U.S. patent application number 12/445248 was filed with the patent office on 2010-02-11 for method and apparatus for running tubulars.
This patent application is currently assigned to CALEDUS LIMITED. Invention is credited to Paul Howett, Mike Wardley.
Application Number | 20100032170 12/445248 |
Document ID | / |
Family ID | 37491408 |
Filed Date | 2010-02-11 |
United States Patent
Application |
20100032170 |
Kind Code |
A1 |
Howett; Paul ; et
al. |
February 11, 2010 |
METHOD AND APPARATUS FOR RUNNING TUBULARS
Abstract
A method is disclosed for running a completion string, such as
casing, into a predrilled wellbore while allowing rotation of a
downhole component with respect to the completion string. The
downhole component may be a drill shoe or reamer shoe for example.
There is also disclosed a drillable or millable drive assembly for
driving the rotation of a portion of the casing assembly and other
applications thereof.
Inventors: |
Howett; Paul; (Aberdeen,
GB) ; Wardley; Mike; (Aberdeen, GB) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W., SUITE 800
WASHINGTON
DC
20037
US
|
Assignee: |
CALEDUS LIMITED
Aberdeen
GB
|
Family ID: |
37491408 |
Appl. No.: |
12/445248 |
Filed: |
October 4, 2007 |
PCT Filed: |
October 4, 2007 |
PCT NO: |
PCT/GB07/03769 |
371 Date: |
June 9, 2009 |
Current U.S.
Class: |
166/383 ;
166/155; 175/107 |
Current CPC
Class: |
E21B 17/08 20130101;
E21B 17/14 20130101 |
Class at
Publication: |
166/383 ;
166/155; 175/107 |
International
Class: |
E21B 23/08 20060101
E21B023/08; E21B 23/10 20060101 E21B023/10; E21B 4/00 20060101
E21B004/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 13, 2006 |
GB |
0620272.5 |
Claims
1. A method of running a casing string in a wellbore, the method
comprising the steps of: (a) providing a casing string assembly in
a wellbore, the casing string assembly having a first portion and a
second portion; and (b) rotating a first portion of the casing
string assembly relative to a second portion of the casing string
assembly while running the casing string.
2. The apparatus as claimed in claims 49 wherein the apparatus
includes a swivel, and the lower section is located below the
swivel, and the upper section is located above the swivel.
3. (canceled)
4. The apparatus as claimed in claim 49 wherein the shoe includes
an abrasive or cutting surface.
5. The apparatus as claimed in claim 49 wherein the shoe is a
casing reaming shoe.
6. (canceled)
7. The method as claimed in claim 1 wherein the casing string is
run while the second portion of the casing string assembly is
substantially not rotated with respect to the wellbore.
8. The method as claimed in claim 1 including the step of driving
rotation of the first portion of the casing string assembly by
circulation of fluid through the casing string.
9. The method as claimed in claim 11 wherein the rotation of the
first portion of the casing string assembly is driven by the drive
assembly, comprising a mud motor.
10. (canceled)
11. The method as claimed in claim 1 including the steps of
locating a drive assembly with respect to the casing string
assembly and running the drive assembly in hole with the casing
string assembly.
12. The method as claimed in claim 11 further including the step of
retrieving the drive assembly from the casing string assembly.
13-22. (canceled)
23. The method as claimed in claim 1 including the additional step
of preventing rotation of the first portion of the casing string
assembly with respect to the second portion.
24. (canceled)
25. The method as claimed in claim 1 including the additional step
of drilling beyond the casing string assembly.
26. The method as claimed in claim 11 including the step of
drilling through the drive assembly.
27. (canceled)
28. The method as claimed in claim 11 including: (a) running the
drive assembly with the casing; and (b) cementing the casing with
the drive assembly downhole.
29. The method as claimed in claim 11 including the step of running
a float collar with the casing, above the drive assembly.
