External hydraulic tieback connector

A connector for tie back liners has a tubular housing having at least one interior locking dog window. A setting chamber having a setting piston is located in the housing. A retraction chamber is in the housing, spaced axially from the setting chamber and having a retracting piston. Locking dogs are movably coupled in the locking dog window and axially spaced between the setting chamber and the retraction chamber. An actuating sleeve has a cam surface in engagement with the locking dogs and end portions with the setting piston and the retracting piston. Linking elements are in engagement with the locking dogs and a load shoulder located in the housing. The linking elements extend through linking element windows in the actuating sleeve. A shock absorber on the end of the housing absorbs shock when the connector lands on a wellhead.

FIELD OF THE INVENTION

This invention relates in general to offshore drilling and well production equipment, and in particular to connectors for tieback external risers.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

In the drawings and description that follows, like parts are marked throughout the specification and drawings with the same reference numerals, respectively. The drawings are not necessarily to scale. Certain features of the invention may be shown exaggerated in scale or in somewhat schematic form and some details of conventional elements may not be shown in the interest of clarity and conciseness. The present invention is susceptible to embodiments of different forms. Specific embodiments are described in detail and are shown in the drawings, with the understanding that the present disclosure is to be considered an exemplification of the principles of the invention, and is not intended to limit the invention to that illustrated and described herein. It is to be fully recognized that the different teachings of the embodiments discussed below may be employed separately or in any suitable combination to produce desired results. The various characteristics mentioned above, as well as other features and characteristics described in more detail below, will be readily apparent to those skilled in the art upon reading the following detailed description of the embodiments, and by referring to the accompanying drawings.

Referring initially toFIG. 1, an exemplary embodiment of a tieback connector assembly100includes an outer tubular sleeve102that includes an inner flange102aat one end having a stepped internal shoulder102b, an annular internal recess102c, an annular internal recess102d, an annular recess102e, and an annular internal recess102fat another end. The sleeve102further defines a longitudinal flow passage102g, a longitudinal flow passage102h, a longitudinal flow passage102i, a radial flow passage102jthat connects the longitudinal flow passage102gto the internal annular recess102d, a radial flow passage102kthat connects the longitudinal flow passage102hto the internal annular recess102f, and a radial flow passage102lthat connects the longitudinal flow passage102ito a lower location within the internal annular recess102f.

A tubular actuating sleeve104is received within and mates with the annular internal recess102dof the outer tubular sleeve102that defines a tapered annular internal recess104aat one end, a plurality of circumferentially spaced apart radial windows104b, and a lower tubular end104c.

A tubular piston106that includes an annular external recess106aat one end is received within and mates with the internal annular recess102fof the outer tubular sleeve102. In an exemplary embodiment, the external annular recess106aof the tubular piston106mates with and in received within the internal annular recess102dof the outer tubular sleeve102and the upper end of the tubular piston106is threadably coupled to the lower tubular end104cof the actuating sleeve104.

A tubular piston108is received within and mates with the internal annular recess102fof the outer tubular sleeve102. The tubular piston108is also positioned proximate and below the tubular piston106.

An inner tubular sleeve110includes an internal flange110aat one end and an external tapered annular recess110bat another end. The end of the inner tubular sleeve110is received within and mates with the annular internal recess102cof the outer tubular sleeve102.

An inner tubular sleeve112includes an external annular recess112aat one end and an external flange112bhaving a bottom channel112cat another end. The bottom channel112cat the other end of the inner tubular sleeve112receives and mates with the other end of the inner tubular sleeve102.

The opposing ends of the inner tubular sleeves,110and112, are spaced apart from one another and thereby define an annular window114therebetween.

The internal annular recess102dof the external tubular sleeve102and the inner tubular sleeve110define therebetween an annular chamber116that receives one end of the tubular actuating sleeve104for longitudinal displacement therein. The internal annular recess102fof the external tubular sleeve102and the inner tubular sleeve112define therebetween an annular piston chamber118that receives the tubular pistons,106and108, for longitudinal displacement therein.

