A method for extracting energy from hydrocarbons located in a geologic reservoir is presented, including the steps of: oxidizing the hydrocarbons; extracting heat generated from oxidizing the hydrocarbons, relocating oxidized gases away from the oxidizing hydrocarbons; and replenishing oxygen towards the oxidizing hydrocarbons. The extraction of heat further includes: evaporating a liquid; transferring the evaporated liquid to the surface; and recovering low-NaCl, low-precipitate water from the evaporated liquid. The replenishing of oxygen towards the oxidizing hydrocarbons further includes: generating oxygen from water; and transferring the generated oxygen toward the oxidizing hydrocarbons; and combining hydrogen derived from the generating step with surface oxygen, whereby heat and low-precipitate, pure water is produced.