U.S. patent application number 14/675962 was filed with the patent office on 2016-10-06 for component of bottom hole assembly having upwardly-directed fluid cleaning flow and methods of using same.
This patent application is currently assigned to NOV Downhole Eurasia Limited. The applicant listed for this patent is NOV Downhole Eurasia Limited. Invention is credited to Ralph Dale Morrison, Pabel Antinio Gaduan Segura, Robert Peter Douglas Tipples, Stephen Williams.
Application Number | 20160290067 14/675962 |
Document ID | / |
Family ID | 57015718 |
Filed Date | 2016-10-06 |
United States Patent
Application |
20160290067 |
Kind Code |
A1 |
Tipples; Robert Peter Douglas ;
et al. |
October 6, 2016 |
COMPONENT OF BOTTOM HOLE ASSEMBLY HAVING UPWARDLY-DIRECTED FLUID
CLEANING FLOW AND METHODS OF USING SAME
Abstract
A stabilizer, drill bit, or other component of a bottom hole
assembly for use in drilling a borehole includes an elongate and
generally cylindrical body, a flow bore in the body, a plurality of
outwardly-extending blades, with a valley disposed between adjacent
blades. A ring segment that is spaced from the body and extends
across at least one valley to define a flow passage through which
cuttings-laden drilling mud is conveyed with an upwardly-direct
trajectory. The body includes a hole or passageway for conveying
drilling mud from the flow bore to between the blades. The
passageway terminates in an exit directed toward the flow passage
so as to provide fresh drilling mud with a trajectory such that the
fluid passes through the flow passage.
Inventors: |
Tipples; Robert Peter Douglas;
(Cheltenham, GB) ; Williams; Stephen; (Stroud,
GB) ; Morrison; Ralph Dale; (Magnolia, TX) ;
Segura; Pabel Antinio Gaduan; (Muscat, OM) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NOV Downhole Eurasia Limited |
Gloucestershire |
|
GB |
|
|
Assignee: |
NOV Downhole Eurasia
Limited
Gloucestershire
GB
|
Family ID: |
57015718 |
Appl. No.: |
14/675962 |
Filed: |
April 1, 2015 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
E21B 17/1078
20130101 |
International
Class: |
E21B 17/10 20060101
E21B017/10 |
Claims
1. A stabilizer for use in drilling a borehole, comprising: a
generally cylindrical body having an inner wall defining a flow
bore in said body; a plurality of blades extending outwardly from
said body; a valley disposed between a pair of adjacent blades; a
ring segment spaced from said body and extending over said valley;
a flow passage between said ring segment and said body; a hole in
said body configured to convey drilling fluid from said flow bore
to between said pair of blades.
2. The stabilizer of claim 1 wherein said hole comprises an
entrance in said inner wall and an exit in said valley, said hole
extending between said flow bore and said flow passage.
3. The stabilizer of claim 1 wherein said hole is configured to
convey drilling fluid with a trajectory through at least a portion
of said flow passage
4. The stabilizer of claim 2 wherein the hole extends at an obtuse
angle to the direction of flow of drilling fluid through the flow
bore.
5. The stabilizer of claim 1 wherein said exit of said hole is
located beneath said ring segment.
6. The stabilizer of claim 1 further comprising a sleeve disposed
in said hole, said sleeve lining at least a part of said hole.
7. The stabilizer of claim 3 wherein said hole comprises a nozzle
having a nozzle bore through which drilling fluid is conveyed.
8. The stabilizer of claim 7 wherein said nozzle bore includes a
fluid entry end having a first flow area and a fluid exit end
having a second flow area smaller than said first flow area.
9. The stabilizer of claim 1, wherein said body has a wall
thickness that varies along the longitudinal length of said body
and comprises a transition zone between a thick wall portion in
said valley and a thin wall portion under said ring segment,
wherein said hole is positioned in said transition zone.
10. The stabilizer of claim 1 wherein only one ring segment spans
between adjacent blades.
11. The stabilizer of claim 1 wherein a ring segment is arranged
between every adjacent blade forming a complete ring about said
stabilizer.
12. A drill bit for use in drilling a borehole, the drill bit
comprising: a generally cylindrical bit body having an inner wall
defining a flow bore for conveying drilling mud; a pair of blades
extending outwardly from said bit body; a valley disposed between
said pair of blades; a ring segment spaced from said bit body and
extending over said valley; a flow passage between said bit body
and said ring segment; a hole in said body configured to convey
drilling fluid from said flow bore to said flow passage.
13. The drill bit of claim 12 wherein said hole comprises an exit
in said flow passage.
14. The drill bit of claim 12 wherein said wherein said exit is
located beneath said ring segment.
15. The drill bit of claim 12 wherein said hole extends at an
obtuse angle to the direction of flow of drilling fluid through
said flow bore.
16. The drill bit of claim 15 wherein said obtuse angle is between
140 degrees and 170 degrees.
17. The drill bit of claim 12 wherein said exit is configured to
convey drilling fluid with a trajectory passing through said flow
passage.
18. The drill bit of claim 17 wherein said hole comprises a nozzle
having a nozzle bore through which drilling fluid is conveyed.
19. The drill bit of claim 12 wherein said bit body has a wall
thickness that varies along the longitudinal length of said body
and comprises a transition zone between a thick wall portion in
said valley and a thin wall portion under said ring segment,
wherein said hole is disposed in said transition zone.
20. Apparatus for use in drilling a borehole in earthen formations,
comprising: an elongate body having an outer surface and an
internal flow bore configured to convey drilling fluid
longitudinally through said body; at least a first pair of blades
connected to said body and extending radially beyond said outer
surface; a valley between said pair of blades; a ring segment
spaced apart from said outer surface and connected to each of said
first pair of blades, said ring segment bridging said valley; a
flow passage between said ring segment and said outer surface of
said body; a hole extending from said flow bore to said outer
surface and configured to direct a portion that is less than all of
the drilling fluid from said flow bore though an exit in the outer
surface, and to impart a trajectory to said portion of drilling
fluid such that it passes through said flow passage.
21. The apparatus of claim 20 wherein said body has a wall
thickness that varies along the longitudinal length of said body
and comprises a transition zone between a thick wall portion in
said valley and a thin wall portion under said ring segment,
wherein said hole is disposed in said transition zone.
22. The apparatus of claim 20 wherein said hole extends at an
obtuse angle to the direction of flow of drilling fluid through
said flow bore.
23. The apparatus of claim 22 wherein said exit is positioned
beneath said ring segment.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] None
BACKGROUND
[0002] The field of endeavour relates to a stabilizer and a drill
bit for use in a drill string. The stabilizer and drill bit
preferably, but not exclusively, forms part of a bottom hole
assembly of the drill string.
[0003] In the drilling of a borehole in the construction of an oil
or gas well, a drill bit is arranged at a lower end of a drill
string, which is rotated to bore the borehole through a formation.
