Geophysical appraisal of fractured carbonate reservoirs: a case study of Abu Roash D Member, Abu Gharadig Field, Western Desert, Egypt

This paper appraises the carbonate of the Abu Roash “D” Member as a case study for being a potentially fractured oil reservoir inside the Abu Gharadig Field, Western Desert, Egypt. The seismic interpretation revealed an asymmetrical east northeast (ENE)–west southwest (WSW) anticline dissected by several northwest (NW)–southeast (SE) normal faults. This reflects the well-known dextral wrench tectonics that affected the northern portions of the Western Desert through the Late Cretaceous time. The occurrence of fractures inside the carbonate of Abu Roash “D” Member is attributed to the abundance of the interpreted normal faults (extensional regime) in the study area. The qualitative well log assessment for the limestone of Abu Roash “D” in Abu Gharadig-5 Well (AG-5), which has been chosen as a case study in this research, shows that the most promising zone interval (zone I) is located between depths of 9855 and 9887 ft. The quantitative investigation displays that the examined zone has good petrophysical parameters with 0% shale volume, 9% effective porosity, 32% water saturation, and 0.03 bulk volume of water. These low water saturation (Sw) and bulk volume of water (BVW) values were obtained after applying the corrected value of the “m” of the Archie equation, which in the case of fractured porosity, should be less than 2 (m = 1.5 in the present study). Accordingly, using the exact “m” value to assess the oil potentiality of Abu Roash “D” Member in Abu Gharadig Field is vital for obtaining more accurate and reliable values of Sw and BVW.