A device for extracting crude oil out of an extraction bore of a previously tapped deposit, comprises, a combustion chamber having at least one reaction chamber portion and an evaporation chamber portion arranged in axial relationship with a constricted nozzle portion therebetween. Advantageously, an additional constricted nozzle portion separates a turbulence chamber from a front reaction chamber and the second constriction separates the front reaction chamber from a rear evaporation chamber. The evaporation chamber in turn feeds through a nozzle section to a narrow discharge into the extraction bore. A fuel and chemical oxygen or an oxygen carrier are directed into the combustion chamber preferably in front of the first constriction and forms high temperature combustion gases into which the water is directed in a manner to intermix the water with the combustion gases and to form superheated steam which is then discharged into the extraction bore. The steam causes the oil in the previously tapped deposit to become less viscous and to flow out of the extraction bore.