Note: Descriptions are shown in the official language in which they were submitted.
7~
1 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 given depth and enlarge the hole
to form a large chamber for receiving a blas,ting 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 or 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 cutters 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 5,000 feet per minute oE air are
; 30 required.
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1 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 require
compressor capacity at the drilling rig in excess o~ that
available or economically practical to obtain. Moreover,
even if added compressors can supply sufficient air to cause
the effective balling 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
objectionably noisy at the outlet, and the abrasive nature of
the cuttings and dust would be damaging 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 drilllng fluid at
ade~uate bailing velocity. ~he reverse circulation involves
circulating air downwardly through the bore hole annulus and
upwardly through the bit and drill pipe, the velocity in the
relativeLy 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 tnrough
so-called dual concentric pipe strings has been resorted to
; in som~ drilling operations. Dual concentric pipe strings
involve providing concentrlc 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
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1 a good seal at the pipe connections and adequate wrench areas
or tool slots for making up and breaking out the connections,
while maintaining adequate 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 enla~ged 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 staces 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 expansible bit run on a second drill string, produces a
superior blast hole shape, if the bore hole enlargement is
continued substantially to the bottom of the pilot hole.
Since the annular bore hole space outside the drill string,
when drilling the pilot hole is not lar~e in cross-sectional
flow area, the drilling fluid or air can be normally
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1 circulated down the drill string and up the anrlulus, and the
bailing velocity of the fluid or air in the annulus may be
adeguate. 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 exîsting
compressors. If an expansible bit is used which is expanded
by reverse circulation, even through a dual concentric pipe
string, a different set up of equipment at the rig is
necessary to supply the air through the annulus. On the
other hand, the pilot bit could be used on 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 enlarging 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 particularly disclosed in United States patent
4,189,185, issued February 19, 1980 to A.W. Kammerer et al,
it is desirable that the ~ottom of the hole be relatively
free from cuttings and accumulated dust at the conclusion of
the drilling. Accumulated debris at the bottcm of the hole
can cushion the explosive effect and interfere with bench
removal or effective fragmentation. However, residual
cuttings and dust 1n the hole have continued to be a problem.
; The present invention relates to improved reverse
circulation, pilot hole and enlarged 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-
~527~
1 pass method and reverse circulation through a dual concentricpipe string during the bore hole enlargement drilling, the
dual concentric pipe string also being utili~ed during the
drilling of the pilot hole.
A dual concentric pipe string is provided, according to
the invention, made up in lengths of pipe having threaded pin
and box ends providing sealed connections or joints between
the lengths of pipe. One length of pipe utili~ed 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 rotaty mandrel connected to the pipe
string by one of the sealed dual pipe joints.
Also, in accordance with the in-7ention, 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 oi
; cutter arms in response to longitud1nal movement of an outer
arm support with resect to an inner body and rotaty drive
mandrel for the arm support. ~uring initial movement of the
; arm support and expansion of the cutter arms, a relatiely
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 porl:ion of the air
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l pressure is maintained in the piston an~ cylinder structure
to effect expansion of the cutters. When the cutters are in
fully expanded condition, they are mechanically 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 from the piston and cylinder structure to flow through
the outer cutter support body to noz~les 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
connected with additional passages in the support body by a
flexible connector conduit enabling pivotal movement of the
arms. The passages in the arms lead 1:o 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 supplied to the
`- pipe string. Thus, effective bailing or removal of cuttings
is assured. In addition, the venturi means is preferably
capable of inducing continued air flow 1:hrough the center pipe
to remove ~esidual cuttings and dust which settle in the hole
1 when the driling 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 posseses 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 form and method are shown and described in the present
specification in connection with the drawings accompanying
and constituting 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 will be
understood that such detailed description is not to be ta'~en
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
continuation of Fig. la;
Figs. 2a and 2b, together, constitute a vi~w
diagrammatically 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 ~ual pipe
string, Fig. 2b being a downward continuation of Fig 2a.
