Metal to metal annulus seal with enhanced lock-down capacity

In accordance with embodiments of the present disclosure, a seal assembly for sealing and locking a casing hanger to a wellhead includes a lower seal body, an upper seal body connected to the lower seal body, an inner lock ring disposed between the upper seal body and the lower seal body, an external lock ring engaging the upper seal body, and an energizing ring. The lower seal body is structured and arranged to form a seal with the casing hanger and the wellhead. The upper seal body includes a load portion that overhangs a load shoulder of the casing hanger. At least a portion of the energizing ring is disposed within an inner groove disposed within the upper seal body. The energizing ring locks the inner lock ring into forcible engagement with the casing hanger, and locks the external lock ring into engagement with the wellhead.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a non-provisional patent application of U.S. provisional application Ser. No. 62/118,365, entitled “Metal to Metal Annulus Seal with Enhanced Lock-down Capacity”, filed on Feb. 19, 2015.

BACKGROUND

The present disclosure relates to a hanger system for connecting a casing hanger to a wellhead. More particularly, the present disclosure relates to a seal assembly implemented in conjunction with connecting a casing hanger to a wellhead.

Various types of seal assemblies have been devised for sealing between a casing hanger and a wellhead. Some seal assemblies are suitable for either high temperature or high pressure application, but not both high temperature and high pressure applications. Other seal assemblies are only suitable for modest temperature and pressure applications. Other seal assemblies initially form a seal, but over time lose their sealing effectiveness.

U.S. Pat. No. 7,096,956 discloses a downhole tool for activating a seal assembly, the entirety of which is incorporated herein by reference. In addition, U.S. Pat. No. 6,202,745 discloses a casing hanger positioned within a wellhead, the entirety of which is incorporated herein by reference.

Most downhole wellhead-hanger seal assemblies are manufactured from two or more components which make up the seal body. The seal body supports one or more seals that seal with the wellhead and the casing hanger. In many cases, these components are interconnected by threads, which inherently allow axial travel between components. The axial travel between seal body components results in wear on both the seals and the sealing surfaces. Additionally, high seal setting forces are conventionally difficult to transmit through a seal body with threaded components.

Another significant problem with prior art sealing assemblies is that when fluid pressure is applied from below the set seal assembly, the interior wellhead wall expands radially outward, and the exterior hanger wall contracts radially inward, thereby creating a significant increase in the radial gap, which inherently detracts from sealing effectiveness. The disadvantages of this created gap are particularly significant when high downhole pressure is applied from below the seal assembly.

The disadvantages of the prior art are overcome by the methods and systems disclosed herein which are generally directed to an improved seal assembly and lockdown method of implementing the same.

DETAILED DESCRIPTION

The present disclosure relates to a hanger system for connecting a hanger to a wellhead. More particularly, the present disclosure relates to a lock and seal hanger system for connecting the hanger to the wellhead.

Illustrative embodiments of the present disclosure are described in detail herein. In the interest of clarity, not all features of an actual implementation may be 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 the specific implementation goals, 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. To facilitate a better understanding of the present disclosure, the following examples of certain embodiments are given. In no way should the following examples be read to limit, or define, the scope of the disclosure.

The terms “couple” or “couples,” as used herein are 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, or through an indirect electrical connection via other devices and connections. Further, if a first device is “fluidically coupled” to a second device there may be a direct or an indirect flow path between the two devices. The term “uphole” as used herein means along the drillstring or the hole from the distal end towards the surface, and “downhole” as used herein means along the drillstring or the hole from the surface towards the distal end. However, the use of the terms “uphole” and “downhole” is not intended to limit the present disclosure to any particular wellbore configuration as the methods and systems disclosed herein may be used in conjunction with developing vertical wellbores, horizontal wellbore, deviated wellbores or any other desired wellbore configurations.

