Geothermal energy recovery

Abstract

Apparatus and method for recovering resources from subterranean rock formations, particularly heat energy, and more particularly geothermal energy. A heat-drill, which has means associated therewith for removing some rock from the earth and forming other rock into shafts, drills into the earth and forms two shafts at the same time. Both shafts communicate with each other and with the surface and are used to circulate a drilling mud which passes through the drill body and carries off the rock being removed. The heating means is shaped in a coil or grid pattern and operates at a temperature well above the melting point of the rock, heating the rock it displaces to well above its melting point, while raising the average temperature of the total rock melted to slightly above its melting point. The drilling mud absorbs heat as it circulates and the absorbed heat is put to any desirable use, particularly by being recovered from the drilling mud by a heat-exchanger on the surface. The drill has means associated therewith for automatically controlling its rate of advance into the earth and its general downward direction. The drill has means associated therewith for preparing the shafts, particularly the downflow shaft, for a particular type of fracturing of the surrounding rock formations to facilitate the collection of heat therefrom. Later heat recovery is facilitated by forming convection cells within the factures which encourage circulation of fluids at a distance from the shafts.t