A borehole radar prototype: Development and testing

Abstract

A prototype of borehole radar has been successfully tested in three sites for different purposes under a field condition. The objective of the prototype is for providing an effective downhole tool for detecting targets in deep boreholes situated in a relatively high conductivity area such as the metal ores. The first testing site is at a geothermal field. The fractures extended more than 20 m from the borehole are delineated by the borehole radar in single-hole reflection mode. The second testing site is located in a jade mine for basement evaluation. The cross-hole measurement mode was used to detect the cavities made by previous unorganized mining activities. Several high-velocity anomalies were found in the velocity profile and presumably the targets of the mine shafts and tunnels. The third test site is located in a mineralized belt characterized by low resistivity less than 1000 Ohm. m, the surface-borehole measurement was carried out, and the data was processed with velocity tomography. The low-velocity zone is corresponding to a mineralized zone from geological records. The three testing results proved the readiness of this borehole radar prototype for further deployment in more complicated and realistic field situations.