Subsea riser disconnect and method

Abstract

A subsea riser disconnect assemblymay be actuated from a drilling rig DR by axial movement of an upper riserrelative to a lower riser, for disconnecting the upper riserfrom the lower riser. A subsea riser valve assemblymay be actuated from the drilling rig DR by axial movement of the upper riserrelative to the lower riser, for sealing an interior portion of the lower riserand well bore WB below the subsea riser valve assembly. A drill pipe disconnectmay be actuated from a drilling rig DR, either onshore or offshore, for disconnecting an upper portion of drill pipefrom a lower portion of drill pipe. The drill pipe disconnectmay be actuatable by hydraulic and/or mechanical forces applied to the drill pipe disconnectfrom the drilling rig DR. The drill pipe disconnectmay be compatible for use with or without the subsea riser disconnect assemblyand/or the subsea riser valve assembly. The component assemblies of this invention may improve the efficiency and lower the cost of recovering hydrocarbons by reducing drilling costs and time requirements. Also, the ability to relatively quickly disconnect a floating rig from a well may enhance the safety of persons and equipment facing hostile weather conditions or other emergency situations.