GB2381023A

GB2381023A - Adjustable hanger system

Info

Publication number: GB2381023A
Application number: GB0223979A
Authority: GB
Inventors: Blake T Deberry
Original assignee: Dril Quip Inc
Current assignee: Dril Quip Inc
Priority date: 2001-10-16
Filing date: 2002-10-15
Publication date: 2003-04-23
Anticipated expiration: 2022-10-15
Also published as: NO326233B1; GB0223979D0; NO20024949L; SG109993A1; GB2381023B; NO20024949D0

Abstract

An adjustable hanger system and related method connect a hanger to a wellhead, with a hanger supporting a tubular secured at its lower end in the well. The wellhead includes a housing (20) having a plurality of axially spaced support grooves (23, figure 1), and a hanger (30) including a support ring (32) radially moveable into a selected one of the support grooves on the wellhead housing. A lock down ring (34) may limit axially upward movement of the hanger with respect to the wellhead, while a support ring (32) may be used to limit axially downward movement of the hanger with respect to the wellhead housing. Both the support ring and the lock ring may be a substantially C-shaped rings which move radially outward into a selected one of the support grooves or locking grooves.

Description

Title of invention : "Improvements in or relating to an adjustable hanger system and a method of adjustably connecting a hanger to a wellhead" THE PRESENT INVENTION RELATES to an adjustable hanger system and a method of adjustably connecting a hanger to a wellhead.

The invention relates generally to the field of wellheads for use in the drilling and completion of sub-sea wells and more particularly the invention relates to an improved wellhead having an adjustable hanger system configured so that a tubular, such as a well casing or a liner, may be connected at its lower end to a mud line hanger, with the casing extending into the drill bore hole wherein the casing is tied back to a hanger adjustably supported within the surface wellhead. The invention also relates to a method of adjustably connecting a hanger to a wellhead, with the hanger suspending a tubular secured at its lower end in the well.

The present invention seeks to provide an improved adjustable hanger system for use in a wellhead for supporting a hanger.

According to one aspect of this invention there is provided an adjustable hanger system for connecting a hangar to a wellhead, with the hangar suspending a tubular secured at its lower end in the well, the hanger system comprising; the wellhead including a housing having a plurality of axially spaced support grooves ; and a hanger axially moveable relative to the support grooves, the hanger supporting a support ring which is radially moveable into a selected one of the plurality of support grooves in the wellhead housing to interconnect the hanger to the wellhead.

Preferably the support ring is initially carried in a retracted position within a recess in the hanger and is adapted to move radially outward into the selected one of the plurality of the support grooves.

Conveniently the support ring comprises three or more axially spaced circumferential ribs each for engagement with a selected one of the plurality of the support grooves.

Preferably the support ring is biased radially inward.

Conveniently the support ring is radially moved with a response to a fluid pressure responsive arrangement.

Preferably the fluid pressure responsive arrangement comprises a plurality of circumferentially spaced pistons.

Advantageously the support ring is adapted to move radially inwards in response to increased fluid pressure in an annulus surrounding the hanger.

Preferably an exterior stop surface is provided on the hanger to prevent the support ring from moving radially inward while in its selected support groove.

Conveniently the exterior stop surface is mounted to move axially with respect to the support ring to a locked position radially inward at a selected support groove.

Preferably the support ring is a substantially C-shaped unitary member.

The hangar system may further comprise a well head including a lock down groove separate from the plurality of support grooves and a lock down ring for securing the hanger to the well head by preventing axially upward movement of the hanger relative to the wellhead.

Conveniently each of the plurality of support grooves have a profile for receiving a support ring and the lock down groove has a profile for rejecting the support ring.

Preferably the selected one of the plurality of support grooves is positioned axially below the lock down groove.

Conveniently the lock down ring is initially carried in a retracted position within a recess in the hanger and is adapted to move radially outward into the lock down groove.

Preferably the lock down ring comprises two or more axially spaced circumferential ribs each adapted to move radially outward into the lock down groove.

Conveniently the lock down ring is biased radially inward.

