U.S. patent application number 12/745768 was filed with the patent office on 2011-11-03 for method of radially expanding a tubular element.
Invention is credited to Fu Joseph Hou, Petrus Cornelis Kriesels, Pieter Van Nieuwkoop.
Application Number | 20110266007 12/745768 |
Document ID | / |
Family ID | 39361297 |
Filed Date | 2011-11-03 |
United States Patent
Application |
20110266007 |
Kind Code |
A1 |
Hou; Fu Joseph ; et
al. |
November 3, 2011 |
METHOD OF RADIALLY EXPANDING A TUBULAR ELEMENT
Abstract
A method is provided of radially expanding a tubular element
extending into a wellbore formed in an earth formation, the method
comprising inducing the wall of the tubular element to bend
radially outward and in axially reverse direction so as to form an
expanded tubular section extending around a remaining tubular
section of the tubular element, wherein said bending occurs in a
bending zone of the tubular element, and increasing the length of
the expanded tubular section by inducing the bending zone to move
in axial direction relative to the remaining tubular section. One
of the tubular element and the wellbore wall is provided with at
least one seal member arranged to induce sealing of the expanded
tubular section relative to the wellbore wall.
Inventors: |
Hou; Fu Joseph; (Missouri
City, TX) ; Kriesels; Petrus Cornelis; (Rijswijk,
NL) ; Van Nieuwkoop; Pieter; (Rijswijk, NL) |
Family ID: |
39361297 |
Appl. No.: |
12/745768 |
Filed: |
December 2, 2008 |
PCT Filed: |
December 2, 2008 |
PCT NO: |
PCT/EP08/66620 |
371 Date: |
May 18, 2011 |
Current U.S.
Class: |
166/384 |
Current CPC
Class: |
E21B 43/103
20130101 |
Class at
Publication: |
166/384 |
International
Class: |
E21B 43/10 20060101
E21B043/10 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 4, 2007 |
EP |
07122208.7 |
Claims
1. A method of radially expanding a tubular element extending into
a wellbore formed in an earth formation, the method comprising
inducing the wall of the tubular element to bend radially outward
and in axially reverse direction so as to form an expanded tubular
section extending around a remaining tubular section of the tubular
element, wherein said bending occurs in a bending zone of the
tubular element; inducing the bending zone to move in axial
direction relative to the remaining tubular section so as to
increase the length of the expanded tubular section; wherein one of
the tubular element and the wellbore wall is provided with at least
one seal member arranged to induce sealing of the expanded tubular
section relative to the wellbore wall.
2. The method of claim 1, wherein each seal member comprises a
swellable elastomer susceptible of swelling upon contact with a
fluid selected from formation fluid and wellbore fluid.
3. The method of claim 1, wherein each seal member is provided at
the tubular element, the seal member being positioned at one of the
outer surface and the inner surface of the expanded tubular
section.
4. The method of claim 3, wherein the seal member is fixedly
connected to the expanded tubular section.
5. The method of claim 3, wherein the seal member is integrally
formed with the expanded tubular section.
6. The method of claim 1 wherein the wall of the tubular element
includes a material susceptible of plastic deformation in the
bending zone during the bending process so that the expanded
tubular section retains an expanded shape as a result of said
plastic deformation.
7. The method of claim 1 wherein the bending zone is induced to
move in axial direction relative to the remaining tubular section
by inducing the remaining tubular section to move in axial
direction relative to the expanded tubular section.
8. The method of claim 7, wherein the remaining tubular section is
subjected to an axially compressive force acting to induce said
movement of the remaining tubular section.
9. The method of claim 8, wherein said axially compressive force is
at least partly due to the weight of the remaining tubular
section.
10. The method of claim 8 wherein said axially compressive force is
at least partly due to an external force applied to the remaining
tubular section.
11. The method of claim 1 wherein the remaining tubular section is
axially shortened at a lower end thereof due to said movement of
the bending zone, and wherein the method further comprises axially
extending the remaining tubular section at an upper end thereof in
correspondence with said axial shortening at the lower end
thereof.
12. The method of claim 1 wherein a drill string extends through
the remaining tubular section for further drilling of the
wellbore.