One side of a lower end120aof a pivotable load transfer element120is received within the internal annular recess102eof the external tubular sleeve102for pivoting motion relative to the external tubular sleeve. In an exemplary embodiment, a plurality of circumferentially spaced apart load transfer element elements120are received within the internal annular recess102eof the external tubular sleeve102for pivoting motion relative to the external tubular sleeve. The other side of the lower end120aof each load transfer element120is mounted for pivoting motion relative to the tubular actuating sleeve104. One side of an upper end120bof each load transfer element120is received within the internal annular recess102eof the external tubular sleeve102for radial displacement relative to the external tubular sleeve. The other side of the upper end120bof each load transfer element120extends through the corresponding circumferentially spaced apart radial window104bof the tubular actuating sleeve104for movement therein.

A lower end122aof a locking dog122includes a recessed curved surface that mates with an external curved surface of the upper end120bof the load transfer element120for pivoting motion relative thereto. In this manner, a plurality of circumferentially spaced apart locking dogs122are provided that are operably coupled to one or more corresponding load transfer elements120. In an exemplary embodiment, the load transfer elements120and the locking dogs122may be staggered with respect to one another in a circumferential direction. As a result, each locking dog122may be supported by and paired with circumferential opposing end portions of adjacent load transfer elements120.

The lower end122aof the locking dog122is also at least partially positioned within the corresponding circumferentially spaced apart radial window104bof the tubular actuating sleeve104for movement therein. An upper end122bof the locking dog122includes a tapered inner surface that mates with the tapered external annular recess110bof the inner tubular sleeve110and a tapered outer surface that mates with the tapered annular internal recess104aof the tubular actuating sleeve104. An inner face of the locking dog122includes a profiled outer surface.

A retraction sleeve124includes an internal annular recess124aat one end that mates with the external annular recess112aof the inner tubular sleeve112, an external annular recess124bat the one end that mates with and receives the other end of the tubular actuating sleeve104, a curved outer external surface124cthat mates with complementary curved surfaces provided on each of the load transfer elements120, and a tapered external surface124dat another end that mates with a portion of the lower ends122aof each of the locking dogs122for retaining and retracting the lower ends of the locking dogs.

An end of a telescoping tubular guide assembly126is coupled to the other end of the external tubular sleeve102that includes an inner telescoping tubular member126ahaving a tapered opening126aaat lower end thereof and an outer tubular support126bthat is coupled to the other end of the external tubular sleeve. In an exemplary embodiment, the inner telescoping tubular member126aof the tubular guide assembly126telescopes downwardly from the outer tubular support126bof the tubular guide assembly such that the inner telescoping tubular member of the tubular guide assembly may be displaced in a longitudinal direction relative to the outer tubular support of the tubular guide assembly and the other end of the external tubular sleeve102. In an exemplary embodiment, the inner telescoping tubular member126aof the tubular guide assembly126is coupled to the outer tubular support126bof the tubular guide assembly by one or more retaining bolts128and is spring biased away from the end of the inner telescoping tubular member of the tubular guide assembly by springs130positioned around each of the bolts.

Flow passages132are also defined within and extend through the outer tubular support126bof the tubular guide assembly126for conveying fluidic materials therethrough. In an exemplary embodiment, the flow passages132further include conventional orifices for controlling the rate of fluid flow therethrough.

In an exemplary embodiment, the telescoping support126bof the tubular guide assembly126may be provided as an outer annular extension of the lower end of the inner tubular sleeve112.

During operation, as illustrated inFIG. 1, an upper end of the assembly100is coupled to a lower end of a conventional tubular liner200that defines an internal passage200aand includes an external flange200bat the lower end having a stepped external flange200c. In particular, during assembly, the external flange200bof the lower end of the liner200is received within and is coupled to the internal flange102aof the external tubular sleeve102and the stepped external flange200cof the lower end of the liner200is received within and is coupled to the internal flange110aat the end of the inner tubular sleeve110. In this manner, the lower end of the liner200is coupled to the upper end of the assembly100is such a manner are to prevent longitudinal displacement of the liner relative to the assembly. In an exemplary embodiment, the liner200provides an external riser for connection to a subsea wellhead.

