Stratigraphy and Palaeontology
marjan zadesmaeil; Mahmoud Reza Majidifard; Seyed Hamid Vaziri; Davood Jahani
Abstract
The Middle and Upper Jurassic sedimentary well successions is located in the northwestern Damghan, (eastern Alborz range). The Dalichai Formation with a thickness of 618 meters in the studied section consists of marl, limestone and marly limestone. The lower boundary with the siliciclastic of the underlying ...
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The Middle and Upper Jurassic sedimentary well successions is located in the northwestern Damghan, (eastern Alborz range). The Dalichai Formation with a thickness of 618 meters in the studied section consists of marl, limestone and marly limestone. The lower boundary with the siliciclastic of the underlying Shemshak Formation is unconformable and in the upper boundary is gradually covered by the Lar Formation. From studied section, altogether 371 fossile sample were collected of which 15 sample were related to other taxon (Bellemnite, Bivalve, Coral and Sponge). Altogether, 51 species of ammonites from the Dalichai Formations belonging to 25 genera and 9 families and 14 zones are described. The following families are reported: Phylloceratidae, Lytoceratidae, Haploceratidae, Oppeliidae, Parkinsoniidae, Morphoceratidae, Reineckeiidae, Perisphinctidae and Aspidoceratidae.Based on ammonites, the Dalichai Formation ranges from the Upper Bajocian to Lower Kimmeridgin and can be subdivided, from bottom to top, into six informal members.Palaeobiogeographically the ammonite fauna is closely related to that of the sub-Mediterranean Province of the northwestern Tethys.
Sedimentology
Elmira Shahkaram; Mohammad Hosein Adabi; Davood Jahani; Seyed Hamid Vaziri
Abstract
The Dalichai Formation is the first rock unit of the Middle Jurassic in the Alborz sedimentary basin that has occurred in a marine environment. The boundary of the Dalichai formation with Shemshak Formation is erosional unconformable while it is concordant with Lar formation. Due to lithological similarity, ...
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The Dalichai Formation is the first rock unit of the Middle Jurassic in the Alborz sedimentary basin that has occurred in a marine environment. The boundary of the Dalichai formation with Shemshak Formation is erosional unconformable while it is concordant with Lar formation. Due to lithological similarity, the boundary of the Dalichai formation with the Lar formation is unclear. It is also very difficult to identify the primary carbonates mineralogy, due to the effects of diagenetic processes solely on the basis of petrographic studies. We studied a section of Sharaf mountain with a thickness of 1420m and 149 samples was studied. The study of the major and minor elements, the Oxygen and Carbon isotopes, and plotting of these values against each other represents that the Dalichai formation have had original aragonite mineralogy, and the nonmarine diagenesis have had the highest impact on them. Plotting the Sr/Ca ratio versus Mn value, shows that these carbonates are affected in a semi-closed to open diagenetic system. Using Sr, Sr/Na, Sr/Ca, Oxygen and Carbon isotopes, the boundary of this formation with the Lar Formation is recognized in thickness of 1200m. The diagenetic environment temperature for this section limestones is 32.9ºC.
Sedimentology
keyvan ahzan; Nader Kohansal Ghadimvand; Seyed Mohsen Aleali; Davood Jahani
Abstract
The Jahrum Formation (Paleocene-Mid Eocene) is one of the most important reservoir units in the Zagros basin and the Persian Gulf. The thickness of this formation in Binaloud oil field in Persian Gulf, which mainly consists of limestones and Dolomites, is about 660 meters. In this research, depositional ...
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The Jahrum Formation (Paleocene-Mid Eocene) is one of the most important reservoir units in the Zagros basin and the Persian Gulf. The thickness of this formation in Binaloud oil field in Persian Gulf, which mainly consists of limestones and Dolomites, is about 660 meters. In this research, depositional environment, sequence stratigraphy and effective diagenesis processes on Reservoir quality of the Jahrum Formation were investigated in Binaloud oil field. The Jahrum succession, which consists of crystalline limestones and dolomites, is overlain by the Asmari Formation and is underlian by the Tarbur Formation unconformably. According to study of cutting samples, eleven microfacies that were deposited in four facies belts, have determined . The most important diagenetic process that was observed in this formation as follows: bioturbation, cementation, dolomitization, dissolution, porosity generation and fracture systems wich is worthy to mation bioturbation and anhydrite cement causes the reduce of reservoir quality and dolomitization , dissolution and secondary porosity causes the reservoir quality. improvement most of facies jahrum formation are mud supported and have very low primary porosity. According to sequence stratigraphy studies, a third order sedimentary sequence with type SB1 boundary was identified in Jahrum subsurface succession.
behnam pashazadeh; Davood Jahani; razieh Lak; Hamid nazari; masoud zamani pedram
Abstract
The purpose of this research is to identify quaternary units and determine the sediment boundaries around Yazd city in Central Iran. The origin of Quaternary sediments is mainly related to erosion of the Triassic, Cretaceous, and Palaeozoic units. Based on the results of sedimentation, six types of facies ...
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The purpose of this research is to identify quaternary units and determine the sediment boundaries around Yazd city in Central Iran. The origin of Quaternary sediments is mainly related to erosion of the Triassic, Cretaceous, and Palaeozoic units. Based on the results of sedimentation, six types of facies were identified as Mud, silt, sandy silt, silty sand, mud sands and sandy mud. The XRD results of the samples show that these specimens consist mainly of quartz, calcite, dolomite, feldspar, coperite and clay minerals. In the fossil studies of two important species of ostracodes called Ilyocypris sp. Which refers to sweet waters and Candona .sp, which relate to various saline waters. Due to the diversity of facies and fossils, approximately the lake in the study area was developed in late Quaternary. Facies characteristics, the type of minerals and index fossils indicate that the sedimentation of these facies in a sedimentary lake environment that was first identified in the study area.
Petroleum geology
Bita Arbab; Davood Jahani; Bahram Movahed
Abstract
The Aptian Shuaiba deposits, in southeastern of Persian Gulf due to having resistivity less than 6 to 1 ohm.m, is considered as low resistivity pay zone. On the basis of experimental studies 8 microfacies defined which settled in a carbonate platform of homoclinal ramp model that belong to outer, ...
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The Aptian Shuaiba deposits, in southeastern of Persian Gulf due to having resistivity less than 6 to 1 ohm.m, is considered as low resistivity pay zone. On the basis of experimental studies 8 microfacies defined which settled in a carbonate platform of homoclinal ramp model that belong to outer, middle, inner ramp. Existence micro porosity in the microfacies is main reason for lowering resistivity. Various digenetic process are seen such as micritization and pyritization which have noticeable impact on declining resistivity. Lønøy method applied to address pore throat sizes which contain Intercrystalline porosity, Chalky limestone, Mudstone micro porosity. Pore systems are at class 3 Lucia. NMR logs and core data have been used for defining reliable water saturation and reservoir characterization. Results explain that decreasing of resistivity in pay zone is related to texture and grain size variation not being existence of moved water .Irreducible water estimate for this reservoir between 30 to 50 %.