GB2387891A

GB2387891A - Electrothermal actuator

Info

Publication number: GB2387891A
Application number: GB0209646A
Authority: GB
Inventors: James Brian Wilson
Original assignee: ABB Offshore Systems Ltd
Current assignee: Baker Hughes International Treasury Services Ltd
Priority date: 2002-04-26
Filing date: 2002-04-26
Publication date: 2003-10-29
Also published as: GB0209646D0

Abstract

An electrothermal actuator 100, for use in downhole valve actuation, has a piston 10 controlled by an element 6 which heats and expands a wax, which in turn displaces the piston 10. The piston 10 increases pressure of a fluid in a cavity 23 and through an orifice 24 to actuate the valve. The piston 10 may be held in place by a latch 15 so that the electric supply can be turned off whilst maintaining pressure in the cavity 23. In another embodiment, the piston 10 provides the fluid actuator as above, as well as providing a mechanical actuation itself(fig 3).

Description

1 238789 1

Method of actuation of sub-surface control devices and actuators therefor The present invention relates to a method of actuation of control devices, such as valves, in a sub-surface installation such as a fluid extraction well (such as a 5 hydrocarbon production well), and to actuators therefor. The installation or well may be below a land surface or a sea surface or a sub-sea surface and the method is particularly, although not exclusively, suitable for use in sub-sea oil wells for the actuation or control of hydraulically actuated control devices. For example, a method according to the invention may be carried out and an actuator according to the 10 invention may be at a "Christmas" tree in a sub-sea oil well to operate downhole devices. Traditionally, fluid exit action wells have used and still use hydraulically operated control devices. Electrically operated devices, although recognised to have 15 some significant advantages over hydraulically controlled devices, have not normally been employed and the extensive employment of such electrically operated devices would be a radical new departure in the fluid extraction industry. Hereinafter, reference will generally be made to valves, instead of control devices, but it is intended that the expression, where appropriate and possible, should encompass other 20 forms of control devices than valves, for example flow control chokes.

Producers have been nervous about making the change to using electrically operated valves because they have little or no experience of the longterm reliability of electrically actuated valves as compared with their extensive experience of their 25 hydraulic counterparts. Thus the fluid extraction industry has required the use of high pressure hydraulic fluid lines extending from the surface to operate valves which are often situated deep underground or at or below a sea bed.

Patent GB2328492 describes an electrical actuator device for electrically 30 operating valves and a method of using this actuator for controlling devices in a well.

The actuator of this patent includes a cylinder containing a material that when

subjected to electrical heating expands to move a piston. A shaft, coupled to the piston, is moved linearly with movement of the piston to operate a valve, typically but not exclusively in a production fluid extraction well. This actuator is described in more detail below in relation to Fig. 1 of the accompanying drawings.

s One aspect of the present invention seeks to enable extraction well operators to transfer to electrical operation of control devices in an easier step, and also to enable existing installations to be converted to electrical actuation without having to change existing hydraulically operated valves. In this way, experience of electrical 10 actuation may be gained before taking the final step to full electrical actuation, which the use of the device described in the abovementioned prior patent would involve.

According to a first aspect of the present invention, a method of actuating a hydraulic pressure operated control device of a sub-surface installation from a remote 15 station, comprises: providing electrically operated hydraulic pressure output producing means positioned sub-surface in the region of the control device; providing a hydraulic coupling between a hydraulic output of said means and a hydraulic control input of said device; 20 providing an electrical energy operating supply from the remote station to said means; and controlling operation of the device by controlling the output hydraulic pressure from said means to said device by controlling the electrical energy supply from the remote station.

A second aspect of the invention seeks to provide electrically operated means suitable for use in said first aspect but which are capable of providing both a mechanical and a hydraulic output.

According to a second aspect of the present invention, an electrically operated actuator, comprises: a chamber containing a thermal expansion medium; an electric heater for heating said medium to cause it to expand; 5 a mechanical linkage linked with said expansion medium chamber such that expansion of said medium acts on the linkage to produce a mechanical output movement from said linkage; a further chamber containing hydraulic fluid and arranged such that the expansion of said medium pressurises the hydraulic fluid in the chamber; and 10 a hydraulic fluid output for said chamber, whereby the actuator can provide a mechanical conk ol output and/or a pressurised hydraulic fluid output for actuation of a control device.

