Gas seepage and pockmark formation in the Levant Basin, offshore Israel, provide valuable insights into subsurface fluid migration and hydrocarbon systems. Most previous studies that examined pockmarks and gas seepage in this area were limited to the depth of the Base Pliocene horizon. Thus, the relation between these shallow gas escape features and deeper gas systems remained unattended.
The current study integrates 3D pre-stack depth-migrated seismic data and well logs to investigate the pre-Messinian geological controls on seepage pathways and the relation between pockmark development observed in the base Messinian and base Pliocene horizons.
As a starting point, seismic well-tie analysis at the Myra-01 well was performed to obtain stratigraphic correlations within the Oligocene to Pliocene sequences. Next a high-resolution, detailed, structural framework, was constructed, incorporating the correlation of intra-Messinian units. Subsequent structural and geomorphological analysis of the base Messinian and base Pliocene horizons identified distinct structural domains, including extensional, compressional, and rollover zones.
As shown by previous works, the seismic data shows the presence of pockmarks. This suggests either active or past fluid flow in the area. Root Mean Square amplitude and time maps of the base Messinian and base Pliocene horizons were used to highlight variations in seismic reflectivity and pockmark locations. Our initial results indicate that the base Messinian and base Pliocene pockmarks do not spatially overlap. They also differ in size and distribution, with base Pliocene pockmarks being smaller and more widespread. These findings challenge a possible assumption of direct vertical fluid pathways and highlight the complexity of fluid migration in this region.
Detailed structural and geomorphological framework presented here has not yet been able to identify potential fluid migration sources or pathways within the intra-Messinian layers. To constrain such sources, we intend to integrate lithological analysis, based on Amplitude-Versus-Offset inversion. This approach should help us improve our understanding of gas systems connectivity and constrain the mechanisms driving fluid flow within the Levant Basin.