A drilling fluid, referred to herein as "drilling mud," is pumped
through the drill string to the drill bit to lubricate the drill
bit and returns carrying drill cuttings in an annulus between an
outer wall of the drill string and the borehole. As the drill bit
progresses through the formation, stands of drill pipe are added to
the drill string. Stands of drill pipe typically comprise two,
three or four joints of drill pipe threadedly connected together in
a mousehole in a drilling rig floor using an iron roughneck. The
stand is then set back in a fingerboard pipe rack. A joint of drill
pipe is typically 31 ft 6 inches long (9.65 m). Each joint of drill
pipe has a hollow cylindrical body with a lower threaded pin end
and an upper threaded box end. As the drill bit progresses in the
borehole, the drill string moves downwardly. When an upper end of
the drill string nears the rig floor, a stand is pulled out of the
fingerboard pipe rack. The top of the stand is placed in an
elevator, and the lower end aligned with a top of the drill string
at well centre. A lower threaded pin end of the stand of drill pipe
is stabbed into an upper box of the drill string and threadedly
connected using the iron roughneck. Drilling then continues using
rotation of a top drive, a rotary table or downhole motor. The
drill string can be many hundreds or thousands of metres long.
[0004] The borehole may be substantially vertical and may comprise
deviated portions. A deviated portion of a borehole may be
horizontal. A horizontal portion of a bore may be several
kilometres long.
[0005] The drill bit is usually arranged in a Bottom Hole Assembly
at the bottom end of a drill string. The drill bit has a pin end
with a male thread and has a flow bore leading to a body of the
drill bit. The body of the drill bit has a number of cutting
elements with a plurality of nozzles therebetween. Drilling mud
flows down through the flow bore and out through the nozzles to
inter alia carry drill cuttings from the drill bit through the
annulus.
[0006] The drill bit is usually threaded into a box end of a
stabilizer. The stabilizer attempts to reduce vibration induced by
the drill bit progressing through the formation and to improve
directional stability. The stabilizer is generally a thick walled
tubular with a plurality of spaced blades thereabout which may be
arranged in parallel curved paths which may be helical, or spiral.
The spaced blades define interleaved valleys. The valleys may also
follow a helical or spiral path to inter alia facilitate the flow
of drill cuttings laden drilling mud in the annulus around and
along the bottom hole assembly. The stabilizer usually has an upper
box end into which further components of a Bottom Hole Assembly are
attached. Such components may include: a Measurement While Drilling
(MWD) tool, for obtaining data; a Logging While Drilling tool, for
logging the data; further stabilizers; drill collars for providing
weight to facilitate Weight On Bit (WOB); a jar for providing a
shock to BHA if a tool or drill bit becomes stuck in the borehole;
and cross-over subs having pin-to-pin connectors.
[0007] The drill string may be pulled out of the borehole for many
reasons, such as: to change the drill bit; to allow for a string of
casing to be lowered into the borehole for casing the borehole; to
hang a liner; to set a whipstock for deviated drilling; to lower
milling tools; to fish for stuck tools; to clean the borehole; and
prepare the borehole for production. The step of pulling the drill
string out of the borehole is known as "tripping-out" and the step
of lowering the drill string back into the borehole is known as
"tripping-in". During tripping, the string of drill pipe is not
rotated or only rotated slowly in order to facilitate a smooth
movement along a borehole, which may be vertical, deviated or
partly horizontal.
[0008] As the drill string is pulled out of the borehole, a stand
of drill pipe is disconnected using an iron rough neck and the
stand placed back into the fingerboard pipe rack, usually using a
pipe handling tool, such as a racker.
[0009] During tripping-out, circulation of drilling mud through the
drill string may be maintained to inter alia maintain a constant
head of drilling mud in the well, inhibit solids suspended in the
drilling mud from settling out; and to maintain a constant pressure
in the borehole to inhibit the borehole collapsing. During tripping
out more drilling mud will be added to the well to replace the
drill pipe removed from the borehole. During tripping-in drilling
mud will be displaced from the borehole as the drill string is
lowered into the well.
[0010] It is common to stop circulation of drilling mud during
tripping. Although it is common during tripping to circulate
drilling mud between making or breaking a threaded connection
between a stand of drill pipe and the drill string. It is also
possible to have a continuous circulation of drill mud during
tripping using a Continuous Circulation System to maintain
continuous circulation of drilling mud through the entire drill
string during making or breaking a connection,
SUMMARY OF THE DISCLOSURE
[0011] A stabilizer incorporates a plurality of blades with
interleaved valleys and may have a ring or ring segments between
the blades over the valleys forming flow passages. Upon upward
movement of the stabilizer, such as being lifted, reciprocated or
upon tripping-out, an upper face of the ring may scrape along a
wall of the borehole, collecting small solids, such as clay
particles, which can agglomerate to form clumps, known as balling.
Once a small clump forms, solids suspended in the drilling mud may
additionally land on the clump, increasing the clump's size. The
clumps stick to the stabilizer, possibly blocking flow passages and
can also fall into the well. The clumps can build up in parts of
the borehole and in a worse case, block the borehole. Upon
tripping-in and during drilling, a bottom face of the ring may
scrape along a wall of the borehole, collecting small solids, such
as clay particles, which can agglomerate to form clumps, known as
balling. Once a small clump forms, solids suspended in the drilling
mud may additionally land on the clump, increasing the clump's
size. These clumps may block or partially block the flow passages
defined by the ring and the valleys.
[0012] Furthermore, the balling may occur around the ring or ring
segment during drilling.
[0013] There is disclosed a stabilizer for use in drilling a
borehole, the stabilizer comprising a cylindrical body having an
inner wall defining a flow bore and a plurality of blades extending
outwardly from said cylindrical body with a valley disposed between
adjacent blades, the stabilizer further comprising at least one
ring segment spaced from said cylindrical body over at least one
valley to define a flow passage characterised in that said
cylindrical body further comprises at least one fluid passageway or
"hole" therein for conveying drilling mud from said flow bore to
between the blades.
[0014] The hole may provide a flow path for fresh drilling mud to
flow out of the flow bore and direct the flow to inhibit clumps of
drill cuttings and other solids from forming, particularly but not
exclusively around the ring segment. The flow through the hole
exits the hole as a jet of fresh drilling mud. The jet may be
sufficient to break up clumps of drilled cuttings and other solids
which have already formed.
[0015] The hole may have any suitable cross-sectional shape, such
as circular, oval, square, rectangular, slot-like or polygonal.
There may be more than one hole under each ring segment. The holes
may be pointed in different directions.
[0016] Optionally, the hole comprises an entrance in said inner
wall and an exit in the at least one valley. Having the exit
positioned in the valley facilitates direction of the flow of fresh
drilling mud therefrom in a radial direction. Optionally, the hole
has an exit directed through at least a portion of the flow
passage. The flow of fresh drilling mud through the flow passage
may facilitate fluidizing solids knocked, scraped or reamed from
the formation surrounding the borehole by the ring segment. The
flow of fresh drilling mud through the flow passage may encourage a
smooth flow of solids-laden drilling mud therethrough. Optionally,
the exit of the hole is located underneath the ring segment, which
may encourage solids-laden drilling mud to be pulled through as
well as pushing solids through the ring, and may prevent solids
from settling on the ring. Preferably, the exit of the hole is
located underneath the ring segment, towards a bottom face thereof,
which may allow the jet to develop and have a spread which
facilitates removal of settled solids and solids about to settle on
and about the ring segment.
