RUPTURE APPARATUS

Abstract

A rupture apparatus (50) often deployed within a wall of a casing string (53) of an oil and gas well, comprising a housing (51) defining a housing bore (54) with a bore inlet and a bore outlet; a carriage carrying a rupturable component (12) the carriage being moveable in the housing bore between a rupturable position, an open and a closed position. Thus the bore can be opened or closed or closed subject to rupture of the rupturable component (12). Moreover, after rupture the bore can still be closed. Wireless signals are normally used to for control, especially electromagnetic or acoustic signals. A pressure balancing port (6) may be defined in a wall of the housing allowing fluid communication between at least a portion of the housing bore, and an outside of the housing which can pressure-balance the carriage such that it remains stationary unless actuated.

Claims

1. A rupture apparatus comprising: a housing defining a housing bore with a bore inlet and a bore outlet; a carriage carrying a rupturable component; wherein the carriage is moveable in the housing bore between a rupturable position and at least one of an open and closed position.

2. The rupture apparatus of claim 1 comprising a wireless communication module configured to receive at least one of coded pressure pulse, acoustic and electromagnetic signals, to direct movement of the carriage.

3. The rupture apparatus of claim 1, comprising at least one seal between an outer surface of the carriage and an inner surface of the housing bore.

4. The rupture apparatus of claim 3 wherein the at least one seal can alternate between actively sealing with the inner surface of the housing bore, and being inactive.

5. The rupture apparatus of claim 3 comprising a plurality of seals, wherein at least one of the plurality of seals is configured to be inactive whilst at least another two of the plurality of seals actively seal between the inner surface of the housing bore and the carriage.

6. The rupture apparatus of claim 3 wherein the seal(s) is/are non-elastomeric.

7. The rupture apparatus of claim 1 wherein the carriage is moveable between the rupturable position and the closed position.

8. The rupture apparatus of claim 1 wherein the carriage is moveable between the rupturable position and the open position.

9. The rupture apparatus of claim 1 further comprising a pressure balancing port defined in a wall of the housing allowing fluid communication between at least a portion of the housing bore, and an outside of the housing.

10. The rupture apparatus of claim 9, wherein in the open position, at least a portion of a first face of the rupturable component is exposed to a first pressure, and at least a portion of an opposing face of the rupturable component is exposed to a second pressure, one of said faces being exposed to at least one of said first and second pressure via the pressure balancing port.

11. The rupture apparatus of claim 1 wherein the carriage is configured to move in the housing bore in an axial direction, parallel with a main longitudinal axis of the housing bore.

12. The rupture apparatus as claimed in claim 1, which is disposed on a tubular member.

13. The rupture apparatus of claim 12, wherein in the closed position, at least a portion of two opposing faces of the rupturable component are in fluid communication with one of an outside of the tubular member and the inside of the tubular member.

14. The rupture apparatus of claim 12, wherein in the rupturable position, at least a portion of one face of the rupturable component is in fluid communication with a port of the tubular member, and at least a portion of a second face of the rupturable component is in fluid communication with an outside of the tubular member.

15. The rupture apparatus of claim 12, wherein the carriage comprises a longitudinal tubular member having at least one carriage port between a bore of the longitudinal tubular member and an outside thereof.

16. The rupture apparatus of claim 12, wherein the primary path for fluid flow through the rupture apparatus is defined in the housing bore, such that the primary fluid flow path is in part defined by the tubular member.

17. A tubular member apparatus comprising the rupture apparatus as claimed in claim 1 and a tubular member, of claim 12, wherein the tubular member defines an inner bore.

18. The tubular member apparatus of claim 17 wherein the housing bore is in fluid communication with at least a portion of an outside of the tubular member and the inner bore of the tubular member.

19. The tubular member apparatus of claim 17, wherein a main axis of the housing bore is off-centre compared to a main axis of the tubular member.

20. The tubular member apparatus as claimed in claim 17, wherein the housing bore is within a wall of the tubular member.

21. The tubular member apparatus as claimed in claim 17, wherein the rupture apparatus is provided in a side pocket mandrel.

22. The tubular member apparatus of claim 17 wherein the tubular member forms part of a casing string.

23. The tubular member apparatus of claim 22 wherein the casing string comprises an inner diameter of at least 5 inches (127 mm).

