Processing and interpretation

VSP, surface seismic and LOG data joint processing and interpretation services are provided with the use of UNIVERS software.

The technique of VSP data processing and interpretation of results includes the following stages:

1. Preprocessing
  • Applying of statics corrections for base model into source VSP data and monitoring device;
  • Applying of statics corrections calculated from monitoring device records;
  • Impulse form correction by monitoring device;
  • Minimum-phase high-frequency filtration for zero shift elimination;
  • First breaks hodograph definition;
  • Harmonic noises and spikes suppression;
  • Polarization parameters determination;
  • Three-component record orientation, transformation to PRT coordinates system.

The result of procedures described above is prepared for selection three-component wavefield.

2. Kinematic processing
  • Bed boundaries determination by means of interval velocities curve analysis. Interval velocities are calculated from near SP hodographs with a priori information and LOG data;
  • Layer velocities determination by velocity model parameters optimization with the use of near SP hodographs;
  • Correction of the velocity model obtained taking into account absorbtion characteristics and optimization with first break hodographs from all shots;
  • Calculation of average velocities vertical hodograph.

The results of kinematic processing are: anisotropic layered model of the medium, vertical hodograph, interval and average velocities.

3. Dynamic processing
  • Selection of waves i.e. VSP wave field separation on regular waves and residuals. For quality improvement of the selected waves the iterative combined technique including FK filtration and the method of waves selection named POLYCOR based on weighted traces summation. Weights are calculated from multiple correlations;
  • Downcoming wave deconvolution (the calculated filters are used to all selected pressure reflected and exchange waves);
  • Applying of kinematic corrections, normal moveout wavefield construction;
  • Corridor summing and trace of single reflections determination in both time and depth scale;
  • Getting acoustic impedance on the depths scale. Comparison of an acoustic impedance and the trace of single reflections to LOG and CDP data.

4. Processing of distant SP
  • Construction of depth and time VSP-CDP sections from presure reflected waves.

The reflected waves are migrated with anisotropic model of medium taking into account of inclinometry, SP emergent angle, divergence, boundary incident and penetration angles.

5. Interpretation of processing results.
  • Kinematic characteristic of environment;
  • Analysis of the absorbing characteristics of a section;
  • Lithologic-stratigraphic data control with LOG, CMP and VSP;
  • CDP section impulse form estimation and VSP-CDP section deconvolution. (Zero-phase signal conversion and CDP section sensitivity enhancement);
  • Estimation of shear waves velocities anisotropy;
  • Structural interpretation of VSP-CDP images of borehole environment.
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