30-48. (canceled)
49. Apparatus for running a casing string, the apparatus comprising
an upper section adapted to be coupled to the casing string; a
lower section rotatable with respect to the upper section and
including a shoe located below the tubular; and engagement means
for engaging a drive assembly adapted to rotate the shoe with
respect to the upper section.
50. A drive assembly for a downhole apparatus comprising an upper
section adapted to be coupled to a tubular; a lower section
rotatable with respect to the upper section; and a motor for
imparting rotation to the lower section; wherein the drive assembly
is drillable or millable by conventional downhole drilling
equipment.
51. (canceled)
52. The drive assembly as claimed in claim 50 wherein the motor
comprises a drillable or millable rotator.
53. (canceled)
54. The drive assembly as claimed in claim 50 wherein the lower
section is connected to a shoe.
55. A drive assembly as claimed in claim 54 wherein the shoe
includes a non-return valve to prevent fluid flow into the shoe
from the wellbore.
56. A drive assembly as claimed in claim 50 adapted to have a
rotating mode and a non-rotating mode.
Description
[0001] The present invention relates to the drilling and completion
of wellbores. In particular, the present invention in one of its
aspects relates to a method for running a completion string, such
as casing, into a predrilled hole. In another of its aspects, the
invention relates to apparatus for allowing rotation of a downhole
component with respect to a completion string. In another of its
aspects, the invention relates to a drillable or millable drive
assembly and applications thereof.
[0002] Casing is steel pipe cemented in place during the wellbore
construction in order to stabilise the wellbore. The casing string
is made up of a plurality of casing sections, usually threaded
together, each run from the surface to a casing point at the bottom
of an open hole at a specific diameter. The wellbore is extended by
drilling beyond the casing at a smaller inner diameter, and a
second casing string is run from the bottom of that open hole back
to the surface. The wellbore thus comprises a series of concentric
casing strings, with the inner most strings extending to a greater
depth in the wellbore.
[0003] When the casing is run into the wellbore, it is desirable to
use casing that is a close fit to the open hole diameter. A float
shoe may be used to guide the casing toward the centre of the hole
and minimise the impact of the casing with rock ledges or washouts
as the casing is run into the wellbore. The float shoe is typically
made from a drillable material, since the float shoe must be
drilled through if the well is to be deepened beyond the casing
point.
[0004] When running casing using conventional float shoes, the
casing string can still have a propensity to stand up on ledges and
washouts. Casing reaming shoes attached to the lower end of the
casing have an abrasive surface for enlarging the open hole size
and assisting in deployment of the casing. During casing reaming,
the entire casing string will be rotated, and the reaming shoe
smoothes the run-in of the casing. However, the frictional forces
of the casing string against the open bore reduce the torque
transferable to the casing reaming shoe. The forces can be
significant as the casing string may extend over considerable
distances. In addition, rotation of the casing string in the open
bore can cause wear and damage to the casing string.
[0005] Casing drilling techniques have also been developed, in
which the casing is run into the hole as it is being drilled. In
most cases, it would be necessary to drill beyond the casing point.
One solution to this is to divert a drill string around the drill
bit used for the casing drilling operation, using a whipstock
provided in the casing section. Alternatively, the drill bit can be
retrieved from the wellbore using a specialised fishing tool in a
dedicated run. Alternatively, it may be possible to use a drillable
bit that can be drilled through in a subsequent drilling operation.
All of these solutions are specialised operations requiring
dedicated equipment and procedures, and present significant
technical challenges in some drilling environments.
[0006] Similar challenges apply to the running of completion
strings such as including liners, sand control screens, slotted
liners, expandable tubulars, sometimes referred to as lower
completion strings or openhole completion strings.
[0007] It is one object of the invention to provide a method and
apparatus for casing the running that at least mitigate one or more
disadvantages of conventional casing running methods and
apparatus.
[0008] It is an aim of at least one aspect of the invention to
provide a method and apparatus for allowing selectable rotation of
downhole equipment mounted at the bottom of the casing string.
