AU2012201022B2 - Improved Plug - Google Patents

Improved Plug Download PDF

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Publication number
AU2012201022B2
AU2012201022B2 AU2012201022A AU2012201022A AU2012201022B2 AU 2012201022 B2 AU2012201022 B2 AU 2012201022B2 AU 2012201022 A AU2012201022 A AU 2012201022A AU 2012201022 A AU2012201022 A AU 2012201022A AU 2012201022 B2 AU2012201022 B2 AU 2012201022B2
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Australia
Prior art keywords
plug
seal element
body section
seal
conduit
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AU2012201022A
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AU2012201022A1 (en
Inventor
Daniel Purkis
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Weatherford Technology Holdings LLC
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Weatherford Technology Holdings LLC
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Priority claimed from AU2005298359A external-priority patent/AU2005298359B2/en
Application filed by Weatherford Technology Holdings LLC filed Critical Weatherford Technology Holdings LLC
Priority to AU2012201022A priority Critical patent/AU2012201022B2/en
Publication of AU2012201022A1 publication Critical patent/AU2012201022A1/en
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Publication of AU2012201022B2 publication Critical patent/AU2012201022B2/en
Assigned to WEATHERFORD TECHNOLOGY HOLDINGS, LLC reassignment WEATHERFORD TECHNOLOGY HOLDINGS, LLC Request for Assignment Assignors: PETROWELL LIMITED
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Abstract

Abstract A plug for sealing a conduit comprises a body having a first section (15) and a second section (17), and at least one seal element (20) for creating a seal between the plug and the conduit. The at least one seal element (20) is adapted to be energised by movement in a setting direction of the first body section (15) relative to the second body section (17). The pug further comprises seal locking means (26) comprising a first portion and a second portion wherein as the at last one seal (26) is energised, the seal locking means firsL portion is rutaLable unidirectioually relative to the seal locking means second portion to take up the movement of the first body section (15) relative to the second body section (17) in the setting direction and prevent movement of the first body section relative to the second body section in a releasing direction, opposite the setting direction. In one embodiment the seal locking means first portion is a locking nut. 3715026_1

Description

Regulation 3.2 AUSTRALIA PATENTS ACT, 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT ORIGINAL Name of Applicant: PETROWELL LIMITED Actual Inventors: PURKIS, Daniel Address for service in A J PARK, Level 11, 60 Marcus Clarke Street, Canberra ACT Australia: 2601, Australia Invention Title: Improved Plug The following statement is a full description of this invention, including the best method of performing it known to us. 312339111 2 IMPROVED PLUG FIELD OF THE INVENTION The present invention relates to plugs, particularly to plugs for sealing 5 wellbores and christmas trees. BACKGROUND OF THE INVENTION Conventionally wellbores, and christmas trees associated with wellbores, have been sealed with plugs having three basic parts: an anchoring system, a sealing 10 element and a setting system. The first stage in setting a conventional plug is anchoring the plug in the wellbore. Anchoring systems for conventional wellhead plugs use a set of locking dogs, which engage a recessed profile in the wellbore or tree, or use a set of slips which "bite" the casing to hold the plug in place. 15 The seal is then set using a linear action setting mechanism to create a linear displacement to deform the seal element. The force required to create the seal is then locked in using a linear locking mechanism. In wellbore applications the seal is generally a metal-to-metal seal formed by swaging a metal ring element into the bore or onto a no-go shoulder. 20 To provide a seal capable of withstanding well pressures, the required setting force needs to be as high as the maximum force generated by the well pressure. In recent years a number of high pressure, high temperature, high flow rate wells have been completed which have highlighted shortcomings in conventional designs of well bore plugs and tree plugs. For example, swaged seals can dislodge 25 when exposed to the high pressure, temperature and vibration cycles of these wells, and the jarring action used to set the seal can damage the plug or the surrounding environment. Additionally, linear locking mechanisms have a degree of backlash which in a high temperature, pressure and vibration cycle environment can lead to failure. 30 A further disadvantage of conventional plugs is the expansion achievable from the metal seal element is not sufficient to permit the plug to be run into the wellbore with adequate clearance between the plug and the wellbore to prevent a build-up of pressure in front of the plug, resisting the placement of the plug. This can be a 3823017-1 3 particular problem when a number of plugs are to be located in series in a conduit, as a hydraulic lock can be formed between plugs. It is an object of the present invention to obviate or mitigate at least one of the aforementioned disadvantages. 5 SUMMARY OF THE INVENTION According to a first aspect of the present invention there is provided a plug for sealing a conduit, the plug comprising: a first body section; 10 a second body section having an energising portion and a de-energising portion; and at least one seal element for creating a seal between the plug and a conduit, the at least one seal element being energised and de-energised by movement of the first body section relative to the second body section; 15 such that to energise the seal, the energising portion of the second body section is engaged with the at least one seal element and to de-energise the seal the de-energising portion of the second body section is engaged with the at least one seal element, the de-energising portion defining a fluid flow path around the at least one seal element. 