SUBSEA WELLHEAD TREE PLUG INTERVENTION SYSTEMS

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of and priority to U.S. Provisional Patent Application Ser. No. 63/734,480, filed Dec. 16, 2024, and entitled, “Open Water Crown Plug Retrieval and Installation Method,” the entire contents of which are incorporated herein by reference.

BACKGROUND

Embodiments disclosed herein generally relate to subsea wellbores for producing formation fluids, such as hydrocarbons, and more specifically to systems and methods for installing or removing plugs in a subsea wellhead assembly.

An offshore wellbore may include a subsea wellhead assembly. The subsea wellhead assembly may include one or more valves and fluid flow paths that are configured to provide selective fluid communication with one or more flow paths defined in the wellbore. One or more plugs may be installed into the subsea wellhead assembly that are configured to seal off an interior of the subsea wellhead assembly from the subsea environment.

SUMMARY

Some embodiments disclosed herein are directed to a plug intervention system for retrieving or installing a plug for a subsea wellhead assembly. The plug intervention system includes a cap including an upper end, a lower end, and a cavity extending into the cap from the lower end, where the cap is configured to engage with a connection hub of the subsea wellhead assembly such that the connection hub is at least partially received into the cavity. In addition, the plug intervention system includes a guidance assembly connected to the upper end of the cap, where the guidance assembly is configured to guide a plug intervention tool into a bore of the subsea wellhead assembly via the connection hub for removal or installation of the plug.

Some embodiments disclosed herein are directed to a plug intervention system for retrieving or installing a plug for a subsea wellhead assembly. The plug intervention system includes a cap that is configured to cover an opening to a bore of a connection hub of the subsea wellhead assembly. In addition, the plug intervention system includes a guidance assembly connected to a terminal upper end of the cap so that the guidance assembly is configured to be inserted into the bore when the cap is engaged with the connection hub, where the guidance assembly is configured to guide a plug intervention tool into the bore for removal or installation of the plug.

Some embodiments disclosed herein are directed to a plug intervention system for retrieving or installing a plug for a subsea wellhead assembly. The plug intervention system includes a cap that is configured to engage with a connection hub of the subsea wellhead assembly, where the connection hub includes a bore that is in communication with a plug seat. In addition, the plug intervention system includes a guidance sleeve that is coupled to the cap, where the guidance sleeve is configured to be inserted into the bore when the cap is engaged with the connection hub such that the guidance sleeve extends through the bore toward the plug seat.

Some embodiments disclosed herein are directed to a plug intervention system for retrieving or installing a plug for a subsea wellhead assembly. The plug intervention system includes a cap that is configured to engage with a connection hub of the subsea wellhead assembly, where the connection hub includes a bore that is in communication with a plug seat. In addition, the plug intervention system includes a plug intervention tool that is configured to engage with the plug. Further, the plug intervention system includes a linear actuator coupled to the plug intervention tool and the cap, where the linear actuator is configured to translate the plug intervention tool within the bore when the cap is engaged with the connection hub.

Some embodiments disclosed herein are directed to a method including (a) lowering a cap of a plug intervention system into a subsea environment to a subsea wellhead assembly. In addition, the method includes (b) receiving a connection hub of the subsea wellhead assembly into a cavity of the cap. Further, the method includes (c) inserting a plug intervention tool into a bore of the connection hub by use of a guidance assembly that is connected to an upper end of the cap. Still further, the method includes (d) installing a plug into or retrieving the plug from a plug seat in the subsea wellhead assembly by use of the plug intervention tool.

BRIEF DESCRIPTION OF DRAWINGS

For a detailed description of various exemplary embodiments, reference will now be made to the accompanying drawings in which:

FIG. 1 is a schematic diagram of a subsea system that includes a subsea wellhead assembly and a plug intervention system according to some embodiments disclosed herein;

FIG. 2 is an enlarged cross-section of the connection hub of the subsea wellhead assembly of the subsea system of FIG. 1 according to some embodiments disclosed herein;

FIG. 3 is a cross-sectional view of the plug intervention system of the subsea system of FIG. 1 according to some embodiments disclosed herein;

FIGS. 4A-4D are sequential views of an operation to remove and re-install a crown plug into the bore of the subsea wellhead assembly of FIG. 1 by use of the plug intervention system of FIG. 3 according to some embodiments disclosed herein;

FIG. 5 is a cross-sectional view of the plug intervention system of the subsea system of FIG. 1 according to some embodiments disclosed herein;

FIGS. 6A and 6B are sequential views of an operation to remove a crown plug into the bore of the subsea wellhead assembly of FIG. 1 by use of the plug intervention system of FIG. 5 according to some embodiments disclosed herein;

FIG. 7 is a cross-sectional view of the plug intervention system of the subsea system of FIG. 1 according to some embodiments disclosed herein;

FIG. 8 is a cross-sectional view of the plug intervention system of the subsea system of FIG. 1 according to some embodiments disclosed herein;

FIGS. 9A and 9B are sequential views of an operation to remove a crown plug into the bore of the subsea wellhead assembly of FIG. 1 by use of the plug intervention system of FIG. 8 according to some embodiments disclosed herein;

FIG. 10 is a cross-sectional view of the plug intervention system of FIG. 8 engaged with a connection hub of the subsea wellhead assembly of FIG. 1, where the plug intervention system further includes an occlusion sleeve that extends within the bore of the connection hub according to some embodiments disclosed herein;

FIG. 11 is a cross-sectional view of the plug intervention system of FIG. 8 that includes a guidance sleeve from the plug intervention system of FIG. 3 according to some embodiments disclosed herein; and

FIG. 12 is a cross-sectional view of the plug intervention system of FIG. 3 that is configured to sealingly engage with the connection hub of the subsea wellhead assembly of FIG. 1 according to some embodiments.

DETAILED DESCRIPTION

A subsea wellhead assembly may include one or more plugs that are configured to seal off an interior of the subsea wellhead assembly from the subsea environment. At some point, it may become desirable to perform an intervention operation for the subsea wellbore. Such intervention operations may include additional drilling, equipment installation or retrieval (such as tubing, tools, measurement devices, etc.), fluid injection, perforation, and stimulation, among others. In order to perform an intervention operation, the one or more plugs of the subsea wellhead assembly may first be removed to provide access to the wellbore. Following the intervention operation, the one or more plugs may be re-installed (either via re-installation of the original plugs or installation of new plugs) into the subsea wellhead assembly.

A top or uppermost plug of the one or more plugs in the subsea wellhead assembly may be referred to as a crown plug. In some circumstances, the crown plug may be larger (such as in diameter) than the others of the one or more plugs in the subsea wellhead assembly. Some types of intervention systems may not have large enough bores or other through-passages to pass the crown plug therethrough. Thus, in such circumstances, a well operator may be forced to deploy intervention systems that have sufficient clearances for removing or installing the larger crown plug as part of an intervention operation, which may increase costs and complexity for such operations.

