Optimization of Separator Size and Operating Pressure for Three-phase Separators in the West Qurna1 Oil Field


  • Ammar Falah Hasan Department of Petroleum Engineering, College of Engineering, University of Baghdad, Baghdad, Iraq
  • Ghanim M. Farman Department of Petroleum Engineering, College of Engineering, University of Baghdad, Baghdad, Iraq https://orcid.org/0000-0002-5657-9598




Operating Pressure, API gravity, Production Optimization, Separator Sizing, Gas Oil Ratio


An optimization study was conducted to determine the optimal operating pressure for the oil and gas separation vessels in the West Qurna 1 oil field. The ASPEN HYSYS software was employed as an effective tool to analyze the optimal pressure for the second and third-stage separators while maintaining a constant operating pressure for the first stage. The analysis involved 10 cases for each separation stage, revealing that the operating pressure of 3.0 Kg/cm2 and 0.7 Kg/cm2 for the second and third stages, respectively, yielded the optimum oil recovery to the flow tank. These pressure set points were selected based on serval factors including API gravity, oil formation volume factor, and gas-oil ratio from the flow tank.

   To improve the optimization process for separator sizes, a Python code was developed, combining the Newton Raphson Method (NRM), and Lang Cost Method (LCM), with Retention time calculations. In this process, total purchase cost was the objective function. Two design scenarios were examined, corresponding to throughput of 105,000 KBPD and 52,500 KBPD respectively. In the first scenario, the NRM, LCM, and Retention time methods within the Python code were employed, resulting in a three-stage separation train with costs of $1,534,630 for the first stage, $1,438,239 for the second stage and $1,025,978 for the third stage. The Total purchase cost for the separation train was $3,988,847. In the second scenario, utilizing two separators for each stage to process the same throughput resulted in lower costs, totaling $823,851.5 per stage and a total purchase cost of $2,471,553. These costs were calculated using the Lang Cost method, which included the material cost and utilized a Lang factor of 3.1 to determine the total purchase cost after adding shipping, installation, commissioning, and start-up expenses.

The first scenario resulted in larger separators and higher costs, while the second scenario showed lower costs, although it required two vessels per stage to process the same throughput. It was observed that the separator efficiencies were influenced by retention time, with increased retention time leading to improved separator efficiency.


A. Ghafarkhah, M.A. Shahrabi, M.K. Moraveji, H. Eslami, "Application of CFD for designing conventional three phase oilfield separator," Egyptian Journal of Petroluem, 2017. https://doi.org/10.1016/j.ejpe.2016.06.003

M. Bothamley, "Gas-liquid separators: quantifying separation performance-part 1," Oil Gas Facilities, vol. 2, no. 04, pp. 21–29, 2013. https://doi.org/10.2118/0813-0021-OGF

A. Darvish Sarvestani, A. Moazami Goodarzi, A. Hadipour, "Integrated Asset Management: A Case Study of Technical and Economic Optimization of Surface and Well Facilities," Petroleum Science, 2019. https://doi.org/10.1007/S12182-019-00356-6

N. Kharoua, L. Khezzar, H.N. Saadawi, "CFD modelling of a horizontal three-phase separator: a population balance approach," American Journal of Fluid Dynamics, vol. 3, no. 4, pp. 101–118, 2013.

M.K. Moraveji, M. Hejazian, "CFD examination of convective heat transfer and pressure drop in a horizontal helically coiled tube with CuO/Oil base nanofluid," Numerical Heat Transfer, Part A: Applications, vol. 66, no. 3, pp. 315–329, 2014. https://doi.org/10.1080/10407782.2013.872976

G. Al-Zubaidy, "Determining Optimum Oil Separator Size and Optimum Operating Pressure," Iraqi Journal of Chemical and Petroleum Engineering, vol. 23, no. 2, pp. 43–46, 2022. https://doi.org/10.31699/IJCPE.2022.2.6

M. Mostafaiyan, M.R. Saeb, A.E. Alorizi, M. Farahani, "Application of evolutionary computational approach in design of horizontal three-phase gravity separators," Journal of Petroleum Science and Engineering, 2014. https://doi.org/10.1016/j.petrol.2014.04.003

T. Ahmed, P.A. Russell, F. Hamad, S. Gooneratne, "Experimental analysis and computational fluid dynamics modelling of pilot-scale three-phase separators," SPE Production and Operations, vol. 34, no. 04, 2019. http://dx.doi.org/10.2118/197047-PA

M. Ghaedi, A.N. Ebrahimi, M.R. Pishvaie, "Application of Genetic Algorithm for Optimization of Separator Pressures in Multistage Production Units," Chemical Engineering Communication, vol. 201, no. 7, pp. 926-938, 2014. https://doi.org/10.1080/00986445.2013.793676

