BACKGROUND OF THE INVENTION
[0001] This invention relates to inflatable well bore packers. More particularly, this invention
relates to new and improved inflatable packers employing elastomeric packer elements
that are reinforced by alternately biased plies of reinforcing wires and mounted on
a packer mandrel by special end fittings cooperatively securing the end portions of
the wires.
BACKGROUND ART
[0002] Inflatable packers are frequently used for selectively isolating formation intervals
during the performance of various testing or completion operations in cased well bores,
as well as in uncased boreholes. Since inflatable packers are actuated by fluid pressure
instead of by selective movements of their supporting pipe string, it is often preferred
to utilize such packers both as a single packer as well as for the spaced packers
on a so-called "straddle testing" tool. It is, however, recognized that inflatable
packer elements are apt to fail under extreme pressure differentials unless particular
care is taken in their design and construction. Many of the problems encountered with
prior art inflatable packers have been overcome with packers such as, for example,
the packers disclosed in U.S. Patent No. 4,406,461 and Canadian Patent No. 1,177,762.
Nevertheless, no completely satisfactory solution has heretofore been provided for
securing an inflatable reinforced packer element to a packer mandrel so that the tool
can be reliably operated under extreme pressure differentials.
OBJECTS OF THE INVENTION
[0003] Accordingly, it is an object of the present invention to provide new and improved
inflatable packers having internally-reinforced packer elements which have their end
portions firmly secured to the mandrels of the packers and reliably supported against
failure under extreme well bore pressures.
[0004] It is a further object of the present invention to provide a well bore packer having
an inflatable packer element with a plurality of reinforcing strands bonded between
inner and outer elastomeric plies, with the element being mounted on the packer mandrel
between new and improved coupling assemblies with gripping means securing the ends
of the reinforcing strands as well as deformable support means which cooperatively
expand or move outwardly as the packer element is initially inflated to support the
end portions of the inner ply against rupture.
SUMMARY OF THE INVENTION
[0005] These and other objects of the present invention are attained by providing a new
and improved well bore packer having an inflatable packer element that is comprised
of inner and outer elastomeric plies coaxially arranged on and bonded to an intermediate
sleeve formed of multiple plies of reinforcing strands. To secure the packer element
to the packer mandrel, inner and outer coupling members are coaxially disposed around
the mandrel at each end of the packer element so as to define convergent annular spaces
into which the free ends of the strands are disposed and cooperatively secured. The
outer coupling members have end portions extending over the packer element and bonded
to the ends of the outer elastomeric ply and which are internally rounded to accommodate
the outward movement of the reinforcing strands over the rounded end portions as the
element is inflated. The inner coupling members include yieldable or deformable skirt
portions disposed over the ends of the inner elastomeric ply and bonded thereto so
that the pressure forces inflating the packer element will correspondingly expand
these deformable skirt portions outwardly to support the end portions of the inner
ply.
[0006] In one embodiment of the invention, the reinforcing strands are secured by driving
coaxially-arranged inner and outer gripping members between the end portions of the
strands in the annular spaces. In an alternative embodiment, single gripping members
are driven between the stands in the annular spaces and secured by inner and outer
threaded locking rings. The threaded rings are cooperatively arranged so that tightening
of one ring will move the gripping member inwardly for securely clamping some of the
strands against one coupling member and tightening of the other locking ring will
pull the other coupling member outwardly against the gripping member for securely
clamping the remaining reinforcing strands against the other coupling member.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] The novel features of the present invention are set forth with particularity in the
appended claims. The invention, together with further objects and advantages thereof,
may best be understood by way of illustration of the following description of exemplary
apparatus employing the principles of the present invention as illustrated in the
accompanying drawing, in which:
FIGURE 1 shows a typical assembly of well tools in a well bore including a typical
straddle-packer tester employing a preferred embodiment of a new and improved inflatable
packer of the present invention;
FIGURE 2 is an enlarged cross-sectioned view of part of one of the packers shown in
FIGURE 1 showing a new and improved coupling assembly incorporating the principles
of the present invention to cooperatively secure an inflatable reinforced packer element
to the packer mandrel;
FIGURE 3 depicts a portion of the coupling assembly shown in FIGURE 2 as it will appear
after it has been expanded by inflation of the packer element; and
FIGURE 4 is an enlarged cross-sectioned view similar to FIGURE 2 but depicting an
alternative embodiment of a new and improved coupling assembly also arranged in accordance
with the principles of the present invention.
