EP4695496A1

EP4695496A1 - Method and system of changing between hydraulic and electric operated x-mas tree

Info

Publication number: EP4695496A1
Application number: EP23933243.0A
Authority: EP
Inventors: Alan ZARAGOZA LABES
Original assignee: FMC Technologies Inc
Current assignee: FMC Technologies Inc
Priority date: 2023-04-14
Filing date: 2023-04-14
Publication date: 2026-02-18
Also published as: WO2024215330A1

Abstract

A method of changing from a hydraulic operated X-mas tree to an electric operated X-mas tree. The X-mas tree comprising at least one hydraulic operated actuator (200) for a valve (110) in the X-mas tree, wherein a spring (210) in the hydraulic operated actuator (200) provides a fail-safe function for closing the valve (110). The X-mas tree further comprising a hydraulic control system (430) with a compensator (450). The method comprises adding (510) a linear electric operated actuator (300) to the hydraulic operated actuator (200) to actuate the valve (110); using (520) only the spring (210) of the hydraulic operated actuator (200) to provide the fail-safe function for closing the valve (110); adding (530) an electric control module (470) to the X-mas tree; and providing (540) means to interconnect all internal chambers (240) in the hydraulic operated actuator (200) to the compensator (450). A system for changing from a hydraulic operated X- mas tree to an electric operated X-mas tree, and vice versa, is also disclosed. The system comprises a X-mas tree (100) comprising at least one hydraulic operated actuator (200) for a valve (110) in the X-mas tree, wherein a spring (210) in the hydraulic operated actuator (200) provides a fail-safe function for closing the valve (110); a linear electric operated actuator (300) releasable coupled to the hydraulic operated actuator (200), the linear electric operated actuator (300) being configured for opening or closing the valve (110); and means to interconnect all internal chambers (240) in the hydraulic operated actuator (200) to a compensator (450), for hydraulics, of the X-mas tree (100).

Description

METHOD AND SYSTEM OF CHANGING BETWEEN HYDRAULIC AND

ELECTRIC OPERATED X-MAS TREE

Technical Field

The present disclosure relates to a method of changing from a hydraulic operated X-mas tree to an electric operated X-mas tree. The present disclosure also relates to a system for changing from a hydraulic operated X-mas tree to an electric operated X-mas tree, and vice versa, and a method of changing from an electric operated X-mas tree to a hydraulic operated X-mas tree, using such a system. The system and method is used in the oil and gas industry, subsea and on land.

Background

A X-mas tree in the oil and gas industry comprises valves to regulate flow of pipes in an oil well, gas well, water injection well, and other types of wells. Hydraulic operated actuators are used to control flow through the valves. The control and safety measures on a X-mas tree are paramount considerations.

For a X-mas tree that is constructed for being operated by hydraulic, it is a problem to change so that the X-mas tree can be operated by electronics. It is a problem to change hydraulic operated valves to be electrically operated valves. Such changes are problematic when constructing the X-mas tree and also problematic after having installed the X-mas tree, especially if installed subsea, it is a problem that a X-mas tree is either hydraulic operated or electric operated, and a change between the two operation modes is not possible.

A further problem is that the X-mas tree may be subsea, possibly at several hundred meters depth, and must be able to take pressure from the outside also. This results in further problems such a high pressures, water current, darkness, presence of water, difficult or even impossible to perform maintenance in situ, etc. Maintenance and changes are a problem of X-mas trees, especially subsea X-mas trees. The X-mas tree and its valves, control and operating system, actuators, etc. must also comply with regulations and standards in the oil and gas industry.

A further technical problem is that any method or system must function without a possibility to fail, fulfil technical and legal requirements, and be easy to use. It is desirable that any solution is simple, not expensive to produce, and is reliable. It is further a technical problem to avoid cumbersome arrangements that are expensive to manufacture or assemble, it is further a technical problem to provides a solution that is applicable to existing X-mas trees. US2008/0264646 may be useful for understanding the background.

Summary of the Invention

It is an object of the present invention to provide a method of changing from a hydraulic operated X-mas tree to an electric operated X-mas tree, a system for changing from a hydraulic operated X-mas tree to an electric operated X-mas tree, and vice versa, and a method of changing from an electric operated X-mas tree to a hydraulic operated X-mas tree, using such a system. This object can be achieved by the features as defined by the independent claims. Further enhancements are characterized by the dependent claims. The invention is defined by the claims.

