LIQUID BASED BOILER

Method.s 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 hack 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.