Patent Publication Number: US-7900706-B2

Title: Shoulder ring set on casing hanger trip

Description:
RELATED APPLICATIONS 
     This non-provisional application is continuation-in-part patent application that claims the benefit of co-pending, non-provisional patent application U.S. Ser. No. 11/189,387, now U.S. Pat. No. 7,150,323, filed on Jul. 26, 2005, which claimed priority to provisional application 60/591,067 filed Jul. 26, 2004, both of which are hereby incorporated by reference in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates in general to subsea wellhead assemblies, and in particular to a full bore wellhead housing, wherein the operator sets a casing hanger load shoulder ring during the casing hanger running procedure. 
     2. Background of the Invention 
     A typical subsea well has a wellhead housing at the upper end of the well. The wellhead housing is a tubular member having a bore. A string of large diameter casing attaches to the lower end of the wellhead housing and extends into the well. After further drilling through the wellhead housing, a smaller diameter string of casing is installed. A casing hanger at the upper end of the smaller diameter string of casing lands in the bore on a load shoulder. 
     In one type of wellhead housing, the load shoulder is permanently formed in the bore during manufacturing. This permanent load shoulder reduces the diameter of the bore below the load shoulder. In some instances, a full diameter is desired for the entire length of the bore. It has been proposed to install a split load ring in the bore before running the first casing hanger to provide a load shoulder. However, running the load ring on a running tool would require an extra trip from the drilling rig to the sea floor. In very deep water, the extra trip would be expensive. 
     In another technique, a split load ring is secured in a contracted diameter position to the casing hanger. When the casing hanger enters the bore, the load ring moves to a set position on a support shoulder provided in the bore. 
     SUMMARY OF THE INVENTION 
     In this invention, a support shoulder is located in the wellhead housing. The support shoulder has an inner diameter equal or greater than the full bore of the wellhead housing and is located at the lower end of a recess. A split, resilient load ring is carried in an expanded diameter initial position in the recess above the support shoulder. The load ring is movable downwardly in the recess to a set position in engagement with the support shoulder. When moving downward, the load ring contracts to a smaller diameter. 
     An actuator is carried in the bore above the load ring for moving the load ring from the initial position to the set position. The casing hanger is provided with a profile that engages the actuator while being lowered into the wellhead housing. Continued downward movement of the casing hanger causes the actuator to move the load ring to the set position. The casing hanger lands on the load ring as it moves to the set position. 
     A wellhead assembly has a wellhead housing with a bore containing a support shoulder. A split, resilient load ring carried in an expanded initial position in the bore above the support shoulder. The load ring is movable downwardly to a contracted set position in engagement with the support shoulder. An actuator assembly is carried in the bore above the load ring for pushing the load ring from the initial position to the set position. The actuator assembly has an axially resilient portion. A casing hanger is for securing to a string of casing and lowering into the wellhead housing. The casing hanger has an outer profile that engages the actuator assembly as the casing hanger moves downwardly in the bore, thereby causing the resilient portion to compress and the load ring to move to the set position. The casing hanger has an outer profile that engages the actuator assembly as the casing hanger moves downwardly in the bore, also causing the casing hanger to land on the load ring so that the load ring transfers weight from the casing hanger to the wellhead housing. 
     The resilient portion can have a serpentine cross-section. The resilient portion can have an initial axial length prior to the casing hanger engaging the actuator assembly that is greater than a compressed axial length of the resilient portion after being compressed by the downward movement of the casing hanger. The resilient portion can have a decompressed axial length upon removal of the casing hanger from the wellhead housing that is substantially the same as an initial axial length. 
     The load ring can have an engagement shoulder on an upper side, and at least a portion of the engagement shoulder has a larger diameter than an interior surface of the resilient portion to the casing hanger engaging the actuator assembly. The load ring can have an engagement shoulder on an upper side, and an interior surface of the resilient portion has a larger diameter than the engagement shoulder when the load ring is in the set position. 
     The actuator assembly can have an axially resilient ring and an actuator ring. The axially resilient ring can be positioned between the actuator ring and the load ring. The actuator ring can have an inner profile that engages the outer profile of the casing hanger. The actuator assembly can have an inner profile that engages the outer profile of the casing hanger and the axially resilient ring is positioned between the inner profile and the load ring. 
