An apparatus for the in situ extraction of bitumen or very heavy oil from oil sand deposits, and applying heat energy to the deposit to reduce the viscosity of the bitumen is provided. A high-frequency generator feeds electric power to a linearly extended conductor loop at a predefined depth of an oil sand deposit, the inductance of the conductor loop is compensated in some sections or continuously. Advantageously, one of the conductors of the conductor loop may be disposed substantially in a vertical direction above the extraction pipe.