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Clearview Geophysics

Borehole Time-Domain EM

March 25, 2021

Borehole Time-Domain EM (Electromagnetics) Surveys are carried out using a fixed loop with electricity powered by transmitters on surface.  ClearView uses Geonics TEM57 transmitters and TEM67 power modules.  Currents up to 28 amps can be applied to 10 gauge copper wire loops. The PROTEM receiver records the results typically with a base frequency of 30 Hz but occasionally with 3 Hz for stronger conductors.

The borehole is first ‘dummy-probed’ to clear potential obstructions including grease and reduce the risk of losing the survey probe.  A ‘hammering’ tool can be lowered along the winch cable to free the probe if stuck.  The Geonics BH43-3d collects data in all 3 directions: axial Z, X and Z. 

Some test work was completed to apply one TEM57 as a master and a second TEM57 as a slave, with both TEM67 modules also connected (4 units total) for added power.

MultiLoop or Maxwell software is used to present and interpret the results.