WO2001012948A1

WO2001012948A1 - Methods and apparatus for the emergency actuation of control systems

Info

Publication number: WO2001012948A1
Application number: PCT/GB2000/003022
Authority: WO
Inventors: Torquil Macleod Crichton; Robert White
Original assignee: Coflexip Stena Offshore Limited; Coflexip
Priority date: 1999-08-13
Filing date: 2000-08-03
Publication date: 2001-02-22
Also published as: AU6456300A; NO20020712D0; NO20020712L; GB9919024D0; EP1203139A1

Abstract

The invention relates to the emergency actuation of control systems for the shut down and/or isolation of a fluid circuit containing at least one flexible pipe (42, 44, 46). The flexible pipe (42, 44, 46) being connected to at least one actuating means provided by a system component associated with the operation of the pipe such that the system component is actuated in response to movement of the pipe arising from failure of, or damage to the pipe. The system component may consist of a valve (48) for venting pressure from a hydraulic circuit (16) used in offshore installations and actuation of the valve (48) may be provided by a lever (102A, 102B) connected between the valve (48) and one of the flexible pipes (42, 44, 46) by a lanyard (24).

Description

"Methods and Apparatus for the Emergency Actuation of Control Systems"

The present invention relates to methods and apparatus for use in the emergency actuation of control systems for the shut-down and/or isolation of fluid circuits. More particularly, the invention relates to systems which enable valves to be actuated automatically in the event of a failure in a flexible conduit forming part of a fluid production or control circuit. The invention finds particular application in offshore installations involved in the extraction of hydrocarbons, including subsea hydrocarbon production facilities and other offshore production and/or storage facilities.

A typical example of a subsea hydrocarbon production facility is illustrated in Fig. 1 and comprises a number of satellite wellheads 2 connected to a local template 4. The template 4 is in turn connected to a number of inter-field flowline manifolds 6. The wellheads 2 are connected to the template 4 and the template 4 is connected to the inter-field flowline manifolds 6 by means of a variety of fluid conduits including production lines for the transport of production fluids and hydraulic control lines, and electrical lines. As shown in Fig. 1, each of the wellheads 2 is connected to the template by flexible pipes 42, 44 and 46, comprising production, test and gas lines respectively. The inter-field flowline manifolds 6 are also connected to the template by respective flexible pipes 8, 10, 12, again comprising production, test and gas lines. Each of the inter- field flowline manifolds 6 is associated with an inter- field flowline 7.

The facility will generally be powered by a main hydraulic umbilical 14 and a main electrical umbilical (not shown) connected to the template 4. The template 4 will generally include a hydraulic power distribution system ("ring main") 16 comprising two high pressure lines and two low pressure lines by means of which hydraulic power is distributed to various subsea modules including the satellite wellheads 2 and inter- field flowline manifolds 6, via suitable hydraulic power lines 60.

The invention is also applicable in other offshore applications, including situations where flexible jumper conduits connect marine risers to fixed platform pipework, where flexible conduits are used for fluid transfer between respective vessels, where flexible conduits convey pressurised hydraulic control fluid between an energy source at the surface and an operating system on the seabed, and where lengths of flexible conduit are used to tie in subsea satellite production facilities to rigid inter-field flowlines. In the event of a failure occurring in a flexible fluid conduit or in a hydraulic umbilical or the like, it is necessary to shut down the hydraulic pressure in the affected conduit and/or in associated conduits to prevent the flow of hydrocarbon products and/or other contaminants into the environment .

Existing systems for effecting the emergency shutdown of fluid conduits in such circumstances commonly include the use of suitable instrumentation such as pressure sensors, supplemented in some cases by temperature sensors. Such sensors monitor the relevant conduits and feed information back to a monitoring/control system. Such systems generally require manual action in response to information received from the sensors in order to instigate a shut- down or isolation of relevant conduits.

Instrumentation based systems of this type have a number of disadvantages, including: - the time lag between an abnormal condition being recorded and interpreted and action being taken in response thereto; - degradation of the system capability over time and resultant failure of sensors, communication lines etc.; - the fact that the use of pressure and temperature sensors to identify abnormal conditions is reliant on other aspects of the control system operating correc ly; - high development, installation and maintenance costs associated with leak-detection systems, particularly for subsea applications; - the complexity of such systems makes them liable to erroneous alarm signals, so that it is uncommon for such systems to be configured to effect automatic shut- downs, and unidentified or uncorrected system bugs often lead to alarm signals being disabled so that the operation of the system is compromised.

