U.S. patent application number 10/809036 was filed with the patent office on 2004-11-04 for tubing expansion.
Invention is credited to Rudd, Wayne, Simpson, Neil Andrew Abercrombie.
Application Number | 20040216506 10/809036 |
Document ID | / |
Family ID | 32232407 |
Filed Date | 2004-11-04 |
United States Patent
Application |
20040216506 |
Kind Code |
A1 |
Simpson, Neil Andrew Abercrombie ;
et al. |
November 4, 2004 |
Tubing expansion
Abstract
A method of expanding tubing comprises locating an expansion
device in tubing to be expanded, vibrating one or both of the
tubing and the expansion device, and translating the expansion
device relative to the tubing, the vibration acting to reduce
friction between the tubing and the device.
Inventors: |
Simpson, Neil Andrew
Abercrombie; (Aberdeen, GB) ; Rudd, Wayne;
(Newcastle Upon Tyne, GB) |
Correspondence
Address: |
WILLIAM B. PATTERSON
MOSER, PATTERSON & SHERIDAN, L.L.P.
Suite 1500
3040 Post Oak Blvd.
Houston
TX
77056
US
|
Family ID: |
32232407 |
Appl. No.: |
10/809036 |
Filed: |
March 25, 2004 |
Current U.S.
Class: |
72/370.06 |
Current CPC
Class: |
E21B 43/105
20130101 |
Class at
Publication: |
072/370.06 |
International
Class: |
B21D 039/08 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 25, 2003 |
GB |
0306774.1 |
May 29, 2003 |
GB |
0312278.5 |
Claims
1. A method of expanding tubing, the method comprising: locating an
expansion device in tubing to be expanded; vibrating at least one
of the tubing and the expansion device; and translating the
expansion device relative to the tubing.
2. The method of claim 1, wherein the nature of the vibration of at
least one of the tubing and the expansion device is selected to
reduce friction between the tubing and the device.
3. The method of claim 2, wherein the vibration of at least one of
the expansion device and the tubing is selected to substantially
avoid static friction between contacting surfaces of the expansion
device and the tubing.
4. The method of claim 1, wherein a driving force is applied to
translate the expansion device through the tubing.
5. The method of claim 4, wherein the driving force remains
substantially constant as the expansion device is translated
through the tubing.
6. The method of claim 1, wherein the direction of the vibration
includes an element selected from at least one of: random,
multi-directional, axial, transverse and rotational.
7. The method of claim 1, wherein at least a major portion of the
expansion device is subject to vibration.
8. The method of claim 1, wherein only a selected portion of the
expansion device is subject to vibration.
9. The method of claim 8, wherein a surface portion of the device
is subject to vibration.
10. The method of claim 1, wherein portions of the expansion device
experience different forms of vibration.
11. The method of claim 1, wherein at least a substantial portion
of the tubing is vibrated.
12. The method of claim 1, wherein only a selected portion of the
tubing is vibrated.
13. The method of claim 12, wherein a portion of the tubing
adjacent the expansion device is vibrated.
14. The method of claim 12, wherein a surface portion of the tubing
is vibrated.
15. The method of claim 1, wherein the vibration induces physical
movement of at least one of the expansion device and tubing.
16. The method of claim 1, wherein the vibration induces
contraction and expansion of at least a portion of at least one of
the expansion device and the tubing.
17. The method of claim 1, wherein the vibration takes the form of
at least one wave traveling through at least one of the expansion
device and the tubing.
18. The method of claim 1, wherein the vibration is created locally
relative to the tubing being expanded.
19. The method of claim 1, wherein the vibration is created
remotely of a tubing expansion location, and travels to the
expansion location.
20. The method of claim 1, comprising creating the vibration with a
moving mass.
21. The method of claim 1, comprising creating the vibration by
providing a varying restriction to fluid flowing through at least
one of the expansion device and the tubing.
22. The method of claim 1, comprising creating the vibration with
an electromagnetic oscillator.
23. The method of claim 1, comprising creating the vibration by
varying the pressure of fluid operatively associated with at least
one of the device and the tubing.
24. The method of claim 1, comprising creating the vibration by
creating pressure pulses in a fluid operatively associated with at
least one of the device and the tubing.
25. The method of claim 1, comprising creating the vibration by
injecting fluid into fluid operatively associated with at least one
of the device and the tubing.
