In situ conversion process systems utilizing wellbores in at least two regions of a formation

A system for heating a subsurface formation, comprising:

• a plurality of first elongated heaters located in a plurality of first openings in the formation, at least two of the first heaters being substantially parallel to each other for at least a portion of the lengths of the heaters;
• a plurality of second elongated heaters located in a plurality of second openings in the formation, at least two of the second heaters being substantially parallel to each other for at least a portion of the lengths of the heaters;
• at least two of the first heaters and at least two of the second heaters having first end portions in a first region of the formation and second end portions in a second region of the formation;
• and
• a source of time-varying current configured to apply time-varying current to at least two of the heaters;
• wherein a first voltage is applied to the first end portions of the first heaters during use that is opposite in polarity to a second voltage applied to the first end portions of the second heaters during use;
• and
• the second voltage is applied to the second end portions of the first heaters during use.

A system for heating a hydrocarbon containing formation, comprising:

• an opening in the formation, the opening having a first end portion at a first location on the surface of the formation and a second end portion at a second location on the surface of the formation;
• a heater in the opening, the heater having a first end portion at the first location on the surface of the formation and a second end portion at the second location on the surface of the formation;
• wherein the heater includes insulated electrical conductors positioned in the portions of the opening in the overburden of the formation at both the first and second end portions of the heater, the insulated electrical conductors including copper;
• the heater has a temperature limited heater section positioned in a portion of the opening in a hydrocarbon layer of the formation;
• the heater has a transition section coupled between the insulated electrical conductors and the temperature limited heater section;
• and
• the heater is configured to provide heat to a portion of the formation.

A system for heating a subsurface formation, comprising:

• a plurality of elongated heaters located in a plurality of openings in the formation, at least two of the heaters being substantially parallel to each other for at least a portion of the lengths of the heaters;
• at least two of the heaters having first end portions in a first region of the formation and second end portions in a second region of the formation;
• and
• a source of time-varying current configured to apply time-varying current to at least two of the heaters, wherein the first end portions of at least two heaters are configured to have substantially the same voltage applied to them, and the second end portions of at least two heaters are configured to have substantially the same voltage applied to them;
• wherein the first end portions of the heaters are configured to be applied with a first voltage and the second end portions of the heaters are configured to be applied with a second voltage, and wherein the first voltage is, at a selected point in time on the voltage versus time wave of the first voltage, opposite in polarity to the second voltage at the selected point in time on the voltage versus time wave of the second voltage.

A system for heating a subsurface formation, comprising:

• a plurality of elongated heaters located in a plurality of openings in the formation, at least two of the heaters being substantially parallel to each other for at least a portion of the lengths of the heaters;
• at least two of the heaters having first end portions in a first region of the formation and second end portions in a second region of the formation;
• and
• a source of time-varying current configured to apply time-varying current to at least two of the heaters, wherein the first end portions of at least two heaters are configured to have substantially the same voltage applied to them, and the second end portions of at least two heaters are configured to have substantially the same voltage applied to them;
• wherein the first end portions of the heaters are configured to be applied with a first voltage and the second end portions of the heaters are configured to be applied with a second voltage, wherein the first voltage is equal in magnitude and opposite in polarity to the second voltage, with an average voltage that is substantially at ground potential.

A system for heating a subsurface formation, comprising:

• a plurality of elongated heaters located in a plurality of openings in the formation, at least two of the heaters being substantially parallel to each other for at least a portion of the lengths of the heaters, wherein at least one opening comprises a substantially u-shaped opening;
• at least two of the heaters having first end portions in a first region of the formation and second end portions in a second region of the formation;
• and
• a source of time-varying current configured to apply time-varying current to at least two of the heaters, wherein the first end portions of at least two heaters are configured to have substantially the same voltage applied to them, the second end portions of at least two heaters are configured to have substantially the same voltage applied to them, and the voltage configured to be applied to the first end portions of the heaters is substantially equal in magnitude to the voltage configured to be applied to the second end portions of the heaters.

A system for heating a subsurface formation, comprising:

• a plurality of elongated heaters located in a plurality of openings in the formation, at least two of the heaters being substantially parallel to each other for at least a portion of the lengths of the heaters, wherein at least one opening comprises a substantially u-shaped opening;
• at least two of the heaters having first end portions in a first region of the formation and second end portions in a second region of the formation;
• and
• a source of time-varying current configured to apply time-varying current to at least two of the heaters, wherein the first end portions of at least two heaters are configured to have substantially the same voltage applied to them, and the second end portions of at least two heaters are configured to have substantially the same voltage applied to them;
• wherein at least one elongated heater comprises a temperature limited heater, the temperature limited heater comprising a ferromagnetic conductor and being configured to provide, when a time varying current is applied to the temperature limited heater, and when the heater is below a selected temperature, an electrical resistance and, when the ferromagnetic conductor is at or above the selected temperature, the temperature limited heater automatically provides a reduced electrical resistance.