Abstract: A method of logging an underground formation from within a borehole includes the steps of emitting an electromagnetic signal from a first location in a borehole, determining a time at which the signal is emitted, detecting a direct component of the signal which has passed from the first location to a second location without being reflected, determining a time at which the direct component arrives at the second location and determining the speed of the signal in the underground formation from the time at which the signal is emitted, the time of arrival of the direct component and the spacing of the first and second locations. The speed of the signal can be used for radar logging of the formation.

Abstract: A two-dimensional array of slot antennas which can provide two-dimensional quantitative dielectric and conductivity images of formations in the region surrounding an earth borehole. The antennas are mounted in a wall-engaging member of a logging device that is moveable through the borehole. Selected ones of the antennas are energized at given times to transmit electromagnetic energy into the formations, the electromagnetic energy being received at other antennas for processing to obtain formation properties.