Near Surface Geophysics > Calibration and Synthetic seismograms

Step 1/4

Synthetic seismogram after compensation of the velocity log by the block shift method

Step 2/4

Calibration in time after compensation of the velocity log by the block shift method

Step 3/4

Time Calibration of surface seismic sections by VSP and acoustic logs

Step 4/4

Depth Calibration of surface seismic sections by VSP and acoustic logs

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The corrected velocity log is used to calculate a log of reflectivity and a corrected synthetic seismogram.

Step 1: Synthetic seismogram after compensation of the velocity log by the block shift method.
It can be seen that the reflector with high amplitude of about 70 ms has disappeared.

Step 2: Calibration in time after compensation of the velocity log by the block shift method.
The corrected synthetic seismogram trace, duplicated 5 times, is inserted in the in-line section 3 at the CMP position associated with the cross-line section 6. The correlation coefficient between synthetic seismogram and seismic trace at the well location is high (0.77) confirming a good fit of the seismic horizons in time.

Step 3: Time Calibration of surface seismic sections by VSP and acoustic logs.
The figure shows the comparison of the calibration of a seismic section using both a synthetic seismogram (computed from acoustic log) and a VSP stacked trace. The synthetic seismogram and the VSP stacked trace are inserted in the in-line section 3 at the CMP position associated with the cross-line section 6.

Step 4: Depth Calibration of surface seismic sections by VSP and acoustic logs.
The synthetic seismogram allows the identification of reflectors in the depth range where the logs have been recorded. The VSP stacked trace allows calibration in the same depth range, but it also predicts the presence of reflectors under the well, particularly in the 90-180 m range.