Impact of Phase Behavior Modeling on In-Situ Combustion Process Performance

摘要

To facilitate the study of reactive-compositional porous media processes we develop a virtual kinetic cell (single-cell model) as well as a virtual combustion tube (one-dimensional model). Both models are fully compositional based on an equation of state. In this work, we apply the models to analyze phase behavior sensitivity for in-situ combustion, a thermal oil recovery process. For the one-dimensional model we first conduct sensitivity analyses to numerical discretization errors and provide grid density guidelines for proper resolution of in-situ combustion behavior. A critical condition for success of in-situ combustion processes is the formation and sustained propagation of a high-temperature combustion front. Using the models developed we study the impact of phase behavior on ignition/extinction dynamics as a function of the operating conditions. We show that when operating close to ignition/extinction branches, a change of phase behavior model is likely to shift the system from a state of ignition to a state of extinction or vice versa. For both the rigorous equation of state based and a simplified, but commonly used, K-value based phase behavior description we identify areas of operating conditions which lead to ignition. For a particular oil we show that the simplified approach overestimates the required air injection rate for sustained front propagation by 17% compared to the equation of state based approach.