20 Provision of a de-energising portion permits, when the plug is sealed in a conduit, pressure equalisation across the seal element, which prevents the possibility of the plug being blown tip the conduit by pressure trapped below the plug. Preferably, the at least one seal element is adapted to be energised by axially translating the first body section relative to the second body section in the setting 25 direction. Preferably, the plug is adapted to be set by the application of linear forces to one or both of the first body section and the second body section to axially translate the first body section relative to the second body section in the setting direction. Alternatively, the at least one seal element is adapted to be energised by 30 rotationally translating the first body section relative to the second body section in the setting direction. Preferably, the at least one seal element is a metal seal element. Preferably, the at least one seal element is a stack of frusto-conical washers. Frusto-conical washers are also known as disc springs or Belleville WashersTM 3823017-1 4 Alternatively, the at least one seal element is a plurality of metal seals, or a combination of metal and plastic seals. Preferably, at least one frusto-conical washer in the stack is adapted to form an independent metal-to-metal seal with a conduit from at least one other frusto-conical 5 washer in the stack. Preferably, the frusto-conical washers are steel. Most preferably, the frusto conical washers are InconelTM. Preferably, the frusto-conical washers are coated with silver. Most preferably, the silver coating is approximately 3 5pm thick. 10 Preferably, adjacent washers or seals are separated by at least one layer of softer material. Preferably, the softer material is polymeric. Preferably, the at least one layer is a laminate of softer material. Most preferably, the at least one layer is a laminate of a number of softer materials. In one 15 embodiment the laminate is a layer of PTFE sandwiched between layers of PEEK. In a further alternative, the at least one seal element may be multiple metal seals of differing hardness. Preferably, the at least one seal element is energised by compression. Preferably, where the at least one seal element is a stack of frusto-conical 20 washers, in the uncompressed state each washer is at an angle of 80 to the horizontal. Preferably, where the at least one seal element is a stack of frusto-conical washers, when the at least one seal element is energised, the washers are not flattened. Most preferably, in the energised configuration, each frusto-conical washer is at an angle of 50 to the horizontal. Retaining a slight angle, assists in the recovery of the 25 frusto-conical washers to their original shape when the seal is released. A metal seal element is required for use in wellbores. A stack of frusto conical washers is preferred because a high expansion ratio is achievable by compression of a frusto-conical washer, permitting the plug to be run into position without building up a significant head of pressure in front of the plug. A further 30 advantage of the frusto conical washer is the expansion is an elastic expansion; the plug can be easily removed from the conduit by releasing the compression force on the washers, thereby reversing the expansion of the seal element sufficiently to permit removal of the plug from the conduit. Additionally because the stack of frusto conical washers is a smaller diameter than the target seal prior to and after sealing 3823017-1 5 there is no requirement for jarring and no damage is done to the seal bore in the conduit. As no jarring is required to set the seal, the plug can be set by a running adapter which uses e-line or slick-line. The use of a softer material between adjacent washers allows a tight seal to be 5 obtained in a damaged conduit. As the stack is compressed the softer material is squeezed radially outwards into engagement with the damaged conduit. Preferably, in an uncompressed configuration, the stack of frusto-conical washers describes an external diameter less than that of the plug body. This arrangement means the plug can be run in without the seal element being damaged on 10 the conduit. Preferably, to release the at least one seal element, the second body section is moveable relative to the at least one seal element. Preferably, the second body section is moveable from a set position to a released position, such that in the set position, a seal is formed between the at least 15 one seal element and the second body section and in the released position there is a flow path between the at least one seal element and the second body section. Preferably, the flow path is provided by at least one groove defined by the second body section. Preferably, the plug further comprises a flow path locking means to lock the 20 plug in the released position. This arrangement prevents the seal element being inadvertently reset after an operator believes the seal element has been released. According to a second aspect of the present invention there is provided a method of retrieving a plug from a conduit which extends downhole, the method comprising the steps of: 25 de-energising at least one seal element, the at least one seal element forming a seal between the plug and a conduit, by movement of a first body section relative to a second body section to a position in which a de-energising portion of the second body section is engaged with the at least one seal element, the de-energising portion defining a fluid flow path around the at least one seal element. 30 BRIEF DESCRIPTION OF THE DRAWINGS The present invention will now be described, by way of example, with reference to the accompanying figures in which: 3823017-1 6 Figure 1 is a cut away side view of a plug, for sealing a conduit, and a running adapter for setting the plug in the conduit in accordance with a first embodiment of the present invention; Figure 2 is an enlarged cut away side view of section A of Figure 1, showing 5 the plug and part of the running adapter; Figure 3 is an enlarged cut away side view of section B of Figure 1, showing part of the running adapter; Figure 4 is an enlarged cut away side view of section C of Figure 1, showing part of the running adapter; 10 Figure 5 is a cut away side view of the plug of Figure 1 in a conduit prior to the anchoring dogs being set; Figure 6 is a cut away side view of the plug of Figure 1 in the conduit after the anchoring dogs have been set and prior to the seal element being set; Figure 7 is a cut away side view of the plug of Figure 1 in the conduit after the 15 anchoring dogs and the seal element have been set; Figure 8 is a cut away side view of the plug ofFigure 1 in the conduit showing the retaining sleeve disengaged from the locking nut; Figure 