Association of the Flow Units with Facies Distribution, Depositional Sequences, and Diagenetic Features: Asmari Formation of the Cheshmeh-Khush Oil Field, SW Iran

Document Type : Research Paper


1 Research Institute of Petroleum Industry

2 School of Geology, University of Tehran


The Oligo-miocene Asmari formation is one of the most important hydrocarbon reservoirs in the southwest of Iran. In order to evaluate reservoir quality and the factors controlling reservoir properties, detailed geological and petrophysical studies were carried out on 242 m of core samples from Asmari reservoir. This study is a part of a larger project that examines depositional history and reservoir properties of the Asmari formation in the Cheshmeh-Khush field. Macroscopic and microscopic studies resulted in the determination of 5 shallow marine carbonate facies (from proximal open marine to tidal setting) and also 5 silisiclastic lithofacies (including channel, barrier, tidal, and shoreface sandstones). Based on the integrated results from sedimentological and paleontological studies, Sr isotopes dating, gamma-ray logs, and seismic data analysis, 5 depositional sequences with constituent system tracts were distinguished.
In this research, the reservoir characterization of the Asmari reservoir were carried out through the integration of geological and petrophysical properties. In the first step, 21 hydraulic flow units (HFU or FU) were identified and then, to achieve better lateral correlation and modeling, HFU’s were merged to 17.
The results from this study showed different behaviors of the silisiclastic and carbonate facies next to the fluid flow. The findings of this study indicate that the lateral and vertical distribution of channel-filled sandstones (such as units 2 and 8) are strongly controlled by the geometry of depositional facies. Thus, the correlation and modeling of flow units, solely on the basis of lithology and thickness, and regardless of facies and its geometry, will cause different facies (such as coastal and channel-filled sandstones) with different geometry, and reservoir quality are placed incorrectly in a single flow unit.
In the carbonate parts of Asmari formation, the effect of diagenetic processes on reservoir quality is much higher than the facies. Hence, the LST limestones of unit 17, as a result of calcite cementation, were changed to a thick, distinct, correlatable, and barrier unit. On the other hand, dolomitic intervals that have not been affected by anhydrite cementation have formed porous and permeable carbonate reservoir units (such as units 18 and 21).


