GLOBE Claritas Refraction Statics Analysis
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 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.
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.
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 MO-corrected data.
- Claritas REFSTAT.pdf (464.41 kB)