Note: Descriptions are shown in the official language in which they were submitted.
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I RATABLE PACKER
BACKGROUND OF THE INVENTION
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A. Field of the Invention
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The present invention relates generally to
5 packers for use in oil and gas wells for providing
annular seals between the outside owe pipe and the
surrounding surface of the Barlow or casing, and
more particularly to inflatable packers having long
inflatable sleeves adapted to be inflated with a
cement slurry, having means for increasing the
friction between the pipe and the inflatable
sleeve.
B. Description of the Prior Art
Inflatable packers of the typo disclosed 3 for
example, in US. Patent No. 3,640,732, or US.
Patent No. 3,837,947, Dave been used for many
years. Such packer include a tubular mandrel that
is covered by an inflatable sleeve secured to the
mandrel by a pair of axially spaced apart collar.
The sleeve is normally reinforced by a reinforcing
sheath, which comprises a plurality ox overlapping
ribs connected between the collars. Valve eons
are provided for allowing inflating fluid to enter
between the exterior of the mandrel and the inlay-
table sleeve to inflate the sleeve into sealingc~ntact with the Wilbur or cuing. Such inflow-
table packers function to isolate toe annul above
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the packer from that below and, accordingly, need
to be only of a length long enough to Norm an
effective seal.
More recently, there have been developed inflow-
table packers for use in well completion, which readapted to be positioned adjacent the producing
zone and inflated with cement. After the cement
has set, the packer is perforated and the well is
produced through the packer. Examples of such
inflatable packers are disclosed, for example, in
US. Patent No. 3,918,522, US. Patent No. Rev
40,711, and US. Patent No. 3,907,034. Such
inflatable packers tend to be relatively long, i.e.
from 10 feet to 40 feet in length, in order to seal
against both the producing formation, which is per
forayed, and the formations above end below the
producing formation.
Since the completion type inflatable packers
are of such length, the centrfll portion of the
inflatable sleeve is supported and in effect,
reinforced by the bore~lole. Accordingly, a rein-
forcing sheath it unnecessary in the central part
of the inflatable sleeve. However reinforcing is
necessary adjacent the ends of the inflatable
I sleeve to prevPn~ the inflatable sleeve from
extruding past the securing collar or hlowin~ out.
Therefore, toe inflatable sleeves of the complexion
type packers ore normally reinforced only it the
ends doesn't the securing koalas.
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As inflatable packers are run into the bore-
hole, there is sometimes kinetic between the inflow-
table sleeve and the Barlow wall. Such contact
is particularly lawlessly in David holes. Contact
between the sleeve and the Barlow wall during
movement causes frictional forces to be applied to
the sleeve what tend to move the sleeve with
respect to the mandrel. In short length inflatable
packers with continuous reinforcing sheaths, the
reinforcing sheath provides a measure of stiffness
to the sheath which prevents axially movement due
to frictional Wilbur contact. However, in the
case of long paclcers with largely unreinforced
inflatable sleeves, when the coefficient of Eric-
lion between the Wilbur and the sleeve exceeds
the coefficient of friction between rubber and the
mandrel, the sleeve can move with respect to the
mandrel. Such movement can cause thickening of the
sleeve at the upper end of the inflatable packer
and can deform outwardly the upper reinforcing
material. In some instances 3 the movement of the
sleeve along the mandrel can cause the diameter of
the packer to become greater than that of the bore-
hole, in which case the packer becomes stuck.
A solution Jo the problem o-f movement of the
inflatable sleeve with respect to the mandrel is
provided in US, Patent No. 4~311,314, which
discloses an inflatable packer having nun inflatable
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sleeve mounted on a tubular mandrel that is covered
with a gritty sand paper-like material The grit
particles are bonded to the outer surface of the
mandrel by a suitable binder, such as an epoxy
resin, as for example the adhesive sold under the
trademark EON by Shell Chemical Corporation. The
coefficient of friction of the inflatable sleeve on
the grit covered surface is much higher than the
coefficient of friction between the inflatable
sleeve and a Barlow wall. Accordingly, the
improvement of US. Patent 4,311,314, very effect
lively solve the problem of the movement of the
inflatable sleeve with respect to the mandrel.
