Dolomitization models and related fluid evolution in the carbonate platform of the Asmari Formation

Document Type : Original Article

Authors

1 National Iranian South Oil Company, Ahvaz, Iran

2 Department of Petroleum and Sedimentary Basins, Faculty of Earth Sciences, Shahid Beheshti University, Tehran, Iran

3 Department of Geology, Faculty of Science, University of Tehran, Iran

4 Department of Geology, Faculty of Science, Ferdowsi University of Mashhad, Iran

Abstract

Introduction
The Oligocene-Miocene dolomitized Asmari Formation has expanded all over the Arabian plate with numerous supergiant and giant hydrocarbons in SW Iran, Iraq, Saudi Arabia, and the United Arab Emirates. Concertedly, the Asmari Formation and age-equivalents in adjacent areas of Middle East include more than 90% of recoverable oil reservoirs (Ghazban, 2007). The best reservoir units of this succession occurs within dolomitic parts exhibiting better reservoir quality than do the intercalated limestones and silisiclastics. Dolomite sequences play an important role in the production of oil and gas in the world's major hydrocarbon basins (Fallah-Bagtash et al, 2020; Noorian et al, 2020; Omidpour et al, 2021; 2022; Fallah-Bagtash et al, 2022). Similarly, in the Asmari reservoir with poor primary reservoir properties, fracturing and dolomitization enhanced porosity and permeability and thus hydrocarbon production (Aqrawi et al, 2006). Shadegan Oil Field is one of the important oilfields of Iran, due to its carbonate- siliciclastic nature, different parts of this formation have been exposed to the process of dolomitization. This has led to the development of porosity and permeability in its different parts. Therefore, in this research, using various data such as detailed petrographic studies along with geochemical studies of dolomites, the dolomites types of the Asmari Formation in the Shadegan Oil Field, dolomitization models, diagenetic history, diagenetic alteration and evolution of dolomitized fluids have been discussed. The results of this study can finally be used to evaluate the effect of dolomitization on the reservoir potential of Asmari Formation in this field.
 
Materials and Methods
The present study is based on a petrographic analysis of 1123 thin sections from cores of five wells drilled in the Asmari Formation. All thin sections were stained with potassium ferricyanide and Alizarin Red-S to distinguish carbonate minerals (Dickson, 1965). Dolomites are classified based on dolomite-rock texture classification presented by Sibley and Gregg (1987), Mazzullo (1992) and Chen et al. (2004). Facies analysis and interpretation of the depositional environment was performed using by Burchette and Wright (1992) and Flügel (2010) schemes. Ten uncovered thin sections were also analyzed by cathodoluminescence microscopy. These analyses took place at the Central Laboratories of Ferdowsi University of Mashhad, Iran. Ten gold-coated samples were analyzed with backscattered electron imaging using a Scanning Electron Microscope (SEM) in order to evaluate dolomite types, crystal sizes, micro-textures and pore spaces. Finally, thirty-two dolomitic samples were analyzed for their trace and major element contents using atomic absorption spectrophotometry (AAS) at the Ferdowsi University of Mashhad, Iran. 
Results and Discussion
The Asmari Formation, in Shadegan Oil Field, with Oligocene-Miocene age, consists of carbonate unit and siliciclastic intervals, which is mainly composed of medium to thick layered limestone and dolomite with interlayers of shale and sandstone. Detailed description of the core samples along with petrographic studies of the Asmari succession led to the identification of 26 carbonate-evaporite microfacies. In general, mineralogical, geochemical, and especially the interaction of facies with the distribution of dolomite indicates dolomitization by five different mechanisms/models in the carbonate platform of the Asmari Formation. These models include: Sabkha model, Seepage-reflux model, Meteoric-mixing zone model, Burial model and Bacterial mediation model. Dolomitization, as the most important diagenetic process in the depositional sequence of the Asmari Formation, has formed in several diagenetic environments, including syndepositional diagenetic realm (near surface), shallow burial, and intermediate to deep burial.
 
Conclusion
Four texturally and geochemically different types of dolomite include D1 (<10 μm, fabric-retentive), D2 (16-62 μm, fabric-retentive), D3 (62-250 μm, fabric destructive), and D4 (150-250 μm, fabric destructive). The lateral and vertical heterogeneity in dolomite percent indicates that the Asmari reservoir was subject to the multiple dolomitizations that could be categorized by five models in the near-surface to deep burial environments. Thin-layered sabkha dolomites (D1) are formed at or just below the sediment-water interface in mud-supported facies soon after deposition or during shallow burial. The matrix dolomites (D2 and D3) are the most abundant type of dolomites with the most contribution to reservoir porosity. They were formed during intermediate burial stages of the Asmari succession, indicated by their close association with the formation of an early generation of stylolites and fairly high iron concentration. These dolomites formed from warmer and more saline basinal fluids and/or from the dissolution of high-magnesium calcite or earlier dolomites, or recrystallization of D1. The D4 and other dolomites associated with the shaley facies, formed in a deeper burial setting by hydrothermal processes, utilizing hot and slightly-saline fluids that were affected by brine enrichment.

