TECHNOLOGY FOCUS - CHEMICAL ENGINEERING - Preferred Method: The superposition of heat from the heat sources (801) pyrolyzes some hydrocarbons within the selected section of the formation. The pressure and temperature are controlled within a majority of the selected section of the formation, in which the pressure controlled as a function of temperature, or the temperature is controlled as a function of pressure. The heat is controlled so that the an average heating rate of the selected section is less than 1degreesC per day during pyrolysis.The provision of heat to the portion of the formation is carried out by heating a selected volume of the hydrocarbon containing formation from the heat source. The heating rate is less than 10degreesC/day. The heat is transferred via conduction. The selected section is heated such that a thermal conductivity of a portion of the selected section is greater than 0.5 W/(mdegreesC). The controlled pressure is at 2 bar absolute. By controlling formation conditions, a partial pressure of hydrogen (H2) within the mixture at greater than 0.5 bar is obtained. The partial pressure of H2 is measured when the mixture is at a production well (825). The formation conditions are controlled by recirculating a portion of hydrogen from the mixture into the formation. The pressure within the formation is altered to inhibit production of hydrocarbons from the formation having carbon numbers greater than 25.A H2 is provided to the heated section to hydrogenate hydrocarbons within the section, and a portion of the section is heated with the heat from hydrogenation. The heat is allowed to transfer by increasing the permeability of the majority of the selected section to greater than 100 millidarcy. The heat is controlled to yield greater than 60 wt.% condensable hydrocarbons, as measured by the Fischer Assay. The produced mixture is separated into gas and liquid streams. The liquid stream is separated into an aqueous stream (811) and a non-aqueous stream. The produced mixture comprises hydrogen sulfide (H2S) and carbon dioxide (CO2). A portion of the H2S and CO2 are separated from the non-condensable hydrocarbons.Since the mixture is produced from a production well, the wellbore of the production well is heated to inhibit condensation of the mixture within the wellbore. The pyrolysis is carried out at 270degreesC. The pressure is maintained within the formation at 2 bar absolute to inhibit production of fluids having carbon numbers above 25. The pressure is also controlled at atmospheric pressure to 100 bar, as measured at a wellhead of a production well, to control an amount of condensable hydrocarbons within produced mixture and to control the API gravity of condensable hydrocarbons within the produced mixture. The pressure is reduced to increase production of condensable hydrocarbons. The pressure is increased to increase production of non-condensable hydrocarbons.The formation has an average heat capacity (Cv) and heating energy/day provided to the volume is upto Pwr being calculated by the equation (Pwr=hasteriskVasteriskCvasteriskrhoB) and is the heating energy/day, h is an average heating rate of the formation and rhoB is the formation bulk density.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Product: The produced mixture is condensable. The condensable hydrocarbons include 0.1-15 wt.% olefins, less than 1 wt.% nitrogen, less than 1 wt.% oxygen, less than 1 wt.% sulfur, 5-30 wt.% oxygen-containing compounds (phenols), greater than 20 wt.% aromatic compounds, or less than 5 wt.% multi-ring aromatics with more than two rings, 5-30 wt.% cycloalkenes. The produced mixture has an API gravity of at least 25degrees. The produced mixture also includes non-condensable hydrocarbons, in which the molar ratio of ethene to ethane is 0.001-0.15. The non-condensable hydrocarbons include 0.1-15 wt.% olefins. The produced mixture comprises a non-condensable component containing greater than 10-80 vol.% hydrogen.    TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Products: The produced mixture also includes greater than 0.05 wt.% ammonia useful for producing fertilizer.    TECHNOLOGY FOCUS - MECHANICAL ENGINEERING - Preferred Apparatus: The heat sources are electrical heaters (803), surface burners, flameless distributed combustors, natural distributed combustors. A valve is coupled to the heat sources or to a production well located in the formation. The wellbore includes heating elements. The conduit comprises critical flow orifices configured to control the flow of the oxidizing fluid. The system also includes an insulated conductor and an elongated component in the opening, a heat exchanger for heating the oxidizing fluid and an overburden casing coupled to the opening. A packing material is at a junction of the overburden casing and the opening.    TECHNOLOGY FOCUS - METALLURGY - Preferred Materials: The overburden casing is made of stainless steel.    TECHNOLOGY FOCUS - CERAMICS AND GLASS - Preferred Materials: The packing material is made of cement material.