26. The method of claim 1, comprising coupling a source of
vibration to at least one of the expansion device and the
tubing.
27. The method of claim 26, comprising directly coupling a source
of vibration to at least one of the expansion device and the
tubing.
28. The method of claim 26, comprising indirectly coupling a source
of vibration to at least one of the expansion device and the
tubing.
29. The method of claim 1, wherein the amplitude of the vibration
is selected from at least one of constant, varying and random
amplitude.
30. The method of claim 1, wherein the frequency of the vibration
is selected from at least one of constant, varying and random
frequency.
31. The method of claim 1, wherein the form of the vibration is
selected from at least one of constant, varying and random
form.
32. The method of claim 1, wherein the vibration is of high
frequency.
33. The method of claim 32, wherein the vibration is
ultrasonic.
34. The method of claim 1, wherein the form of the vibration is
selected such that the vibration is not apparent as physical
movement.
35. The method of claim 1, wherein the vibration is induced
electromagnetically.
36. The method of claim 1, wherein the vibration is of relatively
low frequency.
37. The method of claim 36, wherein the vibration is in the range
of 1 to 100 Hz.
38. The method of claim 1, wherein the vibration comprises a
plurality of different components.
39. The method of claim 38, wherein the vibration comprises a low
frequency component and a high frequency component.
40. The method of claim 1, wherein the vibration is selected to
coincide with a natural frequency of at least one of the expansion
device and the tubing.
41. The method of claim 1, wherein the vibration is selected to
avoid a natural frequency of at least one of the expansion device
and the tubing.
42. The method of claim 1, comprising applying a driving force to
the expansion device to translate the expansion device relative to
the tubing.
43. The method of claim 1, comprising applying a mechanical driving
force to translate the expansion device relative to the tubing.
44. The method of claim 43, wherein the driving force comprises at
least one of a pulling, pushing and torsional force.
45. The method of claim 1, comprising applying a fluid pressure
driving force to translate the expansion device relative to the
tubing.
46. The method of claim 1, wherein the expansion device is in
sliding contact with the tubing.
47. The method of claim 1, wherein the expansion device is in
rolling contact with the tubing.
48. The method of claim 1, wherein the expansion device is
translated axially relative to the tubing.
49. The method of claim 1, wherein the expansion device is
translated rotationally relative to the tubing.
50. The method of claim 1, comprising expanding the tubing by
creating localized compressive yield in the tubing wall.
51. The method of claim 1, comprising varying the diameter of the
expansion device.
52. The method of claim 1, further comprising creating a pressure
differential across a wall of the tubing.
53. The method of claim 52, wherein the pressure differential
applied across the tubing wall is varied.
54. The method of claim 53, wherein the pressure differential is
cycled.
55. The method of claim 1, comprising isolating a volume of fluid
containing the expansion device.
56. A method of expanding tubing, the method comprising: locating
an expansion device in tubing to be expanded; vibrating the
expansion device; and translating the expansion device relative to
the tubing.
57. Apparatus for expanding tubing, the apparatus comprising: an
expansion device; and means for vibrating at least one of the
tubing and the expansion device.
58. The apparatus of claim 57, further comprising means for
translating the expansion device relative to the tubing.
59. The apparatus of claim 57, wherein the vibrating means is
operable to reduce friction between the tubing and the expansion
device.
60. The apparatus of claim 57, wherein the vibrating means is
operable to avoid static friction between contacting surfaces of
the tubing and the expansion device.
61. The apparatus of claim 57, wherein the vibrating means is
operable to vibrate at least a major portion of at least one of the
device and the tubing.
62. The apparatus of claim 57, wherein the vibrating means is
operable to vibrate a selected portion of at least one of the
expansion device and the tubing.
63. The apparatus of claim 57, wherein the vibrating means
comprises at least one of: a movable mass; a variable fluid flow
path through at least one of the expansion device and tubing; an
electromagnetic oscillator; means for varying the pressure of fluid
operatively associated with at least one of the device and tubing;
means for creating pressure pulses in a fluid; and means for
injecting a fluid into fluid operatively associated with at least
one of the expansion device and the tubing.
64. The apparatus of claim 57, wherein the vibrating means is
directly coupled to at least one of the expansion device and the
tubing.
65. The apparatus of claim 57, wherein the vibrating means is
indirectly coupled to at least one of the expansion device and the
tubing.