Referring toFIG. 1, a seal assembly100is shown disposed between a wellhead102and a casing hanger101positioned within the wellhead102. The wellhead102includes an inner generally cylindrical surface103, while the casing hanger101includes a tapered outer surface104. The seal assembly100may seal between the tapered outer surface104of the casing hanger and the wellhead inner surface103. The seal may also seal against a flat outer surface of the casing hanger. Lower seal body114is a unitary component positioned between the wellhead102and the casing hanger101. In certain embodiments, the lower seal body114may be capable of sealing at least 20,000 psi from above and at least 15,000 psi from below the lower seal body114. However, the present disclosure is not limited as such and these numbers are provided as illustrative examples only. In certain embodiments, the lower seal body114may be a homogeneous component.

The lower seal body114may comprise a radially outward projecting member136, which has annular bumps138and140at its upper and lower ends for sealing engagement with the wellhead inner surface103. A gap142between a portion of the projecting member136and the lower seal body114provides for limited outward deflection of the bump138at the upper end of member136when pressure is applied to the seal assembly from above, while a similar gap144allows limited outward deflection of annular bump140when fluid pressure is applied to the seal assembly from below. The lower seal body114may comprise seals151and152on the inner surface of the lower seal body114, each formed from an annular metal bump for sealing engagement with the hanger outer surface104. In certain embodiments, gaps between the hanger outer surface104and the lower seal body114may be filled with one or more elastomeric O-rings.

The lower seal114may comprise a protector element146, disposed below the projecting member136. The protector element146may provide a radially outer surface147which acts as a protector to eliminate or at least minimize damage to the projecting member136when the seal assembly100is pushed between the inner surface103of the wellhead102and the tapered surface104of the casing hanger101, since the outer diameter of protector element146is substantially as large as the outer diameter of member136. Positioned lower than member136, protector element146contacts the interior wall103of the wellhead102when the seal assembly100is pressed in place. The protector element146may also serve to prevent crushing of the lower seal body114when fluid pressure from above the seal assembly100acts to force the lower seal body114radially outward. The protector element146may act to withstand a high radially outward force on the lower seal body114to prevent the sealing surfaces from being crushed so that the seal assembly100no longer seals. Even though forces which create a gap and detract from sealing effectiveness are greater when fluid pressure is from below, in certain embodiments, the seal assembly100may be able to reliably seal while withstanding a high fluid pressure from both above and below.

The lower seal body114may comprise at least one puller mechanism115for initially sealing with the wellhead inner surface103, such that fluid pressure above the puller mechanism115pulls the seal assembly100downward. The puller mechanism115may create an initial seal which allows pressure buildup when a force tool pushes the seal assembly100into the set position. Further details regarding a seal puller mechanism are disclosed in U.S. Pat. No. 6,705,615, which is incorporated herein by reference in its entirety.

The lower seal body114may support an inner lock ring118. The inner lock ring118may be one unitary piece split ring which locks the lower seal body114to the casing hanger101. The inner lock ring118may be disposed between the lower seal body114and an upper seal body116. For example, the lower seal body114and the upper seal body116may form a pocket that contains the inner lock ring118.

The upper seal body116may comprise a unitary body which provides structural integrity to the seal assembly100and is capable of inhibiting bending forces exerted on the seal assembly100. In certain embodiments, when the upper seal body116is actuated as shown inFIG. 1, the seal assembly100may maintain the integrity of the seal at extreme axial loads. One non-limiting illustrative example may be an implementation where the seal assembly100may withstand an axial load of at least 2 million pounds. Another non-limiting illustrative example may be an implementation where the seal assembly100may maintain the seal under an axial load of from 1.5 million to 2 million pounds. In certain embodiments, the upper seal body116may comprise a running notch162for running and/or retrieving the seal assembly100, for example using a running tool (not shown).

In certain embodiments, the upper seal body116may interlock with the lower seal body114. For example, a thread164may connect the lower seal body114to the upper seal body116. The thread164may be located on the lower seal body114and configured to engage the upper seal body116, or the thread164may be located on the upper seal body116and configured to engage the lower seal body114. When the upper seal body116and the lower seal body114are connected (e.g., via the thread connection164) the two seal bodies114,116create a pocket that contains the inner lock ring118.

