Explosive disconnect

Abstract

A coupling system includes a lower marine riser package having a connector at a bottom end and at least one blowout preventer pressure control element coupled to a wellhead and having a connector at an upper end. Explosively frangible fasteners are used to couple the connector on the lower marine riser package to the connector on the at least one blowout preventer pressure control element. A method for separating a lower marine riser package from a blowout preventer coupled to a subsea wellhead includes closing a least one pressure control element in the blowout preventer. At least one explosively frangible fastener coupling the blowout preventer to the lower marine riser package is detonated. The lower marine riser package is then lifted from the blowout preventer.

What is claimed is: 
     
         1 . A coupling system, comprising:
 a lower marine riser package having a connector at a bottom end thereof;   at least one blowout preventer pressure control element coupled to a wellhead and having a connector at an upper end thereof;   explosively frangible fasteners comprising explosively frangible nuts disposed to couple the connector on the lower marine riser package to the connector on the at least one blowout preventer pressure control element.   
     
     
         2 . The coupling system of  claim 1  wherein the connector on the lower marine riser package is coupled to the connector on the at least one blowout preventer pressure control element by the explosively frangible fasteners being disposed through a corresponding bolt flange on each of the connector on the lower marine riser package and the connector on the at least one blowout preventer pressure control element. 
     
     
         3 . The coupling system of  claim 1  wherein the connector on the at least one blowout preventer pressure control element comprises a profile connection at one longitudinal end. 
     
     
         4 . The coupling system of  claim 1  wherein the connector on the lower marine riser package comprises a profile connection to couple the connector on the lower marine riser package to the lower marine riser package. 
     
     
         5 . The coupling system of  claim 1  further comprising a plurality of blowout preventer pressure control elements coupled to the wellhead. 
     
     
         6 . The coupling system of  claim 1  wherein the lower marine riser package comprises at least one blowout preventer pressure control element. 
     
     
         7 . A method for separating a lower marine riser package from a blowout preventer coupled to a subsea wellhead, comprising:
 closing at least one pressure control element in the blowout preventer;   detonating at least one explosively frangible fastener coupling the blowout preventer to the lower marine riser package, the at least one explosively frsngible fastener comprising an explosively frangible nut; and   lifting the lower marine riser package from the blowout preventer.   
     
     
         8 . The method of  claim 7  further comprising, prior to detonating the at least one explosively frangible fastener, uncoupling at least one auxiliary line extending between the lower marine riser package and the blowout preventer. 
     
     
         9 . The method of  claim 7  wherein a connector on the lower marine riser package is coupled to a corresponding connector on the blowout preventer by a plurality of explosively frangible fasteners being disposed through a corresponding bolt flange on each of the connector on the lower marine riser package and the connector on the blowout preventer. 
     
     
         10 . The method of  claim 9  wherein the connector on the blowout preventer comprises a profile connection at one longitudinal end. 
     
     
         11 . The method of  claim 10  wherein the connector on the lower marine riser package comprises a profile connection to couple the connector on the lower marine riser package to the lower marine riser package.