Amaefule J. O., Altunbay M., Tiab. D., Kersey D. G., and Keelan D. K., “Enhanced Reservoir Description: Using Core and Log Data to Identify Hydraulic (Flow) Units and predict permeability in uncored intervals/wells,” SPE 68, Annual Technical Conference and Exhibition, Houston, Texas, 1993.
Orodu O. D., Tang Z., and Fei Q., “Hydraulic (Flow) Unit Determination and Permeability Prediction: A Case Study of Block Shen-95, Liaohe oilfield, North-East China,” Journal of Applied Sciences, 2009, 9, 1801-1816.
Noori Al-Jawad S., Saleh A. H., Al-Dobaj A., and Al-Rawi Y. T., “Reservoir Flow Unit Identification of the Mishrif Formation in North Rumaila Field,” Arabian Journal of Geosciences, 2014, 7, 2711-2728.
Nabikhani N., Moussavi-Harami R., Mahboubi A., Kadkhodaie A., and Yosefpour M. R., “The Evaluation of Reservoir Quality of the Sarvak Formation in One of Oil Fields of the Persian Gulf,” Journal of Petroleum Science and Technology, 2012, 2, 3-15.
Rahimpour-Bonab H., Mehrabi H., Navidtalab A., and Izadi-Mazidi E., “Flow Unit Distribution and Reservoir Modeling in Cretaceous Carbonates of the Sarvak Formation, Abteymour oil Field, Dezful Embayment, SW Iran,” Journal of Petroleum Geology, 2012, 35, 213-236.
Ebanks W. J. Jr., Scheihing M. H., and Atkinson C. D., “Flow Units for Reservoir Characterization,” In: D. Morton-Thompson, A. M. Woods (Eds.), Development Geology Reference Manual, American Association of Petroleum Geoplogists, Methods in Exploration Series, 1992, 10, 282-284.
Moore C. H., “Carbonate Reservoirs: Porosity Evolution and Diagenesis in a Sequence Stratigraphic Framework. Developments in Sedimentology,” Amsterdam, Elsevier, 2001, 55, 444.
Hosseini nia T., “Well Completion Report of Well Cheshmeh Khush-9,” Geology Department, Iranian Central Oil Fields Company, Internal Report, 2006.
Van Buchem F. S. P., Allan T., Lausen G. V. , Lotfpour M., et al., “Sequence Stratigraphy and Sr Isotope Stratigraphy of the Oligo-miocene Deposits in the Dezful Embayment (Asmari and Pabdeh Formations, SW Iran)-implications for reservoir characterization,” 1st International Petroleum Conference, European Association of Geoscientists and Engineers (EAGE), Shiraz, Iran, 2010.
Jong-Se L., “Reservoir Properties Determination Using Fuzzy Logic and Neural Networks from Well Data in Offshore Korea,” Journal of Petroleum Science and Engineering, 2005, 49, 182-192.
Helle H. B., Bhatt A., and Ursin B., “Porosity and Permeability Prediction from Wireline Logs Using Artificial Neural Networks: a North Sea Case Study,” Geophysical Prospecting, 2001, 49, 431-444.
Gunter G. W., Finneran J. M., Hartmann D. J., and Miller J. D., “Early Determination of Reservoir Flow Units Using an Integrated Petrophysical Method,” Society of Petroleum Engineers, SPE Annual Technical Conference and Exhibition, San Antonio, Texas, 1997, 373-380.
Honarmand J., “Sedimentological and Diagenetic Controls on Reservoir Properties of the Asmari Formation, Cheshmeh Khush Oil Field, SW Iran,” Ph.D. Thesis, School of Geology, University of Tehran, Tehran, 2013.
Thomas A. N., “Facies Variation in Asmari limestone,” 18th Inter. Geol. Cong., 1952, 74-82.
Adams T. D., “The Asmari Formation of Lurestan and Khuzestan Provinces, Exploration Directorate,” National Iranian Oil Company, 1969, Report No. 1151.
McCoard D. R., “Regional Geology of the Asmari of Ahwaz and Marun Areas,” Exploration Directorate, National Iranian Oil Company, Internal Report, 1974.
Pairaudeau J. G., “Environmental Analysis of Ahwaz Sands in Lower Asmari Marun Field,” OSCO Technical note, National Iranian Oil Company, Internal Report, 1978.
Seyrafian A. and Hamedani A., “Microfacies and Depositional Environment of the Upper Asmari Formation (Burdigalian) North-Central Zagros Basin, Iran,” Journal of Geological Palaeontology Abh, 1998, 210, 129–141.
Seyrafian A. and Hamedani A., “Microfacies and Palaeoenvironmental Interpretation of the Lower Asmari Formation (Oligocene), North-Central Zagros Basin, Iran,” Journal of Geological Palaeontology Abh, 2003, 3, 164–174.
Aqrawi A. A. M., Keramati M., Ehrenberg S. N., Pickard N., et al., “The Origin of Dolomite in the Asmari Formation (Oligocene-Lower Miocene), Dezful Embayment, Southwest Iran,” Journal of Petroleum Geology, 2006, 29, 381-402.
Vaziri-Moghaddam H., Kimiagari M., and Taheri A., “Depositional Environment and Sequence Stratigraphy of the Oligocene-Miocene Asmari Formation in SW Iran,” Facies, 2006, 52, 41-51.
Honarmand J. and Amini A., “Diagenetic Processes and Reservoir Properties in the Ooid Grainstones of the Asmari Formation, Cheshmeh Khush Oil Field, SW Iran,” Journal of Petroleum Science and Engineering, 2012, 81, 70-79.
Buxton M. W. N. and Pedley H. M., “A Standardized Model for Tethyan Tertiary Carbonate Ramps,” Journal of the Geological Society, 1989, 146, 746-748.
Flugel E., “Microfacies of Carbonate Rocks: Analysis, Interpretation and Application,” Berline, Springer Verlag, 2010, 976.
Ehrenberg S. N., Pickard N. A. H., Laursen G. V., Monibi S., et al., “Strontium Isotope Stratigraphy of the Asmari Formation (Oligocene–Lower Miocene), SW Iran,” Journal of Petroleum Geology, 2007, 30, 107-128.
Hunt D. and Tucker M. E., “Stranded Parasequences and the Forced Regressive Wedge Systems Tract: Deposition during Base-level Fall,” Sedimentary Geology, 1992, 81, 1-9.
Catuneanu O., “Principles of Sequence Stratigraphy,” Amsterdam, Elsevier, 2006, 375.
Lucia F. J., “Carbonate Reservoir Characterization: An Integrated Approach,” Berlin, Springer-Verlag, 2007, 336.