The upper seal body116may comprise an annular stop126for engagement with a lower portion of an external lock ring106. In certain embodiments, the annular stop126may be disposed on the outer diameter of the upper seal body116. The external lock ring106may comprise a single piece split ring, which may be run in a collapsed state and expanded into lockdown grooves127in the wellhead102, preventing upward movement of the casing hanger101and seal assembly100. The external lock ring106may be supported by an external ring load shoulder165disposed on the upper seal body116.

The seal assembly100may comprise an energizing ring120extending within the upper seal body116, and engaging the external lock ring106. The energizing ring120may comprise a solid upper ring section121, which may provide hoop strength that is capable of preventing inward collapse of the energizing ring120and/or the seal assembly100. The energizing ring120may comprise a milled lower section122that may be inserted into an inner groove117of the upper seal body116.

Referring briefly toFIGS. 2A and 2B, an embodiment of an energizing ring300is shown comprising a solid upper section310and a milled lower section320. The lower section320may comprise a plurality of fingers322spaced radially on the energizing ring300. In certain illustrative embodiments, the energizing ring300may comprise 4 to 100 fingers, although the present disclosure is not limited to any particular number of fingers. For example, as shown inFIGS. 2A and 2B, the energizing ring300may comprise twenty-four (24) fingers. In certain embodiments, the fingers322may be equally spaced on the energizing ring300.

Referring briefly toFIGS. 3A and 3B, an embodiment of the upper seal body400is shown comprising a plurality of inner slots410spaced radially on the upper seal body400. In certain illustrative embodiments, the upper seal body400may comprise 4 to 100 inner slots410, although the present disclosure is not limited to any particular number of inner slots410. Each of the plurality of inner slots410may be capable of accepting a corresponding finger of an energizing ring, such as shown inFIGS. 2A and 2B. For example, the number of inner slots410may correspond to the number of fingers on the energizing ring. For example, the upper seal body400may comprise twenty-four (24) inner slots410, as shown inFIGS. 3A and 3B, where the energizing ring also comprises 24 fingers.

Referring briefly toFIGS. 4A and 4B, an embodiment is shown comprising an upper seal body510and an energizing ring520inserted and engaging the upper seal body510in an actuated configuration. When in the actuated configuration, each of a plurality of fingers522may be inserted into a corresponding inner groove of the plurality of inner slots.

Referring toFIG. 5, the dual lock seal assembly100ofFIG. 1is shown in a non-actuated configuration while being run toward a casing hanger101. The seal assembly100includes an energizing ring120extending into the inner groove117, but not engaging the inner lock ring118and without displacing the external lock ring106outward. In certain embodiments, on approach to the casing hanger101, the seal assembly100may comprise one or more shear pins130press fit into an upper seal body116and through the energizing ring120to prevent early deployment of the energizing ring120into the upper seal body116.

Referring toFIG. 6, the seal assembly100is shown engaging the casing hanger101and the wellhead102, while remaining in a non-actuated configuration. In certain embodiments, the seal assembly100may remain in the non-actuated configuration while engaging the casing hanger101and the wellhead102until an operator desires to actuate the seal assembly100. While in the non-actuated configuration, the lower seal body114may form a seal with the casing hanger101and wellhead102, but provides no lockdown.

Referring back toFIG. 1, the seal assembly100may be locked into place by actuating the energizing ring120downward where the lower section122is inserted into the inner groove117and engages the inner lock ring118, as shown inFIG. 1. Once the energizing ring120is actuated downward and into the upper seal body116, the seal assembly100may be in an actuated configuration or an energized configuration. In the actuated configuration, the seal assembly100may form at least one seal able to withstand well pressure above and below the seal assembly100and lockdown the casing hanger101to the wellhead102.

For example, the energizing ring120may be actuated using a running and force tool to drive the energizing ring lower section122into the inner groove117. For example, the running and force tool may apply a downward force to an energizing ring setting surface123. A suitable running and force tool is of the type disclosed in U.S. Pat. No. 7,096,956, which is incorporated herein by reference in its entirety.