However, there has been developed recently, new
cement bond log equipment that is gaining suntan
trial industry acceptance. Unfortunately, epoxy
resin acoustically decouples steel from cement.
While the bond between the mandrel and the epoxy
and between the epoxy and the cement try be per-
Erectly good, the new cement bond logging equipm~ntindicates that proper bonding has not been
achieved.
It is therefore an object of the present liven-
lion to provide an inflatable packer having a high
coefficient of friction between the mandrel and the
inflatable sleeve thou including a grit like
coating.
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SUMMARY OF THE INVENTION
In a broad aspect, the invention resides in an
inflatable packer comprising a tubular mandrel having a rough-
eyed exterior surface intermediate the ends thereof, an inflate
able sleeve surrounding said tubular mandrel in frictional con-
tact with the roughened exterior surface, means for sealingly
securing the ends of the inflatable sleeve to the tubular
mandrel, and jeans for inflating the inflatable sleeve.
In a preferred embodiment the inflatable packer
includes a tubular mandrel that is covered by an elastic
sleeve. The ends of the elastic sleeves are connected to and
sealed with the mandrel by a pair of spaced apart collars. One
of the collars has means for allowing inflating fluid to enter
between the inflatable sleeve and the mandrel to inflate the
sleeve. The tubular mandrel is easing that has an outside die-
meter and wall thickness greater than the minimums jet by
ASP. T . for casing. The exterior surface of the tubular mandrel
it roughened to provide an increased coefficient of friction
with the inflatable sleeve. The surface depth of the roughen-
in is such that the outside diameter and wall thickness of the mandrel within the roughening remains greater than APE.
minimums. Preferably, the roughened exterior is provided by
gnarling.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is 2 quarter sectional view of a packer of
the preferred embodiment of the present invention.
Figure 2 is an enlarged sectional view showing the
interface between thy tubular mandrel and the inflatable sleeve
of the preserlt invention.
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Fig. 3 is a view taken along line 3-3 of Fig.
I showing a detail of a portion owe the surface of
the mandrel of the inflatable packer of the present
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
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Referring now to the drawing, and first to Fig.
1, the inflatable packer of the present invention
is designated generally by the numeral 11. Packer
: 11 includes a tubular mandrel 13~ which in the pro
furred embodiment is a length of casing or the like
having threaded portions 15 and 17 at its respect
live ends Threaded portions 15 and 17 are adapted
to receive and connect with, respectively, a valve
collar 19 and a blank collar 21, which in urn are
adapted to be connected between adjacent other
tubular member 23 and 25 respectively to form a
string of pipe.
Valve collar 19 is of the type disclosed
generally in ITS Patent No. 3,437,142, and inkwell
dyes a passageway 27, having an inlet 29 and an
outlet 31, for the flow of inflating fluid
there through. Passageway 27 includes valve means
33 for preventing the flow of inflating fluid
through passageway 27 until a certain preselected
pressure d:Lfferen~lal is achieved an for pro
venting flow of fluid from outlet 31 to inlet 29.
Inflatable packer if includes an inflatable
sleeve 35 of a rubber like el~stomer positioned
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about tubular mandrel 13 and connected between
collars 19 and 21 by a pair of spaced apart heads
37 and 39, respectively. Heads 37 and 39, respect
lively, have connected thereto longitudinally
extending reinforcing element 41 and 43. In the
preferred embodiment, reinforcing elements 41 and
43 comprise a plurality of longitudinally extending
overlapping fibs connected at one end to the heads
and extending into and embedded in the material of
inflatable sleeve 35. As inflatable sleeve 35 is
inflated, the ribs of reinforcing elements 41 and
43 separate and expand.
