Velocity model building in the major basins of the eastern Mediterranean Sea for imaging regional prospectivity

Abstract

Hydrocarbon prospectivity in the eastern Mediterranean is challenged by the presence of the Messinian salt layer, which varies in complexity across the area. The macro salt layer geometry itself varies from the deep abyssal planes in the middle of two major basins (the Herodotus and Levant basins), where it shows simple top and base relief to more complicated geometries near the continental salt-free shelf. Building depth velocity models for imaging the eastern Mediterranean basins requires accurate determination of the complex salt top and base, as well as accurate estimation of their velocities. Since 2006, many 2D and 3D megasurveys using conventional and dual-sensor acquisitions have been carried out across the area. Regional and relatively simple velocity models are used to image the Messinian salt layer extensions from offshore West Egypt to offshore Lebanon, passing by the Cypriot waters and the Eratosthenes Seamount. The data acquired include shallow and deepwater surveys, and technologies such as full-waveform inversion are applied to produce high-resolution images for the shallow post-Messinian section. Shallow-water imaging challenges such as acquisition footprint issues and low-angle illumination are solved by imaging with multiples using dual-sensor acquisition data. The Messinian salt layer is modeled with a simple constant regional velocity, while the pre-Messinian section is modeled with a simple combination of velocity gradient models. The regional model-building scheme introduces a good correction for the pre-Messinian structure and provides reliable multiclient data ready for outlining new prospects.