According to one embodiment, a method of changing from a hydraulic operated X-mas tree to an electric operated X-mas tree is disclosed. The X-mas tree comprising at least one hydraulic operated actuator 200 for a valve 110 in the X-mas tree, wherein a spring 210 in the hydraulic operated actuator 200 provides a fail-safe function for closing the valve 110. The X-mas tree further comprising a hydraulic control system 430 with a compensator 450. The method comprises adding 510 a linear electric operated actuator 300 to the hydraulic operated actuator 200 to actuate the valve 110; using 520 only the spring 210 of the hydraulic operated actuator 200 to provide the fail-safe function for closing the valve 110; adding 530 an electric control module 412 to the X-mas tree; and providing means to interconnect all internal chambers in the hydraulic operated actuator 200 to the compensator 450. The providing of means to interconnect all internal chambers in the hydraulic operated actuator 200 to the compensator 450, may further comprise providing one or more conduits 420 to supply the hydraulic operated actuator 200 with hydraulic fluid, and providing the compensator 450 connected to the one or more conduits 420. The method is preferably made subsea or on the surface. Further enhancements are characterized by the dependent claims.

According to one embodiment, a system for changing from a hydraulic operated X-mas tree to an electric operated X-mas tree, and vice versa, is disclosed. The system comprises a X-mas tree 100 comprising at least one hydraulic operated actuator 200 for a valve 110 in the X-mas tree, wherein a spring 210 in the hydraulic operated actuator 200 provides a fail-safe function for closing the valve 110. The system further comprises a linear electric operated actuator 300 releasable coupled to the hydraulic operated actuator 200, the linear electric operated actuator 300 being configured for opening or dosing the vaive 110; and means to interconnect all internal chambers 240 in the hydraulic operated actuator 200 to a compensator 450, for hydraulics, of the X-mas tree 100. The means to interconnect all internal chambers 240 in the hydraulic operated actuator 200 to the compensator 450 may comprise one or more conduits 420 to supply the hydraulic operated actuator 200 with hydraulic fluid, and the compensator 450 connected to the one or more conduits 420. The system is preferably a subsea system or a surface system. Further enhancements are characterized by the dependent claims.

According to one embodiment, a method of changing from an electric operated X-mas tree to a hydraulic operated X-mas tree, using the system described herein, is disclosed. The method comprises removing 610 any linear electric operated actuator 300 from any ROV override interface 220 at the hydraulic operated actuator 200 to actuate the valve 110; providing 620 a subsea control module 460 for hydraulics on a SCM mounting base 400 of the X-mas tree for operating the hydraulic operated actuator 200; and maintaining 630 the compensator 450. The method may further comprise providing one or more conduits 420 for supplying the hydraulic operated actuator 200 with hydraulic fluid; and connecting the compensator 450 to the one or more conduits 420. The method is preferably made subsea or on the surface. Further enhancements are characterized by the dependent claims.

At least one of the above embodiments provides one or more solutions to the problems and disadvantages with the background art. Other technical advantages of the present disclosure will be readily apparent to one skilled in the art from the following description and claims. Various embodiments of the present application obtain only a subset of the advantages set forth. No one advantage is critical to the embodiments. Any disclosed embodiment may be technically combined with any other disclosed embodiment or embodiments.

Brief Description of the Drawings

The accompanying drawings illustrate presently exemplary embodiments of the disclosure and serve to explain, by way of example, the principles of the disclosure.

Fig 1 is a diagrammatic and schematic illustration of a system according to an exemplary embodiment of the disclosure; Fig 2 is a diagrammatic illustration of a part of figure 1 according to a further exemplary embodiment of the disclosure;

Fig 3 is a diagrammatic illustration of a method according to an exemplary embodiment of the disclosure; and

Fig 4 is a diagrammatic illustration of a method according to an exemplary embodiment of the disclosure.

Detested Description

Figures 1 and 2 illustrate an exemplary embodiment of the system for changing from a hydraulic operated X-mas tree to an electric operated X-mas tree, and vice versa. Figure 1 is a schematic illustration of the X-mas tree 100 with a valve 110 for controlling flow out or in of the well. Other valves of the X-mas tree has been omitted since only one valve is necessary for describing the invention. The X-mas tree may be a subsea tree on a seabed 10 or a surface tree on the surface 10. Figure 2 illustrates an exemplary embodiment of the hydraulic operated actuator 200, in figure 1 , that opens and closes the valve 110. Figure 2 only shows the principals of the hydraulic operated actuator 200. Figures 3 and 4 are flow charts of the method of changing from a hydraulic operated X-mas tree to an electric operated X-mas tree and the method of changing from an electric operated X-mas tree to a hydraulic operated X-mas tree.