24. A well comprising the rupture apparatus of claim 1.

25. A well as claimed in claim 24 wherein the well is a subsea well.

26. A well as claimed in claim 24, wherein the rupture apparatus is coupled to a wireless data communication module configured to transmit said signals in at least one of the following forms: electromagnetic, acoustic, coded pressure pulses and inductively coupled tubulars; especially at least one of acoustic and electromagnetic.

27. A well as claimed in claim 24, wherein the rupture apparatus is at least one of at least 500 m, 1000 m and at least 1500 m deep in the well.

28. (canceled)

29. A system comprising the rupture apparatus as claimed in claim 1, and an axial-movement actuator configured to cause axial movement of the carriage in the housing bore.

30. The system as claimed in claim 29, wherein the actuator is hydraulically actuated.

31. The system as claimed in claim 29, wherein the actuator is a single actuator which provides for movement of the carriage between the rupturable position, the open position and the closed position.

32. The system as claimed in claim 29, wherein the actuator is powered by in-well power source, such as a battery.

33. A system comprising a rupture apparatus, an actuator and a tubular having an inner bore, the rupture apparatus comprising: a housing defining a housing bore with a bore inlet and a bore outlet; a carriage carrying a rupturable component; wherein the carriage is moveable in the housing bore between a rupturable position, an open position and a closed position; wherein the housing bore is in fluid communication with at least a portion of an outside of the tubular member and the inner bore of the tubular member; and wherein the actuator is actuable to move the carriage between the rupturable position, the open position and the closed position.

34. A well comprising the tubular member apparatus as claimed in claim 17.

35. A well as claimed in claim 34, wherein the tubular member apparatus comprises a tubular, in part, defining at least one of a B-annulus and outer annulus.

36. A system comprising the tubular member apparatus as claimed in claim 17, and an axial-movement actuator configured to cause axial movement of the carriage in the housing bore.

Description

[0081] Embodiments of the invention will now be described by way of example only and with reference to the accompanying drawings, in which:

[0082] FIG. 1a is a sectional perspective view of a casing string with a rupture apparatus with moveable seal carriers shown in a rupturable position;

[0083] FIG. 1b is a cross-sectional view of the rupture apparatus of FIG. 1a;

[0084] FIG. 1c is a cross-sectional view of the FIG. 1a rupture apparatus shown in a fully closed position;

[0085] FIG. 1d is a cross-sectional view of the FIG. 1a rupture apparatus shown in a fully open position;

[0086] FIG. 2a is a cross-sectional view of an alternative embodiment of a rupture apparatus with a sealing rod, shown in a rupturable position;

[0087] FIG. 2b is a cross-sectional view of the FIG. 2a rupture apparatus shown in a fully closed position;

[0088] FIG. 2c is a cross-sectional view of the FIG. 2a rupture apparatus shown in a fully open position;

[0089] FIG. 3 is a cross-sectional view of an alternative sealing rod comprising a discrete rupture disc;

[0090] FIG. 4a is a cross-sectional view of a further embodiment of the FIG. 2a rupture apparatus on an outer wall of a side pocket mandrel; and

[0091] FIG. 4b is a cross-sectional view of the portion bounded by the rectangular box ‘B’ in FIG. 4a, showing the rupture apparatus in more detail.

[0092] FIG. 1a shows a rupture apparatus 50 on an outer face of a tubular member 52 which forms part of a casing string 53 in a wellbore annulus 55.

[0093] As shown in more detail in FIGS. 1b-1d, a housing bore 54 of the rupture apparatus 50 is defined in a valve housing 51. A seal carriage comprising three moveable seal carriers 41, 42, 43, each with respective seals 31, 32, 33 attached, is provided in the housing bore 54. The seal carriage can be moved to change the valve position between open, closed and rupturable valve positions to selectively allow or resist fluid communication between the bore of the tubular 52 and the annulus 55, via a main port 15 in the tubular 52. A pressure balancing port 6 is provided in the valve housing 51 to equalise pressure on either side of one or more of the moveable seal carriers 41, 42, 43 as described below.

[0094] FIGS. 1a-1d show the rupture apparatus 50 in its three fundamental positions: a rupturable position in FIGS. 1a and 1b, a fully closed position in FIG. 1c and a fully open position in FIG. 1d. The rupture apparatus 50 operates through axial movement of the seal carriers 41, 42, 43 in the housing bore 54.

