Stratigraphy and Palaeontology
Behzad Saeedi Razavi; mozhgan rikhtehgarzadeh; saeedeh senemari
Abstract
In order to study the biostratigraphy of Sarvak and Ilam in wells A1 and A2 of Binak oilfield, B of Gachsaran oilfield, C of Aghajari oilfield and D of Rag-Sefid oilfield, numerous thin sections have been studied microscopically In the biostratigraphic study of 5 biozones in the Sarvak and Ilam formations, ...
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In order to study the biostratigraphy of Sarvak and Ilam in wells A1 and A2 of Binak oilfield, B of Gachsaran oilfield, C of Aghajari oilfield and D of Rag-Sefid oilfield, numerous thin sections have been studied microscopically In the biostratigraphic study of 5 biozones in the Sarvak and Ilam formations, the following fields were introduced: 1-Oligostegina flood zone, 2- Nezzazata – Alveolinids assemblage zone, 3- Rudist debris zone, 4 -Nezzazatinella – Dicyclina assemblage zone, 5- Rotalia skourensis – algae assemblage zone and Oligostegina food zone. Based on the study of age of Sarvak Formation from Late Albian to Turonian, and for Ilam Formation from Coniasian to Santonian. Based on the biostratigraphy correlation and thickness analysis of biozones introduced in the two studied formations, the depth of the Zagros basin from northwest to southeast decreases dramatically.
Petroleum geology
B Soleimani; M. S. Ravanshad; Ehsan Larki
Abstract
Petrophysical and lithological parameters study of Ilam reservoir in Ahvaz oil field is the main aim of the present research work. Ilam Formation consisted lithologically of limestone, dolomitic limestone, and less quantity of scattered shales. Facies changes are also observed through the formation. ...
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Petrophysical and lithological parameters study of Ilam reservoir in Ahvaz oil field is the main aim of the present research work. Ilam Formation consisted lithologically of limestone, dolomitic limestone, and less quantity of scattered shales. Facies changes are also observed through the formation. On the basis of petrophysical parameters distribution the reservoir divided into 4 zones. The results indicated that shale volume calculated by CGR log, as a shale index, is less than 10% and so the Ilam reservoir is clean formation. Shale quantity is low in zones 2 and 3 than zones 1 and 4. However, the shale volume is very less but its effect on petrophysical parameters especially porosity and permeability is intense. The Ilam Formation is estimated to have 26.8 % water saturation and 3.3% of irreducible water saturation. Middle part is characterized by low rate of water saturation compared to other parts and along with effective porosity average in the range of 14.7%. Calculated permeability average is 8.3 mD. Permeability variation is indicating a direct relation with the porosity. All these results are emphasized that the middle part (zones 2 and 3) is in better condition in view of oil potential and hydrocarbon reserve in comparing to other parts.
E. Asadi Mehmandosti; Sh. Alivand; H. Ghalavand; A. R. Rostami
Abstract
Nuclear magnetic resonance (NMR) is a test method that has had basic influence on the accuracy of reservoir parameters prediction. In this study, petrophysical properties of the Ilam Formation in one oil field of the Abadan plain were investigated by Nuclear magnetic resonance method, and core analysis ...
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Nuclear magnetic resonance (NMR) is a test method that has had basic influence on the accuracy of reservoir parameters prediction. In this study, petrophysical properties of the Ilam Formation in one oil field of the Abadan plain were investigated by Nuclear magnetic resonance method, and core analysis and thin sections data were used to validate the test results for the first time. The Nuclear magnetic resonance method was used to determine reservoir parameters such as porosity, permeability and rebuilding of capillary pressure curve in studied oil field. Correlation between petrophysical results of Nuclear magnetic resonance method, core data and microscopic thin sections indicates effectiveness of this method in determining the reservoir parameters. In addition, evaluation of the Ilam Formation carbonate with NMR method indicates that the studied reservoir at depths of 2890 to 2846 m has suitable reservoir quality in terms of hydrocarbon storages in studied oil field in Abadan plain.
