Offshore hydrocarbon cooling system

Abstract

An offshore hydrocarbon cooling system for an offshore platform is provided. The system includes one or more 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.

1 . A hydrocarbon cooling system for an offshore platform, said system comprising:
 one or more 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, the subsea cooling unit comprising:
 an inlet and an outlet arranged in fluid communication with the cooling medium fluid distribution pipe 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 riser arranged to provide fluid communication between the inlet and the one or more subsea cooling modules; and 
 a second riser arranged to provide fluid communication between the one or more subsea cooling modules and the outlet. 
   
     
     
         2 . The system according to  claim 1 , wherein the offshore platform is a fixed offshore platform. 
     
     
         3 . The system according to  claim 1 , wherein the offshore platform is a floating offshore platform. 
     
     
         4 . The system according to  claim 1 , wherein the one or more subsea cooling modules are located above the sea bed. 
     
     
         5 . The system according to  claim 4 , wherein the one or more subsea cooling modules are supported by one or more respective mud mats residing on the sea bed. 
     
     
         6 . The system according to  claim 5 , wherein the one or more respective mud mats comprise a pallet. 
     
     
         7 . The system according to  claim 5 , 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. 
     
     
         8 . The system according to  claim 1 , wherein the one or more cooling modules are located remotely from the offshore platform. 
     
     
         9 . The system according to  claim 8 , wherein the first and second risers are arranged in fluid communication with the cooling modules via respective seabed pipes. 
     
     
         10 . The system according to  claim 1 , wherein the one or more subsea cooling modules are located substantially laterally with respect to the offshore platform. 
     
     
         11 . The system according to  claim 10 , wherein the one or more subsea cooling modules are tethered to the offshore platform. 
     
     
         12 . The system according to  claim 1 , further comprising one or more pumps to circulate the cooling medium fluid through the heat exchange circuit and the subsea cooling unit. 
     
     
         13 . A subsea cooling unit for cooling a cooling medium fluid circulating through a heat exchange circuit on an offshore platform, the 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;   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 riser arranged to provide fluid communication between the inlet and the one or more subsea cooling modules; and   a second riser arranged to provide fluid communication between the one or more subsea cooling modules and the outlet.   
     
     
         14 . The subsea cooling unit according to  claim 13 , wherein the plurality of cooling pipes are configured in a manifold of parallel lengths of pipe. 
     
     
         15 . The subsea cooling unit according to  claim 13 , wherein the plurality of cooling pipes are configured in a coiled or other shaped arrangement. 
     
     
         16 . The subsea cooling unit according to  claim 13 , wherein the one or more subsea cooling modules is coiled around at least part of a substructure of the offshore platform. 
     
     
         17 . The subsea cooling unit according to  claim 13 , 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. 
     
     
         18 . The subsea cooling unit according to  claim 17 , wherein the shroud is provided with baffles, vanes or means for increasing and/or directing flow of seawater over the subsea cooling modules. 
     
     
         19 . A method of cooling a hydrocarbon process fluid on an offshore platform, said method comprising:
 passing the hydrocarbon process fluid through a hydrocarbon process fluid heat exchanger and passing a cooling medium fluid through a cooling medium fluid distribution pipe system, wherein said 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;   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 riser arranged to provide fluid communication between the inlet and the one or more subsea cooling modules; and   a second riser arranged to provide fluid communication between the one or more subsea cooling modules and the outlet.   
     
     
         20 . A method of processing a hydrocarbon process fluid on a topsides facility comprising:
 treating the hydrocarbon process fluid in one or more process steps to produce a treated hydrocarbon fluid, whereby one of the process steps comprises cooling the hydrocarbon process fluid;   wherein cooling the treated hydrocarbon process fluid comprises:   passing the treated hydrocarbon fluid through a hydrocarbon process fluid heat exchanger and passing a cooling medium fluid through a cooling medium fluid distribution pipe system, wherein said 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;   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 riser arranged to provide fluid communication between the inlet and the one or more subsea cooling modules; and   a second riser arranged to provide fluid communication between the one or more subsea cooling modules and the outlet.