Method and system for subsea intervention using a dynamic seal

Abstract

A system for performing intervention operations in subsea installations, including a tubular which connects a subsea installation to a surface vessel, a conveyance designed to enter subsea installation to perform an intervention, and a non-retrievable subsea dynamic seal, which prevents hydrocarbons from reaching the vessel. A surface dynamic seal can be provided. A method for subsea intervention using the system and a corresponding subsea dynamic seal apparatus are provided.

1 . A system for subsea intervention, the system comprising:
 at least one non-retrievable subsea dynamic seal provided between a surface vessel and a subsea well or a subsea installation;   a tubular extending between the at least one subsea dynamic seal and the surface vessel; and   a toolstring coupled to a conveyance and lowered through the tubular to the subsea well or the subsea installation, the toolstring passing through the at least one subsea dynamic seal,   wherein the at least one subsea dynamic seal establishes a dynamic, pressure tight seal on the conveyance to prevent the entry of borehole fluids into the tubular.   
     
     
         2 . The system of  claim 1 , further comprising:
 an intervention package located between the surface vessel and above the subsea well or the subsea installation.   
     
     
         3 . The system of  claim 2 , further comprising:
 at least one subsea lubricator located above the intervention package.   
     
     
         4 . The system of  claim 1 , further comprising:
 at least one surface dynamic seal located on or in proximity of the surface vessel for establishing a dynamic, pressure tight seal on the conveyance at an upper end of the tubular and so as to pressurize an annulus between the conveyance and the tubular.   
     
     
         5 . A method for subsea intervention, the method comprising:
 installing at least one non-retrievable subsea dynamic seal between a surface vessel and a subsea well or a subsea installation;   installing a tubular extending between the subsea dynamic seal and the surface vessel;   lowering a toolstring coupled to a conveyance through the tubular from the vessel into the subsea well or the subsea installation and passing the toolstring through the subsea dynamic seal; and   establishing a dynamic, pressure tight seal with the at least one subsea dynamic seal on the conveyance for preventing borehole fluids from entering into the tubular.   
     
     
         6 . The method of  claim 5 , further comprising:
 installing an intervention package between the surface vessel and above the subsea well or the installation.   
     
     
         7 . The method of  claim 6 , further comprising:
 lowering the toolstring into a subsea lubricator before the toolstring is lowered into the subsea well or the subsea installation, the subsea lubricator located above the intervention package.   
     
     
         8 . The method of  claim 7 , further comprising:
 establishing a dynamic, pressure tight seal on the conveyance at an upper end of the tubular so as to pressurize an annulus between the conveyance and the tubular with at least one surface dynamic seal located on or in proximity of the surface vessel.   
     
     
         9 . The method of  claim 8 , further comprising:
 equalizing the pressure above well barriers in the intervention package with the pressure below the well barriers;   opening the well barriers in the intervention package;   performing an intervention operation;   retrieving the toolstring into the lubricator;   closing the well barriers in the intervention package;   bleeding off pressure from the lubricator and from the tubular;   opening the subsea dynamic seal; and   retrieving the toolstring to the surface through the tubular.   
     
     
         10 . A non-retrievable subsea dynamic seal apparatus for subsea intervention, the apparatus comprising:
 at least one non-retrievable subsea dynamic seal adapted to be coupled between a surface vessel and a subsea well or a subsea installation;   the at least one subsea dynamic seal adapted to be coupled to a tubular extending to the surface vessel;   the at least one subsea dynamic seal adapted to allow a toolstring to pass therethrough, the toolstring coupled to a conveyance and lowered through the tubular to the subsea well or the subsea installation; and   the at least one subsea dynamic seal configured to establish a dynamic, pressure tight seal on the conveyance to prevent the entry of borehole fluids into the tubular.   
     
     
         11 . The apparatus of  claim 10 , wherein an intervention package is located between the surface vessel and above the subsea well or the subsea installation. 
     
     
         12 . The apparatus of  claim 11 , wherein at least one subsea lubricator is located above the intervention package. 
     
     
         13 . The apparatus of  claim 10 , wherein at least one surface dynamic seal is located on or in proximity of the surface vessel for establishing a dynamic, surface tight seal on the conveyance at an upper end of the tubular and so as to pressurize an annulus between the conveyance and the tubular. 
     
     
         14 . The apparatus of  claim 10 , further comprising:
 a set of one or more ram-type devices coupled to least one non-retrievable subsea dynamic seal and configured to cause the at least one non-retrievable subsea dynamic seal to form a dynamic, pressure tight seal on the conveyance.   
     
     
         15 . The apparatus of  claim 14 , wherein the set of one or more ram-type devices is configured to open the at least one non-retrievable subsea dynamic seal so as to allow the toolstring to pass therethrough, and close the at least one non-retrievable subsea dynamic seal so as to establish the dynamic seal on the conveyance.