Shearable Wedge Component for Rigidizing Seal

Description

TECHNICAL FIELD

The present disclosure relates generally to seal assemblies used to secure a casing hanger within a wellhead and, more particularly, to a seal assembly having a shearable wedge component used to rigidize the seal between the casing hanger and the wellhead.

BACKGROUND

Conventional wellhead systems include a wellhead housing and a subsurface casing string extending from the wellhead into the well bore. During a drilling procedure, a drilling riser and BOP are installed above a wellhead housing to provide pressure control as casing is installed, with each casing string having a casing hanger on its upper end for landing on a shoulder within the wellhead housing.

For various reasons, a casing hanger within the wellhead may move axially upward, particularly when the wellhead is part of a production system where downhole fluids at elevated temperatures thermally expand the casing string and thus exert a substantial upward force on the casing hanger. Since the casing hanger seal is intended for sealing at a particular location on the wellhead, upward movement of the casing hanger and the seal assembly is detrimental to reliably sealing the casing annulus. A lockdown component can be used to prevent axial movement of the casing hanger in response to such axial forces.

Various types of lockdown components have been conceived for axially interconnecting a casing hanger and a subsea wellhead. The lockdown component (e.g., a lockdown sleeve) may be incorporated into the seal assembly. Such a seal assembly, once run in and locked into the wellhead, prevents axial (i.e., vertical) movement of the uppermost casing hanger and the seal with respect to the wellhead. Typically, a seal assembly is run into the wellhead on an associated running tool, landed on the casing hanger, and locked to a locking profile on an inner wall of the wellhead housing to axially secure the casing hanger within the wellhead. To install conventional seal assemblies, it is first necessary to run a lead impression tool into the wellhead to measure the distance between the top of the casing hanger and the housing locking profile. After retrieving the lead impression tool to the surface, the measured dimension can be obtained. With this information, the seal assembly length can be adjusted at the surface so that once the seal assembly is run in and secured to the wellhead, it provides a zero-gap connection between the casing hanger and the wellhead housing and any desired pre-load.

This process of taking measurements in the wellhead via a lead impression tool, retrieving the tool to the surface, and then adjusting and installing a seal assembly into the wellhead is a time-consuming installation process requiring multiple trips into the wellhead. It is now recognized that a need exists for a seal assembly that can be adjusted once it is already landed in the wellhead.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure and its features and advantages, reference is now made to the following description, taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a cross-sectional view of a system including a casing hanger secured in a wellhead using a seal assembly with a wedge component for rigidizing a seal, in accordance with an embodiment of the present disclosure;

FIG. 2 is a cross-sectional view of the system of FIG. 1 with the seal assembly in a run in position, in accordance with an embodiment of the present disclosure;

FIG. 3 is a cross-sectional view of the system of FIG. 1 with the seal assembly in an initial locked position, in accordance with an embodiment of the present disclosure;

FIG. 4 is a cross-sectional view of the system of FIG. 1 with the seal assembly in a fully installed position with a rigidized seal, in accordance with an embodiment of the present disclosure; and

FIG. 5 is a cross-sectional view of the system of FIG. 1 showing an interface of the wedge component and a spacer component, in accordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION

Illustrative embodiments of the present disclosure are described in detail herein. In the interest of clarity, not all features of an actual implementation are described in this specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation specific decisions must be made to achieve developers' specific goals, such as compliance with system related and business related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of the present disclosure. Furthermore, in no way should the following examples be read to limit, or define, the scope of the disclosure.

Certain embodiments of the present disclosure may be directed to a seal assembly equipped with a wedge component for rigidizing a seal.

A seal assembly may be used to position a seal between a casing hanger and a wellhead housing and to axially interconnect the casing hanger to the wellhead. The seal assembly may be locked into the wellhead, thereby preventing axial movement of the casing hanger, and the seal, with respect to the wellhead.

In some cases, machining tolerances may give rise to small gaps between a locking mechanism (e.g., lock ring) of the seal assembly and an upper edge of a complementary lock profile of the wellhead when the seal assembly is landed and locked to seal the annulus between the casing hanger and the wellhead. Such gaps may allow the seal located between the casing hanger and the wellhead to move up and down axially in response to pressure differentials. Over time, this motion of the seal can cause undesirable wear on the seal.