After coupling the assembly100to the lower end of the liner200, the assembly and liner are positioned proximate an end of a conventional wellhead300that defines an internal passage300aand includes an external profiled surface300bproximate the end of the wellhead and a tubular gasket300cwithin an annular recess provided at the upper end of the wellhead. In an exemplary embodiment, the assembly100and liner200are then displaced toward the end of the wellhead300until the end of the wellhead is received within the tapered opening122aof the tubular guide assembly122. In an exemplary embodiment, the wellhead300is a subsea wellhead.

In an exemplary embodiment, as illustrated inFIG. 2, the assembly100and liner200are then further displaced toward the end of the wellhead300until the tapered opening126aof the tubular guide assembly126engages load shoulders300dprovided on the wellhead. During the engagement of the tubular guide assembly126with the wellhead300, an annular chamber302is defined by, and bounded between, the exterior surface of the wellhead and the axial annular space defined between the lower end face of the inner tubular sleeve110, the upper end face of the inner telescoping tubular member126aof the tubular guide assembly126, and the inner surface of the outer tubular support126bof the tubular guide assembly.

In an exemplary, as illustrated inFIG. 3, after the tapered opening126aof the tubular guide assembly126engages the load shoulders300dprovided on the wellhead300, the assembly100and liner200are then further displaced toward the end of the wellhead300until the lower end face of liner rests on the upper end face of the end of the wellhead. As a result, the tubular gasket300cis compressed between the opposing open ends of the liner200and wellhead300thereby fluidicly sealing the interface therebetween. Furthermore, as a result of the further displacement of the assembly100and liner200, the springs130of the tubular guide assembly126are compressed thereby permitting the inner tubular telescoping portion126aof the tubular guide assembly126to telescope into and towards the outer tubular support portion126bof the tubular guide assembly. As a result, fluidic material within the chamber302is exhausted out of the chamber through the passages132. In an exemplary embodiment, the combination of the springs130, on the one hand, and the fluidic chamber302and passages132, on the other hand, provide a spring-damper shock absorber system that controllably absorbs energy and limits the rate of displacement of the inner tubular telescoping portion126arelative to the outer tubular support portion126bof the guide assembly126during the engagement of the guide assembly126with the wellhead300.

In an exemplary embodiment, the energy absorbed by the springs130, fluidic chamber302and passages132, during the further displacement of the assembly100and liner200minimizes shock loads on the assembly100, liner200and wellhead300. Furthermore, as a result, energy absorbed by the springs130, fluidic chamber302and passages132, during the further displacement of the assembly100and liner200prevents damage to the gasket300cthereby providing a soft landing of the end of the liner on the opposing end of the wellhead300. Furthermore, as a result of the further displacement of the assembly100and liner200, the locking dogs122of the assembly100are positioned in opposing relation to the profiled external surface300bof the wellhead300. Furthermore, as a result, energy absorbed by the springs130, fluidic chamber302and passages132, during the further displacement of the assembly100and liner200prevents distortion of the gasket300cthereby preventing, for example, flattening of the vertically aligned portion of the gasket into engagement with the tapered open ends of the passages,200aand300a, of the liner200and wellhead300, respectively.

The locking dogs122are then displaced into engagement with the profiled external surface300bof the wellhead300thereby locking the lower end of the liner200onto the opposing end of the wellhead. In particular, a pump400may be operated to pump fluid into and through the passages,102gand102j, thereby pressurizing the portion of the annular chamber116above the top end face of the tubular actuating sleeve104.

As a result of the pressurizing of the portion of the annular chamber116above the top end face of the tubular actuating sleeve104, the tubular actuating sleeve is displaced in a downward direction relative to the locking dogs122thereby impacting and displacing the locking dogs radially inwardly through the annular window114into engagement with the profiled external surface300bof the wellhead300. The downward displacement of the tubular actuating sleeve104further causes the inner surface of the tubular actuating sleeve to surround and engage the outer surface of the locking dogs122thereby preventing the locking dogs from being disengaged from the profiled external surface300bof the wellhead300. In an exemplary embodiment, during the downward displacement of the tubular actuating sleeve104, fluid is drained from the piston chamber118through the radial passages,102kand102l, into the longitudinal passages,102hand102i, respectively.

