Note: Descriptions are shown in the official language in which they were submitted.
In the forming of bore holes in the earth, more
particularly enlarged bore holes, for example, blast holes used
in bench mining or quarrying, it has become the practice to drill
a pilot hole to a givendepth and enlarge the hole to form a
large chamber for receiving a blasting explosive. Such bore
holes are also useful in connection with in-situ fragmentation
for chemical mining and coal gasification techniques. In the
drilling of other bore holes into or through the earth, such as
oil or gas wells, it is sometimes necessary or desirable to
enlarge the well bore for a given distance.
Accordingly, hole openers, including expansible drill
bits have evolved. Some of the expansible drill bits have
included a pilot bit in combination with expansible cutters to
drill a pilot hole and also drill out an enlarged chamber. When
drilling with liquid or mud as a drilling fluid to cool the cut-
ters and flush cuttings from the bore hole, it is customary to
circulate the drilling fluid down a length of drill pipe or
tubular conduit, and the fluid returns through the annulus
between the pipe and the bore hole to flush cuttings from the
hole.
In the case of certain bore hole drilling operations,
both in the formation of blast holes and other bore holes, air
or gas is employed as the drilling fluid to cool the cutters and
remove the cuttings from the bore hole. However the effective
removal of cuttings by air requires a relatively high bailing
velocity as compared with liquid drilling fluids. According to
most authorities, air bailing velocities on the order of five
thousand feet per minute of air are re~uired.
When large bore holes are being drilled, using air as
a drilling fluid, therefore, it will be appreciated that such
bailing velocity of the air through the annulus, outside the
drill pipe may be difficult to accomplish or may reauire com-
pressor capacity at the dri'ling rig in excess of that available
or economically practical to obtain. Moreover, even if added
compressors can supply sufficient air to cause the effective
bailing of cuttings through the bore hole annulus, the velocity
of air returning to the reduced annular space above the enlarged
chamber or bore hole would be ojectionably noisy at the outlet,
and the abrasive nature of the cuttings and dust would be damag-
ing to the drill pipe and the integrity of the enlarged bore
hole. In the case of blast holes, particularly, erosion of the
shoulder at the beginning of the enlarged chamber is undesirable
in that the blasting effectiveness is reduced.
So called reverse circulation of drilling fluid has been
resorted to in an effort to supply drilling fluid at adequate
bailing velocity. The reverse circulation involves circulating
air downwardly through the bore hole annulus and upwardly through
the bit and drill pipe, the velocity in the relativelt~ small
bore of the pipe being quite high due to the small cross-
sectional area of the flow passage~
In addition, circulation of the drilling fluid through
so-called dual concentricpipe strings has been resorted to in
some drilling operations. Dual concentric pipe strings involve
providing concentric inner and outer pipes having connections
which provide flow passages establishing communication with the
annular space between the pipe sections, as well as through
the central pipe bore. However, providing a good seal at the
pipe connections and adequate wrench areas or tool slots for
making up and breaking out the connections, while maintaining
adequ,ate flow area, are problems in dual concentric drill pipe.
When expansible, pivoted cutter supporting arms on drill
bits are actuated outwardly by air pressure to initiate an
enlarged bore hole, the flow of air to the cutters, in air
cooled cutter bits, may be so great that inadequate pressure is
present to effect expansion of the cutters in a reasonably short
period of drilling, so that a long tapered side wall is formed
on which the back or outer surfaces of the pivoted cutter arms
may drag and wear. Thus, it is desirable that the expansive
force be maintained on the arms which carry the cutters, while
not depriving the cutters of sufficient cooling air during the
early stages of bore hole enlargement.
Air cooled expansible cutters currently available are
both complicated in the structure permitting the flow of air
through the cutter support arms and inefficient in terms of the
cleaning and cooling effect of the air on the cutter elements.
In the formation of blast holes in mining or quarrying
operations, it has been found that a two-pass method of first
drilling a pilot hole with a first drill bit and drilling string,
and then, in a second pass, enlarging the hole with an ~xpansi-
ble bit run on a second drill string, produces a superior blast
hole shape, if the bore hole enlargement is continued subs-
tantially to the bottom of the pilot hole. Since the annular bore
hole space outside the drill string, when drilling the pilot
hole is not large in cross-sectional flow area, the drilling
fluid or air can be normally circulated down the drill string
and up the annulus, and the bailing ~elocity of the fluid or
air in the annulus may be adequate. Thereafter, however, when
the second, hole enlarging pass is being made, the enlargement
of the bore hole may so increase the annular flow area that the
necessary air bailing velocity may not be obtained with existing
compressors. If an expansible bit is used which is expanded
by reverse circulation, even through a dual concentric pipe
string, a ~ifferent set up of equipment at the rig is necessary
to supply the air through the annulus. On the other hand, the
pilot bit cou]d be used Oll the dual pipe with the dual pipe rig
equipment which supplies air through the dual pipe annulus.
Thus, two separate pipe strings for the pilot drilling pass and
the enlarying drilling pass would be required in the case of
existing equipment.
When forming blast holes by the two-pass method to provide
a more-or-less flat bottomed enlarged chamber, as more particu-
lar]y disclosed in the ~nited States Patent 4 ,189 ~185, i .
issued February 19, 1980 to A.W. Kammerer et al, it is
desirable that the bottom of the hole be relatively free from
cuttings all~ accumlllated dust at the conc]usion of the drilling.
Accumulated debris at the bottom of the hole can cushion the
explosive effect and interfere with bench removal or effective
fragmentation. Ilowever, residual cuttings and dust in the hole
have contir~ued to be a problem.
