U.S. patent application number 09/788624 was filed with the patent office on 2001-10-18 for rock bit with improved nozzle placement.
Invention is credited to Campos, Harry Morales JR., Clydesdale, Graham MacDonald, Huffstutler, Alan Dee, Spatz, Edward Charles, Tso, Lawrence Lee.
Application Number | 20010030066 09/788624 |
Document ID | / |
Family ID | 22038274 |
Filed Date | 2001-10-18 |
United States Patent
Application |
20010030066 |
Kind Code |
A1 |
Clydesdale, Graham MacDonald ;
et al. |
October 18, 2001 |
Rock bit with improved nozzle placement
Abstract
A rotary cone drill bit is provided with enhanced fluid flow
near the bottom of an associated borehole resulting in improved
removal of cuttings and other debris from the bottom of the
borehole. The drill bit includes a plurality of fluid passageways
extending from the bit body to the exterior of the drill bit. The
bit body may include an enlarged cavity with the fluid passageways
extending therefrom. One end of the cavity preferably includes an
opening to receive fluid from a drill string attached to the drill
bit. The end of the cavity opposite from the opening may have a
generally parabolic configuration. For one application, a web
member extends from the lower portion of the bit body, occupying a
void area between each cutter cone assembly. The web member
preferably contains a plurality of fluid passageways which direct
drilling fluid from the drill string, through the bit body, through
the web member, and exiting at nozzles adjacent to the bottom of
the associated borehole.
Inventors: |
Clydesdale, Graham MacDonald;
(Aberdeen, GB) ; Huffstutler, Alan Dee; (Aberdeen,
GB) ; Campos, Harry Morales JR.; (Grand Prairie,
TX) ; Spatz, Edward Charles; (Dallas, TX) ;
Tso, Lawrence Lee; (Glenn Heights, TX) |
Correspondence
Address: |
Groover & Associates p.c.
Suite 230
17000 Preston Road
Dallas
TX
75248
US
|
Family ID: |
22038274 |
Appl. No.: |
09/788624 |
Filed: |
February 16, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09788624 |
Feb 16, 2001 |
|
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|
09169371 |
Oct 9, 1998 |
|
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|
60061808 |
Oct 14, 1997 |
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Current U.S.
Class: |
175/339 ;
175/368; 175/393 |
Current CPC
Class: |
E21B 10/18 20130101 |
Class at
Publication: |
175/339 ;
175/368; 175/393 |
International
Class: |
E21B 010/18 |
Claims
What is claimed is:
1. A rotary cone drill bit for forming a borehole, comprising: a
bit body having an upper portion adapted for connection to a drill
string for rotation of the drill bit; a number of support arms
attached to the bit body and extending opposite from the upper
portion, each of the support arms having a spindle connected
thereto, each spindle projecting generally downwardly and inwardly
with respect to its associated support arm; a number of cutter cone
assemblies equal to the number of support arms and mounted
respectively on one of the spindles; an enlarged cavity formed
within the upper portion of the bit body for communicating fluids
between the drill string and the cavity; the bit body having a
lower portion opposite from the upper portion; more than four fluid
passageways formed in the bit body extending between the cavity and
the lower portion of the bit body; and a nozzle disposed in each of
the fluid passageways adjacent to the lower portion of the bit
body.
2. The drill bit as defined by claim 1 wherein the lower portion of
the bit body further comprises a generally convex exterior surface
formed thereon.
3. The drill bit as defined by claim 1 wherein each fluid
passageway further comprises: an opening adjacent to the lower
portion of the bit body; and the respective opening having a
threaded portion to receive the associated nozzle.
4. The drill bit as defined by claim 3 wherein the threaded portion
of each fluid passageway is identical in size to the threaded
portion of all other fluid passageways contained within the bit
body.
5. The drill bit as defined by claim 3 wherein the threaded portion
of at least one opening varies in size as compared to the threaded
portion of the other openings.
6. The drill bit as defined by claim 1 further comprising: the bit
body having a longitudinal axis corresponding generally with a
projected axis of rotation of the drill bit; at least six fluid
passageways extending through the bit body at a respective angle
relative to the longitudinal axis of the bit body; and at least one
nozzle positioned to direct fluid flow between each cutter cone
assembly and an adjacent cutter cone assembly.
7. The drill bit as defined in claim 1 wherein the cavity further
comprises a generally uniform inside diameter extending from the
opening to a position intermediate the bit body along a
longitudinal axis of the bit body.
8. The drill bit as defined in claim 1 further comprising each
nozzle having a respective outlet orifice of approximately the same
size.
9. The drill bit as defined in claim 1 further comprising each
nozzle having a respective outlet orifice and at least one nozzle
having an outlet orifice larger than the outlet orifice of the
other nozzles.
10. The drill bit as defined by claim 1 further comprising: the bit
body having a longitudinal axis corresponding generally with a
projected axis of rotation for the drill bit; first, second and
third support arms attached to the bit body and extending therefrom
with first, second and third cutter cone assemblies respectively
mounted on the support arms; the first and second support arms
mounted on the exterior of the bit body spaced radially
approximately one hundred ten degrees relative to each other; the
second and third support arms attached to the exterior of the bit
body and spaced radially from each other approximately one hundred
twenty degrees; and the third support arm and the first support arm
mounted on the exterior of the bit body and radially spaced
approximately one hundred thirty degrees from each other on the
exterior of the bit body.
11. The drill bit as defined in claim 1 further comprising: the bit
body having a longitudinal axis corresponding generally with a
projected axis of rotation of the drill bit; and at least one
nozzle disposed adjacent to the longitudinal axis having a fluid
flow rate which is substantially greater than the fluid flow rate
through the other nozzles.
12. The drill bit as defined in claim 1 further comprising: the bit
body having a longitudinal axis corresponding generally with a
projected axis of rotation of the drill bit; and each of the
nozzles spaced from the intersection of the longitudinal axis with
the lower portion of the bit body whereby fluid flow from the
nozzles is generally directed away from the axis of rotation of the
drill bit.
13. A rotary cone drill bit for forming a borehole, comprising: a
bit body having an upper portion adapted for connection to a drill
string for rotation of the drill bit; a number of support arms
attached to the bit body and extending opposite from the upper
portion; a number of cutter cone assemblies equal to the number of
support arms with each cutter cone assembly rotatably mounted on
one of the support arms; a void space formed between each cutter
cone assembly and the cutter cone assembly disposed adjacent
thereto; a web member extending from a lower portion of the bit
body and occupying the void space between each cutter cone
assembly; and a nozzle disposed in each fluid passageway adjacent
to a lower portion of the web member.
14. The drill bit of claim 13 wherein the web member further
comprises three blades with each blade disposed between adjacent
cutter cone assemblies.
15. The drill bit of claim 13 further comprising at least one fluid
passageway formed in the bit body and extending through the web
member.