DESCRIPTION OF A PREFERRED EMBODIMENT
[0008] Turning now to FIGURE 1, new and improved inflatable well bore packers 10 and 11
incorporating the principles of the present invention are depicted in a typical string
of well tools dependently suspended from a pipe string 12 at a selected depth in a
well bore 13 where the packers have been expanded into sealing engagement with the
adjacent walls of the well bore. Although the new and improved packers 10 and 11 can
be employed either independently or together as well as with various types of well
bore tools, to illustrate one manner for utilizing these packers, the tools are depicted
as including a circulating valve 14 and a tester valve 15 which are respectively actuated
by selectively varying the pressure of the fluids in the annulus of the well bore
13 above the packers 10 and 11. A recorder housing 16 carrying one or more pressure
recorders 17 is dependently coupled to the tester 15. A central mandrel 18 intercoupling
the packers 10 and 11 communicates the tester valve 15 with the well bore interval
between the straddle packers 10 and 11. Although the inflatable packers 10 and 11
could just as well be expanded by pumping fluids from the surface through the pipe
string 12, the tools depicted in FIGURE 1 preferably include a rotary pump 19 which
is operable by rotating the pipe string for drawing well bore fluids through a screened
inlet pipe 20 and pumping them into the packers to inflate them. A typical drag spring
anchor 21 is coupled in the tool string to keep the tools from turning as the pipe
string 12 is rotated to drive the pump 19.
[0009] Since the upper and lower end portions of the new and improved inflatable packers
10 and 11 are identical, FIGURE 2 depicts only an enlarged, cross-sectioned partial
view of the upper end portion of the packer to illustrate the principles of the present
invention. To fabricate the illustrated packer element 22, inner and outer elastomeric
sleeves 23 and 24 are respectively disposed inside of and around an intermediate reinforcing
sleeve, as shown generally at 25, comprising a multiple plies of stranded steel wires;
and these three sleeves are bonded together in a typical fashion such as by vulcanization
to provide a unitary reinforced packer element capable of being inflated from its
normal relaxed diameter to a predetermined expanded diameter. In the preferred embodiment
of the inflatable packer element shown generally at 22, the inner sleeve or ply 23
is preferably compounded from an easily expandable elastomer and the outer sleeve
or ply 24 is preferably formed of a tough elastomer selected to form a protective
outer covering able to withstand abrasive well bore walls.
[0010] As one example of a preferred embodiment of the packer element 22, the inner elastomeric
ply 23 is enclosed by a sheath 26 formed of two or more layers or plies of stranded
steel wires or cords which are laid close to one another, with the wires in each ply
being successively directed in an alternate helical direction, so as to oppose outward
extrusion of the packer element 22 through the layers of the intermediate reinforcing
sleeve 25 during packer inflation. In the depicted exemplary packer element 22, the
protective sheath 26 is comprised of first and second plies of stranded steel wires
having a diameter of about 0.03 inch laid at an angle of about 12 degrees in relation
to the longitudinal axis of the packer mandrel 18, with one ply extending in a right-hand
helix and the other in a left-hand helix. In fabricating the protective sheath 26,
to ensure that the sheath will have uniform thickness the stranded wires in these
two inner plies may, for example, be dipped in a suitable bonding agent and calendared
with rubber before being wrapped around and secured over the inner elastomeric ply
23 of the new and improved inflatable packer element 22.
