Abstract: Disclosed is a chemical system of gas evolving oil viscosity diminishing compositions (GEOVDC) for stimulating the productive layer of an oil reservoir, that is to chemical compositions for a thermochemical treatment of an oil reservoir, more specifically for initiating a chemical reaction in the productive layer zone of the oil reservoir to produce heat and evolve gases so that the extraction of oil (petroleum) is improved. Further disclosed is a method of thermochemically treating an oil reservoir by means of this chemical system, and an apparatus for performing thermochemical treatment of an oil reservoir.

Abstract: It is provided a method and an apparatus for continuously thermally treating an oil reservoir, in particular a method and an apparatus for thermally treating an oil reservoir by separately introducing a first and a second composition into an oil well and contacting the first and second compositions in a pay zone of the oil reservoir to initiate a chemical reaction producing heat and gases. With the method and apparatus according to the present invention it becomes possible to simultaneously introduce the compositions into the oil well and to extract the resultant oil or oil containing mixture through the same oil well.