[0017] Optionally, the hole is lined with a liner. The liner may
provide erosion resistance in the body around the entrance, exit
and along the length of the hole. Optionally, the liner projects
into the flow bore of the stabilizer, which may help reduce the
risk of erosion of the body around the entrance to hole.
Optionally, the liner is made from a wear resistant material, such
as tungsten carbide. Optionally, the hole comprises a nozzle having
a nozzle bore through which drilling fluid flows. The nozzle
provides a jet having known qualities, such as spread pattern and
speed. The nozzle may also be used to facilitate direction of the
jet of fresh drilling mud. The nozzle bore has a length and a
cross-sectional flow area which changes along the length. A change
in cross-sectional bore area may induce different jet speeds and
spread patterns. Optionally, the nozzle bore has a fluid entry end
which has a first flow area and a fluid exit end which has a
smaller flow area. The nozzle preferably reduces in diameter
between the fluid entry end and fluid exit end. The nozzle bore may
have a smooth internal surface which follows a curved path. The
nozzle may be replaceable, so that the nozzle can be replaced with
a nozzle having different flow characteristics, such as a different
ratio of entry and exit flow areas. Optionally, the nozzle has a
thread and the hole has a corresponding thread, such that the
nozzle can be threaded into the hole in the body of the
stabilizer.
[0018] Optionally, the body has a wall that varies in thickness,
and includes a thick wall in the valley along a portion of the
length of the blades and a thin wall under the ring or ring
segment. Thus, a greater flow area may be obtained under the ring,
whilst structural strength may not be excessively reduced thanks to
additional support provided by the ring or ring segment, including
a structural component that may be employed therein. Optionally,
the hole is arranged in a transition zone between the thick wall
portion and a thin wall portion. The hole is thus placed in a
position which minimises reduction of structural integrity, whilst
being placed in a position which provides a flow of fresh drilling
mud to inhibit solids from forming clumps on the ring segment.
Optionally, the stabilizer has a lower end provided with a box for
receiving a pin of a drill bit. Optionally, an entrance to the hole
is arranged in the body between the box and the ring.
[0019] Optionally, the hole is arranged at an obtuse angle to the
direction of flow of drilling mud through the flow bore. The obtuse
angle provides an acute angle at the exit when the hole is formed
along a linear path. The acute angle at the exit, in use, provides
a trajectory for the jet of fresh drilling mud. Optionally, the
hole is arranged at between 140 degrees and 170 degrees to the
direction of flow of drilling mud through the flow bore, and
optionally, between 150 degrees and 160 degrees.
[0020] Optionally, the ring segment is arranged between every
adjacent blade to form a complete ring about the stabilizer. Thus
each blade has two ring segments, one to the left and one to the
right. A complete ring may increase stability. Optionally, only one
ring segment spans between adjacent blades, such that on a
stabilizer with four blades there are only two ring segments, each
on an opposing side. Optionally, the blades are curved about a
central axis of the stabilizer. The curved blades may curve about
the axis by an angle such that the angle of all blades adds up to
at least 360 degrees. Thus a complete 360 degree contact with the
borehole is possible along the length of the blades. With such
blade contact, only one ring segment per blade may be provided,
whilst maintaining vibration control of the drill bit.
[0021] Optionally, the ring or ring segment is arranged on a part
of each of the blades, which may be a part axially aligned with a
main axis of the stabilizer. This may allow the flow passage to
have sides which are substantially axially aligned. Optionally, the
stabilizer further comprises an upper portion of thick walled pipe.
Optionally, the thick walled pipe has a box in an upper end to
facilitate connection in a bottom hole assembly. Optionally, the
upper portion has a recess therein for holding a measuring while
drilling ("MWD") device.
[0022] There is disclosed a stabilizer for use in drilling a
borehole, the stabilizer comprising a cylindrical body having an
inner wall defining a flow bore and a plurality of blades extending
outwardly from the cylindrical body with a valley formed between
adjacent blades, the stabilizer further comprising at least one
ring or ring segment spaced from the cylindrical body characterised
in that the cylindrical body further comprises at least one hole
therein for conveying drilling mud from the flow bore.
[0023] A drill bit incorporates a plurality of blades with
interleaved valleys and may have a ring or ring segments between
the blades over the valleys forming flow passages. Upon upward
movement of the drill, such as being lifted, reciprocated or upon
tripping-out, an upper face of the ring may scrape along a wall of
the borehole, collecting small solids, such as clay particles,
which can agglomerate to form clumps, known as balling. Once a
small clump forms, solids suspended in the drilling mud may
additionally land on the clump, increasing the clump's size. The
clumps stick to the drill bit, possibly blocking flow passages and
can also fall into the well. The clumps can build up in parts of
the borehole and in a worse case, block the borehole. Upon
tripping-in and during drilling, a bottom face of the ring may
scrape along a wall of the borehole, collecting small solids, such
as clay particles, which can agglomerate to form clumps, known as
balling. Once a small clump forms, solids suspended in the drilling
mud may additionally land on the clump, increasing the clump's
size. These clumps may block or partially block the flow passages
defined by the ring and the valleys.
[0024] Furthermore, balling may occur around the ring or ring
segment during drilling.
[0025] There is disclosed a drill bit for use in drilling a
borehole, the drill bit comprising a cylindrical body having an
inner wall defining a flow bore for conveying fresh drilling mud
and a plurality of blades extending outwardly from the cylindrical
body with a valley disposed between adjacent blades, the drill bit
further comprising at least one ring segment spaced from the
cylindrical body over at least one valley to define a flow passage
through which cuttings-laden drilling mud flows, the cylindrical
body further comprises at least one fluid passageway or "hole"
therein for conveying drilling mud from the flow bore,
characterised in that the hole has an exit directed to provide
fresh drilling mud with a trajectory passing through at least a
portion of the flow passage.
[0026] There is disclosed a drill bit for use in drilling a
borehole, the drill bit comprising a cylindrical body having an
inner wall defining a flow bore for conveying fresh drilling mud
and a plurality of blades extending outwardly from the cylindrical
body with a valley disposed between adjacent blades, the drill bit
further comprising at least one ring segment spaced from the
cylindrical body over at least one valley to define a flow passage
through which cuttings laden drilling mud flows, the cylindrical
body further comprises at least one fluid passageway or "hole"
therein for conveying drilling mud from the flow bore,
characterised in that the hole has an exit in the flow passage.
[0027] There is disclosed a drill bit for use in drilling a
borehole, the drill bit comprising a cylindrical body having an
inner wall defining a flow bore for conveying fresh drilling mud
and a plurality of blades extending outwardly from the cylindrical
body with a valley disposed between adjacent blades, the drill bit
further comprising at least one ring segment spaced from the
cylindrical body over at least one valley to define a flow passage
through which cuttings laden drilling mud flows, the cylindrical
body further comprises at least one fluid passageway or "hole"
therein for conveying drilling mud from the flow bore,
characterised in that the hole is arranged at an obtuse angle to
the direction of flow of drilling mud through the flow bore.
