WO2006061645A1

WO2006061645A1 - Plug installation and retrieval tool for subsea wells

Info

Publication number: WO2006061645A1
Application number: PCT/GB2005/004756
Authority: WO
Inventors: Craig Yerington Duell; David Knowles; Mark Tindal Carill Worsley
Original assignee: Fmc Technologies, Inc.
Priority date: 2004-12-10
Filing date: 2005-12-09
Publication date: 2006-06-15
Also published as: GB0427148D0

Abstract

A plug retrieval and installation tool comprises a housing (50) that is lowered on a lift line or riser and connected to subsea production equipment such as a tree (30) and wellhead housing (16) in use. A plug manipulator (70) which can be extended to install, or retracted to retrieve, a plug-type barrier (22), is detachably mounted to the housing so that it can be retrieved independently of the housing. In the event that the plug manipulator fails, it may therefore nevertheless still be detached from the housing and retrieved, for example by wireline, through a riser and suitable pressure control equipment. The plug (22) is retrieved from/installed in a tubing hanger profile (23) through the tree (30). The housing (50) may comprise an LRP (50), having selectively openable pressure containment facilities, through which the plug manipulator (70) may be removed. The installation tool eliminates the need for full-size intervention vessels or drilling rigs for plug retrieval/installation.

Description

PLUG INSTALLATION AND RETRIEVAL TOOL FOR SUBSEA WELLS

Field of the Invention

The present invention relates to apparatus for installing or extracting a plug from a subsea well. For brevity, the following description refers mainly to the installation and retrieval of tubing hanger plugs, but the invention may also be used to install or retrieve plugs and similar removable fluid barriers elsewhere in subsea well apparatus, for example in subsea Christmas trees or tree caps.

Background of the Invention

When completing and/or suspending subsea wells, it is necessary to plug the tubing passage and (where a suitable annulus valve is not present) optionally also the annulus passage in the well to provide barriers against the well pressure. When preparing the well for production, it is necessary to remove the tubing plug/suspension barrier, to allow the well fluids to flow into the production flowline.

To remove a plug from a well under pressure it is necessary to have complete control over the well. Usually, plugs have been removed through a riser and BOP system, to ensure complete control. This often necessitates a full size intervention vessel or a drilling platform. These are extremely costly. A need exists for cheaper methods of running or retrieving a plug type barrier in the bore of a Christmas tree/tubing hanger that do not depend on full-sized intervention vessels or drilling platforms, and which make maximum use of tried and tested existing forms of completion installation equipment.

In US Patent No. 6,719,059 there is described a plug retrieval and installation tool that is enclosed in a housing that can be lowered on a lift line and connected to the upper end of the tree. The connector, drive mechanism and an extendable plug-retrieval member are powered by an ROV. The disclosed tool is a fairly complex piece of equipment useful solely for plug installation or retrieval. Failure of the tool with the retrieval member in the extended configuration can also leave the tree in a vulnerable and potentially unsafe condition in which flow control valves in the tree's vertical production bore are obstructed.

The present invention seeks to mitigate or eliminate some or all of these disadvantages. Summary of the Invention

The present invention accordingly provides a plug retrieval and installation tool mountable in a housing that together with the tool is lowered towards and connected to subsea production equipment in use, for retrieval or installation of a removable fluid barrier; the tool comprising a plug manipulator which can be extended to install, or retracted to retrieve, the removable fluid barrier, characterised in that the plug manipulator in use is detachably mounted to the housing so that it can be retrieved independently of the housing. In the event that the plug manipulator fails, it may therefore nevertheless still be detached from the housing and retrieved, for example by wireline, through a riser and suitable pressure control equipment.

The housing may comprise a selectively openable/closeable pressure barrier through which the plug manipulator is removable from the housing.

The housing may comprise an (e.g. otherwise conventional) lower riser package (LRP).

The plug manipulator may comprise a linear actuator.