Accordingly, embodiments disclosed herein include plug intervention systems that may be configured to install and/or remove one or more plugs, such as a crown plug, in a subsea wellhead system. In some embodiments, the plug intervention systems may be configured to engage with a connection hub of the subsea wellhead assembly in an open-water arrangement that is free from additional pressure barriers between the plug(s) and the surrounding subsea environment. Thus, the plug intervention systems may be smaller, lighter, and less expensive than a conventional intervention system, which may include additional pressure barriers and control mechanisms for selectively closing the wellbore in the event of an emergency as previously described. In some embodiments, the plug intervention systems may be configured to remove or install the crown plug of the subsea wellhead assembly so that a separate intervention assembly may then be used to remove (and later install) the additional (and smaller) plugs. As a result, through use of the embodiments disclosed herein, a well operator may deploy intervention systems that may not be suitable for removing or installing a larger crown plug for the intervention operation of the subsea wellbore.

FIG. 1 illustrates a subsea system 10 that includes a subsea wellhead assembly 50 having a connection hub 52 according to some embodiments disclosed herein. The subsea system 10 includes a subsea wellbore 20 that extends into a subterranean formation from the sea floor 12. The subsea wellhead assembly 50 is coupled to the uphole end of the subsea wellbore 20 at or proximate the sea floor 12.

The subsea wellhead assembly 50 may be coupled to and supported on the wellhead 22. The subsea wellhead assembly 50 may include a body 54. The body 54 may include a first or upper end 54a and a second or lower end 54b opposite the upper end 54a. The lower end 54b may be coupled to the subsea wellbore 20 at (or proximate to) the sea floor 12, and the upper end 54a may be projected vertically away from the sea floor 12 and toward the sea surface 11. In some embodiments, the subsea wellhead assembly 50 may include a subsea valve tree, such as a Christmas Tree valve assembly, or more particularly a horizontal Christmas Tree valve assembly. However, it should be appreciated that the subsea wellhead assembly 50 may include additional or alternatively components, assemblies, or subsystems that are configured to provide one or more of a fluid or pressure control of or access to the subsea wellbore 20.

The connection hub 52 may be coupled to the upper end 54a of the body 54. In some embodiments, the connection hub 52 may be integrally formed on the body 54 so that the body 54 and connection hub 52 may be formed as a single-piece monolithic body. In some embodiments, the connection hub 52 may be a separate body that is coupled (e.g., via bolts, subsea connector, threaded connection, clamps, etc.) to the body 54.

The body 54 may also define a plurality of fluid flow paths therein. One or more of the plurality of flow paths defined in the body 54 may be in fluid communication with one or more fluid flow paths defined in the subsea wellbore 20. For instance, FIG. 1 schematically illustrates a vertical bore 56 (or “bore” 56) that extends through the body 54 and connection hub 52 of the subsea wellhead assembly 50. The vertical bore 56 may be in fluid communication with the subsea wellbore 20 so that fluids, equipment (such as equipment for performing an intervention operation), etc. may be inserted into the subsea wellbore 20 via the vertical bore 56 during operations.

In addition, the body 54 may include one or more additional flow paths (not shown) defined therein that are configured to direct fluid into and/or out of the subsea wellbore 20 during operations. The body 54 includes a plurality of access valves 55 that are in fluid communication with these one or more additional flow paths. These access valves 55 may control fluid flow along the one or more additional flow paths during operations. In some embodiments, the access valves 55 may include a production wing valve, and an annulus swab valve.

One or more plugs 60, 62 may be inserted within the vertical bore 56 to seal the vertical bore 56 from the subsea environment 13. For instance, the subsea wellhead assembly 50 may include a first or upper plug 60 and a second or lower plug 62 that may be positioned axially below the upper plug 60. The plugs 60, 62 may be positioned in the body 54 and/or the connection hub 52 via the vertical bore 56.

The upper plug 60 may be referred to herein as a “crown plug.” In some embodiments, the crown plug 60 may be larger (such as by having a larger outer diameter) than the lower plug 62. Thus, in some circumstances, intervention packages that may be landed on the connection hub 52 may not have large enough inner bores and passages to receive the crown plug 60. Accordingly, to initiate an intervention operation for the subsea wellbore 20, a plug intervention system 100 may be lowered onto the connection hub 52 in order to remove the crown plug 60. Subsequently, an intervention system (not shown, and which may include additional fluid barriers and actuatable seals, rams, or other sealing devices) may be lowered to remove the lower plug 62 and perform the intervention operation.

The plug intervention system 100 may be lowered form a surface system 16 into the subsea environment 13 to the connection hub 52 via a tether 17. The tether 17 may comprise any suitable connector that may support the plug intervention system 100 and/or provide fluid and/or data communication between the plug intervention system 100 and the surface system 16. For instance, the tether 17 may comprise flex line, e-line, slickline, wireline (e.g., braided wireline), coiled tubing, a tubing string (e.g., that is comprised of a plurality of tubular members coupled end-to-end), or some combination thereof. The surface system 16 may include a rig, platform, ship, or other vessel.

Further details of embodiments of the plug intervention system 100 are described herein. However, generally speaking, the plug intervention system 100 may include a cap 110 and a guidance assembly 150. The cap 110 may be configured to engage or mate with the connection hub 52. In addition, the guidance assembly 150 may be configured to guide a plug intervention tool (not shown) into the vertical bore 56 via the connection hub 52 for removal or installation of the crown plug 60 during operations.

Because the plug intervention system 100 is configured to remove the crown plug 60 from the subsea wellhead assembly 50 while leaving the lower plug 62 in place, the plug intervention system 100 may be deployed an in “open-water” configuration and without any additional well or fluid control systems (such as ramps, seals, shears, etc. that may typically be associated with a lower marine riser package, intervention package, blow-out preventer, etc. As a result, deployment of the plug intervention system 100 may benefit from reduced costs and complexity when compared to the deployment of a more traditional intervention or well control package for removal of both of the plugs 60, 62.

Referring now to FIG. 2, an enlarged cross-sectional view of the connection hub 52 of the subsea wellhead assembly 50 is shown according to some embodiments. The bore 56 extends along a central or longitudinal axis 105 (or “axis” 105). In some embodiments, the axis 105 may be aligned with the force of gravity so that the axis 105 may be referred to as a “vertical axis.”

The connection hub 52 may comprise a cylindrical member or body that is coupled to or integrated with the body 54 as previously described. The connection hub 52 may extend axially along the axis 105 to an upper end 52a. In some embodiments, such as embodiments where the connection hub 52 is integrated with the body 54, the upper end 52a of the connection hub 52 may be coincident with (and thus may define) the upper end 54a of the body 54.

The upper end 52a of the connection hub 52 may define an opening 53 to the bore 56. A debris cap 70 may be engaged (such as threaded, clamped, etc.) onto the upper end 52a of the connection hub 52 to thereby occlude or cover the opening 53.

The crown plug 60 may be engaged with a first or upper plug seat 72 that is positioned or defined in the bore 56, and the lower plug 62 may be engaged with a second or lower plug seat 74 that is positioned or defined in the bore 56. The upper plug seat 72 may be axially positioned above lower plug seat 74 along the axis 105. Thus, the upper plug seat 72 may be positioned axially between the lower plug seat 74 and the upper end 52a of the connection hub 52. In some embodiments, one or both of the upper plug seat 72 and lower plug seat 74 may be integrally formed in or by the bore 56. In some embodiments, one or both of the upper plug seat 72 and the lower plug seat 74 may be defined by additional components that may be positioned in the bore 56. For instance, in some embodiments, the upper plug seat 72 may be defined on or by an internal tree cap that is positioned in the bore 56, and/or the lower plug seat 74 may be defined on or by a tubing hanger that is positioned in the bore 56.

