Electricity: measuring and testing – Of geophysical surface or subsurface in situ – Using electrode arrays – circuits – structure – or supports
Patent
1989-10-30
1991-08-27
Wieder, Kenneth A.
Electricity: measuring and testing
Of geophysical surface or subsurface in situ
Using electrode arrays, circuits, structure, or supports
G01V 320
Patent
active
050436686
ABSTRACT:
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.
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Edmonds Warren S.
ParaMagnetic Logging Inc.
Wieder Kenneth A.
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