[0009] It is a further aim of an embodiment of the invention to
provide a method and apparatus for rotating a portion of a
completion string by controlled pumping of circulation fluid.
[0010] It is a further aim of at least one aspect of the invention
to provide a drive assembly for downhole equipment that is
drillable or millable by conventional downhole drilling
equipment.
[0011] According to a first aspect of the invention there is
provided a method of running a casing string in a wellbore, the
method comprising the steps of: [0012] providing a casing string
assembly in a wellbore, the casing string assembly having a first
portion and a second portion; and [0013] rotating a first portion
of the casing string assembly relative to a second portion of the
casing string assembly while running the casing string.
[0014] It should be understood that the term casing string assembly
includes any casing sections along with apparatus associated with
the casing sections, including a drill shoe, or reaming shoe
located at the lower end of the casing string.
[0015] Preferably, the casing string assembly includes a swivel,
and the first portion of the casing string assembly is a lower
portion located below the swivel, and the second portion of the
casing string assembly is an upper portion located above the
swivel.
[0016] Preferably, the first portion of the casing string assembly
includes a shoe. More preferably, the shoe includes an abrasive or
cutting surface. The shoe may be a casing reaming shoe.
[0017] The second portion of the casing string assembly may include
a plurality of casing sections. Preferably, the second portion of
the casing string assembly provides the majority of the length of
the casing string assembly. More preferably, the second portion of
the casing assembly provides greater than 70% of the length of the
casing string assembly. More preferably greater than 80%. More
preferably, at least 90%.
[0018] Preferably, the casing string is run while the second
portion of the casing string assembly is substantially not rotated
with respect to the wellbore.
[0019] In this manner, the invention allows for a reduction to the
length of tubular that is rotated with respect to the wellbore,
reducing frictional forces and wear to the casing string.
[0020] Preferably, all casing sections in the casing string
assembly are provided in the second portion.
[0021] The method may include the step of driving rotation of the
first portion of the casing string assembly by circulation of fluid
through the casing string. The rotation of the first portion of the
casing string assembly may be driven by a drive assembly, which may
comprise a mud motor. In this way, pumping of fluid controls the
rotation and reaming function.
[0022] The method may include the step of locating a drive assembly
with respect to the casing string assembly. The drive assembly may
be run in hole with the casing string assembly. Where this is the
case, the drive assembly may be located in the casing string
assembly at surface.
[0023] The method may include the step of retrieving the drive
assembly from the casing string assembly. In this way, after the
reaming operation is complete, for example when no further reaming
is required due to formation conditions or because the casing
string has reached its casing point, the drive assembly can be
retrieved to surface.
[0024] The drive assembly may be retrieved using a wireline fishing
tool. Alternatively, the drive assembly may be retrieved using
drill pipe. In a further alternative, the drive assembly may be
retrieved by reverse circulation of the fluid in the wellbore to
pump the drive assembly upward in the well.
[0025] In a preferred embodiment, the method includes the step of
locating the drive assembly with respect to the casing string when
the casing string has been at least partially run into the
wellbore.
[0026] In this way, initial running of the casing could be by
floating the casing string into the wellbore. If difficulties are
experienced while running the casing in this fashion, for example,
if the casing string stands up on a rock ledge or a washout, the
drive assembly can be deployed through the casing string to locate
with respect to the swivel components.
[0027] The method may include the step of pumping the drive
assembly through the casing string. The drive assembly may comprise
a swab cup or wiper. In an alternative embodiment, the drive
assembly is run on drill pipe.
[0028] The method may include the additional step of engaging first
and second portions of the casing string assembly with the driving
assembly. The first and second portions of the casing string
assembly may be rotationally keyed with corresponding portions of
the drive assembly.
