Pore-scale modelling of the coupled thermal and reactive flow at the combustion front during crude oil in-situ combustion

A stable combustion front is important to achieve a successful in-situ combustion process for the crude oil recovery. The understanding of the multiple physicochemical and thermal processes at the combustion front is fundamental to reduce the potential risks, such as high burning temperature and low oxygen utilization. In the present study, a pore-scale modelling of the combustion front was employed based on the Lattice Boltzmann method to couple the fluid flow, heat and mass transfer and chemical reactions with the geometrical evolution. A thermal counter-slip algorithm was developed to solve the coupled interface conditions between conjugated heat transfer and heterogeneous reactions. The accuracy of the coupled lattice Boltzmann numerical models was validated by the finite element method. Pore-scale simulation was then performed to model the thermal and reacting flows through a two-dimensional model porous medium. The numerical simulation distinguished four characteristic regimes corresponding to different control mechanisms for the reacting flow. The study showed that the diffusion-limited mechanism is most desirable for the stable combustion in terms of the ideal burning temperature and full oxygen utilization. The control regime diagram was mapped on the Péclet-Damköhler plane for the specified computational domain. The effects of the Péclet and Damköhler numbers on the burning temperature, combustion front propagation velocity and oxygen utilization were then analyzed to obtain some insights about the control of the combustion front in the ISC process.