Boring or penetrating the earth – Bit or bit element – Rolling cutter bit or rolling cutter bit element
Reexamination Certificate
1999-03-11
2001-11-06
Bagnell, David (Department: 3672)
Boring or penetrating the earth
Bit or bit element
Rolling cutter bit or rolling cutter bit element
C175S393000
Reexamination Certificate
active
06311793
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a nozzle and retainer assembly for use in rotary cone earth boring bits. In one aspect, the present invention relates to a nozzle and retainer assembly that allows for a larger fluid passage in the nozzle and for orientation of the nozzle relative to the bit.
BACKGROUND OF THE INVENTION
Earth boring bits used for drilling holes in the earth are typically classified into two types: drag bits which have no moving parts and shear the formation (e.g. polycrystalline diamond compact (PDC) bits, diamond impregnated bits, etc.) and rotary cone bits which have one or more generally conic roller cones rotatably mounted on the bit body. The roller cones have cutting teeth and/or inserts extending therefrom and rotation of the bit body rotates the cones so that the cutting teeth and/or inserts crush and gouge the formation.
Both of these types of bits use nozzles mounted on the bit body to direct drilling fluid coming down the drill string to sweep the bottom of the borehole and carry cuttings back up the hole on the outside of the drill string. This fluid flow, or “bit hydraulics”, serves three primary purposes: cutting removal, relief of chip hold down pressure, and, in the case of rotary cone bits, cleaning of the cones. The location and type of the nozzles used can greatly impact these purposes.
Location of the nozzles relative to the borehole bottom is especially relevant to rotary cone bits versus drag bits. Because the face of the drag bit body is directly against the formation, the nozzles in a drag bit are readily located near the borehole bottom by mounting of a nozzle in a receptacle in the bit body. In contrast, the bit body of a rotary cone bit is disposed above the bottom of the formation by the rotary cones and thus fluid exiting from a nozzle recessed or flush with the bit body must travel a significant distance before impinging at or near the borehole bottom. Moving the nozzle exit closer to the hole bottom can generally improve chip removal by increasing the bottom hole energy and by improving the ability of the fluid to relieve chip hold-down pressures.
One way the exit orifice of nozzles in rotary cone bits have been moved closer to the borehole bottom is by using steel tubes that extend from the bit body with a wear-resistant nozzle mounted in the end of the tube. These extended nozzle tubes have the advantage of being able to closely locate the exit orifice of the nozzle close to the borehole bottom; however, the extended tubes are susceptible to breaking. A tube breaking off of the bit effectively ends the run of that particular bit and may require a costly down hole fishing (retrieving) operation to remove the tube from the bottom of the borehole.
Another way that the exit orifice has been moved closer to the borehole bottom is by the use of “mini-extended” nozzles. Conventional nozzles are generally flush or recessed from the outer surface of the receptacle in the bit body in which they are mounted. Mini-extended nozzles have a portion which extends beyond the receptacle in which it is mounted but still are retained by conventional nozzle retention means. With reference to
FIG. 1
, a conventional mini-extended nozzle
10
is shown mounted in receptacle
12
defined in bit body assembly
14
with fluid bore
15
. Nozzle
10
defines passage
16
for the direction of drilling fluid through the nozzle. Receptacle
12
conventionally has a standard inner diameter for a given size bit. Retainer
18
threads into receptacle
12
at threaded connection
24
and retains nozzle
10
in receptacle
12
by capturing shoulder
20
of nozzle
10
by ledge
22
extending radially inward from retainer
18
. Nozzle
10
seats on shoulder
26
in receptacle
12
. Seal
28
seals between the outer surface of nozzle
10
and the inside of receptacle
12
. Nozzle
10
is referred to as a “mini-extended” nozzle due to the fact that the nozzle has portion
11
extending beyond receptacle
12
. The outer diameter of portion
11
is smaller than the outer diameter of base portion
13
of nozzle
10
in order to extend beyond ledge
22
of retainer
18
. The advantage of mini-extended nozzles is their relative durability and ruggedness compared to extended tubes; however, a mini-extended nozzle does not locate the nozzle orifice as close to the borehole bottom as an extended tube.
U.S. Pat. No. 5,669,459 discloses a retention body for holding a mini-extended nozzle closer to the borehole bottom. This design has the advantage of better protecting the mini-extended nozzle during operation by extending a mild steel retention body along the portion of the nozzle that extends beyond the body of the bit. By better protecting the nozzle, the orifice of the nozzle can be moved closer to the borehole bottom compared to a mini-extended nozzle mounted in a conventional receptacle while at the same time avoiding the potential breakage problems associated with extended tubes.
Thus for a rotary cone bit, the mini-extended nozzle can be used in a conventional receptacle for some extension, with a retention body of the '459 patent for additional extension, or with an extended tube for even more extension but with risk of tube breakage.
In addition to location of the nozzle in the axial direction (i.e., distance from borehole bottom), the type of nozzle used impacts the goals of chip removal, relief of chip hold down pressure, and cone cleaning. More specifically, the nozzle passageway and orifice can effect bit hydraulics. U.S. Pat. No. 5,494,124 (as well as related patents U.S. Pat. Nos. 5,632,349; and 5,653,298) discloses a type of nozzle with a passageway and orifice design that is purported to provide advantages over other nozzles when used in an earth boring bit. FIGS. 1, 3, and 5 of the '124 patent show the shaped orifices (slot 16, 46, and 76, respectively) while FIGS. 2, 4, and 6 of the '124 patent show the corresponding internal passage 20, 50, 80, respectively.
With reference to FIG. 2, an embodiment of nozzle 10′ of the type disclosed in the '124 patent is shown in receptacle 12 with retainer 18 capturing end 21 of nozzle 10′. Nozzle 10′ is recessed from the opening of receptacle 12. Passage 16′ has transition zone 29 that transitions from passage 16′ to orifice 31. The '124 patent teaches particular shapes of transition zone 29 and orifice 31 to achieve the desired fluid characteristics for the nozzle.
One disadvantage of the nozzle of the '124 patent is that its internal passage 16′ must be much larger than that of a conventional nozzle to allow sufficient room for the desired short transition zone 29 with its high rate of inward taper to orifice 31, especially for larger sized nozzle orifices. The standard receptacle 12 in a bit together with the retention means used to hold the nozzle in the receptacle limits the maximum outer envelope of the nozzle, and this together with the minimum acceptable wall thickness of the nozzle limits the maximum size of internal passage 16′ of the nozzle. Thus, for a given receptacle 12, the maximum nozzle orifice size achievable by the '124 nozzle will be appreciably less than that of a conventional nozzle. This is a disadvantage because standard drilling practices often require larger nozzle orifices to reduce the pressure drop across the bit. The inability to accommodate larger nozzle orifices makes the nozzles of the '124 patent less versatile and unable to be used in certain drilling applications that may require a pressure drop that is less than that available with the largest '124 nozzle for the particular receptacle in the bit.
This disadvantage of the '124 nozzle is compounded when it is desired to take advantage of the mini-extended nozzle concept by extending the end of the nozzle beyond the receptacle in which it is mounted. Retainer 18 used with mini-extended nozzle 10 in FIG. 1 requires a reduced outer diameter of extended portion 11. This reduced diameter even more severely restricts th
Larsen James L.
Siracki Michael A.
Bagnell David
Dougherty Jennifer
Noah Wesley T.
Smith International Inc.
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