The crown plug 60 is a generally cylindrical member that includes a first or upper end 60a and a second or lower end 60b opposite the upper end 60a. A plurality of seals 82 are coupled to the crown plug 60 at or proximate to the lower end 60b. The plurality of seals 82 are configured to sealingly engage with corresponding surface(s) in the upper plug seat 72 to prevent (or at least restrict) fluid and pressure communication along the bore 56 axially across the crown plug 60. Each of the seals 82 may comprise any suitable radial seal ring or other radial sealing member or assembly.

In addition, the crown plug 60 includes a plurality of locking dogs 84 that are radially expandable into corresponding recesses 76 defined in the upper plug seat 72 to secure the crown plug 60 to the upper plug seat 72 during operations. The locking dogs 84 may be axially positioned between the plurality of seals 82 and the upper end 60a along the axis 105 (that is, when the crown plug 60 is installed in the bore 56 and aligned with the axis 105 as shown in FIG. 2). An actuation assembly 86 may be coupled to or incorporated on (or in) the crown plug 60. The actuation assembly 86 may be accessible on or through the upper end 60a of the crown plug 60 during operations. Engagement or actuation of the actuation assembly 86 may be configured to radially expand (or deploy) the plurality of locking dogs 84 into the corresponding recesses 76 during operations.

The lower plug 62 may be similarly configured as the crown plug 60. Thus, the lower plug 62 may include upper and lower ends 62a and 62b, respectively. In addition, the lower plug 62 includes seals 82, locking dogs 84, and an actuation assembly 86 that are arranged and configured in substantially the same manner as that described above for the crown plug 60. Thus, the seals 82 on the lower plug 62 may searingly engage with corresponding surface(s) of the lower plug seat 74 to prevent (or restrict) fluid communication along the bore 56 axially past the lower plug 62. In addition, the locking dogs 84 on the lower plug 62 may be radially expanded (via the actuation assembly 86) to engage with corresponding recesses 76 in the lower plug seat 74 to secure the lower plug 62 thereto as previously described.

As previously described, the crown plug 60 may be larger than the lower plug 62. Specifically, the crown plug 60 may include a first outer diameter D₆₀, and the lower plug 62 may include a second outer diameter D₆₂. The first outer diameter D₆₀ may be greater than the second outer diameter D₆₂. Thus, the lower plug 62 may be configured to pass through smaller bores or flow passages than the crown plug 60.

FIG. 3 shows a cross-sectional view of the plug intervention system 100 according to some embodiments. As previously described, the plug intervention system 100 includes a cap 110 and a guidance assembly 150. The cap 110 includes a central or longitudinal axis 107 (or “axis 107”), a first or upper end 110 a, a second or lower end 110b opposite the upper end 110a, and a sidewall 110c extending axially between the ends 110a, 110b. A cavity 112 may extend axially into the cap 110 from the lower end 110b to the upper end 110a. Thus, the upper end 110a may be a closed end, and the lower end 110b may be an open end of the cap 110. The upper end 110a may comprise a terminal upper end of the cap 110, and the lower end 110b may comprise a terminal lower end of the cap 110.

In some embodiments, the cap 110 may have an axial height H₁₁₀ that extends axially between the ends 110a, 110b along axis 107. In some embodiments, the axial height H₁₁₀ may be relatively small when compared to an axial height of an intervention system (which may include the additional components for fluid and/or pressure containment as previously described). For instance, in some embodiments, the axial height H₁₁₀ may be less than or equal to about 15 feet, such as less than or equal to about 10 feet, such as less than or equal to about 8 feet, such as less than or equal to about 5 feet. However, other values of the axial height H₁₁₀ are contemplated.

The cap 110 may have a generally cylindrical shape. As a result, the sidewall 110c and the cavity 112 may be cylindrical in shape. However, other shapes are contemplated for the cap 110 (and thus also for the sidewall 110c and cavity 112).

During operations, the cap 110 may be engaged with the connection hub 52 of the subsea wellhead assembly 50 (FIGS. 1 and 2). For instance, the connection hub 52 may be at least partially inserted into the cavity 112 so that the cap 110 may occlude the opening 53 on the upper end 52a. Thus, the cap 110 may comprise (and may be referred to herein as) a housing that is configured to cover the upper end 52a of the connection hub 52 during operations.

The guidance assembly 150 may include a guidance sleeve 154 that extends axially through the upper end 110a of the cap 110 and into the cavity 112 along the axis 107. The guidance sleeve 154 may include a first or upper end 154a and a second or lower end 154b that is opposite the upper end 154a. The upper end 154a may be positioned axially above the upper end 110a and outside of the cap 110 (and specifically outside of the cavity 112). The lower end 154b may be positioned below the upper end 110a and within the cavity 112.

The guidance sleeve 154 may define a throughbore 158 that extends axially between the ends 154a, 154b. Thus, the throughbore 158 provides access into the cavity 112 from outside of the cap 110, axially above the upper end 110a. A guide surface 160 may be positioned at the upper end 154a adjacent to the throughbore 158. The guide surface 160 may comprise a frustoconical surface that diverges radially inward toward the axis 107 when extending axially from the upper end 154a toward the lower end 154b. Thus, the guide surface 160 may be referred to herein as a “frustoconical guide surface” or “funnel.” During operations, the guide surface 160 may guide a plug intervention tool (not shown, but see plug intervention tool 170 shown in FIGS. 4B-4D) into the throughbore 158 of the guidance sleeve 154.

The guidance sleeve 154 may include a mounting shoulder 152 that extends radially relative to the axis 107. The mounting shoulder 152 may be engaged with the upper end 110a of the cap 110 so that the guidance sleeve 154 is connected to, carried on, and supported by the upper end 110a of the cap 110.

A plurality of latch assemblies 159 are coupled to the sidewall 110c of the cap 110. As will be described in more detail herein, the latch assemblies 159 may be configured to secure the cap 110 to the connection hub 52 during operations. In some embodiments, the latch assemblies 159 may comprise set screws that are threadably engaged with the cap 110, so that the set screws may be threadably and radially advanced into the cavity 112 to engage with an outer surface of the connection hub 52. The plurality of latch assemblies 159 may be circumferentially spaced (such as uniformly circumferentially spaced) about the axis 107.

FIGS. 4A-4D illustrate sequential views of an operation to remove and re-install the crown plug 60 from the bore 56 of the subsea wellhead assembly 50 by use of an embodiment of the plug intervention system 100 shown in FIG. 3. As shown in FIG. 4A, the plug intervention system 100 is landed on the connection hub 52 so that the connection hub 52 is at least partially received into the cavity 112. In some embodiments, the cap 110 may be landed on the connection hub 52 so that the axis 107 of the cap 110 is aligned (or substantially aligned) with the axis 105 of the bore 56. The plug intervention system 100 may be lowered subsea (or into the subsea environment 13) via the tether 17 (FIG. 1). In addition, prior to landing the plug intervention system 100 on the connection hub 52, the debris cap 70 may be removed from the connection hub (such as by a remotely-operated vehicle (ROV), a tool that is lowered from the surface system 16 (FIG. 1), etc.).