The present invention relates to improved reverse circu-
lation, pilot hole and enlaryed hole drilling which obviates the
problems referred to above.
More particularly, the present invention provides for
forming enlarged bore holes or blast holes utilizing a two-pass
method and reverse circulation through a dual concentric pipe
string during the bore hole enlargement drillinc3, the dual
concentric pipe string also being utilized during the drilling
of the pilot hole.
~ dual concentric pipe string is provided, according to
the invention, macle up in lengths of pi~)e havir-1c3 threaded l~in an(l
-4-
box ends providing sealed connections or joints between the
lengths of pipe. One length of pipe utilized in the pipe
string during drilling of the pilot hole has a cross-over
structure which blanks off the center pipe above the pilot bit
and allows air flow from between the center and outer pipes to
the air passage of the pilot bits, so that return flow of air
is upwardly in the annulus between the pipe string and the bore
hole wall. A sealed swivel structure provides for the supply
of air to the space between the center pipe and the outer pipe,
from a source of drilling air, and includes a rotary mandrel
connected to the pipe string by one of the sealed dual pipe
joints.
Also, in accordance with the invention, the expansible
bit for enlarging the bore hole has a piston and cylinder
structure to which air is supplied from the space between the
center and outer pipes for effecting outward expansion of cutter
arms in response to longitudinal movement of an outer arm support
with respect to an inner body and rotary drive mandrel for the
arm support. During initial movement of the arm support and
expansion of the cutter arms, a relatively small amount of the
total air pressure is allowed to be bled off from the piston and
cylinder structure and to flow through passages in the arm
supports and to the cutters to cool the cutters; while the
greater portion of the air pressure is maintained in the piston
and cylinder structure to effect expansion of the cutters. When
the cutters are in fully expanded condition, they are mechani-
cally locked expanded and additional passage means are opened to
allow a greater volume of the air to pass through the piston and
cylinder means and flow through the cutters. Still further
passage means in the cutter support are also opened to allow air
3;3
from the piston and cylinder structure to flow through the
outer cutter support body to no~zles which are directed towards
the cutters, to blow cutting therefrom and assist in cooling the
cutters, while the cutters are fully expanded and mechanically
locked in the expanded condition.
A simple structure is provided for conducting air from
the piston and cylinder structure to the cutters, through the
cutter support body and arms. The arms have fluid passages con-
nected with additional passages in the support body by a flexible
connector conduits enabling pivotal movement of the arms. The
passages in the arms lead to bearing supports for roller cutters
revolvable on the supports, and the air flows through the bearings
and bearing races.
In order to assure adequate return air flow through the
center pipe during the enlargement of the bore hole, means are
provided to induce such return air flow. More particularly,
venturi means are associated with the discharge line or conduit
from the top drive unit which rotates the drill pipe. The venturi
means has an air inlet to which air can be supplied independently
of the air supplied to the pipe string. Thus, efffective bailing
or removal of cuttings is assured. In addition, the venturi
means is preferably capable of inducing continued air flow
through the center pipe to remove residual cuttings and dust
which settle in the hole when the drilling of the enlargement is
complete. Such residual material can be agitated by continued
rotation of the expanded cutters, but without applying thrust to
the drill pipe.
This invention possesses many other advantages and has
other purposes which may be made more clearly apparent from a
consideration of a form and method embodying the invention. The
3~3
form and method are shown and described in the present specifi-
cation in connection with the drawings accompanying and consti-
tuting a part thereof. Such form and method will now be
described in detail, for the purpose of illustrating the general
principles of the invention; but it is to be understood that
such detailed description is not to be taken in a limiting sense.
Referring to the drawings: Figs. la and lb, together,
constitute a view diagrammatically showing the drilling of a
pilot bore hole into earth formation, utilizing the dual drill
pipe string of the invention, Fig. lb being a downward continua-
tion of Fig. la;
Figs. 2a and 2b, together, constitute a view diagramma-
tically showing the enlargement of the pilot bore hole of Figs.
la and lb utilizing the expansible bit of the invention and
reverse circulation through the dual pipe string, Fig. 2b being
a downward continuation of Fig 2a.
Figs. 3a and 3b, together, constitute an enlarged longi-
tudinal section through the swivel structure, Fig 3b being a
downward continuation of Fig. 3a;
Fig. 3c is a fragmentary vertical section on the line
3c-3c of Fig. 3b;
Fig. 4 is a transverse section through the swivel, as
taken on the line 4~4 of Fig. 3a;
Figs. 5a and 5b, together, constitute an enlarged vertical
section, as taken on the line 5-5 of Fig. 1, showing a typical
dual pipe joint, Fig. 5b being a downward continuation of Fig.
5a;
Fig. 6 is a transverse section as taken on the line 6-6
of Fig. 5a;
--7--
3~
Fig. 7 is a transverse section as taken on line 7-7 of
Fig. 5b;
Figs. 8a and 8b, together, constitute an enlarged vertical
section, as taken on the line 8-8 of Fig. 1, showing the cross-
over unit in the dual pipe string used to drill the pilot bore
hole; Fig. 8b being a downward continuation of Fig. ga;
Fig. 9 is a transverse section as taken on the line ~-9
of Fig 8b;
Figs. lOa, lOb and lOc, together, constitute a vertical
section, as taken on the line 10-10 of Fig. 2, showing the expan-
sible bit used to enlarge the bore hole with the cutters in
retracted condition, Figs. lOb and lOc being successive downward
continuations of Fig. lOa;
Fig. 11 is a transverse section as taken on the line 11-11
of Fig. lOb;
Fig. 12 is a transverse section as taken on the line 12-12
of Fig. lOb;
Fig. 13 is a transverse section as taken on the line 13-13
of Fig. lOc;
Fig. 14 is a transverse section as taken on the line 14-14
of Fig. lOc;
Figs. 15a and 15b, together, constitute a vertical section
corresponding to Figs. lOb and lOc, but showing the cutters
expandea as in Fig. 2;
Fig. 16 is a bottom plan of the expansible bit, with the
cutters expanded as in Fig. 15b; and
J Fig. 17 is an enlarged section, as taken on the line 17-17
of Fig. 16, showing the details of one of the air cooled cutters.
