[OpendTect_Users] Few questions on 3D horizons

[Kristoffer Rimaila]

Dear Michael,

Hopefully the points below will answer your questions.

1) Two horizons can be merged through using the 'horizon' and 
'mathematics' attributes. First, output 'z' of the horizons with the 
'horizon' attribute (select 'Positions' and 'Horizon' in the 3D 
attribute set).  You will also need to select input seismic here. Next, 
use the 'mathematics' attribute to merge the two (or more) attributes 
created from your horizons. For example, you can use the following 
formula: horizon1 == undef? horizon2:horizon1 if your horizons contain 
'empty space' within your inline/crossline range, i.e. undefined data. 
Give a name  and save. If the horizons you want to merge are overlapping 
you will need to accommodate for this in your mathematics attribute. For 
example you can specify the attribute to deal with overlap with the 
following formula: horizon1 > horizon2? horizon1 : horizon2 or vice 
versa, depending on which of the overlapping horizon-portions you wish 
to keep. Then use this attribute as input when you 'set' the formula for 
the merge attribute. If you ignore to take the overlap into account, the 
z value of your merged horizon will be the z-value of horizon1 + z-value 
of horizon2, i.e. double. After creating the merging attribute, go to 
'Processing' in the main menu, select 'Create Grid Output' --> 'Grid' 
---> '3D...'. Here, choose the merged attribute created with the 
formula, give new name and choose which surface to use as reference 
('Calculate on surface').

After gridding the attribute, go to 'Survey' (main toolbar) --> 'Export' 
--> 'Horizons' --> 'ASCII 3D'. Select the merging (mathematics) 
attribute, set area subselection (optional) and for 'Output Z' choose 
'No'. Give output name and hit 'Go'. The new, merged horizon can then be 
imported similarly in the main toolbar through 'Survey' --> 'Import' --> 
'Horizons' --> 'Ascii' --> 'Geometry 3D'. Here, select the exported 
file. It should not contain a header. Define the format (z-units are in 
seconds!). Scan input file (optional), give output name and hit 'Go'. 
The merged horizon can now be loaded in the tree.

The workflow above is obviously time consuming and complicated. 
OpendTect version 4.3 (which will be released after the EAGE conference 
in two weeks) deals with merging horizons in a much simpler way; you can 
use the 'set z-values' tool under algorithms in the tree to convert a 
grid into a horizon or apply a shift, stored as a grid to the horizon.

2) For more information on how to track/edit a horizon, please refer to 
chapter 3.3 of the OpendTect user-documentation manual. It can be found 
on the dGB support site: 
http://opendtect.org/rel/doc/User/base/chapter3.3_interpret-horizons.htm#LINK-TRACKING.SETUP

3) It is possible for multiple persons to work on the same project. To 
do this, I would suggest you set the data-root (ODData) to the same 
network location on all of the computers you wish to work on. To avoid 
file conflicts with edited horizons, faults etc. the first thing to do 
would be to open the files and 'save as..' and create separate files for 
each interpreter, using initials in names as id for instance.

If you have any further questions, please do not hesitate to contact me.

best regards,

-- Kristoffer Rimaila
-- Geoscientist
-- dGB Earth Sciences
-- Nijverheidstraat 11-2, 7511 JM Enschede, The Netherlands
-- mailto: kristoffer.rimaila at dgbes.com, http://www.dgbes.com
-- Tel: +31 53 4315155 , Fax: +31 53 4315104


On 9-5-2011 14:47, Michael Heeremans wrote:
>   Hi,
>
>   I have a few questions regarding 3D Horizons and 3D horizon tracking
>   and hope that someone can help me with that:
>
>   1) How can a merge 2 horizons into 1 horizon.
>
>   2) When I have tracked a few in- and crosslines using the line tracker
>   option for 3D horizons, I change to Volume tracker to fill in the rest.
>   When I then want to edit this automatic interpretation and use the
>   Auto-track option, does it overwrite my earlier interpreted seeds? If
>   so, what is the best workflow for interpreting and editing a 3D horizon?
>
>   3) Is it possible for two person to work simultaneously on the same
>   project or will this lead to that OD crashes?
>
>   Best regards, Michel
>