Using Regional 2D Seismic Data to Redefine the Exploration Play Potential of the Offshore Sirt Basin and Cyrenaica Margin, Libya

Abstract

Exploration in the offshore Sirt Basin in Libya has been limited and to date commercially unsuccessful. Previous exploration efforts have also been hampered by poor seismic data quality and limited well constraints on the highly complex geological history. However, recent wells have proven working petroleum systems in the offshore area, but the extent, character and full potential of these systems remains poorly understood. Meanwhile, the onshore Sirt Basin has yielded some of the world’s largest petroleum discoveries, with estimated oil reserves of 123 billion barrels. In this study we draw analogues between the successful onshore area and the underexplored offshore area by analyzing a new regional seismic data set to highlight the future potential. We place the offshore Sirt Basin and adjacent Cyrenaica Margin into a regional context to understand the relationship with the onshore basins Here, over 45,000 km of recently acquired and depth processed deep regional seismic data and newly reimaged legacy 2D seismic data has been interpreted and integrated with offshore well data in a mega-regional basin study. We present a well constrained crustal-scale structural and tectonic model placed within the regional context of the tectonically complex central Mediterranean. For the first time, deep imaging of the pre- and early rift basin is interpreted within a structural context to pull together the full tectonostratigraphic history of the offshore Sirt Basin and Cyrenaica Margin, from the Hercynian Orogeny to Mesozoic extension and Cenozoic inversion. The regional stratigraphy from the Palaeozoic to present, has been interpreted in the context of assessing the petroleum potential of the basin. It is demonstrated that the offshore basin represents the geological continuation of the prolific onshore Sirt Basin and that this whole system was likely restricted and not open to Tethys during deposition of the key Sirt shale source interval. Using onshore analogues, results from offshore wells and this newly interpreted data there is now an enhanced understanding of the potential potential in the offshore area. A better understanding of the distribution of reservoir facies in the Cretaceous and Tertiary systems, the presence and maturation of source rock and the location of many undrilled features are presented to demonstrate that the offshore Sirt Basin and Cyrenaica Margin contains significant untested exploration potential.

AAPG Datapages/Search and Discovery Article #90355 © 2019 AAPG Africa Region, The Eastern Mediterranean Mega-Basin: New Data, New Ideas and New Opportunities, Alexandra, Egypt, September 6-7, 2019