The plug manipulator may comprise a piston and cylinder, for example a multi-stage piston and cylinder, to enable a plug pick-up or setting tool to be stroked all the way through a vertical production passage in a tree and locate or retrieve a plug or similar fluid barrier in a tubing hanger positioned below the tree.

A penetrator may be used to provide a detachable hydraulic, electrical or other power/signal interface between the housing and the plug manipulator.

A position sensor may be provided for determination of the position of the plug manipulator. The signals from the position sensor may be communicated from the plug manipulator through the housing by a penetrator.

The plug manipulator may be detachably mounted in the housing by means of a penetrator assembly. The housing may include an emergency disconnect facility from the lift line to allow safe rig intervention if necessary. To this end the tool can be removed and re-run through a workover riser. If necessary, the tool can be fished by standard wireline methods through the workover riser, maintaining system pressure integrity.

In preferred embodiments, the present invention can be used for the independent installation and retrieval of subsea Christmas trees by safely installing and retrieving tubing hanger plugs from a rig system or independently from a light support vessel. By mounting the tool within a pressure containment body such as an LRP, the primary well control barriers can be above the tool within the LRP, not the Christmas tree or the plug manipulator.

The tool has universal running and retrieving capability for any plug and is not limited to any specific tubing hanger or plug design.

Preferred embodiments of the invention may meet some or all of the following objectives/provide some or all of the following advantages:

• It integrates a plug running and retrieval mechanism or manipulator inside a substantially standard LRP.

• This configuration provides full well control protection during all operations and incorporates the ability to re enter the assembly with a drilling rig work over riser system.

• The device may allow plug removal and plug installation in a wellhead / tubing hanger assembly.

• The assembly may include the ability to eliminate liquid hydrocarbons in the tool area by using a helium or nitrogen gas purge facility and allow gas venting to sea.

• The device may use a multi-port penetrator assembly for electrical and hydraulic fluid functions, e.g. as disclosed in US5941574, to provide control of the plug manipulator.

Brief description of the Drawings An illustrative embodiment of the invention will now be described with reference to the accompanying drawings, where: Figs. Ia and Ib together form a single drawing showing a sectional view of the plug manipulator mounted in an LRP and extending into a subsea Christmas tree on which the LRP is mounted; Fig. Ic shows the plug manipulator only, in the extended configuration, as in the preceding figures;

Figs. 2a and 2b respectively show the plug manipulator mounted in the LRP and the manipulator on its own, in both cases with the plug manipulator in its fully retracted configuration, Fig. 2a corresponding to a section on line HA -HA in Fig. Ib; Figs. 3a and 3b are enlarged sectional views of the plug manipulator retaining mechanism in the closed position;

Figs. 4a and 4b are enlarged section views of the plug manipulator retaining mechanism in the open position, and

Fig. 5 is a further enlarged view showing details of the penetrator and retaining mechanism in the closed or engaged position.

Description of the preferred Embodiments

Referring first to Fig. Ia, there is shown a wellhead assembly 10 that includes a conductor housing 12 that is located at the seafloor and from which there extends a large diameter conductor pipe 14 into the seabed. A high pressure wellhead housing 16 is landed and locked into the conductor housing. From this there extends a casing 18 into the well. The casing string 18 is cemented to the conductor pipe 14. The wellhead housing 16 has an upper profile 17 for a connector 20. Depending upon the circumstances, and as the well is drilled deeper, a number of further casing strings 18a, 18b may be installed in the well. Each further casing string 18a, 18b includes a corresponding casing hanger 19a, 19b that is landed and locked within the wellhead housing 16. To complete the well, the casings are perforated and a production tubing 22A installed in the well. In the embodiment shown in Fig. Ia, the tubing includes a tubing hanger 24 that is landed, locked and sealed within the wellhead housing 16.

