Note: Descriptions are shown in the official language in which they were submitted.
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TITLE
[00011 Multistage Production System Incorporating Valve assembly With
Collapsible
or Expandable C-Ring
CROSS-REFERENCES TO RELATED APPLICATIONS
[0002] This original nonprovisional application claims the benefit of United
States
Provisional Application Ser. No. 61/453,288, filed March 16. 2011 entitled
"Multistage
Production System Incorporating Valve assembly With Collapsible or Expandable
Split Ring,"
and United States Provisional Application 61/475.333 filed April 14, 2011
entitled "Valve
assembly and System for Producing I-Iydrocarbons", each of which is
incorporated by reference
herein.
STATEMENT REGARDING FEDERALLY-SPONSORED RESEARCH OR
DEVELOPMENT
[0003] Not applicable.
BACKGROUND OF THE INVENTION
I. Field of the Invention.
[0004] The described embodiments and claimed invention relate to a tool for
sequentially engaging and releasing a restrictor element onto and from its
corresponding valve
seat, as well as systems and methods incorporating such a tool for producing
hydrocarbons from
multiple stages in a hydrocarbon production well. valve assembly
2. Background of the Art.
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[0005] In hydrocarbon wells, tools incorporating valve assemblies having a
restrictor
element such as a ball or dart and a scat element such as a ball seat or dart
seat have been used
for a number of different operations. Such valve assemblies prevent the flow
of fluid past the
assembly and, with the application of a desired pressure, can actuate one or
more tools associated
with the assembly.
[0006] One use for such remotely operated valve assemblies is in fracturing
(or
"fracing"), a technique used by well operators to create and/or extend one or
more cracks, called
"fractures" from the wellbore deeper into the surrounding formation in order
to improve the flow
of formation fluids into the wellbore. Fracing is typically accomplished by
injecting fluids from
the surface, through the wellbore, and into the formation at high pressure to
create the fractures
and to force them to both open wider and to extend further. In many case, the
injected fluids
contain a granular material, such as sand, which functions to hold the
fracture open after the fluid
pressure is reduced. .
[0007] Fracing multiple-stage production wells requires selective actuation of
valve
assemblys, such as fracing sleeves, to control fluid flow from the tubing
string to the formation.
For example. U.S. Published Application No. 2008/0302538. entitled Cemented
Open Hole
Selective Fracing System and which is incorporated by reference herein,
describes one system
for selectively actuating a fracing sleeve that incorporates a shifting tool.
The tool is run into the
tubing string and engages with a profile within the interior of the valve. An
inner sleeve may
then be moved to an open position to allow fracing or to a closed position to
prevent fluid flow to
or from the formation.
[0008] That same application describes a system using multiple valve
assemblies
which incorporate ball-and-seat seals, each having a differently-sized ball
seat and corresponding
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ball. Frac valves connected to ball and seat seals do not require the running
of a shifting tool
thousands of feet into the tubing string and are simpler to actuate than frac
valves requiring such
shifting tools. Such ball and seat seals are operated by placing an
appropriately sized ball into the
well bore and bringing the ball into contact with a corresponding ball seat.
The ball engages on a
sealing section of the ball seat to block the flow of fluids past the valve
assembly. Application of
pressure to the valve assembly causes the valve assembly to "shift", opening
the frac sleeve.
[0009] Some valve assemblies are selected for tool actuation by the size of
ball or
other restrictor element introduced into the well. If the well or tubing
string contains multiple
ball seats, the ball must be small enough that it will not seal against any of
the ball seats it
encounters prior to reaching the desired ball seat. For this reason, the
smallest ball to be used for
the planned operation is the first ball placed into the well or tubing and the
smallest ball seat is
positioned in the well or tubing the furthest from the wellhead. Thus, these
traditional valve
assemblies limit the number of valves that can be used in a given tubing
string because each ball
size is only able to actuate a single valve. Further. systems using these
valve assemblies require
each ball to be at least .125 inches larger than the immediately preceding
ball. Therefore, the
size of the liner restricts the number of valve assemblies with differently-
sized ball seats. In
other words. because a ball must be larger than its corresponding ball seat
and smaller than the
ball seats of all upwell valves, each ball can only seal against a single ball
seat and, if desired,
actuate one tool.
[0010] The valve assembly provides a method for sequentially sealing multiple
valve
seats with a single restrictor element and, where desired, actuating tools
associated with the valve
assembly. One embodiment allows multiple balls of the same size to actuate
tools in sequential
stages.
