Abstract:
An adjustable hanger system secures a hanger to a wellhead such that a downward extending tubular may be tensioned at a selected level. The wellhead includes a housing having a plurality of axially spaced grooves, with selected grooves receiving a support member therein. The wellhead housing also has an axially elongate and generally cylindrical sealing surface spaced above the plurality of grooves for sealing engagement with a seal element. The hanger is axially movable relative to the plurality of grooves. The hanger is supported by the support member which is radially movable into selected ones of a plurality of grooves. A lockdown member may also move into selected ones of the plurality of grooves for preventing axially upward movement of the hanger relative to the wellhead.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to an adjustable hanger system for connecting a hanger to a wellhead. More particularly, the adjustable hanger system is used for tensioning a tubular extending downward from the hanger and secured at a lower end in the well. 
       BACKGROUND OF THE INVENTION 
       [0002]    Various types of hanger systems have been devised for tensioning a tubular in a well. Many prior art adjustable hanger systems include numerous components within the wellhead housing which are adjusted to achieve tensioning of the tubular. U.S. Pat. No. 5,176,218 discloses a threaded sleeve which is landed inside the wellhead. The sleeve interfaces with the hanger by rotating the hanger relative to the sleeve. U.S. Pat. Nos. 5,671,812, 5,255,746 and 5,944,111 utilize various arrangements of an internal load shoulder and a hanger with multiple grooves to achieve adjustability. 
         [0003]    U.S. Pat. No. 6,065,542 discloses another design wherein adjustment for tensioning is achieved within the hanger. U.S. Pat. No. 8,066,764 discloses another technique for making adjustments to the hanger to tension the tubular in the well. 
         [0004]    U.S. Pat. No. 7,040,412 discloses an adjustable hanger system wherein a series of axially spaced groove sets are provided in the wellhead, with the hanger including a support ring and a lockdown ring each for fitting within one of the sets of axially spaced grooves. The sealing surface between groove sets provides a sealing surface on the wellhead for sealing with the hanger. 
         [0005]    Prior art adjustable hanger systems tend to be complicated, which in turn leads to questionable reliability. The system discloses U.S. Pat. No. 7,040,412 is reliable since the hanger is connected directly to in the wellhead. When a selected set of grooves for connection with the hanger create too much or too little tension in the string, the hanger may be axially raised or lowered so that another vertically spaced set of grooves will provide the more appropriate tension desired for the hanger system. This design is particularly intended for very deep wells, and fine adjustment of the hanger relative to grooves in the wellhead is not disclosed. 
         [0006]    The disadvantages of the prior art are overcome by the present invention, an improved adjustable hanger system and method are hereinafter disclosed. 
       SUMMARY OF THE INVENTION 
       [0007]    In one embodiment, an adjustable hanger system is connected to a wellhead such that a tubular extending downward from the hanger and secured at a lower end of the well may be tensioned at a selected level. The hanger system includes a wellhead housing with a plurality of axially spaced grooves, with each groove having a profile to receive a support member therein. The support member may be carried in the well on the hanger. The wellhead housing includes an axially elongated and generally cylindrical sealing surface spaced above the plurality of axially spaced grooves for sealing engagement with a seal element between the wellhead housing and the hanger. The hanger is axially movable relative to the plurality of grooves, and the support member is axially movable into selected ones of a plurality of grooves in the wellhead housing to axially connect the hanger to the wellhead. 
         [0008]    According to the method of the invention, the wellhead housing is provided with a plurality of axially spaced grooves to accept the support member, and includes a generally cylindrical sealing surface spaced axially above the plurality of grooves. The support member is positioned in the well on the hanger above selected ones of a plurality of grooves. When the hanger is lowered slightly in the well, the support member moves radially outward into the selected ones of the plurality of grooves, thereby preventing axially downward movement of the hanger with respect to the wellhead. A seal is sealed between the hanger and a generally cylindrical sealing surface while the support member is within selected ones of the plurality of grooves. 
         [0009]    These and further features and advantages of the present invention will become apparent from the following detailed description, wherein reference is made to the figures in the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIGS. 1A and 1B  are cross-sectional half views of a wellhead housing, with a hanger connected to the housing at the lower end of the axially spaced grooves in the wellhead housing shown in  FIG. 1A , and at the upper end of the axially spaced grooves in the wellhead housing shown in  FIG. 1B . 
           [0011]      FIG. 2  is a detailed cross-sectional view including a support ring and a lockdown ring each out of mating engagement with the grooves in the wellhead housing. 
           [0012]      FIG. 3  is a detailed cross-sectional view illustrating the lockdown ring out of mating engagement with the wellhead grooves, and the landing or support ring in mating engagement with the wellhead grooves. 
