--> ABSTRACT: Hydrocarbon Systems of the Hagfa Trough, Sirte Basin, Libya, by M. W. Ibrahim and S. Al Mahrouqi; #90906(2001)

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M. W. Ibrahim1 and S. Al Mahrouqi2

1Target Exploration, London
2Huxley School of Environment, Imperial College, London, UK

ABSTRACT: Hydrocarbon Systems of the Hagfa Trough, Sirte Basin, Libya

More than 5000 meters of post-Palaeozoic sediments have been preserved in the 300 Kms Long by 40 Kms wide Hagfa trough of central Sirte Basin. The Hagfa trough is a tectonostratigraphic twin to the Ajdabia Trough of eastern Sirte Basin. The prolific (4 Billion Bbls OIIP) Upper Palaeocene Intisar reef trend was found in the Ajdabia Trough, while hitherto exploration efforts failed to find similar prolific reefs in the Hagfa trough.

Well data, geochemical source rock analysis, geothermal gradients, and seismic maps of the Hagfa trough were integrated in order to define the operating hydrocarbon system(s), and assess potential of the hitherto undiscovered Intisar-like trend within the Hagfa trough.

Directions, and times of oil and gas generations and migrations were modelled and retraced against rock facies and structural evolution of the trough in order to define times, types and locations of hydrocarbon entrapments in the stratigraphic equivalent to the Intisar reefs, as well as other reservoirs.

This study confirmed the exploration importance of the pre-and post-Upper Palaeocene targets:
• The pre-Upper Cretaceous Sirte group (Hofra-Nubian-Bahi) sands are proven oil and gas reservoirs in structural traps at Al-Hagfa trough and it’s flanking highs.
• The Waha-Faiz members of the Maastrichtian Kalash Formation, the “M-59”, and the Ora-F members of the Lower Palaeocene Beda Formation.
• The Eocene Gialo Formation is proven reservoirs in structural traps at the flanking highs to the Hagfa trough.

The Palaeocene Zelten Formation (the Hagfa trough's stratigraphic equivalent to the Intisar reef of Ajdabia) is a proven reservoir in structural traps at the Zelten-Waha High (ENE flank of the Hagfa trough). However, this study indicates that the Zelten C, B and A Members are also potential exploration targets for rudimentary Intisar-type of oil traps in the Hagfa Trough proper.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado