Compositional Effects in Thermal, Compositional and Reactive Simulation

Abstract

In this work, we study the influence of several compositional effects on thermal and reactive processes.First, we consider the influence of using different lumped pseudo-components. Advanced thermodynamic equilibrium computations are typically required to model the phase behavior in the numerical simulation of thermal recovery processes. Such phase behavior models rely on compositional descriptions of the oil using up to tens of components to obtain accurate solutions. Lumping a large number of components into a smaller number of pseudo-components in order to reduce the computational cost is standard practice for thermal simulations. However, the impact the lumping process has on the displacement processes can be hard to estimate a priori. Thermal, compositional and reactive simulations (such as In-Situ Combustion -ISC) exhibit a tight coupling between mass and energy conservation, through phase behavior, heat transport and reactions. We observe that depending on the number and type of lumped pseudo-components retained in the simulation, the results can exhibit modeling artefacts and/or fail to capture the relevant displacement processes. We illustrate that for several thermal hot gas injection processes, with and without chemical reactions, the displacement results using a small number of pseudo-components do not capture the physical phenomena. Lumping heavy components together overestimates the size of the oil banks and gives inaccurate speeds for multiple fronts.Then, we consider the effects of different compositional interpretations of the lumped pseudo-species appearing in typical reaction schemes. Due to compositional effects, they strongly impact the behavior of the solutions through the intricate interplay between reactions, phase behavior and