Note: Descriptions are shown in the official language in which they were submitted.
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METHOD AND APPARATUS FOR DRILLING A BOREHOLE
WITH A BOREHOLE LINER
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to drilling well bores and in particular a method and an
apparatus for drilling a wellbore using a borehole liner.
Background of the Invention
A drilling liner can be carried along behind the pilot bit to line a borehole
while it is
being drilled. Previously drilling fluid has been circulated down through a
drill pipe, through
the pilot bit and up the outer annulus between the drilling liner and the
borehole wall. In
these previous methods, drilling with a liner was often difficult. Pressure
exerted on the
formation due to a combination of the fluid density and the frictional
pressure losses in the
small annulus between the liner and the borehole/casing wall may induce
fractures in the
formation and cause lost circulation.
Alternately, in other methods, the drilling fluid is circulated down through
the drill
pipe and forced up through the liner by sealing between the liner shoe and the
borehole wall.
This requires the use of an open hole packer, which may not be desirable.
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SUMMARY OF THE INVENTION
In accordance with one aspect of the present invention, there is provided a
borehole
drilling apparatus comprising: a drill string including a center bore and a
distal end; a bit
assembly at the drill string's distal end; a ported sub mounted on the drill
string, the ported
sub including an upper surface, a lower surface, a bore extending from the
upper surface to
the lower surface to which the drill string is connected, an axially extending
port for
providing fluid communication between the lower surface and the upper surface
separate
from fluid communication with the bore and a lateral port for providing fluid
communication
between the drill string center bore and an outer surface of the sub between
the upper surface
and the lower surface, the lateral port being substantially isolated against
fluid
communication with the axially extending port during operation; and a liner
engaging surface
encircling the lower surface, the liner engaging surface formed to releasably
secure a
borehole liner such that the drill string extends through the borehole liner
with the bit
assembly extending beyond a liner shoe of the liner with an opening between
the drill string
and the liner.
In accordance with another broad aspect, there is provided a method for
drilling a
borehole comprising: providing a drill string including a center bore, a
distal end, a bit
assembly at the distal end; hanging a liner from the drill string, thereby
forming an annular
space between the drill string and the liner and with the bit assembly
extending from a lower
end of the liner; positioning the drill string with the liner attached thereto
in a borehole such
that a second annular space is formed between the liner and the borehole wall;
operating the
bit assembly to proceed with drilling the borehole; and circulating drilling
fluid down through
the center bore of the drill string out through the bit assembly and down
through the second
annular space between the liner and the borehole wall, the drilling fluid
returning up through
the annular space between the drill string and the liner.
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In accordance with another broad aspect of the present invention, there is
provided an
apparatus for drilling a borehole defined by a borehole wall, the apparatus
comprising: a drill
string including a center bore and a distal end; a bit assembly at the drill
string's distal end; a
liner including an upper end and an inner bore and the liner being arranged
with the drill
string extending through the liner inner bore; a ported sub mounted between
the drill string
and the liner to support the liner on the drill string, the ported sub
including an upper surface,
a lower surface about which the liner is connected, a bore extending from the
upper surface to
the lower surface through which the drill string is connected to the ported
sub, an axially
extending port for providing fluid communication between the liner inner bore
and an upper
opening to the upper surface of the sub, a lateral bore providing fluid
communication
between the drill string center bore and an outer surface of the sub between
the upper surface
and the lower surface, the lateral port being substantially isolated against
fluid
communication with the axially extending port during operation; and a seal
adjacent the
upper end of the liner and selected to seal against fluid flow upwardly about
the liner upper
end from an annulus formed between the liner and the borehole wall.
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BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a schematic sectional view along a wellbore including a drilling
system
including a drilling liner and showing a method according to the present
invention.
Figure 2 is a schematic sectional view along a wellbore including another
drilling
system including a drilling liner and showing another method according to the
present
invention.
Figure 3 is a schematic sectional view along a wellbore showing another
drilling
apparatus and method according to the present invention.
Figure 4 is a schematic sectional view along a wellbore showing another
drilling
apparatus and method according to the present invention.
Figure 5 is a view showing a method that may follow from that of Figure 4.
Figure 6 is a view showing a method that may follow from that of Figure 5.