           [0013]      FIG. 4  is a cross-sectional view of a top portion of the hanger and a seal lower sleeve between the wellhead and the hanger, and a portion of mandrel radially within the hanger. 
           [0014]      FIGS. 5A and 5B  are cross-sectional half views of a running tool for moving the support ring into mating engagement with the grooves in the wellhead housing. In  FIG. 5B , the hanger is not yet engaged with the housing groove, and in  FIG. 5B  the hanger is engaged with the housing grooves. 
           [0015]      FIGS. 6A and 6B  are cross-sectional half views of a running tool for setting the seal to seal between the wellhead and the hanger, and for moving the lockdown ring into mating engagement within the grooves in the wellhead housing.  FIG. 6A  shows the seal installation starting, and  FIG. 6B  shows the seal installed. 
           [0016]      FIG. 7  is a detailed cross-sectional view showing the support ring in mating engagement with the grooves in the housing, while the lockdown ring is out of engagement with the grooves in the wellhead housing. 
           [0017]      FIG. 8  illustrates both the lockdown ring and the support ring in engagement with the grooves in the wellhead housing. 
           [0018]      FIG. 9  illustrates the seal installed between the hanger and the wellhead housing. 
           [0019]      FIGS. 10A and 10B  are cross-sectional views of the lower seal sleeve setting the lockdown ring in  FIG. 10A  engaging the lower threads on the housing, and the lockdown ring in  FIG. 10B  engaging the upper threads on the housing. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0020]    The hanger system disclosed herein provides an axial elongate sealing surface on the interior of the wellhead housing above an axially spaced plurality of grooves on the wellhead housing. Regardless of the position of the hanger with respect to the grooves, a seal will seal between the hanger and the cylindrical sealing surface above the plurality of grooves, and the hanger will be axially secured to the wellhead housing to provide the desired tension in the tubular string supported in the well from the hanger. 
         [0021]    The hanger system allows for very fine adjustment of the position of the hanger relative to the wellhead, thereby obtaining fine adjustment of the tension applied to the tubular extending downward from the hanger. For many applications, the axially spacing of the grooves will be one-quarter inch or less. Because the grooves have the same groove profile and axial spacing, the support ring and the lockdown ring will fit within any of the selected grooves, which is contrary to disclosure with U.S. Pat. No. 7,040,412, in which the support ring had a different profile than the lockdown ring, so that each ring fit within its corresponding groove profile. 
         [0022]      FIGS. 1A and 1B  disclose a portion of the surface wellhead assembly including a casing head or wellhead housing  10  and a generally tubular shaped hanger  12 . One should appreciate that  FIG. 1A  illustrates the hanger in a lower position within the wellhead housing, and  FIG. 1B  depicts the same hanger in an upper position within the wellhead housing. The tubular  14  supported on the hanger extends downwardly from the hanger, and is conventionally secured in the well at or near its lower end. A spacer spool  16  is shown connected to the wellhead housing  10  with a plurality of conventional dogs  17 . A series of axially extending grooves  18  are provided on the inner surface in the housing  10 . Both the support ring  22  and a lockdown ring  24  discussed subsequently may be moved into engagement with selected ones of the plurality of grooves  18 , thereby securing the hanger to the wellhead. Seal  82  may optionally be provided so that the sealed chamber may be tested. One or more conventional gate valves  25  are provided for communication between the annulus about the tubular  14  and the interior of the housing  10 . 
         [0023]      FIG. 2  illustrates a portion of the wellhead  10  and the casing hanger  12 , and more clearly illustrates the grooves  18  on the wellhead for receiving both the support ring  22  and the lockdown ring  24 . A fluid passageway  26  is provided in the hanger for supplying pressurized fluid to one or more circumferentially spaced pistons  28 , which move radially outward as shown in  FIG. 3  for mating engagement of the support ring with the grooves on the wellhead housing. During radial outward movement of the support ring, the lockdown ring  24  remains in its position out of mating engagement with the grooves  18 . Each of the support ring  22  and the lockdown ring  24  may be biased radially inward to its natural or relaxed position. 
         [0024]      FIG. 4  illustrates the lower sleeve  30  of the seal assembly discussed subsequently inserted between the cylindrical sealing surface  20  on the wellhead housing and the radially outward surface on the hanger  12 . A portion of the running tool  40  used to set to the seal may be sealed to the hanger  12  by one or more seals  42 , while seal  44  seals between the lower sleeve  30  and the hanger  12 . 
