[OpendTect_Users] Time-depth horizon conversion
Witold Seweryn
witek at picknowl.com.au
Thu Jul 14 05:00:39 CEST 2011
FirmaDear OD users,
This discussion has been going on for some time, so I decided to add
something to it. Maybe someone will find it useful.
Some time ago I have written software, which enables conversion of standard
segy files from time to depth domain as well as to enable conversion of
ASCII interpretation files from time to depth and also from depth to time.
The result of segy file conversion is the new segy file with vertical scale
measured in depth. This file can be loaded to seismic workstation like any
other segy file. This is simple time to depth conversion, which is done
using time to depth relationship supplied in a form of time-depth pairs.
Time-depth pairs can be derived from well checkshot survey for example. In
this way you can do your interpretation in depth from the start, or you can
convert time interpretation to depth later using ASCII converter.
Demo version of the software is free, so you can try it for yourself.
Here is link to my website: http://users.chariot.net.au/~witek/t2d.htm with
some description of the software and download.
Have a look if you are interested. Send me an email if you have questions.
Regards,
Witold Seweryn
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-----Original Message-----
From: users-bounces at opendtect.org [mailto:users-bounces at opendtect.org]On
Behalf Of David Epelboim
Sent: Wednesday, 13 July 2011 11:30 PM
To: users at opendtect.org
Subject: Re: [OpendTect_Users] Time-depth horizon conversion
Hello everyone,
We are currently developing a OD Plugin tool called CLAS (or Computer Log
Analysis Software) that's primarily targeted at Well Log Interpretation, but
some functionality tools allow the mix of Petrophysics and Geology Well data
with Geophysics and Seismic Interpretation.
Part of the tools that will come out on the Lite (and actually Beta)
version are the Velocity Function module designed to compute Velocity
expressions (as V= Vo + a*Depth) and then use those functions to store
computed Depth/Time Models storing them as such, or as a Well Log Curve.
The models can be Least Squares, Miller, and a Stack Velocity that uses
inputs from Seismic Stacking velocities coming from Seismic Processing.
With those outputs it is possible to create an attribute applying the Math
function obtained or to use them as inputs for the Processing->Volume
Builder to obtain a velocity volume to apply later using the methods
described before.
CLAS Lite plugin is scheduled for launching in some few weeks
Regards,
David Epelboim, Geoinfo SRL, Argentina
25 de Mayo 168 - Piso 9
Ciudad Autónoma de Buenos Aires, Argentina
CP: C1002ABD
Tel: (+54-11)-4343-8635/8681/7938
Fax: ext. 206
http://www.geoinfo.com.ar
Ing. David Epelboim
e-mail: david at geoinfo.com.ar
MSN: david at geoinfo.com.ar
skype: david.geoinfo
skype soporte Kingdom: soporte_la_smt.geoinfo
Mike Stone wrote, On 07/01/2011 11:35:
You know, an approach I like better is to create a Time-Depth Volume
Attribute.
It's basically the same procedure except you create a reference stack of
time values and do a Avg * Ref/2 instead.
This way you can extract Depth Horizons directly rather then having to
calculate each one. If you have dozens of horizons this can be a real time
saver.
Of course this all assumes you have average velocities right?
Mike Stone
832-768-0884
MStone at ACT3Solutions.com
On Fri, Jul 1, 2011 at 4:52 AM, Farrukh Qayyum
<farrukh.qayyum at dgbes.com> wrote:
Dear Emilson,
We normally do an on the fly time to depth conversion of the seismic
data using a velocity cube. However, if you want to convert only time
horizons into depth horizons within OpendTect then you will have to do the
following steps.
1.. Go to Attribute set window (Main Menu > Analysis > Attribute >
...).
2.. In the pop-up attribute set window, you will have to find
Horizon attribute in the list.
a.. Select that attribute and provide an input seismic data on
which the Horizon was being mapped.
b.. Select the horizon that you want to convert into depth.
c.. Do not change the default Output type. Please leave it 'Z'.
d.. Provide an output name to this horizon attribute (e.g. Horizon
A).
3.. The above step is done to get Z-values (in seconds) of a given
horizon and then multiply the attribute with a velocity data. The next step
is to do time to depth conversion:
a.. Now find the Mathematics attribute in the list. In the formula
bar, please type this: HorZ * Vel/2. Prese the Set button. Here, we are
using two variables. HorZ is the defined horizon attribute (Horizon A) and
the Vel is a stored Velocity data. If you do not have any velocity data and
you want to use a constant velocity, please replace the Vel variable to any
constant value e.g. 3000.
b.. Once you will press the Set button, it will ask you to provide
the inputs for HorZ and Vel variables. Please select the right inputs as
explained in the above bullet.
c.. Give an output name (e.g. Horizon A depth) to this attribute.
d.. Save the attribute set and press OK to the Attribute set
window.
4.. Now create the grid output (Main Menu > Processing > Create Grid
Output). In the pop-up window, please select the Quantity to output (here it
should be the attribute i.e. Horizon A depth). Then also select the horizon
for the calculate on surface field. Once done, press Proceed button.
Please note that the horizon is saved as an attribute data (depth) on
a selected horizon that can be exported as an ASCII grid. To export the
attribute grid created in the step 4, you may use the export utility form
the Main Menu > Export > Ascii .... In the Export Horizon window, select the
horizon and the calculated attribute from the list and export it to a disk.
This exported horizon can be used in the depth survey.
Best Regards,
Farrukh Qayyum
Geoscientist
dGB Earth Sciences B.V.
Nijverheidstraat 11-2,
7511 JM Enschede, The Netherlands.
Tel: +31 53 4315155
Fax: +31 53 4315104
http://www.dgbes.com
mailto: farrukh.qayyum at dgbes.com
On 06/30/2011 09:20 PM, Emilson wrote:
Dear OpendTect users,
Is there a way to convert time-horizons into depth-horizons within
OpendTect?
Thank you all,
Emilson P. Leite
DGRN/IG/UNICAMP
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