Figs. 3a and 3b, together, constitute an enlarged
longitudinal seation through the swivel structure, Fig. 3b
being a downward continuation of Fig. 3a;
Fig. 3c i8 a fragmentary vertical section on the line
` 3c-3c of Fig. 3b;
Fig 4 is a transverse section throuah the swivel, as
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1 taken along 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;
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 crossover unit in the dual pipe string used to drill the
pilot bore hole; Fig. 8b being a downward continuation of
Fig. 8a;
Fig. 9 is a transverse section as taken on line 9-9 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
expansible bit used to enlarge the bore hole with the cutters
in retracted condition, Fig. 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;
Fig~. lSa and l5b, together, constitute a vertical
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1 section corresponding to Figs. lOb and lOc, but showing th~
cutters expanded as in Fig. 2;
Fig. 16 is a bottom plan of the expansible bit, with
the cutters expanded as in Fig. 15b; and
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 diagrammatical~y
illustrated for first drilling a pilot bore hole P~l ~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, whereby 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 ~oints J and defining an annular space A
therebetween communicating through the respective joints,
whereby drilling fluid or air supplied through the swivel S,
from the pipe 10 throuyh the annular space A to a crossover
unit CO ln 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 t:hreaded connection
13 and has a central passage 14 therethrough, through which
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1 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 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 the alr
is suppIied from a compressor through the annulus A of the
drill pipe string at 1300 SCFM, the d ameter of the drill
pipe is 5 3/4" and the gauge of the b t 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 m~inimum
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 drill pipe string, either of the ordinary type or of the
dual concentric type, has been ~idely used as a drilling
fluid in drilling bore holes for blasting or other mining
operations, as well as in the drilling of well bore.
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1 As seen in Figs. 2a and 2b, the same drill pipe string
P, but without the crossover structure CO, has been connected
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
drilling 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 cuttings from the enlarged bore hole or
chamber EH, the bailing velocity would be below the minimum
value required. For example, if the enlarged bore hole El~ is
13" in diameter, and drilling air is supplied at 1300 SCFM,
the air velocity within the enlarged bore hole would only be
slight 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 centre 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
dia_eter, and all oE the air returned to the surface through
the 2" bore, sopplied throagh 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 return~ through th~ inner pipe, the bailing velocity
` - would still be on the oxder of 6000' per minute, which is in
excess of the minumum velocity required to bail the cuttings.
As is known, baffles bstween the piE~e string P and the
11 ,
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1 wall of the bore hole PH may be employed to assure adequate
flow of air up the center of the drill pipe string. However,
in accordance with the present invention, as seen in E~ig. 2a,
the flow of air up through the center pipe is enhanced by the
provision of means V for drawiny 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 of
dust into the drive unit housing. An outlet connection 19 is
connected to the housing by fasteners l9a and establishes a
flow path from the housing chamber 17a to a discharge hose
l9b.
The venturi means V is associated with the discharge
hose l9b 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 in-talled in the discharge
hose l9b 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 f:Luid
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
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1 the bore hole, when the supply of drilling air is
discontinued. When the drilling operation is concluded, ~he
- bore hole will contain a quantity of cuttings and dust which
have been lifted within the annular space wthin the bore hole
outside of the drill pipe and which will set-tle to the bottom
of the hole. The continued application of air to the venturi
will induce flow through the discharge conduit which
continues to draw air up the center pipe and will 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
cuttings as 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 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 described 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 20 has an
internally threaded box section 26 connected to an externally
threaded pin 27 forming a joning J therewith.
A tubular outer body section 2~ 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,
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1 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 downwardly 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 greater 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 ~rench slots 34 which extend
longitudinally of the body and provide a downwardly facing
shoulder 35, 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 preferably a bead of weld 37 is formed about
the interface of the body parts within the wrench slot 34.
~Disposed about the rotatable swiveI body structure is an
outer swivel housing structure 38, adapted to be held
stationary in ah appropriate supporting 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 known in the use of apparatus o~ the type here
14
1 involved.
More particularly, the outer stationary swivel
- structure 38 comprises a central annular section 39 disposed
about the rotatable internal body 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 ag'ainst 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 longit`udinally extended flo;~
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 uppe`r bearing means 46 includes an inner bearing race 48
searing on a shoulder 49 provided on the outer mandrel body
section 28 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 ln a seat 52 provided within a bearing retainer
and sealing sleeve 53. This slee~ve 53 is threaded at 54 onto
an upwardly extended 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 slidably
and sealingly engaglng with the outer cylindrical surfac`e of
the mandrel body section 20, so as to protect the bearing
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1 means 46 from erosive dust and dirt. Correspondingly, 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 upwardly 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
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 6~ slidably 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
33 can be easily assemb.led about the'swivel mandrel structure ::
and disass.embled for service or repair by threadedly
disconnecting the respective bearing retainer sleeves 53 and
64 from the central housing member 39. In addition, when the
bearing retainers 53 and 64 are removed, the central housing
member 39 can be moved axially upwardly from the end oE t:he
swivel mandrel to allow service and replacement of the seal
rings 40 and 41.
