Oxidation and heat exchange processes in oil reservoir

Two things occur during in situ combustion underground (a) oxidation of some of the substances, and (b) thermal treatment of the oil-bearing bed by heat released during this oxidation process. The movement of substances in the zone that has been heated and ahead of it can be described by using equations for filtration of multiphase fluids. 

Gottfried [31] calculated the solution for the system of equations. Of course, this mathematic description of the underground in situ combustion is not complete. Additional equations should be applied based on such things as the theory of combustion, theory of heat transfer [34], equations for mass exchange by convection, and the theory of dissociation. 

However, even with help of modem computers it would be difficult to obtain solutions for systems of all these equations. For practical calculations, it is therefore advantageous to use simplified scheme to represent processes of oxidation as well as heat- and mass-transfer. 

In situ burning of oil in oxygen injected with the air into the bed is always preceded by its slow oxidation. Depending on the properties of petroleum present in the bed, its oxidation can begin at different temperatures. 

The rate of oxidation reaction under specific reservoir conditions is not stable. Average rate of reaction is generally determined by the ratio of difference between the final concentration of products (C2) and the original concentration of products (Ci). This change is measured during the time interval (ti, T2) in which this reaction was taking place, that is  

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