As seen in the drawings, referring first to Figs.la and
lb, and Figs. 2a and 2b, apparatus is diagrammatically illustrated
for first drilling a pilot bore hole PH (Figs. la and lb) by
drilling through the earth formation F with the usual drill bit
B, secured to the lower end of a string of rotatable drill pipe
P, adapted to be rotated by a suitable rotary drive unit D, where-
by the cutters C on the bit B progressively drill the bore or
pilot hole PH as the drill pipe P is rotated, and drilling fluid
is supplied through a swivel S from a suitable source of drilling
fluid, such as a compressor for air in the case of drilling with
air, via a supply conduit 10. As illustrated, the drill pipe
string P is a dual concentric drill pipe having an inner pipe
IP and an outer pipe OP made up in appropriate lengths or sections
secured together at joints J and defining an annular sp~ce A
therebetween communicating through the respective joints, where-
by drilling fluid or air supplied through the swivel S, from the
pipe 10 through the annular space A to a crossover unit CO in
which the annular space A communicates through lateral passages
11 with a central bore 12 at the lower end of the crossover unit.
The bit B is connected to the lower end of the crossover unit
by the usual threaded connection 13 and has a central passage 14
therethrough, through which the drilling fluid or air passes
from the crossover passage 12, exiting into the bore hole PH
through the bit B and returning to the surface of the earth or
to the starting end of the bore hole through the annular space
15 defined between the bore hole wall and the drill pipe string
P. The flow of the drilling fluid or air is operative to cool
the cutters C of the bit B and to flush or bail cuttings from
the bore hole as the drilling progresses.
It is generally known that the velocity of air upwardly
through the annular space 15 between the drill pipe and the bore
hole wall must be on the order of 5000 feet per minute in order
3~
to bail the cuttings from the bore hole. When as shown in
Fig. lb, the gauge of the bit B is only slightly larger than the
diameter of the drill pipe string P, the annular cross-sectional
area of the annulus 15 can enable the air to flow with sufficient
velocity; for example, if air is supplied from a compressor
through the annulus A of the drill pipe string at 1300 SCFM, the
diameter of the drill pipe is 5 3/4" and the gauge of the bit
is 7 7/8", and the bore hole is fairly regular, having no large
cavities or enlargements therein, the bailing velocity of the
air returning through the annulus 15 will be on the order of in
excess of 8000' per minute, or well in excess of the minimum
velocity required for removing the cuttings. With this in mind,
the drilling of bore holes using air, generically including other
gas, as the drilling fluid supplied through the dril] pipe string,
either of the ordinary type or of the dual concentric type, has
been widely used as a drilling fluid in drilling bcre holes
into various earth formations, including bore holes for blasting
or other mining operations, as well as in the drilling of well
bores.
As seen in Figs. 2a and 2b, the same drill pipe string P,
but without the crossover structure CO, has been cornected to a
hole opener or bore hole enlarging bit EB of the expansible
cutter type, having pivoted cutter supporting arms 16 provided
with the cutters C at the lower free ends thereof, adapted to
form the enlarged bore hole or chamber EH, as the expansible
cutters are swung outwardly and the drilliny progresses. If
air were to be supplied through the swivel S to the drill pipe
string P in the same manner as described with respect to Figs.
la and lb in an effort to flush or bail the cuttlngs from the
enlarged bore hole or chamber EH, the bailing velocity would be
83~
below the minimum value required. For example, if the enlarged
bore hole EH is 13" in diameter, and drilling air is supplied
at 1300 SCFM, the air velocity within the enlarged bore hole
would only be slightly more than 1700' per minute. In accordance
with the present invention however, the air is supplied through
the swivel S to the annulus A between the inner and outer pipes
IP and OP, as shown by the arrows, flowing downwardly into the
bore hole, and then entering the center pipe IP and flowing
upwardly therethrough, exiting from the top thereof. If it is
assumed that the bore of the inside pipe is 2" in diameter, and
all of the air returned to the surface through the 2" bore,
supplied through the annulus A at 1300 SCFM, then the bailing
velocity would be on the order of 60,000' per minute. Thus, if
merely 10% of the air entering the bore hole returns through the
inner pipe, the bailing velocity would still be on the order of
6000' per minute, which is in excesss of the minimum velocity
required to bail the cuttings.
As is known, baffles between the pipe string P and the wall
of the bore hole PH may be employed to assure adequate flow of
air up the centre of the drill pipe string. However, in accor-
dance with the present invention, as seen in ~ig. 2a, the flow
of air up through the center pipe is enhanced by the provision
of means V for drawing air through the inner pipe IP. The drive
unit D is shown diagrammatically as having an inner drive pipe
17 driven by gearing 18 which is powered by suitable motors, such
as hydraulic motors M. Fluid and cuttings flow upwardly through
the drive pipe 17 into a discharge chamber 17a in the drive unit
housing, the pipe 17 having a packing 17b engaged therewith to
prevent entry o~ dust into the drive unit housing. An outlet
connection 19 is connected to the housing by fasteners l9a and
33
establishes a flow path from the housing chamber 17a to a
discharge hose l9b.
