Test of the Radar Fracture Mapping Tool in a Lake Using a Known Target

Abstract

A method to located fractures adjacent to but not intersecting a wellbore would be a great aid to the geothermal industry. A prototype downhole radar probe was recently compiled with the aim of locating fractures near a single wellbore. This probe, operating in the pulse mode with a bandwidth of 30 to 300 MHz, contains two identical directional antennas. A with any prototype instrumentation, extensive fieldwork is required to completely understand the characteristics of the system. A first step in that understanding is to operate the instrument under known or controlled conditions. In this paper, a series of tests of the radar probe in the lake using a known target are reported. In the tests, signals reflected from the target t were observed when the target was 5 ft and 9 ft from the probe; in the latter case the returned signal was greatly attenuated by the water. The measure 3 dB beam width of the system to the target was 70 degrees. Finally, the effect of the target size was studied by moving the probe across the face of the target.