13. The method of claim 12, wherein the remaining tubular section
and the drill string are simultaneously lowered through the
wellbore during drilling with the drill string.
14. (canceled)
Description
[0001] The present invention relates to a method of radially
expanding a tubular element in a wellbore.
[0002] The technology of radially expanding tubular elements in
wellbores is increasingly applied in the industry of oil and gas
production from subterranean formations. Wellbores are generally
provided with one or more casings or liners to provide stability to
the wellbore wall, and/or to provide zonal isolation between
different earth formation layers. The terms "casing" and "liner"
refer to tubular elements for supporting and stabilising the
wellbore wall, whereby it is generally understood that a casing
extends from surface into the wellbore and that a liner extends
from a downhole location further into the wellbore. However, in the
present context, the terms "casing" and "liner" are used
interchangeably and without such intended distinction.
[0003] In conventional wellbore construction, several casings are
set at different depth intervals, and in a nested arrangement,
whereby each subsequent casing is lowered through the previous
casing and therefore has a smaller diameter than the previous
casing. As a result, the cross-sectional wellbore size that is
available for oil and gas production, decreases with depth. To
alleviate this drawback, it has become general practice to radially
expand one or more tubular elements at the desired depth in the
wellbore, for example to form an expanded casing, expanded liner,
or a clad against an existing casing or liner. Also, it has been
proposed to radially expand each subsequent casing to substantially
the same diameter as the previous casing to form a monobore
wellbore. It is thus achieved that the available diameter of the
wellbore remains substantially constant along (a portion of) its
depth as opposed to the conventional nested arrangement.
[0004] EP 1438483 B1 discloses a method of radially expanding a
tubular element in a wellbore whereby the tubular element, in
unexpanded state, is initially attached to a drill string during
drilling of a new wellbore section. Thereafter the tubular element
is radially expanded and released from the drill string.
[0005] To expand such wellbore tubular element, generally a conical
expander is used with a largest outer diameter substantially equal
to the required tubular diameter after expansion. The expander is
pumped, pushed or pulled through the tubular element. Such method
can lead to high friction forces that need to be overcome, between
the expander and the inner surface of the tubular element. Also,
there is a risk that the expander becomes stuck in the tubular
element.
[0006] EP 0044706 A2 discloses a method of radially expanding a
flexible tube of woven material or cloth by eversion thereof in a
wellbore, to separate drilling fluid pumped into the wellbore from
slurry cuttings flowing towards the surface.
[0007] Although in some applications the known expansion techniques
have indicated promising results, there is a need for an improved
method of radially expanding a tubular element.
[0008] In accordance with the invention there is provided a method
of radially expanding a tubular element extending into a wellbore
formed in an earth formation, the method comprising
[0009] inducing the wall of the tubular element to bend radially
outward and in axially reverse direction so as to form an expanded
tubular section extending around a remaining tubular section of the
tubular element, wherein said bending occurs in a bending zone of
the tubular element;
[0010] increasing the length of the expanded tubular section by
inducing the bending zone to move in axial direction relative to
the remaining tubular section;
wherein one of the tubular element and the wellbore wall is
provided with at least one seal member arranged to induce sealing
of the expanded tubular section relative to the wellbore wall.
[0011] Thus, the tubular element is effectively turned inside out
during the bending process. The bending zone of a respective layer
defines the location where the bending process takes place. By
inducing the bending zone to move in axial direction along the
tubular element it is achieved that the tubular element is
progressively expanded without the need for an expander that is
pushed, pulled or pumped through the tubular element.
[0012] Furthermore, by virtue of the expanded tubular section being
sealed relative to the wellbore wall, undesired outflow of wellbore
fluid from the wellbore, or undesired inflow of formation fluid
into the wellbore past the expanded tubular section, is
prevented.
[0013] Suitably, each seal member is provided at the tubular
element, wherein the seal member is positioned at one of the outer
surface and the inner surface of the expanded tubular section.
[0014] The seal member can be fixedly connected to the expanded
tubular section by suitable connecting means, or it can be
integrally formed with the expanded tubular section.