66. The apparatus of claim 57, wherein the expansion device
comprises an expansion cone.
67. The apparatus of claim 66, wherein the expansion cone is
adapted for sliding contact with the tubing.
68. The apparatus of claim 66, wherein the expansion cone is
adapted for rolling contact with the tubing.
69. The apparatus of claim 57, wherein the expansion device
comprises a rotary expander.
70. The apparatus of claim 57, wherein the expansion device defines
a fixed expansion diameter.
71. The apparatus of claim 57, wherein the expansion device
comprises a variable expansion diameter.
72. The apparatus of claim 57, wherein the expansion device is
compliant.
73. The apparatus of claim 57, further comprising means for
creating a pressure differential across a tubing wall adjacent the
expansion device.
74. The apparatus of claim 57, further comprising means for
creating a varying pressure differential across a tubing wall
adjacent the expansion device.
75. The apparatus of claim 57, comprising means for isolating a
volume of fluid containing the expansion device.
76. The apparatus of claim 75, wherein said isolating means
comprises at least one seal.
77. The apparatus of claim 76, where the seal comprises a plurality
of seal members.
78. The apparatus of claim 76 or 77, wherein said seal is adapted
to permit a degree of leakage thereacross.
79. Apparatus for expanding tubing, the apparatus comprising: an
expansion device; and means for vibrating the expansion device.
80. Apparatus for expanding tubing, the apparatus comprising: an
expansion device; and a vibration inducing device operatively
associated with at least one of the tubing and the expansion
device.
81. Apparatus for expanding tubing, the apparatus comprising: an
expansion device; and a vibration inducing device operatively
associated with the expansion device.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims benefit of Great Britain patent
application serial number GB 0306774.1, filed Mar. 25, 2003, and
Great Britain patent application serial number GB 0312278.5, filed
May 29, 2003, which is herein incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention relates to tubing expansion. In particular,
but not exclusively, the invention relates to diametric expansion
of tubing downhole.
[0004] 2. Description of the Related Art
[0005] One of the most significant recent developments in the oil
and gas exploration and production industry has been the
introduction of technology which allows for expansion of extended
sections of tubing downhole. The tubing may take different forms,
including but not restricted to: expandable casing, liner,
sandscreen, straddles, packers and hangers. A variety of expansion
methods have been proposed, including use of expansion cones or
mandrels which are forced through the tubing. One difficulty which
has been experienced with cone expansion is the high level of
friction and wear between the surface of the cone and the inner
surface of the tubing to be expanded.
[0006] It is among the objectives of embodiments of the present
invention to obviate or mitigate this difficulty.
SUMMARY OF THE INVENTION
[0007] According to the present invention there is provided a
method of expanding tubing, the method comprising:
[0008] locating an expansion device in tubing to be expanded;
[0009] vibrating at least one of the tubing and the expansion
device; and
[0010] translating the expansion device relative to the tubing.
[0011] The vibration of at least one of the tubing and the
expansion device preferably acts to reduce friction between the
tubing and the device.
[0012] In conventional tubing expansion operations an expansion
device which slides relative to the tubing to be expanded, such as
a cone or mandrel, will tend to progress through the tubing
incrementally in a series of small steps. From a static condition,
the load on the cone is increased until the load is sufficient to
drive the cone through the tubing. In addition to the forces
required to expand the tubing diametrically, it is also necessary
to overcome the static friction between the contacting surfaces of
the cone and the tubing before the cone will move relative to the
tubing. Once static friction has been overcome, frictional
resistance to movement typically decreases sharply due to the lower
dynamic friction between the contacting surfaces, such that the
initial movement of the cone will tend to be relatively rapid. As
the cone moves forward rapidly relative to the tubing, the driving
force being applied to the cone will tend to fall, the inertia of
the cone-driving arrangement being such that the cone-driving
arrangement will typically fail to keep pace with the cone. Thus,
after the initial rapid movement, the cone will tend to stall as
the driving force decreases. The driving force applied to the cone
then increases once more, moving the cone forward again once static
friction between the cone and tube is overcome. For brevity, this
form of movement will hereinafter be referred to as
"stick-slip".
[0013] With the present invention, the vibration of one or both of
the expansion device and the tubing is intended such that there
will be little or no static friction experienced between the
contacting surfaces, and the conventional stick-slip progression of
the expansion device relative to the tubing should be avoided. The
driving force necessary to drive the expansion device through the
tubing should therefore remain relatively constant, as the
frictional forces remain at a relatively constant, and relatively
low, level.
