Vertical Radar Profiling To Determine Dielectric Constant, Water Content And Porosity Values At Well Locations

A vertical radar profiling (VRP) experiment was conducted at the Boise Hydrogeophysical<br>Research Site to determine if direct arrivals and reflections can be recorded using the surface-toborehole<br>survey geometry. The receiving antenna was deployed downhole to insulate it from<br>cultural noise. The transmitting antenna was located on the surface near the wellhead and<br>oriented radially to the well axis. Although the antenna polarizations are perpendicular, we were<br>able to record radar direct-arrivals and reflections. Picked first-arrival traveltimes were inverted<br>to determine layer interval velocities. The VRP-derived velocity estimates fall in the same range<br>as velocity estimates determined from crosshole radar tomography at the site; average velocities<br>for the unsaturated and saturated zones are 0.140 rn/ns and 0.080 m/ns, respectively. Resolution<br>of the VRP-derived velocity estimates is significantly better than the resolution of CMP-derived<br>velocity estimates. Dielectric constant and porosity estimates were also derived from the VRP<br>data using a simple petrophysical model, and compared to porosity estimates derived from<br>neutron logging. Correlation between the two porosity estimates is encouraging. While the VRP<br>method has not been widely used in site investigations to date, the results of this study suggest<br>that VRPs provide an accurate, high-resolution, and cost-effective means of obtaining dielectric<br>constant, EM velocity, volumetric moisture content and porosity values at well locations.