Preferably the lock down ring is a substantially C-shaped unitary member.

Conveniently the wellhead housing includes a seal surface for sealing with a sealing mechanism acting between the hanger and the wellhead.

The hangar may further comprise a plurality of substantially cylindrical sealing surfaces on the wellhead housing, each of the sealing surfaces being spaced between an upper and a lower one of a plurality of support grooves for sealing engagement with the sealing mechanism.

The hangar system may further comprise at least one lock down groove spaced above the plurality of support grooves; and a sealing surface on the wellhead housing between the at least one lock down groove and a support groove having an axial spacing substantially equal to an axially spacing of a sealing surface between an upper and a lower support groove. Consequently in one embodiment the axial spacing between the lock down groove and the uppermost support groove is substantially equal to an axial spacing between any support groove and the next lower support groove.

The hangar system may further comprise the wellhead including a lock down groove separate from the plurality of support grooves; and a lock down ring for securing the hanger to the wellhead by preventing axially upward movement of the hanger relative to the wellhead.

Preferably a shoulder on the hanger is dimensioned to land on the supporting ring to prevent axially downward movement of the hanger and the tubular with respect to the supporting ring fixed to the wellhead housing.

Conveniently the lower end of the tubular is secured to the well by a mud liner hanger.

Preferably a bore in a wellhead housing includes a radially enlarged upper portion for receiving a tubular hanger.

Conveniently the wellhead housing includes an upper shoulder for supporting the tubing hanger above the hanger secured to the wellhead by the support ring.

The hangar system may further comprise a blow out preventer above the wellhead, the blow out preventer having a bore diameter substantially equal to the bore diameter of an upper portion of the wellhead housing.

The invention also relates to a method of adjustably connecting a hanger to a wellhead, the hanger suspending a tubular secured at its lower end in the well, the method comprising providing a wellhead housing having a plurality of axially spaced support grooves; providing a hanger including a radially moveable support ring ; lifting the hanger and the support ring above a selected one of the plurality of support grooves ; and thereafter lowering the hanger such that the supporting ring moves radially outward into a selected one of the plurality of support grooves, thereby preventing axially downward movement of the hanger with respect to the wellhead.

Preferably the method further comprises increasing fluid pressure in the well to move the support ring radially outward into the selected one of the plurality of support grooves.

The method may further comprise lowering the hanger axially to move a stop surface on the hanger radially inward of the radially expanded support ring, thereby preventing the support ring from moving out of the selected one of the plurality of support grooves.

Conveniently the method further comprises lowering at least a portion of the hanger below the plurality of support grooves; thereafter moving the hanger upward to provide a desired tension in the tubular; and thereafter locking the support ring to the selected one of the plurality of support grooves.

Preferably the method further comprises landing a tubing hanger on a shoulder of the housing to support the tubing hanger in the well.

The method may further comprise increasing pressure in the well to axially move a sleeve, thereby exposing ports to fluid pressure to move the support ring to its expanded position into the selected one of the plurality of support grooves.

The method may further comprise shearing a pin supporting the sleeve, such that upon shearing the pin the sleeve moves to open the ports.

Conveniently the method further comprises providing a plurality of fluid pressure responsive pistons for moving the support ring to its expanded position into the selected one of the plurality of support grooves.

Preferably the method further comprises providing a lock down ring on the hanger; providing at least one lock down groove on the wellhead housing; and positioning the lock down ring in the lock down groove to lock the tubing hanger to the wellhead, the lock down ring preventing axially upward movement of the hanger with respect to the wellhead.

Conveniently the method further comprises providing a plurality of sealing surfaces on the wellhead housing each sealing surface being spaced between a respective upper and lower support groove.

The method may further comprise lowering a seal element on a running tool into the well after the support ring has expanded outward into the selected support groove; and axially moving the seal element relative to the hanger and the wellhead to set the seal between the hanger and the wellhead.

Preferably the seal element is run in the well with a lock down ring actuator for moving the lock down ring into the lock down groove.