Referring to Figs. 5a and 5b, as well as to the
- sectlonal views of 6 and 7, a typical jo'int.J is
illustrated.- Each joint J includ'es a box end 70 and a pin
: end 71. The box end 70 comprises an inner tubular member 72
having a'suitable number of circumferentialy spaced and
longitudinally extended flow passages 73 milled therein and
16
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1 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 i~
welded to the box member 72 as by a circumferentially
continuous weld 80. Disposed about the pipé 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 projecting downwardly below the
lower end 86 of the threaded box section. The sleeve 84 is
welded to the box body section 72 by neans of a suitable
number of circumferentially spaced welds 87 pxovided in radial
openings 8~ in the sleeve 84. In addition, a
circumferentially continuous weld 89 is provided between th~
opposing ends of the upper pipe section 81 and the downward]y
extended sleeve 84. The outer connector sleeve 84 and the
inner box member 72 are also united adjacent their lower ends
by a weld 90 which extends circumfexentially at the juncture
- of the lower end of the inner body 72 with the internal
-periphery of the connector sleeve above the lower end
shoulder 85. As seen .n Fig. 5b, the upper end of each
length of pipe, having the pin end 71 of the respective joints
J, hss the external thread 76 on the upwardly and inwardly
17
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1 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 circumferentially continuous weld 96. Formed
in the outer periphery of the pin body section g2, 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 communica'te with further
longitudinally extended slots 99. The slots 97 communicate
with an annualar space'100 between the lower extremity of the
box end 86 and an upwardly faciny 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 exter,t than the
narrower slots 98, have substantially the same
cro'ss-sectional air flow ar,ea as the slots 98. The outerpin
sleeve 102 is welded to the inner pin body section 92 by a
suitable number of circumferentially spaced welds 103 formed
, in radial openings 104 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 circum-
18
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1 ferentially spaced slots 98 provide a substantial segrnent of
the body 92 wherein the circumferentially spaced or
diametrically opposed wrench slots 10~ can be formed, these
slots 106 extending longitudinally 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 superjacent 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 inclucing an upper inner body
section lIl 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 projection 114 of a lower,
elongated crossover body section 115, welded to the body
section 111 by a circumferentially continous weld 116. The
upper body section 111 has elongated slots 11, 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 at the
upper pipe section, wh~n the connection is threaded
together~ Also, as previously described, the pin 112 carries
in its upper end surface an annular resiliently deformable or
19
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1 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
centxe 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 13~ formed in
hole 135 in the portion of the body 118 which surrounds the
cylindrical crossover body 130. Another circumferentially
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 communicates
` I
`~ .with the annular space A and with a num~er of radial ports
139 forned in the crossover body 130 and extending between " .
'
` 20
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1 the slots 137 and 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 s and
discharges into the bore hole, as previously 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 carrying at its uper end an elastomeric
or resilient seal ring 153 engageable within the box 70 to
provide a seal between the outer flow path and the inner flow
passage 154 which extends through the body of the hold
opening bit.
Extending along the bit body 15~) 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 beirg welded at a
number of circumferentially spaced locations by welds 137
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
.
21
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1 carrying support section 160 of the bit upwardly with respect
to an inner drive or mandrel section 161 of the bit, betwsen
the positions shown in Fig. lOb and lOc, in which the cutter
arms 16 are retracted, and in Figs. 15a and lSb, in whihch
the cutter arms 16 are expan~ed.
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 slot.s 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 will 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 passnges 168 leading to
nozzles 170 which are carried in the :Lower end of the body
and directed towards the bits' cutters, whereby the air
discharging from the nozzles is caused to blow over the
cutters to remove cuttings therefrom and assi~t in
maintaining the bit in a cool operating condition.
Carried by-the lower end section 169 of the body member
162 in a pluraity of circumferentially spaced elongated slots
171 are the respectlve cutter support arms 16t Pivot pins
; 172 extend through the upper ends 173 of the cutter arms 16
and into aligned bore holes 174 at opposite sides of the
slots. The pins engage at one end with a stop 175 and are
retained in place by auitable screw members 176 threaded into
22`
. .. . . . . . . . .
: , .. . .
1 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.