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BRIEF DESCRIPTION
[0011] The valve valve assemblyassembly described herein comprises a C-ring
(also
called a split ring) having a body with a seating surface, opposing terminal
ends. and an external
diameter extending radially from the body. The C-ring may be compressed such
that terminal
ends of the C-ring are in contact. In addition, the C-ring may be in an
uncompressed state
wherein the terminal ends are not in contact. The valve assembly further
comprises one or more
mounting elements to engage the outer diameter of the split ring. Engagement
of mounting
elements with the outer diameter causes the split ring to expand or contract.
[0012] Valve assemblies as described herein may further comprise a sleeve
contained
within a tubular housing, the sleeve having an inner surface, an outer
surface, and a plurality of
openings extending between said inner and outer surfaces. The openings are
aligned to engage
with the external diameter of the split ring. The tubular housing may have one
or more
mounting elements aligned within the openings in the sleeve, such that the
mounting elements
may engage the external diameter of the split ring when the sleeve is located
at a desired position
in the housing.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. I is a side partial sectional view of a preferred embodiment valve
asssmebly with an inner sleeve in an upwell first position.
[0014] FIG. 2 is a front elevation of the C-ring of the preferred embodiment
shown in
FIG. 1.
[0015] FIG. 3 is a sectional view through line 3-3 in FIG. 1.
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[0016] FIG. 4 is a side partial sectional view of a preferred embodiment valve
assembly shown in FIG. I with the inner sleeve in a downwell second position.
[0017] FIG. 5 is a sectional view through line 5-5 of FIG. 4.
[0018] FIG. 6 is a side partial sectional view of the preferred embodiment
with the
inner sleeve in a intermediate position between the first and second positions
described with
reference to FIG. I and FIG. 4, respectively.
[0019] FIG. 7 is a side sectional elevation of a system incorporating multiple
tools
having the features of the preferred embodiment.
[0020] FIGS. 8A & 8B illustrate an alternative embodiment showing a valve
assembly
with two seating elements
DETAILED DESCRIPTION
[00211 When used with reference to the figures. unless otherwise specified,
the terms
``upwell." "above," "top,- "upper," "downwell," "below," "bottom," "lower,"
and like terms are
used relative to the direction of normal production and/or flow of fluids and
or gas through the
tool and wellbore. Thus, normal production results in migration through the
wellbore and
production string from the downwell to upwell direction without regard to
whether the tubing
string is disposed in a vertical wellbore, a horizontal wellbore, or some
combination of both.
Similarly, during treatment of a well, which may include a fracturing, or
"fracing," process,
fluids move from the surface in the downwell direction to the portion of the
tubing string within
the formation to be treated.
[0022] FIG. I shows a preferred embodiment tool 20, which comprises a housing
22
connected to a bottom connection 24 at a threaded section 26. The housing 22
has a plurality of
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radially-oriented, circumferentially-aligned ports 28 providing communication
paths to and from
the exterior of the tool.
[0023] The housing 22 has a first cylindrical inner surface 30 having a first
inner
diameter, a second cylindrical inner surface 32 located downwell of the first
inner surface 30 and
having a second inner diameter that is greater than the first inner diameter,
and a third cylindrical
inner surface 34 having a third inner diameter that is greater than the second
cylindrical inner
surface 32. The first inner surface 30 is longitudinally adjacent to the
second inner surface 32,
forming a downwell-facing shoulder having an annular shoulder surface 38. The
second and
third inner surfaces 32, 34 are separated by a partially-conical surface 40.
[0024] The bottom connection 24 includes a first cylindrical inner surface 42
having a
first inner diameter and a second cylindrical inner surface 44 having a second
inner diameter.
The first and second inner cylindrical surfaces 42, 44 are separated by an
inner partially-conical
inner surface 46. An annular upper end surface 47 is adjacent to the first
inner surface 42.
[0025] The tool 20 comprises an annular sleeve 48 nested radially within the
housing
22 and positioned downwell of the shoulder 38. The sleeve 48 has an upper
outer surface 50
with a first outer diameter and a second outer surface 52 with a second outer
diameter less than
the first inner diameter. The first outer surface 50 and second outer surface
52 are separated by
an annular shoulder surface 54. The sleeve 48 further comprises a cylindrical
inner surface 56
that extends between annular upper and lower end surfaces 58, 60 of the sleeve
48.
