U.S. patent number 3,552,510 [Application Number 04/864,747] was granted by the patent office on 1971-01-05 for apparatus for rotary drilling of wells using casing as the drill pipe.
Invention is credited to Cicero C. Brown.
United States Patent |
3,552,510 |
Brown |
January 5, 1971 |
APPARATUS FOR ROTARY DRILLING OF WELLS USING CASING AS THE DRILL
PIPE
Abstract
A drilling system employing casing as drill pipe and a bit
section which is bodily insertable and removable through the casing
and releasably attachable thereto for rotation with the casing.
Inventors: |
Brown; Cicero C. (Houston,
TX) |
Family
ID: |
25343975 |
Appl.
No.: |
04/864,747 |
Filed: |
October 8, 1969 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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803911 |
Mar 3, 1969 |
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857046 |
Sep 11, 1969 |
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Current U.S.
Class: |
175/261; 175/284;
175/267 |
Current CPC
Class: |
E21B
10/66 (20130101); E21B 7/208 (20130101); E21B
10/345 (20130101) |
Current International
Class: |
E21B
10/26 (20060101); E21B 10/34 (20060101); E21B
7/20 (20060101); E21B 10/00 (20060101); E21B
10/66 (20060101); F21b 009/26 () |
Field of
Search: |
;175/257,258,259,261,263,267,271,285,284 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Leppink; James A.
Parent Case Text
RELATED APPLICATIONS
This application is a continuation-in-part of my copending
applications, Ser. No. 803,911, filed Mar. 3, 1969; and Ser. No.
857,046, filed Sept. 11, 1969.
Claims
I claim:
1. Apparatus for rotary drilling of wells using casing as the drill
pipe, comprising in combination with a string of casing and means
for rotating the same:
a. a bit section bodily insertable and removable through the bore
of the casing;
b. cooperating means on the bit section and the lower end portion
of the casing for landing the bit section therein in nonrotative
relation to the casing;
c. said bit section comprising:
i. a generally tubular body;
ii. radially movable anchor means mounted on the body for
releasably anchoring the body to said casing portion;
iii. a main bit carried by the lower end of the body having an
upwardly extending tubular shank defining a fluid passage through
the bit;
iv. a plurality of angularly space underreamers mounted on the body
above said bit for radial movement between extended and retracted
positions relative to said body;
v. a sleeve member coaxially disposed in said body cooperable with
said anchor means and reciprocable between upper and lower
positions respectively releasing and actuating said anchor
means;
vi. connector means pivotally connecting said sleeve member to said
underreamers reciprocable with said sleeve member between said
positions for simultaneously respectively retracting and extending
said underreamers;
vii. valve means carried by the sleeve member cooperable with said
shank for opening and closing communication between the interior of
said sleeve member and said fluid passage respectively at said
upper and lower positions of said sleeve member; and
vii. releasable means initially securing said sleeve member to said
body in said upper position.
2. In apparatus according to claim 1, wherein said bit section
includes lock means carried by said sleeve member operable in
response to movement of said sleeve member to said lower position
to lock said sleeve member to said body in said lower position.
3. Apparatus according to claim 1 wherein said valve means
comprises a tubular nozzle defining a sleeve valve disposed to
telescopically receive the upper end portion of said shank.
4. Apparatus according to claim 1 including means responsive to
mechanically applied force for releasing said releasable means.
5. Apparatus according to claim 1 including means responsive to
hydrostatic force for releasing and said releasable means.
6. Apparatus according to claim 2 wherein said lock means
includes:
a. radially movable lock elements mounted on said sleeve member for
releasably anchoring the same to said body;
b. a lock sleeve coaxially disposed in the bore of said sleeve
member cooperable with said lock elements and reciprocable between
upper and lower positions respectively releasing and actuating said
lock elements; and
c. means actuable in response to the release of said releasable
means to simultaneously move said lock sleeve to said lower release
position.
7. Apparatus according to claim 1 wherein said cooperating means
includes:
a. a tubular landing shoe secured to the lower end of the casing
string;
b. inwardly projecting male splines in the bore of said shoe;
and
c. spline grooves in the bit body open at their lower ends for
receiving the male spline in response to relative downward movement
of the bit body.
8. Apparatus according to claim 7 wherein said anchor means
includes:
a. a plurality of angularly spaced anchor dogs disposed in openings
in the wall of said body; and
b. an annular anchor groove in the wall of said landing shoe
arranged for anchoring engagement with said dogs.
