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No 17
Vol. 17 No. 9
2019
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In order to identify foraminifera and determine the precise age of lower Cretaceous in Zagros and Central Iran basins, Dariyan Formation in Lar Anticline (north east Gachsaran) and Kolah-Ghazi section (south-east Isfahan province) were measured and investigated. Dariyan Formation in the studied section includes 111 ms of thick, medium to thin layers of limestone, marl and marly limestone. The Lower Cretaceous deposits in Kolah-Ghazi section also is 260 ms thick which includes thick to medium layer limestone and shale. Based on the fossil characteristics and biostratigraphical studies of Lar Anticline section, 28 benthonic foraminifera and 4 planktonic foraminifera have been identified that classified in 4 biozones: Hedbergellids - Orbitolinids assemblage zone, Mesorbitolina texana zone, Mesorbitolina gr. subconcava zone, Favusella washitensis rang zone. In Kolah-Ghazi section (south-east Isfahan), 21 benthonic and 1 planktonic foraminifera have been identified and consequently 2 biozones are recognized as follow: Mesorbitolina texana zone, Mesorbitolina gr. subconcava zonethe studied areas were correlated with some sections of the Dariyan in Kuh-e-Fahliyan, Kuh-e- Mangasht and Meymand. Accordingly, the sedimentation of two studied sections in Lar Anticline and Kolah-Ghazi section were started from Late Aptian which were later than the other sections, and the end of sedimentation in the Kolah-Ghazi section was earlier than the other sections in the Late Aptian age, while the end of sedimentation of Dariyan Formation in other sections was in Early Albian age.
Mahdie Shirzad - Hossein Vaziri-Moghaddam - Ali Seyrafian - Ali Bahrami
Keywords : Dariyan Formation ، Lar Anticline ، Cretaceous sediments ، Kolah Ghazi ، Biostratigraphy
The most seismic activities have observed around and along major fault systems of this zone in NE Iran that involving of an array active right lateral-strike slip faults have distributed by trending NW-SE. neotectonic activity and mechanism changing of faults to reverse trusting faults have caused to increase stress, shortening and increasing seismicity with high density of earthquakes in their ends bending. Structural relation faults between this zone and Binaloud through Meshkan thrusting-transfer zone which is major motion engine of Bakharden-Quchan zone to put it constantly under neotectonic stresses convergence of Arabia-Eurasia plates since last phase Alpine orogeny. In this paper Fractal analysis through box counting method has done and D values change between 0-2. If D closes to zero, faults an earthquakes are focusing in a point with high tension and if D closes to 2 is shown low tension, dispersal faults and earthquakes in whole of region. Both surface/volume fractal dimension distribution show higher seismicity activity in Central and Western parts of Kopeh Dagh in NE Iran.
- abbas kangi - abdolreza jafarian
Keywords : Seismicity ، Seismic Sources ، Fractal Dimension ، Box Counting ، Neotectonic zone of Bakharden-Quchan
Asmari Formation from the Gavarzin gas field have erosional unconformity boundary on marl and pelagic limestones of Pabdeh Formation and gradually change to evaporate cap rock of Gachsaran Formation. Cores studies from the one of wells of Gavarzin field is 183 m in thickness, which includes 1.30 m from the top of Pabdeh, 162.4 m from the Asmari Formation and 19.30 m from the base layers of Gachsaran. Asmari Formation includes alternation of limestone, calcite dolomitic, claystone and shale with green marl. Petrology and facies analysis of the sequence of these formations identified 12 microfacies, a carbonate ramp from deep-sea to sabkha environments and formed in a retrograded sequence. This ramp includes deep environments, open sea, patch reef, bio-, clastic-bars, lagoon and tidal environments, which confirms a changing environment due to rapid facies changes and deposition of evaporative sediments in Gachsaran as a restricted environment. Diagenesis processes are considered as the main factors in carbonate reservoir quality of Gavarzin field. The diagenesis history of the Asmari carbonates of the studied cores is summarized as A) marine phreatic diagenesis, bioturbation, micritization and cementation processes occurred. B) vadose zone diagenesis, where the crystallization, cementation, and dissolution occurred. C) burial diagenesis, comprises compression-induced, pressure dissolution and fracturing are common. The microfacies show a wide varieties of reservoir characteristics and therefore a heterogeneous reservoir has been formed. Micro-fractures, however have strongly influence on the reservoir quality in the section. The simultaneous presence of dissolved spaces and fractures in the reservoir the permeability greatly increased. The best reservoir quality in the Grainstone/Packston facies are coated grains with moldic porosity that were created by the leaching of Ooid-bearing Packston lithology during the diagenesis of atmospheric waters.
Karim Mombani - - Ahmad Yahyaei
Keywords : Asmari Formation, Microfacies, Carbonate Ramp, Diagenesis, Reservoir Quality, Gavarzin gas field
Determining the position of the production zone is one of the best ways to reduce drilling costs as well as quick access to the reservoir and optimal production of hydrocarbon resources. The purpose of this study, is to estimate the porosity, water saturation and thickness of an oil field in Iran’s southwestern Basin , and ultimately to reach the production zone. Therefore, according to the data obtained from 76 wells of this field, variation of reservoir petrophysical parameters were modeled with variogram operation and using Geostatistical methods. By using ordinary Kriging method, the values of the parameters were estimated in the whole field. Subsequently, by using the indicator kriging method, the field boundaries were separated in order to obtain the exact area of the oil zone and the volume of oil in place and finally by considering the 80% probability level, The definite boundary of the presence of the production zone was determined in the block model and In this zone the volume of reservoir’s hydrocarbon was estimated about 147/5 million cubic foot.
Farnaz Saberi - Farhad M. Torab - kioumars Taheri
Keywords : Petrophysical Parameters ، Geostatistics ، Indicator Kriging ، Production Zone ، Southwest Oil basin
In this study Surgah Formation at Maleh-Kuh and Sarkan section in south west of Khoram Abad have been studied based on bio-event models. Surgah Formation at Sarkan well no.1and Maleh-Kuh has 46 and 82-meter thickness respectively and was placed on the Sarvak Formation and under the Ilam Formation. In this study Surgah Formation were composed of shale, limy shale with glauconite and pyrite. In this section two Turonian-Coniacian and Coniacian-Santonian boundaries were recognized in Dicarinella concavata Interval Zone. Based of Heterohelix moremani and FODs Dicarinella concavata and Dicarinella primitiva were detected Turonian-Coniacian boundary. Finally based on LoDs Dicarinella primitiva and Marginotruncana marginata were distinguished Coniacian - Santonian boundary in this section.
Mohamad Hadadi - Mohamad Vahidinia - Mohamad Gharaee - Meysam Shafiee Ardestani
Keywords : Zagros sedimentary basin, Surgah Formation, Planktonic foraminifera bioevents, Turonian-Coniacian boundary

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