Welcome to Techco Geophysical Services Ltd.
Developing seismic processing software
Main Software Products - VELANAL
VELANAL is a velocity analysis by which the user bases their
choice of a correct velocity on the stack image generated by that velocity.
The main features of this program are:
VELANAL interfaces naturally with SUMMIG, a
Techco product which performs prestack time migration. It is a quick and
intuitive QC of a seismic data image and the velocity field which generated it.
It is written primarily in Java with certain very portable pieces of code
written in c and c++. This allows the program to be placed on multiple
hardware platforms with no programming effort. It requires that at least java
1.3 be installed on the host machine. VELANAL uses a flexible SEGY header
format, configured by an ASCII file. The minimum information required is
inline, xline, cdp-x and cdp-y. For 2D data, inline must be a constant value
and xline must be set to the cdp number of the stacked trace.
- SEGY 2D or 3D data may be input. The data are stacks generated with
various percentages of a base velocity field. The percentage value
is stored in a trace header. The stacks may be migrated or
- The 100% ASCII velocity field is input. This velocity field,
multiplied by the percentage in a trace header allows the program to
compute the velocity used to generate the stack trace.
- Stacks may be viewed in overlay mode or may be limited to a range of
cdps around a velocity control point. In overlay mode, the data
traces are sorted into line order, followed by a sort into percentage
order and finally into cdp order. For each line, the percentage
stacks may be flipped quickly onto and off of the screen. This
enables the user to decide on the best image. A simple click of the
mouse near a control point will result in that velocity percentage
being stored by the program.
- The user may optionally choose to see the seismic overlain on top of
the velocity field. As the velocities are changed, the underlying
velocity image is repainted, allowing a quick visual QC of velocity
smoothness. This is of critical importance in picking good velocities
for a prestack time migration.
- The new velocity field, picked from the images, is saved as an ASCII
- Prestack data may also be input. This data is displayed in a separate
window and is tied to the stack display window; velocity changes in
one are reflected in the other. As the velocity control points are
updated on the stack display, the gather display will automatically
switch to display the most recently modified gather. This window also
displays an interactive stack and a semblance display. The intent of
this window is as a fine resolution Q.C. of the velocities picked on
the stack window. Any residual moveout errors may be corrected here.
- Anisotropic moveout may be applied and eta values chosen off a special
semblance display which temporarily overlays the main semblance.
- An interactive map is produced, allowing the user to select an
arbitrary inline to display.
- If desired, the whole velocity field may be resampled onto a regular
Last modified: Tue Sep 2 20:59:57 MDT 2003