Note: Descriptions are shown in the official language in which they were submitted.
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WELL PACKER
This invention relates to well packers. In particular, the
invention relates to inflatable well packers, which in use are
inflated by fluid under pressure to isolate a zone in a well.
Inflatable well packers have been known for many years, the
packers being used to isolate a æone in a well, so as, for
example to enable a drill stem test to be performed, to
perform a selective chemical treatment, or to isolate a
redundant zone in a productive well. There are presently two
types of inflatable well packers, each being of a multi
layered construction including an elastomeric inner bladder,
but varying in the stress bearing system incorporated in the
packer. The first type of known well packer includes wire or
textile fibres, woven together with their ends secured to end
fittings by an epoxy potting process, the sheath of woven wire
or fibres being covered in an outer elastomeric boot which
will form the hydraulic seal to the casing, or open-hole
surface of a well which the well packer will, in use isolate.
The other type of inflatable well packer utilises long,
peripherally overlapping strips of spring steel which, when
the packer is inflated, slide radially against each okher like
venetian blinds, the strips surrounding khe elastomeric inner
bladder. The central portions o~ the strips are bonded to an
outer annular elastomeric boot which acts as a hydraulic ~eal
to the casing or open-hole ~ur~ace in u~e of the well packer.
An example of a well packer of this type is shown in U.S.
Patent Number 3160~11.
With either of these known well packers there are a number of
shortcomings. Firstly, the manufacture of either of these
well packers is labour intensive. In the case of the woven
sheath reinforced well packer, khe reinforcing wire or fabric
has to be hand-woven during assembly of the well packer. In
the case of the spring steel strip reinforced well packer, the
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large number o overlapping strips are di-~icult to a~semble
and engage in their end fittings.
Furthermore, in either o~ the known types o~ well packer~, khe
elastomeric inner bladder has to expand typically by twice the
amount that the outer elastomeric boot has to expand Thus,
if the packer has to be in-Elated by a ratio o~ 3:1 in order
for the outer boot to make the required seal, the inner
elastomeric bladder will have to expand by a ratio o~ 6:1.
This results in the inner elastomeric bladder in its inflated
state being very thin, thus making the inner elastomeric
bladder susceptible to any micro faults which it may have in
its structure. Furthermore, the high expansion ratio required
by the inner elastomeric bladder severely limits the choice of
materials which may be used. As a result of the limited
choice of materials, the inner elastomeric bladder tends to
have a very limited chemical resistance to any fluid other
than water, thus limiting the life of the packer when the
pasker is exposed to fluids such as acids, solvents, diesel
oil, and surfactants, these all being chemicals which are
commonly required for treatments of zones within wells.
With regard to the outer elastomeric boot included in either
type of known well packers, although this only has to
typically expand by a ratio of 3:1, and thus an increased
choice o materials enables it to have a better chemical
resistance to the fluids used in the wells than khat of the
inner elastomeric bladder, the outer elastomeric boot skill
has a relatively shork liEe span.
It is an obj~ct o~ the pre~ent ~nvention to provide a weLl
packer, together with a method of making the well packer,
wherein these problems are at least alleviated.
According to a first aspect of the present invention there is
provided an inflatable well packer comprising an annular
member including a quantity of a flexible material and a
stress bearing system, the annular member being such that
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pressure Erom the bore of the annular member causes inflation
of the well packer, wherein the inner and outer
circumferential surfaces of the annular member each carry a
protective layer of material effective to protec~ the ~lexible
material from the surrounding chemical environment.
The flexible material will generally be an elastomeric resin.
The protective layers of material suitably comprise metal
foils preferably in the form of a laminated layer of materials
highly resistant to corrosion.
Preferably the protective layers of deposited on the inner and
outer circumferential surfaces in a folded configuration.
Alternatively, the protective layers may be deposited on the
inner and outer circumferential surfaces in a twisted
configuration. Thus the protective layers may have different
expansion properties to those of the flexible material, the
necessary expansion of the layers when the packer is expanded
being at least partially produced by an unfolding or
untwisting of the protective layers.
In a preferred embodiment in accordance with the invention,
the annular member comprises at least one annular layer of
material comprising a ~eries o~ fibres encapsulated in the
fle~ible material, at leas~ a portion of the annular layer o~
material being corrugated along the direction o~ the
circum~erence of the layer, the layer being designed such that
prqssure from the bore of the annular member causes at least
partial unfolding of the corrugations, thereby causing-
inflation of the well packer.