[0029] The method may include the additional step of rotating the
casing string during running. That is, the casing string could be
run as a conventional casing reamer over distances or through
formation for which casing reaming is achievable and desirable. If
difficulties are encountered, for example, if the reaming shoe
stands up on a ledge or washout and sufficient torque is not
available to continue the casing reaming operation, or
alternatively, if the frictional wear on the casing string poses a
risk of damage to the string, the equipment could then perform in
its swivel mode, with just a portion of the casing string being
rotated.
[0030] In an alternative embodiment, the first portion includes a
drill shoe or drill bit, and the method is implemented as a
casing-while-drilling operation.
[0031] The method may include the additional step of preventing
rotation of the first portion of the casing string assembly with
respect to the second portion. Preferably, the first portion of the
casing string assembly is locked with respect to the second
portion.
[0032] The method may include the additional step of cementing the
casing. The cementing of the casing may prevent rotation of the
first portion of the casing string assembly with respect to the
second portion. The first and second portions of the casing string
assembly may thereby be locked by a cementing operation.
[0033] The method may include the additional step of drilling
beyond the casing string assembly.
[0034] Advantageously, all components of the casing string assembly
left downhole are drillable or millable by conventional drilling
apparatus.
[0035] The method may include the additional step of drilling
through the drive assembly. The drive assembly may be a drillable
or millable downhole motor. The drive assembly may be integral with
the casing string assembly.
[0036] The method may include the steps of: [0037] running the
drive assembly with the casing; and [0038] cementing the casing
with the drive assembly downhole.
[0039] The method may include the steps of running a float collar
with the casing, above the drive assembly.
[0040] According to a second aspect of the invention, there is
provided a method of running a completion string in a wellbore, the
method comprising the steps of: [0041] providing a completion
string assembly in a wellbore, the completion string assembly
having a first portion and a second portion; and [0042] rotating a
first portion of the completion string assembly relative to a
second portion of the completion string assembly while running the
completion string.
[0043] The completion string may be tubular including liners, sand
control screens, slotted liners, expandable tubulars or casing.
These strings may be referred to as lower completion strings or
openhole completion strings. Embodiments of the second aspect of
the invention are as embodiments of the first aspect, with
references to casing string changed to completion string
accordingly.
[0044] According to a third aspect of the invention, there is
provided apparatus for connection to a tubular forming part of a
completion string, the apparatus comprising an upper section
adapted to be coupled to the completion string; a lower section
rotatable with respect to the upper section and adapted to be
coupled to equipment located below the tubular; and engaging means
corresponding to engaging means provided on a drive assembly
adapted to be coupled to the apparatus to allow rotation to be
imparted to the lower section, wherein the apparatus is operable to
be engaged or disengaged with the drive assembly in the
wellbore.
[0045] Preferably, the apparatus is operable to be engaged or
disengaged with the drive assembly in the wellbore to allow the
drive assembly to be run into the wellbore or retrieved from the
wellbore separately from the apparatus.
[0046] Preferably, the engaging means arranged to be rotationally
keyed on engagement with the corresponding engaging means.
Preferably, the engaging means comprises a plurality of
splines.
[0047] Preferably, the apparatus includes an upper spline section,
a lower spline section, and a bearing portion.
[0048] Preferably, the apparatus is adapted to have a rotating mode
and a non-rotating mode. The bearing portion may be operable to
rotate under load or under pressure. In one embodiment, the
apparatus is provided with means for preventing rotation of the
upper portion with respect to the lower portion. Preferably, the
upper and lower portions of are provided with formations which are
lockable by a cementing operation.
[0049] The apparatus may be adapted to be coupled to a shoe, such
as a casing reamer shoe or drill shoe.
[0050] According to a fourth aspect of the invention, there is
provided a drive assembly for a downhole apparatus, the drive
assembly comprising a main body portion and a rotating portion and
a motor for effecting rotation of the rotating portion with respect
to the main body portion; wherein the drive assembly comprises
engaging means for engagement of the main body portion and the
rotating portion with corresponding engaging means provided on the
downhole apparatus to allow rotation to be imparted to the downhole
apparatus, and the drive assembly is operable to be engaged or
disengaged with the downhole apparatus in the wellbore.
