Hydrocarbon Seepage Generation and Migration
in the Southern Province from
the Gulf of Suez, Egypt: Insight from Biomarker Characteristics and Source Rock
Modeling
By
Mohamed Abdel-Aziz Younes1, T. El-Azhary2, M. Said2
(1) Alexandria University, Alexandria, Egypt (2) N/A, Stratochem, Egypt
Active hydrocarbon seepage in Gebel El-Zeit area, southern Gulf of Suez
province is associated with the Quaternary outcrop sediments. The oil seepage
occurs in faulted zones on the western flank of the East Zeit Basin. The
biomarker properties obtained from Gas Chromatography-Mass Spectrometry (GC-MS)
proved that the hydrocarbon seepage possesses geochemical characteristics rich
in tricyclic terpanes and extended hopanes with few diasteranes, typical
characteristics of oils derived from marine siliciclastic source rocks with
angiosperm land plants input as indicated from the higher proportion of oleanane
index of 32.65% and low gammacerane index of 6.28%. The maturity parameter based
on [20S/(20S+20R)]-C29 aaa
cholestane to the hydrocarbon seepage was found to be < 0.5; to indicate that
the seepage was generated at relatively low grade thermal maturity. The
hydrocarbon seepages correlate with the biomarker properties of Miocene crude
oils, which were possibly derived from marine siliciclastic syn-rift Lower
Rudeis shales rich in Tertiary angiosperm land plants. The incipient oil
generation window is believed to have been generated at vitrinite reflectance in
the range Ro%=0.60-0.85 at 3-4 million years before present (Mybp). The source
rock distribution allows for extensive lateral and vertical migration
through
faults that reach the surface. Oil expulsion and
migration
began during Middle
Miocene and still continuing at present in Gebel El-Zeit area. Hydrocarbon
seepages may have also migrated from leaking accumulations.