Integrated interpretation reveals new Mesozoic play types in the southern and central Croatian Adriatic.

Abstract

The Adriatic is a uniquely structured basin comprising a double foreland between the eastward verging Apulian thrust and the westward verging Dinaric thrust belt. Historically, despite an excellent geological understanding of the tectonic framework and Mesozoic geology, exploration of the Mesozoic section offshore Croatia has been unsuccessful largely due to poor seismic imaging. Such legacy data quality limitations have been overcome by modern reprocessing, and the integration of this data with new (2013) 2D, new 3D (2012), marine potential field data, and well data. This integrated dataset has allowed a re-evaluation of the structural-stratigraphic evolution and prospectivity of the Croatian Adriatic.

The new interpretation based on high resolution long cable seismic data has re-defined the major structural elements offering the possibility to recognize prospective structural trends and to synthesize the fault framework. The improved imaging of deeper structures allows the interpretation of hydrocarbon source rock in intra-platform syn-rift basins in addition to revealing Permo-Triassic trapping geometries previously unseen.

Basin modelling completed on the new interpretation confirms that the Triassic source rock is mature for oil at present day with some deeper areas in the gas and oil window. The new seismic data has also emphasized the role of halokinesis as key to the development of the basin's hydrocarbon potential.

The interpretation has identified multiple Cretaceous play types that are potentially oil bearing and sourced from the Triassic level. These include; carbonate platform margin reefs sealed by transgressive limestone and Tertiary clastics, marl sealed karstified structures and lowstand high energy fans in addition to salt cored anticlines within shallow to deep water carbonates sealed by Tertiary clastics.

Three new Jurassic plays are recognized with oil and gas condensate potential sourced from the Triassic. These comprise; salt cored anticlines, carbonate platform marginal carbonates and shallow water carbonates on tilted fault blocks, all sealed by Jurassic shales and marls. Additionally a Permo-Triassic play is identified comprising fault blocks sealed by Triassic evaporites and sourced by deeper Permo-Triassic black shales.

We compare these play models to proven onshore and offshore Italian analogue discoveries. An improved understanding of the fault structural trends and the volume and importance of salt within the carbonate margin has been gained by combining various methodologies and datasets. The interpretation of modern seismic has greatly aided the identification of numerous new Mesozoic plays opening up a new era of exploration offshore Croatia.

AAPG Datapages/Search and Discovery Article #90226 © 2015 European Regional Conference and Exhibition, Lisbon, Portugal, May 18-19, 2015