure, the spring 974 moves the indexing sleeve 960 in the opposite direction, the degree of movement being limited by the engagement between the indexing profile 968 and the pin 970 (see FIG. 23cc). This degree of movement is selected to place the sleeve passages 982 in fluid communication with the inflation ports 964, thus providing a passage for fluid to flow from the interior of the screen and into the activating elements 914. In this configuration the breather ports 980 are isolated from the sleeve passages 982.

(75) If the internal fluid pressure is then increased once more to inflate/activate the elements 914, the piston 976 is actuated to translate the sleeve 960 and compress the spring 974, however the movement of the sleeve 960 is constrained by the interaction of the indexing profile 968 and pin 970 (see FIG. 23dd) such that the inflation ports 964 remains in fluid communication with the sleeve passages 982 and the inflation passages 966, as illustrated in FIG. 23d.

(76) The inflation path to the elements 914 is provided with an appropriate oneway valve (not shown) to trap the inflation pressure within the activation elements 914, such that when pressure is bled off once more the inflation pressure is trapped within the elements 914. However, a further seal is created by the movement of the indexing sleeve 960 under the influence of the spring 974 such that the inflation ports 964 and the sleeve passages 982 are moved out of alignment. The indexing sleeve 960 is also moved to locate the pin 970 at the end of the indexing profile 968 (see FIG. 23ee), which allows the piston 976 to move to a fully balanced position, such that further internal pressure changes will not affect the piston 976. Thus, the sleeve 960 is effectively locked in position, permanently sealing off access to the elements 914.

(77) Furthermore, an additional pair of sprung-loaded pins 971 are mounted on the valve body 972 and, on the sleeve 960 reaching the final position, are arranged to snap into respective flat-bottomed holes formed in the indexing sleeve 960, ensuring that the sleeve is mechanically locked in the closed off position.

(78) Reference is now made to FIG. 24 of the drawings which illustrates a portion of a valve 931 for controlling flow of production fluid into the base pipe 912.

(79) FIG. 24a shows the valve 931 in the run-in-hole configuration in which inflow ports 990 are closed by an internal sleeve 991. The inflow ports 990 are formed in an external sleeve 992 which is initially fixed to the internal sleeve 991 by shear pins 993. In a somewhat similar manner to the inflation valve arrangement described above with reference to FIG. 23, on being exposed to an elevated released pressure (following inflation of the activating elements as described above), a piston 994 formed on the inner sleeve 991 is exposed to internal pressure which, if sufficient, will shear the pins 993, permitting a degree of movement between the sleeves 991, 992, as illustrated in FIG. 24b. Once pressure is bled off, a compression spring 999 between the inner and outer sleeves 991, 992 moves the inner sleeve 991 back in the opposite direction to align sleeve ports 995 in the inner sleeve 991 with the inflow ports 990 in the outer sleeve 992, as illustrated in FIG. 24c. Production fluid may thus now flow into the base pipe 912.

(80) Those of skill in the art will recognise that having the inflow ports 990 closed during run-in-hole, and in subsequent operations, offers numerous advantages. For example, if the inflow ports were always open, a completion incorporating screens otherwise made in accordance with this embodiment would tend to self-fill through the weave, increasing the risk of the weave becoming choked or plugged by material suspended in the fluid filling the bore.

(81) If at some point in the future it is desired to control or vary the flow of fluid through the inner flow ports 990, a mechanical shifting tool may be run into the bore to engage a profile 996 on a portion 991 a of the internal sleeve. If a sufficient force is applied to the profile 996, shear pins 997 will fail and permit axial movement of the internal sleeve portion 991a relative to the external sleeve 992, and move the open sleeve ports 995 out of alignment with the inflow ports 990, and place ports provided with inflow control devices 998 in registration with the inflow ports 990, as illustrated in FIG. 24d.

(82) Alternatively, in other embodiments, shifting the sleeve may shut off the inflow ports completely. Furthermore, a profile may be provided on the other end of the internal sleeve to allow a mechanical shifting tool to be run into the bore to move the sleeve in the opposite direction to re-open the ports. The different internal sleeve positions may be maintained by friction, or by providing a releasable retainer, such as a spring-loaded collet.

(83) In the above examples the various valves are described as being located towards one end of a screen or joint. However, in other embodiments valves may be provided at both ends of the screen or joint, centrally of the screen or joint, or indeed at any appropriate location on the screen or joint.

(84) Reference is now made to FIG. 25 of the drawings, which illustrates an arrangement for use in lining a bore. In section the apparatus 1010 has a generally similar appearance to the sandscreen 10 described above. However, the external elements of the apparatus 1010, namely the drainage layer 1016, the weave 1022 and the shroud 1024 are detachable from the base pipe 1012 and the actuating elements 1014. Thus, after the apparatus 1010 has been run into a bore and activated, as illustrated in FIG. 25b, the activating elements 1014 may be deflated and inactivated and the base pipe 1012 and activating elements 1014 removed from the bore, leaving a bore lining in place, as illustrated in FIG. 25c. Where the bore to be lined is not producing, the weave 1022 may be omitted.