[0028] Optionally, the hole comprises an entrance in the inner wall
and an exit in the at least one valley. Optionally, the hole has an
exit directed through the flow passage. Optionally, the exit of the
hole is located beneath the ring segment. Optionally, the exit of
the hole is located underneath the ring segment, preferably towards
a bottom face thereof. Optionally, the hole is lined with a liner.
Optionally, the liner projects into the flow bore of the drill bit.
Optionally, the liner is made from a wear resistant material, such
as tungsten carbide. Optionally, the hole comprises a nozzle having
a nozzle bore through which drilling fluid flows. Optionally, the
nozzle bore has a length and a cross-sectional flow area which
changes along the length. Optionally, the nozzle bore has a fluid
entry end which has a first flow area and a fluid exit end which
has a smaller flow area. The nozzle optionally reduces in diameter
between the fluid entry end and fluid exit end. The nozzle bore
optionally has a smooth internal surface which follows a curved
path. Advantageously, the nozzle is replaceable, so that the nozzle
can be replaced with a nozzle having different flow
characteristics, such as a different ratio of entry and exit flow
areas. Optionally, the nozzle has a thread and the hole has a
corresponding thread, such that the nozzle can be threaded into the
hole in the body of the drill bit.
[0029] Optionally, the body has a thick wall in the valley along a
portion of the length of the blades and a thin wall under the ring
or ring segment. Optionally, the hole is arranged in a transition
zone between the thick wall portion and thin wall portion.
Optionally, an exit of the hole is arranged under the ring.
Preferably, the hole is arranged at an obtuse angle to the
direction of flow of drilling mud through the flow bore.
Optionally, the hole is arranged at between 140 degrees and 170
degrees to the direction of flow of drilling mud through the flow
bore and optionally, between 150 degrees and 160 degrees.
[0030] Optionally, the ring segment is arranged between every
adjacent blade to form a complete ring about the drill bit. Thus
each blade has two ring segments, one to the left and one to the
right. Optionally, only one ring segment spans between adjacent
blades, such that on a drill bit with four blades there are only
two ring segments, each on an opposing side.
[0031] Optionally, the ring or ring segment is arranged on a part
of each of the blades.
[0032] Optionally the part of each blade is axially aligned with a
main axis of the drill bit.
[0033] Also disclosed is a bottom hole assembly comprising a
stabiliser and/or a drill bit in accordance with an embodiment of
the present disclosure.
[0034] Also disclosed is a method of tripping using a stabilizer
and/or drill bit in accordance with an embodiment of the present
disclosure, the method comprising the steps of circulating drilling
mud through the flow bore, a portion of the drilling mud passing
through the hole and through the flow passage.
[0035] Thus solids which are scraped off the wall of the borehole
or have otherwise collected on the ring segment, are fluidised or
inhibited from forming clumps. The solid particles are thus
suspended in the drilling mud and circulated as any other solids in
the drilling mud, such as drill cuttings. Clumps which may have
already formed may be broken up by the jet of fresh drilling mud.
The drill cuttings-laden drilling fluid in the flow passage is
diluted with fresh drilling mud by a small amount.
[0036] Optionally, the drilling mud is circulated between threading
operations. Optionally, the drilling mud is also circulated during
threading operations with a circulating head. Optionally, the
circulating head comprises a seal which seals inside the drill
string or about the drill string, so that a threaded connection
does not have to be made in order to circulate drilling mud through
the drill string. Optionally, the drill string is threadedly
connected to a rotor of a top drive and the drilling mud circulated
therethrough. Optionally, a continuous circulation system is used
to maintain circulation of drilling mud throughout tripping.
[0037] Also disclosed is a method of drilling a borehole using a
drill bit or stabilizer in accordance with an embodiment of the
present disclosure, the method comprising the steps of circulating
drilling mud through the flow bore, a portion of the drilling mud
passing through the hole and through the flow passage. Optionally,
the drilling mud is circulated continuously during drilling.
[0038] Also disclosed is a method of drilling a borehole using a
drill bit in accordance with an embodiment of the present
disclosure, the method comprising the steps of circulating drilling
mud through the flow bore, a portion of the drilling mud passing
through the hole and through the flow passage. Optionally, the
drilling mud is circulated continuously during drilling.
[0039] Also disclosed is an apparatus for use in a bottom hole
assembly in drilling a borehole, the apparatus comprising a
cylindrical body having an inner wall defining a flow bore and a
plurality of blades extending outwardly from the cylindrical body
with a valley disposed between adjacent blades, the apparatus
further comprising at least one ring segment spaced from the
cylindrical body over at least one valley to define a flow passage,
characterised in that the cylindrical body further comprises at
least one hole therein for conveying drilling mud from the flow
bore. The apparatus may be one of a drill bit, stabilizer, on-gauge
sub or other BHA component.
BRIEF DESCRIPTION OF THE DRAWINGS
[0040] For a better understanding of the disclosed exemplary
embodiments of the invention, reference will now be made to the
accompanying drawings, in which:
[0041] FIGS. 1A and 1B show a schematic view of a drilling rig
constructing a wellbore with a drill string comprising a stabilizer
in accordance with certain of the embodiments disclosed herein;
[0042] FIG. 2 is a perspective view of a stabilizer in accordance
with a disclosed embodiment, the stabilizer shown before a layer of
hardfacing material has been applied;
[0043] FIG. 3 is a side view of the stabilizer shown in FIG. 2;
[0044] FIG. 4 is an end view of the stabilizer shown in FIG. 2;
[0045] FIG. 5 is an enlarged view in section of a part of the
stabilizer shown in FIG. 2 taken along line V-V, shown with a layer
of hardfacing material applied to parts thereof, showing details of
a nozzle;
[0046] FIG. 6a is a side view of the nozzle shown in FIG. 5;
[0047] FIG. 6b is an end view of the nozzle shown in FIG. 6a;
[0048] FIG. 6c is a view in section taken along line VIc-VIc shown
in FIG. 6b;
[0049] FIG. 7 shows an alternative to the part of the stabilizer
shown in FIG. 5;
[0050] FIG. 8 shows a further alternative to part of the stabilizer
shown in FIG. 7;
[0051] FIG. 9 is a perspective view of the stabilizer shown in FIG.
2 with hardfacing material applied to parts thereof;
[0052] FIG. 10 is a drill bit in accordance with an exemplary
embodiment disclosed herein; and
[0053] FIG. 11 is a view in cross-section of part of the drill bit
shown in FIG. 10.
DETAILED DESCRIPTION OF THE DISCLOSED EXEMPLARY EMBODIMENTS
[0054] Referring to FIGS. 1a and 1b there is shown a drilling rig
generally identified by reference numeral 1. The drilling rig 1 has
a derrick 2 arranged on a drill floor 3 supported on legs 4. The
legs 4 are seated on a substructure 5 on ground 6.
[0055] A top drive apparatus 7 is arranged on a carriage 10' raised
and lowered with a travelling block 8 on line 9 along a vertical
track 10. The line 9 passes over a crown block 11 located at a top
of the derrick 2 and down to a drawworks 12 on the rig floor 3 for
reeling the line 9 in and out. A stand of drill pipe 13 depends
from an elevator 14. The elevator 14 depends from links 15 which
are looped over ears 16 of a swivel 16a of the top drive apparatus
7.