[0014] Furthermore, the reduction in friction between the expansion
device and the tubing should tend to decrease the wear experienced
by the expansion device, which in conventional expansion operations
may place limits on the length of tubing which can be expanded in a
single expansion operation.
[0015] Of course, in downhole applications, the vibration may also
serve to assist in reducing the occurrence of differential sticking
between the tubing and the surrounding bore wall.
[0016] The frequency and amplitude of vibration may be selected to
suit each particular application. Furthermore, the direction of
vibration may be selected as appropriate: for example, the
vibration may be random, multi-directional, axial, transverse or
rotational. In one embodiment of the invention the vibration is
substantially perpendicular to the surface of the expansion device,
and in another embodiment the vibration takes the form of torsional
oscillations.
[0017] Where the expansion device is vibrated, all or a major
portion of the device may be subject to vibration. Alternatively,
only a selected portion of the device may be subject to vibration,
for example only a surface portion of the device, or only a
selected area of the surface of the device, may be subject to
vibration. Portions of the expansion device may also experience
different degrees or forms of vibration.
[0018] If the tubing is vibrated, all or a substantial portion of
the tubing may be vibrated. Alternatively, only a selected portion
of the tubing may be vibrated. For example, only a portion of the
tubing at or adjacent the expansion device may be vibrated, or only
a surface portion of the tubing may be vibrated.
[0019] The vibration of the expansion device or tubing may induce
physical movement of the device or tubing. Alternatively, or in
addition, the vibration of the device or tubing may induce
contraction and expansion of all or a portion of the device or the
tubing. For example, the vibration may take the form of one or more
waves traveling through the device or tubing.
[0020] The vibration of the expansion device or tubing may induce
physical movement of the device or tubing. Alternatively, or in
addition, the vibration of the device or tubing may induce
contraction and expansion of all or a portion of the device or the
tubing. For example, the vibration may take the form of one or more
waves traveling through the device or tubing.
[0021] The vibration may be induced or created locally relative to
the expansion device or the tubing being expanded, or may be
created remotely, for example a wave form oscillation may be
created remote from the expansion device location, and then travel
along or through the tubing wall, or travel to the expansion
location via another medium.
[0022] The vibration may be created by any appropriate means,
including: an oscillating or otherwise moving mass; creating a
varying or cyclic restriction to fluid flowing through the
expansion device or tubing; an electromagnetic oscillator; varying
the pressure of fluid operatively associated with the device or
tubing; creating pressure pulses in a fluid; or injecting gas or
liquid or a mixture of both into fluid operatively associated with
the device or tubing.
[0023] The source of vibration or oscillation may be directly or
indirectly coupled to one or both of the expansion device and the
tubing.
[0024] The vibration may be of a constant, varying or substantially
random nature, that is the amplitude, direction, frequency and form
of the vibration may be constant, varying or random.
[0025] The vibration or oscillation may be of high frequency, for
example ultrasonic. Such vibration may not be apparent as physical
movement, as the vibration may be at a molecular or macromolecular
level, or at least at a level below that of readily detectable
physical movement of the device or tubing. Such vibration may be
induced electromagnetically, for example by a varying
electromagnetic field, or a varying or alternating current or
voltage. Alternatively, or in addition, the vibration or
oscillation may be of relatively low frequency, for example in the
range of 1 to 100 Hz. If desired, the vibration may comprise a
plurality of different components, for example a low frequency
component and a high frequency component.
[0026] The vibration may be selected to coincide with a natural
frequency of the expansion device or the tubing, or another element
of apparatus. Alternatively, the vibration may be selected to avoid
such natural frequency or frequencies.
[0027] The expansion device may be translated relative to the
tubing by any appropriate means. The device may be mounted on a
support which allows the device to be pushed, pulled or otherwise
driven through the tubing. The support may extend from a downhole
location to surface, where a pushing, pulling or torsional force
may be applied. Alternatively, the expansion device may be coupled
to a tractor or other driving arrangement located downhole.
Alternatively, or in addition, fluid pressure may be utilised to
move the device relative to the tubing.