[0095] The seal carriers 41, 42, 43 may be positioned (and repositioned) independently of the rupture-state of a rupture disc 12 in the first seal carrier 41, and so the rupture apparatus 50 may be fully closed, fully opened, or placed in the rupturable position indefinitely. The latter valve position allows a differential pressure on either side of the rupture disc 12 to rupture through the rupture disc 12 if it exceeds a threshold value. In this example, the pressure value that the rupture disc 12 ruptures at is 10% below the pressure rating of the tubular 52.

[0096] It is an advantage of such embodiments of the invention that the rupture apparatus 50 may be moved between positions regardless of the state of the rupture disc 12, and without rupturing the rupture disc 12.

[0097] In FIG. 1b, the rupture apparatus 50 of FIG. 1a is shown in more detail.

[0098] The seal carriers 41, 42, 43 of the rupture apparatus 50 are situated within the housing bore 54. The seal carriers 41, 42, 43 are connected to each other, with the first seal carrier 41 being connected to the second, and the second seal carrier 42 being connected to the third seal carrier 43 via a coupling 7. The housing bore 54 is in fluid communication with the annulus 55 outside the valve housing 51.

[0099] The first seal carrier 41 carries a first seal 31, and is tubular with the rupture disc 12 formed across its inside. The second seal carrier 42 carries a second seal 32, and has a plurality of seal carrier ports 29. The seal carrier ports 29 are configured to allow fluid communication from the port 15 in the tubular 52 to the rupture disc 12, via the second and then first seal carriers 42 & 41. The third seal carrier 43 and third seal 33 are connected to an axial-movement actuator via an actuator extension piece 2. The three seals 31, 32, 33 are configured to seal between the housing bore 54 and their respective seal carriers 41, 42, 43, such that further sealing elements (e.g. a sealing thread) are not required. The diameters of all three seals 31, 32, 33 are the same which helps to load-balance the seal carriers 41, 42, 43 across the port 15. In this example, the seals are V-seals.

[0100] The port 15 in the tubular 52 intersects the housing bore 54 and so allows fluid communication between the housing bore 54 and the tubular 52. The pressure balancing port 6 allows fluid communication between the housing bore 54 and the annulus 55.

[0101] The actuator extension piece 2 is configured to move the seal carriers 41, 42, 43 and their respective seals 31, 32, 33 along the housing bore 54 between the three fundamental positions of the rupture apparatus 50.

[0102] In FIG. 1b, the rupture apparatus 50 is shown in the rupturable position. In the rupturable valve position, the axial position of the seal carriers 41, 42, 43 with respect to the valve housing 51 are such that the first and second seals 31, 32 are positioned on either side of the port 15. When the rupture apparatus 50 is in the rupturable position, the first and second seals 31, 32 are active and seal against the housing bore 54, but the third seal 33 is unseated in a slightly larger-diameter portion of the housing bore 54.

[0103] In the rupturable valve position, the seal carrier ports 29 are positioned at the port 15. Thus, the seal carrier ports 29 are fluid-accessible via the port 15.

[0104] The coupling 7 between the second and third seal carriers 42, 43 has a reduced diameter in its central portion. In this valve position, the pressure balancing port 6 in the valve housing 51 is adjacent to the coupling 7. The pressure balancing port 6 and coupling 7 provide a fluid path between the annulus 55 and the housing bore 54, and so annulus pressure acts on the second seal 32, as well as the first seal 31 from the opposite end of the housing bore 54, thus balancing the load on the first and second seal carriers 41, 42 across the port 15 so that they do not move in the absence of other forces.

[0105] The rupture disc 12 is in fluid communication with the casing string 53 (via the seal carrier ports 29, the port 15, and the tubular 52), and the annulus 55 (via the first seal carrier 41 and the housing bore 54). This can result in a pressure differential acting on the rupture disc 12, despite the load-balanced condition of the seal carriers 41, 42, 43.

[0106] So long as the rupture disc 12 has not ruptured, the rupture apparatus 50 in the FIG. 1a position will be conditionally closed. If the pressure differential acting on the rupture disc 12 exceeds a threshold value, then the rupture disc 12 will rupture and allow fluid communication between the annulus 55 and the casing string 53 via the tubular 52. This may help to keep the annular pressure from becoming dangerously high.