Figure 7 is a view showing a method that may follow from that of Figure 6.
Figure 8 is a schematic sectional view along a wellbore drilling apparatus.
Figure 9 is a schematic sectional view along a wellbore showing another
drilling
method employing the apparatus of Figure 8.
Figure 10 is a view showing a method that may follow from that of Figure 9.
Figure 11 is a view showing a method that may follow from that of Figure 10.
Figure 12 is a view showing a method that may follow from that of Figure 11.
Figure 13 is a view showing a method that may follow from that of Figure 12.
Figure 14 is a view showing a method that may follow from that of Figure 13.
Figure 15 is a view showing a method that may follow from that of Figure 14.
Figure 16 is a view showing a method that may follow from that of Figure 15.
CA 02519019 2012-02-10
DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS
Drilling with a liner can be accomplished by drilling the liner in place using
a drill
string 10 formed of, for example, drill pipe or coiled tubing. Drill string 10
may extend from
surface to the bottom 12 of the hole. Drill string 10 includes a center bore
13 and can include
a bottom hole assembly 17 and a bit assembly 15 for drilling a borehole sized
to accommodate
passage therethrough of the liner. Drilling assembly 15 may include, for
example, a pilot bit
14 and an underreamer 16 (as shown), a bicenter bit, a pilot bit and cutting
shoe, etc. As will
be appreciated, the bit assembly may be driven by various means such as for
example a mud
motor in the bottom hole assembly. A liner 18 may be hung onto drill string 10
by a ported
sub 20. Ported sub 20 may be mounted on the drill string, for example about a
drill string
tubular member or the drill string can be connected thereto, as by threaded
connection.
Ported sub 20 may include a liner engaging surface for releasably engaging the
liner at its up
hole end. The surface may encircle the lower end of the sub so that the sub
fits in or over the
upper end of the liner. The sub may fit sealing against the liner to limit
fluid flow
therebetween. The liner may be engaged by the sub such that it is hung with an
annulus
formed between the drill string and the liner, while the lower end of the
liner is open about
the drill string or ported to allow fluid flow into the drill string/liner
annulus.
A liner hanger 19 is provided to support liner 18 within casing liner 22 or
against the
borehole wall, when it is desired to set the liner.
Ported sub 20 includes axially extending ports 26 through which drilling fluid
can pass
axially through the wellbore between the liner inner bore and the upper
surface of the sub,
while returning to surface. Axially extending ports 26 may or may not be
parallel
to the center line of the sub, with reference to its position in the borehole,
but permit fluids to
pass substantially axially through the well bore. Axially extending ports 26
may be sized with
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consideration as to the volume of drilling fluid that is to be circulated and
with consideration
as to the size of cuttings that must pass therethrough.
Sub 20 carries a seal 28 such as a packer, a narrow gap seal or swab cups so
that fluid
is prevented from passing upwardly therepast, thereby substantially preventing
drilling fluid
from passing out of the annulus about the liner. In one embodiment, the seal
may alternately
be carried about the upper end of the liner. The seal may be selected with
consideration as to
the borehole conditions to be encountered. For example, where the borehole is
lined with a
casing, the seal may be selected to seal against the casing wall.
As drilling commences, fluid in the wellbore tends to be trapped in the
annulus 21
about the liner. Drilling fluid provided from surface through drill string 10
flows through the
inside (Q1) of drill string 10 and out through the pilot bit. Due to the
action of seal 28, fluid
trapped in annulus 21 creates a fluid lock forcing drilling fluid to return
(Q2) up through the
annulus between drill string 10 and liner 18. Fluid passes through axially
extending ports 26
through sub 20 and returns to surface through the annulus between the casing
liner 22 and the
drill string.
Referring to FIG. 2, there is shown another apparatus and method according to
the
present invention. Drill string 10 extends from surface to the bottom 12 of
the hole and can
include a bit assembly including, for example, a pilot bit 14 and an under
reamer 16 driven
and controlled by a bottom hole assembly 17 which may include, for example, a
mud motor,
MWD, LWD, etc., as desired.
Liner 18 is hung onto drill string 10 by a ported sub 20a connected
therebetween.
Liner 18 carries a liner hanger 19 for wedging the liner in position in the
borehole.