(85) Reference is now made to FIG. 26 of the drawings, which illustrates apparatus suitable for use in a cementing operation, in particular for use in cementing an inner casing 1100 within an outer casing 1102. A sleeve 1104 is fixed, using shear pins, to the inner casing 1100 and in the initial fixed position the sleeve 1104 closes cement ports 1106 and inflation ports 1108 provided with one-way valves which communicate with annular inflatable elements 1110 mounted externally of the inner casing 1100. In the initial, unactivated configuration, the elements 1110 lie within recesses 1111 formed in the outer surface of the casing 1100 so as to present a substantially flush outer surface. The elements 1110 have metal walls provided with an outer elastomer covering.

(86) A previous cementing operation will have filled the annulus between the inner and outer casing 1100, 1102 to a level at or above the cement ports 1106.

(87) An opening dart or bomb 1112 is then pumped into the casing 1100, ahead of a volume of cleaning fluid. As illustrated in FIG. 26b, the dart 1112 lands on a profile 1114 in the lower end of the sleeve 1104. The fluid pressure acting downwards on the dart 1112, combined with the momentum of the following column of fluid, shears the pins retaining the sleeve 1104 relative to the casing 1100, such that the sleeve 1104 moves downwards, uncovering the cement ports 1106 and aligning the inflation ports 1108 with corresponding sleeve ports 1116, as illustrated in FIG. 26b. The cleaning fluid then inflates the elements 1110, the elements 1110 being configured to retain the inflated extended form, for example by provision of one-way valves in the ports 1108, or by forming the walls of the elements 1110 of a material which is plastically deformed and then retains the fluid pressure-induced deformation. Cleaning fluid is pumped into the casing 1100 and circulates through the open cement ports 1106 to circulate out any excess cement that has gathered above the element from the previous cementing operation.

(88) After the cleaning operation has been completed, a volume of cement slurry is pumped down through the casing 1100 and into the annulus through the ports 1106, above the activated elements 1110. The volume of cement may be followed by a dart which closes the cement ports 1106 and thus retains the column of cement slurry now in the annulus above the ports 1106.

(89) After completion of the cementing operation, the various plugs, the sleeve 1104 and any residual cement within the casing 1100 may be drilled out, as illustrated in FIG. 26d.

(90) Thus, this arrangement allows cement slurry to be flowed into an upper annulus, while the hydraulic head created by the cement slurry in the upper annulus is isolated from the cement slurry in the lower annulus by the inflated elements 1110. The inflated elements 1110 also provide a secondary barrier to prevent fluid flowing up the annulus from a lower formation.

(91) Reference is now made to FIG. 27 which illustrates a cementing arrangement in accordance with another embodiment of the present invention. The Figure illustrates apparatus suitable for use in cementing an inner casing 1200 within an outer casing 1202, with the lower end of the inner casing 1200 extending into an unlined bore section. A conventional shoe 1204 and a float collar 1206 are provided towards the leading end of the casing 1200, and an annular barrier 1208 is provided above the float collar 1206. The barrier 1208 has a tubular body 1210 for incorporation in the casing 1200 and carries three annular inflatable elements 1212 mounted externally of the body 1210. Fluid communication between the casing bore 1214 and the elements 1212 is provided via respective one-way valves 1214, initially closed by burst discs 1216.

(92) Reference is also now made to FIGS. 28a and 28b of the drawings, which are schematic illustrations showing certain features of one of the elements 1212. In particular, the element 1212 is constructed by welding a donut-shaped hollow metal chamber to a collar, which collar is then welded to the body 1210. As is evident from FIG. 28b, only the centre of the inner wall of the chamber is welded to the collar, such that the chamber wall is not restrained from deforming when the chamber is inflated.

(93) FIG. 27 illustrates the arrangement following a cementing operation, with the elements 1212 fully inflated and extending into the cement-filled annulus 1218. As with the apparatus described above with reference to FIG. 26, the inflated elements 1212 provide an additional seal between the casing 1200 and the bore wall 1220 and also assist in supporting the column of cement slurry 1222 as the cement sets.

(94) Initially, and during run-in, the elements 1212 are in a deflated retracted configuration, such that cement slurry that has been pumped down through the casing 1200 may pass through the float collar 1206 and the shoe 1204 and then into and up the annulus 1218. The cement slurry volume is followed into the casing 1200 by a solid wiper plug 1224, which ultimately lands on the collar 1206. The casing 1200 is then tested for pressure integrity. The burst discs 1216 are configured to fail at this test pressure, such that fluid in the casing bore will then inflate the elements 1212, and the arrangement will assume the configuration as illustrated in FIG. 27.

(95) Although only a single barrier 1208 providing a seal with an open hole section, one or more barriers could equally well be provided at other locations, and utilised to provide a casing-to-casing seal.