The latch assemblies 159 may be radially advanced through the sidewall 110c to engage with an outer surface of the connection hub 52, along the sidewall 110c (or a recess or other feature thereon) to secure the cap 110 to the connection hub 52. In some embodiments, the latch assemblies 159 may be actuated by an ROV (not shown, but see ROV 210 that is schematically depicted in FIGS. 6A and 6B).

When the cap 110 is landed on the connection hub 52, the guidance sleeve 154 may be received into the bore 56. In some embodiments, the guidance sleeve 154 may extend axially (along the axes 105, 107) to or proximate to the upper plug seat 72. In some embodiments, the throughbore 158 of the guidance sleeve 154 may be aligned along the axes 105, 107 so that the throughbore 158 may define a passage for guiding a tool (such as plug intervention tool 170) to the crown plug 60 during operations.

Referring now to FIG. 4B, after the plug intervention system 100 is landed on the connection hub 52, a plug intervention tool 170 may be lowered through the guidance sleeve 154 to engage with the crown plug 60. Specifically, the plug intervention tool 170 may be lowered subsea (or into and through the subsea environment 13) and inserted into the throughbore 158 of the guidance sleeve 154 from the upper end 154a. The plug intervention tool 170 may be lowered via the tether 17 (which may be the same tether or a different tether that is used to lower the plug intervention system 100 as previously described).

The guide surface 160 may help to guide the plug intervention tool 170 into the throughbore 158. Once the plug intervention tool 170 advances into the throughbore 158, the throughbore 158 may then guide the plug intervention tool 170 to the crown plug 60. Specifically, as the plug intervention tool 170 is lowered through the throughbore 158 of the guidance sleeve 154, the throughbore 158 may center or align the plug intervention tool 170 with the crown plug 60 so that the plug intervention tool 170 may land on and engage with upper end 60a of the crown plug 60 during operations.

The plug intervention tool 170 may include an engagement assembly 172 that is configured to engage with a suitable assembly, device, sleeve, profile, etc. that is defined on the upper end 60a of the crown plug 60. For instance, the engagement assembly 172 may be configured to engage with the actuation assembly 86 of the crown plug 60. Any suitable engagement be used between the engagement assembly 172 and actuation assembly 86 (or other component, profile, or portion of crown plug 60).

As shown in the sequence from FIGS. 4B to 4C, once the engagement assembly 172 is engaged with the actuation assembly 86, tension may be induced in the tether 17 to pull the plug intervention tool 170 axially upward within the throughbore 158. For instance, the tether 17 may be pulled from the sea surface 11, such as by the surface system 16 (FIG. 1). The tension may be sufficient to dislodge the locking dogs 84 from the recesses 76 so that the crown plug 60 may be axially pulled out of the upper plug seat 72. Thereafter, the crown plug 60 may be axially withdrawn out of the guidance sleeve 154.

After the crown plug 60 is removed from the bore 56 of the subsea wellhead assembly 50, the plug intervention system 100 may be disconnected from the connection hub 52 and removed. In some embodiments, the plug intervention system 100 is pulled back to the sea surface 11 (FIG. 1) via tether 17. In some embodiments, the plug intervention system 100 may be deposited or stored in the subsea environment 13, such as on or proximate to the sea floor 12 (FIG. 1) after the crown plug 60 is removed from the bore 56.

Next, an intervention system (not shown) may be landed on the connection hub 52. The intervention system (not shown) may be configured to remove the lower plug 62 from the bore 56 and facilitate performance of the intervention operation in the subsea wellbore 20 (FIG. 1). As previously described, the intervention system (not shown) may include additional seals as well as pressure and/or fluid barriers that may maintain a suitable containment for fluids flowing within, into, or out of the subsea wellbore 20 during the intervention operation.

Following the completion of the intervention operation, the intervention system (not shown) may reinstall the lower plug 62 into the lower plug seat 74, such as by re-installing the original lower plug 62 or installing a new lower plug 62. Thereafter, the intervention system (not shown) may be pulled back to the sea surface 11 (FIG. 1). Next, as shown in FIG. 4D, the plug intervention system 100 may be lowered back onto the connection hub 52 as previously described, and the plug intervention tool 170 may be reinserted into the throughbore 158 of the guidance sleeve 154 to install the crown plug 60 into the upper plug seat 72.

Specifically, the original crown plug 60 or a new crown plug 60 may be connected to the engagement assembly 172 of the plug intervention tool 170 in the manner generally described above. In some embodiments, when the plug intervention tool 170 installs the original crown plug 60 back into the upper plug seat 72, the crown plug 60 may remain engaged to the engagement assembly 172 from when the plug intervention tool 170 initially removed the crown plug 60 as previously described (FIG. 4C).

The plug intervention tool 170 may lower the crown plug 60 into the upper plug seat 72 via the guidance sleeve 154. Thus, the throughbore 158 of the guidance sleeve 154 may center the crown plug 60 into the upper plug seat 72 during operations. In some embodiments, the weight of the plug intervention tool 170 (or other components or devices coupled thereto), tether 17, and crown plug 60 may be sufficient to set the crown plug 60 into the upper plug seat 72. In some embodiments, a heavy connector 174 (or “jar”) may be connected to the plug intervention tool 170. Once the crown plug 60 is set onto the upper plug seat 72, the plug intervention tool 170 may be raised and dropped one or more times (such as along the arrows 175) onto the upper end 60a of the crown plug 60 to lodge or jar the crown plug 60 into the upper plug seat 72. The additional weight of the heavy connector 174 may help to transfer sufficient force to the crown plug 60 to lodge the crown plug 60 within the upper plug seat 72 during these operations. In some embodiments, jarring the crown plug 60 with the plug intervention tool 170 as previously described may cause actuation of the actuation assembly 86 so that the locking dogs 84 may be radially expanded (or deployed) into the recesses 76 as previously described.

FIG. 5 shows a cross-sectional view of the plug intervention system 200 according to some embodiments. In some embodiments, the plug intervention system 200 may be used in place of the plug intervention system 100 (FIG. 1) in the subsea system 10 of FIG. 1. The plug intervention system 200 may be similar in some respects to the plug intervention system 100. Thus, in describing the features of plug intervention system 200, the same reference numerals are used to refer to components of the plug intervention system 200 that are shared with the plug intervention system 100. In addition, the following description will focus on the features of the plug intervention system 200 that are different from the plug intervention system 100.

For instance, the plug intervention system 200 may include the cap 110 as previously described. However, in place of the guidance sleeve 154, the guidance assembly 150 of the plug intervention system 200 may include a linear actuator 202. The linear actuator 202 may be connected to the upper end 110a of the cap 110 via a mounting plate 206. The linear actuator 202 may be configured to translate (such as extend or retract) a shaft 204 axially along the axis 107 within the cavity 112. The linear actuator 202 may utilize any suitable actuation system or mechanism. For instance, the linear actuator 202 may comprise a hydraulic cylinder that is configured to utilize pressurized hydraulic fluid to translate the shaft 204 during operations. In some embodiments, the linear actuator 202 may comprise a screw actuator that threadably engages the shaft 204 to translate the shaft 204 during operations.

