Multichannel Seismic

The seismic source employed an array of two SODERA-SSI's, model GI-GUN guns (Fig. 10). The guns were set to the harmonic configuration of 210 c.i. each, with medium ports, and were fired and syncronized by the IGM gun controller, a system capable of controlling up to four guns.

We used the Teledyne Mod. 24500, 12.5 m group interval, 48 channel streamer, that was hired by FUGRO/OCEANSISMICA of Rome (Fig. 11). The shot distance was set to 50 m, thus attaining a 600% fold coverage. The streamer depth was set to 9 m by three depth controllers and a model DIGISCAN 293A modem by DIGICOURSE. The Oceansismica streamer, after failure, was replaced by the IGM streamer owning the same characteristics.

The analog data were input to the model STRATAVISOR NX GEOMETRICS controller, that digitized and recorded the data in the SEG-D/8048 (demultiplexed format). The sampling rate was set to 1 ms, record lenght to 12288 ms.

The data were processed on board by the Paradigm's FOCUS 2-D software. The processing sequence was conventional up to the time migration for the totality of, including: resampling to 2 ms, editing of the traces, shot delay removal, amplitude recovering, predictive deconvolution, sort, velocity analysis every 200 CMPs, NMO correction, stack, band-pass filter and time migration using stacking velocities reduced of 10%. The seismic data were also interpreted by means of two softwares, made us available in demo copies by Divestco Inc. and Seismic Micro-Technoilogy Inc.: respectively WinPics and Kingdom Suite+.

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Figure 10: picture of the GI guns during their deployment at sea, taken by S. Carluccio.

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Figure 11: picture of the Teledyne streamer during deployment at sea, taken by S. Carluccio.