Electromagnetic Modeling of Oil Shale Retorts for Remote Sensing Purposes

We report here some work on the modeling of oil shale retort for remote sensing purposes. The aim is to obtain useful information about the contents of the retort (e.g., rubble size, void ratio, etc.) by means of electromagnetic probes. In this paper, the retort is modeled by a spheroid with an average dielectric constant which depends on the void ratio. The near field due to a radiating dipole source in the vicinity of a spheroidal retort is computed using the Extended Boundary Condition Method. Numerical results are given at 4 MHz for a retort with major axis 45.7 m (150 ft), minor axis 25.1 m (82.5 ft), bulk dielectric constant 8.8 + 3.7j, and various void ratios. The results indicate that estimates of the void ratio by remote electromagnetic measurements may be feasible under favorable conditions, but many technical problems remain to be overcome before quantitative determinations are possible.