In the case of hydraulic umbilical conduits, it is also known to employ guillotine devices. Such devices completely sever all of the relevant control lines and the hydraulic umbilical in the event of a conduit failure being detected. Guillotines are difficult to retro-fit to existing systems and have additional disadvantages, including: - "one shot" operation; - high cost of repairing damage resulting from operation of the guillotine; - severing of lines results in conduit contents being released into the environment and exposes internal components to the ingress of seawater; - high manufacturing and installation costs; - the size and cost of the devices is directly related to the cross sectional size of the umbilical; - after use, all control and production lines damaged by operation of the device have to be repaired before production can resume.

It is an object of the present invention to provide improved systems for shutting down and/or isolating fluid conduits in which the aforementioned disadvantages of existing systems are obviated or mitigated. /12948

In accordance with a first aspect of the present invention, there is provided an arrangement in which at least one flexible pipe is connected to at least one actuating means of at least one system component associated with the operation of the pipe in such a manner that said system component is actuated in response to movement of the pipe arising from failure of or damage to the pipe .

In accordance with a second aspect of the invention, there is provided a kit of parts comprising at least one system component associated with the operation of at least one flexible pipe, at least one actuating means for actuating said system component, and means for connecting said actuating means to a flexible pipe in such a manner that said system component is actuated in response to movement of the pipe arising from failure of or damage to the pipe.

In accordance with a third aspect of the invention, there is provided a method of actuating at least one system component associated with the operation of at least one flexible pipe, wherein at least one actuating means is provided for actuating said system component, comprising connecting said actuating means to a flexible pipe in such a manner that said system component is actuated in response to movement of the pipe arising from failure of or damage to the pipe.

Preferably, said at least one system component comprises at least one valve. Preferably, said at least one valve comprises a vent valve for venting pressure from a hydraulic supply circuit.

In one application, the invention is applied to a subsea hydrocarbon production installation including a subsea template having a hydraulic power supply system and at least one associated installation connected to said template by at least one flexible pipe, and further including control means powered by the hydraulic power supply of the template, wherein said at least one vent valve is adapted to vent pressure supplied by said hydraulic power supply to said control means.

Said associated installation (s) may comprise at least one wellhead and/or at least one flowline manifold. Said control means may comprise at least one control module associated with at least one of said template, said wellhead(s) and said flowline manifold(s).

One or more flexible pipes may be connected to one or more actuating means.

Preferably, the connecting means is arranged to effect substantially simultaneous actuation of a plurality of valves in a vent valve assembly for venting pressure from a plurality of hydraulic supply lines connected to a hydraulic ring main of said template. Preferably, said actuating means of said at least one valve comprises a lever and the means connecting said pipeline to said lever is adapted to transfer force arising from movement of said flexible pipe directly to said lever.

Preferably, the means connecting said pipeline to said actuating means includes a flexible lanyard.

Preferably, the means connecting said pipeline to said actuating means is connected to said pipe at a location adjacent to a fluid coupling between an end of said flexible pipe and associated rigid pipework.

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

Fig. 1 is a schematic plan view of a typical example of a subsea hydrocarbon production facility to which the present invention may be applied; and

Fig. 2 is a schematic illustration of one embodiment exemplifying the application of the present invention to a subsea installation such as that illustrated in Fig. 1.

Referring now to the drawings, Fig. 2 illustrates one example of an application of the invention in connection with flexible pipes interconnecting a subsea template structure and a wellhead (or "Christmas tree") structure of the type illustrated in Fig. 1. In this schematic illustration, the template structure 4 is to the left of a first dashed and dotted line 38 and the wellhead 2 structure is to the right of a second dashed and dotted line 40. The template 4 is connected to the wellhead 2 by three flexible pipes 42, 44 and 46 (typically comprising a production line, a gas line and a test line as discussed above) .

The ends of each flexible pipe 42, 44 and 46 are connected by a suitable coupling to rigid pipework of the template 4 and wellhead 2 respectively.

A first vent valve assembly 48 is located on the template 4 and a second vent valve assembly 56 is located on the wellhead 2. When actuated, the vent valve assemblies 48 and 56 vent hydraulic pressure supplied from the ring main 16.

