TEST TREE AND ACTUATOR

Abstract

A subsea test tree comprises a housing defining a flow path, a valve member mounted in the housing and an actuator coupled to the housing. A drive arrangement extends through a wall of the housing to operatively connect the actuator to the valve. The actuator is operable to operate the valve member to control fluid flow along the fluid pathway. Also disclosed are improvements to actuators.

Claims

1. A subsea test tree, comprising: a housing defining a flow path; a valve member mounted in the housing; an actuator coupled to the housing; and a drive arrangement extending through a wall of the housing to operatively connect the actuator to the valve; the actuator operable to operate the valve member to control fluid flow along the fluid pathway.

2. The subsea test tree according to claim 1, wherein the actuator is isolated from a fluid environment within the housing.

3. The subsea test tree according to claim 1, wherein the drive arrangement comprises a drive shaft.

4. (canceled)

5. The subsea test tree according to claim 1, comprising a rotary valve.

6. The subsea test tree according to claim 1, wherein the housing comprises a recess, and at least part of the actuator is accommodated within the recess.

7. The subsea test tree according to claim 1, wherein one or more parts of the actuator are defined by a wall of the housing.

8. The subsea test tree according to claim 1, comprising an actuator outer casing which lies flush with an outer surface of the housing.

9. The subsea test tree according to claim 1, comprising a cylindrical housing.

10. The subsea test tree according to claim 1, comprising a fluid rotary actuator which is operatively connected to the valve by a drive shaft.

11. The subsea test tree according to claim 10, comprising a vane piston rotatable around a rotation axis within an internal chamber, wherein a piston chamber is defined by the walls of the internal chamber and the vane piston, such that the volume of the piston chamber varies with movement of the piston.

12. The subsea test tree according to claim 11, wherein the vane piston is moveable responsive to a fluid pressure differential across the piston.

13. The subsea test tree according to claim 1, wherein the housing comprises more than one valve distributed along an axis of a cylindrical housing.

14. The subsea test tree according to claim 13, wherein each valve is associated with an actuator on diametrically opposite sides of the housing.

15. The subsea test tree according to claim 14, wherein a said actuator associated with one valve is at least one of axially and circumferentially offset from an actuator associated with an adjacent valve.

16. The subsea test tree according to claim 15, comprising circumferentially offset rotary actuators, which in part axially overlap.

17. A fluid rotary actuator, comprising: an actuator body a vane piston within the actuator body, and coupled to a drive structure; the actuator body and vane piston together defining a piston chamber; the vane piston rotatable around a rotation axis to vary the volume of the piston chamber, under the action of a working fluid within the piston chamber.

18. The fluid rotary actuator according to claim 17, comprising a piston chamber to each side of the vane piston.

19. The fluid rotary actuator according to claim 17, wherein the actuator body is cylindrical.

20. The fluid rotary actuator according to claim 17, wherein an outer surface of the actuator body defines a part-cylindrical profile having an axis normal to the rotation axis.

21. The fluid rotary actuator according to claim 17, wherein the vane piston comprises a tapered vane, wherein at least one of the width and the thickness of the vane piston is tapered.

22. The fluid rotary actuator according to claim 21, wherein the vane extends away from the rotation axis from a stem to a tip, wherein the vane is thicker at the stem than at the tip.

23. The fluid rotary actuator according to claim 21, wherein the thickness of the vane piston decreases with distance from the rotation axis.

24. The fluid rotary actuator according to claim 23, wherein an edge of the vane is curved, such that the thickness of the vane decreases non-linearly with distance from the rotation axis.

25. The fluid rotary actuator according to claim 17, wherein an inner face of the/each piston chamber is a part-spherical surface.

26. The fluid rotary actuator according to claim 17, comprising an inflatable bladder disposed within the/each piston chamber.

27. The fluid rotary actuator according to claim 26, wherein the/each bladder comprises an outer anti-deformation layer and an inner fluid-tight layer.

28. The fluid rotary actuator according to claim 27, wherein the fluid-tight layer is free to move in relation to the anti-deformation layer.

29. The fluid rotary actuator according to claim 27, wherein the anti-deformation layer is fluid tight and the anti-deformation layer is perforated.