9 is a cut away side view of the plug of Figure 1 in the conduit showing the seal element released; 20 Figure 10 is a cut away side view of the plug of Figure 1 in the conduit showing the anchoring dogs released; Figure 11 is a perspective view of a locking nut; Figure 12 is a view along section A-A of Figure 2 through part of the locking nut; 25 Figure 13 is a perspective view of one of the first conical washers of the seal element; Figure 14 is a schematic cut away side view of part of a stack of frusto-conical washers in an uncompressed configuration; Figure 15 is a schematic cut away side view of part of a stack of frusto-conical 30 washers in an compressed configuration; Figure 16 is a perspective view of part of the plug mandrel; Figure 17 is a perspective view of a plug for sealing a conduit in accordance with a second embodiment of the present invention; 3B23017-1 7 Figure 18 is a sectional view of the plug of Figure I taken through line A-A on Figure 17; Figure 19 is a sectional view taken through line B-B on Figure 18; Figure 20a is a perspective view of the first rotary lock ring of Figure 18; S Figure 20b is a plan view of the second rotary lock ring of Figure 18; Figure 21 is a perspective view of a plug running adapter for setting a plug in a conduit in accordance with a second embodiment of the present invention; Figure 22 is a sectional view taken through line C-C on Figure 21; and Figure 23, comprising Figures 23a to 23d is a schematic of the plug of Figure 10 17 being set in a wellbore. DETAILED DESCRIPTION OF THE DRAWINGS Referring firstly to Figure 1 there is shown a cut away side view of a plug, generally indicated by reference numeral 10 for sealing a conduit (not shown), and a 15 running adapter 12 for setting the plug 10 in the conduit. As can be seen from Figure 1 the plug and running adapter 10,12 had been divided into three sections indicated as "A", "B", and "C", each of these sections is shown in Figures 2, 3 and 4 respectively. Referring to Figure 2, an enlarged cut away side view of section A of Figure 1, 20 showing the plug 10 and part of the running adapter 12. The plug 10 includes a housing 14, divided in to a moveable upper housing section 15 and a fixed lower housing section 17. The plug 10 also includes a seal setting means 16 in the form of a plug mandrel 18 and a seal element 20 in the form of a stack of frusto-conical washers 22. 25 The plug 10 includes eight anchoring dogs 34 for anchoring the plug 10 in the conduit (not shown). The dogs 34 are axially restrained by the lower housing section 17 but are permitted to move radially outwards from the housing 14 through a series of openings 36. The dogs 34 are moved radially outwards through the apertures 36 by the 30 upper housing section 15, specifically, by the action of a housing ramp 54. The plug 10 further comprises a seal and anchor locking means 24 comprising a locking nut 26, a spacer sleeve 28, and a retaining sleeve 30. The retaining sleeve 30 is releasably fixed to the locking nut 26 by means of a number of sheer screws 32, of which one is indicated. The locking nut 26 is attached to the plug mandrel 18 by a 3823017-1 8 threaded connection 27, and the spacer sleeve acts on the housing upper portion 14, specifically the housing ramp 54. It will be understood that the spacer sleeve 28 could be part of the housing 14. The seal and anchor locking means 24 permits movement of the housing upper 5 portion 15 relative to the mandrel 18 in a setting direction, that is a direction which the seal element 20 is energised, but not in a releasing direction, opposite the setting direction. Referring to Figures 3 and 4, enlarged cut away side views of sections B and C of Figure 1 showing the running adapter 12, the adapter 12 is arranged, in use with the 10 plug 10, to convert a rotary input force applied to an input mandrel 80 into a rotary and an axial output force for application to the plug 10. The rotary output force is applied to the locking nut 26 by a locking sleeve 82, and the axial output force is applied to the upper housing section 15 by a running adapter casing 86, and to the plug mandrel 18 by an output mandrel 84. 15 The setting of the plug 10, by the plug and the running adapter 12 will now be described with reference to Figures 1 to 4, and Figures 5 to 7. Figure 5 to 7 are cut away views of the plug 10 being set in a conduit 90. For clarity, the running adapter 12 is not shown in any of Figures 5 to 7. The plug and adapter 10,12 are lowered into the conduit 90, in this case the 20 bore of a christmas tree. As can be seen from Figure 5, the stack of washers 22 is arranged so that the washers 22 do not extend beyond the circumference housing lower section 17. This permits the plug 10 to be run in to the conduit 90 without damaging the seal element 20. The plug 10 is run into the conduit 90 until a housing shoulder 92 engages a 25 conduit no-go 94, indicating the plug 10 has reached the correct location. At this point the adapter 12 can be activated and the plug 10 can be set. A rotary force is applied to the running adapter input mandrel 80 by an external drive (not shown). The running adapter input mandrel 80 engages the running adapter casing 86 by means of a threaded connection 96. The threaded 30 connection 96 has a pitch of 0.2 inches (0.508 mm). The running adapter casing 86 is locked to a motorised setting tool (not shown) connected to the running adapter 12, preventing the casing 86 from rotating with the input mandrel 80. However linear axial movement of the running adapter casing 86 is permitted. The threaded connection 96 is arranged such that rotational 3823017-1 9 movement of the input mandrel 80, in the absence of a resistance, would result in the input mandrel 80 moving the direction of arrow "X" (Figure 4), applying a pulling force on the output mandrel 80, and the casing moving in the direction of arrow "Y", that is pushing on the upper housing section 15. 