The venturi means V is associated with the discharge hose
19b so as to induce flow through the hose and thus induce flow
upwardly through the center of the drill string. The venturi
includes a housing l9c installed in the discharge hose 19b and
having a flow passage l9d therethrough. A flange l9e on the
housing l9c has an annular space or passage l9f to which air is
supplied by an inlet conduit l9g. An annular gap l9h opens from
the annular passage l9f into the flow passage l9d upstream of
the gap, thereby inducing fluid flow from the bore hole upwardly
through the inner drill pipe and through the discharge hose, as
air is supplied through the swivel S and flows down the annulus
A between the inner and outer pipes and enters the bore hole
through the bit.
The venturi or vacuum producing means V provides a
further advantage after the completion of the enlargement of the
bore hole, when the supply of drilling air is discontinued. When
the drilling operation is concluded, the bore hole will contain
a quantity of cuttings and dust which have been lifted within
the annular space within the bore hole outside of the drill pipe
and which will settle to the bottom of the hole. The continued
application of air tG the venturi will induce flow through the
discharge conduit which continues to draw air up the center pipe
and wi~ continue to lift the cuttings from the bottom of the bore
in a vacuuming operation. During the vacuuming operation, the
drill pipe P can be rotated to cause the cutters on the bit to
agitate the cut~ings at the bottom of the hole.
Referring to Figs. 3a, 3b, 3c and 4, the swivel structure
S is shown in greater detail. Internally, the swivel structure
. ,~
3~
includes an elongated body or mandrel 20 having a central flow
passage 21 therethrough. At its upper end the body 20 has an
externally threaded pin 22 threaded into an internally threaded
box 23 of the rotary drive member 17, which is adapted, as des-
cribed above, to be rotated by drive unit D. The rotary drive
member 17 has a central passage 25 therethrough which communicates
with the swivel passage 21 and with the discharge conduit and
venturi means V. At its lower end, the swivel body or mandrel
B 20 has an internally threaded box section ~ connected to an
externally threaded pin 27 forming a joing J therewith.
A tubular outer body section 28 is disposed about the
body of mandrel 20 and welded thereto at appropriate locations to
rigidly unite the inner and outer body sections together. As
shown, the outer body 28 has an upper weld 29 securing it to the
upper portion of the inner body section, and a suitable number of
longitudinally and circumferentially spaced welds 30 formed in
drilled holes in the outer body section are also provided to
secure the body sections together. Prior to assembly of the
outer body section 28 on the inner body, the inner body is
provided with a number of circumferentially spaced longitudinally
extended milled slots 31 which communicate with further down-
wardly extending and circumferentially spaced slots 32 (Fig.3c),
through which slots air is adapted to flow downwardly between
the mandrel body sections. The slots 32, as seen in Fig. 3c,
are narrower than the slots 31 and 33, but of gr~ater depth so
as to have approximately the same effective air flow areas.
Reduction in the width of the slots 32 enables the formation in
the swivel body at a number of circumferentially spaced locations,
of outwardly opening wrench slots 34 which extend longitudinally
~n nf the bod~7 and provide a downwardly facing shoulder 35,
~lP~3~
whereby a vertical supporting tool and holding tool can be
applied to the body by the drilling rig, as is also well known.
The wrench slots 34 are partially formed by external slots 36
formed in the exterior of the inner body section 20, and pre-
ferably a bead of weld 37 is formed about the interface of the
body parts within the wrench slot 34. Disposed about the rotat-
able swivel body structure is an outer swivel housing structure
38, adapted to be held stationary in an appropriate suppo~ting
arrangement which allows downward movement of the swivel assembly
during the drilling operation. The supporting arrangement is
not illustrated herein since it is not germane to the present
invention and various supporting arrangements can be utilized,
as well ~nown in the use of apparatus of the type here involved.
More particularly, the outer stationary swivel structure
38 comprises a central annular section 39 disposed about the
rotatable internal hody structure and carrying suitable internal
side ring seals 40 and 41 in axially spaced relation. The seals
40 and 41 are preferably elastomer seals and are adapted to
confine the air from the air inlet conduit 10 against leakage
from the swivel assembly. As seen in Fig. 3a, the conduit 10
opens into an annular space 42 defined by companion annular
grooves 43 and 44 in opposed relation in the cylindrical walls
of the swivel member 39 and outer body section 28 of the swivel
mandrel. Leading between the annulus 42 and the respective
longitudinally extended flow passages or slots 31 in the mandrel
is a number of circumferentially spaced radial ports 45. Upper
bearing means 46 and lower bearing means 47 rotatably support
the inner mandrel structure within the outer swivel structure.
The upper bearing means 46 includes an inner bearing race 48 r
seating on a shoulder 49 provided on the outer mandrel body
-14-
8~3
section 28and having an inwardly and upwardly inclined race or
surface 50 engaged by bearing elements or rollers 51. An outer
race member 51' is engaged by the bearing rollers 51 and engages
in a seat 52 provided within a bearing retainer and sealing .
