The extraction of hydrocarbon fuel products such as kerogen oil and gas from a body of fixed fossil fuels such as oil shale is accomplished by applying a combination of electrical energy and critical fluids with reactants and/or catalysts down a borehole to initiate a reaction of reactants in the critical fluids with kerogen in the oil shale thereby raising the temperatures to cause kerogen oil and gas products to be extracted as a vapor, liquid or dissolved in the critical fluids. The hydrocarbon fuel products of kerogen oil or shale oil and hydrocarbon gas are removed to the ground surface by a product return line. An RF generator provides electromagnetic energy, and the critical fluids include a combination of carbon dioxide (CO.sub.2), with reactants of nitrous oxide (N.sub.2O) or oxygen (O.sub.2).