After perforating and testing the well, a plug or similar barrier 22 is placed in a profile 23 in the tubing hanger 24 using a wireline running tool lowered through the drilling riser and BOP. When installed, the plug 22 contains the pressure that is within the tubing 22a. A downhole safety valve and the plug 22 together provide primary and secondary barriers for maintaining control over the well, as required by standard practice. The plug 22 has one or more seals (not shown) that seal within the production passage 22b in the tubing hanger and typically has a plurality of locking elements that will engage a mating groove in the profile 23.

If an annulus valve 25 is installed in the tubing hanger annulus passage 21, it will also be closed, but in any case the tubing annulus normally would have no pressure. If desired, where there is no tubing hanger annulus valve, a further plug (not shown) can be installed in a suitable profile (not shown) in the tubing hanger annulus passage 21, according to standard practice. With the well thus shut in, the BOP and drilling riser can now safely be removed to permit installation of the Christmas tree.

The christmas tree, generally designated 30, is landed on the wellhead housing 16 and locked to it with the connector 20. The christmas tree 30 has a production passage 32 with a laterally extending outlet 34. The production passage is aligned with the tubing hanger production passage 22b in fluid communication with the interior of tubing 22a. At least one valve 35 is arranged in the outlet 34 for controlling fluid flow from the well. Further valves

42, 44 are arranged in the production passage 32, one above and one below the production outlet 34. The christmas tree also includes an annulus passage 36 that via the tubing hanger annulus passage 21 communicates with the annular space 35 outside the tubing 22.

The christmas tree has an upper profile 38 for connecting equipment to the christmas tree. This may be a riser, a BOP or other equipment.

After installation of the tree 30, and before the well can be put into production, the plug 22 must be removed. Referring now to Figs. Ib, Ic, 2a and 2b, there is shown a plug manipulator 70 which is removably held in a pressure control device known as a Lower Riser Package 50, or LRP. The LRP 50 is lowered on a lift line or chain but has an upper flange 51 and adapter spool 53 enabling a riser to be connected if necessary. With the plug manipulator 70 removed, the LRP 50 can thus be run on a high pressure riser so as to fulfil its conventional uses. As shown, the LRP 50 lands on top of the tree 30 and has a connector 52 at its lower end, to be connected to the profile 38 on the tree. The LRP 50 has a through- going vertical annulus passage 57 in communication with the tree and with tubing hanger annulus passages 23, 21, and a through-going vertical production passage 59 in communication with the tree and with tubing hanger production passages 32, 22b. Disposed in the LRP production passage are grip seal rams 52, shear seal rams 54 and a gate valve 56, as are conventional. Between the rams are arranged opposing penetrator assemblies 58a, 58b to provide access from the outside of the LRP 50 for supply of hydraulic and electrical power to the plug manipulator 70. A split support ring assembly 60 is attached to the penetrator assemblies 58a, 58b as shown in Fig.2a and will be more fully described hereinafter.

Referring now to Figs. Ic and 2b there is shown plug manipulator 70. It consists of a multistage hydraulic actuator, comprising e.g. an outer cylinder 74 and a number of telescopically movable stems 71, 72, 73 that are operated by hydraulic pressure supplied through the penetrator assemblies to move the stems between their retracted position within cylinder 74, as shown in Figs. 2a and 2b, and an extended position, as shown in Figs. Ia and Ic A plug release and pick-up tool 75 is located at the lower end of stem 73 for retrieving plug 22. The mechanism for unlocking the plug is conventional and well known in the art.

Conversely, to set a plug 22 in the tubing hanger profile 23, a setting tool (not shown) can be attached to stem 73 in place of the release and pick-up tool 75.

