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Patent Searching and Data


Title:
SUBSEA ARRANGEMENT AND METHOD
Document Type and Number:
WIPO Patent Application WO/2019/045574
Kind Code:
A1
Abstract:
A processing module (100, 200) for a subsea processing system (1), comprising: an enclosure (101, 201); a fluid conduit (12, 14)leading from an internal volume of the enclosure (101, 201) to an outside of the module (100, 200), the fluid conduit (12, 14) having an end connector (31, 33) configured for connection to the subsea processing system (1), a valve (22, 24) arranged in the fluid conduit and operable to close the fluid conduit (12, 14), and an intervention line (42, 44) arranged between the valve (22, 24) and the end connector (31, 33). There is also provided a subsea processing system (1), a method of removing a processing module (100, 200) from a subsea processing system (1), and a method of installing a processing module (100, 200) in a subsea processing system (1).

Inventors:
KJENSJORD ANDERS ØSTBY (NO)
LAUVDAL ANDERS (NO)
BUNGER TYLAR PAUL (NO)
STORSTENVIK ANDERS (NO)
Application Number:
PCT/NO2018/050221
Publication Date:
March 07, 2019
Filing Date:
September 03, 2018
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
AKER SOLUTIONS AS (NO)
International Classes:
E21B41/00; E21B21/00; E21B43/01
Domestic Patent References:
WO2008002147A12008-01-03
Foreign References:
US20140090853A12014-04-03
GB2520709A2015-06-03
US3754380A1973-08-28
Attorney, Agent or Firm:
ZACCO NORWAY AS (NO)
Download PDF:
Claims:
A processing module (100,200) for a subsea processing system (1 ), the module (100,200) comprising:

an enclosure (101 ,201 );

a fluid conduit (12, 14), the fluid conduit (12, 14) leading from an internal volume of the enclosure (101 ,201 ) to an outside of the module (100,200), the fluid conduit (12, 14) having an end connector (31 ,33) configured for connection to the subsea processing system (1 ),

a valve (22,24) arranged in the fluid conduit and operable to close the fluid conduit (12, 14),

an intervention line (42,44) providing a fluid connection into the fluid conduit (12, 14), the intervention line (42,44) arranged between the valve (22,24) and the end connector (31 ,33).

A processing module (100,200) according to claim 1 , wherein at least one of the valve (22,24) and the intervention line (42,44) is located outside the enclosure (101 ).

A processing module (100,200) according to any preceding claim, comprising a second fluid conduit (13, 15), the second fluid conduit (13, 15) leading from an internal volume of the enclosure (101 ,201 ) to an outside of the module (100,200), the second fluid conduit (13, 15) having a second end connector (32,34) configured for connection to the subsea processing system (1 ), and a second valve (23,25) arranged in the second fluid conduit (13, 15) and operable to close the second fluid conduit (13, 15).

A processing module (100,200) according to the preceding claim, comprising a second intervention line (43,45) providing a fluid connection into the second fluid conduit (13, 15), the second intervention line (43,45) arranged between the second valve (23,25) and the second end connector (31 ,33).

5. A processing module (100,200) according to any of the two preceding claims, wherein the fluid conduit (12, 14) and the second fluid conduit (13, 15) are connected to the enclosure (101 ,201 ) at different vertical heights.

6. A subsea processing system comprising at least one module (100,200) according to any preceding claim.

7. A method of removing a processing module (100,200) according to any of claims 1 -5 from a subsea processing system (1 ), comprising the steps: with the valve (22,24) open, injecting a fluid into the fluid conduit (12,14) via the intervention line (42,44) and flowing the fluid into an internal volume of the module (100,200);

disconnecting the end connector (31 ,33) from the subsea processing system (1 ); and

hoisting the module (100,200) to a surface location.

8. A method according to claim 7, wherein

the fluid is a gas, or

the fluid is a liquid.

9. A method according to claim 7 or 8, comprising the steps:

pressurizing the internal volume of the module (100,200) with the fluid; and

bleeding off fluid from the internal volume.