The mounting plate 206 may be engaged with the upper end 110a of the cap 110 so that the linear actuator extends axially through the upper end 110a and into the cavity 112 along the axis 107. An actuation interface 208 may be coupled to the linear actuator 202 and positioned outside of the cap 110. Specifically, in some embodiments, the actuation interface 208 may be coupled to the mounting plate 206. The actuation interface 208 may comprise any suitable interface that may be engaged by an ROV to actuate the linear actuator 202. For instance, in some embodiments, the actuation interface 208 may comprise a button, lever, valve, switch, plug, or other suitable device or system. During operations, an ROV may engage with the actuation interface 208 to selectively translate the shaft 204 axially along the axis 107 via the linear actuator 202. In some embodiments, the linear actuator 202 may be actuated remotely by a suitable connection, such as fluid lines, electrical conductors, fiber optic cables, etc.

The plug intervention tool 170 may be connected to the shaft 204, such as to a distal end thereof. During operations, actuation of the linear actuator 202 may translate (such as extend and retract) the plug intervention tool 170 via the shaft 204 along the axis 107.

FIGS. 6A and 6B illustrate views of an operation to remove the crown plug 60 from the bore 56 of the subsea wellhead assembly 50 by use of the embodiment of the plug intervention system 200 shown in FIG. 5. As previously described, the cap 110 of the plug intervention system 200 may be landed on and secured to the connection hub 52 in the manner previously described for the plug intervention system 100. In addition, prior to landing the plug intervention system 200 on the connection hub 52, the debris cap 70 (FIG. 2) may be removed from the connection hub 52 as previously described.

When the cap 110 is landed on the connection hub 52, the linear actuator 202, shaft 204, and plug intervention tool 170 may be received into the bore 56. For instance, the linear actuator 202, shaft 204, and plug intervention tool 170 may be received into the bore 56 so that the linear actuator 202 is configured to translate (such as extend and retract) the shaft 204 and plug intervention tool 170 along the aligned axes 105, 107.

As also shown in FIG. 6A, after the plug intervention system 200 is landed on the connection hub 52, the plug intervention tool 170 may be translated axially within the bore 56 via the linear actuator 202 and shaft 204 to engage the engagement assembly 172 with the crown plug 60 (such as with the actuation assembly 86 as previously described). Thus, the linear actuator 202 may guide the plug intervention tool into and through the bore 56 to engage with the crown plug 60 during operations. As previously described, the linear actuator 202 may be actuated to translate the shaft 204 and plug intervention tool 170 by an ROV 210 via the actuation interface 208.

As shown in the sequence from FIGS. 6A to 6B, once the engagement assembly 172 is engaged with the actuation assembly 86, the linear actuator 202 may retract the shaft 204 to pull the plug intervention tool 170 axially upward within the bore 56. The tension applied to the crown plug 60 via the linear actuator 202 may be sufficient to dislodge the locking dogs 84 from the recesses 76 so that the crown plug 60 may be axially pulled out of the upper plug seat 72. Thereafter, the plug intervention system 200 may be disconnected from the connection hub 52 and removed. Because the crown plug 60 is engaged with the plug intervention tool 170, which is further connected to the shaft 204, the disconnection and removal of the plug intervention system 200 from the connection hub 52 may also result in the removal of the crown plug 60 from the connection hub 52. Next, an intervention system (not shown) may be landed on the connection hub 52 to remove the lower plug 62 and/or to perform the intervention operation as previously described.

Following the completion of the intervention operation, the intervention system (not shown) may reinstall the lower plug 62 into the lower plug seat 74, such as by re-installing the original lower plug 62 or installing a new lower plug 62. Thereafter, the intervention system (not shown) may be pulled back to the sea surface 11 (FIG. 1). Next, the plug intervention system 200 may be lowered back onto the connection hub 52 so that the crown plug 60 (such as the original crown plug 60 or a new crown plug 60) may be reinserted and installed into the upper plug seat 72 via the linear actuator 202. Specifically, the compressive force applied to the crown plug 60 by the linear actuator 202 via the shaft 204 may be sufficient to both insert the crown plug 60 into the upper plug seat 72 and radially expand the locking dogs 84 into the recesses 76 as previously described.

FIG. 7 shows a cross-sectional view of the plug intervention system 300 according to some embodiments. In some embodiments, the plug intervention system 300 may be used in place of the plug intervention system 100 (FIG. 1) in the subsea system 10 of FIG. 1. The plug intervention system 300 may be similar in some respects to the plug intervention systems 100, 200. Thus, in describing the features of plug intervention system 300, the same reference numerals are used to refer to components of the plug intervention system 300 that are shared with the plug intervention systems 100, 200. In addition, the following description will focus on the features of the plug intervention system 300 that are different from the plug intervention systems 100, 200.

For instance, the plug intervention system 300 may include the cap 110 and linear actuator 202 as previously described. However, rather than directly connecting the mounting plate 206 directly to the upper end 110a of the cap 110, the mounting plate 206 may be coupled to the upper end 110a via one more additional linear actuators 302. The linear actuator(s) 302 may be positioned outside of the cap 110 on the upper end 110a and may extend parallel to the linear actuator 202 (and thus axially along axis 107). Each of the linear actuator(s) 302 may be coupled to the mounting plate 206 via a shaft 304. During operations, the linear actuator(s) 302 may extend or retract the shafts 304 (e.g., in an axial direction relative to axis 107) to raise or lower the mounting plate 206, and thus also to raise and lower the linear actuator 202, shaft 204, and plug intervention tool 170. Thus, the linear actuators 302 may be configured to increase a range of axial movement for the plug intervention tool 170 within the cavity 112. In addition (or alternatively), the linear actuators 302 may add additional hydraulic power for removing or setting the crown plug 60 (FIGS. 6A and 6B) relative to the upper plug seat 72.

The linear actuator(s) 302 may be actuated by use of the actuation interface 208 (or another actuation interface 208 that is coupled to the mounting plate 206, cap 110, etc.) as previously described for the linear actuator 202. As was previously described for the linear actuator 202, in some embodiments, the linear actuator(s) 302 may be actuated remotely, such as via a fluid line, electrical conductor, etc.

FIG. 8 shows a cross-sectional view of the plug intervention system 400 according to some embodiments. In some embodiments, the plug intervention system 400 may be used in place of the plug intervention system 100 in the subsea system 10 of FIG. 1. The plug intervention system 400 may be similar in some respects to the plug intervention system 100. Thus, in describing the features of plug intervention system 400, the same reference numerals are used to refer to components of the plug intervention system 400 that are shared with the plug intervention system 100. In addition, the following description will focus on the features of the plug intervention system 400 that are different from the plug intervention system 100.

Specifically, the plug intervention system 400 may include a cap 410 in place of the cap 110 (FIG. 3). The cap 410 may be configured to engage or mate with the connection hub 52. The cap 410 includes a central or longitudinal axis 407 (or “axis 407”), a first or upper end 410 a, and a second or lower end 410 b opposite the upper end 410a. In addition, the cap 410 may include a radially extending shoulder 412 (or “shoulder 412”), a first or upper portion 414 extending axially from the upper end 410a to the shoulder 412, and a second or lower portion 416 extending axially from the shoulder 412 to the lower end 410b.