[0051] Preferably, the drive assembly is operable to be engaged or
disengaged with the downhole apparatus in the wellbore to allow the
drive assembly to be run into the wellbore or retrieved from the
wellbore separately from the downhole apparatus.
[0052] Preferably, the engaging means arranged to be rotationally
keyed on engagement with the corresponding engaging means.
Preferably, the engaging means comprise a plurality of splines.
[0053] In one embodiment, the drive assembly comprises a fluid
circulation path therethrough. Preferably, the motor is a positive
displacement motor or mud motor.
[0054] The drive assembly may be adapted to be run in and/or
retrieved from a completion string, such as a casing string. The
drive assembly may be adapted to be received in a shoe assembly of
a completion string. Preferably, the drive assembly is adapted to
be received in a shoe assembly to allow rotation of the shoe to be
driven by the drive assembly.
[0055] In one embodiment, the drive assembly is adapted to be
pumped downhole. Preferably, the drive assembly comprises a
resilient member for providing a seal with a completion string,
against which the drive assembly is pumped. Preferably, the drive
assembly comprises a swab cup or wiper.
[0056] The drive assembly may be provided with means for preventing
fluid flow through its circulation path. Such means may be a
rupture disc assembly. In this way, a sufficient increase in
pressure will rupture the disc and open the circulation path, and
allow the motor to be activated.
[0057] The drive assembly may comprise a wireline fishing neck.
[0058] According to a fifth aspect of the invention, there is
provided an assembly comprising the apparatus of the third aspect
of the invention, and the drive assembly of the fourth aspect of
the invention.
[0059] According to a sixth aspect of the invention, there is
provided apparatus for running a casing string, the apparatus
comprising an upper section adapted to be coupled to the casing
string; a lower section rotatable with respect to the upper section
and including a shoe located below the tubular; and engagement
means for engaging a drive assembly adapted to rotate the shoe with
respect to the upper section.
[0060] According to a seventh aspect of the invention there is
provided a drive assembly for a downhole apparatus comprising an
upper section adapted to be coupled to a tubular; a lower section
rotatable with respect to the upper section; and a motor for
imparting rotation to the lower section; wherein the drive assembly
is drillable or millable by conventional downhole drilling
equipment.
[0061] Preferably, the motor is a positive displacement motor such
as a mud motor. More preferably, the motor comprises a drillable or
millable rotator. The rotator may be made from a drillable alloy.
The motor may comprise a stator formed from a rubber or nitrile
rubber material.
[0062] The drive assembly may be provided with a fluid circulating
path for actuating the motor and a fluid bypass path. The fluid
bypass path may be provided with a rupture disc. In this way, the
rupture disc prevents fluid flow through the bypass channel until
pressure behind the disc is sufficient to break the disc.
[0063] Preferably, the lower section is connected to a shoe, such
as a casing reamer shoe or a drill shoe. More preferably, the show
is drillable or millable by conventional downhole drilling
equipment. The shoe may include a non-return valve to prevent fluid
flow into the shoe from the wellbore.
[0064] In one embodiment, the drive assembly is adapted to have a
rotating mode and a non-rotating mode. A bearing portion may be
operable to rotate under load or under pressure. In one embodiment,
the drive assembly is provided with means for preventing rotation
of the upper portion with respect to the lower portion. Preferably,
the upper and lower portions of are provided with formations which
are lockable by a cementing operation.
[0065] It will be appreciated that where the terms `up` and `down`
are used in this specification, they are used in a relative sense
and the invention could equally apply to deviated or horizontal
wellbores, in which case the references would convert
accordingly.