[0026] In FIG. 1, the sleeve 48 is in a first position radially between the
plurality of
housing ports 28 and the center of the flowpath. In this position, the annular
sleeve 48 inhibits
fluid flow between the flowpath and the exterior of the tool. The sleeve 48
extends between the
shoulder 38 of the housing and the first inner surface 42 of the bottom
connection 24.
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[0027] The valve assembly may further comprise a guide element to position the
split
ring in the desired location. The guide element in the embodiment of Figure I
is a spring 64
residing in an annular spring return space 62. The annular spring return space
62 is partially
defined by the second outer surface 52 of the sleeve 48 and the third inner
surface 34 of the
housing 22. The spring return space is further defined by the upper end
surface 47 of the bottom
connection 24, the partially-conical surface 40 of the housing 22, and the
shoulder surface 54 and
first outer surface 50 of the sleeve 48.
[0028] In the embodiment illustrated by the figures, the C-ring 70 is
positioned within
the annular sleeve 48 between the upper end surface 58 and the shoulder
surface 54. The C-ring
70 fits into a groove formed in the inner surface 56 of the shifting sleeve
48. The groove is
sufficiently deep to allow the C-ring seating surface to expand to the desired
maximum diameter.
In some embodiments. the desired maximum diameter may be as large as or larger
than the inner
diameter of the shifting sleeve. Those of skill in the art will appreciate
that, in embodiments in
which the C-ring activates a sleeve or other valve assembly, the C-ring 70 may
be positioned at
any point along the sleeve or tool, or above or below the sleeve, provided
that the C-ring and the
sleeve or other tool are connected such that sufficient pressure applied to
the C-ring will slide the
sleeve in relation to the inner housing or otherwise activate the tool.
[0029] The C-ring 70 has an inner surface 74 an outer surface 76 defining the
outer
perimeter of the C-ring, and a seating surface 72 engagable with a restrictor
element having a
corresponding size. In the illustrated embodiment, the C-ring 70 is held in a
radially
compressed state by the first inner surface 50 of the housing 22.
[0030] FIG. 2 shows a front elevation of one embodiment of the C-ring 70 in a
normal
uncompressed state. In this embodiment, the outer surface 76 of the C-ring 70
is castellated with
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a plurality of radial protrusions 78, said radial protrusions defining the
outer diameter of the C-
ring. The circumference of the outer surface of the C-ring 70 may be larger
than the
circumference of inner surface 56 of the sleeve 48. The C-ring 70 has a
machined slot 80
forming terminal ends 82. The slot 80 shown in the illustrative figures is
within a protrusion 78,
but the slot 80 may be formed at any point along the C-ring and does not have
to be formed in a
protrusion 78.
[0031] Referring to the embodiment in FIG. 3, each of the radial protrusions
78 of the
illustrated C-ring 70 is aligned with and extends through an opening 84 in the
sleeve 48 between
the first outer surface 50 and the inner surface 56. When the C-ring 70 is
upwell of the partially-
conical shoulder 40 of the housing 22, the C-ring 70 has the operating
diameter shown in FIG. 3
and terminal ends 82 of C-ring 70 are in contact to form the seat defined by
the seating surface
72. An associated ball may thereafter seat against the seating surface 72 and
a pressure
differential created across the ball to move the sleeve 48 in the downwell
direction.
[0032] FIGS. 4-5 show the tool 20 with the sleeve 48 in a second position,
which is
downwell of the first position in one preferred embodiment. The upper end
surface 58 of the
sleeve 48 has moved past the ports 28, allowing fluid flow therethrough
between the flowpath
and the exterior of the tool 20. The coil spring 64 is under compression
between the sleeve 48
and the bottom connection 24, with the upper end coil 66 of the spring 64 in
contact with the
sleeve shoulder 54 and the spring lower end 68 is in contact with the upper
end surface 47 of the
bottom connection 24. In this position. the spring 64 exerts an expansive
force to urge the sleeve
48 in the upwell direction relative to the bottom connection 24.
[0033] Referring to FIG. 5, the C-ring 70 is positioned adjacent to the third
inner
surface 34. Because the third inner surface 34 has a larger diameter than the
second inner
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surface 32. the C-ring 70 radially expands towards its uncompressed shape
shown in FIG. 2. The
protrusions 78 extend past the outer surface 50 of the sleeve 48, opening the
seating surface 72
and allowing the associated restrictor element to pass through the C-ring 70,
after which the
spring 64 pushes against the sleeve shoulder 54 to move the sleeve 48 upwell
toward the first
position shown in FIG. 1. Movement of the sleeve 48 past the position shown in
FIG. I is
limited by contact of the upper end surface 58 with the housing shoulder 38.
