Plug installation system for deep water subsea wells
A plug retrieval and installation tool is used with a subsea well having a production tree, a tubing hanger, a passage that extends vertically through the tubing hanger and the tree, and a plug located within a plug profile in the passage within the tubing hanger. The plug retrieval device has a housing and connector that is lowered on a lift line onto the upper end of the tree. An axially extendible stem in the housing is moved with hydraulic fluid controlled by an ROV into the production passage of the tubing hanger. An installation and retrieval member mounted to the stem engages the plug and pulls it upwardly in the passage while the stem is being moved upward, and pushes the plug downward to install the plug while the stem is being moved downward. The connector, drive mechanism and retrieval member are powered by an ROV.
This nonprovisional application is a continuation of and claims the benefit and priority of co-pending, nonprovisional patent application U.S. Ser. No. 10/783,168, filed on Feb. 20, 2004, which claimed the benefit of provisional patent application U.S. Ser. No. 60/514,284, filed on Oct. 24, 2003, and was also a continuation-in-part patent application that also claimed the benefit of then co-pending, non-provisional patent application U.S. Ser. No. 10/340,122, filed on Jan. 10, 2003, now U.S. Pat. No. 6,719,059, which is hereby incorporated by reference in its entirety.
BACKGROUND OF THE INVENTION1. Field of the Invention
This invention relates in general to subsea well installations and in particular to a system for installing and retrieving a plug from a tubing hanger.
2. Background of the Invention
A typical subsea wellhead assembly has a high pressure wellhead housing supported in a lower pressure wellhead housing and secured to casing that extends into the well. One or more casing hangers land in the wellhead housing, the casing hanger being located at the upper end of a string of casing that extends into the well to a deeper depth. A string of tubing extends through the casing for production fluids. A Christmas or production tree mounts to the upper end of the wellhead housing for controlling the well fluid. The production tree is typically a large, heavy assembly, having a number of valves and controls mounted thereon.
One type of tree, sometimes called “conventional”, has two bores through it, one of which is the production bore and the other is the tubing annulus access bore. In this type of wellhead assembly, the tubing hanger lands in the wellhead housing. The tubing hanger has two passages through it, one being the production passage and the other being an annulus passage that communicates with the tubing annulus surrounding the tubing. Access to the tubing annulus is necessary to circulate fluids down the production tubing and up through the tubing annulus, or vice versa, to either kill the well or circulate out heavy fluid during completion. After the tubing hanger is installed and before the drilling riser is removed for installation of the tree, plugs are temporarily placed in the passages of the tubing hanger. The tree has isolation tubes that stab into engagement with the passages in the tubing hanger when the tree lands on the wellhead housing. This type of tree is normally run on a completion riser that has two strings of conduit. In a dual string completion riser, one string extends from the production passage of the tree to the surface vessel, while the other extends from the tubing annulus passage in the tree to the surface vessel. It is time consuming, however to assemble and run a dual string completion riser. Also, drilling vessels may not have such a completion riser available, requiring one to be supplied on a rental basis.
In another type of tree, sometimes called “horizontal” tree, there is only a single bore in the tree, this being the production passage. The tree is landed before the tubing hanger is installed, then the tubing hanger is lowered and landed in the tree. The tubing hanger is lowered through the riser, which is typically a drilling riser. Access to the tubing annulus is available through choke and kill lines of the drilling riser. The tubing hanger does not have an annulus passage through it, but a bypass extends through the tree to a void space located above the tubing hanger. This void space communicates with the choke and kill lines when the blowout preventer is closed on the tubing hanger running string. In this system, the tree is run on drill pipe, thus prevents the drilling rig derrick of the floating platform from being employed on another well while the tree is being run.
In another and less common type of wellhead system, a concentric tubing hanger lands in the wellhead housing in the same manner as a conventional wellhead assembly. The tubing hanger has a production passage and an annulus passage. However, the production passage is concentric with the axis of the tubing hanger, rather than slightly offset as in conventional tubing hangers. The tree does not have a vertical tubing annulus passage through it, thus a completion riser is not required. Consequently the tree may be run on a monobore riser. A tubing annulus valve is located in the tubing hanger since a plug cannot be temporarily installed and retrieved from the tubing annulus passage with this type of tree.