16. A rotary cone drill bit for forming a borehole having a side
wall and a bottom comprising: a bit body having an upper portion
with a threaded connection formed on the exterior of the upper
portion for connecting the drill bit to a drill string for rotation
of the drill bit; a number of support arms attached to the bit body
and extending opposite from the upper portion, each of the support
arms having a spindle connected thereto, each spindle projecting
generally downwardly and inwardly with respect to its associated
support arm; a number of cutter cone assemblies equal to the number
of support arms with one of the cutter cone assemblies mounted
respectively on each spindle for engagement with the side wall and
bottom of the borehole; the bit body having a longitudinal axis
corresponding generally with a projected axis of rotation of the
drill bit; an enlarged cavity formed within the upper portion of
the bit body for communicating fluids between the drill string and
the cavity; the enlarged cavity having a generally cylindrical
configuration disposed along the longitudinal axis; the bit body
having a lower portion opposite from the upper portion; and at
least six fluid passageways formed in the bit body extending
between the cavity and the lower portion of the bit body.
17. The drill bit of claim 16 further comprising: at least six of
the fluid passageways extending through the bit body at an angle
relative to the longitudinal axis of the bit body; at least one
additional fluid passageway extending from the cavity along the
longitudinal axis to the lower portion of the bit body; and a
nozzle positioned in each fluid passageway to direct fluid flow
toward the bottom of the borehole;
18. The drill bit of claim 16 further comprising: one of the
nozzles located a first distance (R.sub.1) away from the
intersection of the lower portion of the bit body and the
longitudinal axis, with a first inside diameter (d.sub.1); one of
the nozzles located a second distance (R.sub.2) away from the
intersection of the member and the longitudinal axis, with a second
inside diameter (d.sub.2); the distance (R.sub.2) greater than the
distance (R.sub.1); and the inside diameter (d.sub.2) larger than
the inside diameter (d.sub.1) creating a drilling fluid flow away
from the longitudinal axis along the bottom of the borehole.
19. A rotary cone drill bit for forming a borehole comprising: a
bit body having an upper portion adapted for connection to a drill
string for rotation of the drill bit; a number of support arms
attached to the bit body and extending therefrom; a number of
cutter cone assemblies equal to the number of support arms with
each cutter cone assembly rotatably mounted on one of the support
arms; an enlarged cavity formed within the upper portion of the bit
body; the cavity having a first end defined in part by an opening
for communicating fluids between the drill string and the cavity;
the cavity having a second end disposed within the bit body; the
second end of the cavity having a generally parabolic
configuration; a number of fluid passageways formed in the bit body
extending between the second end of the cavity and a lower portion
of the bit body; and a nozzle disposed in each of the fluid
passageways adjacent to the lower portion of the bit body.
20. A rotary cone drill bit for forming a borehole comprising: a
bit body having an upper portion adapted for connection to a drill
string for rotation of the drill bit; a number of support arms
attached to the bit body and extending therefrom; a number of
cutter cone assemblies equal to the number of support arms with
each cutter cone assembly rotatably mounted on one of the support
arms; an enlarged cavity formed within the upper portion of a bit
body; the enlarged cavity having a first end defined in part by an
opening in the upper portion of the bit body for communicating
drilling fluids between the drill string and the cavity; the
enlarged cavity having a second end disposed within the bit body;
the bit body having a longitudinal axis corresponding generally
with a projected axis of rotation of the drill bit; a first fluid
passageway formed in the bit body and extending from the second end
of the cavity to a position spaced from a lower portion of the bit
body; and at least two additional fluid passageways formed in the
bit body extending through the lower portion of the bit body and
intersecting the first fluid passageway.
21. The drill bit of claim 20 further comprising: the first fluid
passageway extending along the longitudinal axis of the bit body;
and three additional fluid passageways extending through the lower
portion of the bit body and intersecting the first fluid
passageway.
22. A rotary cone drill bit for forming a borehole comprising: a
bit body having an upper portion adapted for connection to a drill
string for rotation of the drill bits; first, second and third
support arms attached to the exterior of the bit body and extending
therefrom; a respective cutter cone assembly rotatably mounted on
each of the support arms; the bit body having a longitudinal axis
corresponding generally with a projected axis of rotation of the
drill bit; the first support arm and the second support arm spaced
radially a first number of degrees from each other on the exterior
of the bit body; the second support arm and the third support
spaced radially a second number of degrees from each other on the
exterior of the bit body; the third support arm spaced radially
from the first support arm at a third number of degrees; and the
first number of degrees plus the second number of degrees plus the
third number of degrees equal to three hundred sixty degrees.
23. The drill bit of claim 22 further comprising: the first number
of degrees approximately equal to one hundred ten; the second
number of degrees approximately equal to one hundred twenty; and
the third number of degrees approximately equal to one hundred
thirty.
24. A rotary cone drill bit for forming a borehole comprising: a
bit body having an upper portion adapted for connection to a drill
string for rotation of the drill bit; the bit body having a
longitudinal axis corresponding generally with a projected axis of
rotation for the drill bit; a number of support arms attached to
the bit body and extending therefrom; a number of cutter cone
assemblies equal to the number of support arms with each cutter
cone assembly rotatably mounted on one of the support arms; an
enlarged cavity formed within the upper portion of the bit body;
the cavity having a first end defined in part by an opening for
communicating fluids between the drill string and the cavity; the
cavity having a second end disposed within the bit body; the second
end of the cavity having a generally parabolic configuration; a
number of fluid passageways formed in the bit body extending
between the second end of the cavity and a lower portion of the bit
body; and at least one of the fluid passageways having a generally
curved configuration relative to the longitudinal axis.
25. The drill bit of claim 24 further comprising a nozzle disposed
in each of the fluid passageways adjacent to the lower portion of
the bit body.
Description
RELATED APPLICATION
[0001] This application claims the benefit of U.S. provisional
application Ser. No. 60/061,808 filed Oct. 14, 1997 entitled Rock
Bit with Improved Nozzle Placement.
[0002] The present application is related to patent application
Ser. No. 08/675,626 filed Jul. 3, 1996 entitled Rotary Cone Drill
Bit with Integral Stabilizers, now U.S. Pat. No. 5,755,297 issued
May 26, 1998.
TECHNICAL FIELD OF THE INVENTION
[0003] The present invention relates generally to rotary drill bits
used in drilling boreholes in the earth, and more particularly to a
drill bit with enhanced hydraulic efficiency during drilling
operations.
BACKGROUND OF THE INVENTION
[0004] Various types of rotary drill bits or rock bits may be used
to form a borehole in the earth. Examples of such rock bits include
roller cone drill bits or rotary cone drill bits used in drilling
oil and gas wells. A typical roller cone drill bit comprises a bit
body with an upper end adapted for connection to a drill string. A
plurality of support arms, typically two or three, depend from a
lower end portion of the bit body with each arm having a spindle
protruding radially inward and downward with respect to a projected
rotational axis of the bit body. An enlarged cavity or passageway
is typically formed in the bit body to receive drilling fluids from
the drill string.
