WO2008070245A2

WO2008070245A2 - Subsea actuation systems and methods

Info

Publication number: WO2008070245A2
Application number: PCT/US2007/079001
Authority: WO
Inventors: Donald Wayne Allen; Dean Leroy Henning
Original assignee: Shell Oil Company; Shell Internationale Research Maatschappij B.V.
Priority date: 2006-09-22
Filing date: 2007-09-20
Publication date: 2008-06-12
Also published as: GB0902197D0; NO20091568L; GB2456072A; BRPI0716109A2; MX2009002734A; WO2008070245A3

Abstract

There is disclosed a system comprising a cylinder; a piston moveable within the cylinder; an arm connected to the piston; and a mechanism for resisting movement of the piston until a predetermined pressure acts on the piston. In some embodiments, the mechanism for resisting movement comprises a shear pin connected to the arm.

Description

SUBSEA ACTUATION SYSTEMS AND METHODS

Field of Invention: The present disclosure relates to subsea actuation systems and methods. In particular to systems and methods activated at a predetermined water depth. Background:

Structural elements can be installed at sea from a floating vessel using a J-lay configuration where the structural element is held vertically on the vessel and dropped vertically into the water and then when it reaches the bottom of the body of water, it lays horizontal, or alternatively structural elements can be installed in a S-lay configuration where the structural element is held horizontally on the vessel, drops to vertical through the body of water, and then rests on the bottom of the body of water in a horizontal configuration. Other configurations for installing a structural element from a vessel in a body of water are also known.

Referring now to Figure 1, system 100 for installing structural element 114 on bottom 116 of body of water 112 is illustrated. System 100 includes vessel 110 with tensioner 120 and stinger 118. Tensioner 120 holds structural element 114 in a horizontal configuration as it enters water, and then structural element 114 rolls down stinger 118, then drops to a vertical configuration, and then back to a horizontal configuration as it lays on bottom 116. Tensioner 120 and vessel 110 have a sufficient capacity to support structural element 114 as it is being installed.

Currents in body of water 112 may cause vortexes to shed from the sides of structural element 114. When these types of structural elements, such as a cylinder, experience a current in a flowing fluid environment, it is possible for the structural element to experience vortex-induced vibrations (VIV). These vibrations may be caused by oscillating dynamic forces on the surface which can cause substantial vibrations of the structural element, especially if the forcing frequency is at or near a structural natural frequency. Some devices used to reduce vibrations caused by vortex shedding from sub-sea structural elements operate by modifying the boundary layer of the flow around the structural element to prevent the correlation of vortex shedding along the length of the structural element. Examples of such devices include sleeve-like devices such as helical strake elements, shrouds, fairings and substantially cylindrical sleeves. Currently available strake elements and fairings cover part or all the circumference of a cylindrical element or may be clamshell shaped to be installed about the circumference.

Some VIV and/or drag reduction devices can be installed on risers and similar structural elements before those structural elements may be deployed underwater. Deploying structural elements may damage the VIV and/or drag reduction devices by the installation, for example by the stinger or rollers during an S-lay installation. Alternatively, VIV and/or drag reduction devices can be installed on structural elements after those structural elements have been deployed underwater. When installing a structural element in an S-lay configuration, the structural element may travel over a stinger and encounter one or more rollers on the stinger. A pre- installed VIV and/or drag reduction devices may be damaged if it passes over the stinger. In addition, holding onto a structural element with a tensioner may damage VIV and/or drag reduction devices. One alternative is to install the devices on the structural element after it passes over the rollers and the stinger.

When installing a structural element from a surface vessel to a subsea location, it may be desirable to activate or deactivate a mechanism at a predetermined depth. This is normally done with a tether, wire, a remotely operated vehicle, or a diver.

Copending U.S. Patent Application 10/848,547, published as 2005/0254903, and having attorney docket number TH2463 discloses methods and apparatus for the installation of VIV suppression during the S-Lay installation of a subsea pipeline. A locking member will be interposed between a pipe and a fairing rotatably mounted on the pipe, sufficient to bias the fairing against rotating. Upon marine application, the locking member will degrade, thereby releasing the fairing. U.S. Patent Application 10/848,547 is hereby incorporated by reference in its entirety.

