Automating Borehole GPR Surveys
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Automating Borehole GPR Surveys
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ensors & Software has developed a borehole winch to provide rapid acquisition of zero-offset profiles and multi-offset gathers when using the pulseEKKO® borehole system. The motor-driven winch provides automated positioning through a distance encoder which also triggers data acquisition at fixed depth intervals, making borehole data collection more accurate and significantly less time-consuming. Operators can vary the winch speed depending on the borehole conditions. This results in faster generation of tomographic images of the subsurface.

A common area of interest is using borehole GPR to augment security, for example, conducting surveys to detect clandestine tunnels at sites important for national security or at international border crossings. One issue preventing widespread use of GPR technology for this application is that data acquisition is neither simple nor routine. The new motor-driven winch system simplifies and speeds up borehole data collection, making use of GPR for this application more practical.

Motor-driven borehole winch with depth encoder.
Figure 1:
Motor-driven borehole winch with depth encoder.

One survey method for borehole data collection is Zero Offset Profile (ZOP) where data is collected by simultaneously moving both the transmitting and receiving antennas up the boreholes at the same speed. This survey provides an indication of any anomalies that are present between the boreholes. Figure 2 shows an example of ZOP data where the travel time is significantly shorter from 2 to 4 meters in depth compared to other depths. This is indicative of an air-filled zone between the two boreholes.

Raw data from a Zero Offset Profile (ZOP) showing an air-filled zone between the boreholes from 2 to 4 meters in depth.
Figure 2:
Raw data from a Zero Offset Profile (ZOP) showing an air-filled zone between the boreholes from 2 to 4 meters in depth.
Tomographic velocity image of an air-filled tunnel between boreholes, generated by processing multi-offset gathers (MOGs).
Figure 3:
Tomographic velocity image of an air-filled tunnel between boreholes, generated by processing multi-offset gathers (MOGs).

The introduction of the automated winch system for pulseEKKO® borehole systems increases the accuracy and reduces the time required for borehole surveys, enabling this technology to be adopted into additional application areas.

Click here to learn more about pulseEKKO® Ground Penetrating Radar.

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