The method may further comprise utilising a clutch-type running tool to run the tubular into the well and secure the lower end of the tubular into the well.

Conveniently the method further comprises slacking off on a running string to lower the support ring into the selected one of the plurality of the grooves.

The method may further comprise securing a lower end of the tubular string in the well by a mud liner hanger.

The method may further comprise providing a running tool having a first set of splines allowing axial manipulation with secured rotation between a running string and the tubular to secure the lower end of the tubular in the well, and providing a second set of splines on the running tool allowing axial manipulation and secured rotation between the running string and the hanger for disconnecting the running tool from the hanger after the support ring has moved into the select one of the plurality of support grooves.

A preferred hanger system is such that a tubular, such as a casing or liner, may be supported on the wellhead and may be selectively positioned with respect to the wellhead so that the operator may apply a proper tension to the string.

In a preferred embodiment a wellhead is provided with a plurality of axially spaced landing or support grooves which are used for securing the tubuler hanger to the wellhead. A support ring on the casing hanger may be moved radially outward for engagement with one of the grooves in response to increased fluid pressure. Lowering of the tubular hangar on the wellhead then prevents the support ring from moving radially inward and reliably supports the casing hanger from the wellhead. Lock ring when engaged in one of the lock grooves prevents the tubular hanger from moving axially upward relative to the wellhead.

The wellhead enables the hanger, such as the casing hanger, to be landed and sealed with the casing head, with a desired tension in the casing by allowing substantial variations in the space-out length and thus the desired stretch of the casing supported on the casing hanger secured to the wellhead. More particularly, the hanger may pass below the landing or support grooves and below a lockout groove as discussed below, then the hanger pulled upward to

put tension on the tubular string. When at or slightly above a desired tubular tension, the hanger may then be reliably secured to the wellhead.

In order that the invention may be more readily understood, and so that further features thereof may be appreciated, the invention will now be described, by way of example, with reference to the accompanying drawings in which: FIGURE 1 is a side view of one embodiment of a wellhead having a hanger system according to the present invention prior to receiving a production casing thereon ; FIGURE 2 illustrates the wellhead as shown in Figure 1, with a casing hanger suspended within the wellhead from a drill pipe and production casing extending downward to the mud line for interconnection with the tie back at the upper end of a subsurface casing hanger; FIGURE 3 similarly illustrates the casing hanger with a selected tension applied to the production casing by the operator, and subsequent to dropping a ball to actuate the piston to bias a support ring outward, FIGURE 4 similarly illustrates the casing hanger after the operator has slacked off slightly so that the hanger moves downwards to lock the support ring to the wellhead housing, FIGURE 5 similarly illustrates downward movement of the work string to allow unthreading of running tool components from the casing hanger, and

FIGURE 6 similarly illustrates the removal of the running tool and the subsequent insertion of a tool to engage a lockdown ring with the wellhead housing, and to seal the casing hanger to the wellhead.

Figure 1 illustrates a surface wellhead housing 20 at the upper end of an outer casing 21 extending downward to a subsurface wellhead (not shown). The housing bore 22 has a plurality of axially spaced support grooves 23 each adapted to receive a support ring of a casing hanger, as will be described and one or more lockdown grooves 23 or 24 above the support groove for optionally receiving a lockdown ring on the hanger. The support grooves are preferably equally spaced from one another, and the lockdown groove (s) 23 or 24 are preferably spaced axially the same distance above the uppermost support grooves, thereby forming cylindrical seal surfaces 25 of substantially equal height between adjacent grooves. The housing 20 has an enlarged bore 26 above bore 22 to receive a tubing hanger to be lowered into the housing for landing on a shoulder 27. Conventional load sensors may be used to provide an output for the operator to indicate the weight of casing "hung off'from the wellhead housing 20.

As illustrated, each of the support grooves 23 has three annular groove segments, 23A, 23B, 23C, each extending radially outwardly from the bore.

