Journal de géologie et géophysique
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Volumetric Assessment through 3D Geostatic Model for Abu Roash Reservoir in Amana Field-East Abu Gharadig Basin-Western Desert-Egypt

Abu-Hashish MF and Ahmed Said

The main objective of constructing a geostatic model is to determine the 3-D geometry of the reservoir rock and assess its hydrocarbon volumetrics. To achieve this goal, the Amana oil field is taken as a real example. An integrated methodological approach was applied starting with data collection and quality control and then followed by interpretation of the available geological, geophysical and petrophysical data. The field area is located in the most eastern trough of the Abu Gharadig basin in the East Bahariya Concession in the Western Desert of Egypt. The source rock in this area is the Upper Jurassic Khatatba Formation that was deposited in a continental to inner-middle shelf environment. The reservoir rock is Abu Roash “G” sand, one of the seven lithologic members of the Abu Roash Formation. Interpretation of seismic data together with well logs revealed the presence of a horst block, acting as a good structural trap, meanwhile the Abu Roash “F” carbonate and Abu Roash “G” shale are the seal rocks. Well data have shown that the reservoir rock in the Amana field is the Abu Roash “G” Member, which comprises three sand lithologic zones; namely the upper, meddle and lower zones. Of these zones, the middle one is the most attractive and has the best reservoir quality. The shale content in this sand is 8% compared to 13% and 26% in the upper and lower zones. In addition, the net to gross thickness ratio is less than 18%, more than 35%, and about 10% in the upper, middle, and lower zones, respectively. Data analysis also indicates that the upper and lower zones are appreciably water wet. However, the middle sand zone appears to be prospective. The net pay thickness in this zone varies between 10 and 32 ft, porosity 19-22%, water saturation 18-40% and average permeability 40 md. Based on the geostatic model of the Amana field reservoir, it is concluded that this area is a positive prospect in the most eastern part of the Abu Gharadig basin. The volume of oil (STOLIIP) in Amana reservoir is calculated as 10 million barrels, with an initial recoverable oil of 1.4 million barrels.