sleeve 53. This sleeve 53 is threaded at 54 onto an upwardly ex-
tended annular flange 55 provided on the central swivel housing
member 39 and has an upper circumferentially extended and inwardly
projecting flange 55' which carries an internal sealing ring
structure 56 slideably and sealingly engaging with the outer
cylindrical surface of the mandrel body section 20, so as to pro-
tect the bearing means 46 from erosive dust and dirt. Corres-
pondingly, the lower bearing means 47 has an inner race 57
seating in a seat 58 provided on the mandrel body structure and
having a downwardly and inwardly inclined surface or raceway 59
engaged by bearing elements or rollers 60 which also engage the
opposing upwa~dly and outwardly inclined raceway 61 of an outer
bearing race 62 disposed in a seat 63, which is provided by a
lower bearing retainer sleeve 64. This sleeve 64 is threadedly
connected at 65 to a downwardly extended annular flange 66
provided on the mandrel housing central member 39 and has a
circumferentially extended and inwardly projecting lower flange
67, which carries an internal seal assembly 68 slideably and
sealingly engaging with the outer cylindrical surface of the
mandrel structure to prevent the entrance of foreign matter into
the lower bearing assembly 47. It will be seen that the outer
swivel housing structure 38 can be easily assembled about the
swivel mandrel structure and disassembled for service or repair
by threadedly disconnecting the respective bearing retainer
sleeves 53 and 64 form the central housing member 39. In addi-
tion, when the bearing retainers 53 and 64 are removed, the
-15-
33
central housing member 39 can be moved axially upwardly from
the end of the swivel mandrel to allow service and replacement
of the seal rings 40 and 41.
Referring to Figs. Sa and 5b, as well as to the sectional
views 6 and 7, a typical joint J is illustrated. Each joint J
includes a box end 70 and a pin end 71. The box end 70 comprises
an inner tubular member 72 having a suitable number of circum-
ferentially spaced and longitudinally extended flow passages 73
milled therein and having a central flow passage 74 therethrough.
At its lower end, the member 72 has a downwardly and outwardly
tapered internal thread 75 adapted to receive the complimental
external thread 76 on the pin section. At its upper end, the
box member 72 has an annular seat 77 circumscribing the flow
passage 74 and receiving a downwardly extended cylindrical end
portion 78 of an elongated pipe section 79, which is welded to
the box member 72 as by a circum~erentially continuous weld 80.
~isposed about the pipe 79 and defining therewith the annular
space A is an outer elongated pipe 81 which is welded by a
suitable number of circumferentially spaced welds 82 in radial
openings 83 to the upper end of the box body member 72. Also
welded to the box body member 72 is a downwardly extended
connector sleeve 84 which extends downwardly about the box body
72 and provides a downwardly facing end or shoulder 85 pro-
jecting downwardly below the lower end 86 of the threaded box
section. The sleeve 84 is welded to the box body section 72 by
means of a suitable number of circumferentially spaced welds 87
provided in radial openings 88 in the sleeve 84. In addition,
a circumferentially continuous weld 89 is provided between the
opposing ends of the upper pipe section 81 and the downwardly
extended sleeve 84. The outer connector sleeve 84 and the
-16-
833
inner box member 72 are also united adjacent their lower ends by t
a weld 90 which extends circumferentially at the juncture of the
lower end of the inn,er body 72 with the internal periphery of the
connector sleeve above the lower end shoulder 85. As seen in
Fig. 5b, the upper end of each length of pipe, having the pin
end 71 of the respective joints J, has the external thread 76 on
the upwardly and inwardly tapered pin section 91 which is provided
on a pin body section 92 having a longitudinally extended bore
or fluid passage 93 therethrough adapted to be aligned with the
passage 74 through the box end 70 of the coupling. At its lower
end, the pin body section 92 has an internal annular seat 94
receiving an upwardly extended cylindrical end section 95 of the
center pipe 79 which is welded to the body section 92 by a circum-
ferentially conti.nuous weld 96. Formed in the outer periphery
of the pin body section 92, adjacent the upper end thereof, is
a number of circumferentially spaced longitudinally extended
slots 97 which communicate with relatively narrower but deeper
longitudinally extended slots 98, which at their lower ends
communicate with further longitudinally extended slots 99. The
slots 97 communicate with an annular space 100 between the lower
extremity of the box end 86 and an upwardly facing surface or
shoulder 101 at the upper end of an outer pin connector sleeve
102. The lower slots 99 communicate with the annular space A
between the lower pipe 81 and the inner pipe 79 of the subjacent
unit. As in the case of the slots 32 and 33 described above,
the cross-sectional area of the slots 97 and 99, by reason of
their relatively greater circumferential extent than the narrower
slots 98, have substantially the same cross-sectional air flow
area as the slots 98. The outerpin sleeve 102 is welded to the
3~ inne~ pin body section 92 by a suitable number of circumferentially
_ 7 7 _
13
spaced welds 103 formed in radial openings 10~ in the sleeve
102, as well as by a weld 105 formed at the upper end of the
sleeve 102 and the upper outer edge of the pin body 92.
As seen in Fig. 7, the relatively narrow circumferentially
spaced slots 98 provide a substantial segment of the body 92
wherein the circumferentially spaced or diametrically opposed
wrench slots 106 can be formed, these slots 106 extending longi-
tudinally and circumferentially to provide opposed longitudinally
extended shoulders 107 and a downwardly facing horizontal face
108 engageable with the usual holding and supporting members of
the drilling rig. With the pin end held by the projections
provided on the rig and engaged in the wrench slots, the super-
jacent pipe length can be rotated by the rig to make up the
threaded connection between the pin and the box.