The topmost lockdown groove 24 has only two groove segments 24A and 24B, thus permitting it to receive only the lockdown ring on the tubing hanger, and not a support ring. Depending on the level at which the hanger is to be supported, the lockdown ring may be received in one of the axially spaced support grooves other than the lowermost support groove, as discussed below.

As shown in Figure 2, a casing hanger 30, from which the production casing 31 is suspended, carries the support ring 32 in a recess 33, and carries a lockdown ring 34 about a reduced diameter portion 35. The support ring has three ribs each for engaging one of the three segments of a selected support groove 23, and the lockdown ring 34 has two ribs for locking either within the lockdown groove 24 above the support grooves, or within one of the support grooves above the support groove which receives the support ring 32.

As will be described below, an annular seal mechanism may be lowered onto the landed casing hanger for sealably engaging the seal surface both beneath and above the lockdown ring so as to close the annulus between the casing hanger and the bore of the wellhead housing.

As shown in Figures 2 and 3, the casing hanger 30 is lowered on a running tool 40 by drill pipe or other work string 41 through a blowout preventer or BOP 42, which is connected above the wellhead housing 20. The BOP preferably has a bore aligned with and sized with bore 26. As shown in Figure 3. the drill pipe 41 has been raised to pull a desired tension In the production casing 31 which raises the support ring 32 and the lockdown ring 34 to a desired elevation with respect to the wellhead 20 for imparting tension to the casing. The normally retracted support ring 32 is then in a position axially in line with a sealing surface 25 and between a pair of the

support grooves, e. g., between the second and third lowermost support grooves as shown in Figure 3. Since both the support ring 32 and the lockdown ring 34 are normally retracted, they do not engage either the lockdown or the support grooves during this raising of the casing hanger.

Once the hanger 30 is positioned above the groove 23 in which the support ring 32 is to be engaged, one or more circumferentially spaced pistons 48 are urged outwardly to urge the support ring to an outer position for engaging the Intended support groove 32. To energize the pistons 48, a ball 49 may be dropped through the drill pipe 51 to land on the seat 46, as shown In Figure 3. The increase in fluid pressure within the running tool 40 thus shears the pin 43 which holds the sleeve 45 in its upper position, as shown in Figure 2. and causes the inner sleeve 45 to move to the position as shown in Figure 3, so that ports 50 in the body 44 are open to fluid pressure within the drill pipe 41, and transmit pressure through the fluid passageways 52 to each of the pistons 48. A series of ports in sleeve 45 allow communication with passageways 52 in a casing hanger 32 to act on pistons 48. The pistons 48 are thus biased radially outward by fluid pressure applied to the radially interior end of each piston. While maintaining the increased fluid pressure within the drill pipe, the operator may slack off slightly so that the support ring 32, which is biased out by the pistons, snaps into the next lower groove 23. The casing hanger may then continue to be lowered until a shoulder 55 lands on the upper end of the outwardly disposed support ring 32. Once the support ring 32 is positioned as shown in Figure 4, the exterior cylindrical stop surface 56 on the casing hanger prevents the support ring 32 from moving radially inward, and casing weight is reliably hung off from the wellhead housing with the desired tension in the production casing as determined by the operator From a review of Figures 1 - 3, those skilled in the art will appreciate that the operator may pull upward on a casing string to briefly exert the tension in the

casing string slightly above the level desired, so that when the operator slacks off and the ring 32 snaps within the annular recess 23 below that position, the casing string will have the desired stretch.

In many applications, three or more support grooves are provided, with each support groove being spaced axially from other support grooves by a

cylindrical sealing surface 25. For many applications, adjacent support n cor grooves will be spaced axially (three inches) or more apart, since the operator

can accommodate a final position of the casing hanger relative to the wellhead housing within a spacing of several inches or more.

Both the support ring 32 and a lockdown ring 34 are preferably split or C-shaped rings, with an outer surface configured for mating with corresponding grooves in the wellhead housing 20. Various mating configurations between the C-rings and the grooves in the wellhead housing are thus possible.

