Journal of Petroleum Geology, Vol.26, No.2, 211-224, 2003
Hydrocarbon seepage generation and migration in the southern Gulf of Suez, Egypt: Insights from biomarker characteristics and source rock modelling
Active oil seepages in the Gebel El-Zeit area (southern Gulf of Suez, Egypt) occur in fault zones on the western flank of the East Zeit Basin. Gas chromatography-mass spectrometry indicates that these oils are rich in tricyclic terpanes and extended hopanes with few diasteranes. These characteristics are typical of oils derived from marine siliciclastic source rocks; an input of terrestrial angiosperms material is indicated by the very high oleanane index of 32.65% and the low gammacerane index of 6.28%. The molecular maturity parameter C(29)alphaalphaalpha cholestane [20S/(20S+20R)] is <0.5 indicating that these oils were generated at relatively low thermal maturities. The seepage oils resemble Miocene crude oils in the East Zeit Basin which are believed to be generated from the Lower Miocene Rudeis Shale. Burial history modelling indicates that oil generation from this unit began at around 3-4 Ma at vitrinite reflectance levels of Ro%=0.60-0.85. This implies extensive lateral and vertical migration has taken place for the generated oil to reach the surface. Alternatively, the seepage oils may he sourced by leakage from preexisting accumulations.