Simulation of unstable viscous fluid displacement from porous medium considering inter-phase chemical interactions

The paper studies the unstable displacement of a viscous fluid from a porous medium while taking into account the inter-phase chemical interactions. As a viscous fluid is displaced by a less viscous fluid, the Saffman-Taylor instability occurs at the interface: the less viscous fluid breaks through the layer of the more viscous fluid being displaced, forming so-called “viscous fingers” (channels). The instability leads to the bending of the initially flat interface and the contact area between the phases increases. This phenomenon should be considered when modeling the displacement process taking into account the inter-phase chemical reactions because as the interface area between the phases grows, the chemical reaction rate also increases. This paper presents a simulation model describing the thermal gas oil displacement process when oil is displaced by a mixture of hot water and gas. The gas and oil produce an exothermic chemical reaction resulting in the oil viscosity decrease, which leads to a better displacement. The reaction rate simulation model can consider the instability effects. The paper also presents a method for estimating the phase-to-phase boundary area used for 3D modeling of unstable viscous fluid displacement from a porous substance.