Patent ID: 6032739
Filing Date: 2000-03-07
Classification: E21B

Abstract:
A method of employing a dual-purpose magnet in servicing a wellbore, said wellbore having a plurality of casing pipes interconnected by a plurality of casing collars, said method comprising:lowering a housing having a longitudinal centerline into said plurality of casing pipes, said housing holding a dual-purpose magnet having a center of gravity that is radially offset in a forward direction to said longitudinal centerline, said housing holding a coil that is exposed to a magnetic field of said dual-purpose magnet;drawing said housing toward an inner wall of said plurality of casing pipes by way of a radial force provided mostly by said dual-purpose magnet, thereby providing a first purpose of said dual-purpose magnet;lowering said dual-purpose magnet past one casing collar of said plurality of casing collars;disturbing said magnetic field as a result of lowering said dual-purpose magnet past said one casing collar;generating an electrical signal from said coil primarily as a consequence of said magnetic field being disturbed, thereby providing a second purpose of said dual-purpose magnet; andidentifying a location of said one casing collar along said wellbore based upon said electrical signal.