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Drilling with concentric strings of casing

  • US 7,131,505 B2
  • Filed: 02/22/2005
  • Issued: 11/07/2006
  • Est. Priority Date: 12/30/2002
  • Status: Expired due to Fees
First Claim
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1. A drill bit assembly for setting concentric casing strings within a wellbore, comprising:

  • drill bit pieces which are releasably connected to one another, wherein a first force required to release a first connection between outermost ones of the drill bit pieces is weaker than a second force required to release a second connection between innermost ones of the drill bit pieces,wherein the innermost ones of the drill bit pieces define a smaller outer diameter than the outermost ones of the drill bit pieces,wherein the innermost ones of the drill bit pieces are configured to enable drilling of a smaller diameter hole corresponding to the smaller outer diameter of the innermost ones of the drill bit pieces once the first connection is released.

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