U.S. patent application number 14/811779 was filed with the patent office on 2015-11-19 for flow control system.
The applicant listed for this patent is Schlumberger Technology Corporation. Invention is credited to William Norrid.
Application Number | 20150330187 14/811779 |
Document ID | / |
Family ID | 50824304 |
Filed Date | 2015-11-19 |
United States Patent
Application |
20150330187 |
Kind Code |
A1 |
Norrid; William |
November 19, 2015 |
FLOW CONTROL SYSTEM
Abstract
A system and methodology facilitate flow control through
actuation of valves individually along a plurality of zones. The
system and methodology may be used in a variety of applications,
including fracturing operations in which the valves are selectively
actuated to control flow of fracturing fluid to specific zones of a
formation. In fracturing applications, a well string is provided
with a plurality of stages positioned sequentially along a
plurality of surrounding zones, e.g. well zones. Each stage may be
uniquely actuated relative to other stages by dropping a ball or
balls down to the desired stage and actuating the valve via
application of pressure.
Inventors: |
Norrid; William;
(Westminster, CO) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Schlumberger Technology Corporation |
Sugar Land |
TX |
US |
|
|
Family ID: |
50824304 |
Appl. No.: |
14/811779 |
Filed: |
July 28, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13693450 |
Dec 4, 2012 |
9121273 |
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14811779 |
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Current U.S.
Class: |
166/308.1 ;
166/318; 166/373 |
Current CPC
Class: |
E21B 43/26 20130101;
E21B 43/14 20130101; E21B 2200/06 20200501; E21B 34/14
20130101 |
International
Class: |
E21B 34/12 20060101
E21B034/12; E21B 43/26 20060101 E21B043/26; E21B 43/14 20060101
E21B043/14 |
Claims
1. A system for fracturing, comprising: a well string having a
plurality of fracturing stages positioned sequentially along a
plurality of corresponding well zones, each fracturing stage
comprising: a sliding sleeve movable to expose an outlet port
through which fracturing fluid may be injected into a corresponding
well zone; at least one ball seat compressible between a radially
expanded position and a radially contracted position within the
sliding sleeve, the radially contracted position blocking passage
of a ball used to actuate the sliding sleeve; and a restriction
positioned within the sliding sleeve, the restriction being sized
to compress the at least one ball seat to the radially contracted
position when the at least one ball seat is forced into the
restriction; the number of ball seats changing in sequential
fracturing stages of the plurality of fracturing stages in a manner
which enables capture of an ultimate ball seat in the restriction
when it is desired to open the outlet port of a specific fracturing
stage.
2. The system as recited in claim 1, wherein the well string is
deployed in a deviated wellbore between a heel and a toe of the
deviated wellbore.
3. The system as recited in claim 2, wherein each sequential
fracturing stage moving from the toe toward the heel has a larger
number of ball seats than the previous fracturing stage for a given
group of fracturing stages.
4. The system as recited in claim 3, wherein the number of ball
seats increases by one for each sequential fracturing stage in the
given group of fracturing stages.
5. The system as recited in claim 3, wherein the plurality of
fracturing stages comprises a plurality of given groups of
fracturing stages.
6. The system as recited in claim 3, wherein some of the fracturing
stages comprise spacers located within the sliding sleeve on an
opposite side of the restriction from the side on which the ball
seats are initially located.
7. The system as recited in claim 3, wherein the ball is able to
pass through the ball seat once the ball seat is forced past the
restriction.
8. The system as recited in claim 7, wherein the ball is a
dissolvable ball.
9. The system as recited in claim 5, wherein each group of
fracturing stages utilizes balls having a diameter that differs
from the diameter of balls utilized by another group of fracturing
stages.
10. The system as recited in claim 1, wherein each ball seat
comprises a shear member which resists passage of the ball seat
through the restriction until sufficient pressure is applied to a
ball seated against the ball seat to force the ball seat through
the restriction, provided sufficient space remains on a downhole
side of the restriction to receive the ball seat.
11. A method for actuating valves sequentially, comprising:
utilizing a ball and a ball seat in each stage of a plurality of
stages to enable selective actuation of a valve in each stage and
to thus enable a selective outflow of fluid at each stage;
positioning a different number of ball seats in each stage to
enable individual control over the valves in different stages;
using balls under pressure to force ball seats past a restriction
until a sufficient number of ball seats become stacked within a
given stage to hold an ultimate ball seat at the restriction; and
applying pressure against the ball held by the ultimate ball seat
at the given stage to actuate the valve.
