TECHNOLOGY FOCUS - CHEMICAL ENGINEERING - Preferred Method: The superposition of heat from at least two heat sources pyrolyzes at least some hydrocarbons within the selected section of the formation. Controlling formation conditions comprises maintaining a temperature within the selected section within a pyrolysis temperature range. The minimum pyrolysis temperature is 270degreesC. The pressure within at least a majority of the selected section of the formation is controlled with a valve coupled to the heat sources or to a production well located in the formation. The controlled pressure is at least 2.0 bar absolute. The heat is controlled so that an average heating rate of the selected section is less than 1degreesC per day during pyrolysis.Providing heat from the heat sources to at least the portion of formation comprises heating a selected volume (V) of hydrocarbon-containing formation from the heat sources. The formation has an average heat capacity (Cv). Heating energy/day (Pwr) provided to the volume is calculated by the equation: Pwr = hasteriskVasteriskCvasteriskrho-B, where h is an average heating rate of the formation, rho-B is formation bulk density, and the heating rate is less than 10degreesC/day. The heat is allowed to transfer from the heat sources to the selected section by conduction. A partial pressure of hydrogen gas (H2) in the produced mixture is greater than 0.5 bar. A portion of hydrogen from the mixture is recirculated into the formation. A pressure within the formation is altered to inhibit production of greater than 25C hydrocarbons.Allowing the heat to transfer comprises increasing a permeability of a majority of the selected section to greater than 100 millidarcy. Heat is controlled to yield greater than 60 wt.% condensable hydrocarbons, as measured by the Fischer Assay. The mixture produced in the production well is separated into a gas stream and a liquid stream. The liquid stream is separated into an aqueous stream and a non-aqueous stream. Portions of hydrogen sulfide (H2S) and carbon dioxide (CO2) are separated from non-condensable hydrocarbons.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The produced mixture comprises condensable hydrocarbons having an API gravity of at least 25degrees; non-condensable hydrocarbons; and greater than 0.05 wt.% ammonia. The non-condensable hydrocarbons comprise 0.1-15 wt.% olefins; and greater than 10 - less than 80 vol.% hydrogen. The molar ratio of ethene to ethane in the non-condensable hydrocarbons is 0.001-0.15. The condensable hydrocarbons comprise 0.1-15 wt.% olefins; less than 1 wt.% nitrogen; less than 1 wt.% oxygen; 5-30 wt.% oxygen-containing compounds comprising phenols; less than 1 wt.% sulfur; greater than 20 wt.% aromatic compounds; less than 5 wt.% multi-ring aromatics with more than 2 rings; less than 0.3 wt.% asphaltenes; and 5-30 wt.% cycloalkanes.    TECHNOLOGY FOCUS - MECHANICAL ENGINEERING - Preferred Components: The heat sources comprise electrical heaters, surface burners, flameless distributed combustors, or natural distributed combustors. The conduit has orifices to provide an oxidizing fluid to a reaction zone in the formation during use. The system is configured to allow heat to transfer by conduction from the reaction zone to a pyrolysis zone of the formation during use. A heat exchanger is positioned external to the formation and is configured to heat the oxidizing fluid. An overburden casing is coupled to the opening and is positioned in an overburden of the formation. It is further positioned in cement.    TECHNOLOGY FOCUS - METALLURGY - Preferred Material: The overburden casing comprises steel.