5 There is however a resistance preventing the input mandrel 80 moving in the direction is arrow "X". The input mandrel 80 is connected to a collar 98 (Figure 3), which is in turn connected to the output mandrel 84 via a number of shear screws 100. A pair of roller bearings 102 permit the input mandrel 80 to rotate within the collar 98 whilst still transmitting axial pulling forces, applied by the input mandrel 80, to the 10 output mandrel 84. The output mandrel 84 is in turn connected to the plug mandrel 18 by means of a collet 104 (Figure 2). The pulling force applied to the plug mandrel 18 by the input mandrel 80, via the collar 98 and the output mandrel 84 is resisted by a set of shear set screws 106. The resistance of the shear set screws 106 prevents the input mandrel moving 15 in the direction of arrow "X" and therefore the running adapter casing 86 moves in the direction of arrow "Y" and applies an axial "pushing" force on the upper housing section 15. Referring to Figure 5, a cut away side view of a plug 10 in a conduit 90 prior to the dogs 34 being set, under the action of this force, the upper housing section 15 20 and the housing ramp 54 move in the direction of arrow "Y", the ramp 54 engaging the dogs 34 and pushing them radially outwards through the housing apertures 36. The dogs 34 move towards engagement with a complementary recess 108 in the conduit wall 110. The ramp 54 defines a variable surface taper 55 having two sections 57 of shallow taper and two sections 59 of steep taper. The steep taper 25 sections 59 are arranged to move the dogs 34 rapidly towards the conduit recess 108, with the shallow taper sections 57 pushing the dogs 34 for the final stage of their travel into the recess 108 and into engagement with the conduit wall 110. A shallow taper for the stage of the travel in which actual engagement occurs is preferred because a shallow taper maximises the radial force applied to the dogs 34 and assists 30 in locking the plug 10 in the conduit 90. Utilising the steep taper sections 59 for the initial expansion of the travel reduces the axial length of the ramp 54. The movement of the upper housing section 15 relative to the plug mandrel 18 is taken up by the locking nut 26, which engages the plug mandrel 18 by means of the threaded connection 27. As the upper housing section 15 moves relative to the plug 382301-7-1 10 mandrel 18, the locking nut 26 is rotated by the running adapter locking sleeve 82 relative to the spacer sleeve 28. This rotation is unidirectional preventing relative movement of the mandrel 18 with respect to the upper housing section 15 in the opposite direction, which, if permitted, would release the seal element 20. 5 The locking sleeve 82 is connected to the input mandrel 80 by a clutch 112 (Figure 4). As the input mandrel 80 rotates the locking sleeve 82 rotates, however if the locking sleeve 82 encounters sufficient resistance, the clutch 112 slips and the rotation of the locking sleeve 82 stops. The pitch of the threaded connection 27 between the locking nut 26 and the plug mandrel 18 is 0.25 inches (6.35 mm), 10 compared to the pitch of the threaded connection between the input mandrel 80 and the adapter casing 86 of 0.2 inches (5.08 nun). This difference in the two pitches means that for every revolution of the input mandrel 18, the adapter casing 86, and hence the upper housing section, will move 0.2 inches (5.08 mm), and the locking nut will move 0.25 inches (6.35 mm). However as the locking nut 26 is acts on upper 15 housing section 15 via the spacer sleeve 28, the full movement of the locking nut 26 per revolution of the input mandrel 18 is not permitted and sufficient resistance is generated on the locking sleeve 82 to slip the clutch 112. The locking sleeve 82, however, applies a continual rotational force to the locking nut 26 and as soon as there is further movement of the upper housing section 20 15 relative to the plug mandrel 18, the locking nut 26 will take up this movement. Referring now to Figure 11, a perspective view of the locking nut 26, it can be seen the locking nut comprises a first locking nut portion 56 and a second locking nut portion 58. The first locking nut portion 56 comprises six axial sections 60, each axial section 60 being attached to the second locking nut portion 58 by means of a 25 dovetail connection 62. The internal surfaces 61 of the six axial sections 60, when assembled, define one half of the threaded connection 27. The dovetail connections 62 permit the axial sections 60 to move in a radial direction relative to the second locking nut portion 58 but not in an axial direction. When the seal locking means 24 is assembled the axial sections 60 are 30 prevented from moving radially outwards by the retaining sleeve 30. The locking nut 26 also includes unidirectional locking device 64. The arrangement of each locking device 64 can be seen more clearly in Figure 12, a view along section A-A of Figure 2. Each locking device 64 comprises a ball bearing 66 located in a channel 68 having an internal surface 74. The ball bearing 66 is mounted 3823017-1 11 on a spring 70 which pushes against the ball bearing 66, forcing the ball bearing 66 out of the channel 68. As the locking nut 26 rotates with respect to the spacer sleeve 28, the ball bearing 66 is pressed against the spacer sleeve surface 72. If the locking nut 26 is 5 moving relative to the spacer sleeve 28 in the direction of arrow "A", the ball bearing is pushed back up the channel 68, however if a force is applied to the locking nut 26 in the direction of arrow "B", then the ball bearing 66 is drawn out of the channel 68 and wedges between the sleeve surface 72 and the channel surface 74, preventing further movement in the direction of arrow "B". As the interface between the locking 10 nut 26 and the spacer sleeve 28 is located on an are centred on, and substantially perpendicular to, the longitudinal axis of the adapter, backlash is minimised. For example if the locking nut moved 1/20 of a revolution in the direction of arrow "B", this would result in axial movement in the release direction of (0.25 x 1/20) inches, that is 0.0125 inches (0.318 mm). The motorised setting tool (not shown) records 15 the torque versus turn profile of the locking nut 26. This information is transmitted live by e-line (not shown) from the adapter 12 and compared with the expected profile in order to confirm proper setting of the plug. Referring now to Figure 6, a cut away side view of the plug 10 in the conduit 90 after the anchoring dogs 34 have been set and prior to the seal element 20 being 20 set, the dogs 34 have engaged the recess 108, particularly, a first dog surface region 112 has engaged a first recess surface region 114. This arrangement imparts a downward force on the plug 10 which is resisted by the interaction between the plug shoulder 92 and the conduit no-go 94, with the result that the plug 10 is firmly locked in the conduit 90. With the dogs 34 fully set, the upper housing section 15 can not 25 move any