Abstract
A methodology proposed in a previous paper [ Ind. Eng. Chem. Res. 51 , 14188-14198] for thermodynamic characterization of undefined petroleum fractions was applied to gas-condensate fluids. Using this methodology, input parameters of cubic equations of state and their mixing rules, critical properties and chemical pseudostructures are determined for undefined fractions by minimizing their Gibbs free energy. The results show the feasibility of applying this approach to gas-condensate fluids without making use of either cubic equations of state or mixing rules with specific adjusted parameters for petroleum fluids. Besides, it is shown that the phase equilibrium envelopes of gas-condensate fluids are highly dependent on the critical properties assigned to the undefined petroleum fractions of such fluid fractions and less dependent on the equation used for modeling gas-condensate fluids as a whole. The Absolute Average Error (AAE) considering the best arrangement is 1.79% in predicting the dew point.
Highlights
Gas-condensate fluids from reservoirs are composed of hydrocarbon compounds from C1 to C6 and at least one undefined fraction, containing unidentified compounds ranging from C7 to heavier hydrocarbon compounds
Several methods have been proposed for characterizing undefined fractions, where experimental information in the form of molar distributions, the mole fraction against the Carbon Number (CN), is taken as starting point
The results showed that the gas-condensate phase envelopes depend more on the properties assigned to the undefined heavy fraction than on the pressure-volumetemperature equations modeling such fluids
Summary
Gas-condensate fluids from reservoirs are composed of hydrocarbon compounds from C1 to C6 and at least one undefined fraction, containing unidentified compounds ranging from C7 to heavier hydrocarbon compounds. In the same way as heavier petroleum fluids, the characterization of undefined fractions has a great effect on phase equilibrium simulations of gas-condensate fluids. Several methods have been proposed for characterizing undefined fractions, where experimental information in the form of molar distributions, the mole fraction against the Carbon Number (CN), is taken as starting point. When an experimental molar distribution of undefined fractions is absent, the methods commonly employed in the oil industry are those given by Whitson et al (1990) and Pedersen et al (1992)
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