[0005] A cutter cone assembly is generally mounted on each spindle
and supported rotatably on bearings acting between the spindle and
the inside of a spindle receiving cavity or chamber in the cutter
cone. One or more nozzle openings may be formed in the bit body
adjacent to the support arms. A nozzle is typically positioned
within each opening to direct drilling fluid passing downwardly
from the drill string through the bit body toward the bottom of the
borehole being drilled. Drilling fluid is generally provided by the
drill string to perform several functions including washing away
material removed from the bottom of the borehole, cleaning the
associated cutter cone assemblies, and carrying the cuttings
radially outward and then upward within the annulus defined between
the exterior of the bit body and the wall of the borehole.
[0006] In order to reduce the distance between the nozzles and the
bottom of the borehole, to increase hydraulic flow, and to minimize
roller cone erosion, extended nozzle tubes may be attached to
existing nozzles. The tubes typically extend from the bit body
toward the bottom of an associated borehole and direct drilling
fluid flow toward the outermost extremity of the drill bit.
Extended nozzle tube installation often requires a time consuming
welding process for attachment with the bit body which generally
increases manufacturing costs.
[0007] Nozzles formed on the exterior of a bit body may close off a
portion of the fluid return area from the bottom of the associated
borehole. Also, previous nozzles frequently direct fluid flow
inwardly toward the center of the borehole which may hinder the
flow of drilling fluid from the bottom of the borehole up the
borehole annulus. Extended nozzle tubes are subject to erosion due
to deflection of the angle of fluid flow that occurs within the
nozzle tube and breakage due to placement of extended nozzle tubes
at the outer extremity of the bit body. Broken and damaged extended
nozzle tubes can also damage cutter cone assemblies or other
components typically associated with a rotary cone drill bit and
drill string.
[0008] With a maximum of only three nozzles available on most
conventional drill bits (one nozzle per roller cone assembly), the
volume and direction of the drilling fluid flow are limited. Any
increase in the volume of drilling fluid supplied through the
associated drill string increases the velocity of drilling fluid
flowing through the nozzles, which may result in excessive erosion
of adjacent roller cone assemblies and/or nozzles.
SUMMARY OF THE INVENTION
[0009] Accordingly, a need has arisen in the art for improved
rotary drill bits. The present invention provides rotary drill bits
with multiple nozzles that substantially eliminate or reduce
problems associated with drilling fluid flow through and around
prior rotary drill bits.
[0010] In accordance with teachings of the present invention, a
drill bit may comprise a one piece or unitary bit body which
provides increased fluid flow near the bottom of an associated
borehole, resulting in enhanced removal of cuttings and other
debris from the bottom of the borehole to the well surface. For
some, applications, a web member may be attached or formed on a
lower portion of the bit body to occupy an area between adjacent
cutter cone assemblies. The web member preferably contains a
plurality of passageways which receive drilling fluid from the
associated drill string, through the bit body, and direct the
drilling fluid to respective nozzles adjacent to the extreme lower
end of the web member.
[0011] In accordance with one embodiment of the present invention a
lower portion of a bit body, or alternatively a web member, may
contain a plurality of nozzles for directing drilling fluid flow to
optimize cleaning of cutting structures associated with the drill
bit and to enhance removal of cuttings and other debris from the
bottom of a borehole. The lower portion of the bit body, or the web
member, may contain a plurality of threaded openings for
installation of respective nozzles with matching threads. Each
threaded opening may have a substantially identical diameter
allowing nozzles to be used interchangeably within the lower
portion of the bit body or the web member. The nozzles may be
provided with substantially identical outside diameters
corresponding with the threaded openings in the bit body and
varying inside diameters or nozzle bores such that fluid flow rates
through the nozzles may vary. Various types of mechanical fasteners
other than threads may be satisfactorily used to install nozzles
within opening in the lower portion of a bit body or a web member
incorporating teachings of the present invention.
[0012] A further aspect of the present invention includes the
ability to vary the volume of the drilling fluid flowing through
each nozzle at different locations relative to the longitudinal
axis of an associated rotary drill bit and associated borehole. For
some applications nozzles at or near the outside diameter of the
lower portion of the bit body may have the largest inside diameter
or nozzle bore and thus the highest fluid flow rate. For other
applications a nozzle at or near the centermost position on the
lower portion of a bit body may have the largest inside diameter or
nozzle bore and thus the highest fluid flow rate. As the radial
distance away from the longitudinal axis of the bit body or
associated borehole increases, the inside diameter of respective
nozzles may decrease to encourage establishing an outward and
upward flow pattern of drilling fluid with entrained cuttings and
other downhole debris. The configuration of nozzles and associated
fluid flow rates may be modified in accordance with teachings of
the present invention to satisfy particular downhole drilling
conditions.
[0013] Important technical advantages of a bit body incorporating
teachings of the present invention include the ability to provide
an increased number of nozzles in the lower portion of a bit body
and to optimize the direction and volume of fluid flow from each
nozzle. Additional nozzles allow selecting the volume of drilling
fluid provided during drilling operations to promote enhanced
removal of cuttings and debris from the bottom of the borehole and
from around the exterior surface of associated cutter cone
assemblies and up the borehole annulus. Additional nozzles may also
allow a decrease in velocity of drilling fluid exiting each nozzle,
while maintaining the same equivalent total fluid flow rate.
Reducing fluid velocity may substantially limit erosion of
associated cutting structure caused by drilling fluid flow. The
location of each fluid flow passageway formed in a bit body and
respective nozzle may be selected to enhance cleaning of the
associated cutting structure such as a rotary cone cutter with
inserts or milled teeth.
[0014] Other technical advantages of the present invention include
providing a convex lower portion of the bit body which increases
the surface area available for placement of nozzles. The convex
lower portion also allows relatively straight fluid passageways to
be provided between a cavity within the bit body and the respective
nozzles which will decrease pressure losses and limit internal
erosion.
[0015] Still further technical advantages of the present invention
include providing a rotary cone drill bit with a web member
protruding from a lower portion of a bit body, occupying void
spaces between respective support arms and cutter cone assemblies.
The web member allows fluid passageways and nozzles to be located
closer to the lower extremity of the cutter cone assemblies
adjacent to the bottom of the associated borehole. By decreasing
the distance between the bottom of the borehole and the nozzles,
cutter cone erosion may be substantially reduced or limited. Also,
more drilling fluid can be directed toward the bottom of the
borehole and away from void spaces between the lower portion of the
bit body and the bottom of the borehole to increase hydraulic
efficiency of the drilling fluid to lift cuttings and debris from
the bottom of the borehole through the borehole annulus.
Furthermore, the web member occupies void spaces between each
support arm and cutter cone assembly, where debris and cuttings may
tend to collect and hinder drilling operations.