Referring to Figs. 8a and 8b, the crossover sub or
assembly CO is illustrated in detail. The assembly comprises an
elongated center section having a flow passage 110 extending
therethrough and including an upper inner body section 111 having
a threaded pin end 112 engaged in the box thread 75 at the lower
end of the pipe section thereabove. At its lower end, the inner
body member 111 has an annular seat 113 receiving the end pro-
jection 114 of a lower, elongated crosso~er body section 115,
welded to the body section 111 by a circumferentially continuous
weld 116. The upper body section 111 has elongated slots 117
milled therein, opening at their lower ends into the annular
space A between the inner body section 115 and the outer tubular
body 118, which is welded at 119 to the upper, outer body
section 120 which provides the upwardly facing shoulder 121
engageable with the downwardly facing shoulder 85 of the upper
pipe section, when the connection is threaded together. Also,
833
as previously described, the pin 112 carries in its upper end
surface an annular resiliently deformable or elastomeric seal
ring 122 which prevents air flow from the annulus A into the
central passage through the assembly. The upper, outer body
section 120 is welded to the inner body section 111 by a suitable
number of welds 123 formed in holes 124 in the outer body
section, and the lower outer body section 118 is also welded to
the inner upper body section 111 by a suitable number of welds
125 formed in holes 126 in the body section 118 below the weld 119
At the lower end of the crossover assembly CO, the inner
tubular body member 115 and the outer tubular body member 118
are joined to a crossover and connector member 127 which has an
internally threaded box 128 connected to the externally threaded
pin 129 of the bit B. The crossover and connector member 127
has a cylindrical body 130 providing an annular seat 131 which
receives a downwardly extended cylindrical end portion 132 of the
inner body section 115, the two parts being welded together by
circumferentially continuous weld 133. It will be seen that
the connector body 130 blanks off the lower end of the fluid
passage 110 in the center of the upper body section. The outer
tubular body 118 is rigidly connected to the crossover and
connector body 127 by a number of circumferentially spaced welds
134 formed in hole 135 in the portion of the body 118 which
surrounds the cylindrical crossover body 130. Another circum-
fentially continuous weld 136 is provided between the lower end
of the body section 118 and the crossover connector 127.
A number of circumferentially spaced elongated milled
slots 137 in the side of the crossover body 130 communicate with
the annular space A and with a number of radial ports 139 formed
in the crossover body 130 and extending between the slots 137 and
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.833
a central bore 140 in the connector body 130. The bore 140 opens
downwardly into the central flow passage 141 through the bit B,
whereby air flowing downwardly through the annular space A finds
access to the bit B and discharges into the bore hole, as pre-
viously described with respect to Fig. la.
Referring to Figs. lOa through lOc, the expansible cutter
hole opener or hole enlarging bit of the invention is shown in
detail. The bit EB includes an elongated tubular body 150 having
an upper pin end 151 threadedly engaged in the thread 75 at the
lower end of a length of the drill pipe P and shouldering at 152
with the lower end of the drill pipe section, the pin 151 carry-
ing at its upper end an elastomeric or resilient seal ring 153
engagable within the box 70 to provide a seal between the outer
flow path and the inner flcw passage 154 which extends through
the body of the hole opening bit.
Extending along the bit body 150 in circumferentially
spaced locations is a number of elongated milled slots 155 which
communicate through the connection at the upper end of the body
with the annulus of the drill pipe string, the outer body sleeve
or member 156 of the bit body being welded at a number of cir-
cumferentially spaced locations by welds 147 formed in holes
148 in the body member 156 in angularly spaced relation to the
slots 155.
At the lower end, the fluid passages 155 communicate
through lateral openings 157 (Fig. 11) in the outer body member
156 with an annular piston chamber 158 provided by piston and
cylinder means 159. This piston and cylinder means 159 is
adapted to longitudinally shift an outer cutter carrying support
section 160 of the bit upwardly with respect to an inner drive
or mandrel section 161 of the bit, between the positions shown
--20--
3~
in Figs. lOb and lOc, in which the cutter arms 16 are retracted,
and in Figs. 15a and 15b, in which the cutter arms 16 are
expanded.
The outer, cutter arms supporting structure 160 comprises
a tubular member 162 having at circumferentially spaced locations
elongated fluid passages or slots 163 milled therein and then
closed by elongated closure strips 164 welded into an elongated
seat 165. At alternate angularly spaced locations about the
member 162 are additional passage ways are slots 166 which are
somewhat shorter than the slots 163 and which are closed by
elongated closure strips 167 welded in seats 167' in the member
162. As wi~ be described hereinafter, the passage ways 163 are
adapted to supply air to the cutters C on the cutter arms 16, and
the passages 166 communicate with passages 168 in the lower end
section 169 of the outer body member 162, these passages 168
leading to nozzles 170 which are carried in the lower end of the
body and are directed towards the bits' cutters, whereby the air
discharging from the nozzles is caused to blow over the cutters
to remove cuttings therefrom and assist in maintaining the bit
in a cool operatin~ condition.
Carried by the lower end section 16g of the body member
162 in a plurality of circumferentially spaced elongated slots
171 are the respective cutter support arms 16. Pivot pins 172
éxtend through the upper ends 173 of the cutter arms 16 and into
aligned bores 174 at opposite sides of the slots. The pins
engage at one end with a stop 175 and are retained in place by
suitable screw members 176 threaded into the body as seen in
Fig. 14.
As previously indicated, air from passages 163 in the
body member 162 is adapted to be directed to the cutters C.
-21-
33
Thus, the passages 163, at the lower ends, open into a bore
177, and a flexible, preferably metallic, fluid connector 178
has a fitting 179 connected in the bore 177 and another fitting
180 which communicates with an elongated passage 181 formed in
S the bit support arm 16. In the illustrated embodiment, the
bit ~rm 16 is a two part structure, including the pivot end 16a
and the cutter support end 16b joined together by a weld 16c with
a tubular insert 16d providing for continuity of the fluid
passage 181. Air supplied to the passages 181 is adapted to cool
the cutters C in a manner to be describee below.