further in the direction of arrow "Y". Once the plug 10 is firmly locked in position, the seal element 20 can be set. This is achieved by increasing the rotary force on the input mandrel 80. Referring to Figure 7, a cut away side view of the plug 10 in the conduit 90 after the anchoring dogs and the seal element 20 have been set, the force is increased 30 on the input mandrel 80 until the shear screws 106 shear, permitting the input mandrel 80, and hence the plug mandrel 18, to move in the direction of arrow "X". The seal element 20 is located in a seal recess 116 defined by the plug mandrel 18 and the lower housing section 17. As the plug mandrel 18 moves upwards, that is 3823017-1 12 in the direction of arrow "X", the seal recess 116 reduces in size, compressing the seal element 20 into engagement with the conduit 90. The movement of the plug mandrel 18 relative to the housing 14 is taken up by the locking nut 26, which is driven by the running adapter locking sleeve 82, in the 5 same way as described previously. As discussed earlier, the seal element 20 is a stack of frusto-conical washers 22. Referring to Figure 13 there is shown a perspective view of one of the first conical washers 22. Each frusto-conical washer 22 is made from Inconel steel and coated in a layer of silver 35 microns thick. The washer inner edge 44 defines an 10 aperture through which the plug mandrel 18 passes and when the seal is set this inner edge 44 is adapted to sealingly engage the mandrel 18. The outer washer edge 46, when the seal element 20 is energised, is adapted to fbrm a seal with a conduit, each washer 22 in the stack forming an independent seal from every other washer 22. As can be seen from Figure 14, a schematic cut away side view of part of a 15 stack of frusto-conical washers 22 in an uncompressed configuration, between each washer 22 there is a laminate of softer material 48. This laminate 48 is made up of a central layer 50 of PEEK sandwiched between two layers 52 of PTFE. As the stack of washers 22 is energised, by being compressed by relative movement between the housing 14 and the plug mandrel 18, the laminate 48 is squeezed radially inwards, 20 forming a seal with the plug mandrel 18, and radially outwards, forming a seal with the conduit 90. Figure 15 shows a schematic cut away side view of part of a stack of frusto-conical washers 22 in a compressed, or set, configuration As can be seen from Figure 15 the laminate of softer material 48 is squeezed beyond the edges of the washers 22, and assists in forming a seal if the conduit 90 is 25 not entirely smooth; the softer material spreading into any voids or inconsistencies in the surface of the conduit 90. It will be noted from Figure 15 that even when fully compressed each washer 22 is not completely flattened. In the uncompressed state the angle of each washer to the horizontal, indicated as angle 0 on Figures 14 and 15, is 8* to the horizontal. In 30 the compressed, or set, configuration angle 0 is 5'. The retention of a slight angle to the horizontal assists the seal element in recovering back to the uncompressed configuration when the compression force is removed. Referring back to Figure 7, in the leading end 38 of the plug 10 is a reservoir 40. The reservoir 40 is sealed from the surrounding environment and contains a body 3823017-1 13 of air at a pressure of 1 bar. A reservoir cap 42 is provided which seals the reservoir 40 and is adapted to rupture at a given threshold pressure. The purpose of the reservoir 40 is to reduce pressure on the seal element 20 in the event that a volume of air becomes trapped and pressurised below the plug 10. A volume of air may get 5 trapped if, for example, it is decided to set two plugs 10 in series. Without the reservoir 40, the increased pressure would apply a force on the plug 10 which may affect the integrity of the seal element 20. With the reservoir 40, before any damage can be done to the integrity of the seal, the cap 42 ruptures, with the effect of reducing the overall pressure of the air trapped below the plug 10. 10 Figures 5 to 7 explained the setting of the plug 10 in the conduit 90, the releasing and retrieval of the plug will now be described with reference to Figures 1 to 4 and Figures 8 to 10. The releasing and retrieval of the plug 10 is achieved using conventional wireline techniques The plug 10 is prevented from being removed from the conduit 90 by the 15 locking means 24, particularly because the plug mandrel 18 can not move in the release direction relative to the housing 14. As previously discussed the locking nut 26 comprises a first portion 56 and a second portion 58, the first portion 56 comprising six radially moveable sections 60, which together define one half of the threaded connection 27 between the locking nut 26 and the plug mandrel 18. The 20 retaining sleeve 30 prevents radial movement of the locking nut sections 26. Referring to Figure 8, a cut away side view of the plug 10 in the conduit 90 showing the retaining sleeve 30 disengaged from the locking nut 26, sufficient force has been applied to the retaining sleeve 30 by a wireline controlled releasing tool (not shown) to overcome the shear screws 32 so the shear screws 32 are no longer securing 25 the retaining sleeve 30 to the locking nut 26, permitting the six moveable sections 60 to move radially outwardly and break the threaded connection 27 between the locking nut 26 and the plug mandrel 18. As the plug mandrel 18 is no longer locked relative to the housing 14, the wireline controlled releasing tool can apply a fbrce to the plug mandrel 18 to move 30 the plug mandrel 18 in the release direction, that is in the direction of arrow "R" on Figure 8. As the plug mandrel 18 moves in the direction of arrow "R", the compression force on the seal element 20 is removed and the seals are permitted to spring back to the uncompressed configuration, releasing the pressure below the seal element 20. 