[0016] One aspect of the present invention includes providing a
rotary cone drill bit with an increased number of fluid nozzles to
provide better cleaning of associated cutter cone assemblies,
enhanced lifting of cuttings and other debris from the bottom of a
borehole and more efficient application of hydraulic energy to the
bottom of the borehole from drilling fluid exiting the nozzles. As
a result of providing additional fluid nozzles and selecting both
the direction and volume of fluid flowing through each nozzle in
accordance with teachings of the present invention, a resulting
drill bit may have an increased penetration rate for an extended
downhole drilling time as compared to rotary cone drill bits
without such additional fluid nozzles.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] For a more complete understanding of the present invention,
and advantages thereof, reference is now made to the following
brief descriptions, taken in conjunction with the accompanying
drawings and detailed description, wherein like reference numerals
represent like parts, in which:
[0018] FIG. 1 is a schematic drawing in elevation and in section
with portions broken away showing a rotary cone drill bit attached
to one end of a drill string disposed in a borehole;
[0019] FIG. 2 is a schematic drawing showing a partially exploded
isometric view of a rotary cone drill bit incorporating teachings
of the present invention;
[0020] FIG. 3 is a schematic drawing in section showing an exploded
view of portions of the bit body and one support arm/cutter cone
assembly of FIG. 2.
[0021] FIG. 4 is an enlarged schematic drawing in section with
portions broken away showing the lower portion of the bit body and
one nozzle of FIG. 3;
[0022] FIG. 5 is a schematic showing an end view of the bit body of
FIG. 3;
[0023] FIG. 6 is a schematic drawing in section taken along line
6-6 of FIG. 3;
[0024] FIG. 7 is a schematic drawing showing an isometric view of a
rotary cone drill bit incorporating an alternative embodiment of
the present invention;
[0025] FIG. 8 is a schematic drawing showing an end view of the
rotary cone drill bit of FIG. 7;
[0026] FIG. 9 is a schematic drawing with portions broken away of
an irregular section of a bit body incorporating a further
embodiment of the present invention;
[0027] FIG. 10 is a schematic drawing with portions broken away of
an irregular section of a bit body incorporating still another
embodiment of the present invention;
[0028] FIG. 11 is a schematic drawing showing portions of a bit
body incorporating a further embodiment of the present invention;
and
[0029] FIG. 12 is a schematic drawing with portions broken away of
an irregular section taken along lines 12-12 of FIG. 11.
DETAILED DESCRIPTION OF THE INVENTION
[0030] Preferred embodiments of the present invention and some of
its advantages are best understood by referring in more detail to
FIGS. 1-12 of the drawings, in which like numerals refer to like
parts.
[0031] For purposes of illustration, the present invention may be
embodied in rotary cone drill bit 20 of the type used in drilling a
borehole in the earth. Rotary cone drill bit 20 may sometimes be
referred to as a "rotary drill bit", "rock bit" or "roller cone
drill bit". Rotary cone drill bit 20 preferably includes threaded
connection or pin 44 for use in attaching drill bit 20 with drill
string 22. Threaded connection 44 and the corresponding threaded
connection (not expressly shown) associated with drill string 22
are designed to allow rotation of drill bit 20 in response to
rotation of drill string 22 at the well surface.
[0032] As shown in FIG. 1, drill bit 20 may be attached to drill
string 22 and disposed in borehole 24. Annulus 26 is formed between
the exterior of drill string 22 and side wall or inside diameter 28
of borehole 24. In addition to rotating drill bit 20, drill string
22 is often used as a conduit for communicating drilling fluids and
other fluids from the well surface to drill bit 20 at the bottom of
borehole 24. Such drilling fluids may be directed to flow from
drill string 22 to various nozzles 60 provided in drill bit 20.
Cuttings formed by drill bit 20 and any other debris at the bottom
of borehole 24 will preferably mix with drilling fluids exiting
from nozzles 60 and return to the well surface via annulus 26.
[0033] For rotary cone drill bit 20 cutting action or drilling
action occurs as cutter cone assemblies 100 are rolled around the
bottom of borehole 24 by rotation of drill string 22. Cutter cone
assemblies 100 cooperate with each other to form side wall 28 of
borehole 24 in response to rotation of drill bit 20. The resulting
inside diameter of borehole 24 defined by wall 28 corresponds
approximately with the combined outside diameter or gauge diameter
of cutter cone assemblies 100. Cutter cone assemblies 100 may
sometimes be referred to as "rotary cone cutters" or "roller cone
cutters." For some applications, drilling fluid exiting from
nozzles 60 may apply hydraulic energy to the bottom borehole 24 to
assist cutter cone assemblies 100 in forming borehole 24.
[0034] As shown in FIGS. 1, 2, and 3 drill bit 20 includes a
cutting structure defined in part by cutter cone assemblies 100 and
protruding inserts 104 which may scrape, gouge or crush against the
sides and bottom of borehole 24 in response to the weight and
rotation applied to drill bit 20 from drill string 22. The position
of inserts 104 for each cutter cone assembly 100 may be varied to
provide the desired downhole cutting action. Other types of cutter
cone assemblies and cutting structures may be satisfactorily used
with the present invention including, but not limited to, cutter
cone assemblies having milled teeth (not expressly shown) instead
of inserts 104.
[0035] Cuttings and other debris created by drill bit 20 and its
associated cutting structure may be carried from the bottom of
borehole 24 to the well surface by drilling fluid exiting from
nozzles 60. The debris carrying fluid generally flows radially
outward from beneath drill bit 20 and then flows upward toward the
well surface through annulus 26.
[0036] Drill bit 20 preferably comprises a one-piece or unitary bit
body 40 with upper portion 42 having threaded connection or pin 44
adapted to secure drill bit 20 with the lower end of drill string
22. Three support arms 70 are shown attached to and extending
longitudinally from bit body 40 opposite from pin 44. Each support
arm 70 preferably includes spindle 82 connected to and extending
from inside surface 76 of the respective support arm 70. An
important feature of the present invention includes the ability to
selectively position a plurality of nozzles 60 in lower portion 46
of bit body 40 intermediate support arms 70.
[0037] For some applications, two nozzles 60 may be provided for
cutter cone assembly 100 to increase cleaning of the respective
cutting structure. For some applications, drilling fluid flowing
from nozzles 60 may be directed toward void spaces between adjacent
cutter cone assemblies 100. Drilling fluid flowing from one or more
additional nozzles 60 may also be directed toward the bottom of
borehole 24 to assist cutter cone assemblies 100 in forming
borehole 24.
[0038] For some downhole drilling conditions optimum cleaning of
the associated cutting structures may be obtained by directing
fluid flow from nozzle 60 to locations at the approximate midpoint
between adjacent cutter cone assemblies 100. For other downhole
drilling conditions, optimum cleaning of the associated cutting
structures may be obtained by directing fluid flow from nozzle 60
to locations which are closer to the leading edge of the associated
cutting structures. Nozzles 60 will generally be positioned to
avoid direct impact or impingement of cutter cone assemblies 100
with fluid flowing from respective nozzles 60.
[0039] As shown in FIGS. 2 and 3, bit body 40 includes lower
portion 46 having a generally convex exterior surface 48 formed
thereon, and middle portion 52 disposed between upper portion 42
and lower portion 46. Longitudinal axis or central axis 50 extends
through bit body 40 and corresponds generally with the projected
axis of rotation for drill bit 20. Middle portion 52 preferably has
a generally cylindrical configuration with pockets 54 formed in the
exterior thereof and spaced radially from each other. The number of
pockets 54 is selected to correspond with the number of support
arms 70 which will be attached thereto. The spacing between pockets
54 in the exterior of middle portion 52 is selected to correspond
with desired spacing between support arms 70 and their associated
cutter cone assemblies 100. The spacing between pockets 54 also
allows positioning nozzles 60 to optimize the flow of drilling
fluid at the bottom of borehole 24 to increase removal of cuttings
and penetration rate of drill bit 20.