9. Apparatus according to claim 2 wherein said lock means
includes:
a. a plurality of angularly spaced latching dogs disposed in
openings in the wall of said sleeve member; and
b. an annular latching groove in the interior wall of said body
arranged for latching engagement with said latching dogs.
10. Apparatus according to claim 3 wherein said connector means
includes:
a. a crank arm angularly secured to each underreamer; and
b. a crosshead pin-and-slot connection between the free end of each
crank arm and said nozzle.
11. Apparatus according to claim 6 wherein said lock sleeve
includes:
a. a closure plate across the bore thereof; and
b. an orifice of restricted area through said closure plate.
12. Apparatus according to claim 1 wherein said shank has mounted
through the walls thereof a plurality of jet nozzles arranged to
direct wash fluid toward said underreamers.
Description
In the drilling of wells for oil and gas, for example, by the
rotary method, the drilling is conventionally done by the
employment of relatively small diameter string of drill pipe to
which a bit is secured, the entire string being rotated to drill
the borehole. After a suitable interval has been drilled, sometimes
only a short distance but at other times for the full depth of the
well, casing larger in diameter than the drill pipe will be run
into the borehole and subsequently cemented to seal off the
formations through which the borehole extends. This necessarily
involves the series of operations in which the drill string must be
extended as the hole deepens, as by the addition of sections to the
drill pipe, and also the entire drill string must be withdrawn
whenever it become necessary to replace the bit and then reinsert
it to resume drilling. Thus making of such so-called "round trips"
are not only time-consuming but also create hazards of blowouts and
other undesirable conditions in the well. After the appropriate
drilling of the hole has been completed, the drill string must be
withdrawn and casing run to the desired depth. This, too, may
present hazards because with the drill string out of the well,
control of the well becomes more difficult.
Heretofore numerous efforts have been made to provide a system
employing the casing itself as the drill pipe in order to overcome
some of the hazards enumerated, as well as time loss. However,
these prior efforts have not proven satisfactory for various reason
well-known to those skilled in the art.
The present invention, therefore, is directed to an improved
arrangement by which the casing may be employed as the drilling
string and when used in combination with a retractable or removable
bit section will perform all of the functions of drilling and
casing of a well in a sequence or series of operations which
thereby greatly facilitates drilling operations.
In accordance with the present invention a bit section is provided
which includes both the primary bit and a plurality of radially
extendible and retractable underreamers, the entire bit section
being arranged and constructed to be insertable bodily through the
bore of the casing and moved to the lower end of the casing either
on a wire line or by simply dropping it into the casing, where,
either by gravity alone or supplemented by pumped fluid pressure,
the bit section will be forced to the bottom of the lower end of
the casing string, which is provided with a landing shoe to receive
the bit section. The bit section is provided with anchor or latch
means engageable with appropriate latch grooves or other
anchor-engaging structure in the landing shoe. The latter, in the
illustrative embodiments, includes a number of keys or splines
which are adapted to engage appropriate spline slots or grooves in
the bit section to lock the bit section to the casing against
relative rotation whereby rotation of the casing string will be
effective to rotate the bit for purposes of drilling the well.
The bit section also includes connector means pivotally connected
by crank means the the underreamers which will be actuatable from
the upper end of the casing string by a suitable running tool by
mechanical means or by hydrostatic force, as by drilling fluid
circulating through the system, for purpose of extending or
actuating the underreamers so as the enlarge the bore hole drilled
by the pilot bit sufficiently to allow free downward movement of
the casing behind the bit as the hole is being drilled.
Additionally, the bit section includes a fluid circulation
passageway controlled by a bypass valve means which is normally
open to allow bypassing of fluid while the bit section is being
inserted through the casing into the landing shoe or being
withdrawn therefrom but which is closeable in response to the
movement of the connector means to the underreamer extending
position to direct and confine fluid flow to the bit discharge
passages while drilling. This valve arrangement assures high
velocity wash fluid and minimizes wash fluid requirements.
Novel lock means are provided to lock the underreamers in extended
position contemporaneously with the closing of the bypass valve
means.
To withdraw the bit section a conventional fishing tool or spear is
run into the casing on a wire line connected to anchor-releasing
elements of the bit section, whereby an upward pull applied to the
fishing tool will be effective to retract the underreamers and
release the bit section from the landing shoe to which it has been
anchored. The spacing arrangement between the underreamers and
anchor elements is so designed as to assure that the underreamers
are fully retracted before the bit section is released, thereby
avoiding damage to the underreamers which might otherwise occur if
they were not completely retracted when they pass through the lower
end of the landing shoe.