When the energizing ring120is so actuated, the lower section122may engage and press the inner lock ring118inward into the casing hanger101. The inner lock ring118may be forced into a recess within the casing hanger101and engage a hanger upstop119, which prevents upward movement of the inner lock ring118, which may prevent upward movement of the lower seal body114. Actuating the energizing ring120may further force the inner lock ring118into the hanger upstop119and prevent the inner lock ring118from disengaging the casing hanger101.

When actuated, the upper section121may engage and push the external ring106into the wellbore lockdown grooves127. The external ring106may engage the lockdown grooves127to limit upward and/or downward movement of the seal assembly100and casing hanger101. In certain embodiments, a gap between the walls of the lockdown grooves127and the external lock ring106may allow some vertical movement of the seal assembly100and casing hanger101relative to the wellhead102.

In other embodiments, the seal assembly100may be preloaded so that no vertical movement of the seal assembly100and casing hanger101is allowed relative to the wellhead102. Referring toFIG. 11, one such embodiment of the seal assembly100is shown engaging the casing hanger101and the wellhead102, while remaining in a non-actuated configuration.FIG. 12shows this seal assembly100in an actuated configuration or an energized configuration. When actuated, the energizing ring120may engage and push the external ring106into the wellbore lockdown grooves127. In this embodiment, the energizing ring120may have a tapered surface192that pushes outward against the external ring106when actuated. The external ring106may include two upper facing surfaces194designed to engage the corresponding upper tapered surfaces of the lockdown grooves127. Actuating the energizing ring120may preload the seal assembly100by forcing the upper facing surfaces194of the external ring106against the lockdown grooves127such that no vertical movement of the seal assembly100is allowed relative to the wellhead102. With this arrangement, the setting surface125and the load shoulder107may create a preloaded load path capable of supporting a load applied by a second casing hanger disposed in the wellhead102.

In certain embodiments, actuating the energizing ring120into the upper seal body116shears the one or more shear pins130as the energizing ring120moves into the inner groove117. In certain illustrative embodiments, the seal assembly100may comprise four shear pins, although any number of shear pins may be used without departing from the scope of the present disclosure. In certain embodiments, the one or more shear pins may be spaced radially apart from one another around the circumference of the upper seal body116. For example, where the seal assembly comprises four shear pins, each pin may be spaced 90° from adjacent shear pins.

The seal assembly100may comprise a plurality of dowel pins160, each press fit into the upper seal body116and extended through a corresponding radial slot in the external lock ring106. The dowel pins160may be structured and arranged to orient and retain the external lock ring106with the upper seal body116. In certain illustrative embodiments, the seal assembly100may comprise at least three dowel pins160, although any number of dowel pins may be used without departing from the scope of the present disclosure.

Once the energizing ring120is actuated into the upper seal body116, a notch on the energizing ring upper section121may move past and engage an overpull feature141disposed on the upper seal body116. The overpull feature141may prevent the energizing ring120from moving upward relative to the upper seal body116.

The upper seal body116may comprise an overhang portion184that overhangs and engages the load shoulder107. As such, the upper seal body116may transfer a downward load to the load shoulder107. For example, the upper seal body116may comprise a setting surface125. The setting surface125may engage a tool and the upper seal body116may transfer the load applied to the setting surface125onto the casing hanger101(e.g., via the load shoulder107).

Referring briefly toFIG. 10, an illustrative embodiment a system is shown comprising a plurality of seal assemblies100sealing and locking a plurality of casing hangers101,190to a wellhead102, according to certain aspects of the present disclosure. A second position casing hanger190may be positioned above a first casing hanger101and engage the load shoulder107of the first casing hanger101and the setting surface125of the seal assembly100. The load shoulder107and the setting surface125may define a shared load path. In a non-limited embodiment, a plurality of casing hangers101,190may be locked-down to the wellhead102using a plurality of seal assemblies100.