As shown in Figures 3, 4, and 5, the running tool 40 comprises an upper tubular body 60 threaded to the lower end of the drill pipe 41. A clutchtype running tool as disclosed in U. S. Patent 5, 226,493 allows the production casing or the tubular to be manipulated so that it may be connected at its lower end to a mud liner hanger, or otherwise secured, e. g. , by an anchor, within the well. Outer sleeve 68 may move axially with respect to inner body 44, which in turn carries an inner sleeve 45 with the landing seat 46. When the running tool 40 is positioned as shown in Figure 4, the splines on the lower sleeve 61 of body 60 engage corresponding splines 62, so that the inner body 44 as well as the casing hanger 30 and the casing supported therefrom may be rotated to make up at the level of the mud line. Rotation of the casing string 31 also may be used to close off ports in the mud liner hanger. After the mud line connection is made up and the support ring 32 has moved to the position as shown in Figure 4. the operator may set weight down on the drill

pipe 41 to disengage the splines 62 and engage the lower splines 63 on the body 44, as shown in Figure 5. When in the position as shown in Figure 5, torque may then be applied to the drill pipe to unthread the running tool 40 from the threads 64 at the upper end of the casing hanger 30, so that the drill pipe may be raised for removing the running tool 40 from within the wellhead housing.

Once the running tool has been removed, a seal element and locking tool 70 as shown in Figure 6 may be run in the wellhead at the lower end of work tubular 72. The tool 70 includes a conventional J-lock mechanism 74 for carrying seal element 76 into the bore in the wellhead housing. The lower end of the seal element 76 includes a nose 78 which presses the lockdown ring 34 radially outward into either the lockdown ring groove 24 or into the support ring groove above the groove occupied by the support ring 32. The sealing element 76 preferably includes at least two axially spaced elastomeric and metal rib sealing bodies 80 and 82 which are connected by a common seal element base. The seal bodies 80 and 82 are spaced above and below one of the grooves, so that each seal body 80 and 82 forms a reliable seal with the inner cylindrical surface 25 of the wellhead housing. By manipulation of the tool 70, the body of the tool may be released from the seal element with the Jlock mechanism, and the tool 70 then pulled out of the wellhead 20 It should be noted that the gate valve 84 as shown in Figure 6 will conventionally be positioned below the seal element 76, and allows communication to the annulus between the production casing 31 and the outer casing 21. The production casing 31 may typically connect to a mud line tie back connector on a casing hanger, while the outer casing 21 typically connects to a subsea housing. Also, it should be appreciated that the port of the wellhead body in communication with the gate valve 41 is shown at the same elevation as in one of the support grooves 23. This does not decrease

the reliability of these components to perform their desired function, since the grooves are preferably provided circumferentially around the full bore of the wellhead body, and the C-shaped support ring 32 and the lockdown ring 34 have sufficient strength to perform their desired functions even if the annular groove is briefly interrupted by a port. The support ring 32 may thus prevent casing from moving downward with respect to the wellhead housing 20 and thus supports the production casing 31. The lockdown ring 32 prevents any

upward movement of the casing with respect to housing 20. which may occur , if there were a pressure surge.

The seal element 76 is thus moved axially into position for performing its function after the casing hanger 30 has been supported in a selected one of the various possible vertical positions with respect to the wellhead. Once the seal element 76 is positioned as shown in Figure 6, the seal element is a static seal which preferably seals with two of the cylindrical surfaces 25 (see Figure 1) between the support grooves or lockdown groove. By interspersing the seal above and below these groove profiles, the length required for the wellhead stack up Is reduced. Locking groove 24 is configured differently than groove 23 to insure that the support ring 32 cannot snap into the groove 24, since then no groove would be provided for a lock ring 34. Regardless of which axially spaced groove the operator decides to engage with the support ring 32. the lockdown ring 34 is spaced above the support ring and fits within the next upper groove 23 or 24 above the groove 23 which receives the support ring 32.

