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TOMO3D v1.2 is a 3D nonlinear refraction travel-time tomography software product developed by GeoTomo LLC.   Applications include imaging near-surface velocity structures and making refraction statics corrections in complex geological areas. TOMO3D has been successfully applied to real data sets from the oil and gas as well as the environmental and engineering industries.  Customers include Unocal, Schlumberger Geco-Prakla, and Exxon.

INTRODUCTION TO TOMO3D - A COMPLETE TOOL FOR 3D TOMOGRAPHY

TOMO3D v1.2 includes six major modules. The combination of TOMO3D and TOMO+ is a complete 2D and 3D tomography package from picking travel times, velocity analysis, tomographic imaging, to statics interpretation.  TOMO3D v1.2 has capabilities for obtaining both tomographic and delay-time solutions for statics interpretation.  It can be applied to solve both 3D marine refraction imaging and land imaging problems.

 

3D Tomography Software (8293 bytes)


 

  • GEOMETRY ANALYSIS

    There are more than 30 functions in this module! Display 3D travel times, perform 3D geometry coordinates transformation, analyze time picks, identify and remove bad picks, automatically pick velocites from shot-offset data, and many more ...

  • MODEL ANALYSIS

    View 3D velocity models, and more than 15 functions! Extract or place back a small model section, create a topography file from survey geometry, convert a 3D depth-velocity model to a time-velocity model and more ...

  • 3D RAYTRACING

    Perform 3D refraction travel-time and raypath calculation for a given velocity model and survey geometry.  It can help you to design 3D seismic survey, and also provide syhthetic data for tomography experiments.

  • 3D TOMOGRAPHY

    There are three refraction tomography approaches that you can choose: grid-based tomography, interface-based tomography, and joint grid- and interface-based tomography for your need.  This module outputs updated velocity models iteratively, outputs final tomography predicted travel times, reports inversion progress and performance parameters.

  • QC CONTROL

    Analyze the convergence of tomographic inversion, and help you understand misfit residuals in several ways, identify inconsistent picks and geometry errors, and relocate the shots with large misfits by inverting their positions with the tomographic velocity solution.

  • REFRACTION STATICS

    Calculate refraction statics from an input velocity model and a survey geometry file, or from depth-velocity parameters inferred from delay times.   It can display statics times in 1D/2D, output statics times in various formats.


3dgeom.gif (523 bytes)GEOMETRY ANALYSIS - Front Interface

You may apply any of the funtionality to process your time picks at any time.   Each of them is an independent process.  When you select a data set to view, you are able to control the data with a shot geometry display for any process as shown in the following.  The blue shows the current active shot, the green shows those with delay times picked, while the red shows those untouched.


 
GEOMETRY ANALYSIS - Rapid Processing
With travel-time working window, you are able to do a few things: (1) check picking quality and any processing result from using functions in the front interface; (2) manually or automatically pick refraction turning points for deriving simple statics solution directly or building a realistic 3D starting model for tomography; (3) use overlay function to compare fit between data and tomography predicted times.
 

datdisplay.gif (11887 bytes)


3dmodel.gif (1146 bytes) MODEL ANALYSIS MODULE - All About Velocities

 

modelanalysis.gif (12278 bytes)


View 3D Velocity Model


RAYTRACING MODULE - In and Out
 

Raytracing (7655 bytes)


TOMOGRAPHY MODULE - Three Choices
 

tomo.gif (7152 bytes)


3dgrid.gif (571 bytes) Performing 3D Tomographic Inversion - It cannot be easier !
3D Tomography progress.gif (2579 bytes)

You provide input and output files. You may choose to extend the model laterally along the side raypaths near the model boundaries, or fix the near-boundary velocities if this model will be placed back to a large model. You may choose to downward extend the highest velocity along the deep refractor or just leave it as it is. You may choose a constant smoothing parameter or a linearly varying parameter. Or you do not need to choose anything, just let the program figure it out ...

There are three different tomography approaches that you can choose.  The tomography approach inverting interfaces simply assumes that the shallow Earth consists of a few layers with arbitrary interfaces and constant velocities, while full grid-based tomography does not.  It all depends on data! 
If you find that the data suggests sharp interfaces and simple layer velocities, use the interface tomography.  If it shows evidence of both sharp interfaces and variable velocities, you need to apply the joint interface- and grid-based tomography.  You also have a choice of tomography without any assumption of the Earth structure- full grid-based tomography.  Making assumption is not always right, but making no assumption is not always easy either.  All we need to do is to be flexible.

3dsol.gif (412 bytes) QC CONTROL View inversion convergence rate, look into misfit for each shot, relocate shot positions using nonlinear inversion schemes if shot locations are suspected wrong from misfit analysis.  This shot relocation program provides a rapid geometry solution with the tomographic velocity input.  Instead of using a direct-wave arrival and a simple near-surface velocity to infer shot location, this module actually uses any first arrivals including refractions, and derives shot locations in an arbitrary 3D velocity model.
 

QC Control (8075 bytes)

shotrms.gif (15420 bytes)


 
3dstatics.gif (398 bytes)REFRACTION STATICS

statics.gif (13719 bytes)


A 3D Case History --Land 3D data, 10,207 Shots, 5,103,500 Traces

This large 3D survey was performed over a complicated near-surface velocity structure. Because of the near-surface complexity, 3D seismic data processing for imaging deep reflectors encounters significant difficulties. Conventional refraction statics interpretation methods failed because of assuming simplified velocity structures. 3D refraction tomography is a powerful tool for solving the problem in this situation. TOMO3D was successfully applied to reconstruct the near-surface velocity structures for this case.
 

3D Velocity Image

The above images show the near-surface velocity distribution at four depths. Downward direction is the positive increase. The surface is at a depth of about 2500 feet above the sea level. The velocity images clearly show NW-SE structural trend. A high-velocity intrusion occurs in the central area. A major fault appears at the NE corner. The high-velocity sediment dips down from NE to SW.

 

 
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