12. The method as recited in claim 11, further comprising
positioning the plurality of stages along a well string in a
deviated wellbore.
13. The method as recited in claim 12, further comprising
sequentially opening valves in sequential stages of the plurality
of stages to direct fracturing fluid to corresponding well
zones.
14. The method as recited in claim 12, wherein positioning
comprises positioning an increasing number of ball seats in each
sequential stage of a group of stages moving from a tow of the
wellbore toward a heel of the wellbore.
15. The method as recited in claim 14, further comprising using
spacers of decreasing length in sequential stages, moving in a
direction from the toe to the heel, to hold the appropriate
ultimate ball seat in the restriction of each sequential stage.
16. The method as recited in claim 11, further comprising forming
the restriction as a reduced diameter within a sliding sleeve used
to actuate the valve.
17. The method as recited in claim 11, further comprising using
dissolvable balls to actuate the valves.
18. A system for controlling flow, comprising: a flow control stage
comprising a sleeve having an internal restriction, the sleeve
being positioned to interact with a flow port for controlling flow
between an interior and exterior of the flow control stage, the
flow control stage further comprising a plurality of stackable
members disposed initially on a first side of the restriction, each
stackable member being radially compressible to enable movement of
individual stackable members past the restriction, via a ball, for
collection on a second side of the restriction, the individual
stackable members accumulating on the second side until a
subsequent stackable member is blocked from passing the
restriction, thus providing an obstacle to a subsequent ball used
to shift the sleeve and to thus open the flow port.
19. The system as recited in claim 18, wherein the flow control
stage is a fracturing stage positioned with a plurality of
additional fracturing stages in a well string located in a wellbore
to facilitate fracturing of a surrounding formation.
20. The system as recited in claim 19, wherein the individual
stackable members in each fracturing stage comprise ball seats.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 13/693,450, filed Dec. 4, 2012, which is
incorporated herein by reference in its entirety.
BACKGROUND
[0002] Hydrocarbon fluids such as oil and natural gas may be
obtained from a variety of formations. In some applications, the
formations are fractured to facilitate oil and/or gas flow. During
fracturing operations, fracturing fluids are pumped downhole and
injected into the surrounding formation under pressure to create
cracks or fractures through the formation. The formation fractures
increase the conductivity of the formation which enhances
hydrocarbon fluid recovery by improving fluid flow from the
formation to the wellbore or wellbores drilled into the
formation.
SUMMARY
[0003] In general, the present disclosure provides a system and
method of actuating valves individually along a plurality of zones.
The system and methodology may be used in a variety of
applications, including fracturing operations in which the valves
are selectively actuated to control flow of fracturing fluid to
specific zones of the formation. In fracturing applications, a well
string is provided with a plurality of stages positioned
sequentially along a plurality of corresponding zones, e.g. well
zones. Each stage may be uniquely actuated relative to other stages
by dropping a ball or balls down to the desired stage and actuating
the valve via application of pressure.
[0004] However, many modifications are possible without materially
departing from the teachings of this disclosure. Accordingly, such
modifications are intended to be included within the scope of this
disclosure as defined in the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] Certain embodiments of the disclosure will hereafter be
described with reference to the accompanying drawings, wherein like
reference numerals denote like elements. It should be understood,
however, that the accompanying figures illustrate the various
implementations described herein and are not meant to limit the
scope of various technologies described herein, and:
[0006] FIG. 1 is a schematic illustration of a well system having a
well string with a plurality of fracturing stages deployed along a
wellbore, according to an embodiment of the disclosure;
[0007] FIG. 2 is a cross-sectional view of an example of a flow
control stage, e.g. a fracturing stage, that may be used with the
well system illustrated in FIG. 1, according to an embodiment of
the disclosure;
[0008] FIG. 3 is a cross-sectional view of the flow control stage
illustrated in FIG. 2 but in a different operational position,
according to an embodiment of the disclosure;
[0009] FIG. 4 is a cross-sectional view of the flow control stage
illustrated in FIG. 2 but in a different operational position,
according to an embodiment of the disclosure;
[0010] FIG. 5 is a cross-sectional view of the flow control stage
illustrated in FIG. 2 but in a different operational position,
according to an embodiment of the disclosure;
[0011] FIG. 6 is an enlarged view of a portion of the flow control
stage illustrated in FIG. 5, according to an embodiment of the
disclosure;
[0012] FIG. 7 is a schematic illustration of an example of a flow
control system having a plurality of flow control stages arranged
in a deviated wellbore, according to an embodiment of the
disclosure;
[0013] FIG. 8 is a schematic illustration similar to the flow
control system illustrated in FIG. 7 but in a different operational
configuration, according to an embodiment of the disclosure;
and
[0014] FIG. 9 is a schematic illustration of another example of a
flow control system having a plurality of flow control stages
arranged in a deviated wellbore, according to an embodiment of the
disclosure.