t The described wellhead thus provides a high degree of flexibility to adjust the casing hanger relative to the wellhead, thereby allowing for a desired stretch in the casing. This increased flexibility is a significant feature since the support

surfaces and the lockdown surfaces on the wellhead may be provided radially

inward of the central bore)

in the wellhead. The casing hanger may thus be lowered below and, if desired, a substantial distance below, the support surfaces. When in its desired position, the casing hanger and the casing secured thereto may be pulled upward into the bore of the wellhead and, when a desired tension is obtained in the casing, the hanger may then be supported on the support surfaces of the wellhead, as discussed above. If the casing hanger is not at a desired position relative to the wellhead when desired tension is applied in the casing string, the operator need not hang off the casing string from the wellhead, but instead may elect to reposition the casing hanger at either a higher or lower position relative to the casing string such that. when the casing hanger is subsequently raised to its desired position within the wellhead, the desired tension will be applied to the casing string and the hanger may thus be hung off from the wellhead assembly with the desired tension in the string.

The operator may thus apply tension to the casing hanger to cause the casing to stretch, then increase fluid pressure within the work string by dropping a ball, so that when the operator slacks off slightly, the support ring snaps into the next lowest groove. The application of fluid pressure through the work string along with the downward motion of the casing hanger activates the support ring to support the casing string from the wellhead. A lockdown ring subsequently insures that the casing string cannot move upward relative to the wellhead. A support groove may also serve as a lockdown groove.

The seal surfaces are preferably spaced between the grooves to minimize the stack up height of the wellhead assembly.

The wellhead as shown in the enclosed drawings is a"two step" wellhead with a lower bore 22 for receiving a casing hanger, and an upper bore 26 for receiving a tubing hanger. The present invention may be used in a wellhead which only supports a casing hanger, and a separate upper

wellhead may support the tubing hangar, or tubing may not yet be provided within the well.

While hydraulic fluid pressure is preferably used for biasing the pistons and thus the support ring radially outward, other techniques may be used for biasing a support ring in the radially outward position so that, once the support ring engages its intended groove in the wellhead hosuing, the hnager may be lowered to efectively lock the support ring in its radially outward position, thereby supporting the hanger and the tubular supported on the hanger from the wellhead housing. Also, while a C-shaped support ring and lock ring are preferred to obtain high reliability with very little vertical spacing, other mechanisms maybe used for interconnecting the hanger and the housing in a selected axial position once the desired stretch in the tubular has been obtained.

A significant feature of this invention is the ability of the hanger to pass through the wellhead unhindered to allow the tie back to the subsea structure.

The techniques described above are particularly well suited for obtaining the desired stretch in a casing string fixed to a subsea wallhead near the mud line.

The described wellhead has an interior surface adapted to lock with the casing string at one of a selected plurality of elevations. Various types of oilified tubulars, including a production casing or a riser may be supported from the hangar secured to the wellhead by the techniques disclosed herein.

A wellhead and hanger have been described wherein the tubular my be continuous between the member which fixes the lower end of the tubular in a well, such as the tie back tool at the mud line, and the hangar at the upper end of the tubular string, without the use of sliding seals used in prior art systems.

As described above a primary and a backup seal may be interspersed above and below one of the grooves on the wellhead to minimize the stack up length required in the wellhead, while still providing the necessary adjustments to obtain the desired stretch of the tubular string. Also some of the grooves may serve as either a support groove or a lock-out groove.

The casing hangar may be run into the wellhead using a clutch type running tool.

It will be understood by those skilled in the art that the embodiment shown and described is exemplary and various other modifications may be made in the practice of the invention.

In the present specification"comprises"means"includes or consists of and "comprising"means"including or consisting of.

The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

1. An adjustable hanger system for connecting a hangar to a wellhead, with the hangar suspending a tubular secured at its lower end in the well, the hanger system comprising ; the wellhead including a housing having a plurality of axially spaced support grooves; and a hanger axially moveable relative to the support grooves, the hanger supporting a support ring which is radially moveable into a selected one of the plurality of support grooves in the wellhead housing to interconnect the hanger to the wellhead.

2. An adjustable hanger system as defined in claim 1 wherein the support ring is initially carried in a retracted position within a recess in the hanger and is adapted to move radially outward into the selected one of the plurality of the support grooves.