[0015] It is preferred that the wall of the tubular element
includes a material that is plastically deformed in the bending
zone, so that the expanded tubular section retains an expanded
shape as a result of said plastic deformation. In this manner it is
achieved that the expanded tubular section remains in expanded form
due to plastic deformation, i.e. permanent deformation, of the
wall. Thus, there is no need for an external force or pressure to
maintain the expanded form. If, for example, the expanded tubular
section has been expanded against the wellbore wall as a result of
said bending of the wall, no external radial force or pressure
needs to be exerted to the expanded tubular section to keep it
against the wellbore wall. Suitably the wall of the tubular element
is made of a metal such as steel or any other ductile metal capable
of being plastically deformed by eversion of the tubular element.
The expanded tubular section then has adequate collapse resistance,
for example in the order of 100-150 bars.
[0016] If the tubular element extends vertically in the wellbore,
the weight of the remaining tubular section can be utilised to
contribute to the force needed to induce downward movement of the
bending zone.
[0017] Suitably the bending zone is induced to move in axial
direction relative to the remaining tubular section by inducing the
remaining tubular section to move in axial direction relative to
the expanded tubular section. For example, the expanded tubular
section is held stationary while the remaining tubular section is
moved in axial direction through the expanded tubular section to
induce said bending of the wall.
[0018] In order to induce said movement of the remaining tubular
section, preferably the remaining tubular section is subjected to
an axially compressive force acting to induce said movement. The
axially compressive force preferably at least partly results from
the weight of the remaining tubular section. If necessary the
weight can be supplemented by an external, downward, force applied
to the remaining tubular section to induce said movement. As the
length, and hence the weight, of the remaining tubular section
increases, an upward force may need to be applied to the remaining
tubular section to prevent uncontrolled bending or buckling in the
bending zone.
[0019] If the bending zone is located at a lower end of the tubular
element, whereby the remaining tubular section is axially shortened
at a lower end thereof due to said movement of the bending zone, it
is preferred that the remaining tubular section is axially extended
at an upper end thereof in correspondence with said axial
shortening at the lower end thereof. The remaining tubular section
gradually shortens at its lower end due to continued reverse
bending of the wall. Therefore, by extending the remaining tubular
section at its upper end to compensate for shortening at its lower
end, the process of reverse bending the wall can be continued until
a desired length of the expanded tubular section is reached. The
remaining tubular section can be extended at its upper end, for
example, by connecting a tubular portion to the upper end in any
suitable manner such as by welding. Alternatively, the remaining
tubular section can be provided as a coiled tubing which is
unreeled from a reel and subsequently inserted into the
wellbore.
[0020] As a result of forming the expanded tubular section around
the remaining tubular section, an annular space is formed between
the unexpanded and expanded tubular sections. To increase the
collapse resistance of the expanded tubular section, a pressurized
fluid can be inserted into the annular space. The fluid pressure
can result solely from the weight of the fluid column in the
annular space, or in addition also from an external pressure
applied to the fluid column.
[0021] The expansion process is suitably initiated by bending the
wall of the tubular element at a lower end portion thereof by any
suitable means.
[0022] Advantageously the wellbore is being drilled with a drill
string extending through the unexpanded tubular section. In such
application the unexpanded tubular section and the drill string
preferably are lowered simultaneously through the wellbore during
drilling with the drill string.
[0023] Optionally the bending zone can be heated to promote bending
of the tubular wall.
[0024] To reduce any buckling tendency of the unexpanded tubular
section during the expansion process, the remaining tubular section
advantageously is kept centralised within the expanded section.
[0025] The invention will be described hereinafter in more detail
and by way of example, with reference to the accompanying drawings
in which:
[0026] FIG. 1 schematically shows a first embodiment of a wellbore
system during an initial stage of eversion of a liner;
[0027] FIG. 2 schematically shows the first embodiment during a
subsequent stage of eversion of the liner;
[0028] FIG. 3 schematically shows detail A of FIG. 2;
[0029] FIG. 4 schematically shows a second embodiment of a wellbore
system during an initial stage of eversion of a liner;
[0030] FIG. 5 schematically shows the second embodiment during a
subsequent stage of eversion of the liner;
[0031] FIG. 6 schematically shows a third embodiment of a wellbore
system during an initial stage of eversion of a liner;
[0032] FIG. 7 schematically shows the third embodiment during a
subsequent stage of eversion of the liner;
[0033] FIG. 8 schematically shows detail B of FIG. 7; and
[0034] FIG. 9 schematically shows the first embodiment, modified in
that a drill string extending through the wellbore liner.
