Compositional Effects in Thermal, Compositional and Reactive Simulation

TL;DR

This paper investigates how compositional modeling choices impact thermal and reactive simulations in oil recovery, revealing that lumping schemes and reaction interpretations significantly influence simulation accuracy and displacement efficiency.

Contribution

It demonstrates the effects of compositional lumping and reaction scheme interpretations on thermal and reactive simulation outcomes in oil recovery.

Findings

Lumping schemes can cause modeling artifacts and miss displacement details.

Reactions involving lighter components accelerate displacement and increase system pressurization.

Molecular weight effects influence reaction rates and displacement dynamics.

Abstract

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.