Topic:
Why are my markers posting in the wrong place?

Description:
I changed a depth value for my marker but it still posts in the same place on
seismic. Or, checkshot values changed but marker position on seismic did not.
And some other general marker usage rules in GeoFrame 3.5.

Solution:
Open the Marker Data Manager for the borehole and make sure that the following
several fields (attributes) are displayed: MD, TVD, TWT, Time Pick, Index. Index
column indicates which attribute is the "original" - all others are derived from
it and are therefore "secondary". For example, if a marker was entered as MD
value, the other fields (TVD, TWT, TVDSS) will be calculated based on MD as well
as available deviation, checkshot survey and borehole datums. Index column for
such marker will show MD.

If you modify any other field in the marker spreadsheet (say, TVD) and apply
changes, the index type will be switched to TVD and all other fields will be
recalculated based on THAT value (now and in the future).

If your marker has an index type of TWT (two-way time) and you make changes in
checkshot for that borehole, then MD and TVD are going to be recalculated
automatically but TWT will stay the same. If the opposite is true (index is MD
and changes are made to checkshot survey) then TWT will be recalculated
automatically.

So the first thing to check is - what is the index type of your marker.

Also take note of what values (if any) are present in the "Time pick" column.

A single marker can have both a STP (seismic time pick) and TWT value, and these
values can be different. When a marker has both STP and TWT values, the markers
display on seismic using STP value. 

By definition, STP is a marker value defined in time, independent of the
checkshot. When a marker is created or edited in the time domain, a seismic time
pick value is generated for the marker. TWT is a marker time value which is
defined by the time trajectory of the borehole (deviation and checkshot
surveys).

If seismic time pick value is absent, then the TWT value is used for posting on
seismic.

When a marker is interpreted in GeoViz, an STP value is generated. If a TWT
value is already present for that marker, it remains unchanged. More generally,
if a marker is interpreted (edited) in the time domain in IESX (GeoViz), it
affects only the seismic time pick and not TWT, MD or TVD values for that
marker. If TWT value (as well as MD and TVD) were previously absent they will
remain null.

As already mentioned, TWT values are automatically recalculated when checkshot
or depth values are changed. However, STP (time pick) values are NOT changed. So
if you want your posted markers to change positions automatically upon update in
MD or checkshot, you have to delete the values in the time pick column in the
Marker Data Manager. (Be careful not to delete markers that were interpreted in
GeoViz which may be needed.)

For more information regarding marker usage rules, see online documentation in
GeoViz/Interpret markers and Data managers/Appendix C in GeoFrame Bookshelf.





Last Modified on: 09-JUN-00