DETAILED DESCRIPTION
[0015] In the following description, numerous details are set forth
to provide an understanding of some embodiments of the present
disclosure. However, it will be understood by those of ordinary
skill in the art that the system and/or methodology may be
practiced without these details and that numerous variations or
modifications from the described embodiments may be possible.
[0016] The present disclosure generally involves a system and
methodology for actuating valves individually along a plurality of
zones. The technique may be used in a variety of applications to
control flow with respect to the plurality of zones. For example,
the technique may be used in fracturing operations to selectively
actuate valves which control flow of fracturing fluid to specific
zones of the formation. In fracturing applications, a well string
may be provided with a plurality of stages positioned sequentially
along a plurality of corresponding zones, e.g. surrounding well
zones. Each stage may be uniquely actuated relative to other stages
by dropping a ball or balls down to the desired stage and actuating
the valve via application of pressure.
[0017] In a specific example, the fracturing system comprises a
well string having a plurality of fracturing stages positioned
sequentially along a plurality of corresponding well zones. Each
fracturing stage comprises a sleeve, e.g. a sliding sleeve, which
may be moved by pressure applied against a dropped ball landed on a
ball seat to operate a valve and thus expose an outlet port.
Fracturing fluid may be injected through the outlet port and into a
corresponding well zone. Each fracturing stage may comprise at
least one ball seat and often a plurality of ball seats which are
compressible between a radially expanded position and a radially
contracted position within the sliding sleeve. Each ball seat may
be transitioned to the radially contracted position by moving the
ball seat into engagement with a restriction positioned within the
sleeve. When a given ball seat is radially contracted by the
restriction, the dropped ball is blocked from passage
therethrough.
[0018] Each fracturing stage uses a unique number of ball seats to
control the sequence of actuation, and thus the injection of
fracturing fluid, relative to the other stages. When a ball is
dropped, the ball engages the ball seat contracted by the
restriction and moves the ball seat past the restriction. Once the
ball seat moves past the restriction, the ball seat expands
radially to allow the ball to move through the ball seat and on to
the next stage. After passing through the restriction, the ball
seats accumulate on the downstream side of the restriction within
the sleeve until the accumulated ball seats prevent passage of the
ultimate or last ball seat. Because the ultimate ball seat cannot
pass through the restriction when contacted by a dropped ball,
increased pressure causes the ball to shift the sleeve and open the
valve/outlet port, thus allowing injection of fracturing fluid at
that particular fracturing stage. The fracturing stages may be
designed such that different numbers of ball seats pass through the
restriction before being retained in the restriction to enable
actuation of the valve at a particular stage. This allows the
fracturing stages to be actuated according to a desired pattern,
e.g. a sequential pattern moving from a toe to a heel of a deviated
wellbore.
[0019] The fracturing stages and corresponding sleeves may be
designed to provide a large number of fracturing stages which are
all actuated by balls of the same diameter. By using the stacked
ball seats, or other stackable members, the number of fracturing
stages that can be actuated by the same size ball is substantially
increased. The stackable members are progressively moved from one
side of the restriction (e.g. a reduced inside diameter of the
sleeve) to the other side of the restriction until there is no more
room for the next stackable member/ball seat to pass the
restriction. At this point, a ball is dropped to engage the
radially contracted ball seat within the restriction so pressure
may be applied to shift the sliding sleeve to an open flow
position. The balls dropped to operate the plurality of stages in a
given fracturing system may be made from a dissolvable material so
that each ball may be dissolved after completion of the fracturing
operation at a given fracturing stage.
[0020] Referring generally to FIG. 1, an embodiment of a flow
control system, e.g. a flow control multi-stage fracturing system,
is illustrated. By way of example, the flow control system may be
used in a variety of fracturing applications and other applications
in which it is useful to independently control flow at a plurality
of stages. In a variety of fracturing applications, the well system
may be used in deviated wellbores to facilitate sequential
actuation of numerous individual fracturing stages via dropped
balls having a common diameter. The specific components of the
fracturing system or other type of flow control system may vary
based on parameters related to the surrounding environment and the
function of the overall system.