[0040] For some applications, bit body 40 may be fabricated or
machined from a generally cylindrical, solid piece of raw material
or bar stock (not shown) having the desired metallurgical
characteristics for the resulting drill bit 20. Bit body 40 may
also be formed from an appropriately sized forging. For still other
applications, bit body 40 may be formed using precision casting
techniques. the present invention allows using machinery, forging
and/or casting techniques as appropriate to form bit body 40.
[0041] Each support arm 70 has a longitudinal axis 72 extending
therethrough. Support arms 70 are preferably mounted in their
respective pockets 54 with their respective longitudinal axis 72
aligned generally parallel with each other and with longitudinal
axis 50 of the associated bit body 40.
[0042] FIG. 3 is an exploded drawing which shows the relationship
between bit body 40, one of the support arms 70 and its associated
cutter cone assembly 100. Each cutter cone assembly 100 is
preferably constructed and attached to its associated spindle 82 in
a substantially identical manner. Each support arm 70 is preferably
constructed and mounted in its associated pocket 54 in
substantially the same manner. Therefore, only one support arm 70
and cutter cone assembly 100 will be described in detail since the
same description applies generally to the other two support arms 70
and their associated cutter cone assemblies 100.
[0043] Support arm 70 may have a generally rectangular
configuration with respect to longitudinal axis 72. Support arm 70
may have various cross-sections taken normal to longitudinal axis
72 depending upon the configuration of the associated pocket 54 and
other features which may be incorporated into support arm 70 in
accordance with the teachings of the present invention. Support arm
70 includes top surface 74, inside surface 76, bottom edge 78 and
exterior surface 80. Support arm 70 also includes sides 84 and 86
which preferably extend substantially parallel with longitudinal
axis 72.
[0044] A bit body having fluid passageways and nozzles
incorporating teachings of the present invention may be
satisfactorily used with support arms and cutter cone assemblies
having a wide variety of designs and configurations. The present
invention is not limited to use with support arms 70, cutter cone
assemblies 100 or the type of cutting structures shown in FIGS. 1,
2, 3, 7 and 8.
[0045] The various dimensions of each support arm 70 are selected
to be compatible with the associated pocket 54. As shown in FIGS. 2
and 3, a portion of each support arm 70 including upper end or top
surface 74 and adjacent portions of inside surface 76 along with
sides 84 and 86 extending therefrom, are sized to fit within the
associated pocket 54.
[0046] Inside surface 76 may be modified as desired for various
downhole applications. The configuration of inside surface 76 may
be varied substantially between top surface 74 and bottom edge 78.
Also, the configuration of inside surface 76 with respect to sides
84 and 86 may be varied depending upon the configuration of the
associated pockets. Inside surface 76 and exterior surface 80 are
contiguous at bottom edge 78 of support arm 70. The portion of
exterior surface 80 formed adjacent to bottom edge 78 is often
referred to as shirttail surface 88.
[0047] For one embodiment of the present invention, first opening
75 and second opening 77 are formed in inside surface 76 of each
support arm 70. First post 53 and second post 55 may be formed on
back wall 64 of each pocket 54. Post 53 and 55 extend radially from
each back wall 64 to cooperate respectively with first opening 75
and second opening 77 to position each support arm 70 within its
associated pocket 54. For some applications,. first opening 75
preferably comprises a longitudinal slot extending from top surface
74 and size to receive first post 53 therein. Second opening 77
preferably has a generally circular configuration to receive second
post 55 therein. Posts 53 and 55 and openings 75 and 77 may be used
to position each support arm 70 within the associated pocket 54
prior to welding. For some applications posts 53 and 55 may be
dowels inserted into appropriate sized openings in each back wall
64.
[0048] Spindle 82 is preferably angled downwardly and inwardly with
respect to both longitudinal axis 72 of support arm 70 and the
projected axis of rotation of drill bit 20. This orientation of
spindle 82 results in the exterior of cutter cone assembly 100
engaging the side and bottom of borehole 24 during drilling
operations.
[0049] For the embodiment shown in FIGS. 1, 2 and 3, lug 170 is
preferably disposed on the exterior of each support arm 70. Lugs
170 are preferably formed as an integral part of respective support
arms 70 and covered with hardfacing layer 172. For some
applications, lugs 170 may be attached as a separate component to
the exterior of each support arm 70. Further information concerning
lugs 170 may be found in U.S. Pat. No. 5,755,297 issued May 26,
1998.
[0050] As shown in FIGS. 1, 2 and 3, each cutter cone assembly 100
includes base portion 108 with a conically shaped shell or tip 106
extending therefrom. For some applications, base portion 108
includes frustroconically shaped outer surface 110 which is
preferably angled in a direction opposite from the angle of shell
106. Base 108 also includes backface 112 which may be disposed
adjacent to portions of inside surface 76 of the associated support
arm 70. Base 108 preferably includes opening 120 with chamber 114
extending therefrom. Chamber 114 extends through base 108 and into
tip 106. The dimensions of opening 120 and chamber 114 are selected
to allow mounting each cutter cone assembly 100 on its associated
spindle 82. One or more bearing assemblies 122 may be mounted on
spindle 82 and disposed between a bearing wall within chamber 114
and annular bearing surface 81 on spindle 82. A conventional ball
retaining system 124 may be used to secure cutter cone assembly 100
to spindle 82.
[0051] Cutter cone assembly 100 may be manufactured of any
hardenable steel or other high strength engineering alloy which has
adequate strength, toughness, and wear resistance to withstand the
rigors of downhole drilling. Protection of bearing assembly 122 and
any other bearings within chamber 114, which allow rotation of
cutter cone assembly 100, can lengthen the useful service life of
drill bit 20. Once drilling debris is allowed to infiltrate between
the bearing surfaces of cutter cone assembly 100 and spindle 82,
failure of drill bit 20 will follow shortly.
[0052] The size of drill bit 20 is generally determined by the
combined outside diameter or gauge diameter associated with the
three cutter cone assemblies 100. The position of each cutter cone
assembly 100 and their combined gauge diameter relative to the
projected axis of rotation of drill bit 20 is a function of the
dimensions of pockets 54 and their associated support arms 70 with
cutter cone assemblies 100 mounted respectively thereon.
[0053] As best shown in FIGS. 2, 3, 5 and 6, each pocket 54
includes back wall 64 and a pair of side walls 66 and 68. The
dimensions of back wall 64 and side walls 66 and 68 are selected to
be compatible with the adjacent inside surface 76 and sides 84 and
86 of the associated support arm 70. For one application, side
walls 66 and 68 are formed at an angle of forty-five degrees
(45+20) relative to back wall 64. Also, each pocket 54 preferably
includes upper surface 65 formed as an integral part thereof to
engage top surface 74 of the associated support arm 70.
