RESETTABLE DOWNHOLE PACKER

Abstract: A downhole packer (10) is provided for sealing an annulus between first tubing located within larger diameter second tubing. The packer comprises a mandrel (14) for coupling to the first tubing, the mandrel (14) having a wall defining a main through bore (16) and a plurality of smaller diameter through bores (16) for receiving control lines. The packer (10) is resettable, comprising a lost motion arrangement.

Description: RESETTABLE DOWNHOLE PACKER This invention relates to a downhole packer, and in particular but not exclusively to a packer intended for use in "intelligent" oil and gas wells, that is wells provided with downhole tools and devices located below the packer and which may be remotely controlled from surface. Oil and gas production wells typically comprise a casing-lined borehole, within which is located a string of smaller diameter production or "completion" tubing. The annulus between the casing and tubing is sealed by provision of one or more packers; a packer will normally be provided towards the lower end of the tubing and may be set to seal the annulus after the tubing has been run into the well . US Patent No 5,129,454, the disclosure of which is incorporated herein by reference, describes packers which provide the facility to pass up to two control lines through the packer to allow, for example, power cables to pass down through the packer to an electrical submersible pump (ESP) provided on the tubing below the packer, the ESP serving to boost production from relatively low pressure hydrocarbon-bearing formations. The control lines are accommodated in short string mandrels mounted to the main production fluid-carrying mandrel . The requirement to accommodate the various mandrels reduces the available flow area through the packer and thus reduces the flow rate from the well, and also complicates the sealing and mounting arrangements for the various packer components. The packers described in US Patent No 5,129,454 are also resettable, in that the packers may be hydraulically set, then mechanically unset, and subsequently reset and unset. This is made possible by the combination of a lost motion arrangement and various selectively shearable members: after the initial unsetting of the packer, a set of compression springs is released and the springs extend to locate the packer components in position ready to be hydraulically reset. Setting and resetting the packer requires shearing of various members, and the lost motion arrangement protects the screws which must be sheared to permit resetting. The resetting springs are accommodated in the space between the main and short string mandrels . UK Patent Application No 2,292,400, the disclosure of which is incorporated herein by reference, discloses a packer in which the packer mandrel defines both a main production fluid-carrying bore and an axial access line which allows passage of a 1/4" o.d. control line. To accommodate the line, and also to accommodate two fluid passageways which extend part-way along the mandrel, the mandrel is of eccentric form with its o.d. and i.d. offset J to provide a thickened wall portion. It is among the objectives of embodiments of the present invention to provide a downhole packer which accommodates a plurality of control lines with minimal reduction in the cross sectional area of the main through bore . It is a further objective of an embodiment of the invention to provide a resettable packer having a main through bore with a relatively large area through bore . According to a first embodiment of the present invention there is provided a downhole packer for sealing an annulus between first tubing located within larger diameter second tubing, the packer comprising: a mandrel for coupling to first tubing, the mandrel having a wall defining a main through bore and a plurality of smaller diameter through bores for receiving control lines; a seal arrangement located on the mandrel and being configurable to form an annular seal with a surrounding larger diameter second tubing; and a slip arrangement located on the mandrel and being configurable to engage a surrounding larger diameter second tubing . This aspect of the invention permits a plurality of control lines to pass through the mandrel wall, thus permitting control and communication with a plurality of tools, devices, sensors and the like located below the packer and as are found in "intelligent" wells. The packer may be provided in combination with control lines for communication with an electrical submersible pump (ESP), or other electrically powered tool or device. In this case, the control lines comprise power supply cables, and where the electrical supply is a three phase supply, the individual phases are carried by respective individual cables located in respective bores. This allows the bore diameters to be relatively small; in the arrangement as described in UK Patent Application No 2,292,400 it would not be possible to accommodate a conventional ESP power supply cable in the disclosed axial access line, and this would require the provision of a packer as described in US Patent