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The output from REFSTAT effectively replaces a specified number of layers by calculating both the time-delays caused by those layers, and also the surface-consistent residual shifts needed to further minimise the discrepancy between measured and calculated travel-times. For 3-D refraction static analysis, the earth-model comprises a mesh of triangular facets. The diagnostic tools include 3-D isometric displays of travel times and static shift corrections.
GLOBE Claritas also includes a linear-moveout processor module, which may be used to calculate refraction statics in areas with slowly-varying near-surface velocities by running traditional residual statics on LMO-corrected data. Next: Wavelet>>
First breaks>> |
The
centrepiece of GLOBE Claritas' refraction statics software is the
REFSTAT application, which takes a text file of first-break picks,
and derives an earth model which gives the best fit to the measured
first-breaks. The model may then be used to determine shot and receiver
time-delays to correct for the weathered layer. REFSTAT has repeatedly
produced excellent results in many regions throughout the world.
A reliable refraction statics solution is usually an essential pre-requisite
for a successful land seismic processing sequence. 
The
earth-model comprises up to five layers, within which the velocities
are allowed to vary laterally. A full least-squares inversion is
solved for all interface vertices and velocity control-points, with
the aim of minimising the RMS difference between the measured first-breaks
and the travel-times calculated from the earth-model. Unlike many
other refraction statics packages, the first-arrivals are not assigned
to any particular refractor. 
The
many diagnostic features make it very easy to convert first-break
data into a static shift file to apply to seismic reflection data,
or to a model producing a best fit to seismic refraction data. The
earth-model is easily modified using the VIEWMODEL graphical editor.