B Asadi; A Sadeghi
Abstract
For biostratigraphy of the Ilam Formation, in Surgah and Kabirkuh anticlines, 2 sections of Mehdiabad and Holostem - Poshte were selected and sampled. The thickness of the Ilam Formation in Mehdiabad and Holostem - Poshte sections are 183 and 66 meters respectively and main lithology includes limestone, ...
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For biostratigraphy of the Ilam Formation, in Surgah and Kabirkuh anticlines, 2 sections of Mehdiabad and Holostem - Poshte were selected and sampled. The thickness of the Ilam Formation in Mehdiabad and Holostem - Poshte sections are 183 and 66 meters respectively and main lithology includes limestone, shale and argillaceous limestones with intercalation of shale. The lower and upper boundaries of the Ilam Formation with Surgah and Gurpi formations are conformable with sharp lithology changes. For biostratigraphic studies 36, species belong to 15 genus of formaminifera were recognized and 4 biozones based on Premoli Silva &Verga (2004) biozonation were identified. These include:
1. Dicarinellaconcavata zone
2. Dicarinellaasymetrica zone
3. Globotruncanitaelevata zone
4. Globotruncanaventricosa zone
Based on these biozons, the age of the Ilam Formation in both sections is Santonian – early Middle Campanian. In this study, the Ilam Formation in Mehdiabad and Holostem – Poshteh sections were compared with type section.
M Khanjani; S.R Moussavi-Harami; H Rahimpour-Bonab; M.R Kamali; A Chehrazi
Abstract
The Santonian – CampanianIlam Formation is one of the major reservoirs of Bangestan Group in the Zagros petroliferous basin. In the Siri Alvand Oilfield located in the Persian Gulf this formation with a total thickness of 130 m, consists of limestone. In this study, microfacies, depositional environments, ...
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The Santonian – CampanianIlam Formation is one of the major reservoirs of Bangestan Group in the Zagros petroliferous basin. In the Siri Alvand Oilfield located in the Persian Gulf this formation with a total thickness of 130 m, consists of limestone. In this study, microfacies, depositional environments, diagenetic processes and sequence stratigraphy of the Ilam Formaton in Siri Alvand oilfield was studied. Based on thin sections studies, 8 microfacies and 4 facies associations were identified that deposited in a homoclinal carbonate ramp environment. On the basis of petrographic studies, the main diagenetic processes affected these rocks include bioturbation, cementation, dissolution, dolomitization, stylolitization, pyritization and fracturing. The most important cement types in this formation are bladed calcite, fine equant calcite, drusy mosaic calcite, coarse blocky calcite and syntaxial calcite overgrowth. Sequence stratigraphic studies led to recognition of four third order depositional sequences in the Ilam Formation that all of them terminated to the type 1 sequence boundary. Finally, facies and diagenetic processes intensity were studied in each sequence.
L Bakhshandeh; T Mohtat; H Bakhshandeh; S Senmari
Abstract
The Ilam Formation, cropping out in the ZagrosMountain, consists of 195m of cream-colored limestones in the type section, south of Ilam city. This formation has conformable and continuous contacts with the lower Surgah and the upper Gurpi formations. In the present study, 35 foraminifera planktonic species ...
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The Ilam Formation, cropping out in the ZagrosMountain, consists of 195m of cream-colored limestones in the type section, south of Ilam city. This formation has conformable and continuous contacts with the lower Surgah and the upper Gurpi formations. In the present study, 35 foraminifera planktonic species of 17 genus have been identified. The Ilam formation was divided into 4 cosmopolitan biozones on the basis of the planktonic foraminifera which, consist of: Biozone 1-Marginotruncana sigali -Dicarinella primitiva Partial Zone, Biozone 2- Dicarinella concavata Interval Zone, Biozone 3- Dicarinella asymetrica Total -range zone, and Biozone 4- Globotruncanita elevata Partial- range zone. According to these biozones, the Ilam formation was deposited from the late middle Turonian to the early Campanian.