According to a second aspect of the present invention, there
is provided a method of making an inflatable well packer,
including the steps of forming a first protective layer over
a mandrel; forming an annular member, including a quantity of
a fle~ible material and a stress bearing system, over the
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first protective layer; and forming a second protective layer
over the annular member, the first and second protective
layers being effective to protect the flexible makerial from
the surrounding chemical en~ironment.
Preferably at least part of the flexible material is injected
into a mould, defined by the second protective layer and part
of the annular member.
The first and second protective layers are suitably formed in
a folded configuration, either by exkending the material
forming the layers through a die, or alternatively
mechanically folding the layers. Such mechanical folding of
the layers may be achieved by forming each layer into the
shape of a tuber and mechanically folding regions of the tube.
A number of well packers in accordance with embodiments of the
invention, together with a method in accordance with an
embodiment of the invention of making a well packer, will now
be described, by way of example only, with reference to the
accompanying figures, in which:-
Figure 1 is a schematic cross-secti.on of a ~irst well packer
in accordance with an embodiment oE the invenkion, the well
packer being shown in an uninflated state:
Figure 2 is a ~chemakic cross-section of the well packer o~
Figure 1 in an inflated stake;
Figure 3 is a schematic end-sectional view of a disposable
inner mandrel used in a first stage of the method of
manufacture of the well packer of Figure 1
Figure 4 is a detail of Figure 3;
Figure 5 illustrates schematically part of a protective layer
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wound round the mandrel of Figure 3 laid on a flat surface,
Figure 6 shows the part layer o-f Figure S pulled out into a
single planar surface;
Figure 7 shows outer mould places being placed round the
disposable mandrel of figure 3;
Figure 8 is a schematic cross-section of a second well packer
in accordance with an embodiment of the invention, and
Figure 9 is a schematic cross-section of a third well packer
in accordance with an embodiment of the invention.
Referring firstly to Figure 1, the first embodiment of the
well packer to be described, comprises four concentric
corrugated layers 1,3,5,7 of reinforcing fibres encapsulated
in an elastomeric resin system 8 ~although conventional
unribbed layers could also be used). The two edges of the
layers 1,3,5,7 are secured by respective end fittings, not
shown. Conventional end ittlngs such as are well known in
the art can be used to secure the ends o the layers.
On the inner ~ur~ace o the innermost layer 1 and the outer
layer o~ the outermost ~ur~ace 7, there are ca:rried respec~lve
protective layers 9,11. The layers 9,11 ea~h comprlse a
material haviny a hic~h chemical resistance to oil wel1 ~luids
and khe fluids which are pumped lnko reservoir zones, examples
of a suitable material being most metals and selected
fluoroplastics such as Teflon or Ryton. Alternatively, the
layers may be formed from other materials having suitably high
chemical resistance properties, for example polyphenylene
sulphide which is sold under the trade names Ryton and Supec.
The well packer shown in Figure 1 is installed on a running
tool mandrel 13, a space 15 being defined between the outer
surface of the mandrel 13 and the protective layer 9.
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Referring now to Figure 2, in use of khe well packer the
packer is inserted in the core of a well, or in a casing such
as a cylindrical steel casing, only the lininy 17 oE the
casing being shown in the figure. To inflate khe well packer,
fluid is pumped into the space 15 between the mandrel 13 and
the inner protective layer 9, until the outer protective layer
11 conforms to the inner surface of the lining 17 of the steel
casing, the unwinding of the corrugations in the layers
1,3,5,7 enabling the expansion of the well packer. Thus the
corrugations enable the well packer to expand without relying
totally on the elastic expansion of the elastomeric resin. It
is particularly important to ensure that the outer and
innermost protective layers 9, 11 are securely sealed to the
end fittings to ensure that no corrosive elements penetrate
into the inner layers of the packer.
