REACTION AND DISSEMINATION: TWO KEY FACTORS IN THE IN SITU COMBUSTION TECHNIQUE

Currently, around the world, 64% of the reserves are composed of heavy oil, which is not easily extracted by conventional methods. In order to exploit these deposits, some techniques have been developed for enhanced oil recovery, all of them with different mechanisms of displacement. Fluids drive miscible and immiscible, viscosity reduction by temperature rise, reduction of surface tension by chemical methods, etc. Among these techniques it may be found the in-situ combustion (ISC), which is known as a thermal method since it is based on energy transfer in the form of heat in order to decrease the viscosity and density of the heavy oil to be extracted from the reservoir. ISC is a complex technique because it has several physical and chemical mechanisms of displacement. This Technique occurs in five steps: dispersion of air at the surface, adsorption of oxygen in the media, chemical reactions, desorption of the combustion gases and finally, diffusion of these gases to the surface. The overall process speed is controlled by the step that occurs more slowly, which is usually the chemical kinetics or the dispersion. In this paper it is studied the two principal aspects separately, beginning with a review of the reactions that occur in this process. Also it is presented the most important chemical transformations of each temperature regime (low, intermediate and high) as well as the kinetics and thermodynamics of the reactions, which introduces the subject of phase equilibrium for the technique. On the other hand, it is made a review of the different types of dispersion that exist in the reservoir and the factors which affect this process, considering that it is mass transfer phenomena taking in a porous medium, thus generating the necessity for new correlations that include correction factors with the main goal of representing the displacement phenomena by mathematical expressions.