The Integration of Petroleum Systems Elements for Hydrocarbon Prospecting in Pre-Messinian Stratigraphic Section of the Offshore West Nile Delta, Egypt

Abstract

The study area is situated in the offshore West Nile Delta basin towards the northeast of Alexandria, Egypt. This is a major petroleum habitat hosting many gas and condensate fields. The present paper summarizes the petroleum system elements for hydrocarbon prospecting in the Messinian and deeper stratigraphic section based on an integrated study of seismic and well data. Mixed well results have been observed in the area with proven gas fields found in stratigraphic fluvial channels in the Messinian. Rotated fault blocks and fault dependent traps were tested but no discoveries were proven. Failure could be due to trap integrity issues and inadequate migration pathways. Potential remaining stratigraphic plays identified are deepwater slope channels in the pre-Messinian to Oligocene section similar to overlying Pliocene gas fields. Depositional models based on seismic attribute mapping and a few wells generally depicts a NW-SE facies belt trend dominated by deepwater slope channel complexes flanked by slope shales ranging in age from Upper Oligocene to Miocene (Pre-Messinian). In the Messinian, the depositional environment is associated with a major sea-level drop with consequent exposure of the shelf/slope. It contains predominantly incised valleys and fluvial-fills flanked by interfluves. The hydrocarbon charge is expected from Cretaceous-Jurassic and Early Tertiary pro-delta shale source rocks (Marten et al., 2004). Evidence of highly mature thermogenic gases (2.0 % - 2.5% VRo) advocates the assumption of the presence of a deeper source rock contribution from limited well calibration. Basin modeling results shows that the modelled source rocks are presently in the hydrocarbon generation window. Source rock generation has occurred very late from 9.0Ma to 1.0Ma and migration timing post-dates trap formation. Traps are expected to be charged vertically and through fault conduits as observed in well results. This study paved the way for a better understanding of the petroleum system elements which consequently forms the basis in risking the Messinian and deeper exploration plays and shows that the Messinian stratigraphic channel plays are most prospective.