The X-mas tree 100 may be electrically operated or hydraulically operated. It is desirable to be able to change how a X-mas tree is operated. If it is hydraulic operated, then it may be desirable to change so it is electric operated. If it is operated by electricity, then it may be desirable to change so it is operated by hydraulic. A X-mas tree is a large and sophisticated equipment and any fundamental changes such as how it is operated is not easy to realise.

The X-mas tree 100 comprises at least one hydraulic operated actuator 200 for the valve 110 in the X-mas tree. A spring 210 in the hydraulic operated actuator 200 provides a fail-safe function for closing the valve 110. The fail-safe function ensures that if the control system fails, is not working as it should, then the valve 110 is closed by the spring 210. The fail-safe function may be provided by only the spring 210. The hydraulic operated actuator 200 is an actuator that is operated by hydraulic fluid and a piston 230 and produces a reciprocating movement in a linear direction to open or close the valve 110. The liner electric operated actuator 300 is an actuator that is operated by electricity and directly, or indirectly, produces a movement in a linear direction. The liner electric operated actuator 300 may comprise an electric motor that produces a movement in a linear direction. The liner electric operated actuator 300 may comprise an electric motor that drives a pump that pumps hydraulics to a piston within the liner electric operated actuator 300, and the piston in turn produces the movement in the linear direction. The valve 110 may be any valve in the X-mas tree, for example a master valve, a wing valve, or a swab valve.

Turning first to figure 3, a method of changing from a hydraulic operated X- mas tree to an electric operated X-mas tree is disclosed. The X-mas tree 100 comprises at least one hydraulic operated actuator 200 for a valve 110 in the X-mas tree. A spring 210 in the hydraulic operated actuator 200 provides a fail-safe function for closing the valve 110. The X-mas tree further comprising a hydraulic control system 430 with a compensator 450. Preferably the X-mas tree is a subsea X-mas tree. The method comprises the following steps, taken in any order. Adding 510 a linear electric operated actuator 300 to the hydraulic operated actuator 200 to actuate the valve 110; using 520 only the spring 210 of the hydraulic operated actuator 200 to provide the fail-safe function for closing the valve 110; adding 530 an electric control module 470 to the X-mas tree; and providing 540 means to interconnect ail internal chambers in the hydraulic operated actuator 200 to the compensator 450. In this way the linear electric operated actuator 300 is added to the hydraulic operated actuator 200 to actuate the valve 110, whereby only the spring 210 of the hydraulic operated actuator 200 provides the fail-safe function for closing the valve 110. There is no need for the linear electric operated actuator 300 to provide a fail-safe function. There is no need for any batteries, or additional back up, or electric control system, for providing the fail-safe function. The electric control module 470 controls the flow of electricity to the linear electric operated actuator 300. The electric control module 470 may be arranged onto a subsea control module, SCM, mounting base 400 of the X-mas tree 100 and allows the valve 110 to be controlled and operated, opening and closing. When the X-mas tree has been changed according to the method, then the X-mas tree can be operated only by electricity and no hydraulic is needed to control the valves. To allow the hydraulic operated actuator 200 to be controlled by the linear electric operated actuator 300, means are provided to interconnect all internal chambers in the hydraulic operated actuator 200 to the compensator 450 and in this way the hydraulic operated actuator 200 can move freely without the flow of hydraulic fluid to interfere. This also allows to use the spring 210 of the hydraulic actuator 200 to provide the fail-safe function for closing the valve 110. This is advantageous because that fail-safe function complies with the necessary requirements.

The step 540 of providing means to interconnect all internal chambers in the hydraulic operated actuator 200 to the compensator 450, may comprise providing one or more conduits 420 to supply the hydraulic actuator 200 with hydraulic fluid, and providing the compensator 450 connected to the one or more conduits 420. As may best be taken from figures 1 and 2, the hydraulic operated actuator 200 may have a piston 230, a spring 210, and internal chambers such that the piston 230 can overcome the spring force and open the valve 110. The hydraulic oil may be provided to the piston and in the internal chamber 240 of the spring 210.