There is a need in the art for an improved apparatus and method for installing VIV and/or drag reduction devices. There is another need in the art of apparatus for and new and improved methods of installing VIV and/or drag reduction devices in a flowing fluid environment. There is another need in the art for new and improved systems and methods of activating and/or deactivating a mechanism at a predetermined depth. There is another need in the art of apparatus for and new and improved methods of installing VIV and/or drag reduction devices which does not require subsea intervention by a diver or ROV. These and other needs of the present disclosure will become apparent to those of skill in the art upon review of this specification, including its drawings and claims. Summary of the Invention

One aspect of the invention provides a system comprising a cylinder; a piston moveable within the cylinder; an arm connected to the piston; and a mechanism for resisting movement of the piston until a predetermined pressure acts on the piston. In some embodiments, the mechanism for resisting movement comprises a shear pin connected to the arm.

Another aspect of the invention provides a method comprising installing a moveable piston within a cylinder; connecting an arm to the piston; installing a mechanism for resisting movement of the piston until a predetermined pressure acts on the piston within the cylinder; mounting the cylinder to a structural element; and lowering the structural element to a predetermined depth to move the piston, which moves the arm, which actuates a subsea system. Advantages of the invention may include one or more of the following: an improved apparatus and method for installing VIV and/or drag reduction devices; an apparatus for and new and improved methods of installing VIV and/or drag reduction devices in a flowing fluid environment; new and improved systems and methods of activating and/or deactivating a mechanism at a predetermined depth; and new and improved methods of installing VIV and/or drag reduction devices which does not require subsea intervention by a diver or ROV. Brief Description of the Drawings Figure 1 illustrates a system for installing a structural element in a body of water in an S-lay configuration.

Figure 2 illustrates a subsea actuation system.

Figure 3 illustrates a subsea actuation system unlocking a VIV and/or drag reduction device. Figure 4 illustrates a subsea actuation system engaging a valve.

Detailed Description of the Invention

In one embodiment, there is disclosed a system comprising a cylinder; a piston moveable within the cylinder; an arm connected to the piston; and a mechanism for resisting movement of the piston until a predetermined pressure acts on the piston. In some embodiments, the mechanism for resisting movement comprises a shear pin connected to the arm. In some embodiments, the mechanism for resisting movement comprises a biasing means within the cylinder, for example a spring, compressed gas, and/or another compressed fluid. In some embodiments, the piston separates the cylinder into a low- pressure region and an ambient pressure region. In some embodiments, the cylinder comprises at least one opening between the ambient pressure region and an area outside the cylinder. In some embodiments, the system also includes a structural element, the cylinder connected to the structural element. In some embodiments, the structural element is selected from the group consisting of a shell, a collar, an oil flowline, a pipeline, a drilling riser, a production riser, a steel tubular, import and export risers, subsea pipelines, tendons for tension leg platforms, legs for traditional fixed and for compliant platforms, space- frame members for platforms, cables, umbilicals, mooring elements for deepwater platforms, hull structures for tension leg platforms and for spar type structures, and column structures for tension leg platforms and for spar type structures. In some embodiments, the system also includes at least one vortex induced vibration (VIV) and/or drag reduction device about the structural element. In some embodiments, the VIV and/or drag reduction devices are selected from strakes and/or fairings. In some embodiments, the arm is adapted to lock the VIV and/or drag reduction device in a preferred orientation until the predetermined pressure acts on the piston. In some embodiments, the system also includes a valve, the arm adapted to actuate the valve when the predetermined pressure acts on the piston.