Keywords

Main Subjects

References

Adabi, M.H., 2009. Multistage dolomitization of the Upper Jurassic Mozduran Formation, Kopeh dagh Basin, NE Iran: Carbonates and Evaporites, v. 24, p. 16-32.
Ahmad, A.H.M., Bhat, G.M. and Azim Khan, M.H., 2006. Depositional environments and diagenesis of the Kuldhar and Keera Dome carbonates (Late Bathonain-Early Callovian) of Western India: Journal Asian Earth Sciences, v. 27, p. 765-778.
Al-Aasm, I.S., 2003. Origin and characterization of hydrothermal dolomite in the Western Canada.
Al-Aasm, I.S. and Packard, J.J., 2000. Stabilization of early-formed dolomite: a tale of divergence from two Mississippian dolomites, Sedimentary Geology, v. 131, p. 97-108.
Al-Aasm, I.S., Ghazban, F. and Ranjbaran, M., 2009. Dolomitization and related fluid evolution in the Oligocene–Miocene Asmari Formation, Gachsaran area, SW Iran: petrographic and isotopic evidence, Petroleum Geology, v. 32(3), p. 287-304.
Aqrawi, A.A.M., Keramati, M., Ehrenberg, S.N., Pickard, N., Moallemi, A., Svana, T., Darke, G., Dickson, J.A.D. and Oxtoby, N.H., 2006. The origin of dolomite in the Asmari formation (Oligocene‐lower Miocene), Dezful embayment, SW Iran. Petroleum Geology, v.  29, p. 381-402.
Aqrawi, A.A. and Wennberg, O.P., 2007. The Control of fracturing and dolomitisation on 3D reservoir property distribution of the Asmari Formation (Oligocene-Lower Miocene), Dezful Embayment, SW Iran. In IPTC 2007: International Petroleum Technology Conference, p. cp-147. European Association of Geoscientists & Engineers.
Azomani, E., Azmy, K., Blamey, N., Brand, U. and Al-Aasm, I., 2013. Origin of Lower Ordovician dolomites in eastern Laurentia: controls on porosity and implications from geochemistry, Marine and Petroleum Geology, v. 40, p. 99-114.
Bordenave, M.L. and Hegre, J.A., 2010. Current distribution of oil and gas fields in the Zagros Fold Belt of Iran and contiguous offshore as the result of the petroleum systems: Geological Society Special Publication, v. 330, p. 291-353.
Burchette, T.P. and Wright, V.P., 1992. Carbonate ramp depositional systems: Sedimentary Geology, v. 79, p. 3-57.
Chen, Y.J., Pirajno, F. and Sui, Y.H., 2004. Isotope geochemistry of the Tieluping silver-lead deposit, Henan, China: A case study of orogenic silver-dominated deposits and related tectonic setting, Mineralium Deposita, v. 39, p. 560-575.
Fallah Bagtash, R., Adabi, M., Sadeghi, A. and Omidpour, A., 2021. A Study of microfacies and diagenetic processes of the Asmari Formation in Khesht Oil Field with emphasis on reservoir characteristic: a case study from Zagros basin, Fars, SW Iran, Journal of Stratigraphy and Sedimentology Researches, v. 37(3), p. 1-34.
Fallah-Bagtash, R., Adabi, M.H., Nabawy, B.S., Omidpour, A. and Sadeghi, A., 2022. Integrated petrophysical and microfacies analyses for a reservoir quality assessment of the Asmari Dolostone sequence in the Khesht Field, SW Iran: Journal of Asian Earth Sciences, v. 223, p. 104-123.
Fallah-Bagtash, R., Jafarian, A., Husinec, A. and Adabi, M.H., 2020. Diagenetic stabilization of the Upper Permian Dalan Formation, Persian Gulf Basin, Journal of Asian Earth Sciences, v. 189, p. 104144.
Flügel, E., 2010. Microfacies Analysis of Limestones, Analysis Interpretationand Application, Springer-Verlag, 976 p.
Ghazban, F., 2007. Petroleum Geology of the Persian Gulf. Tehran University, Tehran, 717 p.
Gregg, J.M. and Sibley, D.F., 1984. Epigenetic dolomitization and the origin of xenotopic dolomite texture, Journal of Sedimentary Research, v. 54, p. 908-931.
Heydari, E., 2008. Tectonics versus eustatic control on super sequences of the Zagros Mountains of Iran: Tectonophysics, v. 451, p. 56-70.
