APPARATUS AND METHODS FOR MEASURING SPONTANEOUS POTENTIAL OF AN EARTH FORMATION

An apparatus for measuring spontaneous potential (SP) of an earth formation includes a downhole tool that is moveable within a borehole by conveyance means. A portion of the conveyance means produces a reference DC potential signal. The tool includes a measurement electrode that produces a potential...

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Bibliographic Details
Main Authors CHEN MIN-YI, CASTON ANDREW, LAC ÉTIENNE, TARVIN JEFFREY A
Format Patent
LanguageEnglish
Published 11.12.2014
Subjects
DETECTING MASSES OR OBJECTS
GEOPHYSICS
GRAVITATIONAL MEASUREMENTS
MEASURING
PHYSICS
TESTING
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Summary:An apparatus for measuring spontaneous potential (SP) of an earth formation includes a downhole tool that is moveable within a borehole by conveyance means. A portion of the conveyance means produces a reference DC potential signal. The tool includes a measurement electrode that produces a potential signal representative of SP of the earth formation. The tool also includes circuitry that measures a differential DC potential signal between the potential signal produced by the measurement electrode and the reference DC potential signal. SP data that characterizes SP of the earth formation is generated based upon the output of such circuitry. In one embodiment for a while-drilling tool, the conveyance means and tool are realized by a drill string with an insulative sleeve that supports the measurement electrode and electrically isolates the measurement electrode from the drill string. Other embodiments for while-drilling tools and tools for tough logging conditions are also described.
Bibliography:Application Number: US201313912133