Other and more specific objects and advantages of this invention
will become more readily apparent from the following detailed
description when read in conjunction with the accompanying drawing
which illustrates a useful embodiment and modification thereof in
accordance with the present invention.
In the drawing:
FIG. 1 is a longitudinal, sectional view showing the bit section
inserted into the landing shoe preparatory to anchoring the bit
section to the landing shoe;
FIG. 2 is a view similar to FIG. 1 showing the bit section anchored
to the landing shoe and with the underreamers in their extended
position;
FIG. 3 is a partial view generally similar to FIG. 2 showing the
bit section in drilling position with the running tool being
withdrawn from the casing;
FIG. 4 is a partial longitudinal view similar to FIG. 3 with the
parts in drilling position and the running tool completely
withdrawn;
FIG. 5 is a view similar to FIG. 4 showing a retrieving tool
inserted in the bit section preparatory to withdrawing the latter
from the landing shoe;
FIG. 6 is a view similar to FIG. 5 showing the parts in released
position for withdrawal by the retrieving tool;
FIG. 7 is a partial longitudinal view generally similar to the
preceding views showing a modifications of the underreamer latch
structure;
FIG. 8 is a longitudinal view of the drilling system in a well bore
showing the casing string with the bit section in place in the
landing shoe and the drive connections at the surface;
FIGS. 9 and 10 are longitudinal quarter-sectional views showing,
respectively, the running and drilling positions of a
hydraulically-actuated modification of the bit section;
FIGS. 11 and 12 are cross-sectional views taken on lines 11-11 and
12-12 respectively, of FIG. 1; and
FIG. 13 is a cross-sectional view taken along line 13-13 of FIG.
2.
Referring to the drawing and considering the first FIG. 8, there is
shown a string of casing C carrying the bit section, designated
generally by the letter B, showing the bit section in place in a
landing shoe 10 connected to the lower end of casing C. At its
upper end casing C is connected to a power sub P which functions to
rotate the casing string during drilling, as will be described.
Power sub P is of the general form and construction disclosed in my
copending application, Ser. No. 736,179, filed June 11, 1968 now
U.S. Pat. No. 3,467,202. A suitable drive connection between the
power sub and the casing is disclosed in my U.S. Pat. No.
3,467,202. Power sub P is suspended from a swivel S carried on
elevators E conventionally employed as part of the drawworks of a
drilling rig. The swivel has a hose connection H by which
conventional drilling fluid is pumped into the drill string of
casing C, thence through the passages in the bit section into the
annulus defined by the bore hole surrounding the drilling string,
the bore hole being designated by the letter W.
Returning now to FIGS. 1 and 2, the landing shoe and bit section B
comprise the basic drilling structure which is secured to the
casing. Shoe 10 is provided with an internally, threaded socket 12
by which it is threadedly secured to the lower end of casing C.
Adjacent its lower end shoe 10 is provided with two or more
angularly spaced cylindrical pins 14 which project a short distance
inwardly of the bore of the shoe and form male splines for purposes
which will be explained shortly.
Bit section B comprises a body 16 having a bore 17, and is
dimensioned to be insertable through the bore of casing C and into
the bore of shoe 10. Body 16 is provided about an intermediate
portion thereof with a plurality of longitudinal keyways or spline
grooves 18 adapted to receive the projecting ends of the pins 14,
whereby body 16 will be locked to shoe 10 against relative rotation
so that rotation of casing C will function to rotate body 16 and
its appurtenances. Spline grooves 18 terminate in upper end walls
19 which form stops for engagement with pins 14 to limit downward
movement of the bit body through shoe 10. An annular seal ring 20
is disposed about the exterior of body 16 above end wall 19 to seal
with the bore wall of shoe 10. At a point above seal 20, body 16 is
provided with a plurality of radial windows or openings 22 in which
are mounted anchor dogs 24 of a generally conventional form which
are adapted when projected outwardly to be received in an annular
anchoring groove 26 formed in the bore wall of shoe 10. The anchor
dogs are positioned in body 16 so that they will be in registration
with groove 26 when body 16 is fully inserted in the shoe with
walls 19 abutting pins 14. The upper end of body 16 is screwed into
a ring 28 which overhangs the upper end of the body to define a
downwardly facing annular shoulder 30 projecting slightly into bore
17.