[0056] A drill string 17 passes through a spider 18 in the drill
floor 3, through a wellhead 19 into a borehole 20 in formation 21.
A bottom hole assembly 22 is arranged on a lower end of the drill
string 17. The bottom hole assembly 22 comprises a drill bit 23
connected to a stabilizer 100 on a lower end thereof. The bottom
hole assembly also comprises a Measurement While Drilling tool 24,
a further stabilizer 25 and a drill collar 26. A mud motor may also
be incorporated into the bottom hole assembly. An annulus 29 is
defined between the borehole 20 and the bottom hole assembly
22.
[0057] A flow line 30 is fluidly connected at one end to an annulus
29 at the wellhead 19 and the other end to an active mud system 31.
The annulus 29 is an annular flow passage defined by the formation
21 (or casing (not shown) if the borehole is cased) and an outer
surface of the drill string 17 or bottom hole assembly 22. Returned
solids-laden drilling mud DM flows from the annulus 29, through
wellhead 19, into flow line 30 and to the active mud system 31,
which cleans and processes the solids-laden drilling mud DM to
produce fresh drilling mud M. The active mud system 31 comprises a
trip tank, an active mud tank and a series of pieces of mud
processing equipment, such as: a shale shaker, a degasser, a mud
conditioner, and a centrifuge. Fresh drilling mud M is pumped with
a mud pump MP at a pressure up to between 200 bar and 1000 bar at
between 300 and 4800 litres per minute from the active mud system
31 through a hose 32 to a goose neck connection 33 on top drive 34
of the top drive apparatus 7. Processed and now fresh drilling mud
flows through the goose neck connection 33 into a main rotating
shaft 35. The drilling mud continues to flow through an Internal
Blow Out Preventer (IBOP) 36 and sub 37 and through the drill
string 17, when connected.
[0058] An iron rough neck 38 is arranged on the rig floor 3 for
rotating the stand of drill pipe 13 relative to the static drill
string 17 to thread the stand of drill pipe 13 to the drill string
17 or unthread the stand of drill pipe 13 from the drill string
17.
[0059] The stand of drill pipe 13 is threaded and torqued to the
drill string 17 using the iron roughneck 38. The sub 37 of the top
drive apparatus 7 is threadedly connected to the top of the
connected stand of drill pipe 13. The top drive 34 is activated to
rotate the drill string 17, if desired. The drill bit 23 drills
through the formation 21 extending the borehole 20. The drilling
mud M is circulated through the drill string 17 and out of nozzles
in the drill bit 23, washing drilled solids through the annulus to
the active mud system 31. Rate Of Penetration of the drill bit 23
in a formation may vary dramatically, but may often be in the order
of 30 metres per hour.
[0060] When required, the drill string 17 is tripped-out of the
borehole 20. During tripping-out, the sub 37 of the top drive
apparatus 7 is not usually threadedly mated with the drill string
17, thus the top drive 34 is not rotationally connected to the
drill string 17 or stands of drill pipe 13. The elevator 14 is used
to raise the drill string 17 until typically two, three or four
joints of drill pipe are above the rig floor 3. The iron roughneck
38 is used to disconnect a stand of drill pipe 13. A single joint
elevator system 46 may be used to set the stand of drill pipe 13
back into a finger board pipe rack 44, which stores a multiplicity
of stands of drill pipe 45. The elevator 14 is then lowered with
the top drive apparatus 7 until it is just below the box end of the
stem 49 of the drill string 17. The elevator 14 is opened and
clamped or slideably looped around the stem 49 of the drill string
17 above the rig floor 3. The operation is repeated until the
entire drill string 17 and bottom hole assembly 22 are out of the
borehole 20. Accordingly, tripping-out is usually very quick and
can be carried out at 600 metres per hour with modern rigs and
experimental rigs expect tripping-out at up to 3,600 metres per
hour.
[0061] When required, the drill string 17 is tripped-in to the
borehole 20. During tripping-in, the sub 37 of the top drive
apparatus 7 is not usually threadedly mated with the drill string
17, thus the top drive 34 is not rotationally connected to the
drill string 17 or stands of drill pipe 13. A single joint elevator
system 46 may be used to pull a stand of drill pipe 13 from the
finger board pipe rack 44, which stores a multiplicity of stands of
drill pipe 45 and is placed in an elevator 14 hanging above stem 49
at well-centre. The iron roughneck 38 on the rig floor 3 is used to
connect the stand of drill pipe 13 to the stem 49. The elevator 14
is raised with the top drive apparatus 7 to lift the drill string
17 a little to allow the spider 18 to be released. The elevator 14
is then lowered with the top drive apparatus 7 until only a stem 49
of the drill string 17 is above the rig floor 3. The operation is
repeated until the entire drill string 17 and Bottom Hole Assembly
22 are at the bottom of the borehole 20. Accordingly, tripping-in
is usually very quick and can be carried out at 600 metres per hour
with modern rigs and experimental rigs expect tripping-out at up to
3,600 metres per hour.
[0062] Optionally, the sub 37 of the top drive apparatus 7 is
threadedly mated with the drill string 17 to allow circulation of
drilling mud.
[0063] Optionally, a circulating head 50 is connected to the sub
37. Reference is made to WO 2009/098473, WO 2009/098474, WO
2009/098478, WO 2009/098482, WO 2010/089572, WO 2010/089573 which
are hereby incorporated by reference for all purposes. The
circulating head 50 has a spear 51 which moves axially into a
sealing engagement with the top end of the stand of drill pipe 13
held in the elevator 14, which has been threadedly connected to the
drill string 17. Thus a continuous flow path between the goose neck
33 and the drill string 17 is now provided to allow drilling mud to
circulate through the drill string 17 from the goose neck 33. As
the drill string 17 is raised when tripping-out or lowered when
tripping-in, drilling mud can circulate. The sealing engagement is
rated to approximately 5,000 psi (320 bar) to allow
circulation.
[0064] Optionally, a continuous circulation system may be used,
such as the continuous circulation system (CCS) 55 manufactured by
the National Oilwell Varco, which provides a continuous circulation
of drilling mud during tripping-in and tripping-out. Reference is
made to WO 98/16716, which is hereby incorporated by reference for
all purposes. The CCS 55 is moved to well-centre and fits about the
pipe stub 49. A lower seal seals about the stem 49 and allows
drilling mud to flow from the MS into the stem 49 of the drill
string 17 via a flow line even when the stand of drill pipe 13 is
disconnected from the stem 49. The bottom end of the stand of drill
pipe 13 is lowered into the CCS 55 and an upper seal seals
thereabout. A middle seal is opened which provides a flow path for
drilling mud to flow from the goose neck 33 through the top drive
34 into the drill string 17. The flow of drilling mud through the
flow line is stopped, and the stand of drill pipe 13 in threaded to
the stem 49. The drill string can then be tripped-in. The reverse
procedure is used when tripping-out.
[0065] Referring to FIGS. 2 to 5 and 9, there is shown a stabilizer
100 in accordance with an exemplary embodiment of the disclosure.
