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Steerable drilling system and method

  • US 7,621,343 B2
  • Filed: 07/24/2006
  • Issued: 11/24/2009
  • Est. Priority Date: 12/21/1998
  • Status: Expired due to Fees
First Claim
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1. A method, comprising:

  • drilling a deviated borehole using a bottom hole assembly while rotating a drill string from the surface, the bottom hole assembly having a rotary shaft of a rotary steerable device rotatable within a rigid housing extending from an upper shaft bearing positioned within the rigid housing to an intersection of a central axis of the rigid housing and a central axis of a lower deflected portion of the rotary shaft, the lower portion of the rotary shaft being deflected in response to a deflection device;

    coupling an anti-rotation device to the rigid housing of the rotary steerable device;

    the deflection device deflecting the rotary shaft by a transverse force acting between the rotary shaft and the rigid housing;

    using a bit coupled to the rotary shaft to drill the deviated borehole, the bit having a bit face, the bit face having a bit full cutting diameter; and

    using a gauge section above the bit face, such that an axial length between the bit full cutting diameter and a top of the gauge section is at least 75% of the bit full cutting diameter.

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