Liquid–liquid equilibria for reservoir fluids + monoethylene glycol and reservoir fluids + monoethylene glycol + water: Experimental measurements and modeling using the CPA EoS

The complex phase equilibrium between reservoir fluids and associating compounds like water and glycols has become more and more important as the increasing global energy demand pushes the oil industry to use advanced methods to increase oil recovery, such as increasing the use of various chemicals to ensure a constant and safe production. The CPA equation of state has been successfully applied in the past to well defined systems and gas condensates, containing associating compounds. It has also been extended to reservoir fluids in presence of water and polar chemicals using modified correlations for critical temperature, pressure and acentric factor.This work presents new phase equilibrium data for binary MEG/reservoir fluid and ternary MEG/water/reservoir fluid systems, where two reservoir fluids from Statoil operated fields are used. The solubility data are reported over a range of temperatures and compositions at atmospheric pressure.The CPA equation of state has been applied to systems containing reservoir fluids, MEG and water. With a minimum number of adjustable parameters from binary pairs, the CPA EoS satisfactory describes the mutual solubility of the binary systems reservoir fluid and MEG. Promising results are also obtained with CPA EoS for ternary mixtures, with some deviations for the solubility of MEG/water in the hydrocarbon phase and for the hydrocarbons in the polar phase.

► New experimental results are presented for two reservoir fluids with MEG and with MEG/water.
► The reservoir fluids is described using a characterization method.
► The experimental results are modeled using the Cubic Plus Association (CPA) equation of state.
► The CPA EoS satisfactory describes the mutual solubility of the binary systems reservoir fluid and MEG.
► Promising results are also obtained with CPA EoS for ternary mixtures.