[0107] If the rupture disc 12 has been ruptured, the rupture apparatus 50 when in the FIGS. 1a & 1b position will effectively be open thereafter. If it is desired to close the rupture apparatus 50 after the rupture disc 12 has ruptured, then the seal carriers 41, 42, 43 can be moved to the closed position.

[0108] Load-balancing the seal carriers 41, 42, 43 across the port 15 when the rupture apparatus 50 of such embodiments of the invention is in the rupturable valve position is advantageous, because it means that the actuator does not need to maintain a force on the seal carriers 41, 42, 43 (via actuator extension piece 2) to prevent the rupture apparatus 50 from moving from its position. Moreover, when it is desired to move the rupture apparatus 50 to a different valve position, there is less force required to be applied by the actuator extension piece 2.

[0109] A seal being unseated also aids in the reduction of force required to move the seal carriage, especially in high pressure applications. Having seal 33 unseated reduces the friction caused by static pressure on the seals, and reduces the force needed to move the rupture apparatus 50 into a different position.

[0110] The actuator extension piece 2 moves the seal carriers 41, 42, 43 axially in the housing bore 54 to move the rupture apparatus 50 from the rupturable (FIGS. 1a and 1b) position to another position, in this case the fully closed FIG. 1c position. A wireless control signal in the form of an acoustic or electromagnetic (EM) signal is sent to a receiver (not shown) coupled to the actuator from the surface or another communications source (not shown) to initiate the movement of the actuator extension piece 2.

[0111] In FIG. 1c, the rupture apparatus 50 is shown in the fully closed position. In the fully closed position, the axial position of the seal carriers 41, 42, 43 with respect to the valve housing 51 is such that the second and third seals 32, 33 are positioned on either side of the port 15. The second and third seals 32, 33 are active and effectively seal off the port 15, whilst the first seal 31 is unseated.

[0112] As with the rupturable valve position shown in FIGS. 1a & 1b, the seal carriers 41, 42, 43 are also load-balanced across the port 15 in the fully closed position. The second seal carrier 42 is exposed to the annulus pressure through the housing bore 54. The diameter of the actuator extension piece 2 being less than the housing bore 54 results in the third seal carrier 43 being exposed to the annulus pressure through the pressure balancing port 6. Both second and third seal carriers 42, 43 are indirectly exposed to the casing string pressure via the port 15. In a manner similar to that described in relation to FIG. 1b, there are balanced forces acting on the second and third seals 32, 33.

[0113] The annulus 55 is still in fluid communication with one side of the rupture disc 12, through the first seal carrier 41. However, the rupture disc 12 is no longer in fluid communication with the casing string 53. Because the first seal 31 is now unseated in a larger-diameter section of the housing bore 54, the other side of the rupture disc 12 is also in fluid communication with the annulus 55, via seal carrier ports 29. Therefore, when the rupture apparatus 50 is in the fully closed FIG. 1c position, the rupture disc 12 is pressure balanced and will not rupture, if it is intact.

[0114] This is an advantage of such embodiments of the invention when it is desired to prevent inadvertent rupture of the rupture disc 12.

[0115] In a modified embodiment, the first seal 31 can remain seated. To provide for pressure balance across the rupture disc 12, a further pressure balancing port (not shown) can be provided in the housing 51 between the first seal 31 and the second seal 32. For certain embodiments, maintaining the seal in an active position can improve its longevity, as opposed to switching between active and inactive states.

[0116] The actuator extension piece 2 moves the seal carriers 41, 42, 43 axially in the housing bore 54 to move the rupture apparatus 50 from the fully closed FIG. 1c position to another position, in this case the fully open FIG. 1d position. An EM or acoustic wireless control signal is sent to the receiver (not shown) coupled to the actuator from the surface or another communications source (not shown) to initiate movement of the actuator extension piece 2.

[0117] FIG. 1d shows the rupture apparatus 50 in the fully open position. In the fully open position, the axial position of the seal carriers 41, 42, 43 with respect to the valve housing 51 is such that the port 15 is no longer sealed off by any two seals but is in direct fluid communication with the housing bore 54 and annulus 55, bypassing the seal carriers 41, 42, 43 altogether.