[0028] The expansion device may take any appropriate form and may
utilise any appropriate expansion mechanism, or a combination of
different expansion mechanisms. An expansion cone or mandrel may be
utilised with an expansion surface adapted for sliding or rolling
contact with the tubing wall. The cone may be adapted for axial
movement relative to the tubing, but may also be adapted for
rotation. Alternatively, or in addition, a rotary expander may be
utilised, that is a device which is rotated within the tubing with
at least one expansion member, typically a roller, moving around
the surface of the tubing and creating localised compressive yield
in the tubing wall, the resulting reduction in wall thickness
leading to an increase in tubing diameter.
[0029] The expansion device may define a fixed diameter, or a
variable diameter. The device may be compliant, that is the device
has a degree of flexibility to permit the device to, for example,
negotiate sections of the tubing which cannot be expanded to a
desired larger diameter or form. Alternatively, the expansion
device may define a fixed diameter and may be non-compliant. In
certain embodiments, the expansion device may feature both fixed
and compliant elements.
[0030] References herein to expansion are primarily intended to
relate to diametric expansion achieved by thinning of tubing wall.
However, embodiments of the invention may also relate to tubing
which is expanded by reforming a tubing wall, for example by
straightening or smoothing a corrugated tubing wall, or other
expansion mechanisms.
[0031] In other embodiments of the invention the expansion process
may be supplemented by the application of an elevated fluid
pressure, and in particular a varying fluid pressure, to the
tubing.
[0032] The varying fluid pressure preferably acts across the wall
of the tubing. The variation in pressure may be achieved by any
appropriate means, and one or both of the fluid pressure within the
tubing and the fluid pressure externally of the tubing may be
varied. A body of varying volume may be located in a volume of
fluid operatively associated with the tubing. Alternatively, or in
addition, the volume of a body of fluid operatively associated with
the tubing may be varied by movement of a wall portion defining a
boundary of the volume, which wall portion may be operatively
associated with an oscillator or a percussive or hammer device. In
other embodiments a pressurised fluid source may be provided, and
the fluid may be supplied at varying pressure from the source or
the manner in which the fluid is delivered to the tubing from the
source may be such as to vary the fluid pressure. An increase in
pressure within the tubing may be accompanied by a reduction in
pressure externally of the tubing, or a reduction of pressure
externally of the tubing may occur independently of any variations
in the internal pressure, which may remain substantially
constant.
[0033] In one embodiment, in a downhole application, the fluid
pressure externally of the tubing may be maintained at a relatively
low level by providing a relatively low density fluid externally of
the tubing. Thus, the hydrostatic pressure produced by the column
of fluid above the tubing will be relatively low. This may be
achieved by injecting gas or low density fluid into fluid
surrounding the tubing. Alternatively, or in addition, a volume of
fluid externally of the tubing may be at least partially isolated
from the head of fluid above the tubing, for example by means of a
seal or seals between the tubing and a surrounding bore or tubing
wall, or by providing pumping means above the tubing.
[0034] Alternatively, or in addition, the fluid pressure internally
of the tubing may be maintained at a relatively high level by
providing a relatively high density fluid internally of the
tubing.
[0035] Tubing expansion operations are typically carried out using
conventional, readily available fluids, such as seawater or
completion brine, which may have a specific gravity (SG) of
approximately 1.025. However, the SG of fluids used in downhole
operations of course varies depending on, for example, the choice
of base fluid and the presence of weight materials or other
additives, and may range from 0.85 to 2.2. Thus, references herein
to high and low density fluids should be related primarily to
fluids utilised in conventional tubing expansion operations and
other downhole operations where the fluid is selected with
reference primarily to other requirements, including availability
and ease of handling. Accordingly, by way of example, with
reference to expansion operations which, using conventional
expansion techniques, would be carried out in the presence of
completion brine, a high density fluid may be one having an SG in
excess of around 1.025 and a low density fluid may be one having an
SG less than around 1.025. In other cases, the density of a fluid
present within tubing to be expanded may be considered to be
relatively high if the fluid has been selected with reference to
the lower density of the fluid in the annulus surrounding the
tubing. Similarly, the density of a fluid in the annulus may be
considered to be relatively low if the density is lower than the
density of the fluid present within the tubing to be expanded. Of
course the invention is not limited to use with liquids, and in
some cases one or both of the fluids, particularly where a lower
density fluid is required, may be a gas such as natural gas or air,
or a multiphase fluid.