As better shown in Fig. 3a and 5, the plug manipulator 70 has an upper part that terminates in a fishing neck 76. The upper part has a number of bores for engagement with stabs in the split ring assembly 60. A first bore 77 engages with an alignment pin 62. A hydraulic penetrator 64 is movable through a bore in the split ring part 60b into and out of engagement with a hydraulic bore 78 in the plug manipulator upper part. The bore 78 includes a circumferential groove 79, communicating with a hydraulic passage 65 in the penetrator 64 and passages 80, 81 in the plug manipulator 70 leading to the central void in the cylinder 74 and stems 71, 72 of the multistage hydraulic cylinder, as is well known in the art. A further penetrator (not shown) communicates in similar manner with a further hydraulic bore (not shown) and passages 82, 83a, 83b, 83c in the plug manipulator. The passages 83a, 83b, 83c are in fluid communication with each other via radial bores (not shown) and annular hydraulic chambers (not shown) defined between adjacent stems 73, 72; 72, 71, and between the stem 71 and cylinder 74. The multi-stage cylinder is therefore double acting, for extension or retraction of the pick-up tool 75 or setting tool, downwardly away from or upwardly towards the LRP 50. An electrical bore 85 is engaged by an electrical penetrator 61 to communicate signals from an electrical positioning system 84.

Referring now to Figs. 3a, 3b, 4a and 4b, the split ring assembly 60 includes two halves 60a, 60b that can be moved towards or away from the penetrator housing by ROV-operated actuators 67a, 67b. This will move the split ring assembly between open and closed positions. In the closed position, an inner circumferential lip 68 on the split ring 60 engages in a corresponding outer circumferential groove 69 around the manipulator 70 upper part, to hold and support the manipulator 70 within the LRP 50. Figs. 3a, 3b and 5 show the split ring in its normally closed position and Figs. 4a and 4b show the open position. The hydraulic penetrators are connected to a controls umbilical using hydraulic couplers. The electrical penetrator 61 is likewise connected to the controls umbilical using wet mate connectors.

In operation, the LRP 50 and plug manipulator 70 are assembled on the surface and the assembly tested. The LRP 50 is then lowered to the Christmas tree 30 and connected. To install the plug, the plug 22 and setting tool are attached to the lower stem 73 and extended into the plug profile 23 by supplying hydraulic fluid through the penetrator 64. The plug manipulator 70 extends downwardly, its lower end passing out of the open lower end of the LRP 50, through the tree vertical production passageway 32 and opened valves 44, 42, until the plug 22 seats and locks in the tubing hanger profile 23. To retrieve the plug, the manipulator 70 stems 71, 72, 73 are extended by supplying hydraulic fluid through the penetrator 64 so that the plug retrieving tool 75 can engage with the plug 22 through the open tree valves 42, 44 and release the plug 22 from the profile 23. A positioning system 84 is built into the plug tool to monitor the position of the plug when installing or retrieving a plug. When the plug has been successfully disengaged, the stems are made to retract by supplying hydraulic pressure to the passages 83a, 83b, 83c so that the plug 22 and the release and pickup tool 75 are drawn up into the LRP 50. Now the production valve 42 and swab valve 44 can be closed. The LRP 50 can now be disconnected and brought to the surface using a lift line. Should the need arise for disconnection while the tool is in operation, the lift line can be disconnected and the rams 54 and gate valve 56 closed to act as primary barriers. This will ensure complete control of the well even if the tool is stuck so that the tree valves 42, 44 cannot be closed.

Should the need arise to retrieve the plug manipulator 70 independently from the LRP, a workover riser can be connected to the top of the LRP 50. Suitable "fishing" equipment may be then lowered through the workover riser to connect onto the fishing neck profile 76. The penetrators 61, 64 etc. are retracted (disengaged) and the split ring 60 is then opened using the actuators 67a, 67b. This will disengage the lip 68 and alignment pin 62 from the plug manipulator 70, as shown in Figs. 4a and 4b and allow the plug manipulator 70 to be retrieved.

With this system, complete control of the well can be assured, even in emergency situations. The LRP 50 provides pressure containment after the plug has been removed and the well pressure acts on the tool.

With the plug manipulator 70 removed from the LRP 50, conventional wirelining/coil tubing intervention can be carried out allowing greater flexibility within the system.

The tool can be hydraulically, manually or electrically operated.