In one embodiment, there is disclosed a method comprising installing a moveable piston within a cylinder; connecting an arm to the piston; installing a mechanism for resisting movement of the piston until a predetermined pressure acts on the piston within the cylinder; mounting the cylinder to a structural element; and lowering the structural element to a predetermined depth to move the piston, which moves the arm, which actuates a subsea system. In some embodiments, the structural element is selected from the group consisting of a shell, a collar, an oil flowline, a pipeline, a drilling riser, a production riser, a steel tubular, import and export risers, subsea pipelines, tendons for tension leg platforms, legs for traditional fixed and for compliant platforms, space-frame members for platforms, cables, umbilicals, mooring elements for deepwater platforms, hull structures for tension leg platforms and for spar type structures, and column structures for tension leg platforms and for spar type structures. In some embodiments, the method also includes installing at least one VIV and/or drag reduction device about the structural element. In some embodiments, the VIV and/or drag reduction device is selected from strakes and fairings. In some embodiments, the method also includes locking the at least one VIV and/or drag reduction device in a preferred orientation with the arm. In some embodiments, the method also includes unlocking the at least one VIV and/or drag reduction device by moving the piston and the arm, by lowering the structural element to a predetermined depth. In some embodiments, the method also includes connecting a valve to the structural element and actuating the valve with the arm, by lowering the structural element to a predetermined depth.

Referring now to Figure 2, in one embodiment of the invention, system 200 is illustrated. System 200 includes cylinder 202 with openings 204, which allow ambient pressure into cylinder 202. Within cylinder 202 is piston 206, which separates cylinder 202 into low-pressure region 208, and ambient pressure region connected to openings 204. Seals 207 may be provided between piston 206 and cylinder 202. Biasing mechanism 210, such as a spring or rubber band, may be connected to piston 206, to pull piston 206 in the direction of arrows. Arm 212 is connected to piston 206. Shear pin 214 is connected to arm 212 and stationary block 216.

In operation, as system is lowered to increasing subsea depths, ambient pressure increases and exerts a force on piston 206 in the direction of arrows. Shear pin 214 resists this force and the force exerted by biasing mechanism 210 until a predetermined depth when the forces break shear pin 214, and piston 206 and arm 212 move in the direction of arrows. The movement of arm 212 may be used to activate and/or deactivate one or more mechanisms at the predetermined depth. In some embodiments, system 200 may operate without the use of shear pin 214.

Biasing mechanism 210 may be a spring, a compressed gas, or another compressible fluid which resists the force exerted by the ambient pressure. At a predetermined depth, force on piston 206 overcomes force exerted by biasing mechanism 210, and piston 206 and arm 212 move in the direction of arrows. The movement of arm 212 may be used to activate and/or deactivate one or more mechanisms at the predetermined depth.

Referring now to Figure 3, in some embodiments of the invention, system 300 is illustrated. System 300 includes cylinder 302 with openings 304, which allow ambient pressure into cylinder 302. Cylinder 302 is connected to subsea structure 320, which may be lowered into a body of water. Within cylinder 302 is piston 306, which separates cylinder 302 into low-pressure region 308, and ambient pressure region connected to openings 304. Seals 307 may be provided between piston 306 and cylinder 302. Biasing mechanism 310, such as a spring or rubber band, may be connected to piston 306, to pull piston 306 in the direction of arrows. Arm 312 is connected to piston 306. Shear pin 314 is connected to arm 312 and stationary block 316. Stationary block 316 is connected to subsea structure 320. Vortex induced suppression device 318, such as a strake or a fairing, is about subsea structure 320. Arm 312 has locked vortex induced suppression device 318 in the position shown. In operation, as system is lowered to increasing subsea depths, ambient pressure increases and exerts a force on piston 306 in the direction of arrows. Shear pin 314 resists this force and the force exerted by biasing mechanism 310 until a predetermined depth when the forces break shear pin 314, and piston 306 and arm 312 move in the direction of arrows. The movement of arm 312 may be used to unlock vortex induced suppression device 318 at the predetermined depth, so that vortex induced suppression device 318 may rotate about subsea structure 320.

In some embodiments, system 300 may operate without the use of shear pin 314. Biasing mechanism 310 may be a spring, a compressed gas, or another compressible fluid which resists the force exerted by the ambient pressure. At a predetermined depth, force on piston 306 overcomes force exerted by biasing mechanism 310, and piston 306 and arm 312 move in the direction of arrows. The movement of arm 312 may be used to activate and/or deactivate one or more mechanisms at the predetermined depth.