3823017-1 14 Referring to Figure 9, a cut away side view of the plug 10 in the conduit 90 showing the seal element 20 released, the plug mandrel 18 includes a grooved section 120 describing a number of grooves 122. The grooves 122 can be seen more clearly on Figure 16, a perspective view of part of the plug mandrel 18. When the seal 5 element 20 is set, the inner edge 44 of each washer 22 engages a non-grooved section 124 of the plug mandrel 18, however as the plug mandrel 18 moves in the release direction the grooved section 122 is translates behind the seal element 20, and a pressure equalising flow path is created around the seal element 20. To ensure the seal element 20 does not re-set, the plug mandrel 18 is also 10 provided with a wickered surface 126 (Figures 9 and 16) which engages with a complementary wickered element 128 (Figure 9), which is secured to the lower housing section 17 by a screw 130. The engagement between the wickered surface 126 and the wickered element 128 is arranged to permit only uni-directional movement, thereby preventing the plug mandrel 18 moving and resetting the seal 15 element 20. The plug mandrel 18 is moved in the direction arrow "R" -until the plug mandrel lug 132 engages the wickered element 128, preventing further movement of the plug mandrel 18. With the seal between the plug 10 and the conduit 90 broken, the plug 10 can be safely removed from the conduit 90, because the seal element 20 has been de 20 energised and pressure equalisation has occurred across the seal element 20. The pressure equalisation prevents the possibility of the plug being blown up the conduit 90 by pressure trapped below the plug 10. The wireline releasing tool is recovered to surface and a wireline pulling tool (not shown) is sent down to the plug 10 to engage the plug housing 14. 25 Referring to Figure 10, a cut away side view of the plug 10 in the conduit 90 showing the anchoring dogs 34 released. As the input mandrel 18 can not now move relative to the housing 14, the upper housing section 15 moves in the direction of arrow "S" under the action of the wireline pulling tool. The housing ramp 54 moves away from the dogs 34 permitting the dogs 34 to retract into the housing 14 through 30 the housing apertures 36. The plug 10 is now released from the conduit 90 and can be recovered to surface by the wireline pulling tool. A second embodiment of the present invention will now be described with reference to Figures 17-23. 3823017-1 15 Referring firstly to Figure 17, there is shown a perspective view of a plug, generally indicated by reference numeral 510, for sealing a conduit in accordance with a second embodiment of the present invention. The plug 510 comprises a housing 512 having a longitudinal axis 514. The plug 510 further includes a plurality 5 of seal elements 516 for creating a seal between the plug 510 and the conduit (not shown). Within the housing 512 is a seal setting means 518 for setting the plurality of seal elements 516 by rotationally translating the seal setting means 518 with respect to the housing 512 such that the plurality of seal elements 516 are compressed into a sealing engagement with the conduit (not shown). The plug further includes an 10 anchoring system 520 for securing the plug 10 in the conduit (not shown). The anchoring system 20 includes a dog expander ramp (shown and discussed in connection with Figure 18) and a plurality of dogs 522. The anchoring system 520 is set by anchor setting means 524. Rotation of the anchor setting means 524 with respect to the housing 512 translates the anchor setting means 524 with respect to the 15 housing 512 and forces the dogs 522, through the dog expander ramp 528, into engagement with recesses in the conduit (not shown). These and additional elements of the plug 510 can be seen on Figure 18, a sectional view of the plug 510 taken through line A-A on Figure 17. As can be seen from Figure 18, the anchor setting means 524 comprises a dog nut 526, the anchoring 20 system 520 comprises six dogs 522 and the housing 512 further comprises a dog expander ramp 528. The dog nut 526 engages the housing 12 by means of a threaded connection 530. As the dog nut 526 is rotated it translates to the right of Figure 18. This translation acts on the dog expander ramp 528 which also moves to the right. The dog expander ramp 528 includes a leading surface 532 which engages a back 25 surface 534 of the dogs 522. Co-operation between the dog expander ramp leading surface 532 and the dog back surface 534 causes the dogs 522 to move outwards from the plug 510, through apertures 521 in the housing 512, in a direction perpendicular to the longitudinal axis 514. Referring now to Figure 19, there is shown a sectional view through line B-B 30 from Figure 18. This shows that the dog expander ramp 528 is rotationally fixed to the housing 512 by means of a key 536. Therefore as the dog expander ramp 528 translates to the right it does not rotate. Referring back to Figure 18, the plug 510 further includes an anchor ratchet 538. The anchor ratchet 538 comprises a set of teeth or serrations (not shown) in the 3823017-1 16 form of a buttress, located on an end surface 544 of the dog nut 524 and three complementary anchor ratchet tangs (not shown on Figure 18) located on a first rotary lock ring 546 pinned to the dog expander ramp 520. The engagement of the tangs and the teeth or serrations allows rotation in one direction but not the other as the tang 5 prevents rotation in the opposite direction because it would lock against the buttress. The first rotary lock ring 546 can be best seen in Figure 20a, a perspective view of the first rotary lock ring 546. The first rotary lock ring 546 comprises three tangs 542 located on, and sitting proud of, an external surface 552 of the first rotary lock ring 546. One of the tangs is also shown in enlarged detail on Figure 20a. The 10 tangs 542 are machined into the first rotary lock ring 546, and are bent outwards such that edge 553 forms a ratchet with the serrated face 544 of dog nut 524. The first rotary lock ring 546 is centred on the longitudinal axis 514 of the plug 10 such that the anchor ratchet 538 is arranged along an arc centred on, and substantially perpendicular to the longitudinal axis 514. 15 Referring back to Figure 18, the plurality of seal elements 516 comprises a stack of fifteen frusto-conical washers 554. Frusto-conical washers 554 are used because a high expansion ratio is achievable by compression of a frusto-conical washer permitting the plug 510 to be run into position within a conduit without building up a significant head of pressure in front of the plug 510. The plug 510 is 20 set by seal setting means 518 which comprises a two-part mandrel 556ab. The mandrel 556ab is connected to the housing 512 by means of a threaded connection 558. The threaded connection 558 is such that if the seal setting means 518 is rotated it translates to the left of Figure 17, travelling along the threaded connection 558. This motion compresses the frusto-conical washers 554 increasing the radius 560 25 defined by the frusto-conical washers 554 from the longitudinal axis 514. As they expand, the frusto-conical washers 554 engage the wall of a conduit (not shown) and form a seal with the conduit. Over compression of the frusto-conical washers 554 is prevented by stop 562 engaging with housing no-go 564. 