A setting sleeve 32, having an axial bore 33, is coaxially slidably
disposed in bore 17 and is provided a short distance below its
upper end with an external upwardly facing annular shoulder 34
adapted to abut shoulder 30 in the running position of the tool.
The exterior of setting sleeve 32 is provided with an annular
recess 36 at a point below shoulder 34 adapted to register with
dogs 24 when shoulder 34 abuts shoulder 30, as seen in FIG. 1, in
which position anchor dogs 24 are free to retract from anchor
recess 24. The setting sleeve is also provided with a downwardly
facing internal shoulder 37 which projects into bore 33 at a point
opposite shoulder 34 for purposes to be described subsequently.
At a short distance below recess 36, sleeve 32 is provided with a
plurality of radial windows or openings 38 in which are mounted
lock dogs 40 which at a certain stage of operation of the tool, as
will be described hereinafter, are adapted to be projected into an
annular lock recess 42 provided in the wall of bore 17.
A lock sleeve 44 having an axial bore 45 is coaxially slidably
disposed in bore 33 of the setting sleeve and is provided a short
distance below its upper end with an external upwardly facing
annular shoulder 46 adapted to abut shoulder 37 in the running
position of the tool. Lock sleeve 44 is provided with an external
annular lock recess 48 adjacent its lower end spaced to be in
registration with lock dogs 40 when shoulder 46 is engaged with
shoulder 37 in the running position so as to allow lock dogs 40 to
be in retracted position during running of the tool. Bore 45 of the
lock sleeve is provided with an annular recess 45a intermediate its
ends which is adapted for engagement by retrieving tool as will
appear subsequently.
The lower end of body 16 carries a downwardly facing internally
threaded socket 50 adapted to receive the externally threaded shank
51 of a bit 52 which constitutes the primary or pilot bit and may
be of any conventional design for drilling a bore hole to any
desired nominal diameter determined by the dimensions of the bit.
At a point between the lower ends of splines 18 and socket 50, body
16 is provided with a plurality of longitudinally extending
radially opening slots 53 in which are mounted underreamers 54 of
any suitable and known design mounted to arms 55. The latter are
pivotally mounted on pivot pins 56 which extend transversely of the
respective slots for enabling the underreamers to be angularly
moved as to be radially projected and retracted with respect to the
slots 53. A tubular nozzle 57, having a bore 58 is secured to the
lower end of lock sleeve 32 and projects downwardly centrally of
the tool. The lower end of nozzle 57 defines a sleeve valve 59
having an annular seal ring 60 seated in the bore thereof and
arranged to telescopically receive a tubular extension 61 secured
to the upper end of socket 50, when nozzle 57 is moved downwardly
relative to extension 61, as will be described subsequently. Each
of the underreamer arms 55 is fixedly connected to an angularly
extending crank arm 62 having its free end secured to a crosshead
pin 63 mounted in a crosshead groove 64 formed in the exterior of
nozzle 57 at a point above valve 57 (see FIG. 13). With this
arrangement it will be seen that the movement of nozzle 57
downwardly will act through crank arms 62 to rotate the
underreamers outwardly and upwardly while reverse movement of the
nozzle will act to retract the underreamers. The same movement of
nozzle 57 will simultaneously function to open the valve means
formed by sleeve valve 59 and the upper end of extension 61. The
lower end portion 65 of the latter is conically enlarged to form
the connection to socket 50 and the sloping walls of portion 65 are
provided with a plurality of jet nozzles 66 positioned to direct a
spray of high-pressure wash fluid against the underreamer cutters
when the latter are in extended position (FIG. 2) to clean the
surfaces of the cutters. The lower end of landing shoe 10 is
provided with downwardly tapering slots 11 shaped to cooperate with
arms 55 to limit the outward movement of the underreamers to the
extent desired.
The embodiment illustrated in FIGS. 1 to 6, inclusive, is designed
to be run on a suitable running tool, designated generally by the
letter R, which may, in turn, be run on a conventional sand or wire
line string, or on a string of tubing (not shown). As illustrated
tool T includes a tubular body 70 having a lower end portion 71
designed to be inserted in an annular space between the upper end
portions of setting sleeve 32 and lock sleeve 44 and to seat
against a shoulder 72 in the bore of the setting sleeve. A shear
pin 73 initially secures portion 71 to the upper end portion of
setting sleeve 32. A collar 74 surrounds the exterior of the lower
portion of body 70 and the exterior of the upper end portion of
setting sleeve 32 and is secured to body 70 at a point above shear
pin 73 by means of a second shear pin 75. In this position the
lower end of collar bears against the upper end of body 16 (FIG.