The step 540 of providing means to interconnect all internal chambers in the hydraulic operated actuator 200 to the compensator 450, may further comprise adding a logic cap 410 to a subsea control module, SCM, mounting base 400 of the X-mas tree to enable hydraulic fluid to flow freely to and from the hydraulic actuator 200 and the compensator 450, via the one or more conduits 420. The logic cap 410 may be a connector allowing the flow of the one or more conduits 420, for example two conduits 420 as illustrated in figures 1 and 2, to be connected such that hydraulic may flow freely from all internal chambers 240 in the hydraulic operated actuator 200 to the compensator 450. The logic cap 410 may provide a connection from one conduit 420 to another conduit 420.

As may be taken from figures 1 and 2, the linear electric operated actuator 300 may be added to the hydraulic operated actuator 200 to actuate the valve 110 by adding the linear electric operated actuator 300 to a remote operated vehicle, ROV, override interface 220 at the hydraulic actuator 200 to actuate the valve 110. The interface may be a standard interface 220 allowing a standard connection to be made. This may be done subsea, or before on land while manufacturing the X-mas tree.

The method according to figure 3 may further comprise removing any umbilical connector, or umbilical, for hydraulics for the hydraulic operated X-mas tree; and adding a connector 480 for electric control signals, or adding a receiver 480 for wireless control signals, in figure 1 the connector and receiver has the same reference number to keep it simple. This allows to use electric control signals to control and operate the valve 110.

The method according to figure 3 may further comprise maintaining a subsea control module, SCM, mounting base 400 of the X-mas tree 100 and a SCM 460 and use the SCM 460 to enable hydraulic fluid to flow freely to and from the hydraulic actuator 200 and the compensator 450, via the one or more conduits 420. If the hydraulic operated X-mas tree has a SCM mounting base 400 and a SCM 460, then one may maintain them. The SCM 460 may be configured, to function as the logic cap 410, to enable hydraulic fluid to flow freely to and from the hydraulic actuator 200 and the compensator 450, via the one or more conduits 420. In this way the piston 230 is able to move freely and the linear electric operated actuator 300 may move the piston 230 to operate the valve 110.

Turning to figures 1 and 2, a system for changing from a hydraulic operated X-mas tree to an electric operated X-mas tree, and vice versa, is illustrated. The system allows for a X-mas tree that is operated by hydraulic to be changed so it is operated only by electricity. The system allows for a X-mas tree that is operated by electricity to be changed to be operated only by hydraulic. The system comprises a X-mas tree 100 comprising at least one hydraulic operated actuator 200 for a valve 110 In the X-mas tree. A spring 210 in the hydraulic operated actuator 200 provides a fail-safe function for closing the valve 110. The fail-safe function may be provided only by the spring 210 of the hydraulic operated actuator 200 with no further equipment having to be installed to ensure the fail-safe function. The system comprises a linear electric operated actuator 300 releasable coupled to the hydraulic actuator 200, the linear electric actuator 300 being configured for opening or closing the valve 110. The system comprises means to interconnect all internal chambers 240 in the hydraulic operated actuator 200 to a compensator 450, for hydraulics, of the X-mas tree 100. As illustrated in figures 1 and 2, the linear electric operated actuator 300 is releasable coupled to the hydraulic actuator 200. A linear movement of the linear electric operated actuator 300 may actuate a piston 230 against the force of the spring 210 in the hydraulic actuator 200. Such a linear movement may be controlled by electricity and open and close the valve 110.

As illustrated in figures 1 and 2, the means to interconnect all internal chambers In the hydraulic operated actuator 200 to the compensator 450 may comprise one or more conduits 420 to supply the hydraulic operated actuator 200 with hydraulic fluid. The compensator 450 may be connected to the one or more conduits 420. The system may further comprise a logic cap 410 added to a subsea control module, SCM, mounting base 400 of the X-mas tree 100 to enable hydraulic fluid to flow freely to and from the hydraulic operated actuator 200 and the compensator 450, via the one or more conduits 420. This allows the piston 230 to move and be controlled by the linear movement of the linear electric operated actuator 300. The hydraulic fluid inside the internal chambers 240, where the piston 230 and the spring 210 are, may flow to and from the compensator. The one or more conduits 420 may supply hydraulic fluid on both sides of the piston 210 and supply hydraulic fluid around the spring 210 of the hydraulic operated actuator 200. The logic cap 410 may direct the hydraulic fluid flow from one conduit 420 to another conduit 420 so that the hydraulic fluid can flow to the compensator 450. The compensator 450 may have the technical function of an accumulator and/or a pressure compensator.