[0036] The portion of tubing to be expanded may be isolated from
ambient fluid by one or more appropriate seals, and a varying
pressure differential may be maintained across each seal. However,
in accordance with a further aspect of the invention a degree of
leakage past the seals may be permissible, and in some cases may
even be desirable, particularly if means for providing or creating
a cycling fluid pressure is being utilised; if the frequency or
rate of pressure variation is sufficiently high, a degree of
leakage, and the corresponding pressure decay, will not adversely
affect the expansion process and may assist in providing the
desired pressure cycling when combined with an appropriate source
of pressure. In particular, the method may include the step of
producing a pressure pulse, and thus an elevated fluid pressure,
which then reduces or decays, as leakage occurs across the seal.
Furthermore, the ability to utilise "leaky" seals tends to
facilitate use of the expansion method, as there are difficulties
involved in providing a fully effective seal in many environments:
when expanding tubing downhole, the tubing will often not be
perfectly cylindrical, and the tubing diameter may be variable; the
tubing surface is unlikely to be perfectly smooth, and may include
profiles; the ambient fluid in the tubing may contain particulates
and contaminants; and in preferred embodiments the seal will move
relative to the tubing as the tubing is expanded, which movement
would of course result in wear to one or both of the seal and the
tubing, and which movement would have to overcome friction, which
could be considerable if a leak-free seal was provided or required.
Also, the leakage of fluid around and over the seal will provide
lubrication, facilitating relative movement between the seal and
the tubing.
[0037] The seal may take any appropriate form, but is preferably in
the form of a labyrinth seal. Typically, the seal comprises a
plurality of seal members, each seal member adapted to maintain a
proportion of the total pressure differential across the seal. The
number of seal members may be selected depending upon a number of
considerations, including the form of the seal members, tubing form
and condition, ambient conditions, the pressure differential to be
maintained, tubing diameter, and the frequency or rate of variation
of the fluid pressure. Of course such a seal configuration may also
be suitable for use in situations where the fluid pressure is
substantially constant, or is maintained above at least a minimum
level, provided of course that means is provided for maintaining
the expansion pressure at the desired level, despite leakage past
the seal. Thus, perhaps five, ten, fifteen or more seal members may
be provided, as appropriate. The number of seal members may be
selected to provide for redundancy, such that failure or damage of
one or more seal members will not adversely affect the expansion
process.
[0038] The fluid pressure may be maintained at a base pressure, for
example at 70% of the yield pressure of the wall of the tubing,
upon which base pressure additional pressure pulses or spikes are
superimposed, taking the fluid pressure to or in excess of 100% of
the yield pressure, to induce plastic deformation of the
tubing.
[0039] The mechanical expansion or reforming device, such as an
expansion cone, mandrel or die, or a rotary expansion device, may
exert only a small expansion force, and may merely serve to
stabilise the expansion process and assist in achieving a desired
expanded form, for example achieving a desired expanded diameter
and avoiding ovality. Alternatively, or in addition, the mechanical
expansion or reforming device may serve to retain expansion induced
by the elevated fluid pressure. In one embodiment, a shallow angle
cone may be advanced through the expanding tubing, the cone
preferably being advanced in concert with the periods of elevated
pressure. The cone angle may be selected depending upon the
particular application, but for downhole tubulars of conventional
form it has been found that an 11 degree cone angle results in a
cone which retains expansion, that is the cone may be advanced into
the tubing expanded by the elevated pressure, and is then retained
in the advanced position as the tubing contracts on decay of the
fluid pressure below the tubing wall yield pressure. It is
anticipated that by cycling the fluid pressure at a rate of around
5 Hertz the cone will advance at a rate of approximately 6 to 8
feet per minute. Of course the rate or frequency of fluid pressure
variation may be selected to suit local conditions and equipment.
Such advancement may be achieved by providing separate mechanical
drive means but may be conveniently achieved by virtue of the
pressure differential over a seal coupled to the cone; as the
pressure peaks, causing expansion of the tubing, the axial
differential pressure acting force across the seal will also peak.
Where the cone is located between seals, in particular a leading
seal and a trailing seal, the leading seal may be mounted on the
cone or otherwise coupled to the cone such that any pressure
differential across the seal will tend to urge the cone forward.