In the prior art conventional and concentric tubing hanger types, the tubing hanger is installed before the tree is landed on the wellhead housing. The tubing is typically run on a small diameter riser through the drilling riser and BOP. Before the drilling riser is disconnected from the wellhead housing, a plug is installed in the tubing hanger as a safety barrier. The plug is normally lowered on a wireline through the small diameter riser. Subsequently, after the tree is installed, the plug is removed through the riser that was used to install the tree.
SUMMARY OF THE INVENTIONIn this invention, a lift line deployable apparatus is provided for installing or retrieving a plug in a passage of a subsea wellhead assembly. The apparatus has a tubular housing that sealingly connects to an upper end of a subsea wellhead assembly. An axially movable stem is carried in the housing for movement between a retracted position and an extended position in the passage. A retrieval member is mounted to the stem for engaging the plug while in the extended position, and retrieving the plug as the stem is moved to the retracted position.
Preferably, the mechanism for connecting the housing to the upper end of the subsea wellhead assembly is powered by an ROV. Also, the drive mechanism for the stem is preferably controlled and powered by an ROV. Further, the retrieval member preferably is hydraulically driven by the ROV.
BRIEF DESCRIPTION OF THE DRAWINGS
Overall Structure of Subsea Wellhead Assembly
Referring to
An inner or high pressure wellhead housing 21 lands in and is supported within the bore of outer wellhead housing 13. Inner wellhead housing 21 is located at the upper end of a string of casing 23 that extends through casing 17 to a greater depth. Inner wellhead housing 21 has a bore 25 with at least one casing hanger 27 located therein. Casing hanger 27 is sealed within bore 25 and secured to the upper end of a string of casing 29 that extends through casing 23 to a greater depth. Casing hanger 27 has a load shoulder 28 located within its bore or bowl.
In this embodiment, a tubing hanger 31 is landed, locked, and sealed within the bore of casing hanger 27. Referring to
Referring to
As shown in
Referring again to
Tree and Wellhead Housing Internal Connector
Tree 39 includes a connector assembly for securing it to wellhead housing 21. The connector assembly includes a connector body 45 that has a downward facing shoulder 47 that lands on rim 37. Connector body 45 is rigidly attached to tree 39. A seal 49 seals between rim 37 and shoulder 47. Connector body 45 also extends downward into wellhead housing 21. A locking element 51 is located at the lower end of connector body 45 for engaging profile 35. Locking element 51 could be of a variety of types. In this embodiment; locking element 51 comprises an outer split ring that has a mating profile to groove 35. A plurality of dogs 53 located on the inner diameter of locking element 51 push locking element 51 radially outward when moved by a cam sleeve 55. Cam sleeve 55 moves axially and is hydraulically driven by hydraulic fluid supplied to a piston 57.
The connector assembly has an extended or retainer portion 59 that extends downward from connector body 45 in this embodiment. Extended portion 59 is located above and secured to orientation sleeve 46. A collar 60 is threaded to the outer diameter of extended portion 59 for retaining locking element 51 and dogs 53 with connector body 45. Alternately dogs 53 could be used to engage profile 35 and locking element 51 omitted. In that case, windows could be provided for the dogs in connector body 45, and extended portion 59 and collar 60 would be integrally formed with connector body 45.
Referring to
At least one valve is mounted to production tree 39 for controlling fluid flow. In the preferred embodiment, the valves includes a master valve 63 and a swab valve 65 located in production passage 41. A safety shutoff valve 67 is mounted to port 41a. The hydraulic actuator 68 for safety shutoff valve 67 is shown. Valves 63 and 65 may be either hydraulically actuated or mechanically actuated (typically by ROV).
Referring again to
Tubing Annulus Access
A tubing annulus valve 89 is mounted in tubing annulus passage 83 to block tubing annulus passage 83 from flow in either direction when closed. Referring to
A shuttle sleeve 101 is reciprocally carried in tubing annulus passage 83. While in the upper closed position shown in
An outward biased split ring 105 is mounted to the outer diameter of sleeve 101 near its upper end. Split ring 105 has a downward tapered upper surface and a lower surface that is located in a plane perpendicular to the axis of tubing annulus passage 83. A mating groove 107 is engaged by split ring 105 while sleeve 101 is in the upper, closed position. Split ring 105 snaps into groove 107, operating as a detent or retainer to prevent downward movement of sleeve 101.
Engaging member 109 is secured to the lower end of an actuator 117, which is mounted in tree 39. Actuator 117 is a hollow, tubular member with open ends reciprocally carried in a tubing annulus passage 118 in tree 39 (
When actuator 117 is moved to the lower position, engaging member 109 engages and pushes sleeve 101 from the closed position to the open position.