[0118] The seal carriers 41, 42, 43 remain stationary whilst the rupture apparatus 50 is in the fully open position because there are no unbalanced forces acting on them.

[0119] In use, if the rupture disc 12 has not been ruptured, both sides of the rupture disc 12 are in fluid communication with the annulus 55, one via the pressure balancing port 6 and the other via the housing bore 54 and the first seal carrier 41, so there is no pressure differential acting here, and the rupture disc is not at risk of inadvertently rupturing.

[0120] Thus an advantage of preferred embodiments of the invention, such as the above embodiment, is that casing annuli can be more conveniently controlled using the rupture apparatus. Accordingly if these annuli increase in pressure, for example caused by fluids leaking into the annulus, or for example warm fluids being produced in the tubular, such embodiments can be used to bleed the pressure therefrom. As well as safety benefits, in certain situations, this can allow higher production rates to be used, especially for higher temperature wells, where the heat sustained at a higher flow rate could otherwise over-pressure an annulus when being produced.

[0121] If the rupture disk is ruptured, the casing can be maintained in the well with rupture apparatus in a closed position whereas this would have previously caused the well to be abandoned or used in a very restricted manner.

[0122] Advantageously, regardless of the valve position, the seals 31, 32, 33 are potentially less exposed to the potentially erosive fluid flow. The rupture apparatus 50 of such embodiments of the invention is designed such that the sealing surfaces are kept well away from the fluid flow-path.

[0123] FIGS. 2a-2c show a further embodiment which includes like parts with the FIGS. 1a-1d embodiment and these are not described again in detail. The reference numerals of the like parts share the same latter two digits in both embodiments, but differ in that they are prefixed with a ‘1’ in this second embodiment.

[0124] In the FIGS. 2a-2c embodiment of a rupture apparatus 150, an axially-moveable sealing rod carriage 16. The sealing rod carriage 16 (hereinafter “sealing rod 16”) carries a rupture disk 112, but does not carry seals . Instead, stationary first and second seals 131, 132 are provided.

[0125] The sealing rod 16 is partially tubular. It contains sealing rod ports 25 as well as the rupture disc 112 which is formed across the inside of the sealing rod 16. It also contains secondary sealing rod ports 26 which are disposed further along the sealing rod 16, on the other side of the rupture disc 112.

[0126] The rupture apparatus 150 has the same three fundamental positions as in the FIGS. 1a-1d embodiment (rupturable, fully closed and fully open) and is likewise load-balanced across the port 115 in these valve positions.

[0127] First and second seals 131, 132 are mounted within the housing bore 154 of the valve housing 151. The first and second seals 131, 132 are held in place in the housing bore 154 by a central cylindrical spacer 19, and on their other sides by a respective retaining member 17, 24. The cylindrical spacer 19 has a hole therein to allow fluid to pass between the spacer and the port 115. The seals 131, 132 are configured to seal between the housing bore 154 and the sealing rod 16.

[0128] The first and second seals 131, 132 have the same diameter as each other. As with the previous embodiment, this helps when load-balancing the sealing rod 16 across the port 115.

[0129] In FIG. 2a, the sealing rod 16 is positioned such that the sealing rod ports 25 align with the port 115. The rupture apparatus 150 is shown in the rupturable valve position.

[0130] The sealing rod ports 25 provide fluid-access from the tubular 152 through the port 115 to the inside of the sealing rod 16, and to the rupture disc 112 formed across the inside of the sealing rod 16.

[0131] In use, the rupture disc 112 experiences a differential pressure because annulus 155 pressure is acting on one side of the disc, and the casing string pressure (via the tubular 152) is acting on the other.

[0132] As with the previous embodiment, when the rupture apparatus 150 is in the rupturable valve position the differential pressure does not impart any unbalanced load to the sealing rod 16, across the port 115.

[0133] FIG. 2b shows the rupture apparatus 150 of the sealing rod embodiment in the fully closed position. The sealing rod 16 has moved axially along the housing bore 154 such that none of the sealing rod ports 25, 26 align with the port 115. The seals 131, 132 obstruct fluid flow from the tubular 152 to the ports of the sealing rod 25, 26.

[0134] Fluid is completely restricted from flowing between the tubular 152 and the annulus 155.

[0135] As with the previous embodiment, when the rupture apparatus 150 is in the fully closed position the differential pressure between the casing string (via the tubular 152) and the annulus 155 does not impart any unbalanced load to the sealing rod 16 across the port 115.

