Enhanced floating power generation system

Abstract

A system is provided for more efficiently using offshore produced hydrocarbons, where the produced hydrocarbons contain considerable amounts of liquid hydrocarbons and both heavy gaseous hydrocarbons (at least two carbon atoms per molecule) and light hydrocarbons (with two or less carbon atoms per molecule). The produced hydrocarbons are separated into liquid hydrocarbons which are stored in a tank structure ( 183 ) for later offloading to a tanker ( 56 ), and into heavy gaseous hydrocarbons and light hydrocarbons. The heavy gaseous hydrocarbons are liquefied and stored in a tank ( 212 ) for fueling an electricity generator unit ( 192 ) when needed, and the light hydrocarbons are immediately used to fuel the electricity generator unit ( 192 ).

1 . A method for the production and transport of hydrocarbons using a floating structure that floats at the sea surface, that has electrically powered equipment, and that is connected by a riser to a subsea reservoir that produces hydrocarbons that include both gaseous and liquid hydrocarbons comprising: 
 separating the produced hydrocarbons into gaseous hydrocarbons and liquid hydrocarbons;    storing the liquid hydrocarbons in a tank structure, and offloading the liquid hydrocarbons to a tanker at intervals;    using at least some of the gaseous hydrocarbons to fuel an energized electrical generator unit to produce electricity, and using at least some of said electricity to power at least said electrically powered equipment on the floating structure.    
   
   
       2 . The method described in  claim 1  including: 
 separating the gaseous hydrocarbons into heavier gaseous hydrocarbons that have a number of carbon atoms per molecule that is at least two, and light gaseous hydrocarbons that have a number of carbon atoms per molecule that is less than three;    storing said heavier gaseous hydrocarbons in a tank on the floating structure.    
   
   
       3 . The method described in  claim 2  including: 
 using said light gaseous hydrocarbons to fuel said energized generator unit to produce electricity to the extent that said light gaseous hydrocarbons are available to provide fuel required for said generator unit, and using said heavier gaseous hydrocarbons that have been stored to fuel said generator unit when sufficient light gaseous hydrocarbons are not available.    
   
   
       4 . The method described in  claim 3  including: 
 when the tank that stores heavier gaseous hydrocarbons is full, transporting some of said heavier gaseous hydrocarbons by ship away from said floating structure.    
   
   
       5 . The method described in  claim 1  including: 
 carrying electricity from said electric generator unit through an undersea electric cable to a shore facility that is located on shore;    said step of carrying electricity including carrying direct current electricity through said undersea cable, and converting said direct current electricity to alternating current electricity at said shore facility.    
   
   
       6 . The method described in  claim 1  including: 
 separating said gaseous hydrocarbons and delivering primarily methane to said electrical generator unit, and storing at least propane in a tank.    
   
   
       7 . A hydrocarbon production system which includes a floating structure that floats at the sea surface, that carries electrically powered equipment, and that is connected through a riser to an undersea reservoir that produces liquid hydrocarbons and natural gas, comprising: 
 a processor connected to said riser that separates liquid hydrocarbons from components of natural gas;    a liquid tank structure connected to said processor to store liquid hydrocarbons received from said processor;    an electricity generator unit;    a conduit structure that carries natural gas from said processor to said generator unit to fuel said generator unit with natural gas.    
   
   
       8 . The system described in  claim 7  wherein: 
 said processor separates light gases that include methane, from heavy gases that include butane;    said conduit structure carries said light gases from said separator to said generator unit to fuel it; and including    a heavy gas tank that stores said heavy gases, said heavy gas tank being coupled to said generator unit to supply fuel when there are insufficient of said light gases.