Patent ID: 6924640
Filing Date: 2005-08-02
Classification: E21B,G01N

Abstract:
1. In a well borehole, a system for measuring a flaw in a ferromagnetic tubular within said borehole, the system comprising: (a) a tool conveyable within said tubular; (b) a pad array disposed in said tool and comprising a plurality of pads; (c) means for urging each of said plurality of pads against an inner wall of said tubular; (d) a plurality of Hall effect sensors disposed in each of said pads, wherein each said pad comprises at least two said Hall effect sensors positioned, within each said pad, in a plane perpendicular to the major axis of said tool and at equal radial spacing and at equal distance from an outer surface of said pad; (e) circuitry for measuring responses of said Hall effect sensors to a saturated magnetic field induced within said tubular; and (f) located within said tool, a permanent magnet assembly comprising a core and two permanent magnetic poles disposed at opposing ends of said core thereby inducing said magnetic field within said tubular.