Adjustable Riser Suspension System

Abstract

A riser suspension system for suspending a riser from a subsea wellhead housing using a running tool. The system comprises a surface wellhead housing, a riser hanger and a load shoulder. The surface wellhead housing comprises a bore, a shoulder profile, a lock profile and a support ring. The riser hanger assembly comprises a hanger body, an adjustable suspension mechanism rotationally coupled with the hanger body and a lock ring expandable into engagement with the lock profile. The load shoulder assembly couples with the riser hanger assembly and comprises a lock ring expandable into engagement with the shoulder profile. The invention further claims a multi-function running tool that requires only a single trip and which can manipulate, latch and back up a tie-back adapter into the downhole equipment and provide positive preloaded, locked-in, tension of the riser.

What is claimed is: 
     
         1 . A system for tying back a riser under tension from a platform to a subsea wellhead housing using a running tool, comprising:
 a surface wellhead housing comprising a bore;   a riser hanger assembly installable in the bore and comprising:
 a hanger body to support the riser; and 
 an adjustable suspension mechanism coupled with the hanger body; 
   a load shoulder assembly releasably coupled with the riser hanger assembly and comprising a load shoulder, the load shoulder assembly being releasable from the riser hanger assembly and lockable to the wellhead housing inside the bore using force from the riser hanger assembly; and   wherein the adjustable suspension mechanism is axially adjustable relative to the hanger body to engage the load shoulder and support the riser hanger with the riser in tension.   
     
     
         2 . The adjustable riser suspension system of  claim 1 , further comprising:
 the surface wellhead housing further comprising:
 a bore wall; and 
 a support ring selectively extendable from a position recessed into the bore wall to an extended position within the bore; and 
   wherein the load shoulder assembly is restricted from movement upon engagement with the support ring in the extended position to allow application of force from the riser hanger assembly.   
     
     
         3 . The adjustable riser suspension system of  claim 1 , further comprising:
 the surface wellhead housing further comprising:
 a bore wall; and 
 a shoulder profile recessed into the bore wall; and 
   the load shoulder assembly comprising a shoulder lock ring expandable into engagement with the shoulder profile to lock the load shoulder assembly to the surface wellhead.   
     
     
         4 . The adjustable riser suspension system of  claim 1 , further comprising:
 the surface wellhead housing further comprising:
 a bore wall; and 
 a lock profile recessed into the bore wall; and 
   the riser hanger assembly further comprising a hanger lock ring expandable into engagement with the lock profile to lock the riser hanger assembly to the surface wellhead.   
     
     
         5 . The adjustable riser suspension system of  claim 1 , further comprising an overshot sleeve, wherein the running tool rotates the overshot sleeve about the riser hanger to engage the load shoulder assembly into the lock profile. 
     
     
         6 . The adjustable riser suspension system of  claim 1 , further comprising a seal assembly with upper and lower ends. 
     
     
         7 . The adjustable riser suspension system of  claim 6 , wherein the seal assembly comprises metal-to-metal seals. 
     
     
         8 . The adjustable riser suspension system of  claim 6 , wherein the seal assembly comprises elastomeric seals. 
     
     
         9 . The adjustable riser suspension system of  claim 1 , wherein the riser, load shoulder and hanger are installable in one trip. 
     
     
         10 . A method for tying back a riser under tension from a platform to a subsea wellhead housing, comprising:
 coupling the riser to a surface wellhead and suspending the riser and a riser hanger assembly inside an outer riser, wherein the riser hanger assembly comprises an adjustable suspension mechanism;   lowering the riser hanger assembly downward relative to the riser, causing a lower end of the riser to engage the subsea wellhead;   raising the riser hanger assembly upward relative to the riser;   lowering the adjustable suspension mechanism relative to the riser to engage with a load shoulder assembly, wherein the adjustable suspension mechanism supports the riser hanger assembly when engaged with the load shoulder assembly.   
     
     
         11 . The method of  claim 10 , wherein the surface wellhead housing further comprises:
 a bore wall; and   a support ring selectively extendable from a position recessed into the bore wall to an extended position within the bore; and   wherein the load shoulder assembly is restricted from movement upon engagement with the support ring in the extended position to allow application of force from the riser hanger assembly.   
     
     
         12 . The method of  claim 10 , wherein the surface wellhead housing further comprises:
 a bore wall; and   a shoulder profile recessed into the bore wall; and   the load shoulder assembly comprising a shoulder lock ring expandable into engagement with the shoulder profile to lock the load shoulder assembly to the surface wellhead.   
     
     
         13 . The method of  claim 10 , wherein the surface wellhead housing further comprises:
 a bore wall; and   a lock profile recessed into the bore wall; and   the riser hanger assembly further comprising a hanger lock ring expandable into engagement with the lock profile to lock the riser hanger assembly to the surface wellhead.   
     
     
         14 . The adjustable riser suspension system of  claim 10 , further comprising an overshot sleeve, wherein the running tool rotates the overshot sleeve about the riser hanger to engage the load shoulder assembly into the lock profile. 
     
     
         15 . The adjustable riser suspension system of  claim 10 , further comprising a seal assembly with upper and lower ends. 
     
     
         16 . The adjustable riser suspension system of  claim 15 , wherein the seal assembly comprises metal-to-metal seals. 
     
     
         17 . The adjustable riser suspension system of  claim 15 , wherein the seal assembly comprises elastomeric seals. 
     
     
         18 . The adjustable riser suspension system of  claim 10 , wherein the riser, load shoulder and hanger are installable in one trip.