[0034] FIG. 6 shows the sleeve 48 in an intermediate third position between
the first
position shown in FIG. I and the second position shown in FIG. 4. A restrictor
elementl00 is
seated against the seating surface 72 and obstructs fluid flow from through
the C-ring 70 to
create a differential pressure to move the sleeve 48 against the expansive
force of the spring 64.
The upper end surface 58 of the sleeve 48 is positioned such that the flow
ports 28 are in fluid
communication with the interior of the tool 20, allowing fluid communication
between the
interior of the tool 20 with the exterior of the tool 20. The C-ring 70 is
held in a closed state by
the second inner surface 32 of the housing 22. In some embodiments, a
retaining element, not
shown, may be placed in the sleeve to define this intermediate position, such
retaining element
being set such that it stops movement of the C-ring and sleeve up to a first
pressure, but allows
movement of the c-ring at a second pressure. Those of skill in the art will
appreciate that many
retaining elements such as a shear ring, shear pins, or other device may used
in conjunction with
the valve assemblies described herein. Further, mechanisms, assemblies,
methods or devices
other than a retaining element may be used for defining the intermediate third
position in a valve
assembly and any such method or element is within the scope of the valve
assemblies
contemplated herein.
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[0035] When the sleeve 48 is in the second position shown in FIG. 6, the well
operator
may thereafter cause the flow of fluids, including acid, fracing fluids, or
other fluid desired by
the operator, through the housing ports and into the formation adjacent to the
tool. In the
illustrated embodiment, flow of such materials will be blocked from downwell
flow by the ball
100 positioned against the seating surface 72, causing flow to be directed to
the surrounding
formation through the housing ports 28. After fracing, the differential
pressure across the ball
100 may be increased to cause the ball 100 to move the sleeve 48 further
downwell to the
position shown in FIG. 3, where upon the ball will be released by the
expanding C-ring.
[0036] FIG. 7 shows a hydrocarbon producing formation 200 and a system
comprising
an upper set of tools 202 positioned in an upper stage 204 of the formation
200, an intermediate
set of tools 206 positioned in an intermediate stage 208, and a lower set of
tools 210 positioned
within a lower stage 212. An upper static-seat tool 214 is positioned between
the upper set of
tools 202 and the intermediate set of tools 206 and has an internal ball seat
corresponding to an
upper-stage ball. An intermediate static-seat tool 216 is positioned between
the intermediate set
of tools 206 and the lower set of tools 210 and has an internal ball seat
corresponding to an
intermediate-stage ball. A lower static-seat tool 218 is positioned downwell
of the lower set of
tools and has an internal ball seat corresponding to a lower-stage ball. The
static-seat tools 214,
216, 218 have ball seats designed to allow fluid flow therethough in either
the upwell direction
or the downwell direction, but the ball seats are not connected to sleeves or
other movable
components.
[0037] Each tool of the sets of the tools 202, 206. 210 has the features
described with
reference to FIGS. 1-6. Each tool within the upper set of tools 202 has a C-
ring and associated
sleeve sized to be actuated by the associated upper-stage ball. Each tool
within the intermediate
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set of tools 206 has a C-ring and associated sleeve sized to be actuated by an
associated
intermediate ball smaller than the upper-stage ball. Each tool within the
lower set of tools 210
has a C-ring and associated sleeve sized to be actuated by an associated lower-
stage ball, which
is smaller than the upper ball, and the intermediate-stage ball.
[0038] To actuate the lower set of tools 210, the lower-stage ball is caused
to move
through the tubing string and upper and intermediate sets of tools 202, 206.
The lower-stage ball
is sized to pass through the upper and intermediate sets of tools 202. 206
without being inhibited
from further downwell flow by the corresponding ball seat inserts.