Running tool 111 has conventional features for running tubing hanger 31, including setting a seal between tubing hanger 31 and bore 25 of wellhead housing 21 (
Orientation
Referring to
Ring 125 is normally installed on outer wellhead housing 13 at the surface before outer wellhead housing 13 is lowered into the sea. Arm 133 will be attached to arm bracket 131 below the rig floor but at the surface. After outer wellhead housing 13 is installed at the sea floor, if necessary, an ROV may be employed later in the subsea construction phase to rotate ring 125 to a different orientation.
A BOP (blowout preventer) adapter 139 is being shown lowered over inner or high pressure housing 21. BOP adapter 139 is used to orient tubing hanger 31 (
BOP adapter 139 has a plurality of dogs 145 that are hydraulically energized to engage an external profile on inner wellhead housing 21. BOP adapter 139 also has seals (not shown) that seal its bore to bore 25 of wellhead housing 21. A helical orienting slot 147 is located within the bore of BOP adapter 139. Slot 147 is positioned to be engaged by a mating pin or lug on running tool 111 (
Once BOP adapter 139 has oriented tubing hanger 31 (
The safety shutoff valve 67 of tree 39 is connected to a flow line loop 149 that leads around tree 39 to a flow line connector 151 on the opposite side as shown in
Plug Retrieval and Installation
After tree 39 is installed, a plug 159 (
Preferably, rather than utilizing wireline inside a workover riser, as is typical, an ROV deployed plug tool 165 is utilized. Plug tool 165 does not have a riser extending to the surface, rather it is lowered on a lift line. Plug tool 165 has a hydraulic or mechanical stab 167 for engagement by ROV 169. The housing of plug tool 165 lands on top of tree mandrel 81. A seal retained in plug tool 165 engages a pocket in mandrel 81 of tree 39. When supplied with hydraulic pressure or mechanical movement from ROV 169, a connector 171 will engage mandrel 81 of tree 39. Similarly, connector 171 can be retracted by hydraulic pressure or mechanical movement supplied from ROV 169. Once connected, any pressure within mandrel 81 is communicated to the interior of the housing of plug tool 165. Prior to connection, valve 65 would normally be closed and plug 159 would also provide a pressure barrier.
Plug tool 165 has an axially movable stem 173 that is operated by hydraulic pressure supplied to a hydraulic stab 174. Stem 173 moves from a retracted position, wholly within the housing of plug tool 165 to an extended position in the proximity of plug profile 157. A retrieving tool 175 is located on the lower end of stem 173 for retrieving plug 159. Similarly, a setting tool 177 may be attached to stem 173 for setting plug 159 in the event of a workover that requires removal of tree 39. Setting tool 177 may be of a variety of types and for illustration of the principle, is shown connected by shear pin 179 to plug 159. Once locking elements 163 have engaged profile 157, an upward pull on stem 173 causes shear pin 179 to shear, leaving plug 159 in place.
Retrieving tool 175, shown in
Collet 187 and sleeve 185 are joined to a piston 191. Piston 191 is supplied with hydraulic fluid from ROV 169 (
Field Development
Platform 195 also preferably has a crane or lift line winch 207 for deploying a lift line 209. Lift line 207 is located near one side of platform 195 while derrick 197 is normally located in the center. Optionally, lift line winch 207 could be located on another vessel that typically would not have a derrick 197. In
Drilling and Completion Operation
In operation, referring to
The operator then drills the well to a deeper depth and installs casing 117, if such casing is being utilized. Casing 117 will be cemented in the well. The operator then drills to a deeper depth and lowers casing 23 into the well. Casing 23 and high pressure wellhead housing 21 are run on drill pipe and cemented in place. No orientation is needed for inner wellhead housing 21. The operator may then perform the same steps for two or three adjacent wells by repositioning the drilling platform 195 (
The operator connects riser 201 (
The operator is then in position to install tubing hanger 31 (
The operator then attaches drilling riser 201, including BOP 203, (
After tubing hanger 31 has been set, the operator may test the annulus valve 89 by stroking actuator 117′ upward, disengaging engaging member 109 from sleeve 101 as shown in
The operator then applies fluid pressure to passage 118′ within running tool 111. This may be done by closing the blowout preventer in drilling riser 201 on the small diameter riser above running tool 111. The upper end of passage 118′ communicates with an annular space surrounding the small diameter riser below the blowout preventer in drilling riser 201. This annular space is also in communication with one of the choke and kill lines of drilling riser 201. The operator pumps fluid down the choke and kill line, which flows down passage 118′ and acts against sleeve 101. Split ring 105 prevents shuttle sleeve 101 from moving downward, allowing the operator to determine whether or not seals 99 on valve head 97 are leaking.