30. The subsea test tree according to any one of claim 1, comprising a fluid rotary actuator according to claim 17.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0162] Example embodiments will now be described with reference to the following figures in which;

[0163] FIG. 1 shows a schematic cross section of a lower landing string assembly and a marine BOP;

[0164] FIG. 2 shows the landing string fully landed out within the marine BOP;

[0165] FIG. 3 shows a Sub Sea Test Tree in accordance with the invention;

[0166] FIG. 4 shows a cross sectional view of a part of the SSTT of FIG. 3;

[0167] FIG. 5 shows an exploded perspective view of a fluid rotary actuator;

[0168] FIG. 6 shows a perspective (a) front and (b) rear view of the actuator of FIG. 5;

[0169] FIG. 7 shows a cross sectional view across the rotation axis of the fluid rotary actuator of FIG. 5, showing a vane piston in (a) an intermediate position (b) a first position and (c) a second position;

[0170] FIG. 8 shows an exploded perspective view of a diamond shaped fluid actuator;

[0171] FIG. 9 shows an exploded perspective view of a linear fluid actuator;

[0172] FIG. 10 shows a cross sectional view through the actuator of FIG. 9, showing a drive structure in (a) an intermediate position (b) a first position and (c) a second position, in relation to an actuator body;

[0173] FIG. 11 shows an exploded perspective view of a non-linear fluid actuator;

[0174] FIG. 12 shows a plan view of the actuator of FIG. 11;

[0175] FIG. 13 shows a schematic cross section of a prior art linear fluid actuator;

[0176] FIG. 14 shows a cross sectional view of a linear fluid actuator having a two-layer inflatable bag in a piston chamber;

[0177] FIG. 15 shows an exploded perspective view of a second embodiment of a rotary fluid actuator;

[0178] FIG. 16 shows a lubricator comprising a fluid actuator as shown in FIG. 5; and

[0179] FIG. 17 shows a flow line valve comprising a fluid actuator as shown in FIG. 15.

DETAILED DESCRIPTION OF THE DRAWINGS

[0180] FIG. 1 shows a typical landing string configured for performing wellbore interventions. The landing string 100 is run into a marine riser 2 in riser tubing 3, which is coupled to a blow-out preventer (BOP) 13 via a flex joint 14. A flow path extends through the riser tubing 3, the landing string 100 and its component parts, and in use provides access to a well for fluids, tools (run on wireline or tubing) or other apparatus/materials as required in an intervention.

[0181] The landing string 100 includes a Sub Sea Test Tree 5, comprising a double barrier valve system.

[0182] The SSTT sits in the landing string above a tubing hanger 7, which is adapted to couple the landing string to the wellhead 9. A tubing hanger running tool 8 may also be provided to run the landing string to the wellhead along the marine riser 2 and couple the tubing hanger 5 to the wellhead 9, as shown in FIG. 2.

[0183] Between the SSTT 5 and the tubing hanger and running tool 7, 8 is a slick joint 11 having a smooth outer surface against which a pipe ram within a BOP 13 can form a seal in case of emergency (as described below with reference to FIG. 2).

[0184] In addition to the double barrier system within the SSTT, further valves may also be provided which sit above the BOP when the landing string has been deployed, such as a retainer valve 15.

[0185] The landing string 100 must be provided with the capacity for emergency disconnection of the retainer valve 15, the riser tubing 3 above the SSTT and any further apparatus above the SSTT, by way of a severable shear joint 17.

[0186] All of the components of the landing string 100 are constrained to fit within the diameter of the riser 2. The components below the shear joint 17 must also fit within the BOP 13, as shown in FIG. 2. Accordingly, a maximum diameter D (in the example shown, 18.5 inches (or around 47 cm) is permitted.

[0187] FIG. 2 shows the landing string 100 fully landed out within the marine BOP 13. The BOP 13 includes a series of pipe rams 18a-c operable sealing around the landing string at selected points (in the example shown, around the SSTT, slick joint and the shear joint), in order to isolate the annulus around the landing string. Fewer or a greater number of shear rams may alternatively be present. In addition, the BOP 13 comprises a shear ram 20, operable to sever the shear joint 17 in case of extreme emergency.

[0188] An additional requirement of the landing string is that the SSTT must be contained within the BOP 13 beneath a shear ram 20. Thus, a limited height along the landing string axis is available within which to fit the SSTT 5.

[0189] The SSTT 5 is shown in further detail in FIG. 3. The SSTT includes a cylindrical housing 22 having a flow path 24 extending therethrough (in the form of a throughbore). The housing wall 26 has a thickness W. An actuator 28 is coupled to the housing beneath each actuator cover 30.

[0190] As can be seen in the cross sectional view of FIG. 4, each actuator is mounted within a recess in the housing wall.

[0191] Each actuator is coupled to a valve, indicated generally as 32, mounted in the housing, via a drive structure 34 (in example shown, in the form of a drive shaft) which extends through the housing wall 26. The housing wall 26 is sealed around the drive shaft 34 by a dynamic packer seal (not shown), so as to isolate the actuator 28 from the fluid environment within the housing 26.