[0066] There will now be described by way of example only, various
embodiments of the invention with reference to the following
drawings, of which:
[0067] FIG. 1 is a schematic representation of a shoe assembly
according to an embodiment of the invention;
[0068] FIGS. 2A and 2B are schematic representations of a drive
assembly, used in accordance with the apparatus of FIG. 1;
[0069] FIGS. 3A, 3B, and 3C show the apparatus of FIGS. 1 and 2 at
different stages of running;
[0070] FIG. 4 is a schematic representation of a shoe assembly in
accordance with a second embodiment of the invention;
[0071] FIG. 5 is a schematic representation of a casing string
comprising the shoe assembly of FIG. 4.
[0072] Referring firstly to FIG. 1, there is shown in schematic
form a shoe assembly, generally depicted at 10, at its downhole
end. The apparatus is shown in half section in order to reveal
internal components. At an upper end 12, the apparatus 10 is
connected to a casing string (not shown). The apparatus includes an
upper spline section 16, which comprises longitudinally oriented
internal splines 17, protruding radially inward from the inner wall
of the section, and spaced circumferentially around the inner bore
34 of the apparatus. Bearing assembly 18 is coupled to the upper
spline section 16, in this case via an optional spacer section 20,
and provides a downhole swivel. The bearing assembly comprises
upper and lower bearing portions, respectively 22a and 22b, and a
bearing housing 24 functioning to keep the bearing assembly
together. Upper and lower bearing portions 22a and 22b are rotated
with respect to one another.
[0073] Coupled to the lower bearing portion is a lower spline
section 26, which in turn is coupled to shoe 28. The lower spline
section 26 comprises longitudinally oriented internal splines 27,
protruding radially inward from the inner wall of the section, and
spaced circumferentially around the inner bore 34 of the apparatus.
The shoe 28 in this example is a casing reaming shoe, having
abrasive portions 30 on its out surface. Internal to the shoe is a
dual non-return valve arrangement 32 allowing one-way flow of
circulating fluid from the internal bore 34 of the apparatus
through the shoe 28 and out through the jets 36.
[0074] Referring now to FIGS. 2A and 2B, there is shown a drive
assembly, generally depicted at 50, for use with the apparatus of
FIG. 1. FIG. 2B shows a continuation of the same of the drive
assembly 50, in half section to show internal components.
[0075] The drive assembly 50 comprises a main cylindrical body 52,
shown predominantly in FIG. 2A, and an upper end 54, shown in FIG.
2B. The drive assembly is dimensioned to fit inside the internal
bore of the apparatus 10. The upper end 54 comprises a wireline
fishing neck 56, but could be provided with any other suitable
retrieval means. Provided in the body 52 at the upper end 54 are
inlet ports for entry of circulating fluid. In this embodiment, a
rupture disc assembly 58 is provided internal to the body 52. The
drive assembly 50 is also provided with a swab cup 59 made of
resilient material to form a seal with the inner wall of the
casing.
[0076] The drive assembly further comprises an upper spline sub 60,
comprising a plurality of longitudinally oriented splines 62,
extending radially from the outer surface of the upper spline sub.
The splines 62 are distributed circumferentially around the upper
spline sub 60, and are arranged to complement and engage with the
splines 17 of the upper spline section 16.
[0077] Beneath the upper spline sub 60 is a housing 64 for a mud
motor, rotationally coupled to a lower spline sub 66 via a bearing
assembly 68. The spline sub 66 comprises splines 70, distributed
circumferentially around the lower spline sub 66, and arranged to
complement and engage with the splines 27 of the lower spline
section 16.
[0078] At the lower end 72 of the drive assembly 50 there are
provided a plurality of outlet ports for circulating fluid.
[0079] In use, the drive assembly 50 fits inside of the apparatus
10, such that the upper spline sub 60 is rotationally keyed with
the upper spline section 16, and the lower spline sub 66 is
rotationally keyed with the lower spline section 26. When fluid is
circulated in the mud motor 64 by pumping from surface, the lower
spline sub 66 is rotated with respect to the main body 52. The
upper spline sub 60 becomes a reactive torque sub with the upper
spline section 16 acting as a reactive torque section of the
apparatus 10, against which the lower spline sub 66 rotates. The
rotation of the sub 66 causes rotation of the casing reaming shoe
28.
