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 ...
Read More
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.
Stratigraphy and Palaeontology
Mahnaz Parvaneh Nejad Shirazi; M. Seddighi; P. Balicheh khorram abadi
Abstract
This study deals with lithostratigraphy, biostratigraphy, microfacies analysis, and depositional setting of the Jahrum Formation in Chellehgah Sepidan section, NW Shiraz. Vertical changes in lithological characteristics led to recognition of 15 lithotypes. The Jahrum Formation, in this area, rests conformably ...
Read More
This study deals with lithostratigraphy, biostratigraphy, microfacies analysis, and depositional setting of the Jahrum Formation in Chellehgah Sepidan section, NW Shiraz. Vertical changes in lithological characteristics led to recognition of 15 lithotypes. The Jahrum Formation, in this area, rests conformably (with a gradational boundary) on the Pabdeh Formation and is overlain unconformably by the Asmari Formation. Micropaleontological analyses based on benthic foraminifera (Nummulites striatus, N. cf. fabianii, N. gr. bullatus-garganicus, Spiroclypeus sp.) suggest a middle-upper Eocene age for the formation. Facies analyses allowed to recognize the 6 facies (including 12 microfacies) for the examined strata. The results also suggest that the Jahrum Formation deposited in a homoclinal ramp.
Sedimentology
naser abdi; Reza Moussavi-Harami
Abstract
The Qatar-Cowbandi arc is a giant regional anticline with northeast- southwest direction, runs through the Qatar peninsula, extends northeastward through the Iranian sector of the Persian Gulf. The arc in the Iranian part is subject of the study meditation. In this paper the interpretation of 2D seismic ...
Read More
The Qatar-Cowbandi arc is a giant regional anticline with northeast- southwest direction, runs through the Qatar peninsula, extends northeastward through the Iranian sector of the Persian Gulf. The arc in the Iranian part is subject of the study meditation. In this paper the interpretation of 2D seismic in the interval of top of Laffan to top of Jahrum formations, allows the regional research of the arc in the study area. Seismic interpretation in both horizons have distinct indications for existing a platform in the area with northwest- southeast direction, which smoothly dipping toward northeast, with some highs resulted from salt diapirs activity. According to isopach map provided for sedimentary sequence of Ilam-Jahrum formations, which was prepared based on 2D seismic data, the sediments thickness decreases in the platform area. The platform is interpreted as crest of arc, on which low rate of sediment precipitation occurred due to low accommodation space, resulted from the arc uplifting activity. Therefore, the arc and also salt diapers, should be considered as regional important factor in sequence stratigraphy study for the precipitated sediments.
S. A. Moallemi; M. H. Adabi; A. Sadeghi
Abstract
In order to determine the depositional environment and age of the carbonaceous Jahrum Formation, benthic foraminiferal assemblage of upper Eocene in the Jahrum Formation carbonates, located in GisakanMountain, 10 km east of the Borazjan city and adjacent fields, were studied. Based on the foraminiferal ...
Read More
In order to determine the depositional environment and age of the carbonaceous Jahrum Formation, benthic foraminiferal assemblage of upper Eocene in the Jahrum Formation carbonates, located in GisakanMountain, 10 km east of the Borazjan city and adjacent fields, were studied. Based on the foraminiferal distribution and abundance, the paleoenvironment were reconstructed. Due to the presence of Nummulites fabianni and based on strontium isotopic analyses, the age between 33.7-35Ma (Priabonian) was determined. The mean sedimentation rate of ~ 2 m/10000 yr. was calculated. This study indicated Asmari Formation deposited after a hiatus, more than four million years (Rupelian stage). Gradual decreases of the sea level and hence the distribution of large benthic foraminifera resulted in the deposition of six sedimentary facies along the inner-middle to outer carbonate ramp system. These facies, from deep to shallow parts of the basin, include argillaceous carbonates containing planktonic foraminifera that were deposited in a hemipelagic to pelagic environment (which is the transition zone from the Pabdeh to Jahrum Formation), carbonate facies of operculina wackestone to packstone related to the outer carbonate ramp, discocyclina /nummulites wackestone to packstone facies deposited in the middle to outer ramp, nummulites wackestone facies occurred in the middle ramp, nummulites orbitolites wackestone to packstone belong to the middle to inner ramp, and finally the orbitolites/bioclast packstone deposited in the inner ramp.
Kh. Khosrotehrani; M. Afghah; V. Ahmadi
Abstract
In this research, two stratigraphic sections were chosen from the late Paleocene to early Miocene (Jahrum and Asmari Formations). These sections includes Sadra and Dodaj plus 645 meters of late Paleocene to early Miocene scdiments. For this investigation 360 thin sections were prepared and 12 samples ...
Read More
In this research, two stratigraphic sections were chosen from the late Paleocene to early Miocene (Jahrum and Asmari Formations). These sections includes Sadra and Dodaj plus 645 meters of late Paleocene to early Miocene scdiments. For this investigation 360 thin sections were prepared and 12 samples analysed by XRF. We studied Biotope that includes biozone. These index biozones and percentage of elements that appears in biotope are identified. Principally index foraminifers, identified in the studied sections, are listed bellow: Miscellanea sp. Kathina sp., Fallotella alavensis Mangin, Opertorbitionlites sp. Alveolina sp. Lituonella ruberti Stache, Rhapydionina urensis Sirel, Orbitolites complanatus Lamark, somalina Stefaninii Silvestri, Dictyoconus sp. Coskinolina liburnica Atache., Nummulites fabianii Prever, Silvestriella tetraedra Gumbel., Nummulites fichteli Michelotti, Austrotrillina howchini Schlumberger, Meandropsina anahensis Henson.
Regarding the frequency, type of wall and biotope percentage ratio of each foraminiferal biozone, there are different biotopes that indicate change in the trend of paleoecologic conditions of the late Paleocene to Oligocene sediments.