This book addresses conventional and new predictive methodologies for estimating thermophysical properties of heavy petroleum fluids. For the unidentifiable fractions forming the fluids, chemical structures are calculated so that property estimation methods for mixtures of identifiable components are now available for such fractions. Chemical and multiphase equilibriums are of utmost importance; hence, the most significant ones involving heavy petroleum fluids are determined and illustrated using advanced equations of state such as sPC-SAFT and EoS/GE. The included phase equilibriums are phase envelopes of reservoir fluids, asymmetric mixtures between light solvents and bitumen including the presence of water and asphaltenes, among others. Besides, heavy petroleum fluids are analyzed from the Newtonian and non-Newtonian viewpoints, exploring their complex rheological behavior. Finally, complemented by online an Excel program for the thermodynamic characterization of unidentifiable petroleum fractions, this book is a useful resource for engineers and researchers in the petroleum industry and is also of interest to students studying chemical and petroleum engineering.