S. Senemari; Sh. Hasanpour
Abstract
Calcareous Nannofossils are good tool for biostratigraphy, especially in the Late Cretaceous. With respect to this and due to the lack of any precise paleontological study, the calcareous nannofossils of Ilam and Gurpi Formations were investigated in the Southwestern Sarvestan. These Formations consists ...
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Calcareous Nannofossils are good tool for biostratigraphy, especially in the Late Cretaceous. With respect to this and due to the lack of any precise paleontological study, the calcareous nannofossils of Ilam and Gurpi Formations were investigated in the Southwestern Sarvestan. These Formations consists of marl, clay limestone and shale. In this study, for the first time, 14 families, 22 genera and 39 species of nannofossils were identified. Based on the information obtained on nannofossils, the section is aged at Late Coniacian-Early Santonian to Early Maastrichtian corresponding to CC14-CC24 zones (Sissingh, 1977).
Kh. Khosrotehrani; D. Baghbani; F. Keshani; M. Omrani
Abstract
In order to study Biostratigraphy of Cenomanian – Late Campanian deposits (upper part of Sarvak Fm.,Ilam Fm. and lower part of Gurpi Fm.), kuhe Assaluyeh stratigraphic section selected. Sediments of this interval consist of limestone, argillaceous limestone and marl with thickness of 162 m. In ...
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In order to study Biostratigraphy of Cenomanian – Late Campanian deposits (upper part of Sarvak Fm.,Ilam Fm. and lower part of Gurpi Fm.), kuhe Assaluyeh stratigraphic section selected. Sediments of this interval consist of limestone, argillaceous limestone and marl with thickness of 162 m. In this section Ilam Fm. in age of Santonian overlies Sarvak Fm. disconformably and is underlain by Gurpi Fm. conformably. By micropaleontological study on 55 thin sections, 5 genus and 9 species of planktonic and 16 genus and 13 species of benthic foraminifers were identified. Among distinguished foraminifers, Rotaliidae family forms were studied carefully and revised. It should be mentioned that, 5 genus and 6 species of benthic foraminifers (Rotaliid forms) were recognized in Iran for the first time (in Assaluyeh section) which consist of: Rotorbinella mesogeensis,Rotorbinella campaniola,Iberorotalia reicheli,Calcarinella schaubi, Pararotalia tuberculifera and Pyrenerotalia longifolia. Santonian age was determined for Ilam Fm. by identified foraminifers. In studied section, stratigraphy development of benthic foraminifers was compared by Martinez Biozones Martinez (2007). This biozones were presented on the base of Rotaliid forms for Pyrenees area in Spain. By this comparison, four biostratigraphy zones for upper part of Sarvak and Ilam Fm. are suggested.
J. Daneshian; D. Baghbani; Kh. Khosrow- Tehrani; L. Fazli
Abstract
In this study, foraminifera of the Ilam and Gurpi Formations, from Kuh-e- Assaluyeh section in east Kangan port in Boushehr province and Ivan well in Persian Gulf are investigated. Ilam Formation in Kuh-e-Assaluyeh section with 30 meter thickness and Ivan well with 68 meter thickness composed of limestone ...
