Note: Descriptions are shown in the official language in which they were submitted.
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'73818-5
gACKCROUND 'OF 'THE 'TNVENTxON
FTELD OF'THE TNVENTZON
The invention relates to an improved sealing assembly
for a subterranean well packing unit, and particularly to a
sealing assembly that minimizes extrusion of the organic sealing
material commonly employed in such packing unit.
SUMMARY'OF'THE'PRIOR:ART
As will be later described in connection with Figure 1,
prior art sealing assemblies have involved a sealing sleeve formed
of an organic sealing material which snugly surrounds the
tubular body portion of a.packer or bridge plug for a
subterranean well: The sealing slee~re is subjected to substantial
compressive forces by upper and lower cone elements having
oppositely disposed inclined surfaces. Intermediate the inclined
surfaces of the cone elements and the original end surface of the
seal~.ng sleeve, a cone ring and, a packer ring are mounted. Both
of these rings have to be C-rings ~to permit their expansion. The
cone ring has an inclined surface that is cooperable with the
inclined surface an 'the adjacent cone. An annular groove and
slot effects the connection of each cone ring to the packer ring.
Each packer ring has an inclined surface wh~,ch is engagable with
the end surface of the seal9.ng sleeve.
As the upper and lower cones are moved axially
relative to each other so as to bring them closer together, an
increasing compressive force is applied to the sealing sleeve.
At the same time,vthe cone rings and packer rings are expanded
radially outwardly by the inclined surfaces of the upper and
lower cones.
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73818-~5
When the packer or bridge plug.is fully set and the
sealing sleeve is compressed between the tubular body and the
bore of a well conduit, vthe substantial compression forces on
the organic sealing element causes a gradual extrusion of the
material of such element between the inner face of the upper
and loc~:er cones and the outer surface of the tubular body. An
additional major extrusion path is provided between the inclined
surface of the cone ring and the cooperating inclined surface
of the respective upper or lower cone because of the C-ring
construction of the cone ring. Such extrusion path effects a
gradual reduction in the compressive forces trapped in the
organic sealing element, hence reducing the sealing efficiency of
such element.
Numerous solutions have been proposed for this
extrusion problem in the past, but none have been fully effective.
There is a definite need therefore, for a sealing assembly which
will effectively prevent extrusion of an organic sealing element
along the extrusion paths previously mentioned.
SUMMARY OF TIE 'INVENTION
The invention employs a conventional tubular body on
which are mounted upper and lower cone elements for relative
axial movement. Between the cone elements a sleeve of any
conventional organic, elastomeric sealing material is snugly
mounted on the exterior of the tubular body. Each of the upper
and lower cone elements have oppasitely disposed inclined surfaces
which, in the upset position of the upper and lower cone elements
are not normally in engagement with the sealing sleeve.
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'3818-5
The spaces intermediate the oppositely inclined
surfaces on the upper and lower cones and the axial ends of the
sealing sleeve axe occupied by a pair of,cone rings and packer
rings. The cone rings and packer rings are of C-ring construction.
Each cone ring is of.generally triangular cross-section and has
an inclined.surfa.ce that mates with the inclined surface on the
adjacent one of the upper and lower cones. Each packer ring has
an inclined surface engaged with the adjacent end face of the
organic sealing element. in the onset position of the sealing
assembly. An annular slot is provided in one of the packer rings
and cone rings and an annular groove caoperable with such slot is
provided in the other of these rings,. thus securing each cone
ring and 'the adjacent paoker ring for co-movement.
In the conventional construction, the cone ring
normally has a slightly smaller internal diameter than the packer
ring. Since both the packer rings and cone rings are fabricated
as C-rings, there is an inherent path for extrusioxx of the
organic material of the sealing sleeve as compressivo :Forces are
applied to such sleeve.
Tn accordance with this invention, each packer ring
has a smaller internal diameter than the adjacent cone ring and
is fabricated from a relatively soft metallic material. Thus,
a vertex portion of the packer ring extends radially inwardly
beyond the cone ring and, as compressive force i.s applied to the
organic material of the sealing sleeve, such material exerts a
substantial force against such vertex portion and readily effects
the shearing off of such vertex portion along a plane that
corresponds exactly to the inclination of the inclined surface of
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73g~.~-~
the adjacent cone element: Thus, as the,cone rings and packer
rings ride radially outwardly respectively on the upper and lower
cones, the surface newly created by the shearing action effects a
seal with the adjacent upper or lower Cone ring and
substantially reduces this extrusion path.