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As drilling commences, drilling fluid, initially provided through drill string
10, may be
split to both (i) flow F 1 down through the inside of drill string 10 and (ii)
flow F2 down
through the annulus about the outside of liner 18. Fluid then returns F3 up
through the
annulus between drill string 10 and liner 18, passes through ported sub 20a
and returns to
surface through the annulus F4 between the borehole wall or casing liner 22
and the drill
string. The flow Fl provides that there is enough fluid to drive and lubricate
pilot bit 14 and
under reamer 16 while flow F2 acts against a flow of drilling fluid up the
annulus between
the liner and the borehole. Flow F2 may force all drilling fluid to pass up
between the liner
and the drill string. It has been found that flow through the annular space
between liner 18
and drill string 10 causes less pressure loss than drilling fluid flow through
the annular space
between the liner and the borehole wall.
Ported sub 20a can include at least one lateral port 24 through which the
fluid flow is
split. Lateral port 24 allows fluid to be diverted from the drill string inner
bore to the annular
space about the liner and may, therefore, open between drill string center
bore 13 and the
outer surface of liner 18, as shown, or the outer surface of the ported sub
where it extends
above the liner.
Flow F2 through lateral port 24 may be controlled or restricted so that only a
portion
of the flow passes through that port with the remainder continuing down Fl
through center
bore 13 to the pilot bit. In one embodiment, a flow restrictor 25 can be
installed in lateral port
24 to provide resistance to fluid flow through the port.
Ported sub 20a also includes at least one axially extending port 26 through
which flow
F3 can pass. Axially extending ports 26 may be sized to permit cuttings to
pass.
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Ported sub 20a carries a seal 28 such as a packer or swab cups so that fluid
is
substantially prevented from passing upwardly from the annulus about the liner
hanger and
substantially prevented from communication between lateral port 24 and axially
extending
port 26, thereby permitting fluid circulation to be controlled about the liner
hanger.
In one embodiment, the drilling may be conducted through a borehole liner,
such as a
casing liner 22 that may already be cemented in the hole. The drilling may
proceed using the
above-noted circulation until the liner reaches a casing point, which is a
point at which it is
desired to set the liner in the borehole. The liner can be any length L in
order to achieve a
selected extension beyond a lower end 30 of the installed casing.
When the liner reaches casing point, the liner can be hung in the casing
string, for
example adjacent lower end 30, by actuation of liner hanger 19. Ported sub 20a
and drill
string 10, with attached pilot bit 14 and under reamer 16, may then be
disconnected from the
liner and retrieved through the liner and pulled from the well bore. The under
reamer, when
expanded, cuts a borehole greater than the outer diameter of the liner, but
can be collapsed to
be withdrawn through the liner.
Thereafter, if desired, the drill string can be reintroduced to the liner for
cementing
through the drill string. In one embodiment, it may be desirable that the
drill string and
ported sub 20a be removable from the liner at selected times during the
drilling process, for
example, when it is necessary to replace or repair a bit, under reamer or
bottom hole
assembly component. In such an embodiment, the ported sub 20a may be
reconnectable to
the liner and the liner hanger may be reversibly drivable to repeatedly
engage, and release
from engagement with, the casing.
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Referring to FIG. 3, there is shown another drilling assembly and method. A
liner
18 can be drilled in place using a drill string 10 that may be, for example,
formed of drill
pipe. Drill string 10 extends from surface towards the bottom 12 of the hole
and can include
drilling tools including, for example, a pilot bit 14, an under reamer 16 and
a bottom hole
assembly 17 including a mud motor, MWD and LWD.
The drill pipe joints I Oa may have a selected outer diameter so that there is
a
clearance between the inner diameter of the liner and the outer diameter of
the drill pipe
joints. Such a clearance may be selected to permit passage of drill cuttings
and drilling fluid
from a drilling operation.
A ported sub 20a may be provided including a bore 23 from its upper surface to
its
lower surface. Drill string 10 can be threadedly connected into bore 23 such
that the bore
provides communication to the drill string inner bore above and below the sub.
Sub 20a may
include lateral ports 24 open to and extending from bore 23 and axially
extending ports 26
extending substantially parallel to, but not in communication with, bore 23.
