Passive, active and semi-active cancellation of borehole effects for well logging

Methods and apparatus for making subsurface measurements with reduced or eliminated borehole effects. Antenna and electrode configurations address the undesired axial electric currents that are induced along the borehole when antennas with tilted or transverse axes are used to make electromagnetic m...

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Bibliographische Detailangaben
Hauptverfasser: ROSTHAL RICHARD A, SMITS JAN WOUTER
Format: Patent
Sprache:eng
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Beschreibung
Zusammenfassung:Methods and apparatus for making subsurface measurements with reduced or eliminated borehole effects. Antenna and electrode configurations address the undesired axial electric currents that are induced along the borehole when antennas with tilted or transverse axes are used to make electromagnetic measurements. Current and measure electrodes are used in combination with antennas to limit the flow of undesired axial borehole currents. Embodiments use passive, active, or semi-active electrodes to limit the undesired current flow.