Assessing Reservoir Heterogeneity through Integrated Petrophysical and Geological Modeling: Case Study of the Yamama Reservoir, Ratawi Field, Southern Iraq
Main Article Content
Abstract
Constructing a geologically realistic reservoir model and accurately evaluating petrophysical properties are critical components for effective reservoir management. Such efforts enable reliable assessment of hydrocarbon potential and support predictive development scenarios through numerical simulations. This study aims to characterize the Yamama carbonate reservoir in the Ratawi Field, southern Iraq, and to build a static geological model as a foundation for future dynamic simulation. Comprehensive well data, including wireline logs, core analysis, and geological reports, were integrated to interpret petrophysical parameters such as shale volume, effective porosity, and water saturation. Additionally, facies classification was performed using cluster analysis to define lithological variability across the reservoir. A structural framework was established based on contour maps and well tops, followed by 3D property modeling using geostatistical techniques. Experimental variogram models were constructed for each facies and zone to enhance distribution accuracy. The Yamama Formation was confirmed -consistent with previous studies- to consist of five vertical units, three reservoir-bearing (YA, YB, YC) and two barriers (C1, C2). However, this study uniquely establishes an evaluation framework using data from eight wells penetrating the formation, unlike earlier studies constrained by limited wells. Among these units, YB demonstrated the most favorable properties, accounting for approximately 63% of the estimated 1800 MMSTB OOIP, consistent with operator reports. Overall, reservoir quality improves northwestward and declines eastward, with moderate characteristics in the southern sector.
Downloads
Article Details
Section
How to Cite
References
Al-Dujaili, A.N., Shabani, M. and AL-Jawad, M.S., 2023. Effect of heterogeneity on recovery factor for carbonate reservoirs. A case study for Mishrif Formation in West Qurna Oilfield, Southern Iraq. Iraqi Journal of Chemical and Petroleum Engineering, 24(3), pp. 103-111. https://doi.org/10.31699/IJCPE.2023.3.10.
Akinbode, O.B., and Samuel, O.T., 2025. Analysis of an unsupervised clustering algorithm for lithofacies classification in “Riga” field, Niger Delta. Scientific Research Journal, 13(4), pp. 19–31. https://doi.org/10.31364/SCIRJ/v13.i04.2025.P04251018.
Al-Ameri, T., Al-Khafaji, A., and Jasim, S., 2015. IRP11 – Yamama Formation oil source assessment using biomarkers & carbon isotope analysis, Ratawi Oil Field, Southern Iraq. European Association of Geoscientists & Engineers, 2015, pp. 1 – 5. https://doi.org/10.3997/2214-4609.201414384.
Alhakeem, N.S.A., 2019. Petrophysical study and geological modeling of Yamama Formation in Subba, Luhais, and Ratawi oil fields, Southern Iraq. PhD thesis, University of Baghdad.
Alhakeem, N.S., Nasser, M.E., and Al-Sharaa, G.H., 2019. 3D geological modeling for Yamama reservoir in Subba, Luhais, and Ratawi oil fields, south of Iraq. Iraqi Journal of Science, 60(5), pp. 1023–1036. https://doi.org/10.24996/ijs.2019.60.5.12.
Al-Iessa, I.A.A., 2012. Facies reservoir evaluation of Yamama Formation in Ratawi Field, South of Iraq. MSc thesis, University of Basrah.
Al-Iessa, I.A., and Zhang, W.Z., 2023. The methods of determination of stratigraphic boundaries and reservoir units for the Yamama Formation in the Ratawi Oil Field, Southern Iraq. Iraqi Geological Journal, 56(1), pp. 285–309. https://doi.org/10.46717/igj.56.1D.21ms-2023-4-30.
Al-Shahwan, M.F., 2002. Thermal maturity nomenclature of the Lower Chalk Sequence, Southern Iraq: Applications for calculating oil potential. PhD thesis, University of Baghdad.
Al-Shahwan, M.F., and Al-Iessa, I.A., 2015. Petrophysical characteristics study of carbonate Yamama reservoir in Ratawi Oil Field, South of Iraq. Journal of Basrah Researches, Sciences, 40)4(
Al-Siddiki, A.A., 1978. The geology and the hydrocarbon prospects of the Ratawi, Yamama and Sulaiy Formation in Southeastern Iraq. Subsurface section. Southern Petroleum Organization, Iraq.
Al-Siddiki, A.A., 1977. Subsurface geology of southeastern Iraq. paper presented at the 10th Arab Petroleum Congress, Tripoli, Libya, paper no. 141(B-3), P. 47.