     A wellhead assembly has a wellhead housing with a bore that has an axis and a support shoulder. A ramp surface extends upward and outward from the support shoulder. The wellhead housing has a recess extending upward from the ramp. A split, resilient load ring is carried in an initial position in the recess. The load ring is movable downwardly on the ramp surface to a set position on the support shoulder. The load ring has an engagement shoulder on an upper side. An axially resilient ring is carried on the load ring. The wellhead assembly also has a casing hanger for securing to a string of casing and lowering into the wellhead housing. An outer profile on the casing hanger compresses the resilient ring as the casing hanger moves downwardly in the bore, thereby causing the resilient ring to move downward and push the load ring to the set position. And thereby casing hanger lands on the engagement shoulder of the load ring. 
     The load ring can have an inner diameter while in the initial position that is greater than an interior surface of the axially resilient ring while in the initial position. The axially resilient ring can be carried within the recess while the load ring is in the initial position. The axially resilient ring can have an initial axial length when the load ring is in the initial position that is greater than a compressed axial length of the spacer ring when the load ring is in the set position. 
     At least a portion of the engagement shoulder can have a larger inner diameter than an interior surface of the axially resilient ring when the load ring is in the initial position. The interior surface of the axially resilient ring can have a larger inner diameter than the engagement shoulder when the load ring is in the set position. 
     An actuator ring can be carried on the axially resilient ring. The actuator ring can be engaged by the casing hanger to compress the axially resilient ring. An interior surface of the actuator ring can be radially inward of the axially resilient ring. The actuator ring can be carried within the recess while the load ring is in the initial position, and at least a portion of the actuator ring can be carried within the recess while the load ring is in the set position. 
     A method for installing a casing hanger in a subsea wellhead housing having a bore includes providing a support shoulder in the bore of the wellhead housing. The method also includes the step of mounting a split, resilient load ring in an expanded initial position in the bore above the support shoulder. Then the method includes the step, mounting an actuator assembly having an axially resilient portion in the bore above the load ring. Then the method includes the step, lowering the wellhead housing into the sea and installing the wellhead housing at the upper end of a well. Then the method includes the step, securing a string of casing to a casing hanger and lowering the casing hanger into the wellhead housing. Finally, the method includes the step, compressing the axially resilient portion of the actuator assembly with the casing hanger and pushing the load ring downward, thereby causing the load ring to contract and land on the support shoulder and the casing hanger to land on the load ring. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a vertical sectional view of a portion of a wellhead housing having a shoulder ring assembly located in a retracted position. 
         FIG. 2  is a sectional view of the portion of the wellhead housing of  FIG. 1 , and further showing a casing hanger in the process of engaging an actuator ring of the shoulder ring assembly. 
         FIG. 3  is a sectional view of the portion of the wellhead housing of  FIG. 1 , showing the casing hanger moving the actuator ring and the load shoulder ring downward. 
         FIG. 4  is a sectional view of the portion of the wellhead housing of  FIG. 1 , showing the casing hanger and load shoulder ring in a fully landed position. 
         FIG. 5  is an enlarged sectional view of part of the actuator assembly after the casing hanger has fully landed. 
         FIG. 6  is a vertical sectional view of an alternative portion of a wellhead housing having a shoulder ring assembly located in a retracted position, and further showing a casing hanger in the process of engaging an actuator ring of the shoulder ring assembly. 
         FIG. 7  is a sectional view of the portion of the wellhead housing of  FIG. 6 , showing the casing hanger and load shoulder ring in a fully landed position. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to  FIG. 1 , wellhead housing  11  is a large tubular member that is typically located at the upper end of a well in a subsea location near the sea floor. Wellhead housing  11  has a bore  13  extending through it with an internally threaded profile  15 . Bore  13  has a minimum inner diameter portion  13   a  and an enlarged diameter portion or recess  13   b  extending below. 
     A support ring  17  has external threads  19  that secure to threads  15  within wellhead housing bore portion  13   b . Support ring  17  is a solid cylindrical member that is stationarily mounted to wellhead housing  11  prior to lowering wellhead housing  11  into the sea. Support ring  17  has an upward facing support shoulder  23 , a ramp  20  above support shoulder  23 , and a neck  21  extending upward from ramp  20 . Neck  21  has a larger inner diameter than the smallest inner diameter bore portion  13   a . A retainer ring  24  secures to a threaded profile formed in bore portion  13   b  below support ring  17 . Retainer ring  24  retains support ring  17  in engagement with threaded profile  15 . Support shoulder  23  has an inner diameter that is equal or greater than the inner diameter of portion bore  13   a.    