The inner body or drive member 161 extends reciprocably
within the outer member 162 and has at its lower end a tubular
member 182 having a head 183 disposed in a seat 184 at the lower
end of the body member 161 and retained in place by a suitable
means such as a split retainer ring 185, which is in turn re-
tained in place by balls 186 engaging in opposed arcuate suraces
provided about the outer periphery of the split ring 185 and
about the inner peripheral wall of the seat 184. The tubular
member 182 extends downwardly within the center of the outer body
section 162 and through a bushing 187, which is retained in
place by snap rings 188 within a bore 189 provided in a web 190
at the 1ower end of the outer body member 169. Extending through
the tubular member 182 is a fluid passage 191 which is in communi-
cation with the central passage 154 through the inner bit body
member 161. Since the air flowing through the tubular member
182 is laden with cuttings and abrasive dust, the member 182 is
preferably provided at its lower end with a wear resistant
ring insert 192.
In the operation of the structure to expand the cutter
supporting arms outwardly from the position of Fig. lOc to the
position of Fig. 15b, an outward projection 193 at one side of ~ -
the tubular member 182 is formed to engage a downwardly and
inwardly, arcuately extended camming surface 194 provided on the
inside of the respective support arms 16. At the lower end of
the camming surface 194 is a locking surface 195 which, when the
arm 16 is fully pivotally extended as seen in Fig. 15b is engaged
by the cam member 193 to mech~nically lock the arms in the ~ ~
expanded positions until reverse motion of the bit body members ~ -
occurs. Upon such reverse motion of the bit body sections, a
shoulder 196 projecting outwardly and facing upwardly on the
tubular member 182 is provided for engagement with a downwardly
facing lug or projection 197 upon the upper end 173 of the res~
pective support arm 16, whereby to pivotally shift the support ~ -
arms 16 from the extended position of Fig. 15b back to the
retracted position of Fig. lOc, enabling the bit structure to be
removed from ~he hole on the drill pipe.
As previously indicated, the inner bit body member 161
is a rotary drive member which is adapted to rotatably drive the
outer bit body section 162 in response to rotation of the drill
pipe string, so that the bit cutters are rotated or re~olved
about the axis of the bit. The rotary drive between the bid
body sections is provided as shown in Fig. 13, wherein it will
be seen that at opposite sides of the inner body section 161 are
chordal flats 198 disposed in opposed relation and slidably
engageable with segmental torque transmitting members 199, which
are carried within the outer body member 162 and suitably fixed
in place as by weldments.
AS previously indicated, the piston and cylinder means
159 which form the piston chamber 158 act to move the outer body
structure 160 upwardly with respect to the inner body structure
-23-
.33
161 when the cutter arms 16 are to be extended. Referring to
Fig. lOb, it will be noted that the piston and cylinder structure
comprises an upper annular head 200 secur.ed within the upper end
of the outer body member 162 by means such as retainer screws
201 carried by the body member 162 and extending into an opening
or groove 202 formed about the outer periphery of the head 200.
An external sealing ring 203 is disposed between the body member
162 and the outer periphery of the head 200, and an internal side
ring seal or piston ring 203' is carried by the head and slid-
ably and sealingly engaged with the outer cylindrical surface of
the upper and outer body member 156. Another wiper or resilient
seal 204 is carried by the upper end of the head 200 and
slidably engages the cylindrical outer surface of the body member
156. In addition, a lubricant is adapted to be supplied to an
annular space 205 above the piston ring seal 203' and the wiper
ring seal 204 through a suitable grease fitting 206 to lubricate
the slidable connection between the head 200 and the body member
156. Below the head 200, and carried by the inner body member
161, is another head member or ring 207 disposed about the outer
periphery of the body member 161 and seating on a stop ring 208,
the ring being held in place by means of a number of circum-
ferentially spaced retainer screws 209 threaded into the inner
body member 161. A static seal ring 210 is disposed between the
body member 161 and the inner periphery of the head 207, and a
sliding and resilient ring seal 211 is carried by the head ring
207 adjacent its lower end and slidably and sealingly engaging
within the inner cylindrical surface of the outer body member
162. Another external ring seal 212 is carried by the head ring
207 and slidably engages the inner periphery of the outer body
member 162 at the upper end of the head ring 207. Thus, it will
'1 A
3~
be seen that air supplied through the swivel to the annular
space A between the inner and outer pipe sections can flow
downwardly through the respective joints finding access to the
air passages 155 provided in the bit mandrel. Ports 157 at the
lower end of the passages 155 provide communication between the
passages 155 and the piston chamber 158, so that the pressure of
air in the piston chamber acts upwardly across the annular cross-
sectional area of the head 200 between the outer periphery of
the bit mandrel 156 and the inner periphery of the outer bit
member 162, providing an upward force to lift the outer body
member 162 and consequently the bit support arms 16 upwardly with
respect to the inner body member 161 and the camming member 193
on the mandrel tube 182. Such upward movement causes the pro-
gressive expansion of the bit arms 16 outwardly, as rotation of
the drill pipe causes the cutter C to form the downwardly facing
upper shoulder within the enlarged bore hole EH.
A suitable number of circumferentially spaced small ports
213 communicate between the piston chamber 158 immediately below
the head 200 and the air passages 163 in the outer body member
162, whereby a portion of the air supplied to the piston chamber
finds access to the passages 163, and then through the flexible
connectors 178 to the air passages 181 in the bit arm 16.