The stabilizer 100 has an upper portion 101 of heavy weight pipe
and a lower portion 102. The lower portion 102 has a body 103 made
from a single piece of steel, such as a steel comprising chromium
and/or molybdenum and to the standard AISI 4145. The body 103 has a
flow bore 104 extending from a top end 106 to a bottom end 108 of
the body 103, which provides a drilling mud flow path from the
drill string 17 to the drill bit 23. The flow bore 104 is
preferably of circular cross-section and has a constant diameter
along at least a portion of the length of the lower portion 102.
The drilling mud M flows in a downward direction MA along axis AX.
A stub connector 105 is located at the top end 106 of the lower
portion 102 to provide a connection with the upper portion 101. The
stub connector 106 has an external surface which is welded to the
upper portion 102. An internally threaded box 107 is provided at
the bottom end 108 of the body 103. The internally threaded box 107
has a thread 109 for providing a connection with a pin end (not
shown) of drill bit 23.
[0066] The body 103 has four equally spaced blades 110, 111, 112
and 113 defining four valleys 114, 115, 116 and 117. Each blade
110, 111, 112 and 113 has a curved portion which extends in a
curved path about the axis AX, which may be a helical or spiral
path from the bottom end 108 towards the top end 106 in a clockwise
direction when viewed from the bottom end as shown in FIG. 4. Each
curved portion of each blade 110, 111, 112 and 113 has a width
which circums approximately 40 degrees and extends along the curved
path to circum approximately 90 degrees, when viewed from the
bottom end as shown in FIG. 4. All four blades 110, 111, 112 and
113 follow the curved path to circum approximately ninety degrees
each to complete 360 degrees of the circumference of the body 102.
Each blade 110, 111, 112 and 113 has a lead end 118, 119, 120 and
121 and a trailing end 122, 123, 124 and 125. Each lead end 118,
119, 120, 121 has a sloped lead face rising from the bottom end 108
at a first perimeter 126, up to a table portion 127, 128, 129 and
130 located and following an outer perimeter. The table portion
127, 128, 129 and 130 follows an outer diameter. A step 131, 132,
133 and 134 is provided between a top of the sloped lead face and
the table portion 127, 128, 129 and 130. The table portion 127,
128, 129 and 130 is hardfaced. Beads of hardfacing material 135 are
shown on blade 110 in FIG. 5 and FIG. 9. Beads of hardfacing
material 135 may be applied by a plasma transfer arc or a tungsten
powder spray or any other suitable means. The hardfacing material
may have diamonds inserted therein. The outer ridges of the beads
of the hardfacing material 135 preferably has the same diameter as
the diameter of a gauge 136 of the drill bit 23, as shown in FIG.
10.
[0067] A ring segment 140 is arranged between trailing ends 122 and
123 of blades 110 and 111. The ring segment 140 lies transverse to
the main axis AX of the body 103. The ring segment 140 forms a
bridge over the valley 114 defining a cuttings-laden drilling mud
flow path 142 between the body 103 and the ring segment 140, as
best shown in FIG. 5. The valley 114 circums approximately 50
degrees when viewed from the end, as shown in FIG. 4. The
cross-sectional area available in which the cuttings-laden drilling
mud flows at any given point along the length of the stabilizer 100
is known as a Junk Slot Area, the units of which is square inches
(or square mm). The Junk Slot Area at any point under the ring
segment 140 is typically between 9 and 14 sq inches (5,800 to 9,000
sq mm).
[0068] A ring segment 144 is arranged between trailing ends 124 and
125 of blades 112 and 113. The ring segment 140 lies transverse to
the main axis AX of the body 103. The ring segment 144 forms a
bridge over the valley 116 defining a cuttings-laden drilling mud
flow path, like ring segment 140. The valley 116 circums
approximately 50 degrees when viewed from the end, as shown in FIG.
4. The Junk Slot Area at any point under the ring segment 144 is
typically between 9 and 14 sq inches (5,800 to 9,000 sq mm) and is,
in this example, the same as cuttings-laden drilling mud flow path
142.
[0069] An outer surface 141 of the ring segment 140 has a ring
perimeter which is the same as the outer perimeter of the table
surface 127, 128, 129 and 130. The ring segments 140 and 144 are
hardfaced. Beads of hardfacing material 135 may be applied by a
plasma transfer arc or a tungsten powder spray or any other
suitable means. The hardfacing material may have diamonds inserted
therein. The outer ridges of the beads of the hardfacing material
135 in this example has the same diameter as the diameter of gauge
136 of the drill bit 23 and may be 1/8'' (3.2 mm) smaller than the
diameter of the borehole 20. Optional cutters 145 and 146 may be
arranged on a rotationally leading end 147 and 148 of the ring
segments 140 and 144.
[0070] The trailing ends 122 and 123 of the blades 110 and 111 have
an axial portion 149 and 150 between the curved portion and
respective ends of the ring segment 140. An inclined leading radial
land 151 is defined by part of an end face 152 of the curved
portion of blade 111, a part of a bottom face 153 of the ring
segment 140, the outer diameter and a line above the base of the
valley 114. An end face 155 of the curved portion of blade 110
forms an inclined trailing radial land, bound at a top corner by a
part of a bottom face 153 of the ring segment 140, the outer
diameter and a curved inclined line above the base of the valley
114.
[0071] The trailing ends 124 and 125 of the blades 112 and 113 have
an axial portion 156 and 157 between the curved portion and
respective ends of the ring segment 144. An inclined leading radial
land 158 is defined by part of an end face 159 of the curved
portion of blade 113, a part of a bottom face 160 of the ring
segment 144, the outer diameter and a line above the base of the
valley 116. An end face 161 of the curved portion of blade 112
forms an inclined trailing radial land, bound at a top corner by a
part of a bottom face 160 of the ring segment 144, the outer
diameter and a curved inclined line above the base of the valley
116.
[0072] The ring segment 140 has a top face 166, which is of a
smaller radial thickness than bottom face 153, but has the same
outer diameter. The body 103 has a reduced thickness B under a
portion of the ring segment 140 and a corresponding increased
cross-sectional flow area 142 therebetween. The floor of the
valleys 114 and 116 curves downwardly undulating down underneath
the ring segment 140 and 144 respectively and upwardly after the
respective ring segment 140 and 144. Thus the thickness of the body
103 undulates from thickness A below the ring segment 140, 144 to
the smaller thickness B under the ring segment 140, 144 to
thickness C above the ring segment 140, 144.
[0073] At least one system is arranged in the body 103 that
comprises a hole 170 in a sloped region in which the body 103
decreases in thickness from thickness A to thickness B. The hole
170 follows a linear path from the flow bore 104 through the body
103 to an exit in the valley 114. In this manner, hole 170 is a
fluid passageway between flow bore 104 and the borehole annulus 29.