As illustrated inFIG. 3, during the operation of the assembly100to pivot and radially displace the locking dogs122into engagement with the profiled external surface300bof the wellhead300, the ends122aof the locking dogs are supported on the ends120bof the load transfer elements120. During the operation of the assembly100to pivot and radially displace the locking dogs122into engagement with the profiled external surface300b, the load transfer elements120provide pivoting links that swing in and out of the assembly. As a result, the load transfer elements120change the load angle between the assembly100and the locking dogs122while the locking dogs are displaced into engagement with the profiled external surface300bof the wellhead300. In an exemplary embodiment, the more the locking dogs122engage the profiled external surface300bof the wellhead300, the resistance to engagement in a radial direction also may increase. However, because the load angle between the assembly100and the locking dogs122, while the locking dogs are displaced into engagement with the profiled external surface300bof the wellhead300, increases within increasing engagement, the increased load angle provides increased inward radial force to assist the engagement of the locking dogs with the profiled external surface of the wellhead.

Referring now toFIG. 4, in an exemplary embodiment, the locking dogs122may be disengaged from the profiled external surface300bof the wellhead300by displacing the tubular actuating sleeve104upwardly relative to the locking dogs. In particular, the pump400may be operated to pump fluid into and through the passages,102iand102l, thereby pressurizing the portion of the annular chamber118below the tubular pistons,106and108. In an exemplary embodiment, during the pressurizing of the portion of the annular chamber118below the tubular pistons,106and108, fluid is drained from the portion of the annular chamber118above the tubular pistons,106and108, through passages,102mand102n, defined in the tubular sleeve102and fluid is drained from the annular chamber116through the passages,102gand102j.

As a result of the pressurizing of the portion of the annular chamber118below the tubular pistons,106and108, the pistons and the tubular actuating sleeve104are displaced in an upward direction relative to the locking dogs122thereby permitting the locking dogs to be displaced radially outwardly through the annular window114out of engagement with the profiled external surface300bof the wellhead300. The upward displacement of the tubular actuating sleeve104further causes the inner surface of the tubular actuating sleeve to no longer surround and engage the outer surface of the locking dogs122thereby permitting the locking dogs to be disengaged from the profiled external surface300bof the wellhead300.

Referring now toFIG. 5, in an exemplary embodiment, the locking dogs122may be disengaged from the profiled external surface300bof the wellhead300by displacing the tubular actuating sleeve104upwardly relative to the locking dogs. In particular, the pump400may be operated to pump fluid into and through the passages,102hand102k, thereby pressurizing the portion of the annular chamber118below the tubular piston106and above the tubular piston108. In an exemplary embodiment, during the pressurizing of the portion of the annular chamber118below the tubular piston106and above the tubular piston108, fluid is drained from the annular chamber116through the passages,102gand102j.

As a result of the pressurizing of the portion of the annular chamber118below the tubular piston106and above the tubular piston108, the tubular piston106and the tubular actuating sleeve104are displaced in an upward direction relative to the locking dogs122thereby permitting the locking dogs to be displaced radially outwardly through the annular window114out of engagement with the profiled external surface300bof the wellhead300. The upward displacement of the tubular actuating sleeve104further causes the inner surface of the tubular actuating sleeve to no longer surround and engage the outer surface of the locking dogs122thereby permitting the locking dogs from being disengaged from the profiled external surface300bof the wellhead300. In an exemplary embodiment, during the upward displacement of the tubular actuating sleeve104, fluid is drained from the piston chamber116through the passages,102gand102j.

In an exemplary embodiment, once the locking dogs122have been disengaged from the profiled external surface300bof the wellhead300, the assembly100and liner200may be displaced upwardly relative to the wellhead300.