10. A method according to claim 9, comprising the step:

measuring a hydrocarbon content of a gas bled off from the internal volume.

1 1 . A method according to any of claims 7-10, comprising:

operating a pump to remove fluid from the internal volume via the intervention line (42,44).

12. A method of installing a processing module (100,200) according to any of claims 1 -5 in a subsea processing system (1 ), comprising the steps: with the valve (22,24) closed, lowering the module (100,200) from a surface location to a subsea location; and

connecting the end connector (31 ,33) to the subsea processing system

(1 ).

13. A method according to the preceding claim, comprising applying a fluid pressure in the intervention line (42,44) to pressure test a connection between the end connector (31 ,33) and a corresponding connector on the subsea processing system (1 ).

14. A method according to the preceding claim, wherein the step of applying a fluid pressure in the intervention line (42,44) is carried out with the valve (22,24) closed.

15. A method according to any of the three preceding claims, comprising: injecting a fluid into the fluid conduit (12, 14) via the intervention line (42,44) and displacing seawater from a volume in the fluid conduit (12, 14) between the valve (22,24) and the end connector (31 ,33).

16. A method according to the preceding claim, comprising discharging the seawater via a second intervention line (41 ) fluidly connected to the fluid conduit (12, 14).

Description:
SUBSEA ARRANGEMENT AND METHOD

The present invention relates to an arrangement and a method for installing, retrieving or operating subsea equipment.

BACKGROUND

When using subsea equipment, for example in oil & gas exploitation, it is common to install and retrieve such equipment from a vessel through open water. Such equipment can be, for example compressors, pumps, flow conditioning equipment (such as separators), motors, heaters or coolers, electrical equipment, hydraulic equipment, or other components for use in a subsea system, and will typically be installed or retrieved as modules. One example of such a module is provided in WO 2008/002147 A1 , in that case being a subsea compressor module. A module may also comprise more than one piece of equipment.

Often, such modules will have fluid connections with other modules or equipment subsea. These connections have to be connected or disconnected when installing or retrieving modules. It is desirable to be able to install and/or retrieve such subsea modules in a safe and efficient manner, and with minimal risk of damage or other adverse effects on the modules. The present invention has the objective to provide a subsea arrangement and method which provides advantages over known solutions and techniques for this purpose.

SUMMARY

In an embodiment, there is provided a processing module for a subsea processing system, the module comprising: an enclosure; a fluid conduit, the fluid conduit leading from an internal volume of the enclosure to an outside of the module, the fluid conduit having an end connector configured for connection to another component of the subsea processing system, a valve arranged in the fluid conduit and operable to close the fluid conduit, an intervention line providing a fluid connection into the fluid conduit, the intervention line arranged between the valve and the end connector.

In an embodiment, there is provided a subsea processing system comprising at least one module.

In an embodiment, there is provided a method of removing a processing module from a subsea processing system, comprising the steps: with the valve open, injecting a fluid into the fluid conduit via the intervention line and flowing the fluid into an internal volume of the module; disconnecting the end connector from a component of the subsea processing system; and hoisting the module to a surface location.

In an embodiment, there is provided a method of installing a processing module in a subsea processing system, comprising the steps: with the valve closed, lowering the module from a surface location to a subsea location; and

connecting the end connector to a component of the subsea processing system.

The appended claims outline further embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

Illustrative embodiments of the present invention will now be described with reference to the appended drawings, in which:

Figures 1 and 2 show a subsea arrangement according to an embodiment.

