Drilling with concentric strings of casing
First Claim
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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Accused Products
Abstract
The present invention provides a method and apparatus for setting concentric casing strings within a wellbore in one run-in of a casing working string. In one aspect of the invention, the apparatus comprises a drilling system comprising concentric casing strings, with each casing string having a drill bit piece disposed at the lower end thereof. The drill bit pieces of adjacent casing strings are releasably connected to one another. In another aspect of the invention, a method is provided for setting concentric casing strings within a wellbore with the drilling system. In another aspect of the invention, the releasably connected drill bit pieces comprise a drill bit assembly.
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Citations
17 Claims
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1. A drill bit assembly for setting concentric casing strings within a wellbore, comprising:
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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. - View Dependent Claims (2, 3, 4, 5)
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6. A drill bit assembly, comprising:
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a first drill bit piece defining an initial outer diameter for drilling a first hole corresponding to the outer diameter of the first drill bit piece; a second drill bit piece which is releasably connected to the first drill bit piece, wherein a first force is required to release a first connection between the first and second drill bit pieces, the second drill bit piece configured to enable drilling of a second hole smaller in diameter than the first hole once the first connection is released; and a third drill bit piece which is releasably connected to the second drill bit piece, wherein a second force greater than the first force is required to release a second connection between the second and third drill bit pieces, the third drill bit piece configured to enable drilling of a third hole smaller in diameter than the second hole once the second connection is released. - View Dependent Claims (7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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Specification