Referring now to Fig. 2, there is shown in
detail the interface between tubular mandrel lo and
inflatable sleeve 35. Fig. 2 depicts a portion of
such interface in the vicinity of lower reinforming
element 41. As shown in Fig. 2, the exterior sun-
face of tubular mandrel 13 axially above the end of
lower reinforcing element 41 is roughened, as India
cawed generally at 45. The roughened exterior our-
face 45 extends axially upwardly to the vicinity of
the lower end of upper reinforcing element 43. As
shown in Fig, 3, in toe preferred embodLmen~,
roughened surface I is formed by a plurality of
closely spaced apart orthogonal groQV~q which pry-
sent a knurled appearance. In thy preferred embo-
dominate thy grooves of roughened Sirius 45 are
formed ho brinelling the surface with plural
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of rollers. However, those skilled in the art will
recognize alternative method of forming the
Icn~lrling pattern, as for example, by scratching or
cutting the surface of tubular mandrel 13. Also
in the preferred embodiment, the grooves which
comprise knurl surface 45 are pluralities of ortho-
gonad helical grooves, but whose skilled in the at
will recognize other patterns as I examples
orthogonal longitudinal and circumferential
grooves. While roughened surface 45 is preferably
formed by gnarling, those skilled in the art Jill
recognize al~ernatlve methods of roughening the
pipe. For example, roughened surface 45 may be
foxed by abrasive sand or grit blasting" chemical
pitting, or the like.
It is important, during the formation or
roughened surface 45, that the grooves not be so
deep as to make the wall thickness of tubular
mandrel lo less than the minimum wall thickness end
outside diameter prescribed by the American
Petroleum Institute, APE. Spew SAY for casing of
the diameter of tubular mandrel 13. Thus, prior to
formation of roughened surface 45, pipe from which
tubular mandrel 13 it formed is selected to have on
ought diameter OLD. and wall thlckne~s treater
azalea the minimum jet by APE. The depth of
roughening by gnarling or the live I theft selected
such that after roughening, the outloud diameter
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and wall thickness of the pipe radially beneath the
roughening remains at least equal to the APE.
minimums. For example, the APE. specific~tlons
require that for casing greater than I inch out-
side diameter, the tolerances for outside diameter be -~0.75~ and for wall thickness be -12.5%~ Thus,
for 7 inch 26.0 pound per foot casing the outside
diameter Jay vary from 6.9475 inches to 7.0525
inches. The wall thickness specified for such
casing is 0.362 inches, but may be, within
tolerance, as low as 0.316 inches. The pipe LO
thus selected having an outside diameter and wall
thickness greater than the respective minimums and
the depth the roughening is selected such that the
undisturbed material underlying the roughening it
equal to or greater than the minimums. It has keen
discovered that the grooves of roughened surface 45
need not be very deep in order to provide a sub-
staunchly coefficient of friction with the rubber-
I like material of inflatable sleeve 45. Indeed grooves less than 0.05 inches in depth will
increase substantially the coefficient of friction.
Referring still to Figs. 2 and 3, tubular
mandrel 13 includes a smooth outer surf~cP 47
axially below the end of re~nEorcing element 41.
Tubular mandrel 13 includes similar sooth sun-
face axially above the end of upper re-lnforcin~
element 43. Smooth portion 47 allows lower herd Al
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with reinforcing element 41 embedded in the rubber-
like material to be slipped axially thereon and to
be interconnected with valve collar 19. Upper head
39 with reinforcing element 34 may likewise be
slipped over the axially pyre smooth portion of
tubular mandrel `13 and interconnected with collar
21. With heads 37 and 39 so positioned, the
remainder of inflatable sleeve 35 may be laid in
strops fashion upon tubular mandrel 13 and cured
in place. The material of sleeve 35 conforms to
and intermits with roughened surface 45 of tubular
mandrel 13.
From the foregoing it will be seen that this
invention is one well adapted to attain nil of the
ends and objects honeybee set forth, together
with other advantages which are obvious and which
are inherent to the apparatus.
It will be understood that certain features and
subcombinAt:ion~ are ox utility and Jay be employed
with reference to other features and ~ubcom-
binations. This is contemplated by and is within
the scope of` the claims.
As many possible embodiments may be made of the
invention without departitlg from the scope thereof,
I I Lo to be understood aye all matter herein jet
-forth of Shelley Lo the ~ccompanyit g drawings is to
be interpreted AS illustrative and not in a
l~lmitin~ sense.
