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Hydrocarbon Systems in the Onshore and Offshore Sicilian Fold and Thrust Belt: New Constraints from Geochemical
Data*

Carlo Caldarelli1 and D. Smith1

Search and Discovery Article #30202 (2012)

Posted March 12, 2012

*Adapted from extended abstract prepared in conjunction with oral presentation at AAPG International Conference and Exhibition, Milan, Italy, October 23-26, 2011

1Northern Petroleum Plc (ccaldarelli@northpet.com)

Abstract
The onshore Sicilian thrust belt has been extensively studied, whereas little information is available for the offshore thrust belt. The paleo tectonic
units which constitute the onshore thrust belt were deposited on a Mesozoic passive margin linked to the opening of the Tethys. These units bear
some similarities, especially during the Cretaceous, with equivalent facies in North Africa. New geochemical data have been acquired in the onshore
Sicilian thrust belt. The results obtained have been correlated with existing data from Northern Tunisia and offshore Sicily and integrated with a
regional geological model. The occurrence of Late Triassic-Liassic intraplatform basins with proven hydrocarbon potential has been identified in
western Sicily as well as in equivalent Mesozoic Trapanese facies in the inverted Tortonian-Messinian foredeep offshore Sicily. The Cenomanian-
Turonian black shales outcropping in NE Sicily, regarded as a unit equivalent to the Bahloul Formation in North Africa, have the highest source
rock potential of all the analyzed samples and can be regarded as a world class source rock. Our studies indicate these sequences were deposited in a
near-shore environment consistent with slope facies of the Panormide platform. Geochemical studies have shown a possible correlation between the
oils of the Nilde and Norma discoveries in the inverted offshore Tortonian-Messinian foredeep, the Bahloul Formation (Cenomanian-Turonian) in
Tunisia, and the equivalent Bahloul facies in northeastern Sicily. These oils also correlate with the Fahdene Formation (Aptian, Albian) in Tunisia,
however a contribution from the Bahloul Formation is considered more likely. Our studies concluded the most significant petroleum accumulations
in the inverted offshore Tortonian-Messinian foredeep (e.g. Norma and Nilde discoveries) derive from hydrocarbons being generated in the offshore
Sicilian thrust belt where different sequences, possibly Panormide type, are expected to occur and to have entered the oil window from Late
Miocene to the present day. Tertiary source rocks, although prolific in Tunisia and Sicily, are not expected to contribute significantly to the
hydrocarbon system of the offshore Sicilian thrust belt.

Introduction

Northern Petroleum and its partner Shell Italia E&P are jointly engaged in oil & gas exploration in a large area of relatively deep water offshore
western Sicily. The area under study contains the offshore extension of the Atlas fold & thrust belt of North Africa which links to the north-east with