Alameedy, U., Almomen, A., and Abd, N., 2023. Evaluating machine learning techniques for carbonate formation permeability prediction using well log data. Iraqi Geological Journal, 56(1), pp. 175–187. https://doi.org/10.46717/igj.56.1D.14ms-2023-4-23.
Bassiouni, Z., 1994. Theory, measurement, and interpretation of well logs. Society of Petroleum Engineers. https://doi.org/10.2118/9781555630560.
Bateman, R.M., 2012. Openhole log analysis and formation evaluation. Society of Petroleum Engineers. https://doi.org/10.2118/9781613991565.
Chatton, M., and Hart, E., 1962. Announcement of a rock unit redefined: Ratawi Formation. OCE, internal report.
Clavier, C., Coates, G., and Dumanoir, J., 1984. Theoretical and experimental bases for the dual-water model for interpretation of shaly sands. SPE Journal, 24(2), pp. 153–168. https://doi.org/10.2118/6859-PA.
Cosentino, L., 2001. Integrated reservoir studies. Editions Technip, Institut français du pétrole publications.
Darling, T., 2005a. Chapter 1 – Basics. In: T. Darling (ed.), Well Logging and Formation Evaluation. Burlington: Gulf Professional Publishing, pp. 1–27. https://doi.org/10.1016/B978-075067883-4/50001-2.
Darling, T., 2005b. Chapter 5 – Advanced log interpretation techniques. In: T. Darling (ed.), Well Logging and Formation Evaluation. Burlington: Gulf Professional Publishing, pp. 67–102. https://doi.org/10.1016/B978-075067883-4/50005-X.
Dunnington, H.V., 1958. Stratigraphical distribution of oil fields in the Iraq–Iran–Arabia Basin. Journal of the Institute of Petroleum, 53, pp. 129–161.
Egbele, E., Ezuka, I., Onyekonwu, M.O., 2005. Net-to-gross ratios: implications in integrated reservoir management studies. SPE paper. https://doi.org/10.2523/98808-MS.
Han, T.C., Yan, H., and Fu, L.Y., 2021. A quantitative interpretation of the saturation exponent in Archie’s equations. Petroleum Science, 18(2), pp. 444–449. https://doi.org/10.1007/s12182-021-00547-0.
Hilchie, D.W., 1982. Applied openhole log interpretation (for geologists and engineers). Golden, Colorado, Dev. Pub. Co., 161 pp.
Jassim, S.Z., and Goff, J.C., 2006. Geology of Iraq. Dolin, Prague.
Khamees, L.A., and Abdulrazzaq, F.N., 2024. Evaluation uncertainty in the volume of oil in place in Mishrif Reservoir. Journal of Chemical and Petroleum Engineering, 58(2), pp. 243–254. https://doi.org/10.22059/jchpe.2024.373776.1491.
Kumar, K.C.H., 2010. On the application of Simandoux and Indonesian shaly sand resistivity interpretation models in low and high Rw regimes. 8th Biennial International Conference and Exposition on Petroleum Geophysics, pp. 1–11. https://spgindia.org/2010/071.pdf.
Kurniawan, D., Winardi, S., and Anggara, F., 2021. Linking between sedimentary facies and petrophysical rock type: a case study. IOP Conference Series: Earth and Environmental Science, 789, P. 012077. https://doi.org/10.1088/1755-1315/789/1/012077.
Ma, Y.Z., 2019a. Facies and lithofacies classifications from well logs. In: Y.Z. Ma (ed.), Quantitative Geosciences: Data Analytics, Geostatistics, Reservoir Characterization and Modeling. Cham: Springer, pp. 231–254. https://doi.org/10.1007/978-3-030-17860-4_10.
Ma, Y.Z., 2019b. Geostatistical estimation methods: Kriging. In: Y.Z. Ma (ed.), Quantitative Geosciences: Data Analytics, Geostatistics, Reservoir Characterization and Modeling. Cham: Springer, pp. 373–401. https://doi.org/10.1007/978-3-030-17860-4_16.
Ma, Y.Z., 2019c. Geostatistical variography for geospatial variables. In: Y.Z. Ma (ed.), Quantitative Geosciences: Data Analytics, Geostatistics, Reservoir Characterization and Modeling. Cham: Springer, pp. 301–330. https://doi.org/10.1007/978-3-030-17860-4_13.
Ma, Y.Z., 2019d. Hydrocarbon volumetrics estimation. In: Y.Z. Ma (ed.), Quantitative Geosciences: Data Analytics, Geostatistics, Reservoir Characterization and Modeling. Cham: Springer, pp. 539–563. https://doi.org/10.1007/978-3-030-17860-4_22.
Ma, Y.Z., 2019e. Introduction to geological and reservoir modeling. In: Y.Z. Ma (ed.), Quantitative Geosciences: Data Analytics, Geostatistics, Reservoir Characterization and Modeling. Cham: Springer, pp. 333–349. https://doi.org/10.1007/978-3-030-17860-4_14.
Ma, Y.Z., 2019f. Introduction to model upscaling, validation and history match. In: Y.Z. Ma (ed.), Quantitative Geosciences: Data Analytics, Geostatistics, Reservoir Characterization and Modeling. Cham: Springer, pp. 565–591. https://doi.org/10.1007/978-3-030-17860-4_23.
Ma, Y.Z., 2019g. Stochastic modeling of continuous geospatial or temporal properties. In: Y.Z. Ma (ed.), Quantitative Geosciences: Data Analytics, Geostatistics, Reservoir Characterization and Modeling. Cham: Springer, pp. 403–433. https://doi.org/10.1007/978-3-030-17860-4_17.
Motlaq, H.G., 1999. Sequential stratigraphy of Yamama Formation in Al-Siba field. internal report, Oil Exploration Company, Baghdad.
Murtadha, Z.I., 2012. Reservoir evaluation of Yamama Formation, Ratawi Oil Field. MSc thesis, University of Baghdad.
Murtazin, T., Sergey Usmanov, Marat Validov, and Marat Amerkhanov, 2022. The development of automatic system for geological modeling of extra-viscous oil deposits on the example of Tatarstan Republic. International Petroleum Technology Conference Proceedings, D032S172R001. https://doi.org/10.2523/IPTC-22175-MS.
Phan, V., 2002. Modeling technique for generating fluvial reservoir descriptions conditioned to seismic data. PhD thesis, Stanford University. https://earthsci.stanford.edu/ERE/pdf/pereports/Phan02.pdf.
Pickett, G.R., 1966. A review of current techniques for determination of water saturation from logs. Journal of Petroleum Technology, 18(11), pp. 1425–1433. https://doi.org/10.2118/1446-PA.
Rabanit, P.M.V., 1952. Rock units of Basrah area. BPC, internal report.
Rozarian, A., 1995. Sedimentological and depositional history of the Yamama Formation, Southern Iraq. INOC, internal report.
Sadooni, F., 1993. Stratigraphic sequence, microfacies, and petroleum prospects of the Yamama Formation, Lower Cretaceous, Southern Iraq. AAPG Bulletin, 77, pp. 1971–1988. https://doi.org/10.1306/BDFF8F92-1718-11D7-8645000102C1865D.
Salem, H., and Chilingarian, G., 1999. The cementation factor of Archie’s equation for shaly sandstone reservoirs. Journal of Petroleum Science and Engineering, 23, pp. 83–93. https://doi.org/10.1016/S0920-4105(99)00011-5.
Santos, A., Scanavini, H.F., Pedrini, H., Schiozer, D.J., Munerato, F.P. and Barreto, C.E., 2022. An artificial intelligence method for improving upscaling in complex reservoirs. Journal of Petroleum Science and Engineering, 211, P. 110071.https://doi.org/10.1016/j.petrol.2021.110071.
Schlumberger, 2018. Petrel software user guide, version 2018. Schlumberger, Houston.
Steineke, M., and Bramkamp, R.A., 1952. Mesozoic rocks of eastern Saudi Arabia. American Association of Petroleum Geologists Bulletin, 36(5), P. 909.
Tibshirani, R., Walther, G., and Hastie, T., 2001. Estimating the number of clusters in a data set via the gap statistic. Journal of the Royal Statistical Society: Series B (Statistical Methodology), 63(2), pp. 411–423. http://www.jstor.org/stable/2680607.
TotalEnergies, 2021. Subsurface workshop about Ratawi Field Development Plan. internal Ratawi Field development study, Iraq, Basrah.
Turner, A.K., Kessler, H., van der Meulen, M.J., 2021. Introduction to modeling terminology and concepts. In: Applied Multidimensional Geological Modeling. Wiley, pp. 1–12. https://doi.org/10.1002/9781119163091.ch1.
Wang, J., Wancheng Z., Hui L. , Tao Q., and Maiyong Z. , 2025. Three-dimensional geological modeling of thin ore body and complex strata based on multi-point geostatistics. Engineering Geology, 352, P. 108056. https://doi.org/10.1016/j.enggeo.2025.108056.
Waxman, M.H., and Smits, L.J.M., 1968. Electrical conductivities in oil-bearing shaly sands. SPE Journal, 8(2), pp. 107–122. https://doi.org/10.2118/1863-A.
Zhang, Y., 2009. Introduction to geostatistics – course notes. Colorado School of Mines.