[0192] The efficient packaging of the SSTT 5 enables the housing wall thickness W to be sufficient for the SSTT to be coupled to the adjacent slick joint 11 by a conventional and highly secure flange joint 36. An array of hex nuts 37a is threaded over bolts 37b extending from the housing 22 and through the flange 38 of the slick joint. Accordingly, the use of specialist thin-wall tubing for the housing, and specialist connections to adjacent apparatus in the landing string, is not required.

[0193] In the embodiment shown, the valve is a rotary valve and the SSTT includes rotary actuators, although the invention is not limited to any particular form of valve or actuator. Indeed in alternative embodiments, there may be a different number or arrangement of valves or actuators.

[0194] FIG. 6 shows an exploded view of an actuator 28, which is a rotational fluid actuator (in the present case, hydraulic). The actuator includes an actuator body 40, which is sized to fit within a recess in the wall 26 of the housing 22. In alternative embodiments (not shown) the actuator body forms part of the housing 22 itself, and various parts of the actuator may be defined by the test tree housing 22.

[0195] The drive shaft 34 extends through an aperture 42 of the actuator body and is coupled, via a spline portion 35, to a vane piston 44. The vane piston includes a hub portion 46, having spline fittings 48 around an inside of an aperture through the hub, to enable the vane piston to be coupled to the spline portion 35 of the drive shaft 34.

[0196] The vane piston also includes vanes 50, extending from diametrically opposite sides of the hub 46. The vanes taper from tips 51 to a root portion 52. Each vane 50 is both wider (around the rotation axis A) and thicker (along the rotation axis A) at the root 52 than at the tip 51. The increased width of each vane, such that the vane is general trigonal as viewed along the rotation axis A, improves the mechanical strength of the vane piston.

[0197] The actuator body defines a cavity 54 in its outer face 56 sized to receive the vane piston 44. An actuator cover 30 is bolted (by bolts 31) over the cavity 54, so that the actuator cover and the actuator body together define an internal chamber. In use, the vane piston is operable to rotate around the axis A within the internal chamber, as described below.

[0198] Fluid passages 58 extend through the actuator body 28 to the cavity 54 (and thus the internal chamber). The actuator is also provided with a fluid control arrangement, for regulating the flow of high pressure hydraulic fluid into, and of low pressure hydraulic fluid out of, the internal chamber in use. Fluid flow conduits 60, which extend to the fluid control arrangement, are shown in the figures. Further features of a fluid control arrangement for controlling the operation of a hydraulic actuator are well known in the art and are not described in further detail herein.

[0199] FIGS. 6(a) and (b) show perspective view of the front and rear faces of the actuator 28. As most clearly shown in FIG. 6(a), the outer face 56 of the actuator body 40, and the outer face of the actuator cover 30, both define portions of a cylindrical surface. Thus, the outer surfaces of the actuator lie flush with the outer surface of the test tree housing 22. Accordingly, the actuator is compatible with the largest diameter housing capable of fitting within the BOP. In addition, by maintaining the SSTT within a cylindrical envelope in this way, the SSTT may be run through apparatus such as a lubricator or a rotating table.

[0200] Portions of an inside surface of the actuator cover proximate to the vanes 50 in use (which is not visible in the figures) are provided with a part-spherical profile. As mentioned above, the vanes 50 are tapered, such that their thickness decreases towards the tips 51. The tapered edge portion 53 (shown in FIG. 5) is provided with a curvature which matches the curvature of the inner face of the cover 30. Thus, the radial cross section of the internal cavity matches that of the vane piston, throughout its range of rotation about the axis A. Moreover, the curvature of the vanes 50 and cover 30 ensure that the vane piston may be located as closely as possible to the outer face of the actuator body 28 and the housing 22.

[0201] Operation of the actuator 28 is shown in FIG. 7. FIG. 7 shows that vane piston 44 in the internal chamber 61. The internal chamber is divided by the vane piston into four piston chambers 62a-d. Each piston chamber is defined in part by the actuator body 40 (which may form part of the housing 22), by the vane piston 44 and by the actuator cover 30. Each piston chamber communicates with a fluid passage 58, through which the flow of working hydraulic fluid is controlled via conduits 60 connected to the fluid control arrangement.

