HCToolkit/EOS interface: An open source, multi-platform phase equilibria framework for exploring phase behaviour complex mixtures

We present a computational framework that can be used to estimate phase equilibria, equation of state properties and composition-dependent viscosity, aimed at the geochemical community for modelling reservoir processes, and at the chemical community to quickly estimate continuum properties of known mixtures. The framework presented is an extensible, component-based set of modules that can be used in calculating phase properties (volumes and densities, compositions and conditions of phase separation, Henry's Law constants and viscosities) at a wide range of pressures, temperatures and starting compositions. There are two pieces to the model: the HCToolkit (a set of Perl modules that act as computational engines) and the EOSInterface (an ActiveX wrapper for the HCToolkit) which allow the models in the HCToolkit to be usable in Microsoft Office programs. An application hosted in Microsoft Excel is included within the distribution. The EOS models are adaptable for mixtures of arbitrary complexity, with number and types of components only limited by hardware. Model runs with mixtures of over 100 components have been tested, and are perfectly feasible. Implemented within the software are four equations of state; additional equations of state can easily be added. Also implemented are G ^E models and mixture viscosities. Finally, the EOS models provide liquid-vapour flash calculations, liquid-liquid flash (designed for petroleum-aqueous solutions) and the generation of phase diagrams.