To further impro~ze the awti-extrusion property of the
sealing assembly, the oppositely inclined surfaces of the upper
and lower cone rings are terminated in a generally radial. inner
surface, thus defining annular chambers of triangularly shaped
configuration respectively between the upper and lower cones and
the adjacent cone rings in the onset position of the sealing
element. An annular ring of; carbon :fiber filled organic sealing
material, such as polyetheretherketone, is inserted in the
aforementioned annular ohamber and has a triangular Cross-section
conforming to that of the chamber. The fiber filling of this
material substantially eliminates ~,ts extrusion. Thus, as the
compression of the sealing sleeve is effected by the relative
movement of the upper and lower COnes toward each other, this
triangular cross-seCt~.on sealing element effects a sealing
engagement bwtweenvthe radial inner sur:~ace provided on each.
of the uppor and lawer cones and the adjacent external surface of
the tubular body. '.t'hus, the second major path for extrusion loss
of material of the organic sealing element is effectively
eliminated.
Further objects and advantages of the invention will be
readily apparent to those skilled in the art from the following
detailed description, on which is shown a preferred embodiment of
the invention.
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'~38:L8-5
BRTEF 'DESCRTPTTON 'aF ~DRA.WT1~TGS
Figure 1 is a vertical quarter~sectional. view of an
existing sealing assembly for a subterranean well packing unit,
on which the major seal extrusion leakage paths are indicated.
Figure 2 is a vertical quarter-sectional view of an
extrusion of a sealing assembly for a subterranean well packing
unit embodying this invention, ~,~rith the sealing assembly shown
in its unset or uncompressed condition.
Figure 3 is a view similar to Figure 2 but showing the
sealing assembly in its set or compressed position in engagement
with the wall of a well conduit.
Figure 4 is an enlarged view of that portion of Figure
2 contained within the dotted line circle.
Figure 5 is an enlarged view of that portion of Figure
3 contained within the dotted line circle.
DESCRTPTTON OF PREFERRED EMBODTMENT
Referring to Figure 1, there is illustrated a
conventional sealing assembly for a packer or bridge plug
employed In a subterranean well. The sealing assembly is shown
in its expanded positipn and a tubular mass o:~ organ:Lc sealing
ma,t:erial is compxossed into sealing engagement between the
exterior of a body tube and the bore of a well conduit such as
the casing. The compression of the organic sealing material is
effected by relative movement of upper and lower cones toward
each other which effect the concurrent movements of a cone ring
and packer ring mounted between each axial end of the sealing
material and the respective upper or lower cone element. The cone
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'73818-5
rings and packer rings axe necessarily of-C-ring configuration
because the cone ring has an inclined surface engagable with a
similarly shaped surface formed on the adjacent upper or lower
cone element which expands the cone rings and packer rings
outwardly. The packer ring is moved outwardly by the C-ring
through the inner engagement through an annular tongue and groove
connection.
When the sealing material is in its compressed
condition, there are two major paths for extrusion of such
material. The first path, indicated by the arrow A, is between
the lower end of the packer ring and then through the C-ring
opening of the cone ring.
The second major extrusion path, indicated by the
arrow B, is between the internal surface of the upper and lower
cones and the adjacent external surface of the tubular body on
which such cones are mounted.
It is therefore readily apparent that in this prior
art construction, a substantial quantity of the organic sealing
material may be extruded through the leakago paths A and B and
thus the compressive Forces ex:Lsting ~.n the sealing mater~.a1 will
be gradually reduced, 'thus reducing the sealing effectiveness
of such material.
Turning now to Figures 2 - 5, a sealing assembly
embodying this invention is illustrated. In Figure 2, the
sealing assembly is shown in its unset or uncompressed position,
while in Figure 3, the sealing assembly is shown in its set or
compressed position.
73818-5
The sealing assembly embodying this invention is
mounted between the tubular body 10 of a packer, bridge plug or
similar well tool and the bore of a..well conduit C comprises an
annular mass of an organic, elastomeric material 20 which is
snugly engagable with, the exterior external surface 10a of the
tubular body 10. Such annular mass will hereinafter be referred
to as a sealing sleeve.
