Impact of Distillation on the Combustion Kinetics of High Pressure Air Injection (HPAI)

Abstract

Abstract During the last two decades HPAI (High Pressure Air Injection) has proven to be a successful recovery method in deep light oil reservoirs. Distillation, flue gas drive and thermal front effects are the most dominant mechanisms associated with oil recovery in HPAI processes. This paper describes the results and observations of an experimental study conducted to characterize distillation, not only as a recovery mechanism but moreover as a phenomenon that impacts the kinetics of light oil combustion in HPAI. Distillation or vaporization-condensation of light fractions of oil in thermal processes, more frequently in steam flooding and in-situ combustion, has been studied since its first recognition in 1960. Compositional effect of distillation on phase behavior of light oils, through stripping, and displacement of light ends through vaporization-condensation has been recognized as important. However, certain aspects of distillation such as the latent heat associated with vaporization of hydrocarbons, type of residual fuel remaining in the liquid phase after progression of an evaporation front, and more importantly the type of fuel transferred to the vapor phase through vaporization, all of which impact the kinetics of light oil combustion, has been missing in HPAI studies. This study aims to shed light on the impact of distillation on formation and progression of the thermal front and reaction kinetics associated with the vapor phase oxidation/combustion. For the purpose of this study, oxygen and nitrogen injection experiments were performed on a recombined light oil core sample in a 45cm long, ramped temperature oxidation (RTO) reactor. This paper concentrates on selected tests which highlight the distillation behavior. The presence of an endothermic vaporization front accompanying the exothermic thermal front in the RTO experiments was observed in this research. The nature of the thermal front depends on whether the concentration of hydrocarbon in the vapor phase falls in the flammable range.