3. An adjustable hanger system according to claim 1 or claim 2 wherein the support ring comprises three or more axially spaced circumferential ribs each for engagement with a selected one of the plurality of the support grooves.

4. An adjustable hanger system according to any one of the preceding claims wherein the support ring is biased radially inward.

5. An adjustable hanger system according to any one of the preceding claims wherein the support ring is radially moved with a response to a fluid pressure responsive arrangement.

6. An adjustable hanger system according to claim 5 wherein the fluid pressure responsive arrangement comprises a plurality of circumferentially spaced pistons.

7. An adjustable hanger system according to any one of the preceding claims wherein the support ring is adapted to move radially inwards in response to increased fluid pressure in an annulus surrounding the hanger.

8. An adjustable hanger system according to any one of the preceding claims wherein an exterior stop surface is provided on the hanger to prevent the support ring from moving radially inward while in its selected support groove.

9. An adjustable hanger system according to claim 8 wherein the exterior stop surface is mounted to move axially with respect to the support ring to a locked position radially inward at a selected support groove.

10. An adjustable hanger system according to any one of the preceding claims wherein the support ring is a substantially C-shaped unitary member.

11. An adjustable hanger system according to any one of the preceding claims further comprising a well head including a lock down groove separate from the plurality of support grooves and a lock down ring for securing the hanger to the well head by preventing axially upward movement of the hanger relative to the wellhead.

12. An adjustable hanger system according to claim 11 wherein each of the plurality of support grooves have a profile for receiving a support ring and the lock down groove has a profile for rejecting the support ring.

13. An adjustable hanger system according to claim 11 or 12 wherein the selected one of the plurality of support grooves is positioned axially below the lock down groove.

14. An adjustable hanger system according to any one of claims 11 to 13 wherein the lock down ring is initially carried in a retracted position within a recess in the hanger and is adapted to move radially outward into the lock down groove.

15. An adjustable hanger system according to any one of claims 11 to 14 wherein the lock down ring comprises two or more axially spaced circumferential ribs each adapted to move radially outward into the lock down groove.

16. An adjustable hanger system according to any one of claims 11 to 15 wherein the lock down ring is biased radially inward.

17. An adjustable hanger system as defined in any one of claims 11 to 16 wherein the lock down ring is a substantially C-shaped unitary member.

18. An adjustable hanger system as defined in any one of the preceding claims wherein the wellhead housing includes a seal surface for sealing with a sealing mechanism acting between the hanger and the wellhead.

19. An adjustable hanger system as defined in claims 18, further comprising: a plurality of substantially cylindrical sealing surfaes on the wellhead housing, each of the sealing surfaces being spaced between an upper and a lower one of

a plurality of support grooves for sealing engagement with the sealing mechanism.

20. An adjustable hanger system as defined in claims 18 or 19, further comprising: at least one lock down groove spaced above the plurality of support grooves; and a sealing surface on the wellhead housing between the at least one lock down groove and a support groove having an axial spacing substantially equal to an axially spacing of a sealing surface between an upper and a lower support groove.

21. An adjustable hanger system as defined in claims 18 or 19, further comprising : the wellhead including a lock down groove separate from the plurality of support grooves ; and a lock down ring for securing the hanger to the wellhead by preventing axially upward movement of the hanger relative to the wellhead.

22. An adjustable hanger system as defined in any one of the preceding claims wherein a shoulder on the hanger is dimensioned to land on the supporting ring to prevent axially downward movement of the hanger and the tubular with respect to the supporting ring fixed to the wellhead housing.

23. An adjustable hanger system as defined in any one of the preceding claims wherein the lower end of the tubular is secured to the well by a mud liner hanger.

24. An adjustable hanger system as defined in any one of the preceding claims, wherein a bore in a wellhead housing includes a radially enlarged upper portion for receiving a tubular hanger.

25. An adjustable hanger system as defined in claim 24, wherein the wellhead housing includes an upper shoulder for supporting the tubing hanger above the hanger secured to the wellhead by the support ring.