The exact location of the plug setting or release and pick-up tool 75 can be determined either using remote linear position measurement from known datum or from hydraulic monitoring.

Regardless of failure mode, (i.e. even when the plug manipulator 70 is extended and stuck across Christmas tree valves omitting them as barriers), system design maintains the ability to close two barriers above the Christmas tree, i.e. within the LRP 50, to allow the plug manipulator 70 to be recovered by safe rig intervention. Alternatively, the system design has the capacity to allow the plug manipulator 70 and plug 22 to be recovered through the workover riser, whilst maintaining barriers, allowing subsequent closing of Christmas tree gate valves to maintain the two well barrier requirement. The manipulator 70 cylinder system can also be releasably supported within the LRP by any other suitable means, as an alternative to the penetrator support mechanism. The cylinder system can be replaced by any other suitable linear actuator.

After plug venting and removal from the tubing hanger 24, an inert medium, (e.g. helium gas) may be introduced from an umbilical or accumulators to displace hydrocarbon liquid down below the Christmas tree swab valve 44, to avoid any environmental spill when disconnecting the LRP 50. In addition, this allows for safer system retrieval without the potential for trapped liquid hydrocarbons within the LRP 50. The helium will mix with any hydrocarbon gas present, whereas the fluid hydrocarbons will move down the well. In this case, vented gas will include helium and hydrocarbon gas.

The plug manipulator 70 may be run independently through a workover riser on wire for installation into the LRP. A dedicated running tool that includes an orientation helix could position the plug manipulator 70 within the LRP 50 using the alignment pin 62 as an orientation / positioning feature.

Claims

1. A plug retrieval and installation tool mountable in a housing that together with the tool is lowered towards and connected to subsea production equipment in use, for retrieval or installation of a removable fluid barrier; the tool comprising a plug manipulator which can be extended to install, or retracted to retrieve, the removable fluid barrier, characterised in that the plug manipulator in use is detachably mounted to the housing so that it can be retrieved independently of the housing.

2. A plug retrieval and installation tool as defined in claim 1, in combination with said housing, in which the housing comprises a selectively openable/closeable pressure barrier through which the plug manipulator is removable from the housing.

3. A combination as defined in claim 2, in which the housing comprises a lower riser package (LRP).

4. A plug retrieval and installation tool or combination as defined in any preceding claim, in which the plug manipulator comprises a linear actuator.

5. A plug retrieval and installation tool or combination as defined in claim 4, in which the plug manipulator comprises a piston and cylinder.

6. A plug retrieval and installation tool or combination as defined in claim 4, in which the plug manipulator comprises a multi-stage piston and cylinder.

7. A plug retrieval and installation tool or combination as defined in any preceding claim, in which a penetrator is used to provide a detachable hydraulic, electrical or other power/signal interface between the housing and the plug manipulator.

8. A plug retrieval and installation tool or combination as defined in any preceding claim, in which a position sensor is provided for determination of the position of the plug manipulator.

9. A plug retrieval and installation tool or combination as defined in claim 8, in which the signals from the position sensor are communicated from the plug manipulator through the housing by a penetrator.

10. A plug retrieval and installation tool or combination as defined in any preceding claim, in which the plug manipulator is detachably mounted in the housing by means of a penetrator assembly.

1 1. A plug retrieval and installation tool or combination as defined in any preceding claim, which is lowered on a lift line, towards the subsea equipment.

12. A plug retrieval and installation tool or combination as defined in claim 11, in which the housing includes an emergency disconnect facility from the lift line.

13. A plug retrieval and installation tool or combination as defined in any preceding claim, which is lowered on a riser, towards the subsea equipment.

14. A plug retrieval and installation tool or combination as defined in any preceding claim, in which the plug manipulator can be extended from within the housing to install, or retracted into the housing to retrieve, the removable barrier.

15. A plug retrieval tool and installation tool or combination as defined in any preceding claim, comprising a supply of an inert medium for displacement of hydrocarbon liquid in the housing.