Identification of ferrous changes in piping deployed in a wellbore

A method and apparatus for detecting ferrous changes (90, 95) passing axially through a cylindrical space comprises surrounding the space with a non-magnetic cylinder (110) and creating an alternating magnetic field in the cylindrical space by means of a permanent magnet (20) rotatable by a motor (4...

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Bibliographische Detailangaben
Hauptverfasser:	MAHENDRAN S RELTON, JASON P MACINNES, JONATHAN J FALCON, JOHN S BURLINGTON
Format:	Patent
Sprache:	eng
Schlagworte:	EARTH DRILLING EARTH DRILLING, e.g. DEEP DRILLING FIXED CONSTRUCTIONS INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIRCHEMICAL OR PHYSICAL PROPERTIES 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 method and apparatus for detecting ferrous changes (90, 95) passing axially through a cylindrical space comprises surrounding the space with a non-magnetic cylinder (110) and creating an alternating magnetic field in the cylindrical space by means of a permanent magnet (20) rotatable by a motor (40). Sensors (30) detect magnetic field changes as the ferrous matter passes axially through the cylindrical space. The apparatus may be used for detecting tool joints (90) that connect a tubing string (95) as the tubing string is moved in or out of a wellbore, or the presence or absence of a coiled tubing string in the wellbore. The permanent magnet provides a safe field generating means within a hostile well environment.