26. An adjustable hanger system as defined in any one of the preceding claims further comprising: a blow out preventer above the wellhead, the blow out preventer having a bore diameter substantially equal to the bore diameter of an upper portion of the wellhead housing.

27. A method of adjustably connecting a hanger to a wellhead, the hanger suspending a tubular secured at its lower end in the well, the method comprising : providing a wellhead housing having a plurality of axially spaced support grooves; providing a hanger including a radially moveable support ring; lifting the hanger and the support ring above a selected one of the plurality of support grooves; and thereafter lowering the hanger such that the supporting ring moves radially outward into a selected one of the plurality of support grooves, thereby preventing axially downward movement of the hanger with respect to the wellhead.

28. A method as defined in claim 27, further comprising increasing fluid pressure in the well to move the support ring radially outward into the selected one of the plurality of support grooves.

29. A method as defined in claim 27 or 28 further comprising lowering the hanger axially to move a stop surface on the hanger radially inward of the radially expanded support ring, thereby preventing the support ring from moving out of the selected one of the plurality of support grooves.

30. A method as defined in any one of claims 27 to 29 further comprising: lowering at least a portion of the hanger below the plurality of support grooves; thereafter moving the hanger upward to provide a desired tension in the tubular; and thereafter locking the support ring to the selected one of the plurality of support grooves.

31. A method as defined in any one of claims 27 to 30 further comprising landing a tubing hanger on a shoulder of the housing to support the tubing hanger in the well.

32. A method as defined in any one of claims 27 to 31 further comprising increasing pressure in the well to axially move a sleeve, thereby exposing ports to fluid pressure to move the support ring to its expanded position into the selected one of the plurality of support grooves.

33. A method as defined in claim 32 further comprising shearing a pin supporting the sleeve, such that upon shearing the pin the sleeve moves to open the ports.

34. A method as defined in any one of claims 27 to 33 further comprising: providing a plurality'of fluid pressure responsive pistons for moving the support ring to its expanded position into the selected one of the plurality of support grooves.

35. A method as defined in any one of claims 27 to 34 further comprising providing a lock down ring on the hanger; providing at least one lock down groove on the wellhead housing; and positioning the lock down ring in the lock down groove to lock the tubing hanger to the wellhead, the lock down ring preventing axially upward movement of the hanger with respect to the wellhead.

36. A method as defined in any one of claims 27 to 35 further comprising providing a plurality of sealing surfaces on the wellhead housing each sealing surface being spaced between a respective upper and lower support groove.

37. A method as defined in any one of claims 27 to 36 further comprising lowering a seal element on a running tool into the well after the support ring has expanded outward into the selected support groove ; and axially moving the

seal element relative to the hanger and the wellhead to set the seal between the hanger and the wellhead.

38. A method as defined in claim 37, wherein the seal element is run in the well with a lock down ring actuator for moving the lock down ring into the lock down groove.

39. A method as defined in any one of claims 27 to 38 further comprising i utilising a clutch-type running tool to run the tubular into the well and secure the lower end of the tubular into the well.

40. A method as defined in any one of claims 27 to 39, further comprising: slacking off on a running string to lower the support ring into the selected one of the plurality of the grooves.

41. A method as defined in any one of claims 27 to 40 further comprising securing a lower end of the tubular string in the well by a mud liner hanger.

42. A method as defined in claim 41 further comprising providing a running tool having a first set of splines allowing axial manipulation with secured rotation between a running string and the tubular to secure the lower end of the tubular in the well, and providing a second set of splines on the running tool allowing axial manipulation and secured rotation between the running string and the hanger

for disconnecting the running tool from the hanger after the support ring has moved into the select one of the plurality of support grooves.

43. An adjustable hanger system substantially as herein described with reference to and as shown in the accompanying drawings.

44. A method of adjustably connecting a hanger to a wellhead substantially as herein described with reference to the accompanying drawings.

45. Any novel feature or combination of features disclosed herein.