The hole 170 is disposed at a obtuse angle to the general direction
of flow of drilling fluid through the flow bore 104, of optionally
between one hundred and fifty to one hundred and sixty degrees. As
is used herein, an angle that is obtuse relative to the general
direction of flow of drilling fluid through the flow bore means the
angle existing between the hole 170 and the direction of the
drilling fluid in the flow bore 104 after it has passed by hole 170
and is moving towards the bottom of the borehole 20, not as the
fluid is approaching the hole 170. The hole 170 comprises an inner
portion 171 having a smooth inner wall having a first diameter, and
an outer portion 172 of a larger diameter, with a shoulder 173
therebetween. A liner, for example a sleeve 175 has a smooth inner
surface defining a bore 176 and smooth outer surface with an
outwardly projecting flange 177 at a proximal end. The sleeve 175
is insertable through the upper portion 172 of the hole 170 and
slid therein until the flange 177 abuts the shoulder 173. The upper
portion 172 of the hole 170 is at least partly internally threaded.
A nozzle 180 is threaded into internal threads of the upper portion
172 of the hole 170 which locks the sleeve 175 in place. A first
end of the sleeve 175 projects into the flow bore 104, and this end
may have an upper point in line with the bore of the borehole 204
and a lower part projecting in to the flow bore 204. The sleeve 175
is preferably made from a tungsten-carbon material, resistant to
erosion. The sleeve 175 inhibits erosion in the body 103 around the
hole 170 induced by the flow of drilling mud through the flow bore
104 and through the hole 170. The hole 170 may be between 10 mm to
25 mm in diameter and in this example 17 mm to 20 mm in
diameter.
[0074] The nozzle 180 is shown in more detail in FIGS. 6a to 6c,
which has a cylindrical body 181 of circular cross-section having
an entrance portion provided with a male thread 182 for threaded
engagement in the female threads of hole 170. An exit portion 183
is castellated having four upstands 184 with interleaved notches
185. A nozzle bore 186 has a large diameter at the entrance,
converging non-linearly to a small diameter bore at the exit.
[0075] A corresponding system may be provided on the other side of
the stabilizer 100 for ring segment 144.
[0076] When the bottom hole assembly 22 is at the bottom of the
borehole 20, the drill bit 23 and stabilizer 100 are rotated,
either by the top drive 34, a rotary table (not shown) or a mud
motor (not shown) to extend the borehole 20. Mud pump MP is used to
pump fresh drilling mud M through the drill string 17, which flows
through the flow bore 104 of the stabilizer 100. The majority of
the fresh drilling mud M continues on to the drill bit 23, through
nozzles therein and washes drill cuttings up through the annulus 29
back to the mud system 31 located at surface 6. However, a small
portion of the fresh drilling mud M passes through the hole 170 in
the body 103 of the stabilizer 100. The pressure in the flow bore
104 may be different from the pressure in the cuttings-laden
drilling mud in the annulus 29 at the flow path 142, at the exit of
the hole 170. The pressure is typically higher in the fresh
drilling mud M in the flow bore 104 than in cuttings-laden drilling
mud in the annulus 29 at the exit of the hole 170. Fresh drilling
mud M flows from the flow bore 104 through hole 170 into the flow
path 142 defined by the ring segment 140 and the valley 114.
[0077] A fast jet of fresh drilling mud M is induced by a reduction
in the diameter of the hole 170 by nozzle 180. The hole 170 and
nozzle 180 are directed upwardly through the cuttings-laden
drilling mud flow path 142 and optionally, at a region above the
top face 166 of the ring segment 140. The jet of fresh drilling mud
may facilitate maintaining suspension of drill cuttings and other
solids in the cuttings-laden drilling mud. This may reduce the risk
of solids forming clumps on the top face 166 of the ring segment
140.
[0078] Upon the bottom hole assembly 22 being tripped-out of the
borehole 20, fresh drilling mud M may flow through the hole 170. If
the drilling fluid is circulated through the drill string 17 as
herein described, the flow of drilling mud through the flow bore
104 at the flow rate and pressure produced by the mud pump MP is
intended to induce a better flow through the hole 170. A good flow
rate through the hole 170, induces a jet of fresh drilling mud
directed through the cuttings laden drilling mud flow path 142. As
the stabilizer 100 is pulled through the borehole 20, the top
surface 166 of the ring segment 140 may scrape along the wall of
the borehole 20 scraping solid particles therefrom. The solid
particles may collect to form a clump on the ring segment 140.
However, the jet of fresh drilling mud through the cuttings-laden
drilling mud flow path 142 will stimulate the solids, inducing the
solids to fluidize and other drill cuttings and solids to remain
suspended in the drill mud.
[0079] Upon the bottom hole assembly 22 being tripped-in to the
borehole 20, fresh drilling mud M may flow through the hole 170. If
the drilling fluid is circulated through the drill string 17 as
hereinbefore described, the flow of drilling mud through the flow
bore 104 is intended to induce a better flow through the hole 170.
A good flow rate through the hole 170, induces a jet of fresh
drilling mud directed through the cuttings-laden drilling mud flow
path 142. As the stabilizer 100 passes down through the borehole
20, the bottom face 153 of the ring segment 140 may scrape along
the wall of the borehole 20 scraping solid particles therefrom. The
solid particles may collect to form a clump on the ring segment
140. However, the jet of fresh drilling mud through the
cuttings-laden drilling mud flow path 142 will stimulate the
solids, inducing the solids to fluidize and other cuttings and
solids to remain suspended in the drill mud and pull them through
the cuttings-laden drilling mud flow path 142.
[0080] Such methods for circulating drilling mud through the drill
string whilst tripping include threadedly connecting the drill
string to a sub 37 of the top drive apparatus 7 during tripping.
This may be carried out between each connection or disconnection of
a stand of drill pipe 13, or once every two, three or more
connections or disconnections.
[0081] Alternatively, circulating drilling mud through the drill
string whilst tripping may be employed using a circulating whilst
tripping tool, which allows circulation between making and breaking
threaded connections, without the need for making a threaded
connection with the sub 37.
[0082] Alternatively, circulating drilling mud continuously through
the drill string 17 whilst tripping may be employed using a
Continuous Circulation System 55, such as the CCS.TM. manufactured
by the National Oilwell Varco.
[0083] FIG. 7 shows a further exemplary embodiment in which
reference numerals in the two hundred series are used for similar
parts referred to previously in the one hundred series. The system
269 comprises a fluid passageway or hole 270 through the body 203
which is partly lined with a sleeve 275. The sleeve 275 is arranged
at an obtuse angle to the direction of flow in flow bore 204. The
sleeve 270 has an inner portion 271 which is of a smaller diameter
than a threaded outer portion 272, with a shoulder therebetween. A
proximal end of the sleeve 275 has a threaded flange 277 threaded
into the threaded outer portion 272 and is seated on the shoulder
273. A first end of the sleeve 275 extends into the flow bore 204.
The first end may have an upper point in line with the bore of the
borehole 204 and a lower part projecting in to the flow bore 204.
Alternatively, the sleeve 275 may line the entire length of the
hole 270. The system 269 may be used in the stabilizer 100 or drill
bit 23. A flow axis of the sleeve 275 is directed through a
cuttings-laden drilling mud flow path 242 defined by the ring
segment 240 and the body 203.
[0084] In use, fresh drilling mud M flows from flow bore 204,
through the sleeve 275 and exits the sleeve 275 as a jet of fresh
drilling mud directed upwardly through the cuttings-laden drilling
mud flow path 242. Optionally the jet has a trajectory aimed at a
region above the top face 266 of the ring segment 240 which may
reduce the risk of solids forming clumps on the top face 266 and
bottom face 253 of the ring segment 240.
