SEG Y rev1 May 2002 Comments

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We are delighted that an update of the SEGY standards has finally arrived. Encana has been able to incorporate many of the additional fields as we develop an new standard as a result of the merger between Pan Canadian and Alberta Energy Energy company.

What defines a standard? A standard is more than a proposal, it's what is actually being utilized. The Canadian company Crestar led the way and declared that they were going to use the same standard used by their interpretation software. Photon (now Paradigm) interpretation software uses the SeisX SEGY standard for both 2D and 3D data. Data are checked to this standard before data delivery and as a result data loading has been eliminated at Crestar. It is estimated that more than 500,000 seismic lines already exist to this standard.

While the new SEG Y rev1 standard is close to meeting our needs, it fails with respect to the following:

• SEGY in Canada has used data sample format code of 6=SUN IEEE Big Endian for more than ten years. According to the SEG Y rev1 standard, 6 isn't used!
• Is the 5=IEEE Big or Little Endian? Our experience shows that a code of 5 means different things from different hardware platforms.
• Integers and scale factors are used in the header instead of IEEE real numbers. SeisX makes full use of real numbers where appropriate.
• The SEG Y Format Revision number space in the Binary header is used by the SeisX line name. SeisX has used byte location 399 for the past ten years as their SeisX flag location.
• Full compatibility with SeisX/SeisWare.
• The Extended Textual Header record definition is used by the SeisX line name. It is recommended that at separate text file be provided for this variable length descriptive information.
• A few missing items from the SEG Y rev1 standard:
  1. Internal 20 byte LINE NAME in the binary header
  2. Internal 12 byte REFERENCE NUMBER in the binary header
  3. SEISMIC DATUM and REPLACEMENT VELOCITY in the binary header. Every line processed in Western Canada is different and must be shifted to properly tie.
  4. Amplitude distributions for PEAK, AVERAGE and RMS. These numbers reduce the time it takes to display data to the terminal.
  5. Total PHASE ROTATION applied to the data. It's important to keep track of what phase rotation was required in order to tie your data in the stratigraphic Western Canadian Sedimentary Basin.
  6. LATITUDE, LONGITUDE min and max. Data can easily be scanned to simplify the building of Seismic projects.
  7. Both XY's and LATUTUDE LONGITUDE are stored in the trace header.
  8. Corner points for 3D stack data sets, rotation orientation and the 3 points it takes to define a 3D survey. 3D map views can easily be generated with these reference points.

Here is a link to the Proposed Encana SEGY standard.

Site Owner: Eric Keyser
Last Updated: Oct 13, 2002