[0054] Additional information concerning the design and
construction of drill bit 20 such as shown in FIGS. 1, 2 and 3 may
be found in U.S. Pat. U.S. 5,641,029 entitled "Rotary Cone Drill
Bit Modular Arm." As previously noted, lower portion 46 of bit body
40 preferably includes convex surface 48. However, various
teachings of the present invention may be satisfactorily
incorporated into a bit body wherein the lower portion comprises a
flat surface or a concave surface.
[0055] As shown in FIG. 3, enlarged cavity 56 may be formed within
upper portion 42 of bit body 40. Opening 58 is provided in upper
portion 42 for communicating fluids between drill string 22 and
cavity 56. Cavity 56 preferably has a generally uniform inside
diameter extending from opening 58 to a position intermediate bit
body 40. Second end of cavity 56 opposite from opening 58 has a
generally spherical configuration. For some applications, cavity 56
may be formed concentric with longitudinal axis 50 of bit body
40.
[0056] One or more fluid passageways 62 may be formed in bit body
40 extending between cavity 56 and convex surface 48 formed on
lower portion 46 of bit body 40. Opening 61 may be provided in each
fluid passageway 62 adjacent to convex surface 48. A plurality of
threaded recesses 63 are preferably provided within each opening 61
to allow installing various types of nozzles or nozzle inserts 60
within each fluid passageway 62. O-ring seal 67 may be provided
with each nozzle insert 60 to prevent undesired fluid flow from the
associated fluid passageway 62 through the respective nozzle bore
130. See FIG. 4.
[0057] Various techniques are commercially available for
satisfactorily installing each nozzle 60 within its associated
opening 61. For some applications, nozzles 60 may be formed from
tungsten carbide or other suitable materials to resist erosion from
fluids flowing therethrough. Also, one or more access ports (not
shown) may be provided in bit body 40 adjacent to openings 61 to
allow lock screws or pins and/or plug welds (not expressly shown)
to secure nozzles 60 within respective openings 61.
[0058] Nozzles 60 are preferably disposed in each fluid passageway
62 to regulate fluid flow from cavity 56 through the respective
fluid passageway 62 and the associated nozzle 60 to the exterior of
bit body 40. Each nozzle 60 preferably include at least one outlet
orifice 59. For some applications nozzles with multiple outlet
orifices may be satisfactorily used with the present invention.
[0059] The length and diameter of each fluid passageway 62 may be
selected for some applications to provide laminar flow between
cavity 56 and the respective nozzle 60. The present invention
allows forming fluid passageways 62 with a total fluid flow area
larger than previously possible with conventional rotary cone drill
bits. The relatively straight, large inside diameter of each
passageway 62 will minimize erosion or washout of respective
nozzles 60.
[0060] For the embodiment shown in FIGS. 3 and 4, the length of
nozzles 60 and associated threaded recesses 63 is selected such
that the respective outlet orifices 59 are disposed adjacent to
surface 48 of lower portion 46 of bit body 40. For some
applications, the length of nozzles 60 may be increased and/or the
length of nozzle bores 130 decreased such that the resulting
nozzles 60 extend from lower portion 46 of bit body 40.
[0061] For purposes of illustration, nozzles 60 shown in FIGS. 3
and 4 have been designated 60a, 60b and 60c. For some applications,
nozzles 60a, 60b and 60c may have essentially the same dimensions
and configurations which will result in approximately the same
fluid flow rate through each nozzle 60. For other applications,
nozzles 60c will preferably have a larger inside diameter or outlet
orifice 59 as compared to nozzle 60a. For this same application,
60a will preferably have a larger inside diameter or outlet orifice
59 as compared to nozzles 60b.
[0062] For still other applications, nozzle 60a may have a larger
outlet orifice 59 as compared with nozzles 60b and 60c. Also,
nozzles 60b may have a larger outlet orifice 59 than nozzles 60c.
Decreasing the size of the respective outlet orifices 59 for
nozzles 60a, 60b and 60c will generally cause a corresponding
decrease in the flow rate of drilling fluid exiting from each
nozzle 60. Having the largest fluid flow rate from nozzle 60a at
the center of lower portion 48 may enhance the flow of drilling
fluid from the bottom of borehole 24 radially outward and upward
through annulus 26. For still other applications, nozzle 60a may
include more than one outlet orifice (not expressly shown).
[0063] For some downhole drilling conditions nozzle 60a may be
removed and a plug installed therein or fluid passageway 62
extending along longitudinal axis 50 may be omitted. For example,
if the drilling fluid which will be used with the resulting rotary
cone drill bit contains abrasive materials, it may be preferable to
eliminate center nozzle 60a and possibly even nozzles 60b to
minimize erosion and wear of the associated cutting structures.
Center nozzle 60a may also be omitted and/or the associated fluid
passageway 62 closed when downhole drilling conditions require
relatively high fluid flow rates through bit body 40. Eliminating
nozzle 60a and/or substantially reducing the fluid flow rate
through nozzle 60a may reduce erosion and wear of the associated
cutter cone assemblies 100.
[0064] For some applications, nozzles 60b may be positioned to
direct drilling fluid flow to a desired location relative to
respective cutter cone assembly 100. Nozzles 60c may be positioned
to direct drilling fluid flow toward the bottom of borehole 24. For
some applications, fluid flow exiting from nozzles 60c will
preferably impact the bottom of borehole 24 at a radial distance
approximately one inch less than the radius of borehole 24. As a
result, drilling fluid exiting from nozzles 60c will apply
hydraulic energy to the bottom of borehole 24 in a manner that will
encourage drilling fluid and cuttings to flow readily upward
through annulus 26. Also, applying hydraulic energy to the bottom
of borehole 24 at a location approximately one inch radially inward
from wall 28 may enhance the penetration rate of the associated
cutter cone assemblies 100. The present invention allows varying
the location at which fluid flow exiting from nozzles 60 will
impact the bottom of borehole 24 depending upon the diameter of the
respective borehole and other downhole conditions.
[0065] For still other applications, the position of nozzles 60b
and 60c may be varied to optimize the angle of drilling fluid
exiting from the respective nozzles 60b and 60c to enhance cleaning
of the cutting structure on the associated cutter cone assembly
100.
[0066] For the embodiment shown in FIG. 4, nozzle bore 130 formed
in nozzle 60c is generally aligned concentric with the associated
fluid passageway 62. For some applications, a nozzle bore (not
expressly shown) may be formed in one or more nozzles 60 extending
at an angle from the associated fluid passageway 62. For drill bits
having a nominal diameter larger than approximately twelve to
fourteen inches in ten or more fluid passageways 62 and associated
nozzles 60 may be formed within the associated bit body 40. As the
size of rotary cone drill bit 20 increases additional fluid
passageway 62 and associated nozzles 60 may be added to provide the
desired drilling fluid flow rate to optimize downhole performance
of the associated drill bit 20.
[0067] An important feature of the present invention includes the
ability to vary the number and position of fluid passageways 62 and
associated nozzles 60 within bit body 40 without affecting the
location of pockets 54 and the associated support arms 70.
