Offshore Mediterranean Seismic Data Processing Challenges

Magdy AbdelAty^1*, Tamer Saleh¹, Michael Cogan^1**, Alfredo Cegna², Antonio Betti², Giorgio Bondi², and Riccardo Vercesi^2
1WesternGeco, Egypt
²Eni, Egypt
*[email protected];
**[email protected];

The application of a modern processing sequence that focuses on noise and multiple at-tenuation demonstrated how careful reprocessing can add significant value to existing data sets and improve exploration decision making. The results of a recent 3-D seismic reproc-essing effort over approximately 1,800 square km of data from the Mediterranean Sea has brought renewed interest in deep, pre-Messinian structures. Historically, the reservoir tar-gets in the southern Mediterranean Sea have been the Pliocene-Pleistocene and Messin-ian/Pre-Messinian gas sands. These are readily identifiable as anomalous bright amplitudes on the seismic data. The key to enhancing the deeper structure is multiple and noise at-tenuation. The Miocene and older targets are overlain by a Messinian-aged, structurally complex anhydrite layer, the Rosetta Formation. This layer is of variable thickness and is highly fractured in places. The quality of seismic data beneath it tends to be inversely pro-portional to the thickness and complexity of the layer. The Rosetta Formation also gener-ates a significant amount of complex multiple energy. On the seismic data, these multiples are not well defined. Many methods of multiple attenuation are therefore only partially suc-cessful, and the residual multiple often appears as a fuzz of noise on near and middle off-sets. Attenuation of this residual multiple noise was one of the keys to the success of the reprocessing effort. This presentation outlines a carefully executed processing flow to en-hance the signal-to-noise ratio and improve the time imaging for the pre-Messinian struc-tures in the southeast Mediterranean Sea. The success of the reprocessing meant that acre-age that was due to be relinquished was extended, and is now a location for new seismic activity and possibly, new drilling.

AAPG Search and Discovery Article #90077©2008 GEO 2008 Middle East Conference and Exhibition, Manama, Bahrain