No 5,129,454, that is a packer having separate fluid-carrying and control line-carrying mandrels. Of course the present invention may be utilised in other applications, in which the control lines are not restricted to electrical power cables, and may carry fluid conduits, signal carrying members, fibre optic cables and the like. Preferably, the mandrel is a unitary mandrel, that is the mandrel is formed from a single piece of material, typically steel or another appropriate metal alloy. Preferably, the smaller diameter bores are gun drilled through the mandrel wall, thus eliminating weak spots and potential leak paths that would be present if the mandrel was formed from multiple parts. Preferably also, the mandrel has an outside diameter and the main through bore has a inside diameter, said outside diameter and said inside diameter being offset to provide a relatively thick wall portion in which the smaller diameter through bores are formed. Preferably also, the smaller diameter through bores are circumferentially spaced about the main through bore. Preferably also, the packer is adapted to be hydraulically set, most preferably by bore pressure. The packer may comprise a setting arrangement including a setting piston which is axially movable in response to elevated pressure, and most preferably includes at least two linked setting pistons. The two or more setting pistons are preferably axially spaced, and thus may provide a relatively high setting force in response to a given setting pressure, without significantly increasing the diameter of the setting arrangement, and thus permitting provision of a relatively large area main through bore. Preferably also, the packer may be released from the set configuration, or unset, to release the seal arrangement and the slip arrangement from the set configuration, and allow retrieval or at least movement of the packer. Conveniently, this is achieved by means of a releasable coupling, typically a shear member, between a packer body mounted on the mandrel and comprising elements of the seal arrangement and the slip arrangement, and the mandrel . Preferably also, the packer is resettable, that is the packer is adapted to be set, unset and then reset without requiring retrieval to the surface. The packer preferably further comprises a lost motion arrangement, including means for biassing a packer body mounted on the mandrel and comprising elements of the seal arrangement and slip arrangement towards a configuration ready for resetting the seal and slip arrangements, following initial unsetting of the packer. The biassing means may comprise a spring, and most preferably a spring mounted concentrically on the mandrel . The use of a concentric spring allows the diameter of the main through bore to be maintained relatively large. Most preferably, the spring is initially restrained by a releasable coupling, which may also serve to retain the seal and slip arrangements in the set configuration . Preferably also, the packer may be released from the reset configuration, or unset, to release the seal arrangement and the slip arrangement from the reset configuration, and allow retrieval of the packer. Conveniently, this is achieved by means of a further releasable coupling, typically a further shear member, between the packer body and the mandrel. This and other aspects of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic half-sectioned view of a downhole packer in accordance with a preferred embodiment of the present invention; Figure 2 is a top view of the packer of Figure 1; Figures 3a to 3h are sectional views of the packer of Figure 1 in a run-in configuration; Figures 4a to 4h are sectional views of the packer of Figure 1 in a first set configuration; Figures 5a to 5h are sectional views of the packer of Figure 1 in a first unset configuration; Figures 6a to 6h are sectional views of the packer of Figure 1 in a second set configuration; Figures 7a to 7h are sectional views of the packer of Figure 1 in a second unset configuration; and Figures 8, 9 and 10 are top views of packers in accordance with other embodiments of the present invention. Reference is first made to Figures 1 and 2 of the drawings, Figure 1 being a schematic illustration of a downhole packer 10 in accordance with an embodiment of the present invention, and Figure 2 being an enlarged plan view of the packer 10. The packer 10 is intended to be utilised in "intelligent" well applications, and allows six control lines to pass through the packer 10 to facilitate control of tools and devices below the packer 10. In use, the packer 10 is mounted in a tubing string (not shown) and accordingly the packer includes top and bottom connectors 12, 13. Extending the length of the packer 10, between the connectors 12, 13, is a one-piece mandrel 14 which, as will be described, defines a main through bore 16, for carrying production fluids, and six smaller diameter secondary through bores 18, for accommodating control lines. Mounted externally of the mandrel 14 is a body 20 which includes resilient packer elements 22, slips 24 and the arrangement which permits setting and unsetting