DETAILED DESCRIPTION For installation and retrieval of subsea processing modules, there may for example be a requirement to displace seawater after connection of two pipes, to pressure test connections, or to displace hydrocarbons before disconnecting the pipes prior to retrieving the module. Current methods for these processes are time consuming and complex, and has high potential for human error. Figure 1 shows, schematically, parts of a subsea processing system 1 comprising two replaceable modules 100,200. The subsea processing system 1 is in this case a production system for processing a hydrocarbon flow from a well (not shown). Figure 2 shows module 100 and its associated components separate from the production system 1 , for example after retrieval or before installation of module 100. Each module 100,200 comprises an enclosure 101 ,201. The enclosure 101 ,201 may be a pressure housing, rated for operation of the module 100,200 at a given water depth and at a given operating pressure. A first fluid pipe 1 1 forms a fluid conduit leading to the first module 100 from a different part of the subsea production system 1. The first fluid pipe 1 1 may, for example, be a pipe providing petroleum products from a wellhead. Pipework is provided to lead the petroleum products from the first fluid pipe 1 1 , through the first module 100 and the second module 200, and out through a second fluid pipe 16.

The first pipe 1 1 comprises a valve 21 and a connector, in this case in the form of a flange 30. An intervention line 41 is arranged with the first pipe 1 1 , the intervention line 41 being fluidly connected to the interior of the first pipe 1 1 at a point between the valve 21 and the flange 30.

The first module 100 comprises an inlet pipe 12 and an outlet pipe 13 leading into and out of the enclosure 101 . The inlet pipe 12 has a valve 22, a flange 31 and an intervention line 42 arranged between the valve 22 and the flange 31 . The outlet pipe 13 has a valve 24, a flange 33 and an intervention line 44 arranged between the valve 22 and the flange 33.

The second module 200 comprises an inlet pipe 14 and an outlet pipe 15 leading into and out of the enclosure 201 . The inlet pipe 14 has a valve 24, a flange 33 and an intervention line 44 arranged between the valve 24 and the flange 33. The outlet pipe 15 has a valve 25, a flange 34 and an intervention line 45 arranged between the valve 25 and the flange 34. The second pipe 16 comprises a valve 26 and a flange 35. An intervention line 45 is arranged with the second pipe 16 between the valve 26 and the flange 35.

In the installed configuration, as shown in Fig. 1 , the flange 30 of the first pipe 1 1 is connected to the flange 31 of the pipe 12, the flange 32 of pipe 13 is connected to flange 33 of pipe 14, and flange 34 of pipe 15 is connected to flange 35 of pipe 16. All the valves 21 -26 are open. The intervention lines 41 -46 are closed, for example with a valve arranged in the line, or the line can be plugged. In this manner, a fluid provided through pipe 1 1 can flow through modules 100,200 and out through pipe 16. The modules 100,200 may comprise, for example fluid processing equipment such as a separator, a compressor, or other equipment.

The flanges 30-35 between the components in the system shown in Fig. 1 provide releasable connections such that the modules 100,200 can be individually retrieved from the installation, for example for replacement in case of failure or for maintenance. Prior to retrieval to surface of one or both of the modules 100,200, it may be desirable to remove or reduce the hydrocarbon content of the module. This may be needed to avoid or reduce the risk of hydrocarbon leakage on the vessel deck, and/or fire and explosion hazard. This can be achieved, for example, by purging or diluting the content of the module 100,200 by an inert fluid, such as nitrogen, water or another fluid which is non- reactive. In a method according to an embodiment, displacement of hydrocarbons in one of the modules 100,200 (or in both) can be achieved by operation of the valves 21 -26 and intervention lines 41 -46. For example, if module 100 is to be removed, valve 21 is closed and intervention line 42 is utilized to inject an inert fluid. Intervention line 42 can be activated by appropriate tools, for example can a ROV connect to the intervention line 42 and open a valve in this line (or remove a plug, if intervention line 42 was plugged), and connect an inert fluid supply line. Valve 23 is open such that the fluid in module 100 is allowed to exit the module 100. Valve 24 may be open, such that fluid from the module 100 is passed down into the production system, or intervention line 43 or 44 may be open to discharge the fluid in module 100 through this line. A ROV may, for example, be used in the same manner as described above to prepare

intervention line 43 for this operation. Fluid being discharged to intervention line 43 may be discharged to sea, or a fluid line for receiving the fluid may be connected to intervention line 43.