[0202] In alternative embodiments, the vane piston 44 may seal against the actuator body 40 and the cover 30. However, the actuator 28 is provided with inflatable bladders 64a-d disposed within each piston chamber. The insides of the bladders communicate with the passages and conduits 58, 60. Accordingly, the piston chambers themselves are required only to contain the bladders, and not to seal against a pressure differential. Moreover, the various internal surfaces of the actuator are not directly exposed to the working fluid.

[0203] In order to move the vane piston 44 anticlockwise, so as to place it in its first position as shown in FIG. 7(b) (corresponding to a first configuration of the actuator as a whole), high pressure working fluid is caused to enter the bladders 64b and 64c in the piston chambers 62b and 62c, respectively. Working fluid within the bladders 64a and 64d, in piston chambers 62a and 62d are exposed to a low pressure fluid sink, such that a pressure differential is created across each vane 50 and working fluid is displaced from the bladders 64a and 64d, as the bladders 64b and 64c are inflated.

[0204] In order to move the vane piston 44 clockwise, so as to place it in its second position as shown in FIG. 7(c) (corresponding to a second configuration of the actuator as a whole), high pressure working fluid is caused to enter the bladders 64a and 64d in the piston chambers 62a and 62d, respectively. By way of the fluid control arrangement, working fluid within the bladders 64b and 64c, in piston chambers 62b and 62c are now exposed to a low pressure fluid sink, such that a pressure differential is created across each vane 50 in the opposite direction and working fluid is displaced from the bladders 64b and 64c, as the bladders 64a and 64d are inflated. Accordingly, the actuator may be selectively controlled between the first and second configurations, so as to open and close the associated valve as required.

[0205] The actuator 28 is provided with a vane piston 44 having diametrically opposed vanes 50. This ensures that the forces applied around the rotation axis are equal; i.e. that only rotational forces are applied to the drive shaft 32, and there is no net force applied normal to the rotation axis A. This arrangement mitigates against binding between the drive shaft and the actuator body 40. Moreover, in use with a rotational valve such as a ball valve, driving of the ball valve member into the valve seat (a known problem in use of balls valves with linear sleeve type actuators) is avoided.

[0206] It should also be noted that the tip-to-tip diameter of the vane piston may exceed the diameter of the rotational valve 32 and so the leverage or torque which may be applied to the valve is not limited by the valve diameter, as is the case for conventional sleeve-actuated rotational valves.

[0207] As can be seen in FIG. 4, the compact rotary actuators 28 are disposed on opposite sides of the housing 22. In addition, provision of the actuators 28 external to the housing, the actuators can be most efficiently spaced around the housing. As can be seen in FIG. 3, the actuators 28 are spaced apart axially along the housing and in addition, the actuators of adjacent valves are staggered circumferentially around the housing. This circumferential offset enables the actuators of adjacent valves to axially overlap, and provides for significant axial space savings.

[0208] As previously mentioned, the provision of an inflatable bladder within each piston chamber obviates the need for a fluid tight dynamic seal between a piston member and an associated internal chamber. In turn, this enables a range of different actuator geometries, which would not otherwise be practicable to manufacture or sufficiently reliable for industrial use.

[0209] FIG. 8 shows an alternative embodiment of an actuator 70. The actuator 70 comprises an actuator body 72 of diamond-shaped cross section. Slideable within a cavity 71 in the body 72 is a piston 74 having a diamond-shaped piston head (not visible in the figure) and a piston shaft 75, which is connectable to external apparatus via a flange 76.

[0210] An inflatable bladder 78 is provided with an aperture so as to fit around the shaft 75 between the piston head and the end 77 of the body 72. A further diamond-shaped inflatable bladder 79 is placed within the cavity 71 on the other side of the piston head. An inside of each of the bladders communicates with a fluid control arrangement via neck portions 78a and 79a and fluid passages 78b and 79b in the body 72. The end of the cavity 71 is covered by an actuator cover (not shown). The piston 74 may be caused to reciprocate within the cylinder by inflating/deflating the bladders 78, 79 generally as described above.

[0211] FIG. 9 shows an exploded view of a still further embodiment of an actuator 80. The actuator 80 comprises an actuator body 82. The actuator body defines an open cavity 83. The actuator 80 also includes a drive structure 84, comprised of a planar drive plate 85 and a piston member 86 extending from the drive plate 85 into the cavity 83.

[0212] The drive plate 83 is provided with slots 90, and threaded bolts 92 pass through the slots and are threaded into threaded apertures in the actuator body 82 (not visible) and to nuts 94 on the underside of the drive plate. The actuator body 82 and the drive structure 84 are thereby secured together, and together define an internal chamber 96 (visible in FIG. 10). The body and the drive structure are moveable in relation to one another along a pathway defined by the slots. The piston member 85 divides the internal aperture into two piston chambers 97, 98.