of the packer 10, as described below. Reference is now also made to Figures 3a to 3h, which illustrate the components of the packer 10 in greater detail. The Figures are arranged in sequence, with Figure 3a illustrating the upper end of the packer 10, through to Figure 3h illustrating the lower end of the packer 10, and the components of the packer 10 will, where possible, be introduced in sequence from the top of the packer 10 towards the bottom. As noted above, the packer mandrel 14 defines a main through bore 16 and six smaller diameter secondary through bores 18. The secondary through bores 18 are accommodated in a relatively thick portion of the packer wall 26, this being provided by offsetting the internal diameter of the main through bore 16 from the mandrel outside diameter 28. However, the thickened portion of the packer wall 26 does not extend to the ends of the mandrel 14, as is apparent from Figures 3b and 3g, to facilitate coupling of the control lines to the respective bores 18. The packer body 20 is mounted on the larger diameter section of the mandrel 14, the uppermost element of the body 20 being an upper gauge ring 30 which is pinned and threaded to the mandrel 14. The gauge ring 30 serves to restrain the upper end of the packer elements 22, the lower end of the elements 22 abutting the upper end of a setting sleeve 32 which is coupled to a pair of hydraulic setting pistons 34, 35 (Figures 3d and 3e) , as will be described. The setting sleeve 32 is restrained against downward movement relative to the mandrel 14 by a locking ring 36, but of course may be moved upwardly relative to the mandrel 14 to allow energising of the packer elements 22. The sleeve 32 is in two parts 32a, 32b, which are threaded together, the lowermost part 32b being threaded to a sleeve 38 forming part of the slip setting arrangement as will be described. The lower part of the sleeve 32b also abuts the upper end of a compression spring 40, the lower end of the spring abutting a sleeve 42 which is coupled to the setting pistons 34, 35 via a sleeve 44 forming a lower part of the slip setting arrangement. As noted above, the sleeve 44 of the slip setting arrangement is also coupled to the setting pistons 34, 35 and defines a cam face 46 for radially extending the slips 24. The sleeve 38 also defines a cam face 48 for acting on the upper end of the slips 24, the slips being contained within a cage 50 which is pinned to the sleeve 38. The slips 24 are provided with cone-shaped compression springs (not shown) which tend to urge the slips 24 towards the retracted position, thus facilitating unsetting of the packer 10 and in particular disengagement of the slips 24 from the surrounding casing. As noted above, two setting pistons 34, 35 are provided, these being formed by sleeves 52a, 52b, 52c which are threaded and pinned together and in sealed sliding contact with the mandrel outside diameter. The lower wall of the annular fluid chamber 54, 55 associated with each piston 34, 35 is formed by a respective seal ring 56, 57, each ring being restrained on the mandrel 14 by respective locking rings 58. Each fluid chamber 54, 55 is in communication with the main through bore 16 via a respective fluid port 62, 63. The pistons 34, 35 are initially fixed relative to the mandrel 14 by a shear screw 64 (Figure 3f) which couples the pistons 34, 35 to a lower body assembly 66, arranged to permit unsetting and resetting of the packer 10, as will be described. A secondary shear screw 65 also couples the pistons 34, 35 to the assembly 66, however in the packer run-in configuration, the shear screws 65 does not serve to restrain the pistons 34, 35, the screw head being located in an axial slot 67 in the piston sleeve 52c. As will be described, upward movement of the pistons 34, 35 relative to the assembly 66 is conserved by provision of a ratchet 68 arrangement comprising ratches 70 mounted on the sleeve 52c and a toothed outer face of a sleeve 72 forming the upper part of the assembly 66. The sleeve 72 is initially restrained relative to the mandrel 14 by a shear wire 74 (Figure 3f) . A secondary shear wire 75 is also provided and restrains a spring support 76 which abuts the upper end of a pre-loaded spring 78 which tends to bias the assembly 66 towards a lower relative position on the mandrel 14. However, as noted above, the assembly is initially restrained against such movement by the primary shear wire 74. Figures 3a to 3h illustrate the packer in its run-in configuration, that is with the packer elements 22 and the slips 24 retracted. The initial setting of the packer 10 will now be described, also with reference to Figures 4a to 4h, which illustrate the packer 10 in its first set configuration. Once the packer 10 has been positioned at the desired location in the well bore, the pressure within the main through bore 16 is increased. This increase in fluid pressure is communicated, via the ports 62, 63, to the pistons 34, 35. Once the fluid pressure exceeds a predetermined level, the primary shear screw 64 will fail, allowing the pistons 34, 35 to move upwardly relative to the mandrel 14. This movement