[0011] The design parameters for the reinforcing sleeve 25 are governed by the maximum expected
differential pressure to be imposed on the element 22 as well as the maximum expanded
diameter of the packer element. Since the inner sheath 26 has only a limited strength,
the principal strength of the packer element 22 is provided by the reinforcing sleeve
25 which is formed of two or more plies, as at 27-30, of closely-spaced stranded wires
or cables which, in the depicted exemplary packer element, are about 0.125 inch in
diameter and are cooperatively arranged between the outer elastomeric ply 24 and the
protective sheath 26. The several plies 27-30 are, preferably, respectively laid in
pairs in alternate right-hand and left-hand directions at bias angles which successively
increase from about 14 degrees for the innermost ply to about 16 degrees for the outermost
ply. This progressive angling provides for even distribution of the load across all
the plies at expansion. The protective sheath 26, the several reinforcing plies 27-30
and the elastomeric plies 23 and 24 are vulcanized together in a suitable fashion
to form a substantially unitary packer element 22 with the free ends of the stranded
wires of the several reinforcing plies 27-30 extending beyond the opposite ends of
the packer element.
[0012] To prepare the packer element 22 for mounting on the mandrel 18, an end-coupling
assembly, as seen generally at 31, is coaxially fitted over and secured to each end
of the inflatable packer element 22. As shown in FIGURE 2, each end-coupling assembly
31 includes an annular inner coupling member 32 which has been counterbored to define
a frustoconical socket 33 into which the complementary-shaped end of the inner elastomeric
sleeve 23 is snugly fitted and secured by a typical bonding technique. As will subsequently
be discussed in detail, a major feature of a present invention is that the outer end
of the socket 33 is cooperatively enlarged or counterbored to define a thin-walled
skirt portion 34 around the entrance to this socket. In keeping with the objects of
the invention, by designing the skirt portion 34 to expand as the pressure forces
imposed thereon by inflation of the packer element increase, the adjacent end portion
of the inner elastomeric ply 23 will be supported against extrusion around the inner
coupling member 32 when the packer 10 is set. As illustrated, the external surface
of the inner member 32 is also reduced slightly and the exposed ends of the reinforcing
sheath 26 are fitted over the entrance to the socket 33 and suitably bonded around
the deformable skirt portion 34.
[0013] Each end-coupling assembly 31 also includes an annular outer coupling member, as
at 35, which is coaxially disposed around the adjacent end of the expandable packer
element 22; with the axial bore of each outer coupling member being cooperatively
sized to snugly receive the exposed end portions of the main reinforcing plies 27-30.
The inwardly-projecting end of each outer coupling member 35 adjacent to the outer
elastomeric ply or sleeve 24 is shaped to provide a rounded, outwardly-diverging entrance
36 receiving the exposed end portions of the reinforcing plies 27-30 and adapted to
support the plies upon expansion of the packer element 22. It is also preferred to
externally reduce the inner end portion of the outer coupling members 35 for a short
distance to provide reduced portions 37 that may be snugly fitted into and bonded
to a tubular extension 38 of the outer elastomeric sleeve or ply 24.
[0014] Those skilled in the art will recognize that as the packer element 22 is inflated,
the resulting circumferential enlargement of the several reinforcing plies 27-30 will
subject the strands to substantial tensile forces which are directly proportional
to the differential between the inflation pressure inside of the packer element and
the well bore pressure outside of the element. These tension forces must be carried
by the end-coupling assemblies 31 if the packer 10 is to continue functioning. Accordingly,
as illustrated in FIGURE 2, the outer ends of the inner and outer coupling members
32 and 35 are respectively shaped to provide external and internal tapered surfaces
39 and 40 to cooperatively define an outwardly-diverging annular socket 41 for receiving
the exposed end portions of the several reinforcing plies 27-30. To secure the strands
of the reinforcing plies 27 -30 in the socket 41, the end-coupling assembly 31 of
the present invention further includes wedge means such as inner and outer wedge-shaped
gripping members 42 and 43 which are forcibly driven between the exposed ends of the
reinforcing plies 27-30.
