Fluid Rlow Reconstruction in Cretaceous Panormide Platform Limestones: Implications for Timing of Oil Migration in the Sicilian Fold and Thrust Belt

Ben Dewever¹, Rudy Swennen¹, François Roure², Pietro Di Stefano³, Isaac Berwouts¹, and Philippe Muchez^1
1K.U.Leuven, Heverlee, Belgium
²Institut Francais de Petrole (IFP), Rueil-malmaison, France
³Universita` di Palermo, Palermo, Italy

Karstic cavities in Cretaceous platform limestones in Sicily contain bitumen and associated late diagenetic phases. The Panormide platform formed a structural high in a basinal area and was submerged in the Eocene. Subsequently, it was covered with thick Oligocene series of siliciclastic flysch deposits (over 2 km) before onset of thrusting in the Middle Miocene. Aim of the study was to determine origin and timing of oil migration by reconstructing fluid flow and its physico-chemical conditions through time. The late diagenetic products are studied with petrographical, geochemical and microthermometric techniques to constrain the origin of the fluids and the pressure and temperature at which the products precipitated (PVTXt-model). Meteoric fluids created the porous karstic network that constitutes the reservoir. During Oligocene burial and subsequent thrusting, hot saline fluids (°" 135¢XC) migrated through the reservoir. The fluids displayed increasing fluid-rock interaction with clay rock lithologies as evidenced by the gradual change from depleted to more enriched ƒÔ¹⁸O signature and high ⁸⁷Sr/⁸⁶Sr ratios. Preliminary Rock-Eval pyrolysis results indicate that black shales of the Numidian flysch interval form a possible source rock for bitumen in the Cretaceous reservoir. This complies with either lateral fluid flow from adjacent shales into the Cretaceous platform or upward fluid flow from overthrusted Numidian flysch. Finally, less saline fluids migrated through the reservoir during Pliocene transtensional tectonics. The results of this outcrop analogue study offer new perspectives for exploration in the Sicilian fold and thrust belt and identify the Numidian flysch as a potential source rock for oil.

AAPG Search and Discovery Article #90072 © 2007 AAPG and AAPG European Region Conference, Athens, Greece