TECHNOLOGY FOCUS - CHEMICAL ENGINEERING - Preferred Method: Superposition of heat pyrolyzes at least some hydrocarbons within the selected section (805, 819) of the formation. The formation conditions are controlled by maintaining the selected section within a pyrolysis temperature range or recirculating a portion of hydrogen from the mixture into the formation. They are controlled to produce a mixture comprising a partial pressure of hydrogen of greater than 0.5 bar which is measured when the mixture is at a production well (825). The pressure and temperature are controlled as a function of temperature or pressure, respectively. The heat is controlled so that an average heating rate of the selected section is less than 1degreesC/day during pyrolysis, and to yield more than 60 wt.% of condensable hydrocarbons, as measured by the Fischer Assay. It is provided to at least the portion of the formation by heating a selected volume (V) of the formation from the heat sources so that thermal conductivity of at least a portion of the selected section is greater than 0.5 W/(mdegreesC), where the formation has an average heat capacity (Cv), and heating energy/day provided to the volume is equal to or less than Pwr. Pwr is calculated by the equation Pwr = HasteriskVasteriskCvasteriskrho-B, where Pwr is the heating energy/day, 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 transferred by conduction or by increasing a permeability of a majority of the selected section to more than 100 millidarcy. The controlled pressure is at least 2 bar absolute and at an equation pbar is greater than e-((-A/T)-B-26744), where p is more than 1.4 bar, T is less than 390degreesC, A is greater than 14000 or less than 57000, and B is greater than 25 or less than 83 and a majority of the pyrolyzed hydrocarbon fluids (807) have an average carbon number of lower than 25 (preferably lower than 21) and comprise less than 10 wt.% olefins. The pressure can be altered in the formation to inhibit production of hydrocarbons having carbon numbers greater than 25. At least 7 heat sources are disposed in the formation for each production well. Three or more heat sources are located in the formation in a unit of heat sources comprising triangular pattern. The produced mixture is separated into a gas stream (813) and a liquid stream (815) which is also separated into an aqueous (811) and non-aqueous streams. The minimum pyrolysis temperature is at 270degreesC. The formation is controlled at 100 bar, as measured at a wellhead of the production well, to control an amount and API gravity of condensable hydrocarbons. The API gravity of the mixture is controlled to be more than 25degrees, 30degrees, or 35degrees API by controlling average pressure and temperature in the selected section so that the average pressure in the selected section is more than the pressure (p) of the equation p = e-(-44000/T+67), p = e-(-31000/T+51, or p = e-(-22000/T+38) where p is measured in psi and T is measured in degreesK. A weight percentage of olefins of the mixture is controlled to be less than 20 wt.%, 10 wt.% or 5 wt.% using an equation p = e-(-57000/T+83), p = e(-16000/T+28), or p = e(-12000/T+22), respectively. The hydrocarbons are controlled to be less than 25 wt.%, less than 20 wt.%, or less than 15 wt.% using an equation p = e-(-14000/T+25), p = e-(-16000/T+28), or p = e-(-18000/T+32), respectively. An atomic hydrogen to carbon ratio is controlled to be greater than 1.7, greater than 1.8, greater than 1.9 using an equation p = e-(-38000/T+61), p = e-(-13000/T+24), or p = e-(-8000/T+18), respectively. The portion of the formation is heated by raising the temperature of the portion above 400degreesC. An oxidant is reacted with the hydrocarbons to produce heat in a heat source zone. Excess oxidant is removed from the heat source zone to inhibit transport of the oxidant to the pyrolysis zone. The amount of oxidant is limited to maintain the heat source zone at less than 1200degreesC. The vaporization temperature is less than approximately 450degreesC at atmospheric pressure. An electrical current is applied to an insulated conductor to provide heat. The synthesis gas (823) is generated at approximately 400 to approximately 1200degreesC.    TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Component: The oxidant comprises hydrogen peroxide or air. It comprises fluid free of nitrogen. The electrically insulating material is aluminum oxide and magnesium oxide having a thickness of at least approximately 1 mm.    TECHNOLOGY FOCUS - METALLURGY - Preferred Component: The conductor comprises a copper-nickel alloy comprising approximately 2- approximately 6 wt.% nickel. The conduit comprises stainless steel.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Composition: The produced mixture comprises condensable and non-condensable hydrocarbons, hydrogen sulfide, and carbon dioxide. It comprises more than 0.05 wt.% ammonia used to produced fertilizer. A molar ratio of ethene to ethane in the non-condensable hydrocarbons is 0.001-0.15. The (non)condensable hydrocarbons (0.1-15, preferably 0.1-2 wt.%) are olefins. The condensable hydrocarbons comprise less than 1 wt.% nitrogen, less than 1 wt.% oxygen, 5-30 wt.% oxygen containing compounds comprising phenols, less than 1 wt.% sulfur, more than 20 wt.% aromatic compounds, less than 5 (preferably less than 2) wt.% multi-ring aromatics with more than two rings, less than 0.3 wt.% asphaltenes, and 5-30 wt.% cycloalkanes. The non-condensable component comprises more than 10 vol.% but less than 80 vol.% hydrogen. The condensable mixture comprises more than 25 wt.% oxygenated hydrocarbons. The synthesis gas has a selected composition having a hydrogen to carbon monoxide ratio of 2:1, preferably approximately 2.8:1 to approximately 3.2:1. The feed stream comprises hydrogen and hydrocarbon having a carbon number of less than 5, preferably less than 3.Preferred Property: The produced mixture comprises condensable hydrocarbons having an API gravity of at least 25degrees. The heat is provided at approximately 500- approximately 1150 W/m.    TECHNOLOGY FOCUS - MECHANICAL ENGINEERING - Preferred Component: The heat sources (801) comprise electrical heater (803), surface burners, or flameless distributed combustors. Preferred Property: The distance between heat sources is 2-8 mm.