The vent valve assemblies 48 and 56 each comprises a block of four fluid lines 100, corresponding to the four conduits (two low pressure and two high pressure) of the hydraulic ring-main 16, each of which includes first and second normally-closed valves 100A and 100B. The use of two series-connected valves in each line 100 is conventional practice to ensure in-service leak integrity. The valves themselves may be of conventional type. Each of the valves 100A, 100B is operated by a lever 102A, 102B. For the purposes of the present embodiment of the invention, it is desirable that the valves 100A, 100B are of a type which are actuated by lever with a relatively short throw, suitably of about 90°. The levers of each pair of valves 100A/100B in each of the lines 100 are ganged together by first link members 104, pivotally connected to the ends of each pair of levers 102A/102B. In this example, the first link members 104 are in turn ganged together by a second link member 106, connected to lowermost ends of the first link members 104. In accordance with the invention, lanyards 24 are connected to the second link member 106. Accordingly, if any one of the lanyards 24 are pulled with sufficient force, the force is transferred via the link members 106 and 104 to the levers 102A/102B so as to open all of the valves 100A/100B simultaneously.

The lowermost ends of the fluid conduits 100 are closed by blow-out plugs 34, and the upper ends of the conduits 100 are provided with suitable fittings 52 allowing the assembly to be connected to other system components depending on the particular application of the invention.

The second link member 106 of the valve assembly 48 on the template 4 is connected to each of the flexible pipes 42, 44 and 46 by the lanyards 24, each of which has one end connected to the link member 106 and the other end connected to an anchoring collar 50 secured to the respective pipe 42, 44 or 46 at a point adjacent the coupling which connects the pipe 42, 44 or 46 to the rigid pipework of the template. The upper ends of the fluid conduits 100 of the assembly 48 are fitted with T-pieces 52. One leg of each of the T-pieces 52 is connected to a gauge on a gauge panel 54 on the template. The gauges correspond to the high and low pressure lines of the hydraulic ring-main 16.

The second link member 106 of the valve assembly 56 on the wellhead ("tree") 2 is again connected to each of the flexible pipes 42, 44 and 46 by lanyards 24, each of which has one end connected to the link member 106 and the other end connected to an anchoring collar 50 secured to the respective pipe 42, 44 and 46 at a point adjacent the coupling which connects the pipe 42, 44 and 46 to the rigid pipework of the tree structure 2. The upper ends of the fluid conduits 100 of the assembly 56 are again fitted with T-pieces 52. One leg of each of the T-pieces 52 is connected to one leg of respective further T-pieces 58, fitted to hydraulic supply inputs of a subsea control module 59 of the tree structure 2. The remaining legs of the further T- pieces 58 are connected to low and high pressure hydraulic supply lines 60 from the template ring main 16.

Finally, the remaining legs of the T-pieces 52 on the template and wellhead valve assemblies 48 and 56 are interconnected with one another. That is, the corresponding high and low pressure lines of the valve assemblies 48 and 56 are connected to one another, to the corresponding gauges of the gauge panel 54, and to the corresponding hydraulic supply inputs of the subsea control module 59. O 01/12948

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If a sufficient tensile force is applied to any one of the lanyards 24, the valves 100A/100B of the valve assembly 48 or 56 to which the relevant lanyard 24 is connected will be actuated (opened) . The hydraulic pressure from the hydraulic ring main 16 will then have a path via the various T-pieces 52 and 58 and the fluid conduits 100 of the valve assembly 48 or 56 and will blow out the blow-out plugs 34 at the lower ends of the conduits 100. The hydraulic pressure from the ring main 16 will thus be vented through the valve assembly. Thus, pressure is vented from the entire hydraulic network, resulting in shut-down of the subsea facility. Once the failure which led to the shutdown has been identified, the damaged module may be isolated and partial production may be restarted while the damaged module is repaired.

Since the lanyards 24 are connected to the flexible pipes 42, 44, 46, the valve assembly 48 or 56 will be actuated by any movement of any one of the pipes which applies a sufficient tensile force to the lanyards 24. Such movement may be caused by failure of one of the pipes which, due to its flexible nature and the fluid pressure therein, will tend to flail. Any failure of the pipes is liable to occur at or adjacent to the coupling of the pipe to the rigid pipework of either the template or the wellhead structure. Accordingly, the lanyard anchoring collars 50 are secured to the pipes at locations where failure of the pipes is most likely to result in the required tensile force being applied to the lanyard 24 connected thereto. Owing to the flexible nature of the lanyards 24, the valve assemblies 48 and 56 can be actuated in response to axial or lateral movement of the pipes . Axial movement is likely to result from spontaneous failure of a pipe. Lateral movement is likely to occur in response to an external force applied to a pipe, e.g. as a result of the pipe being snagged by fishing gear.

In the above described embodiment, the invention is applied to the wellheads 2 of the subsea facility of Fig. 1; i.e. the lanyards 24 of Fig. 2 are connected between the valve assemblies 48 and 56 and the adjacent ends of the flexible pipes 42, 44 and 46. In the same subsea facility, the invention could be applied in a similar manner to the flexible pipes 8, 10 and 12 interconnecting the template 4 and the inter-field flowline manifolds 6.

