Note: Descriptions are shown in the official language in which they were submitted.
CA 02531932 2000-09-14
EXPANDABLE TUBING
This application is a divisional application of
Canadian Patent Application Serial No. 2,383,179 filed on
September 14, 2000.
This invention relates to a downhole apparatus, and in
particular but not exclusively to forms of expandable tubing
and to forms of expandable filters and filter supports. The
expression "the invention" and the like encompasses the
subject matter of both the parent and the divisional
applications.
W093/25800 (Shell Internationale Research Maatschappij
B.V.) describes a method of completing an uncased section of
borehole. A slotted liner provided with overlapping
longitudinal slots is fixed in the borehole and a tapering
expansion mandrel is pushed or pulled through the liner.
The liner is expanded by the mandrel to support the adjacent
borehole wall.
W097/17524 (Shell Internationale Research Maatschappij
B.V.) describes a deformable well screen and method for its
installation utilising two sections of concentric slotted
tubing, such as described in W093/25800, with a series of
circumferentially scaled filter segments therebetween. The
screen is expanded by pushing or pulling an expansion
mandrel through the screen.
The expansion mechanism of these arrangements is such
that there is an axial retraction of the tubing on radial
expansion. This not only creates difficulties in accurately
locating and securing the ends of the tubing in a bore
relative to adjacent tubing sections, but also may
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result in undesirable relative axial movement between the
tubing and other elements mounted thereon, such as filter
segments. Further, in such a filter arrangement, the
radial expansion forces which must be applied to the outer
section of expandable tubing are transferred via the filter
medium or media located between the tubing sections; this
limits the range of media which may be utilised in such
arrangements to filter materials and configurations which
will withstand significant compressive forces, in addition
to the significant shear forces which the filter material
will experience during expansion of the tubing sections.
It is among the objectives of embodiments of aspects
of the invention to provide alternative expandable tubing
forms, including expandable filters and filter supports,
which overcome such disadvantages.
According to the present invention there is provided
expandable tubing having a tubing wall comprising a
plurality of deformable tubular structures, at least some
of the structures having permeable walls and containing a
filter medium such that fluid may flow through the
structures and thus through the tubing wall.
This aspect of the invention is useful as a downhole
filter or sand screen, the deformable tubular structures
forming the wall of the tubing facilitating expansion of
the tubing, and the tubular structures potentially serving
as filter elements and also accommodating a selected filter
CA 02531932 2000-09-14
3
medium or media. Also, the use of the tubular structures to
accommodate or facilitate expansion assists in avoiding the
longitudinal contraction which tends to occur on radial
expansion of tubing defining overlapping longitudinally
extending slots.
The present invention also provides an expandable
tubing having a tubing wall comprising a plurality of
longitudinally extending deformable tubular structures, the
tubular structures being arranged in side-by-side
configuration to define said tubing wall and at least some
of the structures having porous walls of sintered ductile
material such that fluid may flow through the structures and
through the tubing wall.
The present invention also provides an expandable
tubing having a tubing wall comprising a plurality of
deformable tubular structures, at least some of the
structures having walls of porous material initially filled
by another removable material to create an initially
impermeable structure, such that upon removal of the
removable material fluid may flow through the structures and
thus through the tubing wall.
The present invention also provides an expandable
downhole tubing having a tubing wall comprising a plurality
of longitudinally extending deformable tubular structures,
the tubular structures being arranged in side-by-side
configuration to define the tubing wall and the deformable
tubular structures being retained between two expandable
sleeves.
The present invention also provides an expandable
downhole tubing having a tubing wall comprising a plurality
of longitudinally extending deformable tubular structures,
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3a
the tubular structures being arranged in side-by-side
configuration to define the tubing wall and the deformable
tubular structures being defined by a plurality of
corrugated members.
The present invention also provides an expandable
downhole tubing having a tubing wall comprising a plurality
of longitudinally extending deformable tubular structures,
the tubular structures being arranged in side-by-side
configuration to define the tubing wall and the deformable
tubular structures having discontinuities therein.
The tubular structures may extend longitudinally,
helically, or be positioned in any appropriate orientation.
A substantially axial orientation may offer more
straightforward assembly and resistance to bending, however
for other applications a helical arrangement may offer
greater flexibility and resistance to radial compressive
forces.
The tubular structures may be of any material,
structure or form which provides the desired degree of
deformability, permeability and the desired degree of
structural strength. In one embodiment, the tubular
structures are of sintered ductile metal, while in other
embodiments drilled or slotted tubes may be utilised. If
sintered metal, or some other porous material of similar
structure, is utilised to form the tubular structures, the
pores of the material may be initially filled or occupied by
another material to create an impermeable structure. This
filling material may be subsequently removed, for example by
application of an appropriate solvent, which may be produced
fluid, or exposure to elevated temperature as experienced in
deeper bores.
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4
The tubular structures may be connected to one another
by any appropriate method, for example metal structures may
be welded or brazed to one another, or the structures may
be retained between two expandable sleeves or tubes.
In other embodiments, the tubular structures may be
defined by appropriately shaped sheets or elements, or
unitary structures, for example two corrugated sheets or
tubes which have been welded or otherwise secured together,
or by extruding or otherwise forming the tubing wall in a
form which incorporates tubular structures. These
embodiments may form other aspects of the invention, in
which the tubular structures are impermeable, that is fluid
is prevented from flowing through the tubing wall, in one
or both of the unexpanded and expanded configurations.