As illustrated above inFIGS. 4 and 5, in an exemplary embodiment, during the upward displacement of the actuating sleeve104, the upper end of the actuating sleeve engages the external annular recess124bof the retraction sleeve124thereby displacing the retraction sleeve upwardly. As a result, the retraction sleeve124lifts and thereby displaces the locking dogs122into a retracted position out of engagement with the external profile300bof the wellhead300.

Referring initially toFIG. 6, an exemplary embodiment of a tieback connector assembly400includes an outer tubular sleeve or housing402that includes an inner flange402aat one end having a stepped internal shoulder402b, an annular internal recess402c, an annular internal recess402d, an annular internal recess402e, and an annular internal recess402fat another end.

A tubular actuating sleeve404, which is received within and mates with the annular internal recess402dof the outer tubular sleeve402defines a tapered annular internal recess or can surface404aon an inner side, a plurality of circumferentially spaced apart radial linking element windows404b, and a lower tubular end404cat another end. Actuating sleeve404is integrally joined to a setting piston404don its upper end.

A tubular retracting piston406that includes an annular external recess406aat one end is received within and mates with the internal annular recess402fof the outer tubular sleeve402. In an exemplary embodiment, the external annular recess406aof the tubular piston406mates with and is received within the internal annular recess402dof the outer tubular sleeve402and the upper end of the tubular piston406is threadably coupled to the lower tubular end404cof the tubular actuating sleeve404.

A tubular piston408is received within and mates with the internal annular recess402fof the outer tubular sleeve402. The tubular piston408is also positioned proximate and below the tubular piston406.

An inner tubular sleeve410includes an internal flange410aat one end and an external tapered annular recess410bat another end. The end of the inner tubular sleeve410is received within and mates with the annular internal recess402cof the outer tubular sleeve402.

An inner tubular sleeve412includes an external annular recess412aat an upper end and an external flange412bhaving flow passages412cand an internal annular recess412dat a lower end428. The upper side of external flange412bof the inner tubular sleeve412receives and mates with the lower end of the outer tubular sleeve402.

The opposing ends of the inner tubular sleeves,410and412, are spaced apart from one another and thereby define an annular locking dog window414therebetween.

The internal annular recess402dof the external tubular sleeve402and the inner tubular sleeve410define therebetween an annular setting piston chamber416that receives setting piston404dof the tubular actuating sleeve404for longitudinal displacement therein. The internal annular recess402fof the external tubular sleeve402and the inner tubular sleeve412define therebetween an annular piston chamber418that receives the tubular retracting pistons,406and408, for longitudinal displacement therein.

One side of a lower end420aof a load transfer element or linking element420is received within the internal annular recess402eof the external tubular sleeve402. In an exemplary embodiment, a plurality of circumferentially spaced apart load transfer element elements420are received within the internal annular recess402eof the external tubular sleeve402. One side of an upper end420bof each load transfer element420is received within the internal annular recess402eof the external tubular sleeve402. The other side of the upper end420bof each load transfer element420extends through the corresponding circumferentially spaced apart radial linking element window404bof the tubular actuating sleeve404.

A lower end422aof a locking dog422includes a surface that mates with an external surface of the upper end420bof the load transfer element420for sliding motion relative thereto. In this manner, a plurality of circumferentially spaced apart locking dogs422are provided that are paired with a corresponding load transfer element420. The lower end422aof the locking dog422is also at least partially positioned within the corresponding circumferentially spaced apart radial window404bof the tubular actuating sleeve404for movement therein. An upper end422bof the locking dog422includes a tapered inner surface that mates with the tapered external annular recess410bof the inner tubular sleeve410and a tapered outer surface that mates with the tapered annular internal recess404aof the tubular actuating sleeve404. An inner face of the locking dog422includes a profiled outer surface.

In an exemplary embodiment, the load transfer elements420and the locking dogs422may be staggered with respect to one another in a circumferential direction. As a result, each locking dog422may be supported by and paired with circumferential opposing end portions of adjacent load transfer elements420.