[0021] In the example illustrated in FIG. 1, a flow control system
20, e.g. a formation fracturing system, is illustrated as
comprising a well string 22 deployed in a wellbore 24. Wellbore 24
may comprise a deviated, e.g. horizontal, wellbore section 26 which
extends between a heel 28 and a toe 30 section of the well. Well
string 22 comprises a plurality of flow control stages 32, e.g.
fracturing stages, positioned sequentially along the well string 22
at corresponding well zones 34. In some applications, the well
string 22 may comprise a plurality of packers 36 positioned between
the fracturing stages 32. It should be noted the flow control
stages 32 also may be utilized in vertical wellbores.
[0022] Depending on the flow control application, each flow control
stage 32 may comprise a variety of components and features. For
example, each flow control stage 32 may be in the form of a
fracturing stage having a sleeve 38, e.g. a sliding sleeve, which
is coupled to a valve 39 that may be actuated to control the
outflow of fluid, e.g. outflow of fracturing fluid. By way of
example, valve 39 may be in the form of sliding sleeve 38 working
in cooperation with a port 40, such as an outlet port. However,
port 40 may be selectively opened by a variety of other types of
valves 39, and sleeve 38 may comprise a variety of connection
members coupled to the valve for actuating the valve 39. As
described in greater detail below, the sleeves 38 may be actuated
by balls dropped down through well string 22 for engagement with a
corresponding ball seat. Pressure may be applied along an interior
of the well string 22 and against the ball and ball seat to shift
the sleeve 38, thus allowing outflow of fluid, e.g. fracturing
fluid, through the corresponding port 40. It should be noted that
the term "ball" is used herein to generally represent dropped
objects used to actuate the individual stages 32. Accordingly, the
dropped balls may have a variety of shapes and configurations,
including spherical shapes and other suitable shapes designed to
engage corresponding ball seats. In some applications, the balls
may be in the form of darts, cylinders with a hemispherical lead
end, distorted spheres, and/or other suitable shapes and
configurations.
[0023] Referring generally to FIG. 2, an embodiment of stage 32 is
illustrated in a form which may be employed in a fracturing
operation. In this embodiment, the stage 32 comprises a plurality
of individual stackable members 42 disposed within sliding sleeve
38. By way of example, the stackable members 42 may be in the form
of ball seats each having a seat 44 for receiving a ball 46 (see
FIG. 3). In this example, each ball seat 42 is radially
compressible between a radially expanded position and a radially
contracted position within the sliding sleeve 38. The radially
contracted position blocks passage of ball 46 while the radially
expanded position allows ball 46 to pass through an open interior
48 of the ball seat. It should be noted that when ball seats 42 are
in the radially expanded state, the seat 44 of each ball seat 42
provides a seating profile but the profile is sufficiently large to
allow the ball 46 to pass through the interior 48 of each expanded
ball seat 42. However, when a given ball seat 42 is radially
contracted the diameter of its interior 48 is reduced and the
seating profile 44 becomes a seating surface which prevents passage
of ball 46. Effectively, the ball 46 seats against seat 44 when the
ball seat 42 is transitioned to its radially contracted state.
[0024] To facilitate the radial contraction, each stage 32 further
comprises a restriction 50 which extends inwardly from the sliding
sleeve 38. By way of example, restriction 50 may comprise a reduced
diameter section of the sleeve 38. The stackable members 42, e.g.
ball seats 42, initially are positioned in sliding sleeve 38 on a
first side 52 of restriction 50, as best illustrated in FIG. 2. In
many fracturing applications, the first side 52 of restriction 50
is a region within sleeve 38 on an upstream side of the restriction
50 relative to the downward flowing fracturing fluid. The stack of
ball seats 42 on the first side 52 effectively moves the lead ball
seat 42 into restriction 50 which radially compresses the ball seat
to the radially contracted position which prevents passage of ball
46. Consequently, movement of ball 46 down through the stage 32
causes the ball 46 to seat against surface 44 of the particular
ball seat 42 contracted within restriction 50. If there is nothing
to block movement of the ball seat to a second side 54, e.g. a
downstream side, of the restriction 50 within sleeve 38, pressure
applied against ball 46 causes the ball seat 42 to move past the
restriction 50 and into the interior of sliding sleeve 38 at the
second side 54. It should be noted that the ball seats 42 may be
continually moved into restriction 50 by the natural flow of
fracturing fluid, by the resistance of the ball 46 moving through
the interior of the ball seats 42, by a spring mechanism within the
sliding sleeve 38, and/or by other suitable techniques which
continually load the lead ball seat 42 into restriction 50.
