Boring or penetrating the earth – Bit or bit element – Bit with leading portion forming smaller diameter initial bore
Reexamination Certificate
1999-12-07
2001-10-09
Neuder, William (Department: 3672)
Boring or penetrating the earth
Bit or bit element
Bit with leading portion forming smaller diameter initial bore
C175S399000
Reexamination Certificate
active
06298929
ABSTRACT:
RELATED APPLICATION
This application claims the benefit of Mexican Patent Application No. 9810459 filed on Dec. 10, 1998.
TECHNICAL FIELD OF THE INVENTION
The present invention relates to drill bits for enlarging the diameter of a bore hole, and more specifically to a bi-center bit passing through a smaller diameter segment of the bore hold for enlarging the bore hole below the smaller diameter segment.
BACKGROUND OF THE INVENTION
In conventional drilling of bore holes for oil and gas recovery, there is often a necessity to isolate different types of formations with casing pipe to prevent cave-in of the bore hole walls and for loss of fluid, both during the drilling operation and recovery operation of the well. Currently, the predominant drill bit used by the well-drilling industry is the tri-cone rotary drill bit for oil and gas wells and water wells.
During a drilling operation, the size of the drill bit is many times limited by the inside diameter of the casing pipe previously introduced into the well. This requires a subsequent drill bit introduced into a well to have an exterior diameter somewhat smaller than the inside diameter of the previously introduced casing pipe, resulting in a bore hole having smaller diameters as the depth of the well proceeds. In drilling a typical well, a large diameter bit is routinely used to drill the upper portion of the hole to a first depth for a first casing string. A smaller diameter bit which will pass through the first casing string is then used to drill to a depth where a second casing string is introduced into the well. This continues until the depth of the well is achieved. In addition to requiring the use of various size bits with the attendant costs of drill bits and operational costs, the result is a bore hole having an effective diameter governed by the smallest diameter bit used in the drilling operation.
Heretofore, the drilling industry has utilized an eccentric bit, or a bi-center bit, to enlarge a bore hole below a tighter undersized segment, such as a previously introduced section of casing pipe. An eccentric bit includes an extended or enlarged cutting portion which, when the bit is rotated about its axis, produces an enlarged bore hold. A bi-center bit heretofore in use by the drilling industry employs two longitudinally spaced bit sections with laterally offset axes. The first axis is the center of the pass-through diameter, that is, the diameter of the smallest bore hole that the bi-center bit will pass through. The second axis is the axis of the hole as the bit is rotated.
Examples of bi-center bits are disclosed in U.S. Pat. Nos. 4,706,765 and 5,765,653.
SUMMARY OF THE INVENTION
In accordance with the present invention, there is provided an improved bi-center rotary cone bit having at least one cutter for enlarging a bore hole after passing through a restricted section, such as casing pipe.
Further, the improved bi-center bit of the present invention includes a cylindrical body having an internal fluid channel and at least one drill bit mounted to one side of the cylindrical body. The drill bit includes at least one cutting element. A nozzle in the surface of the cylindrical body communicates with the internal fluid channel with the nozzle positioned to direct a stream of fluid ahead on the cutting element of the drill bit. To stabilize the bi-center bit against vibration, a stabilizer is mounted to the cylindrical body in a position substantially opposite that of the drill bit.
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patent: 4706765 (1987-11-01), Lee et al.
patent: 5678644 (1997-10-01), Fielder
patent: 5765653 (1998-06-01), Doster et al.
patent: 5957223 (1999-09-01), Doster et al.
patent: 5992548 (1999-11-01), Silva et al.
patent: 6039131 (2000-03-01), Beaton
Baker & Botts L.L.P.
Neuder William
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