A retraction sleeve424includes an internal annular recess424aat one end that mates with the external annular recess412aof the inner tubular sleeve412, an external annular recess424bat the one end that mates with and receives the other end of the tubular actuating sleeve404, an outer external surface424cthat mates with complementary surfaces provided on each of the load transfer elements420, and a tapered external surface424dat another end that mates with a portion of the lower ends422aof each of the locking dogs422for retaining and retracting the lower ends of the locking dogs.

An end of a telescoping tubular guide assembly or shock absorber assembly426is coupled to the other end of the inner tubular sleeve412that includes an inner telescoping tubular member426awith a piston portion that mates with and is received within the internal annular recess412dof the inner tubular sleeve412and includes a tapered opening426bat a lower end thereof. The piston portion of tubular member426ahas annular inner seals426dand outer seals426c. Outer seals426cseal against inner sleeve recess412d. In an exemplary embodiment, the inner telescoping tubular member426aof the tubular guide assembly426telescopes downwardly from the inner tubular sleeve412such that the inner telescoping tubular member426aof the tubular guide assembly426may be displaced in a longitudinal direction relative to the inner tubular sleeve412. Similar to as shown inFIGS. 1-5, the inner telescoping tubular member426aof the tubular guide assembly426is coupled to the inner tubular sleeve412by one or more retaining bolts (not shown) and is spring biased away from the end of the inner tubular sleeve412by springs430positioned around each of the bolts.

Flow or displacement fluid passages412care also defined within and extend through the inner tubular sleeve412for conveying fluidic materials therethrough to inner annular recess412d. In an exemplary embodiment, the flow passages412cfurther include conventional orifices for controlling the rate of fluid flow therethrough.

In an exemplary embodiment, the design and operation of the tubular guide assembly426is substantially identical to the design and operation of the tubular guide assembly126illustrated and described above with reference toFIGS. 1-3.

During operation, as illustrated inFIG. 6, an upper end of the assembly400is coupled to a lower end of a conventional tubular liner500that defines an internal passage500aand includes an external flange500bat the lower end having a stepped external flange500c. In particular, during assembly, the external flange500bof the lower end of the liner500is received within and is coupled to the internal flange402aof the external tubular sleeve402and the stepped external flange500cof the lower end of the liner500is received within and is coupled to the internal flange410aat the end of the inner tubular sleeve410. In this manner, the lower end of the liner500is coupled to the upper end of the assembly400in such a manner as to prevent longitudinal displacement of the liner relative to the assembly. In an exemplary embodiment, the liner500provides an external riser for connection to a subsea wellhead.

As illustrated inFIG. 7, after coupling the assembly400to the lower end of the liner500, the assembly and liner are positioned proximate an end of a conventional wellhead600that defines an internal passage600aand includes an external profiled surface600bproximate the end of the wellhead. In an exemplary embodiment, the assembly400and liner500are then displaced toward the end of the wellhead600until the end of the wellhead is received within the tapered opening426bof the tubular guide assembly426. In an exemplary embodiment, the wellhead600is a subsea wellhead.

In an exemplary embodiment, as illustrated inFIG. 7, the assembly400and liner500are then further displaced toward the end of the wellhead600until the tapered opening426bof the tubular guide assembly426engages load shoulders600cprovided on the wellhead. During the engagement of the tubular guide assembly426with the wellhead600, an annular chamber602is defined by, and bounded between, the exterior surface of the wellhead and the axial annular space defined between the lower end face of the inner tubular sleeve412and the upper end face of the inner telescoping tubular member426aof the tubular guide assembly426.

In an exemplary embodiment, as illustrated inFIG. 7, after the tapered opening426bof the tubular guide assembly426engages load shoulders600cprovided on the wellhead600, the assembly400and liner500are then further displaced toward the end of the wellhead600until the lower end face of the liner rests on the upper end face of the end of the wellhead. As a result, a tubular gasket604is compressed between the opposing open ends of the liner500and wellhead600thereby sealing the interface therebetween. Furthermore, as a result of the further displacement of the assembly400and liner500, the springs430of the tubular guide assembly426are compressed thereby permitting the inner tubular telescoping portion426aof the tubular guide assembly426to telescope into and towards the inner tubular sleeve412. Inner seals426dseal against the exterior of wellhead600while outer seals426cseal against inner sleeve412in chamber602. As a result, sea water within the chamber602is exhausted out of the chamber through the passages428due to downward movement of inner sleeve412and outer sleeve402relative to telescoping guide member426. In an exemplary embodiment, the combination of the springs430, on the one hand, and the fluidic chamber602and passages428, on the other hand, provide a spring-damper shock absorber system that controllably absorbs energy and limits the rate of displacement of the inner tubular telescoping portion126arelative to the inner tubular sleeve412during the engagement of the guide assembly426with the wellhead600.