Liner 18 may be hung onto drill string 10 by the ported sub 20a. In so doing,
lateral
ports 24. may be aligned with ports 24a through the liner so that a passage
may be opened
from bore 23, that is in communication with the drill string center bore, to
the outer surface of
liner 18. As such, a portion of any drilling fluid pumped through drill string
can be a jetted
through lateral ports 24 and ports 24a into annulus 21.
Ported sub 20a also includes axially extending ports 26 through which drilling
fluid
can pass upwardly out of the liner inner bore. Axially extending ports 26 are
sized to permit
cuttings to pass. Axially extending ports 26 are not in fluid communication
with lateral ports
24.
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Liner 18 carries a seal 28 such as a packer or swab cups so that fluid is
prevented
from communicating between ports 24, 26 through the annulus about the liner,
thereby
permitting the circulation to be controlled about the liner. Liner 18 also
carries a liner hanger
19 for wedging between the liner and the casing 22 when setting the liner in
the bore hole.
Stabilizers can be installed to control positioning of the liner and the drill
string within
the assembly. For example, one or more stabilizers/centralizers 34 may be
installed about the
liner and/or one or more stabilizers/centralizers 36 may be installed between
the drill string
and the liner. Of course, these stabilizers/centralizers may be formed to
permit fluid flow
therepast. Stabilizer/centralizer 36 also permits the passage of drill
cuttings. In one
embodiment, stabilizer/centralizer 36 may be fluted or ported to permit
passage of drill
cuttings and fluid.
As drilling commences using the embodiment of FIG. 3, the drilling fluid is
initially provided from surface through drill string 10 and may be split at
sub 20a to flow
down both (i) through the inside (F1) of drill string 10 and (ii) through
ports 24, 24a into the
annulus 21 (F2) 'about the outside of liner 18. Fluid then returns F3 up
through the annulus
between drill string 10 and liner 18. Fluid passes through axially extending
ports 26 of sub
20a and returns to surface through the annulus F4 between casing liner 22 and
the drill string.
Flow F2 need only be sufficient to force return flow up between the liner and
the drill string,
rather than between the borehole wall and the liner.
In another embodiment shown in FIG. 4, a ported sub 20c may include a setting
tool component 3 8 to drive the setting of liner hanger 19. In such an
embodiment, the ported
sub is positioned between liner 18 and drill string 10. Ported sub 20c
accommodates passage
therethrough of drill string 10. Ported sub 20c includes at least one axially
extending port 26
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formed to permit fluid communication between the inner bore of liner 18 and an
opening on
the upper side of a seal 28 about the sub. Drill string 10 and axially
extending port 26 may
pass through various components of sub 20c in this embodiment. Sub 20c may
also, if desired,
include a lateral port 24, possibly including a check valve 27 or restriction,
for establishing a
reverse circulation down the annulus about liner 18.
Setting tool component 38 provides one option for setting liner hanger 19. In
the
illustrated embodiment, setting tool component 38 may be hydraulically
operable by selection
of fluid pressures in the drill string. For example, as illustrated, a valve
40 may be positioned
in drill string and a fluid passage 42 may be provided in component 38 up hole
from valve 40
for communicating fluid to the liner hanger. In particular, valve 40 may
include a seat 44 for
accepting and creating a seal with a ball 46 (FIG. 5) launchable from surface
when it is
desired to generate fluid pressures suitable for operation of the setting tool
component. Such
generated fluid pressures may be communicated to the liner hanger through
passage 42.
In operation of the embodiment just described, the assembly may be employed
for
drilling when drill string 10 is open. Drilling fluid may be circulated
downhole with a
portion passing though lateral port 24 and down through annulus 21 about liner
18 and the
remaining fluid flowing through the drill string and past valve 40 and to the
bit (not shown).
The pressure of the drilling fluid flows cause drilling fluid to be circulated
back up through
the annulus between liner 18 and drill string 10, through sub 20c and back to
surface.
With reference to FIG. 5, when it is desired to set the liner in the borehole,
for
example against casing 22, a ball 46 can be launched, which is sized to pass
through drill
string 10 and seat in valve 40. The drill string can then be pressured up P to
a desired level
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to actuate component 38 to set liner hanger 19. Passage 42 allows for
communication of this
fluid pressure to the liner hanger.
