Page 151 - Acquisition and Processing of Marine Seismic Data

142 2. MARINE SEISMIC DATA ACQUISITION

also analyzed along with the seismic data. After multiples and front-end noise level including
the offline QC processes of the seismic data, the swell and operational noise. A single fold 3D
following deliverables are produced in addition cube without flex binning is prepared using a
to the other client-specific requests: single velocity function for NMO correction to
verify the navigation and seismic merge as well
• QC reports per line as the survey coverage. Single fold cubes are not
• SegY header map
used for interpretation purposes, but they pro-
• Brute stack plots
vide time slice maps as well as inline and cross-
• Brute stacks in SegY format with navigation
line displays of the seismic data. They are also
in the headers
used to verify the navigation and seismic merge,
• Near trace plots
where incorrect navigation merge results in
• Single trace or near trace cube
jumps in the crossline traces and striping effects
• Velocity files in specified format (if necessary)
in the time slices. Common channel stacks and
• Migrated fast-track cube (if necessary)
common shot stacks can be generated for every
In addition to the visual inspection of the shot sequence (Fig. 2.85) to check for abnormally high
records, the near trace sections, brute stack sec- amplitudes, such as cross-feed, leakage or other
tions and single fold cube are the main products electrical problems of a potential faulty streamer
of the QC analysis for the seismic data. Prepar- section.
ing near trace sections is the best way for a quick Determination of bad or noisy traces, dead
determination of possible acquisition errors, traces, auto-fires, misfires, and lost records for
such as bad records, misfires, auto fires, overlap- each completed seismic line is an important
ping shot points, array amplitude issues, time- QC implementation, and is performed by a
break problems, etc. These sections also provide visual inspection of all or selected shot gathers
an initial opinion about the strength of the along the line after a suitable band-pass filter

FIG. 2.85 Common channel stack computed for the first 400 shots of the line.