For a better understanding of the present invention reference will now be made 1 S to the accompanying drawings in which, by way of example: Fig 1 shows a diagrammatic cross-section of a thermal actuator with linear mechanical output, as described in prior patent GB2328492; 20 Pig 2 shows a diagrammatic cross-section of a thermal actuator similar to that of Pig. 1 but modified so as to be able to provide a pressurised hydraulic output; Pig. 3 shows a diagrammatic cross-section of a thermal actuator, similar to that of Pig. 2, capable of providing both a linear mechanical output and a pressurized 25 hydraulic output; Fig 4 shows, diagrammatically, the actuator of Fig. 2 applied to control the operation of a valve; and 30 Pig 5 shows, diagrammatically, the actuator of Fig. 2 applied to control the operation of valves in a sub-sea well.

In the various figures, for ease of understanding, like or corresponding pails are given the same references.

Fig 1 shows the known actuator of British patent GB2328492 in its nonactuated 5 condition. This actuator comprises a hollow cylindrical body part 1, having a sealing end-closure plate 2, at the left hand end in the drawing, and lacing co-axially coupled to or integral with a further hollow cylindrical body part 3, of smaller cross-section, at the right hand end. The inner space of the cylindrical body 1 constitutes a cylinder 4 incorporating a floating piston 5 and an electric heating element 6, which can be lO supplied with electric power, via a connector 7. The cylinder 4, bounded by the closure plate 2 and piston 5, contains a material, for example wax, which is such that it will expand under the application of electric heating current to the element 6 and which, in so doing, will force the piston 5 to the right. Wax is very suitable for the material to be used in cylinder 4 since, when it is heated and transitions from a solid to 15 a liquid, it expands significantly As shown, a seal 8 is provided between the piston 5 and the inner wall of the cylinder. To the light of the piston 5 is a perforated flange 9 on the end of a shaft 10.

This shaft extends to the right through the further cylindrical body 3 and carries a 20 piston 11, having a seal 12 between it and the inner wall of the body. Between the left hand end of the body 3 and flange 9 is a spring 13, surrounding and coaxial with the shaft 1O. This spring is tensioned so as to urge the flange 9 towards the piston 5. To the light of the piston 11, the shaft 10 has a threaded section 14 and a latch 15 is provided on the inner surface of the body 3. Bellows 16 sun ound the junction 25 between the cylindrical bodies 1 and 3 and are connected in a sealing fashion to both.

A bore 17 extends between the right hand inside end of body 1 and the inside of the bellows and anti corrosion lubricating oil fills the space 18 in the bodies between the pistons 5 and 1 1, the bore 17 and the inside of the bellows 16. A flange 9 position sensing detector 19 is also provided on the cylindrical body 1.

In operation, when the wax or other material in cylinder 4 is heated by the element 6, it expands and moves the piston 5, and thus flange 9 on the shaft 10, to the fight (in the drawing) against the pressure of the spring 13. As the piston S moves to the fight, the excess lubricating oil, resulting from the change of geometry of the 5 cavity 18, exits via the bore 17 into the bellows 16. The position of the flange 9 is sensed by the detector 19 and, when sufficient movement of the flange 9 for valve actuation is achieved, the latch 15, typically a rotary solenoid operated type, is energised and clamps the shaft 10 at a position on its threaded section 14. At this stage, power can be removed from the heating element 6, leaving only the relatively 10 small power consumed by the latch 15 to hold the shaft 10 in the actuated position. As the material in the cylinder 4 then cools, it contracts and the piston 5 moves to the left with lubricating oil flowing back from the bellows 16 and through the perforated flange 9 to fill the increasing space between piston 5 and the flange. The output end of the shaft 10 is, typically, attached to the operating mechanism of a valve (not 15 shown) such that at the end of the actuating heating sequence, described above, the valve operating position is switched over.

After piston 5 has returned to the left through cooling and resolidifying of the wax in space 4, to return the valve to its former non-actuated position the power to the 20 latch 15 is removed, whereupon the shaft 10 returns to the left to its original position, under the force of the compressed spring 13, and the pressure of the shaft 10 on the valve operating mechanism is removed. As mentioned, the bellows 16 expand and contract, as necessary, to take up or return oil to the cavity 18 during movement of piston 5. As described in the prior patent, cooling means could also be provided in 25 cylinder 4 to enable more rapid cooling and solidifying of the wax.

Pig. 2 shows a modified version 100 of the actuator of Fig. 1. The actuator 100 of Fig. 2 comprises the basic mechanism of Fig 1, with the following modifications:

a) the second piston 11 of Fig. 1 is removed and is replaced by a piston 20, having a seal 21 between it and the inner surface of body 3, and being positioned to the right of the latch 15; b) the shaft 10 of Fig. 1 is reduced in length to finish inside the body 3 and the end of 5 body 3 is sealed with an end cap 22; c) the space 23, surrounding the end of shaft 10 and between the piston 20 and end cap 22, is filled with hydraulic fluid and an output orifice 24 fitted with a hydraulic coupling 25 is provided for this space 23; and d) an axial slot 26 is cut in the end of shaft 10.