Having injected a sufficient amount of inert fluid through intervention line 42, valves 22 and 23 may be closed and module 100 is ready for retrieval with its internal hydrocarbon content (e.g. condensate and gas) having been reduced to zero or diluted to acceptable concentrations.

Flanges 31 and 32 are then released, to free the module 100 for retrieval.

Valves 21 and 24 are preferably closed prior to this, to avoid inflow of sea water into the remaining subsea system components.

As the external pressure subsea is higher than the atmospheric pressure it can be desirable to reduce the differential pressure between the inert fluid pressure being supplied to intervention line 42 and the outlet of the module 100. If so the method may include closing module isolation valve 22 or 23 and reducing the pressure in module 100, and then closing valve 22 or 23 again prior to retrieval. The pressure reduction can, for example, be done by means of a pump. With this, a reduced pressure or vacuum can be obtained, to reduce the potential differential pressure to atmosphere. For some situations it might be desirable to retrieve the modules 100,200 with gas to minimize the weight of modules or for preservation of the internal equipment. The inert fluid in this embodiment may, for example, be nitrogen gas. The modules 100 and/or 200 may have the pipes 12-15 located at different heights of the module. This may allow for more efficient purging or displacement of the module 100 by utilizing the different densities between the purging fluid and the fluid contained in the module 100. For example, if module 100 is originally filled mainly with hydrocarbon gas, and it is desirable to displace using water, such water can be injected into the module 100 via pipe 12 which has its inlet near the lower end of module 100. The outlet via pipe 13 is located near the upper end of the module 100, such that the water column as it's injected into module 100 will push substantially all the gases out of the module 100 and there will be little or no mixing. Conversely, if the module 100 for example contains mainly liquids and the displacement fluid is gas, then the gas can be injected via line 13 near the upper end of the module 100, and the fluid originally in module 100 will be pushed out through line 12. In this case, the flow direction for the purging through module 100 is reversed compared to that described above.

In one embodiment, the module 100 may be filled fully or partially by a gas, such as a hydrocarbon gas, and it is desirable to purge the module 100 using an inert gas. In this embodiment, inert gas can be injected through intervention line 42 or 43 to pressurize the module 100. The gas in module 100 is then bled off, for example through one of lines 12 and 13 (or, alternatively, a different line). The hydrocarbon content of the bled-off gas is measured to determine whether the hydrocarbon level is sufficiently low for safe retrieval. If necessary, inert gas is once again injected, diluting the hydrocarbon content in module 100 further, and module 100 is bled off once more. The procedure is repeated until the hydrocarbon content is acceptable. The module isolation valves 22 and 23 are then closed and the module can be retrieved safe to vessel deck.

For installation of a subsea module such as module 100, the other components as shown in Fig. 1 will be in place, with valves 21 and 24 closed such as to avoid seawater ingress into pipes 1 1 and 14. Valves 22 and 23 (the so-called "module isolation valves") are also closed to avoid ingress of seawater into module 100. Module 100 can now be installed by positioning it in place and connecting flange 31 to flange 30 and connecting flange 32 to flange 33.

As the installation process is carried out in open water, the volume in the pipe ends between the module isolation valve 22 and valve 12, and the volume between module isolation valve 23 and valve 24, will be filled with seawater after connection. It may be desirable to remove this seawater prior to opening the module isolation valves 22,23 and initiating production flow through the system. For example, components in the module 100 (such as electronics) may be sensitive to sea water and one may experience adverse effects such as reduced lifetime or increased failure rates if this trapped seawater is allowed to flow into the module 100.

In one embodiment, a method of installing a subsea module 100 (or 200) comprises connecting the module 100 with connectors 31 ,32 to respective system connectors 30,33. After connection, any trapped seawater is displaced from the pipe section between valve 22 and a corresponding system valve 21 by injecting a fluid into intervention line 42 and opening intervention line 41 for fluid to exit. (Alternatively, injection can be done through line 41 and fluid exit via line 42.) It is thereby possible to displace (or purge) any fluid trapped between valves 21 and 22 prior to opening these valves and fluidly connecting the module 100 to the subsea production system. A similar method can be used to remove any trapped sea water between valves 23 and 24, and an equivalent method may be used when installing module 200.

