The global energy demand continues to rise, driven by population growth and urbanisation, and the efficiency of energy processes need to be improved to meet this need. Understanding fluid behaviour at subsurface conditions is imperative to design, optimize and predict subsurface processes such as fossil fuel extraction, enhanced recovery and carbon capture and storage (CCS), and technologies that aim to offset the environmental cost of such processes. Thermodynamic properties, such as interfacial tension, viscosity and vapour-liquid equilibria etc., of various reservoir fluids including hydrocarbons and carbon dioxide (and associated mixtures), can heavily influence these large-scale processes, and are further impacted by pore-scale confinement effects. In this session, we invite submissions that incorporate established and innovative experimental techniques to ascertain fluid properties and phase behaviour at representative conditions. We also encourage novel modelling approaches that build upon conventional cubic Equation of State (EOS) to describe these thermodynamic properties at relevant conditions.