Protecting a Stationary Vessel from Encroaching Ice

Abstract

Techniques are provided for protecting a stationary vessel from encroaching ice. In an example, a system has a subsea mount disposed on a seafloor and a thruster disposed on the subsea mount under a water surface. The thruster is configured to destabilize a water column under the encroaching ice.

What is claimed is: 
     
         1 . A system for protecting a stationary vessel from encroaching ice, comprising:
 a subsea mount disposed on a seafloor; and   a thruster disposed on the subsea mount under a water surface, wherein the thruster is configured to destabilize a water column under the encroaching ice.   
     
     
         2 . The system of  claim 1 , comprising a cable from the stationary vessel to the subsea mount, wherein the cable carries power, control signals, or both to the thruster. 
     
     
         3 . The system of  claim 1 , comprising a sonar sensor configured to detect encroaching ice. 
     
     
         4 . The system of  claim 1 , wherein the subsea mount comprises a template and one or more pilings. 
     
     
         5 . The system of  claim 4 , wherein the one or more piles comprise a suction pile set into the seafloor. 
     
     
         6 . The system of  claim 1 , wherein the subsea mount comprises a rail to allow the position of the thruster to be changed. 
     
     
         7 . The system of  claim 1 , wherein the thruster pulls water in through the top of the thruster and ejects the water downwards towards the seafloor. 
     
     
         8 . The system of  claim 1 , wherein the thruster pulls water in through the bottom of the thruster and ejects water upwards towards the water surface. 
     
     
         9 . The system of  claim 1 , wherein the thruster comprises one or more side openings configured to move the thruster to the side. 
     
     
         10 . The system of  claim 1 , wherein the thruster comprises a bottom grate to redirect the water outward from the thruster. 
     
     
         11 . The system of  claim 1 , wherein the thruster has one or more buoyancy compartments for adjusting the vertical depth of the thruster. 
     
     
         12 . The system of  claim 1 , comprising a sensor on the thruster configured to detect the approach of an object and instruct the thruster to shut down, lower its depth in the water, or both. 
     
     
         13 . The system of  claim 1 , wherein a plurality of subsea mounts are configured to form multiple rails in arcs. 
     
     
         14 . The system of  claim 1 , wherein the thruster is disposed on the subsea mount using a tether which is coiled to allow vertical mobility from the mount. 
     
     
         15 . The system of  claim 1 , comprising a subsea generator to provide power for the thruster. 
     
     
         16 . A method for protecting a sea surface location from encroaching ice, comprising:
 detecting encroaching ice; and   activating a seafloor mounted thruster, wherein the thruster destabilizes the water column below the ice.   
     
     
         17 . The method of  claim 16 , comprising lowering the thruster to avoid impact with an object. 
     
     
         18 . The method of  claim 16 , comprising moving thrusters to positions calculated to intersect the encroaching ice. 
     
     
         19 . The method of  claim 16 , comprising powering the thrusters from a vessel at the sea surface location. 
     
     
         20 . The method of  claim 16 , wherein destabilizing the water column below the ice includes pulling water in through the top of the thruster and ejecting the water downwards towards the seafloor. 
     
     
         21 . The method of  claim 16 , wherein destabilizing the water column below the ice includes pulling water in through the bottom of the thruster and ejecting the water upwards towards the water surface. 
     
     
         22 . A method for producing hydrocarbons, comprising:
 positioning a vessel at a location on a sea surface;   positioning a thruster attached to a mount on a seafloor;   producing hydrocarbons from a well using the vessel;   detecting ice that is encroaching on the vessel; and
 activating the thruster to destabilize the water column below the ice.