A method and apparatus are shown for burning crude oil or natural gas extracted from an underground reservoir, or for burning both crude oil and natural gas extracted from an underground reservoir, for providing thermal energy. The method and apparatus are also shown transferring the thermal energy to brine separated from the extracted oil, gas or both, for providing heated brine, or for converting the thermal energy to mechanical work, or for both transferring the thermal energy to the separated brine and converting the thermal energy to mechanical work. The method and apparatus are also shown heating the underground reservoir with the heated brine injected into the underground reservoir, or heating the underground reservoir with a resistive cable energized by electricity generated by converting the mechanical work to electric energy, or heating the underground reservoir with both the heated brine and the energized resistive cable.