2019 AAPG Annual Convention and Exhibition:

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Defining New Exploration Play Potential in the Offshore Sirt Basin and Cyrenaica Margin, Libya, Using Mega-Regional 2-D Seismic Data


The onshore Sirt Basin, Libya, has yielded some of the world’s largest petroleum discoveries, with estimated oil reserves of 123 billion barrels. The offshore extent of this system, however, is poorly constrained due to limited exploration activity and a poor understanding of the complex geological history. Recent wells have proven both equivalent and new petroleum systems in the offshore, but the extent, character and full potential of these systems is currently poorly understood. Furthermore, the structural complexities of the offshore area and the relationships between the ancient crustal domains is only starting to be realized. Placing the offshore Sirt Basin and adjacent Cyrenaica Margin into a regional context and understanding the relationship with the onshore basins will be key to future exploration of this potentially huge yet underexplored province. 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. These data allow a well constrained crustal-scale structural and tectonic model to be defined and 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 this structurally complex region. It will be shown 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 plays in the offshore area. A better understanding of the distribution of reservoir facies, the presence and maturation of source rock and the location of many undrilled features will be presented and it will be demonstrated that the offshore Sirt Basin and Cyrenaica Margin contains significant exploration potential, as yet not properly tested.