[0085] FIG. 8 shows a yet further exemplary embodiment of the
invention, in which reference numerals in the three hundred series
are used for similar parts referred to previously in the one
hundred series. The system 369 comprises a fluid passageway or hole
370 through the body 303 which is arranged at an obtuse angle to
the direction of flow in flow bore 304. The system may be used in
the stabilizer 100 or drill bit 23. A flow axis of the hole 370 is
directed through a cuttings-laden drilling mud flow path 342
defined by the ring segment 340 and the body 303.
[0086] In use, fresh drilling mud M flows from flow bore 304,
through the hole 370 and exits the hole 370 as a jet of fresh
drilling mud directed upwardly through the cuttings laden drilling
mud flow path 342. Optionally, the jet has a trajectory aimed at a
region above the top face 366 of the ring segment 340 which may
reduce the risk of solids forming clumps on the top face 366 and
bottom face 353 of the ring segment 340.
[0087] FIG. 10 shows an example of a drill bit made in accordance
with certain of the principles disclosed herein. The drill bit 23
comprises a bit body 403 having a series of curved blades (two
shown) 410 and 411 with a valley (one shown) 412 therebetween. The
blades 410 and 411 curve around a forward end of the drill bit 23.
Each blade 410 and 411 has a rotationally leading face 413 and 414
each provided with a plurality of cutting elements 415 for boring
the borehole 20. A ring segment 416 is arranged between trailing
ends 417 and 418 of respective blades 410 and 411 spanning over
valley 412 to define a cuttings-laden drilling mud flow path 542
between bit body 403 and ring segment 416. The ring segment 416 has
cutting elements thereon at a rotational leading edge and trailing
edge, which may be set at a gauge diameter 136.
[0088] A system 569 is arranged in the body 403. The system 569 is
shown in more detail in FIG. 11, in which reference numerals in the
five hundred series are used for similar parts referred to
previously in the one hundred series. The system 569 comprises a
hole 570 that is a fluid passageway arranged in the body 403 on a
slope in a region in which the body 403 decreases in thickness from
thickness A to thickness B. The fluid passageway or hole 570
follows a linear path from the flow bore 504 through the body to an
exit in the valley 414. The hole 570 is disposed at an obtuse angle
to the direction of flow of drilling fluid through the flow bore
504, which in this example is between one hundred and thirty and
one hundred and fifty degrees. The hole 570 comprises an inner
portion 571 having a smooth inner wall having a first diameter and
an outer portion 572 of a larger diameter with a shoulder 573
therebetween. A liner, such as sleeve 575 has a smooth inner
surface defining a bore 576 and smooth outer surface with an
outwardly projecting flange 577. The sleeve 575 is insertable
through the upper portion 572 of the hole 570 and slid therein
until the flange 577 abuts the shoulder 573. The upper portion 572
of the hole 570 is at least partly internally threaded. A nozzle
580 is threaded into internal threads of the upper portion 572 of
the hole 570 which locks the sleeve 575 in place. A bottom of the
sleeve 575 projects into the flow bore 504. The sleeve 575 may be
made from a tungsten-carbon material, resistant to erosion. The
sleeve 575 inhibits erosion in the body 403 around the hole 570
induced by the flow of drilling mud through the flow bore 504 and
through the hole 570. The hole 570 may be between 10 mm to 25 mm in
diameter and in this example approximately 17 mm to 20 mm in
diameter.
[0089] When the bottom hole assembly 22 is at the bottom of the
borehole 20, the drill bit 23 and stabilizer 100 are rotated,
either by the top drive 34, a rotary table (not shown) or a mud
motor (not shown) to extend the borehole 20. Mud pump MP is used to
pump fresh drilling mud M down through the drill string 17, through
flow bore 504 of the drill bit 23. The majority of the fresh
drilling mud M continues on to flush out of nozzles forwardly in
front of the blades 410 and 411. However, a small portion of the
fresh drilling mud M flows out through the hole 570 in the body 403
of the drill bit 23. There may be a pressure difference between the
pressure of the fresh drilling mud M in the flow bore 504 and in
cuttings-laden drilling mud in the annulus 29 at the flow path 542,
at the exit of the hole 570. The pressure may be higher in the
fresh drilling mud M in the flow bore 504 than in cuttings laden
drilling mud in the annulus 29 at the exit of the hole 570. Fresh
drilling mud M flows from the flow bore 504 through hole 570 into
the flow path 542 defined by the ring segment 416 and the valley
412.
[0090] A fast jet of fresh drilling mud M is induced by a reduction
in the diameter of the hole 570 by nozzle 580. The hole 570 and
nozzle 580 are directed upwardly through the cuttings laden
drilling mud flow path 542 and preferably, at a region above the
top face 566 of the ring segment 416. The jet of fresh drilling mud
may facilitate maintaining drill cuttings and other solids
suspended in the cuttings-laden drilling mud flow path 542. This
preferably reduces the risk of solids forming clumps on the top
face 566 of the ring segment 416.
[0091] Upon the bottom hole assembly 22 being tripped-out of the
borehole 20, fresh drilling mud M may flow through the hole 570. If
the drilling fluid is circulated through the drill string 17 as
hereinbefore described, the flow of drilling mud through the flow
bore 504 at the flow rate and pressure produced by the mud pump MP
is intended to induce a better flow through the hole 570 and nozzle
580. A good flow rate through the hole 570 and nozzle 580, induces
a jet of fresh drilling mud directed through the cuttings laden
drilling mud flow path 542. As the drill bit 23 is pulled through
the borehole 20, the top surface 566 of the ring segment 416 may
scrape along the wall of the borehole 20 scraping solid particles
therefrom. The solid particles may collect to form a clump on the
ring segment 416. However, the jet of fresh drilling mud through
the cuttings-laden drilling mud flow path 542 will stimulate the
solids, inducing the solids to fluidize and stay suspended in the
drill mud.
[0092] Upon the bottom hole assembly 22 being tripped-in to the
borehole 20, fresh drilling mud M may flow through the hole 570. If
the drilling fluid is circulated through the drill string 17 as
hereinbefore described, the flow of drilling mud through the flow
bore 504 is intended to induce a better flow through the hole 570.
A good flow rate through the hole 570, induces a jet of fresh
drilling mud directed through the cuttings-laden drilling mud flow
path 542. As the drill bit 23 passes down through the borehole 20,
the bottom face 553 of the ring segment 416 may scrape along the
wall of the borehole 20 scraping solid particles therefrom. The
solid particles may collect to form a clump on the ring segment
416. However, the jet of fresh drilling mud through the cuttings
laden drilling mud flow path 542 will stimulate the solids,
inducing the solids to fluidize and stay suspended in the drill mud
and pull them through the cuttings laden drilling mud flow path
542.
[0093] The drill string usually comprises a multiplicity of
threaded joints of drill pipe. However, the drill string may
comprise a multiplicity of threaded sections of other kinds of
pipe, such as casing, which is known as drilling with casing.
* * * * *