Enhancing asphaltene precipitation modeling by cubic-PR solid model using thermodynamic correlations and averaging techniques

Aktham E Shoukry,Ahmed H El-Banbi,Helmy Sayyouh

doi:10.1007/s12182-019-00377-1

Aktham E Shoukry, Ahmed H El-Banbi + Show 1 more

Open Access

https://doi.org/10.1007/s12182-019-00377-1

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Abstract

Cubic equation-of-state solid models are one of the most widely used models to predict asphaltene precipitation behavior. Thermodynamic parameters are needed to model precipitation under different pressures and temperatures and are usually obtained through tuning with multi asphaltene onset experiments. For the purpose of enhancing the cubic Peng–Robinson solid model and reducing its dependency on asphaltene experiments, this paper tests the use of aromatics and waxes correlations to obtain these thermodynamic parameters. In addition, weighted averages between both correlations are introduced. The averaging is based on reported saturates, aromatics, resins, asphaltene (SARA) fractions, and wax content. All the methods are tested on four oil samples, with previously published data, covering precipitation and onset experiments. The proposed wax-asphaltene average showed the best match with experimental data, followed by a SARA-weighted average. This new addition enhances the model predictability and agrees with the general molecular structure of asphaltene molecules.

Highlights

As Kokal and Sayegh described asphaltenes as “The cholesterol of petroleum” (Kokal and Sayegh 1995), asphaltene precipitation/deposition is recognized as one of the most significant problems in the oil industry
Asphaltene precipitation/deposition could occur in the reservoir, perforation tunnels, wellbore and tubulars, surface chokes, flowlines, processing facilities, transmission pipelines, and stock tanks
The averaging is based on the SARA analysis and wax content of the sample

Summary

Introduction

As Kokal and Sayegh described asphaltenes as “The cholesterol of petroleum” (Kokal and Sayegh 1995), asphaltene precipitation/deposition is recognized as one of the most significant problems in the oil industry. Asphaltene precipitation/deposition could occur in the reservoir, perforation tunnels, wellbore and tubulars, surface chokes, flowlines, processing facilities (separators), transmission pipelines, and stock tanks. Precipitation in any stage of the previous stages causes interruption, reduction, and possible stoppage of the production process, letting aside the costs of remedial/ removal actions. To avoid such problems, it is best to mitigate asphaltene precipitation either by avoiding the conditions of instability, or by adding inhibitors to prevent the precipitation process. SARA analysis is usually performed on stock tank oils to report percentage, in wt% or mol%, of each fraction.

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