[0035] In the Figures and the description like reference numerals
relate to like components.
[0036] Referring to FIGS. 1-3 there is shown, in longitudinal
section, the first embodiment comprising a wellbore 1 extending
into an earth formation 2, and a tubular element in the form of
liner 4 extending downwardly into the wellbore 1. The liner 4 has
been partially radially expanded by eversion of the wall of the
liner whereby a radially expanded tubular section 10 of the liner 4
has been formed, which has an outer diameter substantially equal to
the wellbore diameter. A remaining tubular section 8 of the liner 4
extends concentrically within the expanded tubular section 10.
[0037] The wall of the liner 4 is, due to eversion at its lower
end, bent radially outward and in axially reverse (i.e. upward)
direction so as to form a U-shaped lower section 16 of the liner
interconnecting the remaining liner section 8 and the expanded
liner section 10. The U-shaped lower section 16 of the liner 4
defines a bending zone 18 of the liner.
[0038] The expanded liner section 10 is axially fixed to the
wellbore wall 19 by virtue of frictional forces between the
expanded liner section 10 and the wellbore wall 19 resulting from
the expansion process. Alternatively, or additionally, the expanded
liner section 10 can be anchored to the wellbore wall by any
suitable anchoring means (not shown).
[0039] The liner 4 is provided with a plurality of annular seal
members 20 axially spaced along the liner 4. For ease of reference,
only one seal member 20 is shown. At the remaining liner section 8,
each seal member 20 is positioned at the inner surface of the
remaining liner section 8 (FIG. 1). After eversion of the liner,
the seal members 20 become positioned at the outer surface of the
expanded liner section 10 (FIG. 2). Further, each seal member 20 is
pressed against the wellbore wall 19 so as to form a seal between
the expanded liner section 10 and the wellbore wall 19.
[0040] The seal members 20 can be made of any suitable material
adapted to withstand compression against the wellbore wall 19, such
as, for example, steel, rubber, composite material etc.
[0041] Furthermore, the seal members 20 can be fixedly connected to
the liner 4 by suitable connecting means, or the seal members 20
can be integrally formed with the liner 4.
[0042] Referring further to FIGS. 4 and 5 there is shown, in
longitudinal section, the second embodiment, which is substantially
similar to the first embodiment. However, instead of annular seal
members being connected to the liner, in the second embodiment
annular seal members 25 are connected to the wellbore wall 19. The
seal members 25 can be fixedly connected to the wellbore wall 19 by
suitable means, or the seal members 25 can be integrally formed
with the wellbore wall. In the latter case, the seal members 25 can
be formed, for example, as annular ridges extending radially inward
from the wellbore wall 19.
[0043] Referring to FIGS. 6-8 there is shown, in longitudinal
section, the third embodiment, which is substantially similar to
the first embodiment. However in the third embodiment, annular seal
members 30 are provided at the outer surface of the remaining liner
section 8, rather than at the inner surface thereof. Like in the
first embodiment, the seal members 30 can be connected to the liner
4 by any suitable connecting means, or the seal members 30 can be
integrally formed with the liner 4. As shown in FIG. 7, the seal
members 30 become located at the inner surface of the expanded
liner section 10 after the eversion process whereby, at the
position of each seal member 30, the wall of the expanded liner
section 8 extends further radially outward than at adjacent
locations where no seal member is positioned (FIG. 8).
[0044] Referring further to FIG. 9, there is shown, in longitudinal
section, the first embodiment, modified in that a drill string 40
extends from surface through the unexpanded liner section 8 to the
bottom of the wellbore 1. The drill string 40 has a bottom hole
assembly including a downhole motor 42 and a drill bit 44 driven by
the downhole motor 42. The drill bit 44 comprises a pilot bit 46
with gauge diameter slightly smaller than the internal diameter of
the remaining liner section 8, and a reamer section 48 with gauge
diameter adapted to drill the wellbore 1 to its nominal diameter.
