Modeling of asphaltene and water associations in petroleum reservoir fluids using cubic‐plus‐association EOS

Abstract

Asphaltene is a group of complex compounds commonly present in petroleum reservoir fluids. It is conceivable that asphaltenes strongly interact with water through hydrogen bonding, affecting phase behavior of water/oil mixtures with/without forming an asphaltene‐rich phase. In this research, the cubic‐plus‐association equation of state (CPA EOS) is applied to multiphase behavior resulting from self‐ and cross‐associations of asphaltenes and water in petroleum fluids. This article also presents a new correlation for binary interaction parameters for water with n‐alkanes for the CPA EOS by using three‐phase data for water/n‐alkane binaries. A method is proposed to characterize mixtures of asphaltene‐containing oil with water using the CPA EOS. Results show that the CPA EOS can represent multiphase behavior for water/oil mixtures with up to four equilibrium phases: asphaltene‐rich, solvent‐rich, aqueous, and vapor phases. Case studies include bitumen/water mixtures, involving asphaltene‐water emulsion, water solution in bitumen, and their continuous transition with varying temperature. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3429–3442, 2018