PGS Completes Successful 4D Overlap Base-Survey for Statoil

Using the vessel Ramform Victory, PGS has successfully completed a customized 4D base survey for Statoil over the Albatross/Snohvit field, offshore Norway.

To achieve an overlap configuration, the vessel deployed 10 streamers over an 8 streamer pre-plot survey. The overlap allowed the streamer vessel to follow the survey’s straight pre-plot lines, ensuring complete surface coverage and reduced infill. Infill shooting on this survey was below 5 percent.

The conditioned 4D base survey simplifies and optimizes the repetition of source positions for future repeat surveys. The repetition of such shot positions, in combination with the overlap configuration, improves azimuth preservation for 4D acquisition.

Using the surplus data acquired in the overlap zones and selective binning schemes, it will be possible to achieve a better 4D match. Source-receiver azimuths can be better matched using this approach.

Acquiring 4D data with such a strategy gives a more complete surface coverage and thus assures improved repetition for acquisition and processing of future 4D surveys.

Benefits of 4D Overlap

  • Reduces infill shooting
  • Minimizes crossline deviations
  • Simplifies the repetition of shot points in repeat surveys
  • Almost perfect azimuth matching