is transmitted, via the spring 40, to the setting sleeve 32, and energises the packer elements 22, such that they are radially expanded to form a seal with a surrounding casing. Also, the piston movement is transmitted to the slip setting sleeve 44 which pushes the slips upwardly and outwardly. The movement of the pistons 34, 35 is conserved by the ratchet 68, such that on bleeding off bore pressure the packer 10 remains in the set configuration. If it becomes necessary to release or unset the packer 10, the string in which the packer 10 is mounted is pulled upwardly. Due to the engagement of slips 24 with the casing, the upper portion of the packer body 20 will tend to remain fixed relative to the casing, and if sufficient force is applied to the packer mandrel 14 from the upper portion of the string, the primary shear wire 74 will fail. The weight of the packer body 20, and also the action of the springs 40, 78 and any remaining pulling force, then move the packer element and slip setting parts of the packer body 20 to the position on the mandrel 14 as illustrated in Figures 5a to 5h of the drawings, causing the packer elements 22 and the slips 24 to retract. It will be noted that in this first unset configuration, the lower body assembly 66 moves to a lower position on the mandrel 14, however due to the ratchet 68 the upward portion of the packer body 20 assumes a similar position to when the packer was in the initial running configuration. When it is desired to set the packer 10 once more, elevated bore pressure will again tend to lift the pistons 34, 35 relative to the mandrel 14. Due to the changes in the relative positions of the pistons 34, 35 and the lower body assembly 66, the secondary shear screw 65 now occupies the lower end of the slot 67 in the sleeve 52c, such that movement of the pistons 34, 35 will only occur when the pressure has reached a level sufficient for the screw 65 to fail. Following failure of the screw 65, the packer elements 22 are energised and the slips 24 extended, as in the initial setting. As before, the ratchet 68 conserves the movement of the pistons 34, 35 relative to the lower body assembly 66, and the packer may assume the configuration as illustrated in Figures 6a to 6h of the drawings . In this second set configuration, the packer body 20 is restrained against axial movement relative to the mandrel 14 by the secondary shear wire 75. Accordingly, if axial force is applied to the packer 10 sufficient to shear the wire 75, the packer 10 will once more move to a set position, as illustrated in Figures 7a to 7h of the drawings. The packer body 20 is urged to assume this unset configuration by virtue of its own weight and by the action of the springs 40, 78, the body 20 being retained on the mandrel 14 by a lower retaining ring 80. Those of skill in the art will thus appreciate that the packer 10 may conveniently be set, released and reset in a bore, and ultimately released to allow retrieval of the packer 10. Reference is now made to Figure 8 of the drawings, which illustrates the top view of a packer 90 in accordance with another embodiment of the present invention. The illustrated packer 90 is operated in a similar manner to the packer 10 described above, and also defines similar internal and external diameters. However, rather than providing six similar diameter secondary through bores 18, the packer 90 provides five secondary through bores 92, comprising three through bores 92a for accommodating cables carrying a single phase of a three phase electrical supply to an electric submersible pump (ESP) located below the packer 90. The two remaining bores 92b may accommodate smaller diameter control lines . Reference is now made to Figure 9 of the drawings, which illustrates a packer 100 in accordance with a further embodiment of the present invention. The illustrated packer 100 is provided with a body 20 as described above, but comprises a conventional monobore mandrel 102, demonstrating that the body 20 may be used in applications in addition to those where communication is required through the packer for control and operation of ESPs and the like . Finally, reference is made to Figure 10 of the drawings, which illustrates a packer 110 in accordance with a still further embodiment of the present invention. The packer 110 is of greater internal and external diameter than the packers 10, 90, 100 described above, however the general structure and operation of the packer is substantially the same. The primary difference lies in the number and configuration of secondary through bores 112 provided in the packer mandrel 114, this larger diameter packer 110 accommodating seven secondary through bores 112, three capable of accommodating the cabling necessary to power a three-phase ESP, and a further four smaller diameter through bores being provided to accommodate other control lines. It will be event to those of skill in the art that the above described embodiments are merely exemplary of the present invention, and that various modifications and improvements may be made thereto without departing from the scope of the present invention.