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 the bit support arm 16. In the illustraded
embodiment, the bit arm 16 }s a two part structure, including
10 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 described 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 lfil and retained in place
by a suitable means such as a split retainer ring 185, which
20 is in turn retained in place by balls 186 engaging in opposed
arcuate surfaces 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 lower end of
the outer body member 169. Extending through the tubular
member 182 is a fluid passage 191 which is in communication
with the central passage 154 through the inner bit body member
30 161. Since the air flowing through the tubular member 182 is
23
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1 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 ~he arm 16 is fully pivotally
extended as seen in Fig. lSb is engaged by the cam member 193
to mechanically 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
respective support arm 16, whereby to pivotally shift the
support arms 16 from the extended positon of Fig. 15b back to
the retracted position of Fig. lOc, enabling the bit
structure to be removed from the hole on the drill pipe.
As previousIy 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
revolved about the axis of the bit. The rotary drive between
the bit body sections is provided as shown in Fig. 13,
wherein it wili be seen that at opposite sides oE the inner
~0 body section 161 are chordal flats 198 disposed in opposed
24
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1 relation and slidably engageable with segmental torque
transmitting members 199, which are carried within the oucer
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 161 when the cutter arms 16 are to be extended.
Referring to Fig. lCb, it will be noted that the piston and
cylinder structure comprises an upper annular head 200
secured within the upper end of the outer body member 162 by
means such as retained 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 slidably
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 circumferentially
spaced retainer screws 209 threaded lnt~ the inner body
~5~7~ .
1 member 161. A static seal ring 210 is clisposed between the
body member 161 and the inner periphery of the head 207, and
a slicling and resilient ring seal 211 is carried by the head
ring 207 adjacent its lower end and slidably ancl sealingly
engaging within the inner cylindrical surface of the outer
body member 162. ~nother 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 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
mand:rel 156 and the inner periphery o:- the outer bit member
162, providing an upward force to lif~ the outer body member
162 and consequently the bit support arms 16 upvardly with
. respect to the inner body member 161 and the camming member
19~ on the mandrel tube 182. Such upwardly movement causes
the progressive 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 2i3 communicate between the piston chamber 158
: immediately below the head 200 and the air passages 163 in
~ 30 the outer body member 162, whereby a portion of the air
.
26
. ~ , '.
7~
1 supplied to the piston chamber finds access to the passages
163, and then through the fle~ible connectors 178 to the 3ir
passages 181 in the bit arm 16.
Referring to Fig. 17, it will be seen that the cutter
arms passages 181 are adapted to 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 appropriate 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 bearing 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 initially through the bore 1~31b 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
providing an inner arcuate surface 230 corresEonding 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.
~ ~ .
27
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:
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1 When, 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 referring to Fig. lOb, it will be seen
that additional fluid ports 213a are provided in the boby
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 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 21:3a 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 had additional
circumferentially spaced ports communicating with the passage
ways 166 extending therethrough and leading to the nozzles
170 at the lower end of the outer bit body section 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 i55 is lnitially
.
28
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1 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 15~ 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, directed towards the cutters C so as to create an
air blast against the cutters to blow the cuttings therefrom
and also assist in maintaining the cutters cool.
In the use of the apparatus described above to first
form a pilot hole P~ as in Fig. 1 and to form the enlarged
bore hole E~, the components of the apparatus are preferably
carried by a drilling 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, 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 wlth 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 cver
through the crossover to the central bit passage and return
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 ~hich could be conducted with ordinary drill pipe
instead of the dual concentric pipe. After the pilot hole P~
has been drille;d to the desired depth, the drilling string is
removed from the bore hole and the bit and crossover assembly
29
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~25'~7~
1 remov~d. Then the expansible bit EB ls 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
com~ence.
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 expansible 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 restricted 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 of the cutter
arm 16 from dragging on the formation at the undercut
shoulder. When the expansible cutters are fully expanded and
locked in pIace 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
~etted 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 atove-identified United States patent
4,189,285. Then the circulation of air ~:hrough the drill
pipe and the application of drilling thrust can be ceased
.
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1 while the application of air to the venturi continues. Any
cuttings and dust which have been carried upwardly through
the bore hole annulus will then settle to the bottom of the
bore hole. The continued rotation of the drill pipe can
cause the cutters to agitate the settlng dust and cuttings,
and the flow of air downwardly through the annulus and
upwardly through the center of the drill pipe, under the
influence of the venturi will vacuum the hole relatively
clean.
~0
;` 31
