GAIN STABILIZED NATURAL GAMMA RAY DETECTION OF CASING THICKNESS IN A BOREHOLE

A gain stabilized natural gamma ray spectroscopy system is used to measure casing thickness in a cased well borehole. A ratio of gamma ray intensity in two selected energy ranges forms a measurement signal representative of casing thickness based on the photoelectric absorption of natural gamma rays...

Ausführliche Beschreibung

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Bibliographische Detailangaben
Hauptverfasser:	ROBBINS, CARL ARTHUR, SMITH, HARRY DAVIS, JR
Format:	Patent
Sprache:	eng
Schlagworte:	DETECTING MASSES OR OBJECTS EARTH DRILLING EARTH DRILLING, e.g. DEEP DRILLING FIXED CONSTRUCTIONS GEOPHYSICS GRAVITATIONAL MEASUREMENTS MEASUREMENT OF NUCLEAR OR X-RADIATION MEASURING MINING OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR ASLURRY OF MINERALS FROM WELLS PHYSICS TESTING
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Beschreibung
Zusammenfassung:	A gain stabilized natural gamma ray spectroscopy system is used to measure casing thickness in a cased well borehole. A ratio of gamma ray intensity in two selected energy ranges forms a measurement signal representative of casing thickness based on the photoelectric absorption of natural gamma rays by iron. A coincidence technique employing dual scintillation crystals (51, 57) and a stabilization source (58) of charged particles and known energy gamma rays is used for gains stabilization, the particles and gamma rays coincidentally-emitted by this source (58) being detected by the respective crystals (57, 51) and a circuit (64) testing for coincidence so that the gain stabilization can be effected in accordance with the measured value of these known energy gamma rays.