A hydrocarbon bearing formation (304) which is heated using a variable frequency capacitive radio frequency dielectric heating (334) in situ process. Hydrocarbons or other substances natural to a hydrocarbonaceous formation may be produced by heating specific chemical compositions with or without the use of a carrier medium (320) in a subterranean reservoir. Hydrocarbons or other substances natural to a hydrocarbonaceous formation are heated by maintaining specific chemical compositions in an alternating current electrical field generated by a radio frequency signal. As the targeted chemical compositions increase in temperature, maximum energy is delivered using variable frequency radio frequency dielectric heating to adjust the rate of the heating process.