Referring to Fig. 17, it will be seen that the cutter
arm passages 181 are adapted tc supply air to the cutters C to
cool the same. The passages 181 communicate via passage 181a with
a bore 181b, and from the bore 181b air can flow through a further
passage 181c, which extends through the journal or mount 220 for
the rotary conical cutter element 221, which carries suitable
hard cutting inserts 222 arranged in an appropria.e cutting
pattern, as is well known. Between the journal or hub 220 of
the cutter and the conical cutter element 221 are suitable
roller bearings 223 engaging opposed parallel bearings surfaces
224 within the conical member 225 on the hub. In addition,
ball bearing elements 226 are disposed between opposed arcuate
seats 227 on the hub and 228 within the conical cutter element
221, these balls being supplied initally through the bore 181b
and serving to rotatably retain the cutter element 221 on the
hub. After the bearing balls 226 are installed, they are retained
in place by a retainer 229 disposed in the bore 181b and pro-
viding an inner arcuate surface 230 corresponding to the surface
227 within the journal, and retainer 229 is then secured in place
as by a weld 231. In addition, an end bearing or sleeve 232
is disposed between the reduced end of the journal 220 and the
end bore within the conical member 221. The air passage 181c
opens through the inner end of the journal 220, so that all of
the air supplied through the passage 181 passes about the bearings
232,226 and 223 as the air exits between the cutter cone and the
journal.
While, as previously indicated, the relatively small
ports 213 leading from the piston chamber 158 to the fluid
passages 163 and thence to the cutters allow sufficient flow to
effectively cool the cutters during the initial hole opening
operation, it is desired that after expansion of the cutters to
the positions of Fig. 15b, where they are mechanically locked in
the outwardly extended position, a large volume of air be
supplied to the cutters to cool them. Accordingly, again re-
ferring to Fig. lOb, it will be seen that additional fluid
ports 213a are proviaed in the body member 162 and communicating
with the air passages 163 therein. These ports 213a are initially
closed by virtue of the lower side ring seal 211 and the upper
,33
side ring seal 212 between the head member or sleeve 207 and
the inner periphery of the body member 162. However, as the
body member 162 moves upwardly, to the position of Fig. 15a,
it will be seen that the relatively larger ports 213a communicate
with the piston chamber 158 after the ports 213a pass above the
upper head seal 212, whereby additional air is supplied to the
passage ways through the cutter supporting arms and to the
cutters.
In addition, it will be seen, again referring to Fig. lOb,
that the body member 162 has additional circumferentially spaced
ports communicating with the passage ways 166 extending there-
through and leading to the nozzles 170 at the low~ end of the
outer bit body sect~on 169. These additional ports 213b are
also initially located between the lower seal 211 and the upper
seal 212 between the body 162 and the head ring 207, so that
communication between these ports 213b and the fluid passage 155
is initially precluded. Here again, however, as the outer body
of the bit moves upwardly and the bit arms 16 are fully expanded,
these additional ports 213b are also in communication with the
piston chamber 158 so that a share of the air supplied to the
piston chamber can now flow to the nozzles which are, as seen in
Fig. 16, dir~cted towards the cutters C so as to create an air
blast againct the cutters to blow cuttings therefrom and also
assist in maintaining the cutters cool.
In the use of the apparatus described above to first form
a pilot hole PH as in Fig. 1 and to form the enlarged bore hole EH,
the components of the apparatus are preferably carried by a drill-
ing rig having a compressor for supplying air to the drilling
operation, suitable supports for the various components so that
they can be made up in a string during the drilling operations,
_'~7--
33
and engaging and holding tools for the respective components so
that they can be torqued together. Initially, the crossover sub
CO is made up together with the usual drilling bit B and the
swivel S, together with an appropriate length of intermediate
dual concentric pipe. Rotation is applied to the pipe string as
the drilling air is supplied to the conduit 10. The air flows
down the annulus A of the pipe string, crossing over through the
crossover to the central bit passage and returns to the surface
through the annulus 15 outside of the drill pipe. This is, except
for the use of the dual concentric pipe and crossover, a fairly
standard bore hole drilling operation which could be conducted
with ordinary drill pipe instead of the dual concentric pipe.
After the pilot hole PH has been drilled to the desired depth,
the drilling string is removed from the bore hole and the bit
and crossover assembly removed. Then the expansible bit EB is
applied to the pipe string and lowered in the bore hole to the
location at which the formation of the enlarged chamber or hole
EH is to commence.
Air is supplied simultaneously to the drilling fluid
conduit 10 as well as to the venturi V, and rotation of the drill
pipe string is effected to commence the cutting action of the
cutter C against the pilot hole wall. The cuttings, together with
the portion of the air circulated to the cutter C through the ex-
pansible arms will reversely flow upwardly through the center pipe
assisted by the induced flow produced by the venturi device V.
Since the flow of drilling air to the cutter C is initially res-
tricted by the relatively small ports 213 communicating between
the cutter expanding piston chamber 158 and the cutters, high air
pressure is available to forcefully move the cutters outwardly
to rapidly undercut the formation, preventing the outer surfaces
-28-
833
1 of the cutter arm 16 from dragging on the formation at the
undercut shoulder. When the expansible cutters are fully
expanded and locked in place by the camming action of the
mandrel on the support arms and more air is allowed to
circulate through the cutters to cool and cleanse them, the
balance of the air is jetted through the nozzles 170 in the
direction of the bits to further blow the bits clean and
further cool them. The drilling operation can then be
continued until, for example, the enlarged hole is drilled
to the same depth as the depth of the original pilot hole,
as in the two pass blast hole forming method of the
above-identified United States patent 4,189,185. Then the
circulation of air through the drill pipe and the
application of drilling thrust can be ceased while the
application of air to the venturi continues. Any cuttings
and dust which have been carried upwardly through the bore
hole annulus in the air which returns to the surface
through the annulus will then settle ~o the bottom of the
bore hole. The continued rotation of the drill pipe can
cause the cutters to agitate the settling dust and
cuttings, and the flow of air downwardly through the
annulus and upwardly through the centre of the drill pipe,
under the influence of the venturi will cacuum the hole
relatively clean.
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