Referring back toFIG. 1, the energizing ring120may comprise a setting surface123, where a load applied to the setting surface123may be transferred to the upper seal body116and/or the inner lock ring118and, in turn, transferred to the casing hanger101. Thus, the load transferred to the casing hanger101may be split between one or more seal assembly setting surfaces123,125and the load shoulder107. In addition, applying a load across the setting surfaces123,125and the load shoulder107may increase hoop stiffness created by the upper seal body116and energizing ring120assembly.

For example, the setting surface125may be disposed on the upper seal body116between an inner neck and the inner most diameter of the upper seal body116. The setting surface125may comprise load transfer teeth180that complement a tool that engages the setting surface125(i.e., female load transfer teeth to engage male load transfer teeth disposed on a tool). For example, the setting surface125may comprise female load transfer teeth. The load shoulder107on the casing hanger101may also comprise complementary load transfer teeth182, for example, female load transfer teeth. In certain embodiments, the overhang portion184of the upper seal body116may comprise male load transfer teeth that are structured and arranged to land on and engage the load shoulder107. As such, the upper seal body116may cover and engage with a portion of the load shoulder107.

Referring toFIG. 7A, a seal assembly200is shown disposed between a wellhead202and a casing hanger201positioned within the wellhead202. The seal assembly200may comprise a lower seal body214, which is a unitary component positioned between the wellhead202and the casing hanger201. The lower seal body214may comprise a radially outward projecting member, protector element, and/or puller mechanism as described with respect toFIG. 1.

In certain embodiments, the lower seal body214may comprise at least one primary seal271and at least one secondary seal272. The primary seal271may comprise a metal to metal seal formed between the lower seal body214and the casing hanger201. In certain embodiments, one or more elastomer rings may be disposed on the lower seal body214and engage the casing hanger201. The at least one secondary seal272may be disposed on an upper portion of the lower seal body214relative to the primary seal271. The secondary seal272may be adjacent to an inner groove217disposed within the lower seal body214. For example, the secondary seal272may be disposed near a bottom of the inner groove217. In certain embodiments, the secondary seal272may comprise a metal to metal seal and/or one or more elastomer rings.

The seal assembly200may comprise an upper seal body216, which may comprise a unitary body. In certain embodiments, when the upper seal body216is in an actuated configuration, the seal assembly may be capable of maintaining a seal at extreme axial loads.

In certain embodiments, the upper seal body216may interlock with the lower seal body214. For example, a thread connection264may connect the lower seal body214to the upper seal body216. For example, the thread connection264may comprise complementary thread grooves located on the lower seal body214and the upper seal body216. The lower seal body214may interlock with a load ring218, for example using a thread connection267. The load ring218may provide structural integrity to the seal assembly200capable of inhibiting bending forces exerted on the seal assembly200. The load ring218may provide load transfer between the lower seal body214and an external lock ring206, supported by and engaging the load ring218. The load ring218may comprise an annular stop226for engagement with a lower portion of the external lock ring206. The annular stop226may be disposed on the outer diameter of the load ring218. The external lock ring206may comprise a single piece split ring, which may be run in a collapsed state and expanded into lockdown grooves227in the wellhead202, preventing upward movement of the casing hanger201and seal assembly200. In certain embodiments, the external lock ring206may interlock with the lockdown grooves227preventing the seal assembly200from moving upward with respect to the wellhead202.

The seal assembly200may comprise an energizing ring220extending within the upper seal body216, and engaging the external lock ring206. The energizing ring220may comprise a solid upper ring section221, which, when assembled with upper seal body216, may provide hoop strength to the seal assembly200that is capable of preventing inward collapse of the energizing ring220, external lock ring206, and/or the seal assembly200. The energizing ring220may comprise a solid lower nose222that may be inserted into an inner groove217of the upper seal body216. The energizing ring220may comprise a plurality of shear pins230. As described above, the plurality of shear pins230may connect the energizing ring220to the upper seal body216and prevent further insertion of the energizing ring220into the lower seal body214until the energizing ring220is actuated downward, at which time the shear pins230may be broken. The energizing ring220may also accept a plurality of dowel pins292for orienting the energizing ring220with respect to the seal assembly200, as described above.