30 The plug 510 further includes a seal ratchet 580. The seal ratchet 580 comprises a set of teeth (not shown) located on an external surface 582 of the mandrel 556 and six complementary seal ratchet tangs (not shown on Figure 18) located on a second rotary lock ring 584. The second rotary lock ring 584 can be best seen in Figure 20b, a plan view of the second rotary lock ring 584. The second rotary lock 3823017-1 17 ring 584 is secured to the housing no-go 564 by lugs 586. The second rotary lock ring 584 comprises six tangs 588 located on, and sitting proud of, an internal surface 590 of the second rotary lock ring 584. The second rotary lock ring 584 is centred on the longitudinal axis 514 of the 5 plug 510 such that the seal ratchet 580 is arranged along an are centred on, and substantially perpendicular to the longitudinal axis 514. The setting of the plug 510 is a two stage process because the plug 510 is arranged such that rotation in one direction (here after referred to as direction X) will drive the dog nut 526 and set the dogs 522 in a conduit recess, and rotation in the 10 opposite direction (hereafter referred to as direction Y) will drive the mandrel 556 and set the sealing element 516. Referring now to Figure 21, there is shown a perspective view of a plug running adapter generally indicated by reference numeral 610 for setting the plug 510 in a conduit in accordance with a second embodiment of the present invention. The 15 plug running adapter includes a housing 612, and a tubular member 614 extending from the housing 612. The tubular member 614 has a longitudinal axis 616, an outer surface 618 and an inner surface 620. The outer surface 618 is adapted to engage the anchor setting means 524 of the plug 510 and the inner surface 620 is adapted to engage the seal setting means 518 of the plug 510. 20 Located on the inner surface 620 of the tubular member 614 are first engagement element 622 and located on the outer surface 618 of the tubular member 614 are second engagement elements 624. The first and second engagement elements 622,624 can be best seen on Figure 22, a sectional view taken through line C-C of Figure 21. Each engagement element 622,624 is pivoted at one end about a 25 pivot 626. The first engagement element 622 are biased to sit proud of the internal surface 620 of the tubular member 614 and the second engagement elements 624 are biased to sit proud of the outer surface 618 of the tubular member 614, as shown in Figure 22. Associated with each of the first engagement elements 622 -are first tubular member recesses 628 and associated with each of the second engagement 30 elements 624 are second tubular member recesses 630. Referring to both Figures 17 and 22 the anchor setting means 524 in the form of dog nut 526 have a number of second complimentary notches 640 in the internal surface 642 of the dog nut 526. When the rotation of the running adapter 612 is in the direction X, the second engagement elements 624 engage the inner surface 644 of 3823017-1 18 the second complimentary notches 640 thereby driving the dog nut 528, and setting the dogs 522. When the rotation of the running adapter is in direction Y, the inner surface 642 of the dog nut 528 depresses the second engagement 630 elements 624 into the second tubular member recesses 630. 5 Continuing to refer to Figures 17 and 22, the first engagement elements 622 are adapted to engage with first complimentary notches 632 on the outer surface of the mandrel 556. The complimentary notches 632 are separated by fingers 634. The pivotal mounting of the first engagement elements 622 means that when the running adapter 610 is driven in direction Y, the first engagement elements 622 engage with 10 the inner surface 636 of the first complimentary notches 632 thereby rotating the mandrel 556, and setting the seal element 516. When the direction of the running adapter is reversed, to direction X, the upper surface 638 of the fingers 634 press the first engagement elements 622 into the first tubular member recesses 628 such that there is no driving engagement between the running adapter 610 and the mandrel 556. 15 Referring now to Figure 23, comprising Figures 23a to 7d, there is shown a schematic of the plug 510 of Figure 17 being set in a wellbore 700. The plug 510 is shown in Figure 23a attached to the running adapter 610, which in turn is suspended from a wireline cable 710. The running adapter 610 includes a latch (not shown) which engages a recess 557 (Figure 18) in the inner 20 surface of the mandrel 556. In Figure 23a, the plug/running adapter 510,610 is being run into the wellbore 700. When the plug 510 is in the correct position, shown in Figure 23b the dogs 522 are set in recesses 712. The dogs are set, as described above, by rotating the tubular member 614 (Figure 21) of the running adapter 610 in a first direction. This 25 rotation drives the dog nut 526 (Figure 18) towards the dogs 522, which are moved into the position shown in Figure 23b by the action of the dog expander ramp 528 (Figure 18). Once the dogs 522 have been set in the recesses 712, and the plug 510 is correctly located in the wellbore 700, the running adapter tubular member 614 is 30 rotated in a second direction, which is opposite to the first direction. This rotation drives the two-part mandrel 556a,556b, which in turn compresses the frusto-conical washers 714 into a sealing engagement with the wall 716 of the wellbore 700, as shown in Figure 23c. The plug 510 is now set in the wellbore 700. 