I.H. Kim, S. Dan, H. Kim, H.R. Rim, J.M. Lee, E.S. Yoon, "Simulation-based Optimization of Multistage Separation Process in Offshore Oil and Gas Production Facilities," Industerial and Engineering Chemistry Research, vol. 53, no. 21, pp. 8810-8820, 2014. https://doi.org/10.1021/ie500403a

M.J. Al-Khafaji, Wafaa’ Mustafa Al-Kattan, "Using Elastic Properties as a Predictive Tool to Identify Pore-Fluid Type in Carbonate Formations," Iraqi Journal of Chemical and Petroleum Engineering, vol. 20, no. 1, 2019. https://doi.org/10.31699/IJCPE.2019.1.8

A. Danesh," PVT and Phase Behavior of Petroleum Reservoir Fluids", Developments in Petroleum Science, vol. 47, 1998.

L. Zhang, W. Zhang, Y. Li, B. Song, D. Liu, Y. Deng, J. Xu, Y. Wang, "Sequence Stratigraphy, Sedimentology, and Reservoir Characteristics of the Middle Cretaceous Mishrif Formation, South Iraq," Journal of Marine Science and Engineering, vol. 11, no. 6, 2023. https://doi.org/10.3390/jmse11061255

S. Osfouri, R. Azin, Z. Rezaei, M. Moshfeghian, "Integrated Characterization and a Tuning Strategy for the PVT Analysis of Representative Fluids in a Gas Condensate Reservoir," Iranian Journal Oil & Gas Science and Technology, vol. 7, no. 1, pp. 40-59, 2018. https://doi.org/10.22050/ijogst.2017.78181.1383

N. Couto, J. Cardoso, L.M. Gonzalez-Gutierrez, A. Souto-Iglesias, "Coupled CFD-response surface method (RSM) methodology for optimizing jet ability operating conditions," ChemEngineering, 2018. https://doi.org/10.3390/chemengineering2040051

M. Mostafaiyan, M.R. Saeb, A.E. Alorizi, M. Farahani, "Application of evolutionary computational approach in design of horizontal three-phase gravity separators," Journal of Petroleum Science and Engineering. 119, 2014. http://dx.doi.org/10.1016/j.petrol.2014.04.003

Z. Khalifat, M. Zivdar, R. Rahimi, "Simulation of an industrial three-phase boot separator using computational fluid dynamics," Journal of Gas Technology, vol. 6, pp. 30–42, 2020.

W.P. Dokianos, "A simplified approach to sizing 2 and 3 phase separators for low GOR and low pressure onshore production batteries," in SPE Production And Operations Symposium, 2015. https://doi.org/SPE-173598-MS

S.A. Shedid, "A new technique for identification of flow units of shaly sandstone reservoirs," Journal of Petroleum Exploration and Production Technology, vol. 8, no. 2, 2018.


A. Ghafarkhah, M.A. Shahrabi, M.K. Moraveji, H. Eslami, "3D computational-fluid-dynamics modeling of horizontal three-phase separators: an approach for estimating the optimal dimensions," SPE Production and Operations, 33 (04): 879–895, 2018. https://doi.org/10.2118/189990-pa

A. Soleymanzadeh, S. Parvin, S. Kord, "Effect of overburden pressure on determination of reservoir rock types using RQI/FZI, FZI* and Winland methods in carbonate rocks," Petroleum Science, vol. 16, no. 6, 2019.


Y. Xu, M. Liu, C. Tang, "Three-dimensional CFD–VOF–DPM simulations of effects of low-holdup particles on single-nozzle bubbling behavior in gas–liquid–solid systems," Chemical Engineering Journal, vol. 222, pp. 292–306, 2013. https://doi.org/10.1016/j.cej.2013.02.065

A. Raoufi, M. Shams, M. Farzaneh, R. Ebrahimi, "Numerical simulation and optimization of fluid flow in cyclone vortex finder," Chemical Engineering and Processing: Process Intensification, vol. 47, no. 1, pp. 128–137, 2008. https://doi.org/10.1016/j.cep.2007.08.004

A. Sharma, N. Chaudhary, "Correction to: Software Cost Estimation for Python Projects Using Genetic Algorithm," International Conference on Communication and Intelligent System,. ICCIS 2019., vol. 120, Springer, 19 August 2020. https://doi.org/10.1007/978-981-15-3325-9_40

H. Zhu, N. Shougarian, G. Ojard, K. Sinha, O. de Weck, E. Arnold, "Exploring Early Stage Cost-Estimation Methods Using Off-the-Shelf Tools: A Preliminary Study," International Conference on Communication and Intelligent System. ICCIS 2016, Springer, 09 December 2016. https://doi.org/10.1007/978-3-319-49103-5_28




How to Cite

Hasan, A. F., & Farman, G. M. (2024). Optimization of Separator Size and Operating Pressure for Three-phase Separators in the West Qurna1 Oil Field. Iraqi Journal of Chemical and Petroleum Engineering, 25(1), 103-110. https://doi.org/10.31699/IJCPE.2024.1.10

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