Application of Gaussian quadrature method to characterize heavy ends of hydrocarbon fluids for modeling wax precipitation

Abstract

a b s t r a c tThe hydrocarbon plus fractions that comprise a significant portion of naturally occurring hydrocarbon fluids create major problems when determining the thermodynamic properties and the volumetric behavior of these fluids by equations of state. These problems arise due to the difficulty of properly characterizing the plus fractions (heavy ends). Proper characterization of the heavier components is important when cubic equations of state and/or solid formation thermodynamic models are used to describe complex phase behavior of reservoir fluids. The effect of heavy fractions characterization on thermodynamic modeling of wax precipitation has been investigated using different models including Won, Pan and proposed models. In order to characterize the plus fraction (heavier part) as a series of pseudocomponents, a probability model that expresses the mole fraction as a continuous function of the molecular weight has been used. The study has been conducted using several mixtures. Two different SCN (single carbon number), C 7 þ and C 10 þ were chosen. The Chosen SCN were distributed to multi-components of five, six, and/or ten using continuous function and Gaussian quadrature method. The results showed that the fractioning is required to be able to predict wax precipitation. Distribution of C 10 þ using a proper distribution function has shown improvement in predictions of WAT and the amount of wax deposited in comparison with the characterization of C 7 þ using semi-continuous approach. In predicting of WAT and the amount of wax build up the developed model showed superiority over the others.

A consistent method for simultaneous calculation of upper and lower dew point pressures of gas condensate fluids

“…The third method which has been used to describe the heavy fraction was the Gaussian quadrature method (Tabatabaei-Nejad and Khodapanah, 2011). Applying this method, the C 7þ fraction was described using 3 pseudo-components for which RiaziDaubert and LeeeKesler correlations were used to estimate the critical properties and acentric factors, respectively.…”

Competing failure analysis considering cascading functional dependence and random failure propagation time

“…If a multidimensional integral can be reduced to a lower dimensionality in an analytical way (ie, symbolic integration), methods like iterated integrals, using symmetry properties, changing variables, or using combination rules of events can be applied . On the other hand, if it is hard to calculate the primitive function of integrand by symbolic integration, integral methods like Newton‐Cotes formulas, Gaussian quadrature, or Monte Carlo integration methods can be used.…”

Application of polar coordinates to construct phase envelope of natural gases and petroleum fluids: A new robust and innovative method

“…Since the heavy ends of the reservoir fluids usually have some uncertainties in the molecular weight and critical properties, in general, characterizing the heavy fractions is inevitable to improve the prediction results of an EoS. Therefore, the C 7þ fraction of this fluid (GC 3) has been described with 4 pseudo-components using Gaussian quadrature method of Gamma distribution function Danesh, 1998;Tabatabaei-Nejad and Khodapanah, 2011). The critical properties and acentric factors of the pseudo-components were estimated, respectively, using the correlations proposed by Twu and Edmister (Ahmed, 2001;Twu, 1984;Edmister, 1958).…”