Unlocking subtle hydrocarbon plays through 3D seismic and well control: A case study from west Gebel El Zeit district, southwest Gulf of Suez, Egypt

Abstract

© 2015 Society of Petroleum Engineers. All rights reserved. The area of study covers the trough and the eastern flank of the Gemsa basin, which is located in the southwestern onshore part of the Gulf of Suez. Bad quality of traditional 2D seismic data and following classical exploration concept of drilling structural highs were resulted in several dry holes and hence, the area suffered from lost hydrocarbon interest for several years. Recently acquired 3D seismic data progressed the imaging of deeper hanging wall structures and improved the understanding of the area. Changing the exploration concept by drilling hanging-wall traps resulted in few oil fields discoveries and revived the further exploration efforts in the area. This work is an attempt to realize the hydrocarbon trapping mechanism and the main controlling factors of reservoir distribution in the study area through seismic data interpretation and analysis of borehole data in an integration with the surface geology. The main reservoir in the study area is represented by thin sandstone intervals of Middle Miocene age imbedded in a thick shale and marl section of the Kareem Formation. This formation is sporadically cropping-out in the hogback of the prominent Gebel El Zeit ridge before its submergence due SW for a depth of 14,000 feet in the trough of the Gemsa basin. This major subsidence in a distance of around 8 kilometers was accessed by a complex fault system. 3D seismic-imaging and interpretation provided more coherent pattern of this fault complex and the intimate relations of fault linkage and transfers. NW-trending Clysmic faults were traced along the ramp of the Gemsa trough-Gebel El Zeit ridge. Toward the trough, these faults are linked with N65°W en echelon faults. E-W to WNW-trending short fault segments were traced near the basin trough. Reservoir pinching-out and fault seal Juxtaposition provide the up-dip and lateral trap-seal for the thin and constrained reservoir levels of the Kareem Formation. In contrary, the more continuous, thicker and deeper pre-Miocene sandstone reservoirs were found water-wet due to absence of the effective lateral and up-dip seals. Equivalent successions in the western flank of the Gemsa basin remain unexplored due to difficulties in the prediction of reservoir distribution and trapping configuration since it is not covered by 3D seismic as well as the lack of well data.