Cubic-Plus-Association Equation of State for Asphaltene Precipitation in Live Oils

Abstract

We apply a cubic-plus-association equation of state (CPA-EOS) to study the asphaltene precipitation in live oils from temperature, pressure, and composition effects. The live oils are characterized by considering the pure components, the pseudo-hydrocarbon components, and the hydrocarbon residue. The hydrocarbon residue is further divided into the “heavy” component and asphaltenes. The asphaltene precipitation is modeled as liquid−liquid equilibrium between the upper onset and bubble point pressures and as gas−liquid−liquid equilibrium between the bubble point and lower onset pressures. In our work, the self-association between asphaltene molecules and the cross-association between asphaltene and “heavy” molecules are taken into account. The EOS parameters are either directly available, from our recent work, or from fitting the bubble point pressure. The cross-association energy between asphaltene and “heavy” molecules depends upon the temperature but is independent of the pressure. We reproduce the experiments of the amount and onset pressures of asphaltene precipitation in several live oils over a broad range of composition, temperature, and pressure conditions.

Thermodynamic modelling of asphaltene precipitation and related phenomena

“…A number of authors have used the CPA equation of state to model asphaltene phase behaviour [161][162][163][164][165]. In the work of Li and Firoozabadi [161,162], the PR equation of state is used within the CPA framework.…”

“…In the work of Li and Firoozabadi [161,162], the PR equation of state is used within the CPA framework. The first study focuses on asphaltene precipitation in model solutions as well as in heavy oil and bitumen, whereas the latter two are considered to be a mixture of three pseudocomponents: saturates, aromatics/resins and asphaltenes [161].…”

“…3, in which the effect of temperature is analysed in comparison with experimental data. In the second study, asphaltene precipitation from a 'live' oil is modelled, where the live oil is considered to be a mixture of a considerable number of components and pseudocomponents, together with a hydrocarbon residue [162]. The latter is divided into a heavy pseudocomponent and asphaltene.…”

General algorithm for multiphase equilibria calculation at given volume, temperature, and moles

“…While there was a main focus on two-phase compositional modelling in the past, nowadays, there is an increasing interest in three and generally multi-phase compositional models which is motivated by CO 2 sequestration [12], processes related to CO 2 or steam enhanced oil recovery [1] or asphaltene precipitation from bitumens [14,15].…”

Estimation of asphaltene precipitation from titration data: a hybrid support vector regression with harmony search

“…In the context of asphaltene precipitation modeling, several researchers and investigators endeavored to develop potent and reliable models for predicting the onset of asphaltene precipitation and its amount. However, phase behavior of asphaltene precipitation remains still unclear mainly due to its structure and properties complexity [12][13][14][15][16][17][18][19]. Available models used for predicting the onset of asphaltene precipitation and its amount can be divided into two main groups.…”