     A split load ring  25  initially mounts to neck  21  by a shear pin  27 . Shear pin  27  releasably retains load ring  25  in an initial diameter expanded position. Split load ring  25  is carried on the inner diameter of neck  21  initially in an upper position, as shown in  FIGS. 1 and 2 . Split load ring  25  is biased outward, and is movable from the upper position down ramp  20  to a set position on support shoulder  23 , as shown in  FIG. 4 . In the lower position, load ring  25  is located farther inward than while in the upper retracted position. Split load ring  25  has an upward and inward facing engagement shoulder  26 . The inner diameter of load ring  25  is equal or greater than the inner diameter of bore portion  13   a  while in the initial position, and less than bore portion  13   a  while in the set position. 
     Load ring  25  has a protruding band  28  on its outer diameter for snapping into engagement with a groove  32  formed on support ring  17  above support shoulder  23 . Band  28  and groove  32  releasably fasten load ring  25  to support ring  17  when load ring  25  moves to its set position. 
     An actuator ring  29  is carried within recessed bore portion  13   b  for movement between an upper position shown in  FIG. 1  and a lower position shown in  FIG. 4 . Actuator ring  29  is a rigid cylindrical member that has a lower end  31  in contact with an upper side of load ring  25 . In the example shown, an outer diameter portion of actuator ring  29  at lower end  31  is spaced inward a selected distance from the sidewall of bore portion  13   b . Actuator ring  29  and load ring  25  are also mounted in bore portion  13   b  prior to lowering wellhead housing  11  into the sea. Actuator ring  29  has an annular recess  33  formed within its inner diameter. 
     A latch ring  35  is movably carried within recess  33 . Latch ring  35  is a split ring that is inward biased. Latch ring  35  has an outer diameter  37  that is spaced radially inward from the cylindrical base of recess  33 . Latch ring  35  has a profile  39  formed on its inner diameter that comprises a selected pattern of grooves and lands. In the initial position, profile  39  protrudes inward a short distance past the inner diameter of actuator ring  29 . Also, the inner diameter of profile  39  is slightly less than the inner diameter of bore portion  13   a.    
     Referring to  FIG. 5 , latch ring  35  has an upward protruding rim  41  located on its inner diameter  37 . Upper rim  41  locates on the outer side of a downward protruding lip  43  of a retainer cap  45 . Latch ring  35  has a downward protruding lower rim  47  on its lower end at its outer diameter  37 . Lower rim  47  locates radially outward from an upward protruding lower lip  49 , which is formed in recess  33 . Lips  43  and  49  and rims  41  and  47  retain latch ring  35  within recess  33 , but allow radial movement. Lower rim  47  is sufficiently thin so as to buckle or crush under the weight of casing, as will be subsequently explained. Retainer cap  45  is secured to an upper portion of actuator ring  29 , such as by threads. 
     When the operator wishes to run casing, the operator secures a casing hanger  53 , shown in  FIG. 2 , to the casing and lowers it through a riser (not shown) and into the well. Casing hanger  53  has a bore  55  and an external profile  57 . Profile  57  comprises a plurality of grooves and lands that match profile  39  of latch ring  35 . Because of the protrusion of latch ring  35 , when profile  57  aligns with profile  39 , latch ring  35  will snap into engagement with casing hanger  53 , as shown in  FIG. 2 . Casing hanger  53  has a downward facing shoulder  59  that is at an angle for mating with engagement shoulder  26  on the upper surface of load ring  25 . When load ring  25  lands on support shoulder  23 , as shown in  FIG. 4 , casing hanger shoulder  59  will be in mating abutment with engagement shoulder  26  of load ring  25 . Band  28  on load ring  25  will snap into engagement with groove  32 , preventing upward movement of load ring  25 . 
     Casing hanger  53  may have a protruding rib or band  61  formed on its outer diameter below load shoulder  59  for providing a feedback to determine that band  28  on load ring  25  has latched into the groove  32  of support ring  17 . After load ring  25  has locked into groove  32 , the operator can lift casing hanger  53  a short distance to test whether the engagement was properly made. While lifting, rib  61  will contact load ring  25  and exert an upward force. The operator can exert an overpull above the weight of the casing string to an amount less than what would be required to completely pull load ring  25  from support shoulder  23 . 
     Casing hanger  53  has a plurality of flow passages  63  (only one shown) that are illustrated in  FIG. 3 , but for clarity, are not shown in the other views. Flow passages  63  extend from a lower shoulder  65  upward to the vicinity of profile  57 . Each flow passage  63  joins a channel  67  that extends along the outer diameter of casing  53 . Flow passages  63  and channels  67  serve for returning flow during cementing. 
