[Users] Using OpendTect for simple time-to-depth stretch?

[Mike Cline]

Tom,

As I understand your question, you're basically wanting to know how to resample your regularly-spaced seismic time data into regularly-spaced depth samples?  Unfortunately, I can't fully answer your original question, relative to OpendTect, because I'm still a relatively new to many of its features.  I've had it for a while now, but mainly use a competitor's package for interpretation, and depth conversion, so I'm not as high up on the learning curve for it as I should be at this point.

However, I can offer an alternative solution, if you are open to some initial "quick-look" results.  For example, if it's a prospect, and you just wanted to determine whether or not to pursue it for further evaluation.  My quick-look suggestion would be to only depth convert the interpreted horizon(s) of interest with a spreadsheet.  You would still be able to see how the prospect looked in depth, without going through much of the required effort yet.

Generally, you would first export the horizon(s) from OpendTect (comma delimited ascii works best).  Then, import this ascii data into a spreadsheet, and enter a formula that includes your velocity info to calculate the layer-cake depth output.  Then graph this depth output.  I did something similar a few years ago on a fault shadow problem, before I had any seismic depth conversion capabilities, and it was pretty easy.

Hope this (partially) helps.

W. Michael "Mike" Cline
Consulting Geophysicist
T/X Resources
 
Phone:  (713) 665-5449
Blog:  http://txresources.com/rocks2digits/
Website:  www.txresources.com
 
"Combining Technology with Petroleum Exploration Since 1985"


  ----- Original Message ----- 
  From: Tom Kearney 
  To: users at opendtect.org 
  Sent: Tuesday, January 01, 2008 9:20 PM
  Subject: [Users] Using OpendTect for simple time-to-depth stretch?


  All,

   

  Can anyone suggest a way to use the attribute package to do a simple vertical stretch of a seismic volume from time to depth? I wish to use a simple two-layer model, such that if the sample is above the seabed horizon, use a constant velocity; if below the seabed, derive a value from a simple polynomial relating velocity to time below seabed. My problem is that the output samples (in depth) will effectively have a reference shift as compared to the input samples (in time), and will need to be rounded up to some pre-defined depth sampling increment, and I can't see how to apply this.

   

  Thanks for any ideas.

   

  Regards,

   

  Tom Kearney

  Staff Geophysicist

   

  Salamander Energy plc

  #34-02 UOB Plaza 1,

  80 Raffles Place,

  Singapore 048624

  Tel:    +65 6309 3300

  DID:   +65 6309 3472

  Mob:  +65 9732 1767

  Fax:   +65 6536 5390

  Email: Tom.Kearney at salamander-energy.com.sg 

   



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