Intervention lines 41 -46 can for this purpose be operated by means of, for example, a valve (which can be remotely operable or locally operable, e.g. by means of a ROV), or their operation can be arranged in a different manner, for example by hooking up a ROV which connects to the respective intervention line 41 -46 and removes a plug in the line. Fluid for flushing/displacing/purging can, for example, be supplied via a pipe which is permanently or temporarily connected to the intervention line 41 -46, via a local storage (e.g. an

accumulator or gas container), or via a ROV.

Pairs of intervention lines 41 -46 which are located on either side of a connection 30-35 may be arranged at different heights, i.e. vertically displaced. This allows gravity-assisted displacement or purging of the lines 1 1 -16. For example, when displacing water from line 1 1 and 12, between valves 21 and 22, a gas (such as nitrogen) can be injected into intervention line 42 which is located higher than intervention line 41 , whereby liquid will be displaced downwards and out of intervention line 41. Alternatively, an inert liquid having a density higher than sea water may be injected into intervention line 41 , and sea water discharged through intervention line 42.

After displacing sea water in the manner described above, the respective intervention lines 41 -46 will be closed (e.g. by closing a valve in the line or by plugging it), and the respective valves (e.g. valves 21 -24 in the case of installing module 100) will be opened to provide fluid communication between the subsea production system and the module 100,200. In one embodiment, it may be desirable or required to pressure test the connections (e.g. the connection between flanges 30 and 31 and between flanges 32 and 33) before the valves 21 -26 can be opened and the newly installed module 100,200 is fluidly connected in the subsea production system. Such testing may be required to ensure the integrity of the flange connections and make sure there will be no leakage to sea when production commences.

In one embodiment, the method comprises pressure testing a connection between a module 100,200 and other components of the subsea production system by means of pressurising one of the respective lines 1 1 -16 through an intervention line 41 -46. For example, to pressure test the connection between flanges 30 and 31 , intervention line 41 or 42 may be used. The fluid used for pressure testing may be a gas or a liquid, depending on the requirements and preferred solution in the circumstances. Supply of pressurising fluid may be from a supply pipe, from a local storage, from a ROV, or by other means.

Access to and operation of the intervention lines 41 -46 can be done similarly as described above, e.g. via a ROV. Valve 21 is closed and valve 22 may also be closed when pressure testing connection 30,31. This can minimize the time required for such pressure testing, and also the amount of fluid required, as the volume between valves 21 and 22 is relatively small and the internal volume of the module 100 will not be part of the tested volume. Alternatively, valve 22 may be open and one may pressurize also the internal volume of module 100. In another alternative, valve 23 may also be open and valve 24 closed, whereby also connection 32,33 can be pressure tested in the same operation. According to this embodiment, connections can thus be leak tested with reduced time and with higher confidence, as for example temperature changes in a large volume can give uncertainties to the pressure test. One or more of the intervention lines 41 -46 can be used for injection of the test medium and can also be connected to sensors to monitor and verify the results. Additionally, it is possible to carry out the leakage test specifically for a given connection by controlling which valves 21 -26 are closed, and thus eliminate other possible leakage sources. Each module 100,200 may have one intervention line 41 -46 or more than one. As shown in Fig. 1 , other components of the subsea production system may also be equipped with equivalent intervention lines 41 and 46. One intervention line per module may be sufficient in certain cases, for example for pressure testing or hydrocarbon flushing/purging prior to retrieval.

According to embodiments described above, systems and methods are provided which provide advantages for example in the form of reduced offshore time for installation and replacement of subsea processing modules and improved safety.

When used in this specification and claims, the terms "comprises" and

"comprising" and variations thereof mean that the specified features, steps or integers are included. The terms are not to be interpreted to exclude the presence of other features, steps or components.

The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

The present invention is not limited to the embodiments described herein;

reference should be had to the appended claims.