Adjacent each end of the sealing sleeve 20, an upper
cone 12 and a lower cone l4 are respectively provided. Such cone
elements have oppositely'inclined, facing surfaces 12a and 14a.
Intermediate each axial end of the sealing sleeve 20,
and the upper and lower cones I2 and l4, a pair of cooperating
rings 16 and l8 are provided. The rings 16 are commonly referred
to as cone rings and are of triangular shaped cross-section and
have inclined surfaces l6a which conform to and are engaged by
the inclined surfaces 12a and lea of vthe upper and lower cones 12
and 14 respectively. The ring elements 18 aye commonly referred
to as packer rings and again are of triangular crass-sectional
configuration and have opposed inclined surfaces 18a engagable
20. with the opposite axial ends of the sealing sleeve 20 as the
upper and lower cones are moved,relatively towards each other.
Both the rings 16 and l8 are of C-ring configuration to permit
their radial expansion as the upper and lower cones l2 and 14
move toward each other. The cane rings 16 and 18 are connected
for co-movement by an annular tongue or ridge 16b formed on the
cone rings 16 and an annular groove l8b formed on the packer
rings 18 and receiving the rib 16b therein in snug fitting.
relationship.
., ~9~~~~~~:"1
738185
In accordance with this invention, the lowermost
portion of the inclined surfaces 16a of the upper and lower cones
12 and 14 are both provided with generally radial surfaces 12b
and 14b respectively. These surfaces thus cooperate with the
adjacent inclined surface l6a of the cone ring 16 to define an
annular chamber of generally triangular cross-sectional
configuration and a continuous auxiliary ring 22 of a fiber
filled organic material is snugly inserted in such annular
chamber. The material employed for the ring 22 is preferably
polyetheretherketone which is filled with carbon fibers
constituting on the order of 30% of the total mass of the ring
22.
It will be noted from Figures 2 and 4 that the inner
end or the vertex portion 18c of each packer ring extends
radially inwardly beyond the ve~~tex 16c of the cone rings 16.
This dimensional relationship is provided for a specific purpose
that will became apparent when we turn to Figure 3 which shows
the seal assembly embodying this invent:Lon :l.n its sst or compressed
position .
As the compressive forces are exerted on the sealing
sleeve 20 by the relative axial movement of the cones 12 and 14
toward each other, such compressive forces are transmitted by
the sealing sleeve 20 to the vertex position l8c of the packer
ring 18. Since the packer ring l8 is formed of a relatively
soft material, such as ductile iron, this vertex portion 18c will
be sheared off in the manner indicated in Figure 5 and -the shear-
ing will take place along a plane 18d that is exactly parallel to
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73818-5
the inclination of the inclined suxface 12a or 14a of the
adjacent cone element 12 or 14 as the case may be. Thus, a
seal is provided between all portiorisof the packer ring 18 and
the inclined cone surfaces 12a or 14a except at the place where
the opening in the C°ring configuration of the packer ring 18
exists. As indicated in Figures 2 and 3, the C-ring openings
l8e in the packer rings 18 are 180° displaced from the C-ring
openings 16e in the cone ring 16.
Of equal importance is the fact that the compressed
organic material of the sealing sleeve 20 will exert a force
directly upon the auxiliary sealing ring 22 and prevent extrusion
between the inner cylindrical surfaces of the cones l2 and 14 and
the outer surface of the tubular body 10. The'sealing sleeve 20
is, of course, expanded into intimate engagement With the internal
wall of a well conduit, such as the casing C.
It w3.11 therefore be readily apparent to Chase skilled
in the art that a seal assembly embodying this invention
effectively substantially reduces the extrusion paths for
extrusion of an organic sealing element due to its compression by
the upper and lower cones during the setting operation.
Although the invention has been described in terms of
specified embodiments which are set forth in detail, it should
be understood that this is by illustration only and that the
invention is not necessarily limited thereto, since alternative
embodiments and operating techniques will become apparent to those
skilled in the art in view of the disc~.osure. Accordingly,
modifications are contemplated which can be made. without departing
from the spirit of the described invention.