[0080] In the embodiment of FIGS. 1, 2A and 2B, the apparatus is
adapted to be run into the casing to the apparatus 10 in a
subsequent run, when the apparatus 10 is already downhole. The
running method will be described with reference to FIGS. 3A to 3C,
each of which shows schematically the apparatus 10, 50 at a
different stage of running in a pre-drilled bore 100.
[0081] In FIG. 3A, the apparatus 10 has been run into bore 100 on
the downhole end of a casing string 110. The apparatus 10 is
connected to the casing string 110 via an optional spacer section
120. The casing string is provided with a landing collar 122 for
landing a cementing plug, which is a non-float collar.
[0082] The casing string and apparatus 10 has been run to a first
depth A conventionally. During this stage of running, the casing
string might not be rotated in the bore, or the casing string could
be run as a conventional casing reamer over distances or through
formation for which casing reaming is achievable and desirable. At
depth A, difficulties are encountered, for example, the reaming
shoe has stood up on a ledge or washout and sufficient torque is
not available to continue the casing reaming operation.
Alternatively, the operator may decide that frictional wear on the
casing string poses a risk of damage to the string. The operator
elects to run the drive assembly 50.
[0083] As shown in FIG. 3B, the drive assembly 50 into the casing.
The swab cup 59 provides a seal with the casing wall and along with
the resistance provided by the rupture disc assembly 58, allows the
drive assembly 50 to be pumped downhole in the direction of arrow
B. The drive assembly 50 and landing collar 122 are selected to
allow the drive assembly to pass the collar. When the drive
assembly 50 locates in the apparatus, the splines of the respective
spline subs 60, 66 and spline sections 16, 26 are rotationally
keyed, and the lower end 72 abuts a formation in the apparatus 10.
The pump pressure breaks the rupture disc assembly 58 and fluid
circulates in the drive assembly. The mud motor 64 causes the lower
spline sub 66, the lower spline section 26, and shoe 28 to rotate
against the portions of the apparatus above the bearing portions.
Downweight on the casing string 110 allows the depth of the casing
to be increased to the casing point while reaming the bore 100, as
indicated by arrow C.
[0084] When the reaming operation is complete, the pump pressure is
bled off and the wireline fishing neck 56 allows the drive assembly
50 to be retrieved from the casing prior to cementing.
[0085] The above-described method and apparatus allows casing
reaming without rotating the entire casing string, and in a manner
in which the only components left downhole may be drilled through
if the wellbore is to be drilled beyond the casing point. In
addition, the method and apparatus provides for elective deployment
and/or retrieval of the driving assembly.
[0086] To assist in drilling out the apparatus, an alternative,
non-illustrated embodiment of the invention provides a bearing
assembly that has rotating and non-rotating states. For example,
the bearing assembly may include a mechanism that is configured
such that it only allows rotation when under a load or under
pressure. In an alternative embodiment, portions of the apparatus
attached to the upper and lower bearing portions are profiled or
ribbed such that after the cement job has been carried out,
relative rotation of the components is prevented or mitigated.
[0087] In an alternative, non-illustrated embodiment, the drive
assembly is run in with the casing string 110, and not pumped down
in a separate operation. In this embodiment, the drive assembly is
substantially identical to that of FIGS. 2A and 2B, but the swab
cup 59 and rupture disc assembly 58 will not be required and may be
omitted. The drive assembly is located with respect to the spline
sections at surface, and run into the bore together with the
casing. If reaming is required, circulating fluid is pumped down
from surface and the mud motor effects rotation of the shoe to ream
the hole. Subsequent to the reaming operation the drive assembly
can be retrieved from the casing, although it could be left
downhole. However, it is preferable in most casing running
applications to avoid leaving equipment downhole that is difficult
to drill out, should the depth of the bore be increased beyond the
casing point.