The reamer section 48 is radially retractable to an outer diameter
allowing it to pass through unexpanded liner section 8, so that the
drill string 40 can be retrieved through the unexpanded liner
section 8 to surface.
[0045] During normal operation of the first embodiment (FIGS. 1-3),
a lower end portion of the liner 4 is initially everted, that is,
the lower portion is bent radially outward and in axially reverse
direction. The U-shaped lower section 16 and the expanded liner
section 10 are thereby initiated. Subsequently, the short length of
expanded liner section 10 that has been formed is anchored to the
wellbore wall by any suitable anchoring means. Depending on the
geometry and/or material properties of the liner 4, the expanded
liner section 10 alternatively can become anchored to the wellbore
wall automatically due to friction between the expanded liner
section 10 and the wellbore wall 19.
[0046] A downward force F of sufficient magnitude is then applied
to the unexpanded liner section 8 in order to move the unexpanded
liner section 8 gradually downward. As a result, the unexpanded
liner section 8 is progressively everted thereby progressively
transforming the unexpanded liner section 8 into the expanded liner
section 10. During the eversion process, the bending zone 18 moves
in downward direction at approximately half the speed of movement
of the unexpanded liner section 8.
[0047] During the eversion process, the seal members 20 move from
the inside of the remaining liner section 8 to the outside of the
expanded liner section 10. Since the outer surface of the expanded
liner section 10 is of a diameter substantially equal to the
wellbore diameter, and because the seal members 20 extend radially
outward from said outer surface, the seal members become compressed
between the expanded liner section 10 and the wellbore wall 19. The
seal members are thereby subjected to a radially inward reaction
force from the wellbore wall 19, which induces a slight elastic
deformation of the wall of the expanded liner section 10. Due to
this elastic deformation, the seal members 20 remain pressed
against the wellbore wall 19 so that the expanded liner section 10
is permanently sealed against the wellbore wall 19.
[0048] In this manner it is achieved that fluid from the wellbore,
or fluid from the surrounding earth formation, cannot leak between
the expanded liner section 10 and the wellbore wall 19.
[0049] If desired, the diameter and/or wall thickness of the liner
4 can be selected such that portions of the expanded liner section
10 inbetween adjacent seal members 20 become pressed against the
wellbore wall 19 as a result of the expansion process so as to seal
against the wellbore wall and/or to stabilize the wellbore wall. In
such case, the seal members 20 provide additional sealing
capacity.
[0050] Since the length, and hence the weight, of the unexpanded
section 8 gradually increases, the magnitude of downward force F
can be decreased gradually in correspondence with the increased
weight of section 8.
[0051] Normal operation of the second embodiment is substantially
similar to normal operation of the first embodiment, however
differing in that the seal members 25 are connected to, or
integrally formed with, the wellbore wall 19 prior to eversion of
liner 4. As the bending zone 18 steadily moves downward during
eversion of the liner 4, the seal members 25 successively become
compressed between the expanded liner section 10 and the wellbore
wall 19 (FIG. 5).
[0052] Normal operation of the third embodiment (FIGS. 6-8) is
substantially similar to normal of the first embodiment. As
mentioned hereinbefore, the seal members 30 become located at the
inner surface of the expanded liner section 10 after the eversion
process. The bending resistance of the wall of the liner 4 is
higher at locations where the seal members 30 are connected to the
liner, than at adjacent locations where no seal members are
located. Therefore, at the location of each seal member 30, the
wall of the liner 4 bends at a larger bending radius during the
eversion process than at adjacent locations where no seal member is
positioned.
[0053] In view thereof, at the location of each seal member 30, a
portion 32 of the wall of the expanded liner section 8 extends
further radially outward than at the adjacent locations (FIG.
8).
[0054] Each wall portion 32 thereby become pressed against the
wellbore wall 19 and is subjected to a radially inward reaction
force from the wellbore wall 19, which induces a slight elastic
deformation of the wall portion 32. This elastic deformation causes
the wall portions 32 to remain pressed against the wellbore wall 19
so that the expanded liner section 10 is permanently sealed against
the wellbore wall 19.
[0055] In this manner it is achieved that fluid from the wellbore,
or fluid from the surrounding earth formation, cannot leak between
the expanded liner section 10 and the wellbore wall 19.
