A technique is provided for extracting a substance containing hydrocarbon from a reservoir, wherein the reservoir is applied with thermal energy in order to reduce the viscosity of the substance. As per the technique, at least two conductor loops for the inductive energization are provided as electric/electromagnetic heating elements. Each of the at least two conductor loops has at least two extended conductors, which are guided horizontally inside the reservoir. At least two alternating current generators are provided for electric power, each being connected to a respective conductor loop. The technique involves operating a first of the at least two alternating current generators and at least a second of the at least two alternating current generators synchronously with respect to their frequency and with a fixed phase position in relation to one another.