In some embodiments, system 300 may be used to S-lay subsea structure 320 with vortex induced suppression device 318 mounted in a locked position by arm 312 away from the stinger and/or ramp and/or rollers. At the predetermined depth, arm 312 may be retracted by piston 306 to unlock vortex induced suppression device 318, so that vortex induced suppression device 318 can rotate about subsea structure 320.

Referring now to Figure 4, in some embodiments of the invention, system 400 is illustrated. System 400 includes cylinder 402 with openings 404, which allow ambient pressure into cylinder 402. Cylinder 402 is connected to subsea structure 420, which may be lowered into a body of water. Within cylinder 402 is piston 406, which separates cylinder 402 into low-pressure region 408, and ambient pressure region connected to openings 404. Seals 407 may be provided between piston 406 and cylinder 402. Biasing mechanism 410, such as a spring or rubber band, may be connected to piston 406, to pull piston 406 in the direction of arrows. Arm 412 is connected to piston 406. Shear pin 414 is connected to arm 412 and stationary block 416. Stationary block 416 is connected to subsea structure 420. Valve 418 is connected to subsea structure 420. Arm 412 may be used to actuate valve from an open to a closed or from a closed to an open position.

In operation, as system is lowered to increasing subsea depths, ambient pressure increases and exerts a force on piston 406 in the direction of arrows. Shear pin 414 resists this force and the force exerted by biasing mechanism 410 until a predetermined depth when the forces break shear pin 414, and piston 406 and arm 412 move in the direction of arrows. The movement of arm 412 may be used to actuate valve from an open to a closed or from a closed to an open position at the predetermined depth, so that a fluid or gas may begin to flow or cease flowing at the predetermined depth.

In some embodiments, system 400 may operate without the use of shear pin 414. Biasing mechanism 410 may be a spring, a compressed gas, or another compressible fluid which resists the force exerted by the ambient pressure. At a predetermined depth, force on piston 406 overcomes force exerted by biasing mechanism 410, and piston 406 and arm 412 move in the direction of arrows. The movement of arm 412 may be used to activate and/or deactivate one or more mechanisms at the predetermined depth.

In some embodiments of the invention, VIV and/or drag reduction devices may be mounted around a structural element according to the method disclosed in U.S. Patent No. 6,695,539, which is herein incorporated by reference in its entirety.

In some embodiments of the invention, VIV and/or drag reduction devices may be installed about a structural element according to the method disclosed in U.S. Patent No. 6,561,734, which is herein incorporated by reference in its entirety. In some embodiments of the invention, VIV and/or drag reduction devices may be installed about a structural element according to the method disclosed in U.S. Patent Application Publication No. 2003/0213113, which is herein incorporated by reference in its entirety.

In some embodiments of the invention, the outside diameter of a structural element to which VIV and/or drag reduction devices can be attached may be from about 10 to about 500 cm, for example from about 20 to about 250 cm, or from about 25 to about 100 cm. In some embodiments of the invention, the height of VIV and/or drag reduction devices may be from about 5% to about 50% of the structural element's outside diameter. In some embodiments of the invention, the height of VIV and/or drag reduction devices may be from about 5 to about 50 cm, measured from the outside surface of the structural element to the outside surface of the VIV and/or drag reduction device.

In some embodiments of the invention, the structural element may be cylindrical, or have an elliptical, oval, or polygonal cross-section, for example a square, pentagon, hexagon, or octagon.

In some embodiments, portions of structural element 320 or 420 may be lowered onto bottom 116 of water 112. In some embodiments, water 112 has a depth of at least about 1000 meters, at least about 2000 meters, at least about 3000 meters, or at least about 4000 meters. In some embodiments, water 112 has a depth up to about 10,000 meters.

