Analysis of dry, wet and superwet in situ combustion using a novel conical cell experiment

Abstract

A conical combustion cell was built and utilized in combustion experiments at the In Situ Combustion Research Group at the University of Calgary to investigate the effect of continuous in situ air flux drop on the dynamics of the combustion process and to identify the characteristics of the process most importantly the extinction air flux. Nine set of top-down (gravity stable) dry, wet and superwet combustion experiments were conducted at different injection rates in sand packs representing typical Athabasca heavy oil reservoirs. The temperature profiles, the produced combustion gases and liquids as well as the unpacked core were examined. Minimum injected air flux at the termination of the experiments was calculated; gas phase combustion parameters were analyzed. Some of the features specific to combustion experiments in conical cells were investigated.It is believed that the formation of fuel rich condition especially in presence of water at the location of the combustion front at certain locations of the core at certain circumstances tends to prevent energy generation at the combustion front even at high air injection rates. Also, it was shown that the counter current convection/diffusion of fuel gases from the combustion front to upstream locations of the core also known as the roll cell effect adversely influences the advancement of the high temperature combustion front which in turn impacts the oil mobilization and recovery.Combustion performance analysis using oil recovered/volume burned calculations for dry conical tests and oil recovered vs. volume steamed and oxygen oil ratio vs. volume burned as the crucial economical parameters of the design of wet combustion processes were calculated. This study greatly enhances the understanding of the complexity of the in situ combustion process and illustrates its characteristic behavior at or close to its exhaustion.