3823017-1 19 Finally the running adapter 610 is disconnected by shearing the running adapter latch (not shown) from the plug recess 557 (Figure 18). The adapter 610 is then withdrawn to surface. Various modifications and improvements may be made to the embodiments 5 hereinbefore described without departing from the scope of the invention. For example, it will be understood that any suitable form of seal element may be used or slips may be used instead of the dogs described. For example, multiple metal seals could be used or, alternatively, a combination of metal and plastic seals where seal bore damage prevents an all metal seal arrangement from testing. Additionally, with 10 regard to the first described embodiment, although a two trip releasing and recovery of the plug has been described, a single trip wireline tool could be used or the running adapter could be modified to retrieve the plug as well as set the plug. Those of skill in the art will also recognise that the above described embodiment of the invention provides a plug in which backlash is substantially 15 reduced. The use of a rotary lock mechanism substantially prevents any movement within the plug and is unaffected by vibration which can occur at the wellhead. Furthermore, from a simple rotational input the running adapter produces both rotational and axial force to set and seal the plug in the conduit. Because the running adapter delivers all the force required during setting and because the seal element is a 20 smaller diameter than the diameter of the conduit at the point of sealing, there is no requirement for jarring and no damage is done to the conduit bore. 3823017-1

Claims (23)

1. A plug for sealing a conduit which extends downhole, the plug comprising: a first body section; a second body section having an energising portion and a de-energising portion; and at least one seal element for creating a seal between the plug and a conduit, the at least one seal element being energised and de-energised by movement of the first body section relative to the second body section; such that to energise the at least one seal element, the energising portion of the second body section is engaged with the at least one seal element and to de-energise the at least one seal element the de-energising portion of the second body section is disposed within and is engaged with the at least one seal element, the de-energising portion defining a fluid flow path around the at least one seal element, wherein the fluid flow path around the at least one seal element is not defined by a portion of the conduit.
2. The plug of any preceding claim, wherein the at least one seal element is adapted to be energised by axially translating the first body section relative to the second body section in the setting direction.
3. The plug of any preceding claim, wherein the plug is adapted to be set by the application of linear forces to one or both of the first body section and the second body section to axially translate the first body section relative to the second body section in the setting direction.
4. The plug of any preceding claim, wherein the at least one seal element is adapted to be energised by rotationally translating the first body section relative to the second body section in the setting direction.
5. The plug of any preceding claim, wherein the at least one seal element is a metal seal element.
6. The plug of any preceding claim, wherein the at least one seal element is a stack of frusto-conical washers. 21
7. The plug of claim 6, wherein at least one frusto-conical washer in the stack is adapted to form an independent metal-to-metal seal with a conduit from at least one other frusto-conical washer in the stack. 5
8. The plug of either of claims 6 or 7, wherein the frusto-conical washers are steel.
9. The plug of any of claims I to 5, wherein the at least one seal element is a 10 plurality of metal seals, or a combination of metal and plastic seals.
10. The plug of any of claims 6 to 9, wherein adjacent seals or washers are separated by at least one layer of softer material. 15
11. The plug of claim 10, wherein the softer material is polymeric.
12. The plug of claim 10, wherein the at least one layer is a laminate of softer material. 20
13. The plug of claim 10, wherein the at least one layer is a laminate of a number of softer materials.
14. The plug of claim 12 or 13, wherein the laminate is a layer of PTFE sandwiched between layers of PEEK. 25
15. The plug of any preceding claim, wherein the at least one seal element is energised by compression,
16. The plug of claim 15, wherein where the at least one seal element is a stack of 30 frusto-conical washers, in the uncompressed state each washer is at an angle of 8' to the horizontal.
3823017-1 22
17. The plug of claim 15 or 16, wherein where the at least one seal element is a stack of frusto-conical washers, when the at least one seal element is energised, the washers arc not flattened.
18. The plug of any of claims 15 to 17, wherein in the energised configuration, each frusto-conical washer is at an angle of 50 to the horizontal.
19. The plug of any of claims 15 to 18, wherein in an uncompressed configuration, the stack of frusto-conical washers describes an external diameter less than that of the plug body.
20. The plug of any preceding claim, wherein to release the at least one seal element, the second body section is moved relative to the at least one seal element.
21. The plug of claim 20, wherein the flow path is provided by at least one groove defined by the second body section.
22. The plug of claim 20 or 21, wherein the plug further comprises a flow path locking means to lock the plug in the released position.
23. A method of retrieving a plug from a conduit which extends downhole, the method comprising the steps of de-energising at least one seal element, the at least one seal element forming a seal between the plug and a conduit, by movement of a first body section relative to a second body section to a position in which a de-energising portion of the second body section is disposed within and is engaged with the at least one seal element, the de energising portion defining a fluid flow path around the at least one seal element, wherein the fluid flow path around the at least one seal element is not defined by a portion of the conduit; and retrieving the plug from the conduit.
AU2012201022A 2004-10-29 2012-02-22 Improved Plug Ceased AU2012201022B2 (en)

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GB0423992.7 2004-10-29
AU2005298359A AU2005298359B2 (en) 2004-10-29 2005-10-28 Improved plug
AU2012201022A AU2012201022B2 (en) 2004-10-29 2012-02-22 Improved Plug

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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1926017A (en) * 1932-07-02 1933-09-05 Walter T Wells Packer
US2498791A (en) * 1946-06-22 1950-02-28 James M Clark Well device

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1926017A (en) * 1932-07-02 1933-09-05 Walter T Wells Packer
US2498791A (en) * 1946-06-22 1950-02-28 James M Clark Well device

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