In some embodiments of the invention, structural element 320 or 420 may be a pipeline, a crude oil flowline, a mooring line, a riser, a tubular, or any other structural element installed in a body of water. In some embodiments, structural element 320 or 420 may have a diameter from about 0.1 to about 5 meters, and a length from about 10 to about 200 kilometers (km). In some embodiments, structural element 320 or 420 may have a length to diameter ratio from about 100 to about 100,000. In some embodiments, structural element 320 or 420 may be composed from about 50 to about 30,000 tubular sections, each with a diameter from about 10 cm to about 60 cm and a length from about 5 m to about 50 m, and a wall thickness from about 0.5 cm to about 5 cm. Those of skill in the art will appreciate that many modifications and variations are possible in terms of the disclosed embodiments, configurations, materials and methods without departing from their spirit and scope. Accordingly, the scope of the claims appended hereafter and their functional equivalents should not be limited by particular embodiments described and illustrated herein, as these are merely exemplary in nature.

Claims

C L A I M S

1. A system comprising: a cylinder; a piston moveable within the cylinder; an arm connected to the piston; and a mechanism for resisting movement of the piston until a predetermined pressure acts on the piston.

2. The system of claim 1 , wherein the mechanism for resisting movement comprises a shear pin connected to the arm.

3. The system of one or more of claims 1-2, wherein the mechanism for resisting movement comprises a biasing means within the cylinder, for example a spring, compressed gas, and/or another compressed fluid.

4. The system of one or more of claims 1-3, wherein the piston separates the cylinder into a low-pressure region and an ambient pressure region.

5. The system of claim 4, wherein the cylinder comprises at least one opening between the ambient pressure region and an area outside the cylinder.

6. The system of one or more of claims 1-5, further comprising a structural element, the cylinder connected to the structural element.

7. The system of claim 6, wherein the structural element is selected from the group consisting of a shell, a collar, an oil flowline, a pipeline, a drilling riser, a production riser, a steel tubular, import and export risers, subsea pipelines, tendons for tension leg platforms, legs for traditional fixed and for compliant platforms, space-frame members for platforms, cables, umbilicals, mooring elements for deepwater platforms, hull structures for tension leg platforms and for spar type structures, and column structures for tension leg platforms and for spar type structures.

8. The system of one or more of claims 6-7, further comprising at least one vortex induced vibration (VIV) and/or drag reduction device about the structural element.

9. The system of one or more of claims 6-8, wherein the VIV and/or drag reduction devices are selected from strakes and/or fairings.

10. The system of one or more of claims 6-8, wherein the arm is adapted to lock the VIV and/or drag reduction device in a preferred orientation until the predetermined pressure acts on the piston.

11. The system of one or more of claims 1-10, further comprising a valve, the arm adapted to actuate the valve when the predetermined pressure acts on the piston.

12. The system of one or more of claims 1-11, wherein the predetermined pressure comprises a predetermined hydrostatic pressure from fluid surrounding the piston.

13. A method of actuating a subsea system, comprising: installing a moveable piston within a cylinder; connecting an arm to the piston; installing a mechanism for resisting movement of the piston until a predetermined pressure acts on the piston within the cylinder; mounting the cylinder to a structural element; and lowering the structural element to a predetermined depth to move the piston, which moves the arm, which actuates a subsea system.

14. The method of claim 13, wherein the structural element is selected from the group consisting of a shell, a collar, an oil flowline, a pipeline, a drilling riser, a production riser, a steel tubular, import and export risers, subsea pipelines, tendons for tension leg platforms, legs for traditional fixed and for compliant platforms, space-frame members for platforms, cables, umbilicals, mooring elements for deepwater platforms, hull structures for tension leg platforms and for spar type structures, and column structures for tension leg platforms and for spar type structures.

15. The method of one or more of claims 13-14, further comprising installing at least one VIV and/or drag reduction device about the structural element.

16. The method of claim 15, wherein the VIV and/or drag reduction device is selected from strakes and fairings.

17. The method of one or more of claims 15-16, further comprising locking the at least one VIV and/or drag reduction device in a preferred orientation with the arm.

18. The method of claim 17, further comprising unlocking the at least one VIV and/or drag reduction device by moving the piston and the arm, by lowering the structural element to a predetermined depth.

19. The method of one or more of claims 13-18, further comprising connecting a valve to the structural element and actuating the valve with the arm, by lowering the structural element to a predetermined depth.