  This work studies the influence of several compositional effects on thermal
and reactive processes. First, the impact of using a fully compositional model
in the context of thermal simulations is considered. Detailed phase behavior
models rely on compositional descriptions of the oil using up to tens of
components. 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. Lumping schemes are typically calibrated
using experimental data, in order to achieve a good approximation of the phase
behavior of the initial oil. Due to the evaporation and condensation of
components under thermal stimulation, the oil composition will widely vary in
time and space. This works illustrates that even if the lumped schemes were
able to capture the phase behavior of the initial oil, the lack of resolution
can lead to modeling artefacts and/or fail to capture the relevant displacement
processes. Then, the effects of different compositional interpretations of the
lumped pseudo-species appearing in typical reaction schemes are investigated. A
constant, mass-based fraction of the oil is allowed to react, and the reactive
components are modified. Due to molecular weight effects, the reaction rate is
larger when light and medium components are allowed to react. Those effects
result in an increased displacement, leading to faster fronts, larger oil banks
and more pressurization of the system.
