Downhole three component TEM probes

Abstract

A three component transient electromagnetic (TEM) probe (VECTEM) has been constructed to eliminate rotational ambiguities associated with data obtained along a single axis. Individual components are obtained sequentially using a surface adapter for multiplexing to any standard TEM recorder. The critical rotation angles are also indicated by this surface unit and are recorded in the data header. Data have been obtained for several sites and interpretations have been generated using filament inversion routines. The results agree in general with previous axial data and are consistent with geological constraints. However noise levels are higher than expected compared to single-component probes and anomalies confined to late windows may remain obscured.