[0039] Upon reaching the upwell tool 210a of the lower set of tools 210, the
lower-
stage ball seats against the closed C-ring of the tool. The well operator can
then increase the
pressure within the tubing string to overcome the expansive force of the
associated coil spring
and shift the sleeve to the intermediate third position described with
reference to FIG. 6. When
desired, the pressure within the flowpath may be increased further to move the
sleeve to the
second position described with reference to FIG. 4. After moving the lower-
stage ball through
the C-ring, the pressure may be decreased to cause the lower-stage ball to
seat against the closed
C-ring of the lower tool 21 Oh of the lower set of tools 210. While the lower
set of tools 210 only
shows two tools 210a, 210b, any number of similar tools may compose this
stage. After moving
through all of such tools, the lower-stage ball seals against the lower static-
seat ball 218, which is
sized to prevent passage therethrough up to a pressure which damages the
structure of the ball
This process may then be repeated, first with the intermediate stage 208 using
the intermediate-
stage ball with the intermediate sets of tools 206 and the intermediate static-
seat tool 216, and
second with the upper stage 204 using the upper-stage ball with the upper sets
of tools 202 and
upper static seat tool 214.
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[0040] While the lower set of tools is shown comprising only three stages of
tools, the
process could be repeated for any number of tools within this stage. In
addition. the same
process described above with respect to the lower set of tools is repeatable
in similar fashion for
the intermediate and upper sets of tools 202. 206.
[0041] In an additional embodiment, the inwardly directed force exerted on the
outer
surface of the C-ring is caused by a plurality of dogs. In a preferred
embodiment, the dogs are
positioned in the openings 84 of the sleeve, and each dog has a surface
corresponding to the
curvature of the second inner surface 50 of the housing 22. The surface
profile of the dogs may
have other shapes provided the dogs can engage the protrusions 78 defining the
outer surface of
the C-ring 70 as desired. The dogs are aligned with and adapted to contact and
exert a radially
inward force on the protrusions 78 of the C-ring 70 to force the C-ring 70
into the compressed
state. In this embodiment, the openings 84 have a length along the
longitudinal axis of the sleeve
to allow the C-ring and sleeve to move in relation to the dogs.
[0042] The dogs extend past first outer surface 50 of the sleeve 48,
effectively
reducing the diameter available to the protrusions. When the C-ring is
positioned such that that
protrusions 78 engage the dogs, the terminal ends 82 are in contact and the
diameter of the
seating surface 72 and inner surface 74 of the C-ring 70 are such that a
properly-sized ball
flowing through the shifting sleeve will engage with the seat of the C-ring 70
as described with
reference to FIGS. 1-7. In one embodiment, the C-ring and sleeve are engaged
near the bottom
of each of the openings 84 such that movement of the C-ring in the downwell
direction moves
the sleeve in the same direction and movement of the sleeve in the upwell
direction. typically by
the force of a spring or other guide device, will move the C-ring in the
upwell direction.
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[0043] FIGS. 8A-8B show yet another embodiment in which a C-ring 70 starts in
an
uncompressed state and a sleeve 48 is oriented such that the protrusions 78
comprising the outer
surface of the C-ring are in a larger-diameter section 300 of the housing 22
(shown in FIG. 8A)
The sleeve 48 is then shifted to the position shown in FIG. 8B so that the
protrusions 78 or
forced from the larger-diameter section 300 to a smaller-diameter section 302
of the housing 22,
which forces the C-ring 70 to a compressed state. Thereafter, a properly-sized
ball flowing 308
through the sleeve would seat against compressed C-ring 70.
[0044] Still referring to FIG. 8A-8B, a system incorporating the above-
described
embodiments may comprise multiple ball seats, including multiple C-rings
initially in either
compressed and uncompressed states. One such system would have an upper C-ring
70 fixed to
the sleeve 48 and a lower seat 304 spaced sufficiently apart to allow a first
ball 306 of a
particular size to seat on the lower seat 304 without engaging or interfering
with the upper seat
72. Systems in which the first ball engages the upper seat 72 without
interfering with the lower
seat 304 are also possible A first ball 306 engages the lower seat 304 and,
using fluid pressure,
shifts the sleeve 48 to allow compression of the upper seat 72 by positioning
the upper seat 72
such that the outer surface 76 of the C-ring 70 engages a smaller diameter
surface 302 or
appropriately positioned dogs. The C-ring 70 of the upper seat 72 becomes
compressed and can
thereafter engage a second ball 308 of a diameter selected for use with the
upper seat 72. Those
of skill in the art will appreciate that, in the uncompressed state, the upper
C-ring 70 is
configured such that balls large enough to engage the lower seat 300 will pass
without engaging
the upper C-ring 70. Further. the upper C-ring 70, when compressed, will
engage balls with a
diameter that is too small to engage and hold pressure on the lower seat 304.
