Time to Depth Seismic Reprocessing of Vintage Data: a Case Study in the Otranto Channel (South Adriatic Sea)

Vintage seismic data are of significant value for the scientific community, especially when reprocessed with up-to-date methodologies. In this chapter, we demonstrated that a specific processing flow and velocity modeling workflow can significantly improve the imaging of geological features within old data. In particular, the proposed time reprocessing flow enabled us to overcome aliasing problems related to low fold coverage that affected the performance of SRME and PSTM. To avoid spatial aliasing, we included two interpolation steps in the processing sequence, which increased the fold coverage for SRME and migration, respectively. The application of both SRME and WEMA algorithms strongly attenuate the energy of multiple reflections, showing that this is also an optimal approach for treating vintage, low coverage seismic data. The temporal resolution has been improved by broadening the frequency bandwidth and applying a designature procedure consisting of three main steps: deghosting, Q correction, and surface consistent deconvolution. A specific velocity modeling workflow was adopted, using the coherence inversion technique to build an optimal initial model and then using both the layerbased and the grid tomography to refine it. The final velocity model enables a reliable depth image of the MS-29 seismic line for the first time. The reprocessing and depth imaging of the MS-29 seismic line lead to an easier and more reliable interpretation of the seismic horizons, seismic facies, and seismic amplitude anomalies. Our major new geological insights in the South Adriatic Sea can be summarized as follow: Gas chimneys and wipe-out zones testify to the presence of gas. This presence is consistent with some bright spots related to gas accumulation, which we interpret inside the Plio-Quaternary sequence. The stratigraphic architecture of the Apulia CP is related to reactivation of normal faults and sea level changes triggering different depositional systems. Above the northern margin, a coral reef is interpreted, drowned below the Pliocene sequence. The base of the Carbonate Platform, underlying the pelagic Middle Jurassic-Neogene sequence of the South Apulia Basin, has been evidenced at a depth of 4 s TWT, approximately corresponding to 5 km. At the foot of the southern margin of the platform, a chaotic wedge is likely related to tectonic activity during Neogene time, probably associated with faults activity. Also, we identify a chaotic layer within both basins that we attribute to mass transport deposits. An active transpressive system has been recognized which cuts the Albanian-Hellenic Chain, allowing the Corfù Arc to migrate further west then the Albanian Chain. Earthquakes recorded in the same region could be related to the intersection of the fault system with an isolated carbonate platform present inside the South Apulia Basin. Above a regular deposition of Pliocene layers, which covers in continuity the South Adriatic Basin, the Apulia CP, and the South Apulia Basin, the Pleistocene sequence is thicker at the top of the carbonate platform and is thinning. This is due to no deposition or erosion, above both basins, where the seismic profile is slightly west of the axial depocenter. This suggests that the sea bottom currents connecting the Adriatic and the Ionian seas were particularly efficient only since the Pleistocene. During the Messinian sea level drop, this connection was probably barred by the Apulia CP promontory.