The invention can similarly be applied in any situation where a flexible pipe is liable to fail and can be connected to an actuator of relevant control/vent valves.

In the examples described and illustrated herein, the flexible pipes are connected to the relevant valve (s) by means of a flexible lanyard and rigid link members. The use of a flexible lanyard is preferred since this allows the valve (s) to be actuated in response to movement of the pipe in any one of a variety of directions. Other types of linkage might be employed dependent on the particular circumstances. Also, in the present examples, the mechanical force arising from O 01/12948

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movement of the pipe is applied directly to effect movement of the valve actuator (s). Alternatively, this force could be employed to activate, for example, a motorised valve actuator. It will also be understood that the invention may be employed to actuate individual valves and/or groups of valves and is not limited to valve assemblies of the type employed in the examples .

It should be understood that the connection of the relevant valve assemblies to the template gauge panel in the preceding example is desirable for convenience in servicing the associated hydraulic systems but is not essential to the main functionality of the invention.

Advantages of the present invention in comparison with prior art systems as discussed above include: - intrinsic simplicity; - speed and nature of response; - resettable using conventional ROV (remotely operated vehicle) technology, requiring no special tooling; - operation of the invention does not damage conduits or other system components and in many cases partial production can be restarted quickly once the failure which resulted in actuation of the system has been identified and isolated; - accidental actuation of the system has no serious or long term consequences; - easily retro-fitted as an enhancement to existing installations; O 01/12948

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- the size of the system components is related to the size of hydraulic system pipework and not to the size of the associated production pipework.

Whilst the described embodiments of the invention relate to fluid control systems, it will be understood that the invention could also be applied to the emergency shutdown or operation of electrical systems, with the lanyard (s) having one end connected to a flexible pipe and the other end connected to an actuating member of an electrical circuit breaker or the like. The invention could also be adapted to operate simultaneously on hydraulic and electrical systems.

Improvements and modifications may be incorporated without departing from the scope of the invention.

Claims

1. An arrangement in which at least one flexible pipe is connected to at least one actuating means of at least one system component associated with the operation of the pipe in such a manner that said system component is actuated in response to movement of the pipe arising from failure of or damage to the pipe.

2. A kit of parts comprising at least one system component associated with the operation of at least one flexible pipe, at least one actuating means for actuating said system component, and means for connecting said actuating means to a flexible pipe in such a manner that said system component is actuated in response to movement of the pipe arising from failure of or damage to the pipe.

3. A method of actuating at least one system component associated with the operation of at least one flexible pipe, wherein at least one actuating means is provided for actuating said system component, comprising connecting said actuating means to a flexible pipe in such a manner that said system component is actuated in response to movement of the pipe arising from failure of or damage to the pipe.

4. The invention of any one of Claims 1 to 3 , wherein said at least one system component comprises at least one valve. O 01/12948

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5. The invention of Claim 4, wherein said at least one valve comprises a vent valve for venting pressure from a hydraulic supply circuit.

6. A subsea hydrocarbon production installation including a subsea template having a hydraulic power supply system and at least one associated installation connected to said template by at least one flexible pipe, further including control means powered by the hydraulic power supply of the template, and incorporating the invention as defined in Claim 5, wherein said at least one vent valve is adapted to vent pressure supplied by said hydraulic power supply to said control means.

7. A subsea hydrocarbon production installation as claimed in Claim 6, wherein said associated installation (s) comprise at least one wellhead and/or at least one flowline manifold.

8. A subsea hydrocarbon production installation as claimed in Claim 7, wherein said control means comprise at least one control module associated with at least one of said template, said wellhead (s) and said flowline manifold (s).

9. The invention as claimed in any preceding Claim, wherein one or more flexible pipes is connected to one or more actuating means.

10. The invention as claimed in any preceding Claim, wherein the connecting means is arranged to effect O 01/12948

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substantially simultaneous actuation of a plurality of valves in a vent valve assembly for venting pressure from a plurality of hydraulic supply lines connected to a hydraulic ring main system.

11. The invention as claimed in any preceding Claim, wherein said at least one system component comprises at least one valve, said actuating means of said at least one valve comprises a lever and means connecting said pipeline to said lever is adapted to transfer force arising from movement of said flexible pipe directly to said lever.

12. The invention as claimed in any preceding Claim, wherein means connecting said pipeline to said actuating means includes a flexible lanyard.

13. The invention as claimed in any preceding Claim, wherein means connecting said pipeline to said actuating means is connected to said pipe at a location adjacent to a fluid coupling between an end of said flexible pipe and associated rigid pipework.