The mode of operation of the electrical, thermally operated, actuator 100 of Fig. 2 is similar to the actuator of Fig. 1, except that the output produced is a hydraulic output in place of the mechanical output of shaft 10 of the Fig. 1 actuator. All of the components of the actuator which, in the drawing, are positioned to the left of piston 15 20, function exactly as in the actuator of Fig.1. However, the piston 20 and its seal 2 1 on shaft 10 and the cavity 23 in the actuator of Fig.2 form a hydraulic piston and cylinder with the pressurised hydraulic output of the cylinder space 23 being provided at orifice 24. Slot 26 facilitates the flow of fluid from the fight of the end of piston 10 back towards the space around shaft 10 adjacent the output orifice 24.

Coupling the hydraulic coupler 25 to a control input for a hydraulically operated valve enables the valve to be operated using the pressure of the hydraulic fluid in cylinder space 23. Movement of the shaft 10, by heating or cooling of the wax or other material in cylinder 4, is achieved electrically by feeding or cutting off 25 current to the heater 6, as described in relation to the operation of the actuator of Fig.1, so that the electrically controlled actuator can provide a hydraulic fluid pressure control output.

The result of these changes, is an electrical, thermally operated, hydraulic 30 output valve actuator. This can be used to operate, for example, existing hydraulically operated valves, without the need for a high pressure hydraulic supply from an

external source such as from the surface, via an expensive umbilical, in a sub sea fluid extraction well.

Fig. 3 shows an embodiment of the second aspect of the invention in the form 5 of an alternative modification of the actuator of Fig. 1, which produces a thermal actuator 200 capable of providing both a mechanical linear output and a hydraulic output. This modification is similar to that of Fig.. 2 except that, with the actuator 200, the shaft 10 is not shortened and, therefore, no end plate 22 is required. Instead, a seal 27 is provided between the inside of the cylinder 3 and shaft 10, to the right of 10 the space 23 at a position where the shaft 10 passes through a narrowed space to extend out of the actuator body cylinder 3.

These modifications result in a slightly more complicated and expensive actuator device 200 which can be operated electrically, in the same way as the 15 actuators of Figs. 1 and 2, but which can provide both a hydraulic output and a mechanical output. Use of such a device would enable conversion of the control of the valves of a well to take place in two stages. The first stage could retain the use of hydraulically controlled valves but with the control from the surface being electrically, not hydraulically linked signals. Actuator 200 then provides the hydraulic control 20 output for the valve control. After satisfactory experience with such an arrangement, the hydraulically controlled valves could, if desired, be replaced by mechanically controlled valves operated by the mechanical output of actuator 200.

Fig 4 illustrates the use of the electrically fed actuator 100 of Fig. 2 to replace 25 a high pressure hydraulic umbilical control line to control a hydraulic actuator 28 for a valve 29 in a production fluid extraction well. Although the actuator shown is the actuator 100 of Fig.2, the actuator 200 of Fig. 3 could equally well be used in this arrangement. An electrical supply to actuator 100, which is situated sub-surface in the region of or relatively close to the device to be controlled, via connection 7, replaces 30 the previously used high pressure hydraulic line. The output of actuator 100 is fed from actuator output connector 25 through hydraulic pipe 30 to the hydraulic actuator

28. A hydraulic fluid reservoir and non-return valve 31 is provided as a source of top up hydraulic fluid for the system. In operation, application of electric power to the heating element of the actuator 100 results, as explained with reference to Figs. 1 to 3, in hydraulic fluid being pumped through connector 25. This pressurised output is fed 5 through supply line 30 to the hydraulic actuator 28, which then actuates the valve 29.

A suitably large actuator 100 (Fig. 2) or 200 (Pig. 3) may be employed to provide the total pressurised hydraulic fluid requirements of a system, for operating all hydraulic devices in the system. This is illustrated, by way of example, in Fig. 5 for 10 the hydraulic supply of a sub-sea well tree. In this arrangement, the output connector 25 of a suitably large output capacity actuator 100 is connected via a hydraulic line 32 to a hydraulic accumulator 33 and a hydraulic manifold 34 which feeds, via channels therein, a multiplicity of directional control valves (DCVs) 35. Each DCV 35 controls the feed of hydraulic fluid to a hydraulic actuator 28 for operation of a sub-sea valve 15 SO, as required, to control the production of fluid from a fluid extraction well. In the arrangement illustrated in Fig. 5, only four such valves 30 are shown whereas in practice there may be many more. Likewise, for simplicity, only valves are shown as being controlled whereas, again, in practice the controlled devices may be other hydraulically operated devices, such as flow control chokes.