[0068] FIGS. 5 and 6 illustrate various examples of different
locations for fluid passageways 62 and their associated nozzles 60
within the respective bit body in accordance with the teachings of
the present invention. FIG. 5 shows lower portion 46 with three
pockets 54 spaced radially with respect to each other around the.
perimeter of bit body 40. For the specific example shown in FIG. 5,
seven (7) fluid passageways 62 and associated openings 61 are
shown. One fluid passageway 62 extends generally along longitudinal
axis 50. The other six fluid passageways 62 and associated openings
61 are spaced radially approximately one hundred twenty degrees
(120.degree.) from each other. In a similar manner, each support
pocket 54 may be spaced radially approximately one hundred twenty
degrees (120.degree.) from an adjacent pocket 54.
[0069] For some applications the radial spacing between adjacent
pockets 54 and associated support arms 70 may be other than one
hundred and twenty degrees. An example of such alternative radial
spacing (not expressly shown) would be one hundred and ten degrees
(110.degree.) between respective longitudinal centerlines of a
first support arm and a second support arm, one hundred and twenty
degrees (120.degree.) between respective longitudinal centerlines
of the second support arm and a third support arm and one hundred
and thirty degrees (130.degree.) between respective longitudinal
centerlines of the third support arm and the second support arm.
Teachings of the present invention may also be used to provide
multiple nozzles in a rotary cone drill bit having two support arms
and cutter cone assemblies (not expressly shown) or four support
arms and cutter cone assemblies (not expressly shown).
[0070] Another embodiment of the present invention is represented
by rotary cone drill bit 138 and bit body 140 shown in FIGS. 7 and
8. Bit body 140 is essentially the same as previously described bit
body 40 with the exception of web member 148. Web member 148
preferably extends from lower portion 46 of bit body 140 toward
associated cutter cone assemblies 200. Cutter cone assemblies 200
may be similar to cutter cone assemblies 100 but proportionally
smaller to provide void spaces for web member 148 to occupy between
adjacent cutter cone assemblies 200.
[0071] For the embodiment of the present invention as shown in
FIGS. 7 and 8, web member 148 includes three legs or blades
designated 149, 150, and 151. Legs 149, 150 and 151 may extend at
an angle of approximately one hundred twenty degrees (120.degree.)
relative to each other and relative to the longitudinal center line
extending through bit body 140. Each cutter cone assembly 200 is
preferably disposed between respective legs 149, 150 and 151. The
configuration of web member 148 may be varied in accordance with
teachings of the present invention to correspond with the number,
dimension and location of the associated cutter cone assemblies.
For example blades 149, 150 and 151 may extend at angles other than
one hundred twenty degrees (120.degree.).
[0072] Web member 148 preferably includes a plurality of fluid
passageways (not expressly shown) which communicate with respective
fluid passageways 62 extending through bit body 140. A plurality of
openings 161 are preferably formed in the extreme end of web member
148 opposite from convex surface 48 of bit body 140. A plurality of
nozzles 60 may be disposed within respective openings 161 as
previously described with respect to openings 61 of bit body
40.
[0073] Providing web member 148 in accordance with teachings with
the present invention may improve hydraulic efficiency of rotary
cone drill bit 138 by placing a plurality of nozzles 60 as close as
possible to the bottom of the associated borehole. For some
applications, at least one nozzle 60 will be placed near the
longitudinal axis associated with drill bit 138 with other nozzles
60 positioned radially outward on blades 149, 150, and 151 of web
member 148. For the embodiment shown in FIGS. 7 and 8, web member
148 includes two nozzle 60 disposed in each blade 149, 150 and 151
and one nozzle 60 disposed at the intersection of blades 149, 150,
and 151.
[0074] For some applications, the fluid passageways extending
through web member 148 to the associated nozzles 60 will be
essentially straight with no turns or sharp bends to prevent loss
of drilling fluid pressure and eliminate the possibility of
internal erosion. For some applications, web member 148 is
preferably formed as an integral part of bit body 140. For other
applications, web member 148 may be attached to the bit body 140
using conventional welding techniques.
[0075] Web member 148 and nozzles 60 cooperate with each other to
sweep cuttings and other debris from the bottom of the borehole to
an associated annulus area to flow upwardly to the well surface.
For some applications, nozzles 60 may be placed approximately one
or two inches from the bottom of the associated borehole. For other
applications, nozzles 60 may be installed even closer to the bottom
of the associated borehole.
[0076] For some applications, the size of cutter cones assemblies
200 may be reduced as compared to cutter cone assemblies associated
with similar sized drill bits. Cutter cone assemblies 200 and
blades 149, 150 and 151 associated with web member 148 cooperate
with each other to minimize erosion thereof. Nozzles 60 are
positioned such that maximum hydraulic energy exiting from the
outlet orifice of each nozzle 60 can be used throughout the
drilling operation to lift cuttings and debris from the bottom of
the associated borehole and to sweep the cuttings in the direction
of the associated annulus. The use of web member 148 and nozzles 60
eliminates generally downward flow streams of drilling fluid that
may interfere with upward flow of cuttings and other borehole
debris. Nozzles 60 can be located radially from the longitudinal
axis of rotary cone drill bit 140 in various ways. Either in groups
of three or each nozzle 60 may have its own unique radial and
angular position.
[0077] Bit bodies 240a, 240b and 240c incorporating alternative
embodiments of the present invention are shown in FIGS. 9, 10, 11
and 12. Except for some of the differences which will be discussed
later in more detail, bit bodies 240a, 240b and 240c are similar to
bit body 40 and bit body 140. Bit bodies 240a, 240b and 240c may be
used to manufacture a wide variety of rotary cone drill bits
including drill bits 20 and 120.
[0078] FIGS. 9, 10 and 12 are schematic drawings showing a cross
section of the respective bit body 240a, 240b and 240c. For the
embodiments of the present invention as shown in FIGS. 9, 10 and
12, each cross section is taken at an angle of approximately 120
degrees relative to the respective longitudinal axis 50. See for
example FIG. 11.
[0079] Bit bodies 240a, 240b and 240c may be generally described as
one piece or unitary bit bodies. Upper portion 42 of each bit body
240a, 240b and 240c includes threaded connection or pin 44 which
may be used to secure the resulting drill bit with the lower end of
a drill string. Lower portion 46 of each bit body 240a, 240b and
240c preferably include generally convex exterior surface 48.
[0080] Middle portion 52 of each bit body 240a, 240b and 240c has a
generally cylindrical configuration disposed between upper portion
42 and lower portion 46. A plurality of pockets as previously
discussed with respect to drill bits 20 and 120 are preferably
formed in the exterior of each bit body 240a, 240b and 240c. For
purposes of illustrating various features of the present invention,
the pockets are not shown in FIGS. 9, 10, 11 and 12. Longitudinal
axis or central axis 50 extends through each bit body 240a, 240b
and 240c. Longitudinal axis 50 corresponds generally with the
projected axis of rotation for the resulting drill bit.