Honarmand, J. and Amini, A., 2012. 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, v. 81, p. 70-79.
Hou, Y., Azmy, K., Berra, F., Jadoul, F., Blamey, N.J., Gleeson, S.A. and Brand, U., 2016. Origin of the Breno and Esino dolomites in the western Southern Alps (Italy): Implications for a volcanic influence, Marine and Petroleum Geology, v. 69, p. 38-52.
Huang, S.J., 2010. Carbonate Diagenesis. Geological Publishing, 29-44 p.
Humphrey, J.D., 1988. Late Pleistocene mixing-zone dolomitization, southeastern Barbados, West Indies, Sedimentology, v. 35, p. 327-348.
Jafarian, A., Fallah-Bagtash, R., Mattern, F. and Heubeck, C., 2017. Reservoir quality along a homoclinal carbonate ramp deposit: The Permian upper dalan formation, south pars field, Persian Gulf basin, Marine and Petroleum Geology, v. 88, p. 587-604.
James, G.A. and Wynd, J.G., 1965. Stratigraphic Nomenclature of Iranian Oil Consortium Agreement Area. AAPG Bulletin, v. 49(12), p. 55-56.
Khazaie, E., Noorian, Y., Moussavi-Harami, R., Mahboubi, A., Kadkhodaie, A. and Omidpour, A., 2022. Electrofacies modeling as a powerful tool for evaluation of heterogeneities in carbonate reservoirs: A case from the Oligo-Miocene Asmari Formation (Dezful Embayment, southwest of Iran), Journal of African Earth Sciences, v. 195, p. 134-151.
Krause, S., Liebetrau, V., Gorb, S., Sanchez-Roman, M., McKenzie, J.A. and Treude, T., 2012. Microbial nucleation of Mg-rich dolomite in exopolymeric substances under anoxic modern seawater salinity: New insight into an old enigma. Geology, v. 40 (7), p. 587-590.
Machel, H.G., 1987. Saddle dolomite as a by-product of chemical compaction and thermochemical sulfate reduction. Geology, v. 15, p. 936-940.
Machel, H.G., 2004. Concepts and models of dolomitization: a critical reappraisal, Braithwaite, C.J.R., Rizzi, G., and Darke, G., (Eds.): The Geometry and Petrogenesis of Dolomite Hydrocarbon Reservoirs, Geological Society of London, Special Publication, v. 235, p. 7-63.
Mahboubi, A., Nowrouzi, Z., Al-Aasm, I.S., Moussavi-Harami, R. and Mahmudy-Gharaei, M.H., 2016. Dolomitization of the Silurian Niur Formation, Tabas block, east central Iran: Fluid flow and dolomite evolution. Marine and Petroleum Geology, v.  77, p. 791-805.
Mazzullo, S.J., 1992. Geochemical and neomorphic alteration of dolomite: A review. Carbonates and Evaporites, v. 7, p. 21-37.
Mazzullo, S.J., 2000. Organogenic dolomitizationl in peritidal to deep-sea sediments, Journal of Sedimentary Research, v. 70, p. 10-23.
Milliman, J.D., 1974. Marine Carbonates Recent Sedimentary Carbonates, Part 1: Springer-Verlag, Berlin, 375 p.
Moore, C.H., 2001. Carbonate Reservoirs: Porosity Evolution and diagenesis in a sequence stratigraphic framework, Development in Sedimentology, Elsevier, Amsterdam, v. 55, 460 p.
Morrison, J.O. and Brand, U., 1986. Geochemistry of Recent marine invertebrates: Geoscience Canada, v. 13, p. 237-254.
Mouthereau, F., Lacombe, O. and Verges, J., 2012. Building the Zagros collisional orogen: timing, strain distribution and the dynamics of Arabia/Eurasia plate convergence, Tectonophysics, v. 532-535, p. 27-60.
Nemati, M. and Pezesh, H., 2005. Spatial distribution of fractures in the Asmari formation of Iran in subsurface environment: Effect of lithology and petrophysical properties, Natural Resources Research v. 14 (4), p. 305-316.
Noorian, Y., Moussavi-Harami, R., Mahboubi, A., Kadkhodaie, A. and Omidpour, A., 2020. Assessment of heterogeneities of the Asmari reservoir along the Bibi Hakimeh anticline using petrophysical and sedimentological attributes: southeast of Dezful Embayment, SW Iran, Journal of Petroleum Science and Engineering, v. 193, doi.org/10.1016/j.petrol.2020.107390.