The DCVs 35 shown are electrically operated DCVs, which are operated by electrical control signals from a conventional sub sea control module (SEM) 36, via the electrical connections 37, which SEM 36 decodes data signals sent from a remote surface based production control system or PCS (not shown) via an electrical data 25 connection 38. The SEM 36 and the manifold 34 with its attached DCVs 35 are, as usual, housed in a sealed pod 39.

Thus when electric power is supplied to the electric thermal hydraulic pump or actuator 200, the output hydraulic pressure is stored in the hydraulic accumulator 26, 30 which provides hydraulic pressure to the manifold 27 and thus to any of the hydraulic actuators 29 of the devices 30, as required by the PCS commanding the SEM. The

use of the invention therefore removes the need for a costly hydraulic umbilical from the surface to operate the hydraulic devices which are in the sub-sea system.

It should be noted that, although this aspect of the invention has been 5 illustrated utilising the electric thermally operated actuator of Fig. 2 as a hydraulic pump, the control arrangement of this aspect of the invention may use any suitable electrical hydraulic pump, such as, for example, an electric motor driven conventional hydraulic pump, as the means for providing electrical operation of hydraulic actuators, particularly in sub-sea fluid extraction wells.

Claims

1. A method of actuating a hydraulic pressure operated control device of a sub-surface installation from a remote station, comprising: providing electrically operated hydraulic pressure output producing means positioned sub-surface in the region of the control device; providing a hydraulic coupling between a hydraulic output of said means and a hydraulic control input of said device; 10 providing an electrical energy operating supply from the remote station to said means; and cony oiling operation of the device by controlling the output hydraulic pressure from said means to said device by controlling the electrical energy supply from the remote station.

2. A method according to claim 1 wherein the electrically operated hydraulic pressure output producing means comprises: a chamber containing hydraulic fluid and having an output for the fluid; and a space containing thermal expansion medium and electrical heating means 20 for heating said medium to cause it to expand; and the arrangement being such that expansion of said medium acts to reduce the size of said chamber so as to increase the pressure of the hydraulic fluid to provide pressurised hydraulic fluid at said output.

3. A method according to claim 2 wherein said hydraulic fluid chamber is a 25 cylinder, with the cylinder containing a piston which is movable by expansion of said medium.

4. A method according to claim 2 or 3 wherein said the,nal expansion medium Is wax.

5. A method according to claim 3 or claim 4 appended to claim 3 wherein,

/ said space includes a floating piston; said hydraulic pressure output producing means includes a mechanical linkage; said mechanical linkage is coupled to said piston contained in said cylinder; and 5 the arrangement is such that expansion of said medium moves said floating piston, which acts on the mechanical linkage to cause movement of said piston to pressuise the hydraulic fluid in the cylinder.

6. A method according to claim 5, wherein the hydraulic pressure producing 10 output means further includes a latch for said mechanical linkage arranged such that, after expansion of the medium to cause operation of the controlled device, the latch operates to hold the linkage to retain it in its operated position so that the electrical heating current can be removed and said medium contract whilst the hydraulic fluid remains pressuised to maintain operation of said device.

7. A method according to claim 6, wherein the latch is controlled by an electrical locking signal such that removal of the electrical locking signal, with said medium cooled down, allows the mechanical linkage to return to its starting position.

20

8. A method according to claim l, wherein said hydraulic pressure output producing means comprises any form of electrically operated hydraulic pump.

9. An electrically operated actuator, comprising: a chamber containing a thermal expansion medium; 25 an electric heater for heating said medium to cause it to expand; a mechanical linkage linked with said expansion medium chamber such that expansion of said medium acts on the linkage to produce a mechanical output movement from said linkage; a further chamber containing hydraulic fluid and arranged such that the 30 expansion of said medium pressuises the hydraulic fluid in the chamber; and a hydraulic fluid output for said chamber, whereby

the actuator can provide as desired a mechanical control output or a pressurised hydraulic fluid output for actuation of a control device.

10. An actuator according to claim 9, wherein: 5 said further chamber is a cylinder, with the cylinder containing a piston; said chamber includes a floating piston; said mechanical linkage is coupled to said piston contained in said cylinder; and the arrangement is such that expansion of said medium moves said floating 10 piston, which acts on the mechanical linkage to cause movement of said piston to pressurise the hydraulic fluid in the cylinder and to provide a mechanical movement output