Electromagnetic techniques for mapping an underground coal gasification process. Final report, January 1, 1978-December 31, 1979

An electromagnetic system, operating in reflection and transmission mode schemes, has been designed to monitor an underground coal seam gasification process. The overall dimensions of some system components have been restricted so that they may be placed inside a six-inch diameter borehole. Radiating elements have been designed, built, and tested to be used with the reflection and transmission mode schemes in the 174-216 MHz frequency range to monitor an underground coal gasification process within a thin (approx. = 6 feet height) coal seam. The system has been tested in a laboratory, with restricted physical dimensions, to validate some of its design concepts. In addition numerical algorithms and computer programs have been developed to map, from the transmission mode scheme measurements, the underground process and its surrounding environment. 20 references, 43 figures, 9 tables.