[0056] If desired, the diameter and/or wall thickness of the liner
4 can be selected such that portions of the expanded liner section
10 inbetween the wall portions 32 also become pressed against the
wellbore wall 19 as a result of the expansion process. In such
case, the wall portions 32 provide additional sealing capacity.
[0057] Normal operation of the modified first embodiment shown in
FIG. 9 is substantially similar to normal operation of the first
embodiment regarding eversion of the liner 4. In addition, the
following features apply to normal operation of the modified first
embodiment. The downhole motor 42 is operated to rotate the drill
bit 44 so as to deepen the wellbore 1 by further drilling. Thereby,
the drill string 40 gradually moves downward into the wellbore 1.
The remaining liner section 8 is simultaneously moved downward in a
controlled manner, and at substantially the same speed as the drill
string 40, whereby it is ensured that the bending zone 18 remains
at a short distance above the drill bit 44. Such controlled
lowering of the remaining liner section 8 can be achieved by
controlling the downward force F referred to hereinbefore.
[0058] Initially the downward force F needs to be applied to the
unexpanded liner section 8 to induce lowering thereof
simultaneously with lowering of the drill string 40. As the length,
and hence the weight, of the unexpanded liner section 8 increases,
the magnitude of downward force F can be gradually decreased, and
eventually may be replaced by an upward force to prevent buckling
of the unexpanded liner section 8. Such upward force can be applied
to the remaining liner section 8 at surface, or it can be applied
to the drill string 40 and transmitted to the remaining liner
section 8 by suitable force transmission means (not shown). The
weight of the unexpanded liner section 8, in combination with the
force F (if any), also can be used to provide a thrust force to the
drill bit 44 during drilling of the wellbore 1.
[0059] Simultaneous lowering of the remaining liner section 8 and
the drill string 40 also can be achieved by axially restraining the
remaining liner section 8 to the drill string 40. For example, the
drill string 40 can be provided with a bearing device (not shown)
that supports the U-shaped lower section 16 of the liner 4.
[0060] As drilling proceeds, pipe sections are added at the top of
unexpanded liner section 8 in correspondence with its lowering into
the wellbore, as is normal practice for installing casings or
liners into wellbores.
[0061] When it is required to retrieve the drill string 40 to
surface, for example when the drill bit 44 is to be replaced or
when drilling of the wellbore 1 is complete, the reamer section 42
brought to its radially retracted mode. Subsequently the drill
string 24 is retrieved through the unexpanded liner section 8 to
surface.
[0062] In practicing the method of the invention, any combination
of the first, second and third embodiments may be applied. Thus,
seal members may be provided at the inner surface of the remaining
liner section, at the outer surface of the remaining liner section,
and at the wellbore wall in a single application.
[0063] Furthermore, the annular seal members preferably are made
of, or include, a swellable elastomer susceptible of swelling upon
contact with wellbore fluid and/or formation fluid. It is thereby
achieved that sealing of the seal members against the wellbore
wall, after swelling of the swellable elastomer, is enhanced. To
prevent premature swelling of the swellable elastomer during
installation into the wellbore, suitably each annular seal member
is provided with a protective coating that ruptures upon radial
expansion of the seal member as it passes through the bending zone,
or upon compression of the seal member between the expanded liner
section and the wellbore wall. After rupturing of the protective
coating, the swellable elastomer becomes exposed to the wellbore
fluid or formation fluid and thereby starts swelling. If there is
little or no space for the seal member to swell, the seal member
becomes more firmly compressed between the wellbore wall and the
expanded liner section thereby enhancing its sealing
functionality.
[0064] With the method described above, it is achieved that the
wellbore is progressively lined with the everted liner directly
above the drill bit, during the drilling process. As a result,
there is only a relatively short open-hole section of the wellbore
during the drilling process at all times. The advantages of such
short open-hole section will be most pronounced during drilling
into a hydrocarbon fluid containing layer of the earth formation.
In view thereof, for many applications it will be sufficient if the
process of liner eversion during drilling is applied only during
drilling into the hydrocarbon fluid reservoir, while other sections
of the wellbore are lined or cased in conventional manner.
Alternatively, the process of liner eversion during drilling may be
commenced at surface or at a selected downhole location, depending
on circumstances.