As illustrated in figures 1 and 2, the hydraulic operated actuator 200 may further comprise a ROV override interface 220. The linear electric operated actuator 300 may be configured to be releasable coupled directly to the ROV override interface 220 at the hydraulic operated actuator 200 to actuate the valve 110. The ROV interface 220 may be used to connect the linear electric actuator 300 directly without the use of any further means to connect. This allows for a safe, easy and economic way of converting an hydraulic operated X-mas tree to be operated by electricity.

According to one embodiment, the system may further comprise an electric control module 470 for controlling the linear electric actuator 300. As illustrated in figure 1 , the electric control module 470 may be added to the SCM mounting base 400. The electric control module 470 may be connected to an umbilical or an umbilical connector. Alternatively, the electric control module 470 may be added to the top side.

As illustrated in figures 1 and 2, the system may further comprises a subsea control module, SCM, mounting base 400 on, or proximate, the X-mas tree and a SCM 460. The SCM 460 may be configured to enable hydraulic fluid to flow freely to and from the hydraulic operated actuator 200 and the compensator 450, via the one or more conduits 420. The SCM 460 may direct the flow of hydraulics in the one or more conduits 420 to the compensator 450. In this way an interconnect of all internal chambers 240 in the hydraulic operated actuator 200 can be made to the compensator 450, The SCM 460 may function as the logic cap described herein.

Turning to all figures, especially figure 4, a method of changing from an electric operated X-mas tree to a hydraulic operated X-mas tree, using the system described herein is disclosed. The method comprises removing 610 any linear electric operated actuator 300 from any ROV override interface 220 at the hydraulic operated actuator 200 to actuate the valve 110; providing 620 a subsea control module 460 for hydraulics on a SCM mounting base 400 of the X-mas tree for operating the hydraulic operated actuator 200; and maintaining 630 the compensator 450. A X-mas tree as described by the system herein may be converted from being an electric operated X-mas tree to a X-mas tree that is operated by hydraulic, without having to make substantial modifications. For example, the fail-safe function is maintained and needs no modifications. These changes, between the two operation modes, can be done subsea or at the surface or in a workshop.

According to one embodiment, the method may further comprise providing one or more conduits 420 for supplying the hydraulic operated actuator 200 with hydraulic fluid; and connecting the compensator 450 to the one or more conduits 420. This allows the SCM to control and operate the valves as any hydraulic fluid may be accumulated and/or pressure compensated in the compensator 450.

According to one embodiment, the method may further comprise adding an umbilical connector, or umbilical, for providing hydraulics to the hydraulic operated X- mas tree. In this way hydraulic fluid may be provided from the top side to operate the X-mas tree.

This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using the system and performing the methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.

List of elements

100 X-mas tree

110 valve

200 hydraulic operated actuator

210 spring

220 ROV override interface

230 piston

240 internal chambers

300 linear electric operated actuator 310 tank

310 valves

320 conduits

400 subsea control module, SCM, mounting base

410 logic cap

420 one or more conduits

430 hydraulic control system

440

450 compensator

460 subsea control module, SCM

470 electric control module

480 receiver or connector

510 Adding a linear electric operated actuator 300 to the hydraulic actuator 200 to actuate the valve 110.

520 Using 520 only the spring 210 of the hydraulic actuator 200 to provide the failsafe function for closing the valve 110.

530 Adding an electric control module 470 to the X-mas tree.

540 Providing means to interconnect all internal chambers in the hydraulic operated actuator 200 to the compensator 450.

610 Removing any linear electric operated actuator 300 from any ROV override Interface 220 at the hydraulic operated actuator 200 to actuate the valve 110.

620 Providing a subsea control module 460 for hydraulics on a SCM mounting base

400 of the X-mas tree for operating the hydraulic operated actuator 200.

630 Maintaining the compensator 450.

Claims

1 A method of changing from a hydraulic operated X-mas tree to an electric operated X-mas tree, the X-mas tree comprising at least one hydraulic operated actuator (200) for a valve (110) in the X-mas tree, wherein a spring (210) in the hydraulic operated actuator (200) provides a fail-safe function for closing the valve (110), the X-mas tree further comprising a hydraulic control system (430) with a compensator (450), the method comprising adding (510) a linear electric operated actuator (300) to the hydraulic operated actuator (200) to actuate the valve (110); using (520) only the spring (210) of the hydraulic operated actuator (200) to provide the fail-safe function for closing the valve (110); adding (530) an electric control module (470) to the X-mas tree; and providing (540) means to interconnect all internal chambers (240) in the hydraulic operated actuator (200) to the compensator (450).