In some embodiments, the cap 410 may include an axial height that extends axially between the ends 410a, 410b along axis 407. In some embodiments, the axial height of the cap 410 may be in the same example ranges that were previously described above for the axial height H₁₁₀ (FIG. 3).

The cap 410 may be a generally cylindrical member so that the upper portion 414 and lower portion 416 may each have a cylindrical shape. In addition, the shoulder 412 may comprise an annular shoulder that extends circumferentially (such as fully or partially) about the axis 407.

The guidance assembly 150 of the plug intervention system 400 may include the linear actuator 202. As shown in FIG. 8, the guidance assembly 150 may be configured in a similar manner to the plug intervention system 200 shown in FIG. 5. As a result, the mounting plate 206 may be directly engaged with the upper end 410a so that the linear actuator 202 may extend axially through the cap 410 along the axis 407. During operations, the linear actuator 202 may translate (such as extend or retract) the shaft 204 and plug intervention tool 170 axially below the lower end 410b of cap 410 along the axis 407. Actuation of the linear actuator 202 may be achieved via the actuation interface 208 as previously described.

In some embodiments, the guidance assembly 150 of the plug intervention system 400 may be configured in a similar manner to the plug intervention system 300 (FIG. 7). Thus, in some embodiments, the mounting plate 206 may be coupled to the upper end 410a of the cap 410 via the additional linear actuators 302 as previously described (FIG. 7).

In addition, a pressurization assembly 420 may be coupled to the cap 410, such as to the upper portion 414 or elsewhere. In some embodiments, the pressurization assembly 420 may be coupled to the mounting plate 206. The pressurization assembly 420 may comprise any suitable fluid connector (such as a port, plug, etc.) for connecting a source of pressure (such as pressurized hydraulic fluid, gas, etc.). The pressurization assembly 420 may be in fluid communication with the lower end 410b of the cap 410 via one or more internal passage(s) 422 defined in the cap 410. As will be described in more detail herein, the pressurization assembly 420 and internal passes(s) 422 may be configured to inject a pressurizing fluid through the lower end 410b of the cap 410 during operations.

FIGS. 9A and 9B illustrate some sequential views of an operation to remove and re-install the crown plug 60 from the bore 56 of the subsea wellhead assembly 50 by use of the embodiment of the plug intervention system 400 shown in FIG. 8. As shown in FIG. 9A, the plug intervention system 400 is landed on the connection hub 52 so that the lower portion 416 may be at least partially inserted into the bore 56 of the connection hub 52 via the opening 53. Thus, a size and shape of the lower portion 416 may be selected so that the lower portion 416 may be received within the bore 56 during operations. In some embodiments, the cap 410 may be landed on the connection hub 52 so that the axis 407 of the cap 410 is aligned (or substantially aligned) with the axis 105 of the bore 56. The plug intervention system 400 may be lowered subsea (or into the subsea environment 13) via the tether 17 (FIG. 1). In addition, prior to landing the plug intervention system 400 on the connection hub 52, the debris cap 70 (FIG. 2) may be removed from the connection hub (such as by a remotely operated vehicle (ROV), a tool that is lowered from the surface system 16, etc.).

In some embodiments, the lower portion 416 of the cap 410 may be axially inserted into bore 56 along the axes 105, 407 until the shoulder 412 engages or abuts the upper end 52a of the connection hub 52. In some embodiments, the cap 410 (such as the lower portion 416 and/or shoulder 412) may sealingly engage with the connection hub 52 to prevent or restrict fluid communication between the bore 56 and the surrounding subsea environment 13 during operations. For example, one or more radial seals 430 may be positioned or defined between the lower portion 416 and the bore 56 of the connection hub 52. Thus, the sealing engagement provided by the radial seal(s) 430 may be configured to isolate the bore 56 from the subsea environment 13. The radial seals 430 may comprise any suitable type of radial seal such as O-rings, seal rings, lip seals, etc.

When the cap 110 is landed on the connection hub 52, the linear actuator 202, shaft 204, and plug intervention tool 170 may be received into the bore 56. For instance, the linear actuator 202, shaft 204, and plug intervention tool 170 may be received into the bore 56 so that the linear actuator 202 is configured to translate (such as extend and retract) the shaft 204 and plug intervention tool 170 along the aligned axes 105, 107.

As is also shown in the sequence from FIG. 9A to 9B, after the plug intervention system 400 is landed on the connection hub 52 as described, the plug intervention tool 170 may be translated axially within the bore 56 via the linear actuator 202 and shaft 204 to engage the engagement assembly 172 with the crown plug 60 (such as with the actuation assembly 86 as previously described). Thus, the linear actuator 202 may guide the plug intervention tool into and through the bore 56 to engage with the crown plug 60 during operations. As previously described, the linear actuator 202 may be actuated to translate the shaft 204 and plug intervention tool 170 by an ROV 210 via the actuation interface 208 as previously described.

As shown in FIG. 9B, once the engagement assembly 172 is engaged with the actuation assembly 86, the linear actuator 202 may retract the shaft 204 to pull the plug intervention tool 170 axially upward within the bore 56. The tension applied to the crown plug 60 via the linear actuator 202 may be sufficient to dislodge the locking dogs 84 from the recesses 76 so that the crown plug 60 may be axially pulled out of the upper plug seat 72. Thereafter, the plug intervention system 400 may be disconnected from the connection hub 52 and removed. Because the crown plug 60 is engaged with the plug intervention tool 170, which is further connected to the shaft 204, the disconnection and removal of the plug intervention system 200 from the connection hub 52 may also result in the removal of the crown plug 60 from the connection hub 52. Next, an intervention system (not shown) may be landed on the connection hub 52 to remove the lower plug 62 and/or to perform the intervention operation as previously described.

Following the completion of the intervention operation, the intervention system (not shown) may reinstall the lower plug 62 into the lower plug seat 74, such as by re-installing the original lower plug 62 or installing a new lower plug 62. Thereafter, the intervention system (not shown) may be pulled back to the sea surface 11 (FIG. 1). Next, the plug intervention system 400 may be lowered back onto the connection hub 52 so that the crown plug 60 (such as the original crown plug 60 or a new crown plug 60) may be reinserted and installed into the upper plug seat 72 as previously described.

In some embodiments, the compressive force applied by the linear actuator 202 may be used to insert and set the crown plug 60 in the manner previously described. In some embodiments, a pressure in the bore 56 may be increased to insert or set the crown plug 60 into the upper plug seat 72. For instance, the ROV 210 (or another ROV) may actuate or engage the pressurization assembly 420 so as to increase a pressure in the bore 56. The pressurization of the bore 56 may also be facilitated by the sealing engagement defined by the radial seals 430 as previously described. In some embodiments, the pressurization assembly 420 may comprise a valve that may be actuated by the ROV 210 so facilitate the communication of pressurizing fluid into the bore 56. In some embodiments, a source of pressurization fluid may be carried on the ROV 210, or may be separately positioned on the sea floor 12, in the subsea environment 13, or on the sea surface 11 (FIG. 1) (such as in or on the surface system 16).

