Tectonics and carbonate platform development, Gabes-Tripoli Basin, offshore Libya


This research proposal targets the Cenozoic development of faults, folds and carbonate platforms in the Gabes-Tripoli Basin, Mediterranean Sea, western offshore Libya. The study area encompasses numerous large hydrocarbon fields (for example the Bouri Field with 1,000 to 3,000 Million barrels oil) that are of major economic importance for Libya.

Yet, despite the relevance and value of the study area, there are today unsolved issues including: (i) the late Cretaceous to recent regional tectonic development of the Gabes-Tripoli Basin influencing sedimentary patterns and the basin wide stratigraphy. (ii) the structural development of hydrocarbon bearing anticlines concerning the role of a potential Triassic salt substratum. (iii) Carbonate platform development through time; and (iv) the interaction of tectonic and sedimentary processes controlling reservoir development (deposition, diagenesis, structural overprint, trap integrity).

The proposed work focuses on the analysis of a unique state-of-the-art three-dimensional subsurface dataset (around 1800 square kilometers covered by three-dimensional seismic-reflection data; geophysical borehole information of 13 industrial wells) kindly provided for academic research by the National Oil Corporation of Libya (NOC) to test following (partly controversial) research hypotheses: (1) The presence of Triassic salt in the deeper subsurface of the Gabes-Tripoli Basin was a key control for structural development offshore Libya, determining fold style above a salt detachment and controlling the formation of reservoir rocks (Eocene nummulitic limestones) above pre-existing salt structures. (2) Faulting, folding, carbonate sedimentation and trap formation in the Gabes-Tripoli Basin was not influenced by the Triassic salt substratum. (3) The west to east orientation of major hydrocarbon-bearing anticlines is oblique to the main fault trend striking along a northwest to southeast direction; folding and the preferential growth of carbonate platforms at the top of anticlines pre-date the development of these faults. (4) Diagenetic changes (for example dolomitisation; burial corrosion in relation to underlying salt structures) within the main reservoir limestones can be identified on three-dimensional seismic-reflection data by seismic-attribute analysis validated at well locations by wireline data. (5) Neogene carbonate platforms of the Gabes-Tripoli Basin differ in architecture, size, type and distribution from their Paleogene predecessors. (6) Post-depositional tectonics and differential stratigraphic loading influenced reservoir development. Areas significantly affected by Neogene to recent tectonics lack subsurface reservoirs.

A final important aspect of this research proposal is the development of fundamental tectonic and stratigraphic knowledge in a region largely neglected by the academic literature, in which, for political reasons, little research can currently take place.

Funding: DFG project 417476001