TECHNOLOGY FOCUS - CHEMICAL ENGINEERING - Preferred Process: The heat sources comprise at least two heat sources, and superposition of heat from the heat sources pyrolyzes at least some hydrocarbons within the selected section of formation. The formation conditions are controlled by maintaining temperature of the selected section within pyrolysis temperature range. Further, pressure and temperature are controlled within the selected section of formation, where the pressure is controlled as function of temperature and the temperature is controlled as function of pressure. The pressure is controlled with a valve coupled to at least one of the heat sources or to production well located in the formation. The heating is controlled so that average heating rate of selected section is less than 1 degrees C/day during pyrolysis. Heating at least a portion of formation involves heating a selected volume of formation (V) having average heat capacity of Cv, where the heating pyrolyzes at least some hydrocarbons within the selected volume of formation. Heating energy per day provided to the volume is at most Pwr. Pwr is calculated as, Pwr = h x V x Cv x rhoB, where h is average heating rate of formation (less than 10 degrees C per day) and rhoB is formation bulk density. Preferred Heater: The heat sources comprise electrical heaters, surface burners, flameless distributed combustors or natural distributed combustors. Preferred Compounds: The produced mixture comprises condensable and non-condensable hydrocarbons, where the condensable hydrocarbons have API gravity of at least 25 degrees C. 0.1-15 weight percent of condensable and non-condensable hydrocarbons are olefins. The molar ratio of ethene to ethane in the non-condensable hydrocarbon is 0.001-0.15. Less than 1 wt.% of condensable hydrocarbons is nitrogen, sulfur or oxygen. 5-30 wt.% of condensable hydrocarbon comprise oxygen containing compounds containing phenols. Less than 5 wt.% of condensable hydrocarbons comprise multi-ring aromatics. The non-condensable component comprises 10-80 volume% of hydrogen. The mixture comprises 0.05 wt.% of ammonia used to produce fertilizers.