[0213] An inflatable bladder 88 retained in one piston chamber and an inflatable bladder 89 is retained in the other piston chamber. An inside of each of the bladders communicates with a fluid control arrangement (not shown) via neck portions 88a and 89a and fluid passages 88b and 89b in the body 82.

[0214] The bladders may be inflated and deflated generally as described above, so as to cause the drive structure to move between the first and second configurations shown in FIGS. 10(b) and (c) by inflating/deflating the bladders 88, 89 generally as described above.

[0215] FIG. 11 shows another embodiment of an actuator 200. The actuator 200 is similar to the actuator 80 and like parts are provided with the same numerals, incremented by 200.

[0216] The actuator 200 includes an actuator body 282 formed from two actuator body portions 282A and 282B. Each body portion has an open cavity and so once secured together against opposite sides of the drive plate 283, the body portions and the drive plate together define two internal chambers, one on each side of the drive plate.

[0217] A piston member 285 extends from each side of the drive plate into the respective chambers. Thus, the actuator 200 includes four piston chambers, each enclosing an inflatable bladder 288, 289. The two actuator body portions 282A and 289B are disposed symmetrically around the drive structure 284 and deliver an even force to the drive structure. In addition, the force applied is additive, and proportional to the sum of the surface areas of the piston members 285 within the internal chambers.

[0218] The two body portions 282A and 282B are secured together via threaded bolts passing through the slots 290, which have been omitted from the figure for clarity.

[0219] In contrast to the actuator 80 described above, the slots 292 are curved. The actuator body portions 282A and 282B are provided with the same curvature along their length.

[0220] Thus, in use, the slots and the body portions each in part define a non-linear pathway 299 (shown in FIG. 12) along which the drive structure 284 moves in relation to the actuator body 282. In alternative embodiments, the actuator body may be provided with a series of linear and curved segments and the pathway defined by the guide formations (the slots) may comprise a series of straight and curved portions. Movement between the drive structure and the actuator body of such embodiments along a convoluted pathway of this type may be facilitated by the provision of more than one bladder in each piston chamber.

[0221] A known problem in the use of bladders within the piston chambers of hydraulic actuators is folding and pinching of the bladder against the piston chamber walls under the action of a high working fluid pressure. As shown schematically in FIG. 13, in relation to a conventional linear hydraulic actuator 101, folding of the bladder walls (region 120) prevents even inflation of the bladder. Consequently, an adjacent region 122 may be subject to excessive inflation, leading to blistering or even rupture of the bladder. Moreover, bladders constructed from elastomeric materials may be prone to extrusion.

[0222] FIG. 14 shows an improved bladder 140. The bladder is provided with an outer anti-deformation layer 142 and an inner fluid-tight layer 144. As can be seen in the exploded view, the anti-deformation layer is separate from and so free to move in relation to the inner layer. The anti-deformation layer may optionally be another fluid tight layer, however in the embodiment shown, the anti-deformation layer 142 comprises a Kevlar fabric material. The fabric has an array of apertures which enable fluid within the piston chamber to enter between the layers and provided lubrication. Moreover, the Kevlar layer (or indeed another type of outer anti-deformation layer, such as a metal fabric, or a perforated or fluid-tight outer later) resists against extrusion of the bag. The Kevlar layer is flexible, and resists stretching. Thus, in the event that the bladder does become folded, the anti-deformation layer 142 resists against blistering of the inner fluid-tight layer 144.

[0223] Another actuator 328 is shown in FIG. 15. Parts in common with the actuator 28 are provided with the same reference numerals, incremented by 300. The actuator 328 includes a cylindrical actuator body 340 having a flat outer face 356. The actuator cover 330 is also flat, so as to lie flush with the outer face 356 when installed.

[0224] The drive shaft 334 has a longer spine portion 335 than the drive shaft 34. The vane piston 344 is also thicker. Thus, the faces 345 which in part define respective piston chambers have a greater surface area than the equivalent faces of the vane piston 44. Thus, for a given pressure differential, greater rotational forces are applied by the vane piston 344.

[0225] As mentioned above, the present invention may also be applied to other apparatus. FIG. 16 shows a lubricator valve 400, comprising a cylindrical housing 422 connected via flange connectors 436 to tubular 401. The cylindrical housing 422 defined a flow path having a valve therein (not shown) and a pair of rotary fluid actuators 28 are coupled to the housing and operable to open and close the valve as described above. FIG. 17 shows a flow line valve 440, comprising an actuator 328 coupled to a flow line housing 442.