Imaging Pre-Messinian Targets in the Eastern Mediterranean Using FWI and RTM

Abstract The Eastern Mediterranean Basin has emerged as a region of considerable hydrocarbon prospectivity, underpinned by well-established petroleum systems across multiple stratigraphic intervals. Proven reserves in Jurassic and Cretaceous formations, as well as Pliocene deep-marine sandstones sourced from the Nile Delta, highlight the region's potential for both oil and gas accumulations. Additionally, the identification of Pre-Messinian carbonate buildups—analogous to the prolific Zohr gas discovery offshore Egypt—suggests that similar high-potential plays remain underexplored (Roberts & Peace, 2020). Despite this promise, imaging Pre-Messinian targets remains a significant geophysical challenge due to the presence of the heterogeneous Messinian evaporite sequence. Although the post-Messinian sedimentary section is generally thin in the West Delta, the Messinian salt exhibits substantial lateral and vertical velocity variations, introducing strong seismic velocity contrasts in the overburden. These contrasts adversely affect wavefield propagation, leading to distorted seismic images and reduced illumination of subsalt targets (Kumar et al., 2022). Effective imaging of the Pre-Messinian interval requires addressing two principal challenges: accurate characterization of salt-body geometry and velocity heterogeneity, and mitigation of illumination issues related to the complex topography and internal variability of the salt. This demands a robust depth velocity model building (VMB) process, supported by advanced imaging technologies. Full Waveform Inversion (FWI) and Reverse Time Migration (RTM) have demonstrated substantial value in this context. FWI enhances the resolution of subsurface velocity models by iteratively minimizing the misfit between recorded and modeled seismic data, while RTM enables accurate imaging in complex geological settings by accounting for multi-pathing and wavefield complexity (Brandsberg-Dahl et al., 2017). We present data examples from recent seismic acquisition programs in the Eastern Mediterranean that have implemented these techniques, with encouraging results. Tailored acquisition geometries and high-end processing workflows have improved the fidelity of subsalt imaging, revealing structural and stratigraphic details within Pre-Messinian targets that were previously obscured. These enhanced seismic images provide interpreters with critical information to delineate potential reservoir facies, including deep-marine clastics and carbonate buildups, thereby reducing exploration risk and supporting more informed drilling decisions (Kirkham et al., 2023).