Application of the CPA Equation of State to Reservoir Fluids in Presence of Water and Polar Chemicals

摘要

The complex phase equilibrium between reservoir fluids and associating compounds like water, methanol and glycols has become more and more important as the increasing global energy demand pushes the oil industry to target reservoirs with extreme or complicated conditions, such as deep or offshore reservoirs. Conventional equations of state (EoS) with classical mixing rules can not satisfactorily predict or even correlate the phase equilibrium of those systems. A promising model for such systems is the Cubic-Plus-Association (CPA) EoS which has been successfully applied to well-defined systems containing associating compounds. In this work, CPA is extended to reservoir fluids in presence of water and polar chemicals by using a newly developed characterization rocedure for ill-defined C7+ fractions. Satisfactory results are obtained for multicomponent systems using a minimum number of adjustable parameters which are obtained from binary systems. Modeling of mutual solubility between light hydrocarbons and water is also addressed.