The tubular structures may feature substantially
continuous walls, or may have discontinuities therein, for
example the tubular structures may be substantially C-
shaped.
The tubular structures may accommodate a filter medium
of'media, such as woven wire, porous foam, wire mesh or
wire wool, or indeed any medium presently utilised as a
filter and which could be located within a tubular
structure and withstand the change in shape experienced by
the tubular structures during expansion. Alternatively or
in addition, the tubular structures may be lined with a
filter media in the form of a flexible or deformable porous
CA 02531932 2006-10-24
material.
The aperture or pore size defined by the tubular
structures or- the filter media therein may be selected as
5 appropriate, depending on the intended application of the
tubing: the tubing may provide a relatively coarse filter,
for preventing passage of relatively large solids, or may
be such that passage of liquid or very fine solids is
-prevented or restricted, and only passage of gas is
permitted, by use of a tubular structure-lining material
such an expanded PTFE, as produced under the Gore-Tex trade
mark by W.L_ Gore & Associates_
In another aspect, the invention provides an
expandable downhole tubing having a tubing wall
comprising a plurality of longitudinally extending
deformable tubular structures, said tubular structures
being arranged in side-by-side configuration to define
said tubing wall, wherein said deformable tubular
structures are defined by at least one corrugated member
and are retained between two expandable sleeves.
These and other aspects of the present invention will
now be described, by way of example, with reference to the
accompanying drawings, in which:
Figure 1 is a diagrammatic representation of an
expandable tubing in accordance with an aspect of the
present invention;
Figure 2 shows the tubing of.:Figure 1 following
expansion;
CA 02531932 2006-10-24
5a
Figure 3 is a diagrammatic representation of part of
a wall of an expandable tubing in accordance with a
further aspect of the present invention;
Figure 4 shows the tubing of Figure 3 following
expansion;
Figure 5 illustrates an expandable tubing in
accordance with a still further aspect of the present
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6
invention; and
Figures 6 to 9 are diagrammatic representations..of
walls of expandable tubings in accordance with further
aspects of the present invention.
Reference is first made to Figures 1 and 2 of the
drawings, which illustrate a form of expandable tubing 10,
in accordance with an aspect of the present invention, and
which may be utilised as or as part of a sand screen or
other downhole filter arrangement. Typically, the tubing
will be run into a bore in, the "unexpanded" form as
illustrated in Figure 1, anchored in the bore, and then
expanded to the larger diameter expanded form as
illustrated in Figure 2, with a degree of expansion in
excess of 3011 being achievable.
The tubing wall 12 comprises a plurality of axially
extending tubular structures in the form of small diameter
tubes 14 formed of sintered metal. The tubes 14 provide a
porous sand filtering media.
Expansion of the tubing 10 is primarily accommodated
by a flattening of the tubes 14, and the expanded tubing is
shown in Figure 2 of the drawings. This expansion may be
achieved by means of a conventional expanding cone or
mandrel, which is pushed or pulled through the tubing 10.
As the tubes 14 deform there will also be some deformation
and variation in the sizes of the pores, apertures and
passages in the walls of the tubes, however pore size
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7 -
variation may be predicted to some extent, and in any event
it is difficult to form a porous sintered metal product
with closely controlled pore size.
Reference is now made to Figures 3 and 4 of the
drawings, which illustrate part of an alternative
expandable tubing 20, in which the tubing wall 22 comprises
a plurality of solid tubes 24 having holes 26 drilled
therein. The tubes 24 accommodate filter media 28 which
may be in the form of deformable woven wire, porous foam,
wire mesh or wire wool. On expansion of the tubing, to the
form illustrated in Figure 4, the aperture or pore size of
the filter media 28 will not tend to change (although the
filter media may be subject to some compaction), providing
a greater degree of predictability than the tubing 10
described above.
Reference is now made to Figure 5 which illustrates a
similar form of expandable tubing 40 to that shown in
Figure 1, except that the pores 42 of the material forming
the tube walls are initially filled by another removable
material 44 thus (temporarily) creating an impermeable
structure. This filling material 44 may be subsequently
dissolved, or removed by exposure to elevated temperatures.
Figure 6 illustrates a further alternative embodiment
of the present invention in which the tubular structures 52
are retained between two expandable sleeves 54, 55
Figure 7 illustrates a wall section 60 of tubing 60 of
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a further embodiment of the present invention wherein the
tubular structures 62 are defined by inner and outer
corrugated sheets 64, 66. These sheets 64, 66 are welded
together at 68.
Reference is now made to Figure 8, which shows a wall
section of tubing 70 of another embodiment of the
invention, which tubing features an alternative form of
tubular structures 72 to define the bounding walls of the
expandable tubing 70. In this particular example, the
tubular structures 72 do not have continuous walls, being
substantially C-shaped.
Figure 9 illustrates a wall section of tubing 80 of a
further embodiment of the invention. In this embodiment,
the porous tubular structures 82 are lined with afilter
membrane 84. In this example the membrane 84 is a flexible
porous material, in particular expanded PTFE, as sold under
the GORE-TEX trade mark, and is impervious to selected
liquids, and only permits passage of gas therethrough.
It will be apparent to those of the skill in the art
that the above-described embodiments are merely exemplary
of the various aspects of the present invention, and that
various modifications and improvements may be made thereto
without departing from the scope of the present invention.
