| 摘要 |
A system for heating a subsurface formation includes a heater wellbore located in a subsurface formation. A single conducting heater element includes a heated portion located in a part of the subsurface formation configured to be heated and a lead-in portion located in an overburden of the subsurface formation. The heated part is located below the overburden. A heater casing is located substantially in an overburden portion of the heater wellbore. The heater casing includes an electrically non-conducting portion and an electrically conducting portion. The non-conducting portion begins at the surface of the formation. The conducting portion is located between the non-conducting portion and the heated portion of the heater. The non-conducting portion extends to a depth that is at least about 30 m above the heated portion of the heater.
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