High voltage temperature limited heaters

Abstract

A heater system may include an alternating current supply and an electrical conductor. An alternating current may be applied to one or more electrical conductors at a voltage above about 200 volts. The electrical conductors may be located in a formation. The electrical conductors may provide an electrically resistive heat output upon application of the alternating electrical current. At least one of the electrical conductors may include an electrically resistive ferromagnetic material. An electrical conductor may provide a reduced amount of heat above or near a selected temperature. Heat may be allowed to transfer from an electrical conductor to a part of the formation.

1 - 154 . (canceled) 
     
     
         155 . A method for treating a hydrocarbon containing formation, comprising:
 providing heat from one or more heaters to at least a portion of the formation, wherein at least one of the heaters is in at least one of one or more wellbores in the formation, and wherein heating from one or more of the heaters is controlled to inhibit substantial deformation of one or more of the heaters caused by thermal expansion of the formation against such one or more heaters;   allowing the heat to transfer from the one or more heaters to a part of the formation; and   producing a mixture from the formation.   
     
     
         156 . The method of  claim 155 , wherein at least one of the wellbores comprises an uncased wellbore. 
     
     
         157 . The method of  claim 155 , further comprising controlling the heating to maintain a minimum space between at least one of the heaters and the formation in at least one of the wellbores. 
     
     
         158 . The method of  claim 155 , further comprising controlling the heating using a temperature limited heater. 
     
     
         159 . The method of  claim 155 , further comprising controlling the heating to maintain a minimum space of at least about 0.25 cm between at least one of the heaters and the formation in at least one of the wellbores. 
     
     
         160 . The method of  claim 155 , wherein at least one of the heaters is in at least one of the wellbores having a diameter sufficient to inhibit the formation from expanding against such heater during heating of the formation. 
     
     
         161 . The method of  claim 160 , wherein the diameter of at least one of the wellbores having a diameter sufficient to inhibit the formation from expanding against such heater during the heating of the formation is greater than or equal to about 30 cm. 
     
     
         162 . The method of  claim 155 , wherein one or more of the wellbores have an expanded diameter proximate to relatively rich zones in the formation. 
     
     
         163 . The method of  claim 162 , wherein the expanded diameter is greater than or equal to about 30 cm. 
     
     
         164 . The method of  claim 162 , wherein the relatively rich zones comprise a richness greater than about 0.15 L/kg. 
     
     
         165 . The method of  claim 162 , wherein the relatively rich zones comprise a richness greater than about 0.17 L/kg. 
     
     
         166 . The method of  claim 155 , wherein controlling the heating comprises adjusting a heat output of at least one of the heaters such that the heat output provided to relatively rich zones of the formation is less than the heat output provided to other zones of the formation. 
     
     
         167 . The method of  claim 155 , wherein controlling the heating comprises adjusting a heat output of at least one of the heaters such that about the heat output provided to relatively rich zones of the formation is less than about ½ the heat output provided to other zones of the formation. 
     
     
         168 . The method of  claim 167 , wherein the relatively rich zones comprise a richness greater than about 0.15 L/kg. 
     
     
         169 . The method of  claim 155 , further comprising reaming at least one of the wellbores after at least some heating of the formation from such wellbores. 
     
     
         170 . The method of  claim 155 , further comprising reaming at least one of the wellbores after at least some heating of the formation from such wellbores, and wherein the reaming is conducted to remove at least some hydrocarbon material that has expanded in such wellbores. 
     
     
         171 . The method of  claim 155 , further comprising removing at least one of the heaters from at least one of the wellbores, and then reaming at least one such wellbore. 
     
     
         172 . The method of  claim 155 , further comprising perforating one or more relatively rich zones in at least part of the formation to allow for expansion of at least one or more of the relatively rich zones during heating of the formation. 
     
     
         173 . The method of  claim 155 , further comprising placing a liner in at least one of the wellbores and between at least a part of one of the heaters and the formation, wherein the liner inhibits heater deformation caused by thermal expansion of the formation during heating. 
     
     
         174 . The method of  claim 173 , wherein the liner comprises a mechanical strength sufficient to inhibit collapsing of the liner proximate relatively rich zones of the formation. 
     
     
         175 . The method of  claim 173 , wherein the liner comprises one or more openings to allow fluids to flow through the wellbore in which the liner is placed. 
     
     
         176 . The method of  claim 173 , wherein a ratio of an outside diameter of the liner to the inside diameter of the wellbore in which the liner is placed is less than 0.75. 
     
     
         177 . The method of  claim 173 , wherein a ratio of an outside diameter of the liner to the inside diameter of the wellbore in which the liner is placed is less than 0.5. 
     
     
         178 . The method of  claim 173 , wherein a ratio of an outside diameter of the liner to the inside diameter of the wellbore in which the liner is placed is less than 0.3. 
     
     
         179 . The method of  claim 155 , further comprising maintaining a temperature in at least a portion of the formation in a pyrolysis temperature range with a lower pyrolysis temperature of about 250° C. and an upper pyrolysis temperature of about 400° C. 
     
     
         180 . The method of  claim 155 , further comprising heating at least a part of the formation to substantially pyrolyze at least some hydrocarbons in the formation. 
     
     
         181 . The method of  claim 155 , further comprising controlling a pressure and a temperature in at least a part of the formation, wherein the pressure is controlled as a function of temperature, or the temperature is controlled as a function of pressure. 
     
     
         182 . The method of  claim 155 , wherein allowing the heat to transfer from the one or more heaters to the part of the formation comprises transferring heat substantially by conduction. 
     
     
         183 . The method of  claim 155 , wherein the produced mixture comprises condensable hydrocarbons having an API gravity of at least about 25°. 
     
     
         184 . The method of  claim 155 , further comprising controlling a pressure in at least a majority of a part of the formation, wherein the controlled pressure is at least about 2.0 bars absolute. 
     
     
         185 . The method of  claim 155 , further comprising controlling formation conditions such that the produced mixture comprises a partial pressure of H 2  in the mixture greater than about 0.5 bars. 
     
     
         186 . The method of  claim 155 , wherein the formation comprises an oil shale formation. 
     
     
         187 . The method of  claim 155 , wherein the formation comprises a coal formation. 
     
     
         188 - 1690 . (canceled)