[0015] In the preferred embodiment of the coupling assembly 31, the wedge means are formed
as unitary rings 42 and 43 which are made radially expansible by cutting each of the
rings at circumferentially-spaced intervals with alternately-directed longitudinal
slots of substantial length. As depicted, the inner gripping member 42 has a cylindrical
outer surface and is formed with a tapered bore which is enlarged toward its inner
end so as to be substantially parallel to the external facing surface 39 of the inner
coupling member 32. Similarly, the outer gripping member 43 is formed with a cylindrical
bore and has an outer tapered surface which is gradually reduced toward its inner
end so as to be substantially parallel to the internal facing surface 40 of the outer
coupling member 35. To enhance the holding force of the wedge-like gripping members
42 and 43, longitudinally- spaced rows of teeth, as at 44 and 45, are formed on the
internal and external surfaces of the gripping members. By forcibly driving the gripping
members 42 and 43 between the free ends of the strands of the reinforcing plies 27-30,
the wedging action provided by the coaction of the tapered facing surfaces 39 and
40 on the coupling members 32 and 35 with the teeth, as at 44 and 45, will effectively
clamp the ends of the reinforcing strands at each end of the inflatable packer element
22 against the facing surfaces of the end-coupling assemblies 31.
[0016] In one manner of securing the packer element 22 to the central mandrel 18 of the
inflatable packer 10, each end-coupling assembly 31 further includes an annular end
coupling member 46 which is threadedly secured at one end, as by threads 47, to the
outer coupling member 35 and which is secured at its other end by conventional means
of attachment to the mandrel 18. Each end-coupling assembly 31 also includes another
annular end-coupling member 48 threadedly coupled, as by threads 49, to the inner
coupling member 32 to firmly hold the end-coupling member against an outwardly-facing
shoulder, as at 50, in each of the outer end-coupling members 46. This prevents relative
movement of the coupling members 32 and 35, thereby keeping gripping members 42 and
43 firmly in position.
[0017] Turning now to FIGURE 3, a partial view is shown of the new and improved well packer
10 to illustrate the cooperative action of the elements of the end-coupling assemblies
31 when the packer element 22 is inflated. Focusing on a significant aspect of the
present invention, it is noted that the reduced or deformable portion 34 of the inner
coupling member 32 will be flared or expanded outwardly by the internal pressure forces
serving to inflate the packer element 22. Thus, the outward movement of the deformable
skirt portion 34 on each coupling assembly 31 will effectively cover the annular gaps
formed between the outer surface 39 of the inner coupling member 32 and the inner
sheath 26 and inner reinforcing ply 27 of the reinforcing sleeve 25 when the reinforcing
sleeve 25 is forced tightly against the inner facing surface 40 of the outer coupling
member 35. These gaps are small; but the support cooperatively provided by the deformable
skirt portions 34 at this critical location at each end of the packer element 22 will
effectively reduce, if not preclude altogether, the unwanted extrusion of the inner
elastomeric ply 23 through these gaps. Such unwanted extrusion into the sealed low
pressure cavity of socket 41 has been a major cause of failure in prior art inflatable
well bore packers.
[0018] It is also noted, with reference to FIGURE 3 that the axial or longitudinal spacing
between the inner end of the reduced portion 34 of the inner coupling member 32 and
the rounded end 36 of the outer coupling member 35 is such that, upon inflation of
the packer element 22, the reinforcing plies 27-30 are allowed to diverge outwardly
in a gradual curve rather than having to sharply bend across an abrupt, unrounded
corner. This feature prevents the cutting of the reinforcing strands 27-30 and the
tearing of the outer elastomeric sleeve 24 that occurs during inflation of prior art
packer elements, thereby avoiding fluid leak paths across the packer from the well
annulus to the isolated interval through the wire paths of sleeve 25.
DESCRIPTION OF AN ALTERNATIVE EMBODIMENT
[0019] As an alternative to the end-coupling assemblies 31 shown in FIGURE 2, a partial
cross-sectional view is shown in FIGURE 4 of a similar end-coupling assembly 100 incorporating
the principles of the present invention. As illustrated, the new and improved end-coupling
assembly 100 is cooperatively arranged for securing the ends of an inflatable packer
element 101 which has only two plies of reinforcing strands 102 and 103 instead of
the four plies of reinforcing strands employed in the packer element 22. By comparing
FIGURES 2 and 4 it can be seen that the end-coupling assembly 101 is almost identical
to the end-coupling assembly 31 in that the alternative assembly also employs inner
and outer end-coupling members 104 and 105 which are respectively bonded to inner
and outer elastomeric sleeves or plies 106 and 107; and that the adjacent surfaces
of these end-coupling members are appropriately fashioned for defining therebetween
an inwardly-tapered annular space 108 into which the free end portions of the reinforcing
strands of plies 102 and 103 are extended and firmly secured by wedge means such as
a single expansible wedge-like gripping member 109.
