TECHNOLOGY FOCUS - CHEMICAL ENGINEERING - Preferred Method: Formation conditions are controlled by maintaining a temperature within the selected section within a pyrolysis temperature range. The method also includes controlling a pressure and a temperature within the selected section of the formation, wherein the pressure is controlled as a function of temperature or the temperature is controlled as a function of pressure. Providing heat from the heat source to at least portion of the formation comprises heating a selected volume (V) of the hydrocarbon containing formation from the heat source. The formation has an average heat capacity (Cv). The heating pyrolyzes at least some hydrocarbons within the selected volume of the formation. The heating energy/day provided to the volume is equal to or less than Pwr, where Pwr is calculated by the equation: Pwr = h x V x Cv x rhoB. Pwr is the heating energy/day, h is an average heating rate of the formation, rhoB is formation bulk density, and heating rate is less than 10degreesC/day. The partial pressure of hydrogen (H2) is measured when the mixture is at a production well. Controlling formation conditions comprises recirculating a portion of H2 from the mixture into the formation. Altering a pressure within the formation to inhibit production of hydrocarbons from the formation having greater than 25 carbons. H2 is provided to the heated section to hydrogenate hydrocarbons within the section. A portion of the section is heated with heat from hydrogenation. A portion of the hydrogen sulfide (H2S) is separated from non-condensable hydrocarbons. A wellbore is heated to inhibit condensation of the mixture within the wellbore.Preferred Condition: The heat is controlled such that an average heating rate of the selected section is less than 1degreesC/day during pyrolysis. The selected section is heated such that a thermal conductivity of at least a portion of the selected section is greater than 0.5 W/(m-degreesC). The portion of the formation extends radially from the opening a width of less than approximately 0.2 m. A pressure is controlled at 2 bar absolute within at least a majority of the selected section of the formation. Formation conditions are controlled such that the produced mixture comprises a partial pressure of H2 within the mixture of greater than 0.5 bar. The heat is controlled to yield greater than 60 wt.% of condensable hydrocarbons, as measured by the Fischer Assay. The produced mixture is separated into a gas stream and a liquid stream, and the liquid stream is separated into an aqueous stream and a non-aqueous stream. The heating is controlled such that the mixture can be produced from the formation as a vapor. The minimum pyrolysis is at 270degreesC. Controlling pressure within the formation from an atmospheric pressure to 100 bar, as measured at a wellhead of a production well, to control an API gravity of condensable hydrocarbons within the produced mixture, the pressure is reduced to decrease the API gravity, and the pressure is increased to reduce the API gravity. The synthesis gas generation is at approximately 400 - approximately 1200degreesC.Preferred Property: The produced mixture comprises condensable hydrocarbons having an API gravity of at least 25degreesC. Allowing the heat to transfer comprises increasing a permeability of a majority of the selected section to greater than 100 millidarcy.    TECHNOLOGY FOCUS - MECHANICAL ENGINEERING - Preferred Component: The heat source is electrical heaters, surface burners, flameless distributed combustors, or natural distilled combustors. The pressure is controlled with a valve coupled to the heat source or a production well located in the formation.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Composition: The produced mixture comprises 0.1-15 wt.% condensable hydrocarbons from olefins, non-condensable hydrocarbons, and a molar ratio of ethene to ethane in the non-condensable hydrocarbons of 0.001-0.15. 5-30 wt.% of the condensable hydrocarbons comprise oxygen containing compounds comprising phenols. Greater than 20 wt.% of the condensable hydrocarbons are aromatic compounds. Less than 5 wt.% of the condensable hydrocarbons comprise multi-ring aromatics with more than two rings. Less than 0.3 wt.% of the condensable hydrocarbons are asphaltenes. 5-30 wt.% of the condensable hydrocarbons are cycloalkanes.    TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Component: Less than 1 wt.%, when calculated on an atomic basis, of the condensable hydrocarbons is nitrogen, oxygen, or sulfur. The non-condensable hydrocarbons comprise greater than 10 or less than 80 vol.% of H2. The produced mixture comprises greater than 0.05 wt.% of ammonia used to produce fertilizer, and carbon dioxide (CO2).