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[0045] One advantage to the system illustrated in FIGS. 8A-8B is that
restrictor
elements which would activate the sleeve if the C-ring were compressed can
pass through the
valve assembly of this embodiment to activate tools further downwell. In other
words, this
embodiment will allow the placement of valve seats configured to utilize
smaller restrictor
elements upwell of valve seats configured to use larger restrictor elements.
This will increase the
flexibility of systems incorporating such valve assemblies and can increase
the number of valves
that can be operating in a single well.
[0046] This arrangement can be continued with any number of valve assemblies
in
series per stage. with no limit on the number of sleeves. Moreover, this
system allows for an
increase in the number of stages. For example, a trio of tools using single
valve seats configured
for a 2.0 inch. 1.875 inch. and 1.75 inch ball respectively, can be placed in
a well. A second trio
of tools using double valve seats with upper valves configured for use with
2.0 inch, 1.875
inches, and 1.75 inches are then placed upwell of the first trio. The upper
valve seats of this
second trio of stages are C-rings in the uncompressed state (as described with
referenced with
respect to FIG. 8A) such that a 2.0 inch ball can pass through each upper seat
without engaging
the seat sufficiently to move the valve assembly in a downwell direction. The
lower valve seats
of the second trio comprise C-ring valve seats configured to engage a 2.0 inch
ball and to shift
the assembly in response thereto.
[0047] In operation, a first 1.75 inch ball is placed in the well and allowed
to engage
and activate the 1.75 inch stage of the first trio of stages. A first 1.875
ball is placed in the well
and allowed to engage and activate the 1.875 inch stage of the first trio of
stages. Following the
1.875 inch ball, a first 2.0 inch ball is placed in the well. This ball first
engages the lower seat of
the 2.0 inch stage of the second trio of stages causing the seat to shift and
moving the upper ring
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from an uncompressed state to a compressed state. The first 2.0 ball then
engages the lower seat
of the 1.875 inch stage of the second trio of stages, causing the seat to
shift and moving the upper
ring from an uncompressed to a compressed state. The first 2.0 inch ball then
engages the lower
seat of the 1.75 inch stage of second trio of stages, causing the seat to
shift and moving the upper
ring from an uncompressed state to a compressed state. Finally, the first 2.0
inch ball engages
the 2.0 inch stage of the first trio of stages and activates the tools
associated with the valve
assemblies of this stage.
[0048] At this point, three stages. associated with a 1.75 inch, a 1.875 inch,
and a 2.0
inch valve assembly have been activated. Further, the well now contains three
additional stages
that can be activated by sequentially placing a 1.75 inch ball, a 1.875 inch
ball, and 2.0 inch ball
into the well and allowing the balls to engage their respective seats. This
means that 6 stages,
each stage having the potential for multiple sleeves, can be activated through
use of 3 ball sizes.
Further, the embodiments arenot limited to the nesting of three sizes. Further
nesting is possible
with the valve assemblies and method of use contemplated herein, such nesting
limited only by
the ability of the uncompressed ring to allow larger sized balls to pass
without shifting the seat.
[0049] It is possible that the lower seat is not a C-ring but rather a solid
seat for the
ball or other restrictor means. Such a solid seat can be paired with the
applicants' resilient
deformable ball, described in applicant's U.S. Patent Application entitled
Valve Assembly with
Resilient Deformable Engaging Element, filed contemporaneously herewith and
incorporated by
reference herein, to allow for engagement and subsequent release of the lower
seat. In fact, any
method or device for engaging the lower seat to initially shift the sleeve is
permissible provided
that it does not prevent the treatment of any previously untreated stage.
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[0050] The ball or other restrictor devices of the present valve assemblies
can either
seat on the C-ring itself or the inside diameter of the sleeve above the C-
ring, where the sleeve is
sized sufficiently small such that the ball creates an interference seal
between the ball and sleeve,
in which case the C-ring provides only the mechanical restriction required to
impart a load on the
sleeve for shifting.
[0051] This specification contains description of preferred embodiments in
which a
specific system and apparatus are described. Those skilled in the art will
recognize that
alternative embodiments of such system and apparatus can be used. Other
aspects and
advantages of the embodiments the invention as claimed may be obtained from a
study of this
disclosure and the drawings, along with the appended claims. Moreover, the
recited order of the
steps of any method described herein is not meant to limit the order in which
those steps may be
performed.
16
