Riser disconnect package for lower marine riser package, and annular-release flex-joint assemblies

Abstract

A riser disconnect/reconnect system having a disconnection package (RDP) and a modified lower marine riser package (LMRP) are provided for quick disconnection of the marine drilling riser (MDR) from the LMRP to facilitate access to the LMRP or BOP stack. The RDP includes a flex joint and a hydraulically-actuated release connector (RC) with a connecting mandrel that engages a modified LMRP. In an emergency event, the RDP is disconnected from the LMRP allowing access to the BOP stack for intervention. The RDP may be disconnected from the LMRP for recovery of the LMRP or BOP stack to the surface for repair or maintenance without recovering the MDR. The RC joins the flex joint to the uppermost annular blowout preventer in the LMRP. The release connector can be used in a standard or inverted position. Also provided are structural cages with complementary stab plates allowing access to various bypass ports and controls.

What is claimed is: 
     
         1 . A subsea assembly for an offshore well comprising in a functional order:
 a flex joint configured on one end to engage a marine drilling riser;   a hydraulically-actuated release connector configured to engage a second end of said flex joint,   a connector mandrel configured to engage said release connector; and   an annular blowout preventer having a top section and a bottom section, wherein said connector mandrel is an integral part of said top section and wherein said annular blowout preventer comprises a bypass port and line;   a first structural cage housing said flex joint and said hydraulically-actuated release connector connector, said first cage having a first stab plate;   a second structural cage housing said connector mandrel and said annular blowout preventer, said second cage having a second stab plate;   wherein said first and said second stab plates are configured to engagingly mate and having complementary access openings to said bypass port and line.   
     
     
         2 . The subsea assembly of  claim 1  further comprising a second annular blow out preventer. and a second hydraulically-actuated release connector. 
     
     
         3 . The subsea assembly of  claim 1  further comprising a seal plate on said connector mandrel, wherein said seal plate is configured to receive and latch to a containment dome. 
     
     
         4 . The subsea assembly of  claim 3 , further comprising a second seal plate wherein said second seal plate is attached to said flex joint. 
     
     
         5 . The subsea assembly of  claim 1 , further comprising a second connector mandrel configured to engage said second release connector wherein said second connector mandrel comprises integrated within a third seal plate. 
     
     
         6 . The subsea assembly of  claim 1 , wherein said first structural cage comprises a male part of an alignment cylinder and said second structural cage comprises the female part of an alignment cylinder that engagingly mates with said male part. 
     
     
         7 . A mechanical locking connector comprising:
 An enclosure having a proximal end and a distal end, a plurality of spring latches attached to the distal end of the enclosure, said spring latches configured to latch to a profile on a latch plate of a subsea assembly.   
     
     
         8 . The mechanical locking connector of  claim 1  wherein the enclosure has a bore through its proximal end. 
     
     
         9 . The mechanical connector of  claim 1 , wherein the proximal end of the enclosure further comprises an API flange, a clamp hub or a flowline connection. 
     
     
         10 . The mechanical locking connector of  claim 1  further comprising a seal for sealing the interface between a mandrel profile on said subsea assembly and said connector. 
     
     
         11 . The mechanical connector of  claim 1 , wherein said seal is a seal gasket. 
     
     
         12 . The mechanical locking connector of  claim 1 , wherein said subsea assembly is a Christmas tree, a well head, a lower marine riser stack, a blowout preventer stack or a mandrel. 
     
     
         13 . A method for retrieving a lower marine riser package to a mobile offshore drilling unit comprising:
 disconnecting a marine drilling riser from said lower marine riser package;   suspending said marine drilling riser from the drilling unit;   disconnecting said lower marine riser package from said lower blowout preventer stack; and   retrieving the lower marine riser package to the surface while the marine drilling riser is suspended from the drilling unit.   
     
     
         14 . A method for containing an offshore well comprising:
 disconnecting a riser disconnect package from a lower marine riser package by actuating a hydraulically actuated release connector;   exposing a mandrel, wherein the mandrel is connected to an upper annular blowout preventer; and   affixing a capping stack or a containment dome on the mandrel.   
     
     
         15 . A method for containing an offshore well comprising:
 disconnecting a flex joint from an upper annular blow out preventer of an lower marine riser package by actuating a hydraulically-actuated release connector integrated onto said upper annular blowout preventer; and   affixing a capping stack or a containment dome onto said release connector.   
     
     
         16 . The method of  claim 15 , wherein the containment dome comprises a guidance funnel, a landing swivel, a vented interface plate and at least one control valve. 
     
     
         17 . The method of  claim 15  further comprising the step of providing access to bypass ports located on the annular blowout preventer. 
     
     
         18 . The method of  claim 17 , further comprising the step of redirecting flow from the well through said bypass ports on an annular blowout preventer. 
     
     
         19 . A method for containing an offshore well comprising:
 disconnecting a riser disconnect package from a lower marine riser package by actuating a hydraulically-actuated release connector;   exposing a mandrel, wherein said mandrel is connected to an upper annular blowout preventer; and   affixing a mechanical locking connector on said mandrel.