[0020] The particular distinction of the alternative coupling assembly 100 is that external
and internal threads 110 and 111 are respectively arranged on the inner and outer
coupling members 104 and 105 for receiving coaxially-fitting, inner and outer support
rings 112 and 113. In installing these support rings 112 and 113, one support ring
is initially installed and securely tightenend to urge the wedge-like gripping member
109 firmly against one set of the reinforcing strands 102 and 103; then the other
ring is securely tightened so as to firmly secure the gripping member 109 against
the other set of reinforcing strands. A lock ring 114 threaded to inner coupling member
104 can then be brought into locking engagement against outer ring 113, to prevent
relative movement between the inner and outer coupling members 104 and 105.
[0021] The independent tightening action of rings 112 and 113 against member 109 is advantageous
to accommodate structural mismatch. Though shown in FIGURE 4 in a packer embodiment
having only two plies 102 and 103, the same arrangement is beneficial to provide tight
anchoring with a greater number of reinforcing plies. In particular, it is noted that
a support ring arrangement similar to that shown in FIGURE 4 by rings 112 and 113
may be utilized for respectively securing the two gripping members 42 and 43 of the
embodiment shown in FIGURES 2 and 3.
[0022] It will be appreciated by those skilled in the art to which the invention relates
that broad application can also be given in many embodiments, other than those described
herein, to an inner coupling member, such as described member 32 or 104, having an
outwardly deformable thin-walled skirt end portion to prevent extrusion of an inner
elastomeric ply into a low pressure gap left during packer inflation as a reinforcing
sleeve is forced away from the outer surface of the inner coupling member. Such an
inner coupling member serves to reduce the risk of failure at a critical point in
packer construction and can thereby contribute significantly to the ability of an
inflatable packer to withstand large differential pressures. Reduction in risk of
failure can also be broadly achieved by the use of an outer coupling member, such
as described member 35 or 105, having a rounded outwardly-diverging tip 36 around
which a reinforcing sleeve can expand during packer inflation, eliminating sharp edges
or abrupt structure that might otherwise cut strands or tear elastomer to form annulus
fluid leakage paths across the packer. It is with such other embodiments in mind,
and in consideration of the various changes and modifications that may be made to
the two embodiments described without departing from the invention in its broader
aspects, that the claims are presented below.
1. A well packer adapted to be sealingly engaged with the walls of the well bore and
comprising:
a mandrel adapted for coupling to a pipe string;
an inflatable packer element coaxially mounted on said mandrel and including inner
and outer elastomeric plies and multiple layers of reinforcing strands bonded between
said inner and outer elastomeric plies; and
a coupling assembly at each end of said packer element for securing said packer element
to said mandrel and including an annular outer coupling member disposed over the ends
of said reinforcing strands, and an annular inner coupling member disposed within
the ends of said reinforcing strands and having an expansible skirt receiving the
adjacent end portion of said inner elastomeric ply and bonded thereto, said expansible
skirt being cooperatively arranged to be expanded by internal pressure forces inflating
said packer element for supporting said inner elastomeric ply against said internal
pressure forces tending to extrude adjacent end portions of said inner elastomeric
ply between said inner coupling member and the ends of said reinforcing strands.
2. The well packer of Claim 1 further including wedge means for cooperatively securing
said reinforcing strand ends between said coupling member at each end of said packer
element.
3. The well packer of Claim 1 further including at least one gripping member cooperatively
clamping said reinforcing strand ends against said coupling members at each end of
said packer element, and a retainer member cooperatively maintaining each of said
gripping members in position between said coupling members.
4. The well packer of Claim 1 further including inner and outer gripping members at
each end of said packer element cooperatively arranged between said coupling members
for clamping some of said reinforcing strand ends against said inner coupling member
and for clamping other of said reinforcing strand ends against said outer coupling
member.
5. The well packer of Claim 4 further including a retainer member cooperatively arranged
between one of said coupling members and each of said gripping members for securing
said gripping members in position.
