Struggling with Time - Depth conversion

[Maria Alejandra G.L]

Dear Opendtect community,

I’ve been struggling for a while trying to convert time to depth and then exporting the seismic into a segy file. I’m submitting a post after consulting the forum posts to find some guidance, but the workflows don’t seem clear to me. I apologize If someone has already asked the same question before.
I can use the F3 dataset for reference and to reproduce your suggestions. I’m numbering my questions to ease the consultation.

Previously, I converted time to depth using the 3D “Time – Depth Conversion” Tool available at the Processing tab. I tried using a “Well’s Depth Model” as Z transform input, but the output seismic (far from the chosen well) does not correlate with markers and horizons, showing a difference of about 40 meters.
1)  Can this difference be corrected in some way? Should the “Tie well to seismic” be used to solve this issue?
2)  Is there a way to use more than one well’s depth model to make the conversion?

I have 2D/3D horizons and only interval velocities from well’s depth model. I thought I could make the conversion using horizons and its corresponding velocity, but I haven’t found the way. The “Horizon-Based Velocity Analysis” ask for Prestack data (which I don’t have). I believe the most optimal approach would be using the horizons as they were interpreted from markers:
3)  Can the horizons be used in some way to make the time – depth conversion without Prestack data?

As I have read and heard, converted seismic (on the fly) cannot be used to interpret nor be exported as segy files:
4)  Is there another type of conversion that is not done on the fly? So that I can store the output seismic in memory?

Thanks for your guidance.

[Hesham Refayee]

Hi Maria,

Please have a look at our self-training manual (section 1.4.4, p90). I believe it answers all your questions.

Best regards,

https://static.dgbes.com/images/PDF/Introduction-To-OpendTect-and-OpendTect-Pro-Training-Manual.pdf

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Hesham Refayee

Senior Geoscientist

-----------------------------------------------------------------------------------------------------------------------   dGB Earth Sciences

Phone: +12812403939 E-mail: hesham....@dgbes.com Internet: dgbes.com

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