[0136] Annulus 155 pressure acts on both sides of the rupture disc 112, and so does not rupture the disc if it is still intact.

[0137] FIG. 2c shows the rupture apparatus 150 of the sealing rod embodiment in the fully open position, in which the sealing rod 16 is positioned such that the secondary sealing rod ports 26 align with the port 115.

[0138] Fluid can flow freely between the tubular 152 and the annulus 155.

[0139] Annulus 155 pressure acts on both sides of the rupture disc 112, and so does not rupture the disc if it is still intact.

[0140] FIG. 3 shows a further embodiment of the sealing rod 16. This embodiment includes like parts with the FIGS. 2a-2c embodiment and these are not described again in detail. The reference numerals of the like parts share the same latter two digits in both embodiments, but differ in that they are prefixed with a ‘2’ in this further embodiment.

[0141] The FIG. 3 sealing rod carriage 216 contains a discrete rupture disc component 212, which may be used in place of the rupture disc 112 used in the FIGS. 2a-2c embodiment.

[0142] This alternative version of the sealing rod 216 may be used in place of the sealing rod 16 of said FIGS. 2a-2c embodiment.

[0143] An advantage of such embodiments of the invention is that the rupture disc component 212 may be more readily replaced because it is a separate part to the rest of the sealing rod using conventional means, such as wireline or coiled tubing.

[0144] FIGS. 4a and 4b show a further embodiment of the present invention which includes like parts with the FIGS. 2a-2c embodiment and these are not described again in detail. The reference numerals of the like parts share the same latter two digits in both embodiments, but differ in that they are prefixed with a ‘3’ in this later embodiment.

[0145] The FIGS. 4a and 4b embodiment comprises a rupture apparatus 350 on an outer face of a side pocket mandrel 359 which forms part of a production tubing string 358a, 358b in a surrounding portion of the well 353.

[0146] As best seen in FIG. 4a, the rupture housing 351 forms part of the side pocket of the side pocket mandrel 359, which is connected to the production tubing 358a, 358b at either end. The side pocket mandrel cavity 359 is in fluid communication with the inside of the production tubing 358a, 358b.

[0147] A conventional gas lift lock 349, such as a BK-2 type lock, is located within the side pocket of the mandrel 359 adjacent one end of the rupture apparatus 350. At the other end of the rupture apparatus 350 is an actuator 302. The actuator 302 is connected to a battery 346, a wireless control module 347, and a pressure sensor 348 to monitor the pressure in the surrounding portion of the well 353. The actuator 302 can thus be powered and controlled from a downhole location, to actuate the rupture apparatus 350 according to the monitored pressure conditions. A pressure sensor may also or alternatively be run into the well on a toolstring, to monitor the pressure within the tubing 358a, 358b and side pocket mandrel cavity 359.

[0148] FIG. 4b shows in more detail the features bounded by the rectangular box ‘B’ in FIG. 4a. The rupture apparatus 350 comprises an axially-moveable sealing rod carriage 316 with a rupture disc 312 and first and second sets of sealing rod ports 325, 326 as described in relation to the FIGS. 2a-2c embodiment.

[0149] A main port 315 intersects the valve housing 351 and is in fluid communication with the surrounding portion of the well 353. A pressure balancing port 306 intersects the inner wall of the side pocket mandrel and the mandrel cavity 359. A flow port 308 is also provided, which also intersects the inner wall of the side pocket mandrel and the mandrel cavity 359.

[0150] In the present embodiment, there is a stationary sleeve comprised of first, second and third portions 371, 372, 373. The sleeve 371, 372, 373 comprises a set of inner seals and a set of outer seals. The first and second inner seals 331, 332 are essentially the same as described in relation to the FIGS. 2a-2c embodiment, but here they are configured to seal between the sealing rod 316 and the inside of the second portion of the sleeve 372. The first and second outer seals 362, 363 have the same diameter as each other and are configured to seal between the housing bore 354 and the stationary sleeve 371, 372, 373.

[0151] The stationary sleeve 371, 372, 373, the sealing rod 316 and the gas lift lock 349 are removeable from the rupture housing 315 as a single unit. These components can be removed from the side pocket mandrel 359 in-situ downhole, and replaced with a conventional passive valve, for example.

