Subsea system delivery to seabed

Abstract

Methods and systems relate to seabed operations, such as well intervention or capping, involving subsea equipment and subsea handling of the equipment, which may be associated with hydrocarbon wells or pipelines. A subsea system submerges during deployment and is landed on the seabed. The system may include a suspension assembly coupled to a frame structure for carrying equipment used in the operations. The deployment of the system may include deploying the frame structure with the equipment from a floating vessel connected to an anchored tether and moving the frame structure under water along the tether toward where anchored and the location for the seabed operations.

1 . A method of deploying a subsea system for seabed operations, comprising:
 setting an anchor coupled to a tether thereby fixed to the seabed,   coupling the tether to a frame structure carrying equipment to perform the operations;   deploying the frame structure with the equipment from a floating vessel connected to the tether while anchored;   moving the frame structure under water along the tether toward where anchored and the location for the seabed operations; and   landing the frame structure on the seabed at the location of the operations.   
     
     
         2 . The method according to  claim 1 , wherein the floating vessel is disposed at least 1000 meters in a horizontal direction away from above a location for the seabed operations during the deploying of the frame structure. 
     
     
         3 . The method according to  claim 1 , wherein the moving of the frame structure is by advancing the tether with a winch on the floating vessel while the frame structure grips the tether. 
     
     
         4 . The method according to  claim 1 , wherein the moving of the frame structure is by advancing the tether in a loop while the frame structure grips an advancing portion of the loop and a returning portion of the loop slides through a guide on the frame structure. 
     
     
         5 . The method according to  claim 1 , wherein the moving of the frame structure includes pulling the tether looped through a sheave coupled to the anchor creating a return portion of the tether going back to the floating vessel from the sheave and an opposite advancing portion of the tether gripped by the frame structure. 
     
     
         6 . The method according to  claim 1 , further comprising pulling the anchor from the floating vessel around an exclusion zone with an anchor handler to a point where the anchor is to be released for the setting with the tether intersecting the exclusion zone. 
     
     
         7 . The method according to  claim 1 , further comprising fixing the tether to the seabed at another location away from the anchor in a direction of the floating vessel. 
     
     
         8 . The method according to  claim 1 , further comprising moving a conduit along the tether toward where anchored by advancing the tether in a loop while the conduit is connected to an advancing portion of the loop. 
     
     
         9 . The method according to  claim 1 , wherein the landing of the frame structure includes controlling ballasts to set weight of the frame structure on the seabed. 
     
     
         10 . The method according to  claim 1 , wherein the equipment includes at least one of a well capping stack and a well containment stack installed on a well as part of the operations. 
     
     
         11 . A subsea system for seabed operations, comprising:
 a frame structure carrying equipment to perform the operations;   a tether anchored to the seabed and coupled to the frame structure for under water movement of the frame structure along the tether; and   a floating vessel connected to the tether for deployment of the frame structure with the equipment along the tether toward where anchored and the location for the seabed operations.   
     
     
         12 . The subsea system according to  claim 11 , wherein the floating vessel connected to the tether is disposed at least 1000 meters in a horizontal direction away from above a location for the seabed operations. 
     
     
         13 . The subsea system according to  claim 11 , wherein the frame structure is moveable by advancing the tether with a winch on the floating vessel while the frame structure grips the tether. 
     
     
         14 . The subsea system according to  claim 11 , wherein the frame structure is moveable by advancing the tether in a loop while the frame structure grips an advancing portion of the loop and a returning portion of the loop slides through a guide on the frame structure. 
     
     
         15 . The subsea system according to  claim 11 , wherein the frame structure is moveable by pulling the tether looped through a sheave coupled to the anchor creating a return portion of the tether going back to the floating vessel from the sheave and an opposite advancing portion of the tether gripped by the frame structure. 
     
     
         16 . The subsea system according to  claim 11 , further comprising an anchor handler to pull the anchor from the floating vessel in a desired path around an exclusion zone. 
     
     
         17 . The subsea system according to  claim 11 , wherein the tether is anchored to the seabed at first and second locations located toward the seabed operations and toward the floating vessel with respect to one another. 
     
     
         18 . The subsea system according to  claim 11 , further comprising a conduit moveable along the tether toward where anchored by advancing the tether in a loop while the conduit is connected to an advancing portion of the loop. 
     
     
         19 . The subsea system according to  claim 11 , wherein the frame structure includes ballasts controllable to set weight of the frame structure on the seabed. 
     
     
         20 . The subsea system according to  claim 11 , wherein the equipment includes at least one of a well capping stack and a well containment stack for installation on a well as part of the operations.