[0065] In view of the short open-hole section during drilling,
there is a significantly reduced risk that the wellbore fluid
pressure gradient exceeds the fracture gradient of the rock
formation, or that the wellbore fluid pressure gradient drops below
the pore pressure gradient of the rock formation. Therefore,
considerably longer intervals can be drilled at a single nominal
diameter than in a conventional drilling practice whereby casings
of stepwise decreasing diameter must be set at selected
intervals.
[0066] Also, if the wellbore is drilled through a shale layer, such
short open-hole section eliminates possible problems due to heaving
of the shale.
[0067] After the wellbore 1 has been drilled to the desired depth
and the drill string 40 has been removed from the wellbore 1, the
length of unexpanded liner section 8 that is still present in the
wellbore 1, can be left in the wellbore or it can be cut-off from
the expanded liner section 10 and retrieved to surface.
[0068] In case the length of unexpanded liner section 8 is left in
the wellbore 1, there are several options for completing the
wellbore. These are, for example, as follows.
A) A fluid, for example brine, is pumped into the annular space
between the unexpanded and expanded liner sections 8, 10 so as to
pressurise the annular space and increase the collapse resistance
of the expanded liner section 10. Optionally one or more holes are
provided in the U-shaped lower section 16 to allow the pumped fluid
to be circulated. B) A heavy fluid is pumped into the annular space
so as to support the expanded liner section 10 and increase its
collapse resistance. C) cement is pumped into the annular space in
order to create, after hardening of the cement, a solid body
between the unexpanded liner section 8 and the expanded liner
section 10, whereby the cement may expand upon hardening. D) the
unexpanded liner section 8 is radially expanded (i.e. clad) against
the expanded liner section 10, for example by pumping, pushing or
pulling an expander through the unexpanded liner section 8.
[0069] In the above examples, expansion of the liner is started at
surface or at a downhole location. In case of an offshore wellbore
whereby an offshore platform is positioned above the wellbore, at
the water surface, it can be advantageous to start the expansion
process at the offshore platform. In such process, the bending zone
moves from the offshore platform to the seabed and from there
further into the wellbore. Thus, the resulting expanded tubular
element not only forms a liner in the wellbore, but also a riser
extending from the offshore platform to the seabed. The need for a
separate riser from is thereby obviated.
[0070] Furthermore, conduits such as electric wires or optical
fibres for communication with downhole equipment can be extended in
the annular space between the expanded and unexpanded sections.
Such conduits can be attached to the outer surface of the tubular
element before expansion thereof. Also, the expanded and unexpanded
liner sections can be used as electricity conductors to transfer
data and/or power downhole.
[0071] Since any length of unexpanded liner section that is still
present in the wellbore after the eversion process is finalised, is
subjected to less stringent loading conditions than the expanded
liner section, such length of unexpanded liner section may have a
smaller wall thickness, or may be of lower quality or steel grade,
than the expanded liner section. For example, it may be made of
pipe having a relatively low yield strength or relatively low
collapse rating.
[0072] Instead of leaving a length of unexpanded liner section in
the wellbore after the expansion process, the entire liner can be
expanded with the method of the invention so that no unexpanded
liner section remains in the wellbore. In such case, an elongate
member, for example a pipe string, can be used to exert the
necessary downward force F to the unexpanded liner section during
the last phase of the expansion process.
[0073] In order to reduce friction forces between the unexpanded
and expanded tubular sections during the expansion process
described in any of the aforementioned examples, suitably a
friction reducing layer, such as a Teflon layer, is applied between
the unexpanded and expanded tubular sections. For example, a
friction reducing coating can be applied to the outer surface of
the tubular element before expansion. Such layer of friction
reducing material furthermore reduces the annular clearance between
the unexpanded and expanded sections, thus resulting in a reduced
buckling tendency of the unexpanded section. Instead of, or in
addition to, such friction reducing layer, centralizing pads and/or
rollers can be applied between the unexpanded and expanded sections
to reduce the friction forces and the annular clearance
there-between.
[0074] Instead of expanding the expanded liner section against the
wellbore wall (as described above), the expanded liner section can
be expanded against the inner surface of another tubular element
already present in the wellbore.
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