Methods and apparatus for measurement of the resistivity of geological formations from within cased wells in presence of acoustic and magnetic energy sources

Patent · Tue Jan 01 04:00:00 EST 1991

OSTI ID:867956

Methods and apparatus are provided for measuring the acoustically modulated electronic properties of geological formations and cement layers adjacent to cased boreholes. Current is passed from an electrode in electrical contact with the interior of the borehole casing to an electrode on the surface of the earth. Voltage measuring electrodes in electrical contact with the interior of the casing measure the voltage at various points thereon. The voltage differences between discrete pairs of the voltage measuring electrodes provide a measurement of the leakage current conducted into formation in the vicinity of those electrodes. Simultaneously subjecting the casing and formation to an acoustic source acoustically modulates the leakage current measured thereby providing a measure of the acoustically modulated electronic properties of the adjacent formation. Similarly, methods and apparatus are also described which measure the leakage current into formation while simultaneously subjecting the casing to an applied magnetic field which therefore allows measurement of the magnetically modulated electronic properties of the casing and the adjacent formation.

• Research Organization: ParaMagnetic Logging, Inc. (Bothell, WA)
• Sponsoring Organization: USDOE - Office of Science (SC)
• DOE Contract Number: FG06-84ER13294; FG22-88BC14243
• Assignee: Para Magnetic Logging, Inc. (Woodinville, WA)
• Patent Number(s): US 5043669
• OSTI ID: 867956
• Country of Publication: United States
• Language: English

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