Method and apparatus for measuring the electrical resistivity of geologic formations through metal drill pipe or casing

Patent · Tue Jun 06 00:00:00 EDT 1989

OSTI ID:5719947

Gard, M F; Kingman, J E.E.; Klein, J D

This patent describes a system for determining the resistivity of an earth formation by measuring voltage differentials along a metal conduit penetrating the formation. The system consists of: an electrical potential sources having a first electrode, means for electrically connecting the first electrode to the conduit and a second electrode connected to the formation at a distance from the conduit; a first set of spaced apart contactors for detecting voltages between first and second points in the conduit; a differential amplifier having input conductors coupled to the first set contactors, respectively, and having an output conductor; an inverter circuit having an input conductor to the differential amplifier output conductor and having an inverter output conductor; switching means having a first input conductor connected to the differential amplifier output conductor, a second input conductor connected to the inverter output conductor, a control input conductor and a switching means output conductor. The switching means being operable to alternately couple the first and second input conductors to the switching means output conductor; and signal averaging means having an input conductor connected to the switching means output conductor and an averaging means output conductor for conducting a signal indicating the differential voltage along the conduit between the first set of connectors.

• Assignee: Atlantic Richfield Co., Los Angeles, CA
• Patent Number(s): US 4837518
• OSTI ID: 5719947
• Resource Relation: Patent File Date: 18 Aug 1987
• Country of Publication: United States
• Language: English

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WELL LOGGING EQUIPMENT
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EXPLORATION
GEOPHYSICS
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