Referring now to Figure 3, in order to manufacture the well
packer shown in Figures 1 and 2, the inner protective layer 9
is laid round a disposable or reusable mandrel 19, as shown in
more detail in Figure 4. As can be seen in Figure 5, the
layer 9 has a folded configuration, the layer 11 being of a
similar configuration, this thus increasing the effective
length of the layers 9, 11 within the packer by the ratio X x
X x Y where X and Y are the distances indicated in Figur0s 6
and 5 respectively. This folded configuration can be produced
by extruding the raw material through a dye. ~lternat:Lvely,
the folded configuration o~ la~ers 9,11 can be produced
mechanically, by forming the layers 9,11 into tubes each
having a diameter equivalent ko the respective diameters that
the layers 9,11 will have when the packer is inflated, and
then performing a mechanical folding operation on the tubes.
The layers 9,11 are designed so that when the well packer has
inflated as shown in Figure 2, the folds are at least
partially removed. In a preferred embodiment the layers 9,11
have memory properties, such that when the well packer returns
to its unextended configuration, when the pressure inside the
packer is reduced, the layers resume their folds once more.
207~
This can be achieved by including short fibres tn the layer~
9,11 at the time o~ extrusion of the raw material used to
produce the layers 9,11 through a dye. ~uitable fibres for
this purpose are glass fibr~s, or short Kevlar fibres.
It will be appreciated that in a well packer in accordance
with the inventio~, the protective layers 9,11 act as the
internal pressure containment barrier, and also form the
external hydraulic seal to the surface of the bore or casing
into which the packer is inserted. Thus the temperature and
differential pressure limits for the well packer are
increased.
It will also be appreciated that, whilst a well packer in
accordance with the invention has particular application a
ribbed well packer described, a well packer in accordance with
the present invention has equal application to well packers
which do not incorporate the corrugated reinforcing layers
shown in my co-pending application, but incorporate
alternative forms of stress-bearing systems. Examples of well
packers in accordance with the invention incorporating such
alternative forms of stress-bearing systems are shown in
Figures 8 and 90 Referring firstly to figure 8, this figure
shows a cross section of a well packer in which the stréss
bearing system is of the type including long, peripherally
overlapping strips o spring steel 51. The inner 53 and outer
55 protective layers are formed of layers of material which
are folded back on themselves to ~orm ~olds around khe inner
and outer circumferential surfaces of the skress-bearing
system 51. E~pansion of the well packer is thus enabled by
the sliding over each other of the strips of spring steel 51
and the unfolding of the folds of the layer 53,55 as the
packer inflates.
Referring now to Figure 9, the third well packer in accordance
with an embodiment of the invention to be described, includes
a braided wire type stress bearing system 57. Inner 59 and
207~3~
outer 61 protective layers are formed in the inner an~ outer
circumferential surfaces of the braided wire 57, with radially
directed folds, which, during inflation of the well packer,
unfold to accommodate the e~pansion of the well packer.
In a further advantayeous embodiment of the invention a
suitable material which can transmit pressure such as a
suitable liquid or silicone is present between the inner
layers 1, 53, 59 and the other layers 3, 55, 61 of the packer
respectively. This material would help to prevent the build
up of hydrostatic pressure between the inner and outer layers
and the main body of the packer. This allows the folds or
corrugations in the inner and outer layers to unfold easily
and avoids pinching of the folds which would prevent the
layers from unfolding.
-
It will be appreciated that in each of the well packers inaccordance with embodiments of the invention, inflation of the
well packer is enabled by folding the layer of material
forming the inner and outer protective layers, the necessary
expansion of the layers on inflakion of the well packer can be
achieved by twisting a tubular layer over the inner and outer
circumferential surfaces o$ the stress bearing system, the
tubular layer having a largar circumference than the
circumferential surfaces. Thus, partlal untwi~ting o~ the
tubular layers as the packer in~lates, wl.ll aause at lea~t
part of the necessary expanslon o~ the layers.
It will also be appreciated that whilst it is advanta~eous to
enable expansion of the protective layers on inflation of the
packer, without relying totally on the elastic expansion
properties of the material forming the protective layers,
materials for the protective layers may be chosen which at
least partially accommodate the inflation of the packer by
virtue of their inherent elastic properties. For example,
some grades of Teflon have an elastic elongation before their
elastic limit ls reached. Thus by use of these materials, the
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need for folded or twisted protective layers may ~e avoided.
Where, however, polyphenylene sulphide, for e~ample Ryton or
Supec, is used for the protective layers, in view of the more
limited elastic properties of khese materials, it will be
ecessary to form the protective layers in a folded or twisted
configuration to achieve nearly all the necessary expansion.
