This paper describes miscible displacement upon air injection in a porous medium saturated with oil corresponding to conditions of high-pressure air injection (HPAI). We assume that injection fluids and produced fluids are fully miscible with the oil at the prevailing high pressure. We use three pseudo-components, viz., oxygen, oil, and an inert component, which includes nitrogen, carbon dioxide, etc. To model the fingering instabilities, we follow a similar procedure as proposed by Koval (SPE J. 3(02):145–154, 1963) and include the reaction between oxygen and oil in the Koval model. The equations are solved numerically, using a finite element software package (COMSOL). The results show that a combustion wave is formed. We study the performance at low and high viscosities and show that the reaction improves the speed and degree of recovery at later times. ... Read more