Abstract: The porosity and permeability of a geological formation (2) are determined on the basis of an electrofiltering phenomenon by exploiting the existence of non-linear electrofiltering phenomena. One or two pressure generators (11 ) are used to propagate a pressure wave in the formation. Electrodes (14, 15) applied against the wall of the formation pick up the electric response of the formation. The detection of a resonance frequency or a phase shift corresponding to an extremum of the electric response of the formation makes it possible to calculate the porosity or permeability of the formation or find their values from charts.

Abstract: A microdevice is provided for measuring the electromagnetic characteristics of a medium in a borehole. The microdevice includes at least one emitting or transmitting coil (31), and at least one receiving coil (41,51). The microdevice generates an A.C. voltage at the terminals of the transmitting coil and measures a signal at the terminals of the receiving coil. The microdevice also includes an E-shaped electrically insulating, soft magnetic material circuit serving as a support for each of the coils and which is positioned adjacent to the medium in the borehole.

Abstract: A nuclear magnetic resonance probe is provided comprising a high frequency resonator (14, 16) having a resonant frequency, a first coaxial conductor (20) connected to the high frequency resonator, and a high frequency supply which supplies the first coaxial conductor (20) the resonant frequency of the high frequency resonator (14, 16). The high frequency supply includes a conductive sampling loop (40) at least partly placed in the high frequency resonator (14, 16) and a broad band, high frequency, amplifier (56) having an input (E) connected to the sampling loop (40) by a second coaxial conductor (50) and an output (S) connected to the first coaxial conductor (20). The assembly forming a high frequency loop oscillator locked to the resonant frequency of the high frequency resonator (14, 16).

Abstract: A NMR magnetometer probe having a single resonator and a single radical solution. A single bottle contains the single radical solution. Further, a single resonator is tuned to one of the electric resonance frequencies of the solution. Such an NMR magnetometer probe may find particular application to the measurement of magnetic fields.

Abstract: A nuclear magnetic resonance probe incorporating at least two bottles with radical solutions, one having a positive nuclear polarization and the other a negative nuclear polarization, at least one high frequency coaxial resonator around each bottle respectively, an assembly of low frequency exciting-sampling coils. The coil assemblies are interconnected and connected to an amplifier in a loop oscillator connection. The probe comprises two blocks having a symmetry of revolution with respect to one axis and a symmetry with respect to a plane perpendicular to the axis of revolution. Each block incorporates at least one bottle having a shape of revolution about the axis and is symmetrical with respect to the plane of symmetry and a coaxial resonator having the same symmetries as the bottle. Each block contains the bottle, a double frequency coil of revolution about the axis and completely surrounds the resonator and the bottle.

Abstract: A coaxial resonator with a distributed tuning capacity. The resonator includes one outer conductor and one central conductor, both conductors having a symmetry of revolution around a predetermined central axis. The tuning capacitor is fully distributed along the axis of the resonator and includes at least two cylindrical armatures nested into each other and having the axis of the resonator as their central axis, one of the two armatures constituting one of the two conductors of the resonator. The coaxial resonator may find particular application for RMN magnetometer probes.

Abstract: The bottle according to the invention comprises a double wall (34, 36) defining a coaxial volume (38) corresponding to the "bubble" to be left after filling. In normal operation, the liquid is ejected from said volume and occupies the remainder of the bottle.