In an embodiment including a component 38 as described, it may be useful to
provide
a valve 50 or another mechanism for closing lateral port 24, where it is
included in sub 20c so
that generation of actuation pressure is not jeopardized by release through
lateral port 24. In
addition or alternately, it may be useful to provide a valve or other
mechanism in passage 42
which may be selectively openable so that the liner hanger mechanism is not
affected by fluid
during run in or drilling. In such an embodiment, valve 50 is closed and the
valve in passage
42 is opened, before seeking to set the liner hanger by application of fluid
pressure.
After setting liner hanger 19, it may be desirable, as shown in FIG. 6, to
resume
access through drill string 10 below valve 40. As such it may be desirable to
select the valve
at ball 46 to be removable by expulsion of the ball downwardly, as shown, by
destruction of
the ball or of the valve seat or by reverse circulation of the ball to
surface.
Pressuring up, downhole manipulation, such as axial or rotational movement,
etc. can
be employed to release at least a portion of sub 20c from the liner 18 and
liner hanger 19. If
desired, downhole manipulation, such as axial or rotational movement or
abutment of the sub
or the drill string, may be useful to compress seal 28, such compression
possibly being useful
to facilitate pulling the sub and the drill string out of the hole. Such
manipulation may be
achieved, for example, by setting sub 20c down on liner 18 once they have been
separated.
Once sub 20c is released from the liner, it can be tripped with the drill
string to surface.
Where it is desired to, thereafter, cement liner 18 in place, a completion
string 54 may
be run into the hole through casing 22 and liner 18. As shown in FIG. 7,
completion string
54 may carry a packer 56 sealable between string 54 and liner 18 such that any
cement C
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conveyed through the string may be directed into annulus 21 between the liner
and the
borehole wall.
Referring to FIG. 8, in another embodiment a sub 20d and other mechanisms may
be provided to permit running in, drilling, hanging and cementing the liner in
a borehole
without tripping of sub 20d or the string 10 on which the sub is carried. In
such an
embodiment, sub 20d may include a bore 23 from its upper surface to its lower
surface or
may accommodate the drill string therethrough. Drill string 10 can be
threadedly connected
into bore 23 such that the bore provides communication between the drill
string inner bore
above and below the sub.
A liner 18 may be secured to sub 20b to hang down over a length of the drill
string
with an annulus formed therebetween. An opening is formed by spacing between
liner shoe
18a and drill string 10 and pilot bit 14 and under reamer 16 (FIG. 10) extend
out from the
end of the liner. Liner 18 may carry a hydraulically operable liner
hanger/packer 19a.
Sub 20d may include lateral ports 24 open to and extending from bore 23.
Lateral
ports 24 may be closed by manipulation of the sub relative to the liner. Sub
20d may also
include axially extending ports 26 extending substantially parallel to, but
not in
communication with, bore 23, and a seal 28 about the sub selected to seal
between the sub and
a borehole in which the assembly is to be used.
In the embodiment of FIG. 8 the bottom hole assembly may include a pilot bit
14,
an underreamer 16, a lower drill string bore valve 62, such as may be provided
by a ball catch
seat-containing sub and a tubing wall valve 64, such as may be provided by a
pump out sub.
As will be appreciated, the bottom hole assembly may also include other
components such as,
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for example, a positive displacement motor, mechanisms for MWD/LWD,
centralizers,
stabilizers, etc.
Sub 20d may further include a setting actuation portion for the liner
hanger/packer
19a that may include, for example, a ball catch valve 40 positioned in bore 23
and including a
seat for accepting a ball 46 (FIG. 11) launchable from a position above the
valve, fluid
passages 42 to hanger/packer 19a and at least one valve 60 for closing off
each of the
passages. Passages 42 may be positioned above lateral port 24 and valve 40 may
be positioned
between passages 42 and lateral ports 24, so that passages 42 may be
hydraulically isolated by
valve 40 from lateral ports 24. In this position, lateral ports 24 may also be
accessible below
hanger/packer 19a.