1). The upper end of collar 74 has an inwardly turned lip 76
abuttable by an external shoulder 77 on body 70 at a point slightly
above shear pin 75. A tubular plunger 78 is mounted in the bore of
body 70 and is biased downwardly against the upper end of lock
sleeve 44 by means of a spring 79 held in compression against the
upper end of plunger 78 by means of a backup collar 80 mounted in
the bore of body 70. Backup collar 80 is provided with radially
extending adjustment pins 81 which project through longitudinally
extending slots 82 formed in the upper end of body 70 into an
annular recess 83 formed in the bore of a threaded coupling 84
which serves to connect the running tool to a running connection 85
which forms a part of the running string. Plunger 78 is provided
with an external shoulder 78a with an opposed shoulder 78b in the
bore of body 70 for purposes which will be made apparent
subsequently.
In operation, the bit section secured to running tool R will be
inserted into the upper end of casing C and will be lowered through
the bore of the casing until the bit is brought to a stop by the
engagement of pins 14 with end walls 19 of spline grooves 18. At
this stage, as the bit section is lowered into place, sleeve valve
59 will be separated from the upper end of extension 61, permitting
free bypassing of well bore fluids through the bore of bit section
which might otherwise hinder the movement of the bit section
through the casing. The parts of the bit section will be positioned
as illustrated in FIG. 1 in which the setting sleeve is held in its
retracted position by shear pins 73 and 75. Anchor dogs 24 will
thus be free to retract and are effectively retracted into relief
groove 36, whereby, to allow the free movement of the bit section
through the casing and into landing shoe 10. At the same time, lock
dogs 40 will be in their retracted position effectively holding
lock sleeve 45 in its upper or inactive position, as seen in FIG.
1.
With the bit section thus in place in the landing shoe, upward
jarring force is applied through the running string to break shear
pin 75. Thereupon springs 79 will drive plunger 78 downwardly and
bring shoulders 78 a and 78b into engagement so that the downward
force will be transmitted to setting sleeve 32, as well as to lock
sleeve 44. The resulting downward movement of both sleeves will
drive anchor dogs 24 into anchor groove 26 effectively locking the
bit section to the landing shoe and simultaneously drive lock dogs
40 into locking groove 42, thereby effectively locking the setting
sleeve to bit body 10, being held in this position by the downward
movement of lock sleeve 45 as seen in FIG. 2.
The downward movement of the setting sleeve will also be
transmitted via nozzle 57 through the crosshead pins 63 and crank
arms 62 to underreamer arms 55 to swing the underreamers to their
extended positions.
Running tool R may now be released by jarring upwardly with
sufficient force to break shear pins 73 (FIG. 3), whereupon the
running tool may be removed from the well leaving the bit section
secured to the landing shoe with the underreamers in extended
operating position (FIG. 4).
Power sub P may now be connected to the upper end of the casing and
rotation of the latter as the drill string will be effected to
drill the well as indicated in FIG. 8.
The drilling fluid circulation will be through hose connection H,
swivel S and through a conduit in power sub P into the bore of
casing C. Thence, through the bit section, the fluid flowing
through the bores of sleeves 44 and 32 to bore 58 and through the
now-closed bypass valve to the discharge passages in the pilot bit
and the jet nozzles 66. The mud flush will return to the surface
through the annulus between well bore W and casing C.
When necessary to withdraw the bit section from the casing in order
to replace or repair the pilot bit, underreamers or any other part
of the bit section, a fishing tool, designated generally by the
letter T, of the form illustrated and described in my copending
application, Ser. No. 869,563, filed Oct. 27, 1969, or of any other
generally conventional form, the details of which do not form a
part of this invention, will be run into the casing bore on a wire
line, or tubing string if desired, and will be latched into groove
45a of lock sleeve 44, as seen in FIG. 5. On application of upward
pull to the fishing string, the lock sleeve will be drawn upwardly
bringing shoulders 37 and 46 in abutment and placing lock recess 48
in registration with lock dogs 40, freeing the latter from recess
42. This same upward movement, now transmitted through abutting
shoulders 37 and 46 will raise setting sleeve 32 sufficiently to
place recess 36 in registration with anchor dogs 24 which will thus
be free to retract from anchor groove 26. Additionally, the upward
movement of the setting sleeve will be transmitted to nozzle 57
which will, in turn, raise sleeve valve 59 off of the end of
extension 62 opening the bypass valve to allow fluid to dump back
into the well as the bit section is raised. Further the upward
movement of nozzle 57 will rotate the underreamers back to their
retracted position inside slots 53. The parts will now be in the
same positions as when running into the casing (FIG. 6) and the
entire bit section may now be withdrawn through the casing.