Claims: CLAIMS 1. A resettable downhole packer for sealing an annulus between first tubing located within larger diameter second tubing, the packer comprising: a mandrel for coupling to first tubing, the mandrel having a wall defining a main through bore and a plurality of smaller diameter through bores for receiving control lines; a seal arrangement located on the mandrel and being configurable, in a set configuration, to form a seal with a surrounding larger diameter second tubing; and a slip arrangement located on the mandrel and being configurable, in a set configuration, to engage the surrounding larger diameter second tubing, the seal and slip arrangements being adapted to be reconfigured downhole from the set configuration to an unset configuration, and then further reconfigured downhole from the unset configuration to a reset configuration. 2. The packer of claim 1, in combination with a plurality of control lines, each control line extending through a respective smaller diameter through bore. 3. The packer of claim 2, in combination with control lines for communication with an electrically powered device, the control lines comprising power supply cables. 4. The packer of claim 3, in combination with power supply cables for carrying a three phase electrical supply, wherein the individual phases are carried by respective individual cables located in respective smaller diameter through bores. 5. The packer of any of the preceding claims, wherein at least the mandrel wall is formed from a single piece of material . 6. The packer of claim 5, wherein the smaller diameter bores are gun drilled through the mandrel wall. 7. The packer of any of the preceding claims, wherein the mandrel has an outside diameter and the main through bore has a inside diameter, said outside diameter and said inside diameter being offset to provide a relatively thick wall portion in which the smaller diameter through bores are formed. 8. The packer of any of the preceding claims, wherein the smaller diameter through bores are circumferentially spaced about the main through bore . 9. The packer of any of the preceding claims, wherein the packer is adapted to be hydraulically set. 10. The packer of any of the preceding claims, wherein the packer is adapted to be hydraulically set by application of bore pressure. 11. The packer of any of the preceding claims, further comprising a setting arrangement including a setting piston which is axially movable in response to elevated fluid pressure. 12. The packer of claim 11, wherein the setting piston is an annular piston located substantially concentrically about the mandrel . 13. The packer of claim 11 or 12, wherein the setting arrangement includes at least two operatively linked setting pistons. 14. The packer of claim 13, wherein the at least two setting pistons are axially spaced. 15. The packer of any of the preceding claims, wherein release of the seal arrangement and the ' slip arrangement from the set configuration results from release of a releasable coupling between a packer body mounted on the mandrel comprising elements of the seal arrangement and the slip arrangement, and the mandrel. 16. The packer of any of the preceding claims, further comprising a spring mounted concentrically on the mandrel, the spring being adapted to facilitate resetting of the seal and slip arrangements. 17. The packer of any of the preceding claims, further comprises a lost motion arrangement, including means for biassing a packer body, mounted on the mandrel and comprising elements of the seal arrangement and slip arrangement, towards a configuration ready for resetting the seal and slip arrangements, following release of the packer from an initial set position. 18. The packer of claim 17, wherein the biassing means comprises a spring. 19. The packer of claim 18, wherein the spring is mounted concentrically on the mandrel. 20. The packer of claim 18 or 19, wherein the spring is initially restrained by a releasable coupling. 21. The packer of claim 20, wherein the releasable coupling also serves to retain the seal and slip arrangements in the set configuration. 22. The packer of any of the preceding claims, wherein the packer is adapted to be released from the reset configuration, to release the seal arrangement and the slip arrangement from the reset configuration, and allow retrieval of the packer. 23. The packer of claim 20 or 21, wherein the packer is adapted to be released from the reset configuration, to release the seal arrangement and the slip arrangement from the reset configuration, and allow retrieval of the packer, release of the packer from the reset configuration resulting from the release of a further releasable coupling between the packer body and the mandrel . 24. A downhole packer for sealing an annulus between first tubing located within larger diameter second tubing, the packer comprising: a mandrel for coupling to first tubing, the mandrel having a wall defining a main through bore and a plurality of smaller diameter through bores; a seal arrangement located on the mandrel and being configurable, in a set configuration, to form a seal with a surrounding larger diameter second tubing; a slip arrangement located on the mandrel and being configurable, in a set configuration, to engage the surrounding larger diameter second tubing; and control lines for communication with an electrically powered downhole device below the packer, the control lines comprising power supply cables for carrying a three phase electrical supply, wherein the individual phases of the electrical supply are carried by three separate cables, each cable being located in a respective smaller diameter through bore in the mandrel wall. 25. A downhole packer for sealing an annulus between first tubing located within larger diameter second tubing, the packer comprising: a mandrel for coupling to first tubing, the mandrel having a wall defining a main through bore and a plurality of smaller diameter through bores; a seal arrangement located on the mandrel and being configurable, in a set configuration, to form a seal with a surrounding larger diameter second tubing; a slip arrangement located on the mandrel and being configurable, in a set configuration, to engage the surrounding larger diameter second tubing; and a setting arrangement including at least two operatively associated setting pistons which are axially movable in response to elevated fluid pressure. 26. The packer of claim 25, wherein the setting pistons are annular pistons located substantially concentrically about the mandrel.

Inventors: MILLAR DAVID MARTIN, VAN DORT ROLAND MARCEL, MILLAR, DAVID, MARTIN, VAN DORT, ROLAND, MARCEL
Applicants: DORT ROLAND MARCEL VAN, MILLAR DAVID MARTIN, WEATHERFORD LAMB, MILLAR, DAVID, MARTIN, VAN DORT, ROLAND, MARCEL, WEATHERFORD/LAMB, INC.
Application year: 2001
Main classification: E21B33
IPC codes: E21B33