Subsea cooling system

Abstract

A subsea hydrocarbon cooling and heat transfer system is provided. The system includes one or more subsea hydrocarbon process fluid heat exchangers arranged in heat exchange communication between a hydrocarbon process fluid and a cooling medium fluid, a cooling medium fluid distribution pipe system connected to the hydrocarbon process fluid heat exchangers, and a subsea cooling unit for cooling the cooling medium fluid. After passing through one of said heat exchangers, a heated cooling medium can act as a heat transfer fluid to re-heat another hydrocarbon process fluid.

1 . A subsea hydrocarbon cooling system, said system comprising:
 one or more hydrocarbon process fluid heat exchangers arranged in heat exchange communication between a hydrocarbon process fluid and a single phase cooling medium fluid, wherein the one or more hydrocarbon process fluid heat exchangers are located subsea;   a cooling medium fluid distribution pipe system connected to the hydrocarbon process fluid heat exchangers; and,   a subsea cooling unit for cooling the cooling medium fluid, the subsea cooling unit comprising:   an inlet and an outlet arranged in fluid communication with the cooling medium fluid distribution pipe system;   a flow controller to control the flow of cooling medium fluid in said system;   one or more subsea cooling modules, each cooling module comprising a plurality of cooling pipes configured in heat exchange relationship with surrounding seawater;   a first conduit for providing fluid communication between the inlet and the one or more subsea cooling modules; and   a second conduit for providing fluid communication between the one or more subsea cooling modules and the outlet.   
     
     
         2 . The system according to  claim 1 , wherein the one or more subsea cooling modules are located above the sea bed. 
     
     
         3 . The system according to  claim 2 , wherein the one or more subsea cooling modules are supported by one or more respective mud mats residing on the sea bed. 
     
     
         4 . The system according to  claim 3 , wherein the one or more respective mud mats comprise a pallet. 
     
     
         5 . The system according to  claim 4 , wherein the one or more respective mud mats incorporate lengths of pipe through which the cooling medium fluid is circulated and/or distributed to the one or more cooling modules. 
     
     
         6 . The system according to  claim 1 , wherein the first and second conduits are arranged in fluid communication with the cooling modules via respective seabed pipes. 
     
     
         7 . The system according to  claim 1 , wherein the flow controller comprises a pump or a flow control valve. 
     
     
         8 . A subsea cooling unit for use in a hydrocarbon process fluid cooling system, said unit being adapted to cool a single phase cooling medium fluid circulating through a subsea heat exchange circuit, the subsea heat exchange circuit having a cooling medium fluid distribution pipe system, the subsea cooling unit comprising:
 an inlet and an outlet arranged in fluid communication with the cooling medium fluid distribution pipe system;   a flow controller to control the flow of cooling medium fluid in the subsea heat exchange circuit;   one or more subsea cooling modules, each cooling module comprising a plurality of cooling pipes configured in heat exchange relationship with surrounding seawater;   a first conduit arranged to provide fluid communication between the inlet and the one or more subsea cooling modules; and   a second conduit arranged to provide fluid communication between the one or more subsea cooling modules and the outlet.   
     
     
         9 . The subsea cooling unit according to  claim 8 , wherein the plurality of cooling pipes are configured in a manifold of parallel lengths of pipe. 
     
     
         10 . The subsea cooling unit according to  claim 8 , wherein the plurality of cooling pipes are configured in a coiled arrangement. 
     
     
         11 . The subsea cooling unit according to  claim 8 , wherein the one or more subsea cooling modules is coiled around at least part of a substructure of an offshore platform. 
     
     
         12 . The subsea cooling unit according to  claim 8 , wherein the one or more subsea cooling modules is coiled around a subsea facility. 
     
     
         13 . The subsea cooling unit according to  claim 8 , wherein the one or more subsea cooling modules is provided with an open-ended shroud to direct flow of seawater over the subsea cooling modules and/or increase thermal convection from the subsea cooling modules. 
     
     
         14 . The subsea cooling unit according to  claim 13 , wherein the shroud is provided with baffles, vanes or means for increasing and/or directing flow of seawater over the subsea cooling modules. 
     
     
         15 . A method of cooling a hydrocarbon process fluid, said method comprising:
 passing the hydrocarbon process fluid through a subsea hydrocarbon process fluid heat exchanger and passing a single phase cooling medium fluid through a cooling medium fluid distribution pipe system, wherein said subsea heat exchanger and said pipe system are configured to provide heat exchange communication between the hydrocarbon process fluid and the cooling medium fluid, thereby producing a cooled hydrocarbon fluid and a heated cooling medium fluid; and,   cooling the heated cooling medium fluid by passing the heated cooling medium fluid through a subsea cooling unit, wherein the subsea cooling unit comprises:   an inlet and an outlet arranged in fluid communication with the cooling medium fluid distribution pipe system;   a flow controller to control the flow of cooling medium fluid through a subsea heat exchange circuit;   one or more subsea cooling modules, each cooling module comprising a plurality of cooling pipes configured in heat exchange relationship with surrounding seawater;   a first conduit arranged to provide fluid communication between the inlet and the one or more subsea cooling modules; and   a second conduit arranged to provide fluid communication between the one or more subsea cooling modules and the outlet.   
     
     
         16 . The method according to  claim 15 , wherein prior to passing the heated cooling medium fluid through the subsea cooling unit, said method comprises passing the heated cooling medium fluid through said pipe distribution system and passing a second hydrocarbon process fluid through a second subsea heat exchanger, wherein said pipe distribution system is configured in a heat exchange relationship with the second subsea heat exchanger. 
     
     
         17 . The method according to  claim 16 , wherein the cooling medium fluid is cooled by thermal exchange with the second hydrocarbon process fluid. 
     
     
         18 . The method according to  claim 16 , wherein the cooling medium fluid is heated by thermal exchange with the second hydrocarbon process fluid.