The increased pressure within the bore 56 may be sufficient to drive the crown plug 60 axially into the upper plug seat 72. In some embodiments, the increased pressure within the bore 56 may also be configured to facilitate radial expansion of the locking dogs 84 into the recesses 76. In some embodiments, even if an increased pressure in the bore 56 is utilized to drive the crown plug 60 into the upper plug seat 72, the locking dogs 84 may be radially expanded into recesses 76 via the engagement with the plug intervention tool 170 (via linear actuator 202) in the manner previously described.

FIG. 10 shows an embodiment of the plug intervention system 400 of FIG. 8 that additionally includes an occlusion sleeve 450 (or “sleeve 450”) that extends axially from the lower end 410b of the cap 410. During operations, the sleeve 450 may extend to the upper plug seat 72 (such as to an upper end thereof) and may reduce a volume within the bore 56 that may be pressurized (such as via the pressurization assembly 420) to drive the crown plug 60 into the upper plug seat 72 as previously described.

FIG. 11 shows an embodiment of the plug intervention system 400 of FIG. 8, that includes the guidance sleeve 154 in place of the linear actuator 202 as the guidance assembly 150. Thus, for the embodiment of plug intervention system 400 shown in FIG. 11, the plug intervention tool 170 may be lowered through the guidance sleeve 154 to engage with the crown plug 60 (or to install the crown plug 60) in the manner previously described for the plug intervention system 100 shown in FIGS. 4A-4D.

FIG. 12 shows an embodiment of the plug intervention system 200 (FIG. 5), wherein the cap 110 is configured to sealingly engage with the connection hub 52 according to some embodiments. For instance, for the embodiment of plug intervention system 200 shown in FIG. 12, the wall thickness of the cap 110 may be increased to accommodate a relatively large pressure differential between the cavity 112 and the outer environment (such as the subsea environment 13—FIG. 1). One or more radial seals 430 may be coupled to, defined on, or integrated with the cap 110 along the inner surface of the cavity 112. Specifically, the radial seals 430 may be positioned on an axial projection 431 that extends axially into the cavity 112 from the upper end 110a of the cap 110. The radial seals 430 may be the same as those previously described herein (FIGS. 9A and 9B). During operations, the radial seals 430 may engage with an inner surface of the connection hub 52 so as to isolate the bore 56 from the surrounding subsea environment 13 (FIG. 1). As a result, a pressure in the bore 56 may be increased in order to drive the crown plug 60 into the upper plug seat 72 as previously described). As is also previously described, the pressure in the bore 56 may be increased by selectively communicating a source of pressurized fluid with the bore 56 through the cap 110 via a suitable fluid connector (or other suitable mechanism of system). In some examples, the embodiment of the plug intervention system 200 of FIG. 12 may include the occlusion sleeve 450 shown in FIG. 10 to reduce a volume within the bore 56 that may be pressurized to drive the crown plug 60 into the upper plug seat 72 as previously described.

While various embodiments of a plug intervention system have been described herein, it should be appreciated that additional embodiments of a plug intervention system are contemplated herein. For instance, embodiments of a plug intervention system are contemplated that include a combination of features from various embodiments of a plug intervention system that have been described herein. Thus, if a particular feature is depicted as being included on or with an embodiment of a plug intervention system, it should be appreciated that this particular features may also be included or incorporated into other embodiments of a plug intervention system.

As explained above and reiterated below, the present disclosure includes, without limitation, the following Examples.

Example 1: A plug intervention system for retrieving or installing a plug for a subsea wellhead assembly, the plug intervention system comprising: a cap including an upper end, a lower end, and a cavity extending into the cap from the lower end, where the cap is configured to engage with a connection hub of the subsea wellhead assembly such that the connection hub is at least partially received into the cavity; and a guidance assembly connected to the upper end of the cap, where the guidance assembly is configured to guide a plug intervention tool into a bore of the subsea wellhead assembly via the connection hub for removal or installation of the plug.

Example 2: The plug intervention system of any of the Examples, wherein the guidance assembly comprises a guidance sleeve that is connected to the upper end of the cap and that is configured to extend into the bore of the connection hub when the cap is engaged with the connection hub.

Example 3: The plug intervention system of any of the Examples, wherein the guidance sleeve has an upper end and a lower end, wherein the upper end of the guidance sleeve is positioned outside of the cap and the lower end of the guidance sleeve is positioned within the cavity.

Example 4: The plug intervention system of any of the Examples, wherein the upper end of the guidance sleeve includes a frustoconical guide surface that is configured to guide the plug intervention tool into the guidance sleeve.

Example 5: The plug intervention system of any of the Examples, wherein the guidance assembly comprises a linear actuator that is connected to the upper end of the cap and coupled to the plug intervention tool, wherein the linear actuator is configured to extend and retract the plug intervention tool within the bore of the connection hub when the cap is engaged with the connection hub.

Example 6: The plug intervention system of any of the Examples, wherein the linear actuator comprises a hydraulic cylinder that is configured to extend and retract the plug intervention tool within the bore.

Example 7: The plug intervention system of any of the Examples, wherein the linear actuator comprises a screw actuator that is configured to extend and retract the plug intervention tool within the bore.

Example 8: The plug intervention system of any of the Examples, wherein the cap comprises: a shoulder; and a lower portion extending below the shoulder, wherein the lower portion is configured to be inserted into the bore of the connection hub and the shoulder is configured to engage an upper end of the connection hub.

Example 9: The plug intervention system of any of the Examples, wherein the cap is configured to sealingly engage with the connection hub, and wherein the plug intervention system further comprises a pressurization assembly that is coupled to the cap and that is configured to pressurize the bore of the connection hub.

Example 10: The plug intervention system of any of the Examples, wherein the pressurization assembly comprises a fluid connector that is coupled to the cap.

Example 11: A plug intervention system for retrieving or installing a plug for a subsea wellhead assembly, the plug intervention system comprising: a cap that is configured to cover an opening to a bore of a connection hub of the subsea wellhead assembly; and a guidance assembly connected to a terminal upper end of the cap so that the guidance assembly is configured to be inserted into the bore when the cap is engaged with the connection hub, where the guidance assembly is configured to guide a plug intervention tool into the bore for removal or installation of the plug.

Example 12: The plug intervention system of any of the Examples, wherein the plug intervention tool is supported on the guidance assembly.

Example 13: The plug intervention system of any of the Examples, wherein the guidance assembly comprises a linear actuator that is configured to translate the plug intervention tool within the bore when the cap is engaged with the connection hub.

Example 14: The plug intervention system of any of the Examples, wherein the cap is configured to sealingly engage with the connection hub.

Example 15: The plug intervention system of any of the Examples, further comprising a pressurization assembly coupled to the cap that is configured to pressurize the bore when the cap is engaged with the connection hub.

Example 16: The plug intervention system of any of the Examples, wherein the guidance assembly comprises a guidance sleeve that extends through the terminal upper end of the cap, wherein the guidance sleeve is configured to guide the plug intervention tool into the bore and to the plug.

Example 17: The plug intervention system of any of the Examples, wherein the guidance sleeve includes a frustoconical guide surface at an upper end of the guidance sleeve that is configured to guide the plug intervention tool into the guidance sleeve.