iii. drilling is to be resumed, the bit section, with the parts in
the original retracted positions, will be returned through the bore
of the casing to its lodgment in shoe 10, the bit section anchored
and the underreamers extended as described, and drilling will be
resumed.
Fig. 7 illustrates a modification in which the setting sleeve and
lock sleeve are effectively combined. In this modification body 16
is provided with an external annular recess 90 at a point spaced
between shoulder 30 and recess 36. Setting sleeve 32 is provided
with a plurality of angularly spaced openings or windows 138 (one
shown) in which are mounted pivoted latches 140 which are biased by
means of springs 91 to urge the upper ends of the latches to swing
outwardly of windows 138. With this arrangement it will be seen
that when setting sleeve 32 moves downwardly relative to body 16
sufficient to bring the upper end positions of the latches opposite
recess 90, the spring pressure on the lower ends of the latches
will swing the upper ends of the latches outwardly of windows 138
into recesses 90 causing them to abut the shoulder 128 forming the
upper wall of recess 90 and thereby locking the setting sleeve in
the position at which anchor dogs 24 will be anchored in recess 26.
This downward movement, as in the previously described embodiment,
will close valve 59--61 and hold the underreamers in their extended
positions.
Running tool R will be slightly modified, as shown, but in general
will operate in substantially the same way as the earlier described
tool. Similarly, the retrieving tool will be modified so as to
swing latches 140 out of recess 90 when effecting release of the
bit body from the landing shoe. These modificatons will be readily
apparent to those skilled in the relevant art.
FIGS. 9 and 10 illustrate a further modification in which the use
of a running tool is dispensed with and the bit section run and set
by a combination of gravity and hydrostatic pressure. As seen in
these FIGS., the only structural changes are the provision at the
lower end of lock sleeve 44 of a bottom closure plate 92 having a
central orifice 93 of relatively restricted dimensions. Also body
16 is provided with an extension 16 a which is secured directly to
a setting sleeve extension 32 a by means of a shear pin 73 a to
hold the parts in the relatively retracted positions.
In operation, the bit section will be inserted into the casing and
allowed to fall of its own weight to lodgment on male splines 14.
Pumped fluid may be employed to assist the bit section to move
through the casing to its seat. As soon as the bit section is in
place on pins 14, pump pressure will be increased and pressure will
build up inside lock sleeve 44 by reason of the restricted orifice
93, the various seals including seal 20 preventing leakage of the
pressure about the outside of the bit section. When the hydrostatic
pressure has built up sufficient force to break shear pins 73a,
both sleeves 32 and 44 will be caused to moved downwardly to
position driving anchor dogs 24 into anchor recess 26 and lock dogs
40 into lock recess 42. Also, sleeve valves 59--61 will be closed
and the underreamers extended to their operative position where
rotation of the casing from the surface will permit drilling
ahead.
To remove the bit section when required, a retrieving tool such as
that previously described may be run and operated to raise lock
sleeve 44 and then setting sleeve 32, with opening of the bypass
valve and retraction of the underreamers.
From the foregoing it will be evident that a drilling system is
provided in which the casing itself which is ordinarily required to
line the bore hole will be used as the drilling string and will be
continuously fed into the hole as the drilling proceeds, thereby
obviating all of the additional operations conventionally required
in rotary drilling and for casing the well. The hazards
accompanying the conventional drilling and casing operations,
including those arising from "round trips" of the drill string,
will be obviated, drilling operations greatly facilitated, and time
of operation substantially reduced.
Landing shoe 10 may be employed to land conventional tools required
for cementing the casing or performing other operations commonly
required in completing the well.
It will be understood that various changes and modifications may be
made in the details of the illustrative embodiment within the scope
of the appended claims but without departing from the spirit of
this invention.
* * * * *