Phase behavior prediction of petroleum fluids with minimum characterization data

A new accurate and efficient computational method is presented for property calculation and phase equilibrium prediction of petroleum fluids using a m inimum amount of input characterization data. This method is based on the c ombination of the discrete thermodynamic framework of the light components and a continuous thermodynamic characterization of the plus-fraction in pet roleum fluids, The key features of the proposed method are the facts that: (i) the light fraction is specified by a definite number of discrete compon ents with known characterization parameters; (ii) the plus-fraction is char acterized by a generalized continuous distribution function in which three average plus-fraction properties, namely, the average molecular weight, the average normal boiling point and the average specific gravity, appear as t he input data; (iii) there is no need for this method to characterize vario us families of hydrocarbons which may be present in the petroleum fluid plu s-fraction; (iv) the model is applicable to any equation of state (EOS) and any set of mixing rules and combining rules; (v) the conventional multi-co mponent phase behavior packages as well as continuous (or semi-continuous) phase equilibrium algorithms can be used with this model to predict the equ ilibrium ratio, gas/oil ratio, and other petroleum fluid properties; (vi) t his model has the potential for application in phase behavior predictions w ith solid deposition which is the case with waxy and asphaltenic condensate s and other crude oils. The proposed model is applied for vapor-liquid equi librium calculation and bulk, liquid and vapor, phases property prediction of several reservoir fluid mixtures for which experimental data are availab le with success. This method is accurate because it predicts the properties of petroleum reservoir fluids as precisely as any other existing method. I t is efficient because it removes the guess work for the characterization o f the plus-fraction which has been the major barrier in the efficient calcu lation of bulk and phase equilibrium properties of petroleum reservoir flui ds. (C) 1999 Published by Elsevier Science B.V. All rights reserved.