Example 18: A plug intervention system for retrieving or installing a plug for a subsea wellhead assembly, the plug intervention system comprising: a cap that is configured to engage with a connection hub of the subsea wellhead assembly, where the connection hub includes a bore that is in communication with a plug seat; and a guidance sleeve that is coupled to the cap, where the guidance sleeve is configured to be inserted into the bore when the cap is engaged with the connection hub such that the guidance sleeve extends through the bore toward the plug seat.

Example 19: The plug intervention system of any of the Examples, wherein the guidance sleeve has an upper end and a lower end opposite the upper end, wherein the lower end of the guidance sleeve is configured to be inserted into the bore when the cap is engaged with the connection hub, and wherein the upper end of the guidance sleeve is positioned outside of the cap.

Example 20: The plug intervention system of any of the Examples, wherein the upper end of the guidance sleeve comprises a frustoconical guide surface that is configured to guide a plug intervention tool into the guidance sleeve.

Example 21: The plug intervention system of any of the Examples, wherein the cap includes a plurality of latch assemblies that are configured to engage with an outer surface of the connection hub to secure the cap to the connection hub.

Example 22: The plug intervention system of any of the Examples, wherein the plurality of latch assemblies comprises a plurality of set screws that are configured to be actuated by a remotely operated vehicle (ROV) in a subsea environment.

Example 23: The plug intervention system of any of the Examples, wherein the cap includes one or more seals that are configured to sealingly engage with the connection hub to isolate the bore.

Example 24: A plug intervention system for retrieving or installing a plug for a subsea wellhead assembly, the plug intervention system comprising: a cap that is configured to engage with a connection hub of the subsea wellhead assembly, where the connection hub includes a bore that is in communication with a plug seat; a plug intervention tool that is configured to engage with the plug; and a linear actuator coupled to the plug intervention tool and the cap, where the linear actuator is configured to translate the plug intervention tool within the bore when the cap is engaged with the connection hub.

Example 25: The plug intervention system of any of the Examples, wherein the linear actuator comprises a hydraulic cylinder.

Example 26: The plug intervention system of any of the Examples, wherein the linear actuator comprises a screw actuator.

Example 27: The plug intervention system of any of the Examples, wherein the cap includes a plurality of latch assemblies that are configured to engage with an outer surface of the connection hub to secure the cap to the connection hub.

Example 28: The plug intervention system of any of the Examples, wherein the plurality of latch assemblies comprises a plurality of set screws that are configured to be actuated by a remotely operated vehicle (ROV) in a subsea environment.

Example 29: The plug intervention system of any of the Examples, wherein the cap includes one or more seals that are configured to sealingly engage with the connection hub to isolate the bore.

Example 30: A method comprising: (a) lowering a cap of a plug intervention system into a subsea environment to a subsea wellhead assembly; (b) receiving a connection hub of the subsea wellhead assembly into a cavity of the cap; (c) inserting a plug intervention tool into a bore of the connection hub by use of a guidance assembly that is connected to an upper end of the cap; and (d) installing a plug into or retrieving the plug from a plug seat in the subsea wellhead assembly by use of the plug intervention tool.

Example 31: The method of any of the Examples, wherein the guidance assembly comprises a guidance sleeve that is connected to the upper end of the cap, and wherein the method further comprises: (e) inserting the guidance sleeve into the bore during (b), wherein (c) further comprises translating the plug intervention tool through the guidance sleeve.

Example 32: The method of any of the Examples, wherein (c) further comprises: (c1) lowering the plug intervention tool into the subsea environment after (a); and (c2) inserting the plug intervention tool into an upper end of the guidance sleeve, wherein the upper end of the guidance sleeve is positioned outside of the cap.

Example 33: The method of any of the Examples, wherein (c) comprises translating the plug intervention tool within the bore with a linear actuator that is connected to the upper end of the cap.

Example 34: The method of any of the Examples, wherein (a) further comprises lowering the cap and the linear actuator into the subsea environment.

Example 35: The method of any of the Examples, further comprising: (f) sealingly engaging the cap with the connection hub to isolate the bore; and (g) pressurizing the bore to set the plug into a plug seat in the subsea wellhead assembly.

• • Example 36: The method of any of the Examples, wherein (c) further comprises actuating the linear actuator by use of a remotely operated vehicle (ROV).
  • Example 37: The method of any of the Examples, wherein (d) further comprises installing the plug by jarring the plug with the plug intervention tool to deploy one or more locking dogs of the plug with the plug seat.

Embodiments disclosed herein include plug intervention systems that may be configured to install and/or remove one or more plugs, such as a crown plug, in a subsea wellhead system. In some embodiments, the plug intervention systems may be configured to engage with a connection hub of the subsea wellhead assembly in an open-water arrangement that is free from additional pressure barriers between the plug(s) and the surrounding subsea environment. Thus, the plug intervention systems may be smaller, lighter, and less expensive than a conventional intervention system, which may include additional pressure barriers and control mechanisms for selectively closing the wellbore in the event of an emergency as previously described. In some embodiments, the plug intervention systems may be configured to remove or install the crown plug of the subsea wellhead assembly so that a separate intervention assembly may then be used to remove (and later install) the additional (and smaller) plugs. As a result, through use of the embodiments disclosed herein, a well operator may deploy intervention systems that may not be suitable for removing or installing a larger crown plug for the intervention operation of the subsea wellbore.

The preceding discussion is directed to various embodiments. However, one of ordinary skill in the art will understand that the examples disclosed herein have broad application, and that the discussion of any embodiment is meant only to be exemplary of that embodiment, and not intended to suggest that the scope of the disclosure, including the claims, is limited to that embodiment.

The drawing figures are not necessarily to scale. Certain features and components herein may be shown exaggerated in scale or in somewhat schematic form and some details of conventional elements may not be shown in interest of clarity and conciseness.

In the preceding discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to . . . .” Also, the term “couple” or “couples” is intended to mean either an indirect or direct connection. Thus, if a first device couples to a second device, that connection may be through a direct connection of the two devices, or through an indirect connection that is established via other devices, components, nodes, and connections. In addition, as used herein, the terms “axial” and “axially” generally mean along or parallel to a given axis (e.g., central axis of a body or a port), while the terms “radial” and “radially” generally mean perpendicular to the given axis. For instance, an axial distance refers to a distance measured along or parallel to the axis, and a radial distance means a distance measured perpendicular to the axis. Further, when used herein (including in the claims), the words “about,” “generally,” “substantially,” “approximately,” and the like, when used to refer to a stated value, mean within a range of plus or minus 10% of the stated value.

While exemplary embodiments have been shown and described, modifications thereof can be made by one skilled in the art without departing from the scope or teachings herein. The embodiments described herein are exemplary only and are not limiting. Many variations and modifications of the systems, apparatus, and processes described herein are possible and are within the scope of the disclosure. Accordingly, the scope of protection is not limited to the embodiments described herein, but is only limited by the claims that follow, the scope of which shall include all equivalents of the subject matter of the claims. Unless expressly stated otherwise, the operations in a method claim may be performed in any order. The recitation of identifiers such as (a), (b), (c) or (1), (2), (3) before operations in a method claim are not intended to and do not specify a particular order to the operations, but rather are used to simplify subsequent reference to such operations.