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Apply DATUM_FIX module Link to this post

HI,

When I run the STATIC module, I want to compute my corrections from the refstat's workflow, plus a fix reference datum. The module explains that I should use the DATUM_FIX module, however, when I use it, my traces don't show that elevations corrections are applied.

How should I use it in my flow ?

Thank you,
Matt.

Re: Apply DATUM_FIX module Link to this post

What does your jobflow look like, could you attach it?

The *.shf file output from the refstat application can be applied to data via the STATIC module.

The DATUM_FLT - DATUM_SRD pairing of modules allows correction from acquisition datum to floating datum (a smoothed version of the topography) {DATUM_FLT] followed later by correction from floating datum to fixed seismic reference datum (SRD) [DATUM_SRD]. The DATUM_FLT module is normally applied at the start of the overall processing sequence (certainly before NMO), and the DATUM_SRD process module is usually applied quite late in the processing sequence (post NMO, and usually post stack). The purpose of initially using a floating datum is to avoid applying potentially large elevation static corrections at the start of the processing sequence. Instead small time shifts are applied to minimise the distortion to the NMO hyperbolae prior to NMO analysis and correction.

The DATUM_FIX module applies static shifts to correct seismic data from the acquisition datum to a fixed seismic reference datum.

Re: Apply DATUM_FIX module Link to this post

My jobflow looks like this :

1 - SEISJOB
2 - SEISREAD
3 - ADDGEOM
4 - STATIC
5 - DATUM_FIX
6 - SEISWRITE

Only my *.shf file is applied for the static correction, but no elevation correction. However, if I use the command "Datum" and "Vel_datum" in the STATIC module, some corrections are applied to my data.

Re: Apply DATUM_FIX module Link to this post

Shifting to a floating datum and/or fixed seismic reference datum helps to correct for the effect of topography / elevation.

Refractions statics (refstat application) on the other hand corrects for variation in near surface terrain. On land seismic surveys, we can expect the near surface terrain to vary significantly. In a few meters we might go from soft, marshy ground to a weathered outcrop. This can lead to large, localised velocity variations which distort the seismic travel times.

Is the STATIC module being used to apply a *.shf file output from the refstat application i.e. to correct for refraction statics?

To correct for elevation statics either the modules DATUM_FLT (Corrects from acquisition datum to floating datum) and (later) DATUM_SRD (Corrects from floating datum to a fixed seismic reference datum) OR DATUM_FIX (Corrects from acquisition datum to a fixed seismic reference datum directly) should be used - not the STATIC module, the DATUM and VELREP parameters in this module have been deprecated by the DATUM_* modules.

Re: Apply DATUM_FIX module Link to this post

I want to use both refraction's corrections from the refstat's workflow and the elevation's correction to a fix datum.

I use STATIC module only for the the *.shf file output from refstat's workflow, but I also want to apply elevation's corrections for total static corrections.

I know that I must use the DATUM_FIX module for elevation's corrections, but I don't see any differencies whether I use or not the module in my flow, because the total static corrections in my traces show no change, but only refraction's corrections.

Re: Apply DATUM_FIX module Link to this post

If you can send your jobflow, support files and a sample of your dataset through to claritas.support@gns.cri.nz we can try to take a look and see what the issue might be.

Re: Apply DATUM_FIX module Link to this post

Ok,
I can send all my flows which lead to my static's workflow with the data.

Thank you again.
Matthieu.

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