The disclosed seal assembly overcomes these deficiencies by using a wedge component to reduce any axial gaps, thereby rigidizing the system. The seal assembly is configured to retain a casing hanger within a wellhead. The seal assembly generally includes a main body, a lock ring coupled to the main body, and a wedge shaped component coupled to the main body and located under the lock ring. The lock ring is configured to expand radially outward into a profile on an inner diameter of the wellhead. The wedge shaped component has a tapered upward facing surface that is capable of causing the lock ring to move axially upward in response to radially outward movement of the wedge shaped component. This axially upward movement transferred to the lock ring helps to close any axial gap between the lock ring and the wellhead profile (and applying any desired pre-load), thus rigidizing the seal. The installation process for the seal assembly may be accomplished during one trip into the wellhead, as opposed to a first trip with a lead impression tool followed by an adjustment of a lockdown component of the seal assembly at the surface and a subsequent trip downhole to install the adjusted seal assembly. The disclosed systems and method provide both time savings (since only one trip into the wellhead is necessary) and cost savings (since an additional lead impression tool is not required) compared to existing seal assembly installation techniques. In addition, the seal assembly having a wedge shaped component is easy to construct and operate compared to other, more complicated lockdown assemblies that utilize rotating components, etc. All these and other advantages will be apparent based on the following description.

Turning now to the drawings, FIG. 1 illustrates certain components of a wellhead system 100. The illustrated system 100 may include a subsea wellhead assembly. However, similar techniques may be used in land-based wellhead systems as well. The wellhead assembly may include a wellhead 102 (with high-pressure housing), an outer low-pressure housing 104, a lower casing hanger 106 landed within the wellhead 102 and supporting an outer casing string 108, and an upper casing hanger 110 landed on the lower casing hanger 106 and supporting an inner casing string 112. A c-ring 114 or other attachment mechanism may support the lower casing hanger 106 and thus the outer casing string 108 from the wellhead 102.

A seal assembly 116 may be installed in the wellhead 102 and used for retaining the upper casing hanger 110 within the wellhead 102. In particular, the seal assembly 116 may be installed at an interface of the top of the upper casing hanger 110 and the wellhead 102. The seal assembly 116 may include a seal 118 at a lower end thereof. The seal 118 may seal between the upper portion of the upper casing hanger 110 and the wellhead 102, thereby sealing the annulus about the inner casing string 112. The lower casing hanger 106 may have its own seal 120 as well for sealing with the wellhead 102. The wellhead 102, casing strings, and casing hangers as described are functionally similar to existing wellhead and casing hanger technologies. The wellhead system 100 in FIG. 1 is typically used during production operations, and frequently a blowout preventer (BOP) or tieback connector is provided at the upper end of the wellhead 102.

In addition to positioning the seal 118, the seal assembly 116 is configured to prevent axial movement between the upper casing hanger 110 (and the seal 118) and the wellhead 102. The seal assembly 116 includes a lock ring (or similar locking component) 122 that locks into an internal locking profile 124 on a bore of the wellhead 102. The seal assembly 116 may be landed on the upper casing hanger 110 to secure and/or provide a pre-load to the casing hanger 110 in a downward direction.

The seal assembly 116 further includes a wedge shaped component configured to help make up any gap in an axial direction (e.g., parallel to axis 128 of the wellhead 102) between the lock ring 122 and an upper edge of the internal locking profile 124. Removing any such gap via movement of the wedge shaped component 126 and resulting movement of the lock ring 122 rigidizes the seal 118 at a desired location with respect to the wellhead 102. Once the seal assembly 116 is installed (i.e., landed, locked, and axially adjusted via the wedge shaped component 126 as needed to make up any gap), the seal 118 and the casing hanger 110 are prevented from moving upward or downward with respect to the wellhead 102 via the connection of the seal assembly 116 with the casing hanger 110 and the wellhead 102. Thus, the disclosed system may deter movement of the seal 118 in an axial direction via the connection between the casing hanger 110, the seal assembly 116, and the wellhead 102.

A description of the process for installing the seal assembly 116 will now be provided, with reference to FIGS. 2-4. These figures each show a different step in the installation process for the seal assembly 116 of FIG. 1.

FIG. 2 illustrates the seal assembly 116 in a run in position within the wellhead 102. As shown in FIG. 2, the seal assembly 116 generally includes a main body 200, the lock ring 122, and the wedge shaped component 126. The lock ring 122 is coupled to the main body 200 and configured to expand radially outward (relative to the main body 200) into the profile 124 on an inner diameter 202 of the wellhead 102. The wedge shaped component 126 is coupled to the main body 200 and located under the lock ring 122. The wedge shaped component 126 has a tapered upward facing surface 204 that is capable of causing the lock ring 122 to move axially upward in response to radially outward movement of the wedge shaped component 126. In particular, the tapered upward facing surface 204 may be tapered in a downward direction from a radially inner side (e.g., facing toward the axis 128 of FIG. 1) of the wedge shaped component 126 to a radially outer side (e.g., facing away from the axis 128 of FIG. 1) of the wedge shaped component 126.

