Patent ID: 7330397
Filing Date: 2008-02-12
Classification: E21B

Abstract:
1. A mud-pulse telemetry tool, comprising: a tool housing; a motor disposed in the tool housing; a magnetic coupling coupled to the motor and having an inner shaft and an outer shaft; a stator coupled to the tool housing; a restrictor disposed proximate the stator and coupled to the magnetic coupling, the restrictor and the stator adapted to generate selected pulses in a drilling fluid when the restrictor is selectively rotated; a first anti-jam magnet coupled to the tool housing; and an second anti-jam magnet disposed proximate the first anti-jam magnet and coupled to one selected from the inner shaft and the outer shaft, wherein at least one of the first anti-jam magnet and the second anti-jam magnet is an electromagnet, and wherein the first anti-jam magnet and the second anti-jam magnet are positioned with adjacent like poles.