Aquifer Characterisation with Airborne Frequency Domain Electromagnetic Surveying - Case Studies from Ireland and Oman

Sander Geophysics has modernized its frequency domain electromagnetics (FDEM) survey systems. The SGEM system was installed on a DHC-6 Twin Otter aircraft with four horizontal coplanar coil pairs. Each pair’s respective transmitter and receiver coil are mounted on opposite wingtips. The aircraft can be equipped with multiple survey payloads, to concurrently measure electromagnetics, magnetics, gravity, and radiometrics. This setup is ideal for the mapping large project areas and can survey over built up areas inaccessible to towed-sensor airborne systems. Case studies of FDEM surveys from Ireland and Oman highlight the potential of using FDEM for ground water exploration. Apparent resistivity maps of Ballincollig, Ireland (west of Cork) showed low resistivity, weakly conductive, regions correlating well with a known, regionally significant, fresh-water aquifer. A four-layer inversion model from the FDEM data collected over Ghuzayn, Oman provides an estimation of the depth to the ground water table. It has been interpretated as horizontally laying, weakly conductive layer at depths from the surface as shallow as 30 m which is supported by ground water flooding of the Ghuzayn mine entrance.