In some embodiments, as illustrated, the wedge shaped component 126 may also have a tapered downward facing surface 206, which is tapered in an opposite direction of the upward facing surface 204 of the wedge shaped component 126. In other embodiments, the wedge shaped component 126 may have a substantially horizontal downward facing surface. As shown in FIG. 2, an angle of the tapered upward facing surface 204 with respect to a horizontal plane may be approximately equal to and opposite of an angle of the tapered downward facing surface 206 with respect to the horizontal plane. That is, the tapered upward and downward facing surfaces 204 and 206 may have equivalent tapers in opposite directions, forming a more pronounced wedge shape for the wedge shaped component 126.

The wedge shaped component 126 may have a largest dimension 208 in an axial direction (e.g., parallel to axis 128 of FIG. 1) that is between approximately 2 cm and 6 cm. This dimension may be equal to or greater than a maximum amount of gap that may be present between the lock ring 122 and an upper edge of the wellhead internal profile 124 upon initial actuation of the lock ring 122 (e.g., as shown in FIG. 3). In some embodiments, the maximum amount of gap that may be taken up by the wedge shaped component may be approximately 1.27 cm. The wedge shaped component 126 may be constructed from a high strength material such as, for example, high strength alloy steels.

In certain embodiments, the wedge shaped component 126 may be a radially expandable split ring having a wedge shaped cross-section. A radially expandable split ring is a ring of material having a substantially consistent cross-section, with the ring being non-continuous (e.g., having a break at one circumferential position of the ring). This break in the ring allows the split ring to expand and compress radially in response to forces on the split ring. The wedge shaped component 126 (e.g., split ring) may be in a neutral (e.g., not radially compressed or expanded) position in FIG. 2. Alternatively, the wedge shaped component 126 (e.g., split ring) may be slightly radially expanded in the run-in position of FIG. 2, such that the wedge shaped component 126 is biased in a radially inward direction. In other embodiments, the wedge shaped component 126 may include one or more separate (i.e., not connected) wedge shaped pieces of material that are arranged between the main body 200 and the lock ring 122. Other possible arrangements of the wedge shaped component(s) 126 may be recognized by those having ordinary skill in the art.

In certain embodiments, the seal assembly 116 may include a spacer component 210 disposed between the wedge shaped component 126 and the lock ring 122. The spacer component 210 has a tapered downward facing surface 212 shaped to interface with the tapered upward facing surface 204 of the wedge shaped component 126. As shown in FIG. 2, an angle of the tapered downward facing surface 212 with respect to a horizontal plane may be approximately equal to the angle of the tapered upward facing surface 204 with respect to the horizontal plane, so that the wedge shaped component 126 and the spacer component 210 maintain a secure engagement with each other during radial movement of the wedge shaped component 126. An upward facing surface 214 of the spacer component 210 may be substantially horizontal (not tapered), as shown. The spacer component 210 may take the form of a continuous ring having a cross-section with the tapered downward facing surface 212.

In certain embodiments, the seal assembly 116 may not include the spacer component, but rather a lower end of the lock ring 122 may have a tapered downward facing surface capable of interfacing directly with the tapered upward facing surface 204 of the wedge shaped component 126. As such, the spacer component may be fully integrated into the lock ring 122. In either case, the wedge shaped component 126 is configured to interface directly with a tapered downward facing surface (e.g., 212) of a component located above the wedge shaped component 126 so as to provide a smooth transfer of force to the lock ring 122 in an upward direction in response to radially outward movement of the wedge shaped component 126.

The seal assembly 116 may also include the seal 118 coupled to the main body 200. As illustrated, the seal 118 may form a lower portion of the seal assembly 116 that is coupled (e.g., via threads 216) to a lower end of the main body 200.

The seal assembly 116 may also include an actuator 218 configured to actuate the lock ring 122 into a radially outward locking position (e.g., as shown in FIG. 3). The actuator 218 may take the form of an actuator sleeve that, when pushed downward (e.g., via a running tool 220), causes the lock ring 122 to expand radially outward. The actuator 218 may include a substantially stepped profile on its outer diameter. The stepped profile may help to actuate different components of the seal assembly 116 (e.g., lock ring 122, wedge shaped component 126) at different times using the same actuator 218. The stepped profile may include tapered steps along the outer diameter of the actuator 218.

