Abstract
An efficient and accurate algorithm is developed to predict phase envelopes of natural gases and petroleum fluids using polar coordinate systems. The algorithm is based on approximating the objective functions for bubble points and dew points via Chebyshev polynomials which enables one to easily estimate all physically meaning roots, i.e., saturation points at a specified polar angle. The new algorithm has many significant features in that it is free of estimating an initial guess when calculating bubble point or dew point. It has also the capability of estimating the saturation points with a high degree of accuracy in polar coordinates. Since the calculations are made in polar coordinates, the algorithm yields the saturation points, i.e., the temperature(s) and pressure(s) corresponding to the bubble point or dew point. An adaptive procedure has been developed when constructing the phase envelopes which systematically estimates the next polar angle at which saturation point is calculated. The new developed method has been applied to predict the phase envelopes of a wide range of petroleum fluids including synthetic gas mixtures, gas condensates and crude oils from heavy to volatile oil systems. The comparison of the predicted phase envelopes to the experimental data points exhibits the capability of the new method to successfully predict the phase envelopes of petroleum fluids. Applying different Characterization methods to describe the heavy fractions of real reservoir fluids allows concluding that the new algorithm is a successful method to predict phase envelopes when different characterization schemes are employed.
Published Version
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