The well may then be perforated and completed in a conventional manner. In one technique, this is done prior to installing tree 39 by lowering a perforating gun (not shown) through the small diameter riser in the drilling riser 201 (
If desired, the operator may circulate out heavy fluid contained in the well before perforating. This may be done by opening tubing annulus valve 89 by stroking actuator 117′ and engaging member 109′ downward. Engaging member 109′ releases split ring 105 from groove 107 and pushes sleeve 101 downward to the open position of
After perforating and testing, the operator will set plug 159 (
The operator then retrieves running tool 111 (
The operator is now in position for running tree 39 on lift line 209 (
Referring to
Referring to
For a workover operation that does not involve pulling tubing 33, a light weight riser with blowout preventer may be secured to tree mandrel 81. An umbilical line would typically connect the tubing annulus passage on tree 39 to the surface vessel. Wireline tools may be lowered through the riser, tree passage 41 and tubing 33. The well may be killed by stroking actuator 117 (
For workover operations that require pulling tubing 33, tree 39 must be removed from wellhead housing 21. A lightweight riser would not be required if tubing hanger plug 159 (
The invention has significant advantages. The plug tool allows a plug to be retrieved from the tubing hanger without the need for a riser extending to the surface. Since a riser is not needed, the tree can be efficiently run on a lift line. The plug tool is easily installable on a lift line. Its functions of connecting, moving the stem, and engaging the plug are accomplished by power from an ROV, avoid the need for an umbilical to the surface for the plug tool. The plug tool can also set a plug in the tubing hanger in the event a plug is needed.
While the invention has been shown in only one of its forms, it should be apparent to those skilled in the art that it is not so limited but is susceptible to various changes without departing from the scope of the invention.
Claims
1-18. (canceled)
19. An apparatus for retrieving a plug in a passage of a subsea wellhead assembly, comprising:
- a housing adapted to be sealingly connected to an upper end of a subsea wellhead assembly;
- an axially movable stem carried in the housing for movement between a retracted position and an extended position into the passage; and
- a retrieving member mounted to the stem to engage the plug while in the extended position, and to retrieve the plug as the stem is moved to the retracted position.
20. The apparatus according to claim 19, further comprising a drive mechanism for moving the stem between the engaged and retracted positions, the drive mechanism adapted to be powered by an ROV.
21. A method for retrieving a plug in a passage of a subsea wellhead assembly, comprising:
- (a) mounting an axially movable stem having a retrieval member thereon within a housing;
- (b) lowering the housing on a lift line and sealingly connecting the housing to an upper end of a subsea wellhead assembly while the stem is in a retracted position;
- (c) axially moving the stem downward into the passage and causing the retrieval member to engage the plug; and
- (d) moving the stem upward along with the plug.
22. The method according to claim 21, wherein step (b) further comprises providing a subsea tree that forms an upper portion of the subsea wellhead assembly, and wherein the housing sealingly connects to the subsea wellhead assembly by sealingly connecting to an upper end of the subsea tree.
23. The method according to claim 21, wherein step (b) further comprises providing a subsea tree connected to a lower end of the housing, and wherein the housing and the subsea tree are lowered on the lift line, the housing being sealingly connected to the subsea wellhead assembly when the subsea tree sealingly connects to the subsea wellhead assembly.
24. A method for retrieving a plug from a passage of a subsea wellhead assembly, comprising the steps of:
- providing a retrieval device which comprises an extendable stem and a retrieval tool which is attached to the stem and removably connectable to the plug;
- securing the retrieval device to the subsea wellhead assembly;
- retrieving the plug from the passage using the retrieval device; and
- removing the retrieval device from the subsea wellhead assembly with the plug connected to the retrieval device.
25. The method according to claim 24, further comprising the step of sealing the retrieval device to the subsea wellhead assembly prior to the plug retrieving step; wherein the retrieval device forms a pressure-containing barrier between the passage and a surrounding environment.