In a liner drilling operation, the assembly of FIG. 8 may be useful to achieve
any or
all of (i) drilling in the liner, possibly using reverse circulation of
drilling fluid, (ii) hanging
the liner by, for example, hydraulically setting slips and packing off the
annulus, (iii)
releasing the liner, (iv) cementing the liner, by introducing cement to the
liner-borehole
annulus, (v) holding the cement in the annulus until it sets, to avoid U-
tubing of cement
slurry, and (vi) clearing out cement slurry from the drill string, and
possibly portions of the
casing and liner.
In particular, with reference to FIGS. 9 to 16, an assembly including sub 20d,
drill
string 10 and liner 18 may be made up and run into a borehole through, for
example, a casing
22 already installed and cemented in place. During run in, fluid may be
circulated and any
returns R displaced by seal 28 may be routed through axially extending ports
26. The
assembly can be run in until the pilot bit reaches the intermediate casing
shoe 22a.
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At the casing shoe, as shown at FIG. 10, drilling can commence by operation of
pilot bit 14 and underreamer 16, wherein the shoe is drilled out and drilling
may proceed to
liner total depth. In so doing, mud can be pumped F1 down the drill string. A
smaller
portion, for example in one embodiment about 30%, of the mud can pass F2
through lateral
ports 24 and down the liner/borehole annulus 21, while the remainder F3
continues down
the string to be jetted through pilot bit 14. Flows F2 and F3 meet at the
opening between
liner shoe 18a and drill string 10 and together return towards surface by
flowing F4 up
through the string/liner annulus. Seal 28 isolates flow F2 separate from flow
F4.
At total depth, mud can be circulated to clean the hole that has been drilled.
Then, as
shown in FIG. 11, ball 46 can be dropped to create a seal at valve 40, -so
that hanger/packer
19a may be hydraulically set H to hang the liner in the borehole.
With reference to FIG. 12, sub 20d may then be disconnected from liner 18, as
by
application of left hand torque to the drill string, and thereby to sub 20d,
from surface. The
drill string may be hoisted slightly to confirm that the liner has been
released from the liner.
These manipulations may close valves 60. Fluid pressure may then be increased
in drill
string such that ball 46 is released and lands in lower drill string bore
valve 62 such that flow
to pilot bit 14 may be stopped but access to lateral ports 24 is again
achieved. Lateral ports 24
may then operate as cementing ports and once circulation is established from
surface through
ports, a fluid caliper FC can be pumped for cement volume determination.
A spacer and cement slurry C (FIG. 13), as required, can then be pumped down
the
drill pipe and out through lateral ports 24. Such pumping drives the cement
slurry C to be
reversed down borehole/liner annulus 21 and up through the liner in the
liner/string annulus.
Cement pumping can be continued until the cement is displaced to a point above
sub 20d. In
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one embodiment, for example, the cement may be displaced to a level about 200
ft. above the
sub.
As shown in FIG. 14, while the cement remains hydraulic, drill string 10 and
sub
20d may be hoisted in the liner to elevate the bottom hole assembly to a
position above liner
shoe 18a. In one embodiment, the bottom hole assembly may be spaced at least
500 feet
above liner shoe 18a. Lateral ports 24 are closed through the sub. Any
openings on liner that
correspond to lateral ports 24 are also closed. Tubing wall valve 64 may then
be opened, as by
pressuring up the drill string or by manipulation. To flush cement from the
drill pipe, as
shown in FIG. 15, fluid may be circulated S through tubing wall valve 64. In
the
illustrated embodiment, such circulation is conducted in the reverse down
through casing 22,
through valve 64 and back up through drill string 10.
Once the cement has set, the drill string and the sub can be hoisted out of
the hole,
leaving the liner cemented in place. This is shown in FIG. 16.
While the foregoing method may be useful with various sized strings and
boreholes
and various equipment, in one embodiment according to FIGS. 9 to 16, an 113/4
inch liner
may be drilled in, hanged and cemented in a 133/8 inch casing annulus using a
105/8 inch
pilot bit with a 14 inch cut PDC underreamer, as is available from TESCO
Corporation, who
is the assignee of the present invention. The pilot bit and underreamer may be
driven by a
positive displacement motor. Of course, this example is only included for the
purpose of
illustration and is not intended to be used to limit the invention in any way.
Numerous modifications, variations and adaptations may be made to the
particular
embodiments described above without departing from the scope of the invention
as defined in
the claims.
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