As illustrated, the actuator 218 may include a reduced diameter portion 222 formed therein, below the stepped profile. The wedge shaped component 126 may include a radially inward facing portion 224 that extends into an annular cavity defined by this reduced diameter portion 222 of the actuator 218. As such, in the run in position, the wedge shaped component 126 may protrude farther in a radially inward direction than the main body 200 and/or the spacer component 210. The radially inward facing portion 224 of the wedge shaped component 126 may be in contact with or otherwise fit close to the reduced diameter portion 222 of the actuator 218 while the seal assembly 116 is in the run in position.

FIG. 2 shows the relative positioning of various components of the seal assembly 116 while the seal assembly 116 is being positioned into the wellhead 102. This is prior to the actuator 218 actuating either the lock ring 122 or the wedge shaped component 126. As illustrated, in this run in configuration, the actuator 218, lock ring 122, spacer component 210, wedge shaped component 126, and main body 200 are positioned such that the entire seal assembly 116 is located radially inward from the inner diameter 202 of the bore of the wellhead 102. The seal assembly 116 remains in this configuration until it is landed atop the casing hanger 110.

FIG. 3 illustrates the seal assembly 116 in an initial locked position within the wellhead 102. Once the seal assembly 116 is lowered and landed on the casing hanger 110, the lock ring 122 may be actuated toward the internal locking profile 124 on the inner diameter 202 of the wellhead 102. In particular, the actuator 218 is pushed downward (e.g., via a setting force from weight or hydraulic fluid) to actuate the lock ring 122. An interface between the actuator 218 and the lock ring 122 may be capable of transferring an axial (i.e., downward) force from the actuator 218 into outward radial expansion of the lock ring 122. In particular, the stepped profile on the radially outer surface of the actuator 218 may interact with a similarly stepped or tapered profile on a radially inner surface of the lock ring 122 to push the lock ring 122 outward. FIG. 3 shows the lock ring 122 in this radially expanded position.

In general, the lock ring 122 may be a radially expandable split ring having a radially outer profile 300 configured to match the profile 124 on the wellhead 102. A radially expandable split ring is a ring of material having a substantially consistent cross-section, with the ring being non-continuous (e.g., having a break at one circumferential position of the ring). This break in the ring allows the lock ring 122 to expand radially outward in response to force from the actuator 218.

As illustrated in FIG. 3, when the lock ring 122 is initially actuated into this radially expanded position, a gap 302 in an axial (e.g., vertical) direction may be present between an uppermost edge of the lock ring 122 and a corresponding uppermost edge of the profile 124 of the wellhead 102. It is desirable to close this gap 302 between the lock ring 122 and the profile 124 so that the seal assembly 116 is able to secure the connection between the casing hanger 110 and the wellhead 102 and rigidize the seal 118.

As shown in FIG. 3, in the initial locked position, the radially inward facing portion 224 of the wedge shaped component 126 may still extend into the annular cavity defined by the reduced diameter portion 222 of the actuator 218. However, since the actuator 218 has moved downward, the wedge shaped component 126 is now located at a higher relative position within the cavity defined by the reduced diameter portion 222. At least part of the radially inward facing portion 224 of the wedge shaped component 126 may be sheared in response to an axial (e.g., downward) force from the actuator 218 as the actuator 218 continues to move downward. To aid in this shearing process, the wedge shaped component 126 may include relief cuts 226 formed in the radially inward facing portion 224. Such relief cuts 226 may have minimal effect on the bearing capacity of the wedge shaped component 126 while lowering the shear force required to shear the material of the wedge shaped component 126, thereby inducing shear in the area of the radially inward facing portion 224. In addition, the actuator 218 may include a cutting edge 228 formed thereon. The cutting edge 228 may be configured to shear at least part of the radially inward facing portion 224 of the wedge shaped component 126. As shown, the cutting edge 228 may be located on a downward facing edge on an outer diameter of the actuator 218 located above the reduced diameter portion 222.

