Document Type : Original Research Paper
Authors
1 Professor, Department of Geology, Faculty of Earth Science, Shahid Chamran University, Ahvaz, Iran
2 M.Sc., Department of Geology, Faculty of Earth Science, Shahid Chamran University, Ahvaz, Iran
Abstract
The main goal of this study is to introduce a paleo high in the central part of Binak oilfield using geochemical parameters. Despite the effect of this phenomena on sedimentation, due to its low amplitude of uplift and lack of unconformity, so far remained unknown in this oilfield. Seismic and well log data reveal that, Binak oilfield is an asymmetrical anticline with Bangestan reservoir of about 22 km long and 10 km wide. To investigate the paleo high in the oil field, geochemical analyses were performed on the cutting samples by Rock Eval 6 Pyrolysis, Vitrinite reflectance measurement and finally Pars Basin Modeler software was used for thermal modeling. The results of Rock-Eval analysis demonstrate that the quantity of total organic carbon decreases in all the Kazhdumi, Lafan, Gurpi and Pabdeh Formations towards the center of this anticline. This phenomenon reveals that the environment and condition of sedimentation have been oxidation and shallow for these formations during their deposit history in the center. This can be explained by development of an uplift along Kharg - Mish basement fault starting at or before Albian to Cenomanian time. The Kazhdumi Formation in well number four indicates a drastic change in the geochemical data in compare to other formations as well as the same formation in well number seven. This can also be correlated to remarkable increase in the activities of Kharg-Mish Fault during Albian. On the other hand significant temperature anomalies are often observed close to the faults and there is a direct relationship between basement fault, high thermal gradient and paleo highs. Therefore, thermal modeling was performed to understand thermal history of this oilfield using PBM (Pars Basin Modeler) software. The results indicate that, the amount of heat flow must be 80, 76, 66 and 60 mW/m2 for well numbers 2, 4, 6 and 7 respectively for achievement of the best fit between calculated Vitrinite reflectances as well as Tmax parameters and the same parameters actually measured by geochemical analyses. Consequently, this study reveals that there is a paleo high in the centre and along the Kharg – Mish Fault of the oil field which caused low content of TOC and naturally lower potential for hydrocarbon generation in the middle part of the oilfield. Finally considering the reservoir in the Binak oilfield, since in the central part is shallower due to the paleo high, there is more Rudist presence and higher oil production in the central part of the oilfield.
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