Generate a valid SEGY file from segyio (Python module)

[Raí Bizerra]

Hello everyone! I'm trying to generate a gradient cube as trace data from a SEG-Y file. The idea is to build a very simple seismic example, just to learn how to deal with the segyio tool. Even though I fill in many header keys (see source code attached), I can't open my file in OpendTect (see attached image). Can someone help me?

[Fernando Bordignon]

Raí, it is difficult to run your code using the PDF file. Try to send the .py file in the future.

On a quick look, I've noticed you used only one row of il and xl (rows 57 and 58)

if you want to write all your 100 traces, you need to provide the inlines and xlines for all the traces on the file header.

Try using your variables iline and xline defined at lines 39 and 40, replacing il and xl on line 57 and 58.

After that, you need to find those in the header when importing with OpendTect.

Regards,

Fernando.

On Mon, Feb 1, 2021 at 9:37 AM Raí Bizerra <raispb...@gmail.com> wrote:

Hello everyone! I'm trying to generate a gradient cube as trace data from a SEG-Y file. The idea is to build a very simple seismic example, just to learn how to deal with the segyio tool. Even though I fill in many header keys (see source code attached), I can't open my file in OpendTect (see attached image). Can someone help me?

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[Raí Bizerra]

Hello Fernando. I appreciate your tips. Thanks to those I managed to import 3D pre-stack data into OpendTect.

Now I'm having a problem to import a 2D pre-stack data. This pre-stack data is just the first inline (10) of the 3D previously imported.

I don't understand where these inline/xline ranges come from (see attached image). The source code used to generate the 2D data is attached too (sorry about that).

Regards,

Raí.

[Fernando Bordignon]

Raí, the values being loaded from the segy seems to be alright  [0,9]

I don't have much experience with pre-stack, but I believe the inline/xline ranges are sort of a default when creating a survey, for this case pre-stack data does not influence that.

You can set up the limits of the survey after this screen to one of your liking.  

Check out how the data inside segy is organized for the prestack case.

Maybe take a look at this tutorial https://github.com/equinor/segyio/tree/master/python/tutorials

They have an example of a segy with multiple gathers.

Sorry to not be able to help any further.

Regards, Fernando.

[Raí Bizerra]

Fernando, thanks for the analysis. From it I noticed some features of OpendTect.

OpendTect seems very sensitive to inline / xline intervals starting at 0. 

For now I'm using the tutorial strategy to show 2D data. 

I will continue to debug the segyio and OpendTect. 

Regards, Raí

[Nanne Hemstra]

Hi Rai,

Please look at the scan settings in the SEG-Y import window. By default OpendTect accepts values of 1 and higher (please see image below). If you change the highlighted values to 0, the scanner will see your inlines with value 0 as well.

Best regards,
Nanne

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[Raí Bizerra]

Thank you, Nanne. That's pretty helpful.

Now I'm trying to do something that might be complicated: 
Can I choose a frame to be the wall of my volume? 

Using madagascar, I managed to do this with sfgrey3 and frame selection, like: 

• sfgrey3 < ... frame1=x  frame2=y  frame3=z ... , where x, y and z are integers.

Regards, 
Raí

[Nanne Hemstra]

Hi Rai,

OpendTect does not support the same type of frame display like Madagascar. Instead, OpendTect has a 3D visualization environment, where you can add any number of in-lines, cross-lines or z-slices at any position in the 3D volume. You can also add data as a 3D box via the Volume display item.

For Linux users, OpendTect has a link to Madagascar. For more information, please see https://doc.opendtect.org/6.6.0/doc/od_userdoc/Default.htm#processing/madagascar.htm

Best regards,

Nanne