FIG. 4 illustrates the seal assembly 116 in a fully installed position within the wellhead 102. During installation of the seal assembly 116, as the actuator 218 is moved further in an axial (e.g., downward) direction, the actuator 218 drives the wedge shaped component 126 radially outward. That is, the radially outward edges of the stepped profile of the actuator 218 may contact and apply a radially outward force on the radially inward facing portion 224 of the wedge shaped component 126. As such, during or after actuating the lock ring 122 (e.g., as in FIG. 3), the wedge shaped component 126 moves in a radially outward direction relative to the main body 200 of the seal assembly 116. This radially outward movement of the wedge shaped component 126 causes the lock ring 122 to move axially upward, thereby closing the gap (e.g., 302 of FIG. 3) between the uppermost portion of the lock ring 122 and the corresponding uppermost portion of the profile 124 of the wellhead 102. Movement of the wedge shaped component 126 in this manner adjusts the axial length of the entire seal assembly 116 to fill the gap. As such, there is no gap between the uppermost edge of the lock ring 122 and the uppermost edge of the profile 124 of the wellhead 102 after adjustment of the axial length of the seal assembly 116 in this manner.

In embodiments having a spacer component 210, the spacer component 210 moves axially upward in response to the radially outward movement of the wedge shaped component 126 based on the interaction of the tapered surfaces of the spacer component 210 and the wedge shaped component 126. The spacer component 210 is moved upward until the lock ring 122 above the spacer component 210 is contacting the uppermost portion of the profile 124 of the wellhead 102.

Depending on the size of the gap (e.g., 302 of FIG. 3), if any, between the lock ring 122 and the wellhead profile 124, the wedge shaped component 126 may not fully expand in the radially outward direction. That is, the wedge shaped component 126 may not expand until its radially inward facing portion 224 is aligned with or otherwise located at a same radial location as a radially inward facing portion 400 of the main body 200. Put another way, at least part of the radially inward facing portion 224 of the wedge shaped component 126 may still extend into the cavity defined by the reduced diameter portion 222 of the actuator 218 after actuating the wedge shaped component 126 to make up the entire gap. In this scenario, the “excess” material of the radially inward facing portion 224 of the wedge shaped component 126 may be sheared off by further downward travel of the actuator 218. The radially inward facing portion 224 of the wedge shaped component 126 may be sheared via the actuator 218 used to actuate the lock ring 122, in particular, after the lock ring 122 interfaces with the profile 124 on the inner diameter 202 of the wellhead 102. The sheared off inward facing portion 224 of the wedge shaped component 126 may be held within the cavity defined by the reduced diameter portion 222 of the actuator 218, as shown.

The configuration of the wedge shaped component 126 that allows for excess material to be sheared off may be beneficial because the inner diameter of the wedge shaped component 126 would be fully backed up and supported by the seal assembly 116. Shearing off this portion of the wedge shaped component 126 enables full contact to be made between the actuator 218 and the rest of the seal assembly 116 atop the casing hanger 110, thereby fully supporting the connection.

FIG. 4 shows the seal assembly 116 in a fully locked and rigidized configuration within the wellhead 102. In this position, the seal assembly 116 is able to retain the casing hanger 110 in the wellhead 102 and rigidize the connection between the casing hanger 110, the wellhead 102, and the seal 118.

FIG. 5 illustrates an embodiment of the seal assembly 116 having the wedge shaped component 126, main body 200, and spacer component 210, similar to the seal assembly 116 discussed above. The spacer component 210 (or lock ring 122 in other embodiments) may be movably coupled to the main body 200 of the seal assembly 116 via one or more shoulder bolts 500. The one or more shoulder bolts 500 may maintain the spacer component 210 (or lock ring 122) in connection with the main body 200 of the seal assembly 116. For example, as shown, the one or more shoulder bolt(s) 500 may include threads 502 connected to the spacer component 210 (or lock ring 122) and an unthreaded portion 504 extending downward into an aperture 506 formed in the main body 200. In other embodiments, the one or more shoulder bolt(s) 500 may be in a reversed configuration such they are connected to the main body 200 via threads and have an unthreaded portion extending upward into an aperture formed in the spacer component 210 (or lock ring 122). Either shoulder bolt configuration allows the spacer component 210 (or lock ring 122) to travel axially with respect to the main body 200. The wedge shaped component 126 may include one or more cutouts 508 formed therein to enable the wedge shaped component 126 to move in a radially outward direction with respect to the one or more shoulder bolt(s) 500, thereby allowing for axial adjustment of the seal assembly 116 as described above. These one or more cutouts 508 may be in the form of scallops used to clear the shoulder bolt(s) 500.

Although the present disclosure and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the disclosure as defined by the following claims.