Characterization of fluid properties and pseudo-fraction analysis for oils with low gas oil ratios

Authors

  • Fatimah J. Kadhim Department of Petroleum Engineering, College of Engineering, University of Baghdad, Iraq
  • Nagham J. Al-Ameri Department of Petroleum Engineering, College of Engineering, University of Baghdad, Iraq

DOI:

https://doi.org/10.31699/IJCPE.2026.1.9

Keywords:

Sadi Reservoir; PVT modeling; Equation of state; Splitting and Lumping; Regression

Abstract

   The Sadi reservoir is one of the largest and most important unconventional tight oil reservoirs in southern Iraq. However, it suffers from low production rates, necessitating many development strategies that require a correct and reliable characterization of reservoir fluid properties. Whilst these properties are originally obtained from laboratory experiments, measurement errors often occur despite rigorous workflows, which negatively affect the calculation of reservoir fluid properties. This study utilizes the fluid thermodynamics characterization program (PVTp) to generate a reliable model for determining the oil properties of Sadi reservoir. A methodology was developed to simulate fluid thermodynamic tests, including Differential Liberation (DL) and Constant Composition Expansion (CCE) tests. This was achieved through adjusting the Peng-Robinson Equation of State (PR-EOS) by splitting and lumping the C7+ plus fractions and calibrating the Ω parameters to match model results with experimental data using regression. Using the absolute average error (AAE) as a model performance benchmark, the model achieved an AAE of 1% for estimating the relative volume, 0% for estimating oil density, 0.41% for estimating oil formation volume factor, 4% for oil viscosity, and 5% for the gas oil ratio. These values represent the highest AAE recorded for this dataset and show good agreements within the acceptable limits. The PR-EOS model proves to be an accurate fluid characterization alternative that can be applied to similar field data, providing a valuable tool for reservoir management, improving performance, and reducing costs in the future.

Received on 18/06/2025

Received in Revised Form on 11/08/2025

Accepted on 12/08/2025

Published on 30/03/2026

Author Biography

  • Nagham J. Al-Ameri, Department of Petroleum Engineering, College of Engineering, University of Baghdad, Iraq

    Asst. Prof. Dr. Nagham Jasim in Department of Petroleum Engineering, College of Engineering, University of Baghdad, Baghdad, Iraq

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Published

2026-03-30

Issue

Vol. 27 No. 1 (2026): Iraqi Journal of Chemical and Petroleum Engineering

Section

Articles

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Copyright (c) 2026 The Author(s). Published by College of Engineering, University of Baghdad.

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This work is licensed under a Creative Commons Attribution 4.0 International License.

How to Cite

Kadhim, F. J., & Al-Ameri, N. J. (2026). Characterization of fluid properties and pseudo-fraction analysis for oils with low gas oil ratios. Iraqi Journal of Chemical and Petroleum Engineering, 27(1), 105-115. https://doi.org/10.31699/IJCPE.2026.1.9