Simulation of in-situ combustion in a matrix-fracture system at laboratory scale

Abstract

In this work, a mathematical model for in-situ combustion (ISC) was numerically solved for one heterogeneous system composed by a porous-matrix adjacent to a fracture. The main aim was to investigate the effect of fractures on the ISC behaviour. Three mobile-phases were considered: non-volatile single-component oil, incondensable gas, and water. The combustion process was modeled with a kinetic model and two chemical reactions: cracking reaction (coke production), and combustion reaction (coke consumption). A benchmark case was established by comparison of suited numerical results against experimental data from a homogeneous combustion tube experiment reported from the literature. It was found an acceptable agreement between theoretical and experimental data for the temperature field and other variables of interest. The validated mathematical model was extended for one system including adjacent fractures, and their effects over the ISC were investigated. It was observed gas breakthrough because it moves preferably through fractures. It was found that around the combustion front, significant amount of oxygen penetrates from the fracture to the porous matrix, as here the coke combustion takes relevance. In addition, an important amount of oil is expelled from the matrix to the fracture.