2 The method according to claim 1 , wherein providing means to interconnect all internal chambers (240) in the hydraulic operated actuator (200) to the compensator (450) comprises providing one or more conduits (420) to supply the hydraulic operated actuator (200) with hydraulic fluid, and providing the compensator (450) connected to the one or more conduits (420).

3 The method according to claim 2, further comprises adding a logic cap (410) to a subsea control module, SCM, mounting base (400) of the X-mas tree to enable hydraulic fluid to flow freely to and from the hydraulic operated actuator (200) and the compensator (450), via the one or more conduits (420).

4 The method according to any one of the preceding claims, wherein adding the linear electric operated actuator (300) to the hydraulic operated actuator (200) to actuate the valve (110) further comprises adding the linear electric operated actuator (300) to a ROV override interface (220) at the hydraulic operated actuator (200) to actuate the valve (110).

5 The method according to any one of the preceding claims, further comprises removing any umbilical connector, or umbilical, for hydraulics for the hydraulic operated X-mas tree; and adding a connector (480) for electric control signals, or adding a receiver (480) for wireless control signals.

6 The method according to claim 2, further comprises maintaining a subsea control module, SCM, mounting base (400) of the X-mas tree and a SCM (460) and use the SCM (460) to enable hydraulic fluid to flow freely to and from the hydraulic operated actuator (200) and the compensator (450), via the one or more conduits (420).

7 A system for changing from a hydraulic operated X-mas tree to an electric operated X-mas tree, and vice versa, the system comprising a X-mas tree (100) comprising at least one hydraulic operated actuator (200) for a valve (110) in the X-mas tree, wherein a spring (210) in the hydraulic operated actuator (200) provides a fail-safe function for closing the valve (110); a linear electric operated actuator (300) releasable coupled to the hydraulic operated actuator (200), the linear electric operated actuator (300) being configured for opening or closing the valve (110); and means to interconnect all internal chambers (240) in the hydraulic operated actuator (200) to a compensator (450), for hydraulics, of the X-mas tree (100).

8 The system according to claim 7, wherein the means to interconnect all internal chambers (240) in the hydraulic operated actuator (200) to the compensator (450) comprises one or more conduits (420) to supply the hydraulic operated actuator (200) with hydraulic fluid, and the compensator (450) connected to the one or more conduits (420).

9 The system according to claim 8, further comprises a logic cap (410) added to a subsea control module, SCM, mounting base (400) of the X-mas tree (100) to enable hydraulic fluid to flow freely to and from the hydraulic operated actuator (200) and the compensator (450), via the one or more conduits (420),

10 The system according to any one of the claims 7 to 9, wherein the hydraulic operated actuator (200) further comprises a ROV override interface (220) and the linear electric operated actuator (300) is configured to be releasable coupled directly to the ROV override interface (220) at the hydraulic operated actuator (200) to actuate the valve (110).

11 The system according to any one of the preceding claims, further comprising an electric control module (470) for controlling the linear electric operated actuator (300).

12 The system according to claim 8, further comprises a subsea control module, SCM, mounting base (400) of the X-mas tree and a SCM (460); the SCM (460) being configured to enable hydraulic fluid to flow freely to and from the hydraulic operated actuator (200) and the compensator (450), via the one or more conduits (420).

13 A method of changing from an electric operated X-mas tree to a hydraulic operated X-mas tree, using the system claimed in any one of the preceding claims 7 to 12, the method comprising removing (610) any linear electric operated actuator (300) from any ROV override interface (220) at the hydraulic operated actuator (200) to actuate the valve (110); providing (620) a subsea control module (460) for hydraulics on a SCM mounting base (400) of the X-mas tree for operating the hydraulic operated actuator (200); and maintaining (630) the compensator (450).

14 The method according to claim 13, further comprises providing one or more conduits (420) for supplying the hydraulic operated actuator (200) with hydraulic fluid; and connecting the compensator (450) to the one or more conduits (420).

15 The method according to claim 13 or 14, further comprises adding an umbilical connector, or umbilical, for providing hydraulics to the hydraulic operated X- mas tree.