     In operation, the components shown in  FIG. 1  will be assembled at the factory, at a field site or on a drilling rig, prior to lowering wellhead housing  11  into the sea. Preferably, the operator installs a wear bushing or protective sleeve over support ring  17  and actuator ring  29 . Wellhead housing  11  is installed in a conventional manner, typically within an outer wellhead (not shown) that is secured to conductor pipe extending into an upper portion of the well. Wellhead housing  11  will be secured to a string of large diameter casing and lowered into the well to a selected depth. The operator connects wellhead housing  11  to a drilling riser and blowout preventer and continues drilling through wellhead housing  11  to the desired depth. 
     After the drilling has been completed, the operator removes the wear bushing, preferably on the last trip of the drill bit. The operator then lowers a string of casing on casing hanger  53 . As casing hanger  53  aligns with actuator ring  29 , its profile  57  will engage profile  39  of latch ring  35 . 
     Continued downward movement causes shear pin  27  to shear as shown in  FIG. 3 . Load ring  25  slides down ramp  20  and inward to the set position of  FIG. 4 , where it latches into place on support shoulder  23 . Casing hanger shoulder  59  will abut load ring  25 . Lower rim  47  ( FIG. 5 ) will crush or buckle under the weight imposed by casing hanger  53 . This deformation causes the weight of the string of casing to bypass latch ring  35  and actuator ring  29  and pass directly from casing hanger  53  through shoulder  59 , load ring  25 , support ring  17  and into wellhead housing  11 . The operator cements the casing in a conventional manner. 
     The invention has significant advantages. While in the initial position, the load ring provides full bore access during initial drilling operations. When needed, the load ring is moved to the set position, providing a load shoulder smaller than the diameter of the bore of the housing above the load ring. The movement to the set position occurs automatically when the casing hanger is being installed. An additional trip to move the load ring to the set position is not required. 
     Referring to  FIGS. 6 and 7 , an alternative embodiment  69  is shown for an actuation assembly that actuates or pushes split load ring  25  downward from its initial position shown in  FIG. 6 , to its set position shown in  FIG. 7  when casing hanger  53  is lowered into wellhead housing  11 . Actuation assembly  69  preferably comprises an actuator ring  29 ′ and an axial resilient portion  30 ′. As shown in  FIGS. 6 and 7 , axial resilient portion  30 ′ can be an axially resilient ring. The ring forming axial resilient portion  30 ′ in  FIGS. 6 and 7  preferably comprises a serpentine-shaped cross-section. As will be readily appreciated by those skilled in the art, an axially resilient portion such as a serpentine-shaped cross section could also be integrally formed in an actuator ring so that actuation assembly  69  comprises only one ring rather than two separate rings  29 ′,  30 ′. 
     Load ring  25  preferably has an inner diameter that is larger than the inner diameters of actuator ring  29 ′ and axially resilient portion  30 ′. A profile  39 ′ is formed on an inner surface of actuator assembly  29 ′ for engagement with a profile  57 ′ of casing hanger  53  when casing hanger  53  is lowered into wellhead housing  11 . Profile  39 ′ is located above axially above axially resilient portion  30 ′. In the preferred embodiment, profile  39 ′ is formed on the interior surface of actuator ring  29 ′ so that casing hanger  53  engages actuator ring  29 ′, which in turn pushes downward on axially resilient portion  30 ′ as casing hanger  53  continues moving downward into wellhead housing  11 . 
     Resilient portion  30 ′ compresses and pushes load ring  25  axially downward from its initial position, thereby shearing pin  27  so that load ring can contract radially inward and move axially downward along ramp  20  to upward facing support shoulder  23 . Upon landing on support shoulder  23 , as shown in  FIG. 7 , load ring  25  is in its contracted, set position. Resilient portion  30 ′ compresses so that casing hanger load shoulder  59  lands directly on engagement shoulder  26  of load ring  25 . The compression of resilient portion  30 ′ allows the weight from casing hanger  53  and any string supported therefrom to be transferred directly from casing hanger load shoulder  59  to engagement shoulder  26 , rather than through actuator assembly  69 . Therefore, the weight associated with casing hanger  53  and the string of casing supported therefrom, is transferred straight through load ring  25  to support ring  17  and wellhead housing  11 . Upon removal of casing hanger  53 , axially resilient portion  30 ′ extends to its original length and can be used again. 
     While the invention has been shown in only one of its forms, it should be apparent to those skilled in the art that it is not so limited but is susceptible to various changes without departing form the scope of the invention.