Well logging system arranged for stable, high-sensitivity reception of propagating electromagnetic waves

A logging apparatus for use in interrogating a borehole and surrounding formation, comprising:

• a housing;
• a plurality of transmitter antennas carried by said housing;
• a plurality of receiver antennas carried by said housing;
• at least one oscillator circuit, which is electrically coupled to said plurality of transmitter antennas for selectively energizing particular ones of said plurality of relatively closely spaced transmitter antennas;
• at least one controller which is electrically coupled to said at least one oscillator circuit;
• a reception circuit for utilizing said plurality of receiver antennas in measuring at least one attribute of at least one of (a) said borehole and (b) said surrounding formation and providing digital data to said at least one controller;
• said at least one controller being operable in a plurality of modes of operation, including:
• (1) a transmission mode of operation, wherein said at least one controller provides commands in response to program instructions, to produce an analog signal from said analog output of said at least one oscillator having a particular frequency for energizing said plurality of transmitter antennas to initiate propagation of an interrogating electromagnetic field, having an interrogation frequency, through said borehole and surrounding formation;
• and
• (2) a reception mode of operation, wherein said at least one controller samples measurements of at least one attribute of said interrogating electromagnetic field, made utilizing at least a particular one of said plurality of receiver antennas and recording said measurements.

A logging apparatus for use in a wellbore for measuring an attribute of at least one of (a) said wellbore, and (b) a surrounding formation, when suspended in said wellbore, comprising:

• a housing;
• a plurality of transmitters carried by said housing, each transmitter being individually and selectively operable for producing an electromagnetic interrogating signal at a selected interrogation frequency for passage through said wellbore and said surrounding formation;
• at least one receiver, carried by said housing in a selected position relative to said plurality of transmitters, each receiver being tuned to receive electromagnetic signals at said interrogation frequency to the exclusion of other frequencies;
• wherein a portion of said at least one of (a) said wellbore, and (b) said surrounding formation has an attribute value which can be derived from at least one of (a) amplitude attenuation of said electromagnetic interrogating signal as determined from measurements of said electromagnetic interrogating signal taken through said at least one receiver, and (b) phase shift of said electromagnetic interrogating signal as determined from measurements of said electromagnetic interrogating signal taken through said at least one receiver;
• means for sampling signals from said at least one receiver;
• a controller member for (a) selectively energizing selected pair of said plurality of transmitters causing said electromagnetic interrogating signals to pass through said wellbore and said surrounding formation to said at least one receiver, (b) or selectively obtaining measurements of said electromagnetic interrogating signals from said at least one receiver with said means for sampling, (c) selectively obtaining measurements of said electromagnetic interrogating signals from said at least one receiver with said means for sampling;
• and (d) mathematically combining a plurality of measurements in order to obtain measure of said attribute value.

A method of measuring in a wellbore an attribute of at least one of (a) said wellbore, and (b) a surrounding formation, comprising the method steps of:

• providing a housing;
• locating a plurality of transmitters on said housing, each transmitter being individually and selectively operable for producing an electromagnetic interrogating signal at a selected interrogation frequency for passage through said wellbore and said surrounding formation;
• locating at least one receiver on said housing in a selected position relative to said plurality of transmitters, each receiver being tuned to receive electromagnetic signals at said interrogation frequency to the exclusion of other frequencies;
• securing said housing in a selected location within a drillstring;
• providing a controller member;
• utilizing said drillstring to advance said wellbore by disintegrating said formation during drilling operations;
• at selected intervals during drilling operations, utilizing said controller member for selectively energizing said plurality of relatively closely spaced transmitters causing said electromagnetic interrogating signal to pass through said wellbore and said surrounding formation in a particular direction relative to said at least one receiver;
• selectively obtaining measurements of said electromagnetic interrogating signal from said at least one receiver and recording in memory a plurality of samples;
• and
• determining an accurate measure of said attribute value by combining a plurality of said plurality of samples.