26. The method according to claim 24, wherein the retrieval device comprises an ROV operated subsea tool.
27. The method according to claim 24, wherein the retrieval device is deployable from a surface facility on at least one of a cable and a drill string.
28. The method according to claim 24, further comprising the step of retrieving the retrieval device to a surface facility with the plug connected to the retrieval device.
29. The method according to claim 28, wherein the step of retrieving the retrieval device is performed with at least one of a cable and a drill string which is deployed from the surface facility.
30. The method according to claim 24, wherein the plug retrieving step comprises the steps of extending the stem into engagement with the plug, connecting the retrieval tool to the plug and retracting the plug from the passage.
31. A method for installing a plug in a passage of a subsea wellhead assembly, comprising:
- providing an installation device which comprises an extendable stem and an installation tool which is attached to the stem and removably connectable to the plug;
- connecting the plug to the installation tool;
- securing the installation device to the subsea wellhead assembly; and
- installing the plug in the passage using the installation device.
32. The method according to claim 31, further comprising the step of sealing the installation device to the subsea wellhead assembly prior to the plug installing step; wherein the installation device forms a pressure-containing barrier between the passage and a surrounding environment.
33. The method according to claim 31, wherein the installation device comprises an ROV operated subsea tool.
34. The method according to claim 31, further comprising the step of lowering the installation device from a surface facility on at least one of a cable and a drill string.
35. The method according to claim 31, further comprising the step of retrieving the installation device to a surface facility after the plug installing step.
36. The method according to claim 35, wherein the step of retrieving the installation device is performed with at least one of a cable and a drill string which is deployed from the surface facility.
37. The method according to claim 35, wherein the step of retrieving the installation device is performed with at least one of a cable and a drill string which is deployed from a facility located above the tree.
38. The method according to claim 31, wherein the plug installing step comprises the steps of extending the stem to position the plug in the passage, securing the plug to the passage and disconnecting the plug from the installation tool.
39. A method for installing a subsea wellhead assembly over a well bore, the subsea wellhead assembly comprising a wellhead which is installed at an upper end of the well bore; a tubing hanger which comprises at least one tubing hanger production passage, and a subsea tree which comprises at least one tree bore, the method comprising the steps of:
- (a) installing the tubing hanger in the wellhead;
- (b) installing a plug in the production passage;
- (c) installing the subsea tree over the wellhead with the tree bore in alignment with the tubing hanger bore;
- (d) providing a retrieval device which comprises an extendable stem and a retrieval tool which is attached to the stem and removably connectable to the plug;
- (e) with the retrieval device secured to the subsea wellhead assembly above the subsea tree, retrieving the plug from the production passage through the tree bore using the retrieval device.
40. The method according to claim 39, further comprising the step of sealing the retrieval device to the subsea wellhead assembly prior to the plug retrieving step; wherein the retrieval device forms a pressure-containing barrier between the tubing hanger bore and a surrounding environment.
41. The method according to claim 39, wherein the retrieval device comprises an ROV operated subsea tool.
42. The method according to claim 39, further comprising the step of lowering the subsea tree from a surface facility to the wellhead on at least one of a cable and a drill string;
43. The method according to claim 39, further comprising the step of securing the retrieval device to the subsea tree after the subsea tree is installed over the wellhead.
44. The method according to claim 39, further comprising the step of securing the retrieval device to the subsea tree prior to landing the subsea tree on the wellhead.
45. The method according to claim 44, further comprising the step of lowering the retrieval device and the subsea tree from a surface facility to the wellhead on at least one of a cable and a drill string.
46. The method according to claim 39, further comprising the step of removing the retrieval device from the subsea wellhead assembly with the plug connected to the retrieval device.
47. The method according to claim 46, further comprising the step of retrieving the retrieval device to a surface facility with the plug connected to the retrieval device.
48. The method according to claim 47, wherein the step of retrieving the retrieval device is performed with at least one of a cable and a drill string which is deployed from the surface facility.
49. The method according to claim 39, wherein the wellhead is installed within an outer housing and the method further comprises the steps of: mounting a guide assembly to the outer housing; and orienting the tubing hanger relative to the guide assembly.
50. The method according to claim 49, wherein the step of orienting the tubing hanger relative to the guide assembly comprises the steps of: landing a tubing hanger orientation tool on the wellhead; orienting the tubing hanger running tool relative to the guide assembly; and orienting the tubing hanger relative to the tubing hanger running tool.
