Improved apparatus of coupling wall to investigate by microinductividad landforms

摘要

A wall-engaging apparatus for microinductively investigating a characteristic of earth formation traversed by a borehole includes an antenna set mounted in a longitudinally elongated body adapted for a sliding engagement with the wall of the borehole. The antenna set includes a first antenna element, and second and third antenna elements, having locations and orientations to place them in electromagnetic symmetry relative to the first antenna element. Means are included for differentially coupling the second and third antenna elements. Either the first antenna element or the differentially-coupled second and third antenna elements may be energized to function as a transmitter, while the other functions as a receiver of signals indicative of the characteristic. Alternative variations include a conductive body for focussing electromagnetic energy, a coductive backplane which enables half-loop antenna elements and an electroquasistatic shield which improve the performance of the antenna set.