[OpendTect_Users] Interval Velocity Conversion

[Colin Hawke]

Arnaud,

I have a PDSM interval velocity model in depth in SEGY. All I want is a PSDM interval model in time. I don't want RMS velocities (I don't think I mentioned RMS anywhere).

>> you can do all your
    time-depth conversion work in a time survey with a velocity model
    stored in depth.

As mentioned I have a time OD project and I have a SEGY PSDM interval velocity model in depth. I need this interval PSDM model in Time - can you explain this to me? as it is not obvious how to do this when in the time domain in OD. I need the interval velocity model in TWT as I am building a rather complex trend based rock property model taking in to account over pressure, it is not just time to depth conversion.

Appreciate any help. I have sent a private support question as I believe I have found a bug anyhow.

Kind Regards

Colin Hawke.

Consultant Geophysicist 

Predict Geoconsultants Ltd.

Date: Wed, 25 Apr 2012 14:47:47 +0200
From: arnaud.huck at dgbes.com
To: colinhawke at hotmail.co.uk
CC: micenko at bigpond.com; users at opendtect.org
Subject: Re: [OpendTect_Users] Interval Velocity Conversion



  
    
  
  
    Dear Colin,

    

    Let me add that you can use the time-depth conversion tool to
    convert a Vrms(TWT) velocity model directly into Vint(Z). The
    velocity type necessarily changes because the quantity Vrms is not
    defined in the depth domain.

    

    The opposite is not completely true since Vint(Z) will be converted
    into Vint(TWT), not to Vrms(TWT). But you can do this step using the
    velocity conversion tool if needed. Note that there is absolutely no
    necessity to have Vrms(TWT) in your time survey, you can do all your
    time-depth conversion work in a time survey with a velocity model
    stored in depth.

    

    Best regards,

    Arnaud Huck.

    Arnaud Huck, MSc.
Senior Geoscientist
dGB Earth Sciences
Nijverheidstraat 11-2, 7511 JM Enschede, The Netherlands
arnaud.huck at dgbes.com
Tel: +31 53 4315155 , Fax: +31 53 4315104
http://www.dgbes.com

    

    On 04/25/2012 12:54 PM, Mick wrote:
    
      
      
      
      
        Hi Colin
        I would use the time-depth conversion option
            (Section 7.1.3 in the manual) for doing this.
         
        Without the velocity model builder plugin you can
            still make velocity volumes and do depth conversions.
            Without going into the full details the way I do it is:
         
        -          Import velocity functions
        -          Use volume builder to grid the functions and make
            a 3D volume
        -          Make an average velocity volume and / or interval
            velocity volume
        -          Time-depth conversion
         
        You already have a velocity volume so all you
            need is the last step.
         
        Mick
         
        PS you may need lots of RAM
        
          
            From:
                users-bounces at opendtect.org
                [mailto:users-bounces at opendtect.org] On Behalf Of Colin
                Hawke

                Sent: Wednesday, 25 April 2012 6:25 PM

                To: OPENDTECT USERS

                Subject: [OpendTect_Users] Interval Velocity
                Conversion
          
        
         
        
          Dear
              Users,

              

              I have been given a 3D PSDM Interval Velocity volume in
              SEGY format in depth with 5m sampling. I need this
              velocity model in two-way-time with 4ms sampling. Is there
              a way of converting from Depth to Time in Opendtect
              without using the Velocity Modelling plug-in (I don't have
              this plug-in)? I'm quite familiar with OD but can't seem
              to work this out.

              

              Any help appreciated.

              

              Thanks 

              

              Colin Hawke 
        
      
      
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