In an exemplary embodiment, the energy absorbed by the springs, fluidic chamber602and passages428, during the further displacement of the assembly400and liner500minimizes shock loads on the assembly400, liner500and wellhead600. Furthermore, as a result, energy absorbed by the springs, fluidic chamber602and passages428, during the further displacement of the assembly400and liner500prevents damage to the gasket604thereby providing a soft landing of the end of the liner on the opposing end of the wellhead600. Furthermore, as a result of the further displacement of the assembly400and liner500, the locking dogs422of the assembly400are positioned in opposing relation to the profiled external surface600bof the wellhead600. Furthermore, as a result, energy absorbed by the springs, fluidic chamber602and passages428, during the further displacement of the assembly400and liner500prevents distortion of the gasket604thereby preventing, for example, flattening of the vertically aligned portion of the gasket into engagement with the tapered open ends of the passages,500aand600a, of the liner500and wellhead600, respectively.

The locking dogs422are then displaced into engagement with the profiled external surface600bof the wellhead600thereby locking the lower end of the liner500onto the opposing end of the wellhead. In particular, a pump700may be operated to pump fluid into the annular chamber416thereby pressurizing the portion of the annular chamber416above the top end face of the tubular actuating sleeve404.

As a result of the pressurizing of the portion of the annular chamber416above the top end face of the tubular actuating sleeve404, the tubular actuating sleeve is displaced in a downward direction relative to the locking dogs422thereby impacting and displacing the locking dogs radially inwardly through the annular window414into engagement with the profiled external surface600bof the wellhead600. The downward displacement of the tubular actuating sleeve404further causes the inner surface of the tubular actuating sleeve to surround and engage the outer surface of the locking dogs422thereby preventing the locking dogs from being disengaged from the profiled external surface600bof the wellhead600. In an exemplary embodiment, during the downward displacement of the tubular actuating sleeve404, fluid is drained from the piston chamber418through radial passages and longitudinal passages (not shown).

As illustrated inFIG. 7, during the operation of the assembly400to radially displace the locking dogs422into engagement with the profiled external surface600bof the wellhead600, the ends422aof the locking dogs are supported on the ends420bof the load transfer elements420. In an exemplary embodiment, during the operation of the assembly400to radially displace the locking dogs422into engagement with the profiled external surface600b, the locking dogs slide on the exterior surfaces of the ends420bof the load transfer elements420into engagement with the profiled external surface600bof the wellhead600.

In an exemplary embodiment, the assembly400may be disengaged from the wellhead600by displacing the locking dogs422radially outward by displacing the tubular actuating sleeve404upwardly by pressurizing the annular chamber418using a pump. In this manner, one or both of the annular pistons,406and408, may be displaced upwardly into engagement with the lower end of the tubular actuating sleeve404thereby displacing the tubular actuating sleeve upwardly and displacing the locking dogs422radially outward and out of engagement with the wellhead600.

It is understood that variations may be made in the above without departing from the scope of the invention. Further, spatial references are for the purpose of illustration only and do not limit the specific orientation or location of the structure described above. While specific embodiments have been shown and described, modifications can be made by one skilled in the art without departing from the spirit or teaching of this invention. The embodiments as described are exemplary only and are not limiting. Many variations and modifications are possible and are within the scope of the invention. Accordingly, the scope of protection is not limited to the embodiments described, but is only limited by the claims that follow, the scope of which shall include all equivalents of the subject matter of the claims.