[0088] In a further embodiment of the invention the driving
assembly is run on a wireline subsequent to running of the casing
section.
[0089] In a further, non-illustrated embodiment of the invention,
the landing collar 122 is modified to provide a profile that
maximises its contact area for landing a cementing plug, but allows
passage of the driving assembly. The landing collar could for
example comprise portions of increased inner diameter to allow
passage of the splines of the driving assembly. In a further
alternative embodiment, the reduced inner diameter of the upper
spline section functions as a landing collar for a cementing
plug.
[0090] Referring now to FIG. 4, there is shown in schematic form a
shoe and motor assembly in accordance with an alternative
embodiment of the invention, generally depicted at 200. The
apparatus is shown in half section in order to reveal internal
components. At an upper end 212, the apparatus 200 is connected to
a casing string (not shown). The apparatus includes an upper
section 216 and a lower section 226 via a bearing assembly 218 to
provide a downhole swivel. The bearing assembly 218 comprises upper
and lower bearing portions, respectively 222a and 222b, and a
bearing housing 224 functioning to keep the bearing assembly
together. Upper and lower bearing portions 222a and 222b are
rotatable with respect to one another.
[0091] The lower portion 226 is connected to shoe, in this case a
standard reamer shoe 228 having tungsten carbide reaming portions
230 and stabilising portions 234. The shoe 228 includes a
non-return valve 232 to prevent backflow of circulation fluid.
[0092] The upper section 216 houses a drillable or millable motor
240. The motor 240 includes a stator 242 coupled to, and static in
relation to, the upper portion 216. The stator is made from a
rubber or nitrile rubber material, having the properties of being
elastically deformable, but resistant to wellbore and circulation
fluids. The motor also comprises a rotator 244, concentric with the
stator 242, and formed from a drillable or millable alloy. The
rotator 244 comprises a main body portion 246 and a lower body
portion 248, coupled to the lower portion 226 of the assembly by a
threaded connection. Fluid ports 250 are provided in the lower body
portion 248. As is understood in the art, the stator and rotator
are profiled on their inner and outer surfaces respectively, such
that fluid pumped through the motor causes rotation of the rotator
with respect to the stator. Such rotation is transferred to the
lower portion of the assembly and the shoe.
[0093] The assembly is also provided with a bypass bore 252 and a
rupture disc 254. Should the motor block or jam, the pressure build
up behind the motor will cause the disc to rupture and open the
bore 252 for passage of fluid.
[0094] The components of the drive assembly are selected to be
readily drillable or millable using conventional drilling
equipment. Similarly, the components of the show 228 are readily
drillable or millable. This allows the apparatus to be left
downhole, even in applications where subsequent drill-out, for
example to extend the wellbore beyond the casing point, is
required. This arrangement also allows the drive assembly to be
integral with the shoe assembly.
[0095] To assist in drilling out the apparatus, an alternative,
non-illustrated embodiment of the invention provides a bearing
assembly that has rotating and non-rotating states, as described
with reference to FIG. 1. For example, the bearing assembly may
include a mechanism that is configured such that it only allows
rotation when under a load or under pressure. In an alternative
embodiment, portions of the apparatus attached to the upper and
lower bearing portions are profiled or ribbed such that after the
cement job has been carried out, relative rotation of the
components is prevented or mitigated.
[0096] FIG. 5 shows schematically a representation of a casing
string 308 comprising the shoe assembly of FIG. 4 in a bore 300. In
this arrangement, the drive assembly 240 is integral with the
casing string assembly on run in, and is coupled at its upper end
to a casing section 302. Further casing section 304 is provided
with a float collar 306 for catching a cementing plug and providing
a non-return valve. The use of the float collar is made possible
because the drive assembly does not require separate deployment or
retrieval.
[0097] Various modifications and improvements could be made to the
above-described embodiments of the invention within the scope of
the invention herein defined.
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