         [0025]    Referring now to  FIGS. 5A and 5B , a running tool  50  may be used to activate the support ring, and is shown in  FIG. 5A  in its run in position, wherein the support ring  22  is not yet activated. A ball  52  may be dropped on seat  54 , thereby increasing the pressure above the ball, which increases pressure in the axially extending passageway  26 . With the increase in pressure, the ball  52  may move down with the seat  44  and the sleeve. High fluid pressure will then force the pistons as shown in  FIGS. 2 and 3  to move the support ring  22  radially outward so that its teeth engage the grooves  18  in the wellhead to prohibit downward movement of the tubular string supported on the hanger, as shown in  FIG. 5B . The support ring  22  may be retained in its radially outward position by support surface  32  on the hanger (see  FIG. 7 ) engaging radially inward surface  34  on the support ring  22  to prevent the support ring from moving radially inward. 
         [0026]      FIGS. 6A and 6B  illustrate a running tool  60  for running the seal assembly  62  in place, and also for moving the backup ring  24  radially outward. Fluid pressure below the closed BOP above the spacer spool  16  may thus move the tool  60  and the seal ring  62  supported thereon from its upper position as shown in  FIG. 6A  to its lower position as shown in  FIG. 6B . As shown in  FIG. 9 , the seal  62  may be positioned on the running tool  60  for reliably sealing between the housing  10  and the hanger  12 . As shown in  FIGS. 7 and 8 , the lower sleeve  30  attached to seal  62  moves downward with the seal  62  during the seal setting operation, and becomes trapped between the radially outer surface  64  on the hanger  12  and the radially inner surface  66  on the lockdown ring  24 , thereby forcing the lockdown sleeve  24  radially outward into engagement with the grooves in the casing hanger, as shown in  FIG. 8 .  FIGS. 10A and 10B  illustrate the sleeve  30  in an upper position to actuate the lockdown ring for engaging an upper set of grooves  18  in  FIG. 10A , and in a lower position in  FIG. 10B  to actuate the lockdown ring to engage a lower set of grooves  18 . 
         [0027]    The operational sequence for tension a tubular is described below. The riser (or other tubular) is lowered in the well on a running tool and is connected at its lower end to an external tieback connector (not shown). Pressure tests are commonly made by pressurizing the riser through the running tool, and the running tool is then removed. 
         [0028]    The hanger passes through the drilling spool and weight is set down onto the inner riser tieback. The riser is rotated to the right and torqued to approximately 5000 foot pounds. The riser is then pulled to obtain the desired riser tension. While holding tension on the riser, a ball is dropped through the drill pipe which lands in a lower sleeve in the clutch tool. Pressure is applied through the drill pipe which moves the shuttle sleeve downward, allowing pressure to communicate with the radial pistons located in the riser hanger to drive the support ring radially outward. While holding pressure in the drill pipe, the inner riser is slowly lowered by the support ring until the ring snaps into the first set of circumferential grooves located in the housing and the riser load is then transferred to the riser hanger. The pressure in the drill pipe may be released, and approximately 5000 pounds set down on the clutch tool. The clutch tool is then rotated to the left which releases the clutch tool from the inner riser hanger, allowing the tool to be brought back to the surface. 
         [0029]    Following installation to the hanger, the riser hanger seal is made up to the seal with the installation running tool. The tool is lowered into the housing while metal seal has landed on the outside of the hanger. The piston seal is formed on the ID of the hanger with the seal running tool. The BOP rams are closed around the drill pipe and the annulus above the hanger is pressurized, which drives the running tool and the seal assembly down onto the inner riser hanger. Pressure in the annulus is then released and the drill pipe is torqued to approximately 5000 foot pounds to lock the metal seal onto the hanger. An external test port adjacent the metal seal may be removed and a hydrostatic test performed to verify pressure integrity of the metal seal to the hanger and the drilling spool. Upon completion of the pressure test, the tool may then be picked up and brought back to the surface. 
         [0030]    For the embodiments shown in  FIGS. 1-6 , the support member received within the grooves in the wellhead housing is C-shaped support ring member. Similarly, the lockdown member is another C-shaped ring member. In other embodiments, one or both of the support member and the lockdown member may have a configuration other than being C-shaped, and for example, may comprise circumferentially spaced dogs which move radially into and out of engagement with the grooves in the wellhead housing. These dogs may be biased radially inward, or may be moved radially by various types of dog actuation mechanisms. 
         [0031]    Although specific embodiments of the invention have been described herein in some detail, this has been done solely for the purposes of explaining the various aspects of the invention, and is not intended to limit the scope of the invention as defined in the claims which follow. Those skilled in the art will understand that the embodiment shown and described is exemplary, and various other substitutions, alterations and modifications, including but not limited to those design alternatives specifically discussed herein, may be made in the practice of the invention without departing from its scope.