6. An inflatable well packer adapted to be positioned in a well bore and expanded
into sealing engagement with the walls of a well bore and comprising:
a mandrel adapted for coupling to a pipe string;
an inflatable packer element coaxially mounted on said mandrel having inner and outer
elastomeric plies and an intermediate sleeve with multiple layers of reinforcing strands
bonded to one another and to said elastomeric plies defining a unitary packer element
with the ends of said reinforcing strands projecting from the upper and lower ends
of said packer element; and
upper and lower end-coupling assemblies cooperatively coupling said upper and lower
ends of said packer element to said mandrel, each of said end-coupling assemblies
including inner and outer coupling members with facing surfaces defining an annular
space receiving the adjacent end of said packer element, said outer coupling member
having an end portion with an inner surface converging outwardly to accommodate the
expansion of said packer element, said inner coupling member having a deformable end
portion projecting over the adjacent end of said inner elastomeric ply and adapted
to be deformed outwardly in response to inflation of said packer element for blocking
extrusion of said inner elastomeric ply between said inner coupling member and said
intermediate sleeve, and means securing said projecting ends of said reinforcing strands
within said annular space.
7. The well packer of Claim 6 wherein said facing surfaces of said coupling members
converge inwardly toward said end of said packer element; and said means for securing
said strand ends include inwardly-converging wedge means in said annular space cooperatively
clamping said strand ends between said wedge means and said facing surfaces of said
coupling members.
8. The well packer of Claim 7 further including retaining means threadedly mounted
on at least one of said coupling members and abutted with said wedge means for retaining
said one wedge means cooperatively clamped against said strand ends.
9. The well packer of Claim 8 wherein said wedge means include a single wedge member
cooperatively arranged in said annular space for clamping some of said strand ends
between said wedge member and said facing surface of said outer coupling member and
for clamping the remaining strand ends between said wedge member and said facing surface
of said inner coupling member.
10. The well packer of Claim 8 wherein said wedge means include inner and outer wedge
members cooperatively arranged in said annular space for clamping some of said strand
ends between said inner wedge member and said facing surface of said inner coupling
member and for clamping the remainder of said strand ends between said outer wedge
member and said facing surface of said outer coupling member.
11. The well packer of Claim 6 wherein said facing surfaces of said coupling members
converge inwardly toward said end of said packer element; and said means for securing
said strand ends include inner and outer inwardly-converging wedges coaxially fitted
together and cooperatively arranged in said annular space for clamping some of said
strand ends between said outer wedge and said facing surface of said outer coupling
member and for clamping the remainder of said strand ends between said inner wedge
and said facing surface of said inner coupling member.
12. The well packer of Claim 11 further including retaining means threadedly mounted
on at least one of said coupling members and abutted with at least one of said wedges
for retaining said one wedge cooperatively clamped against said strand ends.
13. An inflatable well packer adapted to be positioned in a well bore and expanded
into sealing engagement with the walls of a well bore and comprising:
a mandrel adapted for coupling to a pipe string;
an inflatable packer element coaxially mounted on said mandrel having an inner elastomeric
ply coaxially disposed within a shorter outer elastomeric ply and an intermediate
reinforcing sleeve formed of multiple biased layers of closely-spaced reinforcing
strands cooperatively bonded together and to said elastomeric plies for defining a
unitary element with the ends of said reinforcing strands projecting from the upper
and lower ends of said packer element; and
upper and lower end-coupling assemblies cooperatively coupling said upper and lower
ends of said packer element to said mandrel, each of said end-coupling assemblies
including inner and outer coupling members with facing surfaces defining an annular
space receiving an adjacent end of said packer element, said outer coupling member
having an inwardly-directed end portion extending over and bonded to said shorter
outer ply and an inward surface converging outwardly to accommodate the expansion
of said packer element, said inner coupling member having a reduced-thickness end
portion projecting over the adjacent end of said inner ply and adapted to be deformed
outwardly in response to pressure forces inflating said packer element for blocking
extrusion of said inner ply between said reduced-thickness end portion and said intermediate
sleeve, and means securing said projecting ends of said reinforcing strands within
said annular space.