Referring briefly toFIG. 7B, an isolated view of the energizing ring220is shown, according to certain embodiments. The lower nose222portion of the energizing ring220may be a solid ring. The energizing ring220is shown comprising a plurality of shear pin slots231. The energizing ring220may comprise a dowel pin slot293for accepting one of the plurality of dowel pins to orient the energizing ring220with respect to the seal assembly.

Referring toFIG. 8, the seal assembly200is shown in a non-actuated configuration, where the upper seal body216initially engages a load shoulder207of the casing hanger201. In the non-actuated configuration, the seal assembly200has yet to form the primary seal271or secondary seal272between the wellhead202and casing hanger201. The inner groove217may comprise a tapered region274, having a reduced diameter of less than the lower nose222of the energizing ring220. In the partially actuated configuration, the energizing ring220is not extended into the tapered region of the inner groove217.

Referring toFIG. 9, once the seal assembly200reaches the casing hanger201, the energizing ring220may be partially actuated into the inner groove217to form the primary seal271between the lower seal body214and the casing hanger201. For example, to partially actuate the energizing ring220a setting tool may deliver a load to the first setting surface225, which may force the lower seal body214into close engagement between the wellhead202and the casing hanger201without fully actuating the energizing ring220. In certain embodiments, the integrity of the primary seal271may be tested before the secondary seal272is engaged. In this partially actuated configuration, the energizing ring220may engage and push the external lock ring206into the wellbore lockdown grooves227. The external lock ring206may engage and interlock with the lockdown grooves227to limit upward movement of the seal assembly200.

Referring back toFIG. 7A, the energizing ring220may be fully actuated into the inner groove217, extending the nose222of the energizing ring220into the tapered region217. As such, the energizing ring220may apply outward pressure to walls of the inner groove217, which may be transferred to the wellhead202and the casing hanger201by the lower seal body214. The outward pressure by the lower seal body214against the wellhead202and the casing hanger201may create the secondary seal272.

Once the energizing ring220is actuated into the upper seal body216, a notch on the energizing ring220may move past and engage an overpull feature241disposed on the upper seal body216. The overpull feature241may prevent the energizing ring220from moving upward relative to the upper seal body216.

Accordingly, the seal assembly disclosed herein can be used to form a seal between a wellhead and a casing hanger effective to withstand axial loads exerted by well pressure conditions. As such, the seal assembly may maintain integrity of the seal under a wide range of downhole conditions. In addition, the seal assembly may provide multiple load surfaces for tool engagement while allowing sufficient flow-by area for the seal assembly to be run.

Although a limited number of seal rings are depicted herein, it would be appreciated by those of ordinary skill in the art that seal rings may be utilized at the interface of any two components that are coupled to one another as discussed above without departing from the scope of the present disclosure.

Therefore, the present disclosure is well adapted to attain the ends and advantages mentioned as well as those that are inherent therein. The particular embodiments disclosed above are illustrative only, as the present disclosure may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Even though the figures depict embodiments of the present disclosure in a particular orientation, it should be understood by those skilled in the art that embodiments of the present disclosure are well suited for use in a variety of orientations. Accordingly, it should be understood by those skilled in the art that the use of directional terms such as above, below, upper, lower, upward, downward and the like are used in relation to the illustrative embodiments as they are depicted in the figures, the upward direction being toward the top of the corresponding figure and the downward direction being toward the bottom of the corresponding figure.

Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular illustrative embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the present disclosure. Also, the terms in the claims have their plain, ordinary meaning unless otherwise explicitly and clearly defined by the patentee. The indefinite articles “a” or “an,” as used in the claims, are defined herein to mean one or more than one of the element that the particular article introduces; and subsequent use of the definite article “the” is not intended to negate that meaning.