Circulated heated transfer fluid heating of subsurface hydrocarbon formations

Abstract

A method of heating a subsurface formation includes introducing a molten salt into a first passageway of a conduit-in-conduit heater at a first location. The molten salt is passed through the conduit-in-conduit heater in the formation to a second location. Heat transfers from the molten salt to a treatment area during passage of the molten salt through the conduit-in-conduit heater. The molten salt is removed from the conduit-in-conduit heater at a second location spaced away from the first location.

1 - 772 . (canceled) 
     
     
         773 . A method of heating a subsurface formation, comprising:
 introducing a molten salt into a first passageway of a conduit-in-conduit heater at a first location;   passing the molten salt through the conduit-in-conduit heater in the formation to a second location, wherein heat transfers from the molten salt to a treatment area during passage of the molten salt through the conduit-in-conduit heater; and   removing molten salt from the conduit-in-conduit heater at a second location spaced away from the first location.   
     
     
         774 . The method of  claim 773 , wherein introducing the molten salt into the first passageway comprises introducing the heat transfer fluid into an inner conduit of the conduit-in-conduit heater. 
     
     
         775 . The method of  claim 773 , wherein introducing the molten salt into the first passageway comprises introducing the molten salt into an inner conduit of the conduit-in-conduit heater, and passing the molten salt through a flow switcher to change the flow from the inner conduit to the annular region between the inner conduit and an outer conduit. 
     
     
         776 . The method of  claim 775 , further comprising passing the molten salt through a second flow switcher to change the flow from the annular region between the inner conduit and the outer conduit to flow through the inner conduit. 
     
     
         777 . The method of  claim 773 , further comprising introducing a secondary heat transfer fluid into a second passageway of the conduit-in-conduit heater to ensure flowability of the molten salt in the first passageway. 
     
     
         778 . The method of  claim 777 , further comprising eliminating or reducing flow of the secondary heat transfer fluid in the second passageway after a temperature of the conduit-in-conduit heater is sufficient to ensure flowability of the molten salt. 
     
     
         779 - 783 . (canceled) 
     
     
         784 . A system for heating a subsurface formation, comprising:
 at least one fluid circulation system configured to provide a heat transfer fluid to a plurality of heaters in the formation; and   a plurality of heaters in the formation coupled to the circulation system, wherein at least one of the heaters comprises:
 a first conduit; 
 a second conduit positioned in the first conduit; and 
 a first flow switcher configured to change the flow of the heat transfer fluid from the second conduit to an annular region between the first conduit and the second conduit. 
   
     
     
         785 . The system of  claim 784 , wherein one or more of the heater are L-shaped heaters. 
     
     
         786 . The system of  claim 784 , wherein the heat transfer fluid comprises a molten salt and the heat transfer fluid flows through the second conduit adjacent to at least a portion of the overburden, and wherein the heat transfer fluid flows through the annular region between the first conduit and the second conduit adjacent to at least a portion of a treatment area. 
     
     
         787 . The system of  claim 784 , wherein the at least one fluid circulation system comprises a first fluid circulation system near a first side of a treatment area and a second fluid circulation system near a second side of the treatment area, and wherein the first circulation system provides the heat transfer fluid to entrances of a first set of heaters, and wherein the second fluid circulation system receives the heat transfer fluid from exits of the first set of heaters. 
     
     
         788 - 790 . (canceled) 
     
     
         791 . A method of heating a subsurface formation, comprising:
 heating a first heat transfer fluid;   circulating the heated first heat transfer fluid through piping positioned in at least two of a plurality of wellbores using a fluid circulation system, wherein the plurality of wellbores are positioned in a formation;   heating at least a portion of a formation to a first temperature;   heating a second heat transfer fluid;   replacing the first heat transfer fluid positioned in the wellbores with the second heat transfer fluid; and   heating the portion of the formation to a second temperature, wherein the second temperature is higher than the first temperature.   
     
     
         792 . (canceled) 
     
     
         793 . (canceled) 
     
     
         794 . The method of  claim 791 , wherein the first heat transfer fluid and/or the second heat transfer fluid comprise molten salts. 
     
     
         795 . (canceled) 
     
     
         796 . (canceled) 
     
     
         797 . A method of heating a subsurface formation, comprising:
 circulating a first heat transfer fluid through piping positioned in at least two of a plurality of wellbores using a fluid circulation system, wherein the plurality of wellbores are positioned in a formation;   heating at least a portion of the first heat transfer fluid;   adding one or more salts to the heated portion of the first heat transfer fluid to form a heated salt solution comprising the first heat transfer fluid and the one or more salts;   heating at least a portion of a formation to a first temperature with the heated salt solution;   removing at least a portion of the first heat transfer fluid to form a second heat transfer fluid; and   heating the portion of the formation to a second temperature with the second heat transfer fluid, wherein the second temperature is higher than the first temperature.   
     
     
         798 . The method of  claim 797 , wherein the one or more salts comprise one or more metals from Column 1 of the Periodic Table. 
     
     
         799 . The method of  claim 797 , wherein the second heat transfer fluid is a molten salt. 
     
     
         800 . (canceled) 
     
     
         801 . (canceled) 
     
     
         802 . The method of  claim 797 , further comprising cooling the second heat transfer fluid after heating the formation and adding a third heat transfer fluid to make another salt solution. 
     
     
         803 . (canceled) 
     
     
         804 . A system for heating a subsurface formation, comprising:
 at least one fluid circulation system configured to provide a heat transfer fluid to a plurality of heaters in the formation; and   a plurality of heaters in the formation coupled to the circulation system, wherein at least one of the heaters comprises:
 a first conduit; 
 a second conduit positioned in the first conduit; and 
 a first flow switcher configured to allow fluid flowing through the second conduit to flow through the annular region between the first conduit and the second conduit; and 
 wherein at least a portion of the first conduit is configured to be resistively heated when electrical current is applied to the portion of the first conduit, and wherein the resistive heat is configured to heat the heat transfer fluid to maintain flow of the heat transfer fluid in the heater. 
   
     
     
         805 . The system of  claim 804 , wherein the portion of the first conduit configured to be resistively heated comprises an overburden portion positioned in the overburden. 
     
     
         806 . A system for heating a subsurface formation, comprising:
 at least one fluid circulation system configured to provide a heat transfer fluid to a plurality of heaters in the formation; and   a plurality of heaters in the formation coupled to the circulation system, wherein at least one of the heaters comprises:
 a first conduit; 
 a second conduit positioned in the first conduit; and 
 a first flow switcher configured to change the flow of the heat transfer fluid flowing through the second conduit to an annular region between the first conduit and the second conduit; and 
   wherein at least a portion of the second conduit is configured to be resistively heated when electrical current is applied to the portion, and wherein the resistive heat is configured to heat the heat transfer fluid to maintain flow of the heat transfer fluid in the heater.   
     
     
         807 . The system of  claim 806 , wherein the portion of the second conduit configured to be resistively heated comprises an overburden portion positioned in the overburden. 
     
     
         808 - 1180 . (canceled)