WellSweep^®

Vibration survey technique using a fully controlled sweep signal based on VSP data analysis.

Phase tuner^® software module was created to implement the possibility to take into account the phase distortion of the vibration signal by analyzing VSP seismographs.

Concept:

• Seismic surveys are active methods based on the radiation of signals into the geologic environment;
• The response of the medium depends directly on the shape of the signal (amplitude, frequency, and phase components);
• Vibrational methods make it possible to radiate signals of arbitrary shape;
• The most desirable signals are considered to be those that compensate for losses due to propagation through the medium (inverse filter);
• VSP data allows the most accurate evaluation of the signal propagating from the surface to the sediment level;
• The new inverse signal significantly improves the resolution of the VSP;
• The same return signal can be used for onshore 3D seismic surveys to obtain results similar to borehole seismic measurements

1. Standard VSP

2. VSP with control signal

3. Comparison of standard and optimal signals VSP and pulse response seismogram

4. Low frequency content (1-5 Hz)

The phase of WellSweep at low frequencies is better compensated, which is important for inversion and FWI.

5. High frequency content (50-120 Hz)

6. Image of Cenomanian deposit

Conclusions:

• The fully controlled signal concept was successfully tested in the field.
• The emitted VSP test signal included various amplitudes, phases, minimum phases, Q, deterministic and statistical inverse filters.
• A VSP-designed sweep (WellSweep) was used for the 3D onshore seismic survey.
• A fully controlled signal significantly improves both VSP and surface seismic results.
• An improved vibration controller is needed to use the fully controlled radiometric method..

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