[0081] For some applications, bit bodies 240a, 240b and 240c may be
fabricated or machined from a generally cylindrical, solid piece of
raw material or bar stock (not expressly shown) having desired
metallurgical characteristics for the resulting rotary cone drill
bit. For other applications, bit bodies 240a, 240b and 240c may be
initially formed using conventional forging techniques appropriate
for fabrication of equipment used to drill oil and gas wells. The
resulting forgings may then be further machined to have the desired
configuration and dimensions for the respective bit bodies 240a,
240b and 240c. For still other applications bit bodies 240a, 240b
and 240c may formed using precision casting techniques (sometimes
referred to as "investment castings") in combination with various
machining steps as desired. As discussed later in more detail,
precision casting of bit body 240b may be particularly
beneficial.
[0082] Bit body 240a as shown in FIG. 9 includes enlarged cavity
256a formed within upper portion 42. Opening 258 is provided in
upper portion 42 for communicating drilling fluids between an
attached drill string and cavity 256a. Cavity 256a preferably has a
generally uniform inside diameter portion 260 extending from
opening 258 to a position intermediate bit body 240a. For some
applications, cavity 256a may be formed concentric with
longitudinal axis 50. Cavity 256a includes a first end defined in
part by opening 258 and a second end defined in part by surface
261.
[0083] For the embodiment of the present invention as shown in
FIGS. 9 and 10, surface 261 has a generally parabolic configuration
extending from inside diameter portion 260 along longitudinal axis
50. The resulting cross-section of enlarged cavities 256a and 256b
provides additional surface area for forming respective fluid
passageways 262a and 262b extending therefrom.
[0084] A plurality of fluid passageways 262a may be formed in bit
body 240a extending between cavity 256a and convex surface 48 of
lower portion 46. As previously discussed for drill bits 20 and
120, appropriate sized openings may be formed in each fluid
passageway 262a adjacent to convex surface 48 to allow installing
various types of nozzles or nozzle inserts within each fluid
passageway 262a.
[0085] As a result of forming generally parabolic surface 261 on
the second end of cavity 256a disposed within bit body 240a,
additional spacing is provided between adjacent fluid passageways
262a at their intersection with surface 261. For purposes of
illustration, this increased spacing is designated 264a in FIG. 9.
Generally parabolic surface 261 allows forming an increased number
of fluid passageways 262a within bit body 240a with the optimum
orientation and dimensions to optimize fluid flow from cavity 256a
through respective fluid passageways 262a to the bottom of an
associated borehole. Alternative, generally parabolic surface 261
may allow forming the same number of fluid passageways 262a with
larger inside diameters.
[0086] As shown in FIG. 10, bit body 240b includes enlarged cavity
256b formed in upper portion 42. Opening 258 is provided in upper
portion 42 for communicating fluids between a drill string and
enlarged cavity 256b. For purposes of illustrating various features
of the present invention, cavity 256b includes inside diameter 260
and generally parabolic surface 261 as previously described with
respect to cavity 256a.
[0087] A plurality of fluid passageways 262b are preferably formed
in bit body 240b extending between cavity 256b and convex surface
48 of lower portion 46. As best shown in FIG. 10, fluid passageways
262b preferably include an arc or radius of curvature relative to
longitudinal axis 50. As a result, each fluid flow passageway 262b
may be located to intersect convex surface 48 at a generally
perpendicular angle.
[0088] Fluid passageways 262b are preferably formed within bit body
240b using precision casting techniques. Combining fluid
passageways 262b having a generally smooth, gradual curve or bend
with generally parabolic surface 261 provides even more flexibility
in the number and location of fluid passageways 262b which may be
formed within bit body 240b to optimize fluid flow therethrough.
End 261 of cavities 256a and 256b may have various elliptical
and/or parabolic configurations as desired to optimize the location
of the associated fluid passageways 262a and 262b extending
respectively therefrom. For some applications, fluid passageway
263a and 263b which extend along longitudinal axis 50 may be
eliminated if desired.
[0089] For the embodiments shown in FIGS. 9 and 10, fluid
passageways 262a, 263a, 262b and 263b are shown with approximately
the same diameter. Depending upon the anticipated downhole drilling
conditions, the fluid passageways located closest to the outside
diameter of bit bodies 240a and 240b may have a larger inside
diameter or fluid flow area and fluid passageways located closer to
respective longitudinal axis 50 may have a smaller inside diameter
or fluid flow area. This configuration will result in increasing
the fluid flow rate towards the exterior of the associated drill
bit.
[0090] For other applications, the fluid passageways located
closest to longitudinal axis 50 may have the largest inside
diameter or fluid flow area while fluid passageways located closest
to the exterior or respective bit bodies 240a and 240b may have a
smaller inside diameter or fluid flow area. As a result increased
fluid flow may exit from the resulting drill bit along the axis of
rotation. By forming a bit body in accordance with teachings of the
present invention, the required fluid flow rate and fluid flow
pattern may be provided at the bottom of a borehole to optimize
performance of the associated drill bit.
[0091] Bit body 240c incorporating a further embodiment of the
present invention is shown in FIGS. 11 and 12. Enlarged cavity 256c
may be formed within upper portion 42 of bit body 240c. The cavity
256c includes a first end defined in part by opening 258 and second
end 261c. For the embodiment shown in FIGS. 11 and 12 end 261c is
relatively flat and has a diameter corresponding approximately with
inside diameter 260.
[0092] For the embodiment shown in FIGS. 11 and 12, bit body 240c
preferably includes three fluid flow passageways 262c which extend
from cavity 256c to exterior surface 48 proximate the outside
diameter of lower portion 46. Fluid passageways 262c extend at an
angle relative to longitudinal axis 50 and relative to each
other.
[0093] Bit body 240c also includes fluid passageway 263c which
extends along longitudinal axis 50 from end 261c to a location
intermediate middle portion 52 of bit body 240c. Three additional
fluid flow passageways designated 266, 267 and 268 extend formed
from convex surface 48 to intersect fluid flow passageway 263c. As
a result there are only four openings within end 261c of fluid
cavity 256c. However, a total of six openings 61 are available for
adjacent to convex surface for installing nozzles 60.
[0094] For some applications, the inside diameter or flow area of
fluid passageway 263c may be larger than the inside diameter or
fluid flow area of fluid passageways 262c. The increased diameter
may be desirable to provide desired fluid flow to passageways 266,
267 and 268. As a result of forming additional fluid passageways
266, 267 and 268 extending from fluid passageway 263c, the spacing
between adjacent fluid passageways 262c and 263c within end 261c
may be increased.
[0095] For some applications, additional fluid passageways (not
expressly shown) may be formed from convex surface 38 to intersect
with fluid passageway 262c. Generally, parabolic surface 261 and/or
forming one or more additional fluid passageways as shown in FIGS.
11 and 12 allows increasing the spacing between the intersection of
fluid passageways and the respective enlarged cavity. Increasing
the spacing improves manufacturability of the associated bit body
and minimizing possible erosion within the second end of the
respective cavity.
[0096] Although the present invention has been described by several
embodiments, various changes and modifications may be suggested to
one skilled in the art. It is intended that the present invention
encompasses such changes and modifications as fall within the scope
of the present appended claims.
* * * * *