[0152] A collect mechanism 361 releasably locks the actuator 302 to the sealing rod 316. Whilst the actuator 302 engages with the sealing rod 316, the flow port 308 remains aligned with a sleeve port 364 near the end of the third portion of the sleeve 373, which keeps part of the sealing rod 316 in fluid communication with the side pocket mandrel cavity 359. By virtue of the pressure balancing port 306, the opposing side of the sealing rod 316 is also kept in fluid communication with the mandrel cavity 359. This helps to ensure the pressure and forces are balanced across the rod 316 and the inner seals 331, 332 such that force from the actuator need not always be exerted on them to maintain the sealing rod's 316 position. The pressure balancing port 306 also helps to ensure the removeable parts can be removed from the housing bore 354 with greater ease.

[0153] The rupture apparatus 350 has the same three fundamental positions as in the FIGS. 2a-2c embodiment (rupturable, fully closed and fully open) and is likewise load-balanced across the main port 315 in these valve positions.

[0154] In FIG. 4b, the rupture apparatus 350 is shown in the open valve position, wherein the sealing rod 316 is positioned such that the sealing rod ports 326 align with the main port 315. In this position, there is unconditional fluid communication from the mandrel cavity 359 to the surrounding portion of the well 353 via the flow port 308 and sealing rod ports 326.

[0155] In the rupturable valve position, the sealing rod 316 is moved axially in the stationary sleeve 371, 372, 373 such that the second set of sealing rod ports 325 are in fluid communication with the main port 315. In use, when it has not been ruptured, the rupture disc 312 can experience a differential pressure because the surrounding well pressure 353 is acting on one side of the disc 312, and the mandrel cavity 359 pressure is acting on the other.

[0156] In the closed valve position, the sealing rod 316 is moved axially further in the stationary sleeve 371, 372, 373 such that both sets of sealing rod ports 325, 326 are beyond the second inner seal 332. The closed section of the rod 316 is then positioned between the seals 332 and blocks communication to the port 315. In this position, there is no fluid communication between the mandrel cavity 359 and the surrounding well 353. Both sides of the rupture disc 312 are exposed to the pressure inside the mandrel bore 359 via the flow port 308 and the sealing rod ports 325, 326 on one side and pressure balancing port 306 on the opposing side.

[0157] The first seal carrier, sealing rod or discrete rupture disc component may be of a welded construction. This can help support the seal and/or the rupture disc. This construction may be advantageous for constructing a sufficiently robust seal and/or rupture disc.

[0158] The seals may be of a metallic construction to provide metal-to-metal seals between their respective seal carriers or sealing rod, and the housing bore.

[0159] The diameters of the seals in the above embodiments may optionally be different from one another. The actuator extension piece may optionally be used to force or assist the seal carriers or sealing rod to stay in one position, for example, in the case of an unbalanced load condition across the seal carriers or sealing rod.

[0160] In certain embodiments, the rupture disc may only be capable of rupturing due to a pressure above a certain threshold acting on one of its sides, and may resist rupture as a result of pressure acting on its other side, i.e. it may be a one-way rupture disc.

[0161] In alternative embodiments, the rupture apparatus has two valve positions only: a rupturable position and one of an open position and a closed position. Sensors may be provided in various positions on the apparatus in certain embodiments, such within the housing bore, for example on either side of the rupture disc. They may be used to sense the differential pressure across the rupture disc.

[0162] An advantage of certain embodiments is that a rupture mechanism can be isolated and/or bypassed using a single apparatus and/or actuator, thus also saving costs of providing more than one apparatus and/or actuator. This can also help the apparatus to fit within confined spaces downhole.

[0163] An advantage of certain embodiments is that in the event of an increase in pressure within the bore in the tubular, or within the annulus, the pressure can be reduced by changing the valve position to the open position. The valve can then be reset, that is, it can be moved to the closed valve position (which may be the sealing position) or the rupturable valve position (which may be the safety position). In contrast, conventional rupture discs typically need to rupture to provide pressure relief, and cannot be sealed again. If the rupture disc and associated components are safety-critical, they may need to be recovered to surface and replaced, which incurs significant costs and downtime.

[0164] Embodiments so the invention are particularly useful in a subsea well where the outer annuli are not controllable and are sealed.