Near Surface Geophysics > Flows

Step 1/7

Ambient noise and ambient noise factor

Step 2/7

VSP with hydrophones

Step 3/7

Amplitude of upgoing Stoneley waves and P-wave to Stoneley wave conversion factor

Step 4/7

Fullwave form acoustic section

Step 5/7

Noise/Signal detector and BHTV log

Step 6/7

VSP flow index, Normalized VSP flow and PLT log

Step 7/7

back to the 3D

Update Required To play the media you will need to either update your browser to a recent version or update your Flash plugin.

The same procedure has been applied to the dataset recorded in well M13.

Step 1: Ambient noise and ambient noise factor.
The ambient noise and its associated noise factor detect a karstic body between 85 and 87m, and predict a flow.

Step 2: VSP with hydrophones.
One can notice a downgoing Stoneley wave reflected at a depth of 85 m and converted upgoing and downgoing Stoneley waves from the downgoing P-wave at the same depth.

Step 3: Amplitude of upgoing Stoneley waves and P-wave to Stoneley wave conversion factor.
The instantaneous amplitude of the upgoing converted Stoneley waves and the associated P-body wave to Stoneley wave conversion factor confirm the presence of a karstic body between 85 and 90m.

Step 4: Fullwave form acoustic section.

On the 3 m constant offset section, we can clearly see:
- the refracted P-waves between 0.5 and 1 milliseconds,
- the converted refracted shear waves between 1.2 and 1.8 milliseconds,
- the Stoneley modes after 2 milliseconds
One can notice a strong attenuation of all the waves between 85 and 90 m

Step 5: Noise/Signal detector and BHTV log.
The strong attenuation of all the waves between 85 and 90 is highlighted by the Noise/Signal detector log. The BHTV log confirms the presence of a karstic layer.

Step 6: VSP flow index, Normalized VSP flow and PLT log.
The VSP flow index predicts a flow between 85 and 87m. The VSP flow index has been integrated in depth from bottom to top to mimic a flowmeter in order to do a comparison with a PLT flow. We can notice a good correlation between the 2 logs, taking into account that the vertical resolution is not the same for the 2 logs (2.5 m for the VSP, and 1 cm for the PLT). The variation of the PLT log at a depth of 65 m is due to a change of the borehole diameter.

Step 7: back to the 3D.
The 3D seismic block in porosity confirms the porous bodies between 80 and 90 m, as it can be seen on two sections crossing at the well. The seismic block also predicts porous bodies below the well at 120 m.