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In this study, foraminifera of the Ilam and Gurpi Formations, from Kuh-e- Assaluyeh section in east Kangan port in Boushehr province and Ivan well in Persian Gulf are investigated. Ilam Formation in Kuh-e-Assaluyeh section with 30 meter thickness and Ivan well with 68 meter thickness composed of limestone and dolomitic limestone. The Ilam Formation in the study sections overlies unconformable the Sarvak Formation and underlies the Gurpi Formation. The Gurpi Formation in Kuh-e-Assaluyeh with 73 meter thickness and Ivan well with 56 meter thickness composed of argillaceous limestone, sandy limestone, shale and limestone. Also the Gurpi Formation in Kuh-e-Assaluyeh section and Ivan well overlies unconformable the Ilam Formation and underlies the Pabdeh Formation. The study of 70 samples from the examined section led to the identification of 13 genera and 19 species of planktonic foraminifera and 12 genera and 12 species of benthonic foraminifera. Planktonic foraminifera are as follow: Heterohelix globolusa, Macroglobigerinelloides ultramicrus, Globotruncanita elevata, Globotruncana bulloides, Globotruncana ventricosa, Muricohedbergella holmdelensis, Heterohelix striata, Macroglobigerinelloides prairiehillensis, Contusotruncana fornicata, spiropelecta sp., Rugoglobigerina rugosa Macroglobigerinelloides bollii, Muricohedbergella monmouthensis, Globotruncana falsostuarti, Gansserina gansseri, Archaeoglobigerina blowi, Globotruncana arca, Contusotruncana contusa, and benthonic foraminifera are as follow : Rotalia sp., Rotalia skourensis, Pseudedomia sp., Minouxia sp., Dicyclina schlumbergeri, Quinqueloculina sp., Marssonella sp., Gavelinela sp., Archaecyclus midorientalis, Ammobaculites sp. On the basis of stratigraphic distribution of index foraminifera, the Ilam Formation belongs to Santonian to Campanian, and the Gurpi Formation in Kuh-e-Assaluyeh section is Campanian to Maastrichtian and in Ivan well is Maastrichtian in age. The studies in Kuh-e-Assaluyeh section let to recognition four foraminifera zone from base to top: Globotruncanita elevata Zone, Globotruncana ventricosa Zone, Globotruncana falsostuarti Zone, Gansserina gansseri Zone. Lacking the main elements of Globotruncanella havanensis and Globotruncana aegyptiaca biozones caused that Globotruncana falsostuarti biozone is introduced on the basis of the first occurances of Globotruncana falsostuarti (at the base) and Gansserina gansseri (at the top). Also in Ivan well, Globotruncana falsostuarti Zone, Gansserina gansseri Zone, Contusotruncana contusa Zone were identified. Abathomphalus mayaroensis in absent at Ivan well and Kuh-e-Assaluyeh. Thus, Abathomphalus mayaroensis biozone is not recognizable, and instead of it Contusoutruncana contusa biozone is introduced. The boundaries of this biozone are identified by the first and last occurrences of Contusoutruncana contuse. Also comparison this study with Biozonation of Wynd, (1965), from base to top: 1-Rotalia sp. 22, Algae assemblage zone, 2- Archaecyclus midorientalis-Pseudedomia sp.assemblage zone, 3- Globotruncanita elevata zone, 4- Globotruncanita stuarti-Pseudotextularia variance assemblage zone. 5- Contusoutruncana contusa zone.
S.H. Vaziri; D. Jahani; M. Safdari; F. Chegeni
Abstract
The Ilam Formation in southwestern Khorram Abad with a thickness of up to 204 meters consists of uniform limestones with Middle Turonian to Early Campanian age which were deposited in a continuous sedimentation process. In this section, the Ilam Formation has continuous ...
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The Ilam Formation in southwestern Khorram Abad with a thickness of up to 204 meters consists of uniform limestones with Middle Turonian to Early Campanian age which were deposited in a continuous sedimentation process. In this section, the Ilam Formation has continuous and transitional contacts with the Sourgah Formation in the lower boundary and the Gurpi Formation in the upper boundary. In the present study, 9 genera, 30 species and 2 biozones of the planktonic foraminifera have been recognized. The Ilam Formation in the studied section consists of a shaly facies and three carbonatic microfacies include mudstone, wackestone and packstone containing planktonic foraminifera. Shaly facies and mentioned microfacies were deposited in deep-open marine, which formed in a quiet environmental condition and increased environmental energy in microfacies with mudstone texture toward microfacies with wackestone and packstone textures. Whereas in the studied section recognized microfacies are not related to parts of continental shelf,such as ; bar, lagoon and tidal flat, therefore it could be said that, the studied area was part of profound depositional basin in Middle Turonian to Early Campanian.
