Methods and apparatus for measurement of electronic properties of geological formations through borehole casing

Patent · Tue Jan 01 04:00:00 EST 1991

OSTI ID:867955

Methods and apparatus are provided for measuring electronic properties of geological formations and cement layers adjacent to cased boreholes including resistivities, polarization phenomena and dielectric constants. 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. At least three 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 differential current conducted into formation in the vicinity of those electrodes. These measurements facilitate calculation of the resistivities of the adjacent geological formations as well as an indication of whether cement is present. Measurements of the differential voltage response to transient currents provide a measurement of the polarization phenomena in formation as well as the capacitance of the casing in contact with the formation which is useful for determining whether oil and gas present. Lithological characteristics of the formation such as the pressence or absence of clay can also be determined. A calibration procedure is provided for minimizing errors induced by variations in the casing. The device also may be placed within the pipe attached to a drill bit while drilling open holes.

• Research Organization: ParaMagnetic Logging, Inc. (Bothell, WA)
• DOE Contract Number: FG06-84ER13294
• Assignee: ParaMagnetic Logging Inc. (Woodinville, WA)
• Patent Number(s): US 5043668
• OSTI ID: 867955
• Country of Publication: United States
• Language: English

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absence
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bit
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gas
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