Petrophysical evaluation and determination of reservoir rock types in the Ghar member,the Abouzar oilfield, Persian Gulf.
Subject Areas :مهرناز نصیری 1 , محمدرضا رجلی نوده 2
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Keywords: volume of shale porosity water saturation lithology cutoff electrofacies Ghar horizon Abouzar oilfield. ,
Abstract :
This study is aimed at petrophysical evaluation of the Ghar reservoir using Multimin method by Geolog software in five wells from the Abouzar oilfield. For this purpose, well log data comprising of neutron, density, sonic, gamma, resistivity and photoelectric absorption were utilized and their analysis lead to determination of quantitative petrophysical properties such as porosity, volume of shale, water, oil saturation and qualitative parameters including lithology and clay mineral types. The analyses revealed that three zones could be identified in the Ghar reservoir. Meanwhile, there are three shaly interlayers within the Ghar foemation. By application of the cutoff values on oil in place (OIP), petrophysical properties were determined zone by zone and based on Net to Gross ratio (N/G) high reservoir quality zone was identified. Finally by using clustering algorithm, reservoir rock types were identified based upon six properties including density, neutron, gamma ray, volume of shale, water saturation and effective porosity. The facies were introduced on the basis of their priority in reservoir quality so that there is an agreement between petrophysical evaluation results and electrofacies. General lithology of the reservoir in composed of upper loose sands and consolidated sand in the lower part. The lower sands are consolidated by the calcite cement. Overall, the volume of clay minerals in the lower part is less than that of upper part. However, productive zones were separated by a thin shaly layer. The clay minerals type in the shaly layer differs from those present in the reservoir rocks. Total and effective porosity are almost identical which is due to low volume of shale.