Noorian, Y., Moussavi-Harami, R., Hollis, C., Reijmer, J.J., Mahboubi, A. and Omidpour, A., 2022. Control of climate, sea-level fluctuations and tectonics on the pervasive dolomitization and porosity evolution of the Oligo-Miocene Asmari Formation (Dezful Embayment, SW Iran), Sedimentary Geology, v. 427, p. 1-24.
Omidpour, A. and Fallah-Bagtash, R., 2022. Investigation of sedimentary facies and geochemical parameters of the Asmari Formation (Oligocene-Miocene) in the Shadegan Oil Field, Dezful Embayment, SW Iran, Researches in Earth Sciences, v. 13(2), p. 162-188.
Omidpour, A., Mahboubi, A., Moussavi-Harami, R. and Rahimpour-Bonab, H., 2022. Effects of dolomitization on porosity–Permeability distribution in depositional sequences and its effects on reservoir quality, a case from Asmari Formation, SW Iran, Journal of Petroleum Science and Engineering, v. 208, p. 57-81.
Omidpour, A., Moussavi-Harami, R., Mahboubi, A. and Rahimpour-Bonab, H., 2021. Application of stable isotopes, trace elements and spectral gamma-ray log in resolving high-frequency stratigraphic sequences of a mixed carbonate-siliciclastic reservoirs. Marine and Petroleum Geology, v. 125, doi.org/10.1016/j.marpetgeo.2020.104854
Rahimi, A., Adabi, M.H., Aghanabati, A., Majidifard, M.R. and Jamali, A.M., 2016. Dolomitization Mechanism Based on Petrography and Geochemistry in the Shotori Formation (Middle Triassic), Central Iran, Open Journal of Geology, v. 6, p. 1149-1168.
Rahimpour-Bonab, H., Esrafili-Dizaji, B. and Tavakoli, V., 2010. Dolomitization and anhydrite precipitation in Permo-Triassic carbonates at the South Pars Gas Field, offshore Iran: controls on reservoir quality. Petroleum Geology, v. 33, p. 43-66.
Rao, C.P., 1996. Modern Carbonates, Tropical, Temperate, Polar: Introduction to Sedimentology and Geochemistry: Hobart (Tasmania), 206 p.
Rivers, J.M., Kurt Kyser, T. and James, N.P., 2012. Salinity reflux and dolomitization of southern Australian slope sediments: the importance of low carbonate saturation levels. Sedimentology, v. 59, p. 445-465.
Sabbagh-Bajestani, M., Mahboubi, A., Al‐Aasm, I., Moussavi‐Harami, R. and Nadjafi, M., 2018. Multistage dolomitization in the Qal'eh Dokhtar Formation (Middle‐Upper Jurassic), Central Iran: petrographic and geochemical evidence, Geological Journalm, v. 53, p. 22-44.
Sharland, P.R., Archer, R., Casey, D.M., Davies, R.B., Hall, S.H., Heward, A.P., Horbury, A.D. and Simmon, M.D., 2001. Arabian Plate sequence stratigraphy. GeoArabia, v. 2, p. 371.
Sharland, P.R., Casey, D.M., Davies, R.B., Simmons, M.D. and Sutcliffe, O.E., 2004. Arabian plate sequence stratigraphy - revisions to SP2: GeoArabia, v. 9, p. 199-214.
Sibley, D.F. and Gregg, J.M., 1987. Classification of dolomite rock textures, Journal of Sedimentary Research, v. 57(6), p. 967-975.
Swart, P.K., 2015. The geochemistry of carbonate diagenesis: The past, present, and future, Sedimentology, v. 62, p. 1233-1304.
Tucker, M.E. and Wright, V.P., 1990. Carbonate Sedimentology: Blackwell Scientific Publications, Oxford, 404 p.
Warren, J.K., 2006. Evaporites: sediments, resources and hydrocarbons, Springer Verlag, 1035 p.
Wang, L., He, J., Ni, J.E., Yi, S., Wang, X., Sun, F. and Li, C., 2021. Reservoir Characteristics and Main Controlling Factors in Mixed Sedimentary Background: A Case Study from Asmari Formation of N Oilfield, Middle East. In Proceedings of the International Field Exploration and Development Conference 2020, Springer Singapore, p. 1713-1725.

Files

Share

How to cite

Statistics