51. The method according to claim 50, further comprising the step of orienting the subsea tree relative to the guide assembly.
52. The method according to claim 39, wherein the wellhead comprises a wellhead housing having a tubing spool positioned thereon, and in step (a) the tubing hanger is installed within one of the wellhead housing and the tubing spool.
53. A method for retrieving a plug from a passage of a subsea wellhead assembly, comprising:
- providing an ROV operated subsea tool (ROT) which comprises an extendable stem and a retrieval tool which is attached to the stem and removably connectable to the plug;
- securing and sealing the ROT to the subsea completion system;
- and retrieving the plug from the bore using the ROT.
54. An apparatus for installing a subsea wellhead assembly comprising an outer housing which is positioned on the sea floor, an wellhead housing which is landed in the outer housing, at least one casing hanger which is connected to a corresponding casing string, a tubing hanger which is connected to a production tubing string and which includes at least one tubing hanger production passage, and a subsea tree which is installed over the wellhead housing and which includes at least one production bore that is aligned with the tubing hanger production passage, the apparatus comprising:
- an ROV operated subsea tool (ROT) which comprises an elongated body; a bore which extends longitudinally through the body; an elongated stem which is positioned in the bore; a plug tool which is connected to an end of the stem; means for removably connecting the ROT to the subsea tree; and means for moving the stem through the bore to thereby move the plug tool through the production passage and into engagement with a plug in the production passage;
- and at least one of a cable and a drill string which is connected to the ROT and by which the ROT and the subsea tree are lowered to the wellhead housing.
55. A method for installing a subsea wellhead assembly comprising an outer housing which is positioned on the sea floor, a wellhead housing which is landed in the outer housing, at least one casing hanger which is connected to a corresponding casing string, a tubing hanger which is connected to a production tubing string and which includes at least one tubing hanger production passage, and a subsea tree which is installed over the wellhead housing and which includes at least one production bore, the method comprising the steps of:
- (a) installing the outer housing on the sea floor;
- (b) landing the wellhead housing in the outer housing;
- (c) securing a blowout preventer (BOP) to the wellhead housing;
- (d) landing the casing hanger in the wellhead housing through the BOP;
- (e) connecting the tubing hanger to a tubing hanger running tool (THRT);
- (f) landing the tubing hanger in the wellhead housing or the casing hanger through the BOP;
- (g) installing a wireline plug in the production passage through the THRT;
- (h) retrieving the THRT;
- (i) retrieving the BOP;
- (j) securing an ROV operated subsea tool (ROT) to the subsea tree;
- (k) landing the subsea tree on the wellhead housing; and
- (l) retrieving the wireline plug from the production passage using the ROT.
56. The method according to claim 55, wherein:
- in step (b) the wellhead housing further comprises a tubing spool positioned thereon, and
- in step (f) the tubing hanger is landed through the BOP within one of the wellhead housing, the tubing spool, and the casing hanger.
57. A method for installing a plug in a bore of a subsea wellhead assembly, the method comprising the steps of:
- providing an ROV operated subsea tool (ROT), which comprises an extendable stem and an installation tool which is attached to the stem and removably connectable to the plug;
- connecting the plug to the installation tool;
- securing and sealing the ROT to the subsea completion system; and
- installing the plug in the bore using the ROT.
58. A method for installing a subsea wellhead assembly, the subsea wellhead assembly comprising a wellhead which is installed at an upper end of the well bore; a tubing hanger which comprises at least one tubing hanger production passage, and a subsea tree which comprises at least one tree bore, the method comprising the steps of:
- (a) installing the tubing hanger in the wellhead;
- (b) installing a plug in the production passage;
- (c) installing the subsea tree over the wellhead with the tree bore in alignment with the production passage;
- (d) providing an ROV operated subsea tool (ROT) which comprises an extendable stem and a retrieval tool which is attached to the stem and removably connectable to the plug;
- (e) with the ROT secured to the subsea completion system above the subsea tree, retrieving the plug from the production passage through the tree bore with the ROT.
59. The method according to claim 58, wherein the wellhead comprises a wellhead housing having a tubing spool positioned thereon, and in step (a) the tubing hanger is installed within one of the wellhead housing and the tubing spool.
Type: Application
Filed: Sep 8, 2006
Publication Date: Feb 15, 2007
Inventors: Stephen Fenton (Houston, TX), Jon Hed (Houston, TX)
Application Number: 11/517,715
International Classification: E21B 29/12 (20060101);