Tectono-stratigraphic evolution of the eastern Mediterranean and the impact of the Messinian salinity crisis on the petroleum systems

• Main Author: Al-Balushi, Abdulaziz
• Other Authors: Fraser, Alastair J. ; Jackson, Christopher A.-L
• Published: Imperial College London 2014
• Subjects: 665.5
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.712814

A number of recent giant gas discoveries offshore Levant and in the Nile Delta have established the eastern Mediterranean as a major hydrocarbon province. Future exploration success will rely heavily on a detailed understanding of the regional tectonostratigraphic evolution of the basin. Critical inputs to reservoir, charge and trap modelling such as rifting age, rifting direction and the distribution of oceanic versus continental crust are poorly constrained. Additionally, the impact on the petroleum system of the sudden and significant drop in Mediterranean sea level during the Messinian Salinity Crisis in the Late Miocene, has been largely overlooked. In order to address these fundamental research issues, I conduct a detailed interpretation of an unprecedented coverage of regional two-dimensional (2D) deep reflection seismic lines from the eastern Mediterranean. Importantly, the structural and stratigraphic interpretation has been calibrated with borehole data from the margins of the basin. The seismic interpretation aims primarily to map the rifting direction and document key seismic observations that provide insights to the nature of the crust. A reverse subsidence modelling technique has been used to constrain the age of rifting using palaeo-water depth calibration data from both well data and seismic facies analysis. I also carried out flexural backstripping analysis and 2D petroleum system modelling to investigate the impact of the Messinian Salinity Crisis on the hydrocarbon habitat. The main conclusion of this study is that the eastern Mediterranean opened in response to Early-to-Mid Jurassic, NW-SE directed extension along a series of NE-SW trending normal and NW-SE trending transfer faults. The majority of the basin is predicted to be underlain by highly extended continental crust except offshore northern Levant where evidence suggests a remnant of neo-Tethyan oceanic crust is preserved to the south of the Cyprus subduction zone. The result also predicts that the Messinian Salinity Crisis was associated with a ca. 2070 m drop in sea level. This likely encouraged salt deposition producing a pronounced effect on the basin morphology and subsurface pressure and temperature equilibrium conditions. The 2D petroleum system model predicts that changes in pore pressure will lead to hydrocarbon phase changes within reservoir intervals. The impact of this phase change on the pre-existing hydrocarbon accumulations is controlled by the charge, trap size and the seal parameters - which in the worst case can lead to catastrophic trap integrity failure.