Liquid based boiler

Abstract

Methods and systems generate steam for oil recovery operations. The systems may limit feedwater pretreatment expenses and fouling issues. In the method, dirty feedwater introduced into a vessel containing a hot liquid hydrocarbon, e.g., an already hot produced hydrocarbon, contacts the hydrocarbon and is vaporized into steam. The steam collects in a top of the vessel and may be conveyed to the wellhead for downhole injection. The hydrocarbon remains heated by a closed circulation loop passing back and forth through a lower half of the vessel containing the hydrocarbon. The fluid in this loop remains isolated from contaminates in the water to limit fouling in tubes, which form the loop and can employ normal metallurgy to save on capital costs. The hydrocarbon can be treated as needed to remove accumulating salts and/or entrained water and recycled.

What is claimed is: 
     
         1 . A steam generator system for heavy oil production, comprising:
 a vessel comprising a hydrocarbon;   a closed heat transfer fluid circulation loop that passes in part through the vessel to heat the hydrocarbon;   a pump for pressurizing a feedwater stream and fluidly connected to nozzles in the vessel, wherein the nozzles spray the feedwater onto the hydrocarbon to produce steam; and   a wellhead injection system for conveying the steam into an oil reservoir and coupled to an exit port near a top of the vessel for collecting the steam.   
     
     
         2 . The steam generator system of  claim 1 , wherein the closed heat transfer fluid circulation loop includes a heat transfer fluid, a heater and a pump. 
     
     
         3 . The steam generator system of  claim 1 , wherein the closed heat transfer fluid circulation loop includes a heat transfer fluid selected from butane, molten sodium, molten sodium-potassium, DOWTHERM and THERMINOL. 
     
     
         4 . The steam generator system of  claim 1 , further comprising a hydrocarbon treatment loop in fluid connection with the vessel, wherein the hydrocarbon treatment loop desalts the hydrocarbon. 
     
     
         5 . The steam generator system of  claim 2 , further comprising a hydrocarbon treatment loop in fluid connection with the vessel, wherein the hydrocarbon treatment loop desalts the hydrocarbon. 
     
     
         6 . The steam generator system of  claim 3 , further comprising a hydrocarbon treatment loop in fluid connection with the vessel, wherein the hydrocarbon treatment loop desalts the hydrocarbon. 
     
     
         7 . A liquid steam generator, comprising:
 a vessel comprising a hydrocarbon in a lower portion of the vessel;   a closed heat transfer fluid circulation loop containing a heat transfer fluid, wherein the loop passes in part through the lower half of the vessel to heat the hydrocarbon and a remainder of the loop passes to a heater and a pump to heat and circulate the heat transfer fluid;   a hydrocarbon treatment loop for cleaning the hydrocarbon, wherein the hydrocarbon treatment loop includes a pump and a desalter;   a pump for pressurizing a feedwater stream fluidly connected to nozzles in an upper portion of the vessel, wherein the nozzles spray the feedwater onto the hydrocarbon to produce steam; and   a wellhead injection system for conveying the steam into an oil reservoir and coupled to an exit port near a top of the vessel for collecting the steam.   
     
     
         8 . The steam generator system of  claim 7 , wherein the hydrocarbon heat transfer fluid is selected from butane, molten sodium, molten sodium-potassium, DOWTHERM and THERMINOL. 
     
     
         9 . The liquid steam generator of  claim 7 , wherein the feedwater is untreated produced water. 
     
     
         10 . The liquid steam generator of  claim 9 , wherein the hydrocarbon fluid is a produced hydrocarbon separated from the produced water. 
     
     
         11 . The liquid steam generator of  claim 7 , wherein a mixture of the steam and at least some of the hydrocarbons with less than eight carbon atoms per molecule output the vessel through the exit port. 
     
     
         12 . The liquid steam generator of  claim 7 , wherein the treatment loop includes a visbreaker. 
     
     
         13 . A method of generating steam, comprising:
 circulating a heat transfer fluid through a closed loop for transfer of thermal energy from a heater along the loop to hydrocarbons in a vessel as a portion of the loop passes through the vessel; and   introducing feedwater into contact with the hydrocarbons in the vessel to vaporize the feedwater into steam.   
     
     
         14 . The method of  claim 13 , wherein the feedwater is untreated produced water. 
     
     
         15 . The method of  claim 13 , wherein the feedwater is blowdown from one of a steam generator and an evaporator. 
     
     
         16 . The method of  claim 13 , wherein the heat transfer fluid is selected from butane, molten sodium, molten sodium-potassium, DOWTHERM and THERMINOL. 
     
     
         17 . The method of  claim 13 , further comprising injecting the steam into an oil reservoir. 
     
     
         18 . The method of  claim 13 , further comprising desalting the hydrocarbon in the vessel. 
     
     
         19 . The method of  claim 13 , wherein an output from the vessel includes a mixture of the steam and at least some of the hydrocarbons with less than eight carbon atoms per molecule. 
     
     
         20 . The method of  claim 13 , further comprising circulating the hydrocarbons into contact with the steam output from the vessel.