The trailing seal may be located at some point behind the cone,
such that the cone is located within an isolated fluid volume
between the seals. The trailing seal may be fixable or securable
relative to the tubing or may be floating. The trailing seal may be
retained in position mechanically or, alternatively or
additionally, by fluid pressure, for example by a column of fluid
above the seal, which column may be pressurised by appropriate
pumps on surface. The variations in pressure are preferably applied
to the isolated fluid volume between the seals, and may be created
by a pulse generator located within the isolated volume, or by
supplying elevated pressure fluid or pressure pulses from a source
externally of the isolated volume. In other embodiments, variations
in pressure may also be applied to one or both of the fluid volumes
above and below the isolated volume.
[0040] Of course the presence of fluid will facilitate movement of
any expansion device present relative to the tubing, in particular
by serving as a lubricant between the contacting surfaces of the
expansion device and the tubing. The fluid may be selected for its
lubricating properties. This is particularly the case in
embodiments where the fluid surrounding the expansion device is at
least partially isolated from the ambient fluid, and as such a
smaller volume of fluid selected for its particular properties may
be provided. Leakage past isolating seals may be accommodated by
providing a larger initial volume, or by supplying further fluid to
the volume. Of course the fluid may be selected with properties
other than lubrication in mind, for example the fluid may comprise
or include a relatively viscous element, for example a grease, to
minimize the rate of leakage and pressure decay. Downhole expansion
may be accomplished either top down or bottom up, that is expansion
process moves downwardly or upwardly through the tubing.
BRIEF DESCRIPTION OF THE DRAWINGS
[0041] These and other aspects of the present invention will now be
described, by way of example, with reference to the accompanying
drawing, which a schematic illustration of a tubing expansion
operation, in accordance with a preferred embodiment of the present
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0042] The figure illustrates a subterranean bore 10, such as may
be drilled to gain access to a subsurface hydrocarbon reservoir.
After drilling, the bore 10 may be lined with metal tubing,
sometimes known as liner or casing. In the illustrated embodiment,
a section of expandable casing 12 has been run into the bore 10,
and once located in the bore 10 the casing 12 is expanded from a
smaller first diameter D1 to a larger second diameter D2.
[0043] The expansion is achieved by means of driving an expansion
cone 14 down through the casing 12, the cone 14 being mounted on a
string of drill pipe 16 which extends to surface. The force
necessary to drive the cone 14 through the casing 12 while
expanding the casing 12 is considerable: the force must be
sufficient to deform the casing 12 and also to overcome the
friction between the contacting surfaces of the cone 14 and the
casing 12. In conventional cone expansion operations the level of
friction experienced is such that the cone 14 will tend to progress
with an inefficient stick-slip movement, due in part to the
differences in static and dynamic friction experienced by the cone
14 as it is moved through the casing 12. However, in the present
invention, this difficulty is substantially avoided due to the
vibration of the cone 14 by means of an oscillator 18 mounted to
the cone 14. In use, the oscillator 18, which is powered from
surface via an appropriate control line, produces oscillations at
ultrasonic frequencies, which vibrations or oscillations are
transferred to the cone 14. This high frequency of vibration of the
cone 14 is such that there is substantially constant relative
movement between the contacting surfaces of the cone 14 and the
casing 12, such that there is no static friction experienced
between the contacting surfaces. Thus, the level of friction
between the cone 14 and the casing is relatively low, allowing the
cone 14 to progress through the casing 12 at a relatively constant
rate, in response to a relatively constant applied force.
[0044] It will be apparent to those of skill in the art that the
above-described embodiment is merely exemplary of the present
invention, and that various modifications and improvements may be
made thereto without departing from the scope of the present
invention.
[0045] In other embodiments, the casing 12 rather than the cone 14
may be vibrated, and the manner in which the vibration or
oscillation is created may be varied. For example, fluid may be
pumped through the drill pipe 16 and the fluid flow path may be
interrupted or varied to induce vibration. Alternatively, a stream
of gas may be injected into the fluid surrounding the cone 14,
causing vibration of one or both of the cone 14 and the casing
12.
[0046] In other embodiments of the invention translation of the
cone 14 through the casing may be achieved at least in part by
application of a fluid pressure, which fluid pressure may also
assist in expanding the casing 12. The fluid pressure may be varied
such as to vibrate one or both of the cone 14 or casing, or to
assist in the expansion of the casing, as described in greater
detail in our patent application GB 0306774.1 entitled
"Hydraulically Assisted Tubing Expansion", the disclosure of which
is incorporated herein by reference.
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