[0025] Each time another ball 46 is moved through the stage 32, a
subsequent ball seat 42 is forced past restriction 50 for
accumulation within the sliding sleeve 38 at second side 54, as
best illustrated in FIG. 3. Once at second side 54, the ball seat
42 once again expands to allow ball 46 to pass through ball seat
interiors 48 and on to the next sequential stage 32, as represented
by arrow 56 in FIG. 3. Continued passage of balls 46 moves
additional ball seats 42 to the second side 54 until the stack of
ball seats prevents the ultimate ball seat 42 from moving past the
restriction 50, as illustrated in FIG. 4. Consequently, ball 46
also is prevented from passing restriction 50. Continued
application of pressure against ball 46 and the ultimate ball seat
42 causes the sliding sleeve 38 to shift and expose flow port 40,
as illustrated best in FIG. 5. In the example illustrated, flow
port 40 comprises a plurality of flow ports extending radially
through a supporting fracturing stage housing 58. The pressurized
fracturing fluid is thus forced out through the port 40 and is
injected into the corresponding, e.g. surrounding, well zone 34 of
the formation.
[0026] Referring generally to FIG. 6, an enlarged example of a
portion of the fracturing stage 32 is illustrated. In this example,
each of the ball seats 42 is engaged with a shear member 60, such
as a plurality of shear pins, which extends into cooperation with
sliding sleeve 38. As each ball seat 42 moves toward restriction
50, the shear pins 60 (or other suitable shear member) slide along
a corresponding slot or slots 62 extending longitudinally along an
inner surface of the sliding sleeve 38. The shear member 60 guides
the ball seats 42 and prevents relative rotation of the ball seat
with respect to sliding sleeve 38 and restriction 50.
[0027] If a given ball seat 42 is forced past restriction 50, the
shear member 60 is sheared to release the ball seat 42 from
restriction 50. However, the ultimate ball seat 42 retained within
restriction 50 may remain in engagement with the shear member 60
and sliding sleeve 38 so as to prevent rotation of the ultimate
ball seat 42 with respect to the restriction 50 while the ball seat
42 is held within restriction 50. In some applications, each shear
member 60 may comprise a spring plunger 64 to help maintain
engagement between the ball seat 42 and the surrounding sliding
sleeve 38 as the ball seat 42 is transitioned to the radially
contracted configuration within restriction 50. Spring plunger 64
also may be used to clear any remaining bits of the shear member
after shearing.
[0028] In various fracturing operations and other flow control
operations, the sleeves 38 are designed to provide a relatively
large number or group of fracturing stages 32 that may all be
operated with the same size dissolvable ball 46. This enables
stimulation of an entire well, or a substantial region of a well,
without employing additional ball seat clean out operations. When
the ball seats 42 reside in either first side 52 or second side 54
of sleeve 38, the ball seats 42 expand to the radially expanded
position which allows balls 46 to pass along the interior 48 of the
expanded ball seats 42. The restriction 50 may be in the form of a
reduced inside diameter which forces the ball seats 42 to collapse
and catch the ball 46. Increased pressure applied down through well
string 22 via fluid shears the shear member 60 and allows the ball
seat 42 and ball 46 to travel downhole to the larger diameter of
second side 54. The ball seat 42 continues to travel through second
side 54 until stopping against a shoulder 66 (see FIG. 5) or
against the previously stacked ball seats 42.
[0029] When a given ball seat 42 is moved past restriction 50 and
into second side 54, the next sequential ball seat 42 is moved into
the reduced inside diameter of restriction 50 and is stopped when
the shear member 60 seats against the end of the slot or slots 62.
The spring plunger 64 may be used to remove any remaining portions
of the shear member or members after movement of the previous ball
seat 42 past restriction 50. Next, a similarly sized ball 46 is
dropped and lands on the newly created seat 44 of the ball seat 42
positioned within restriction 50. The pressure again increases
until the shear member 60 is sheared and the ball seat 42 and ball
46 are again released. This process is repeated, and the ball seats
42 are stacked up in second side 54 until the ultimate ball seat 42
shoulders out on the stack of ball seats 42 on second side 54, as
illustrated in FIGS. 4-6. The increased pressure applied by the
fluid in well string 22, e.g. fracturing fluid, is then able to
transfer the force to the sliding sleeve 38 and to move the sliding
sleeve 38 to a position opening port 40. Fluid, e.g. fracturing
fluid, may then be distributed through port 40 to the corresponding
well zone 34. It should be noted that in some applications, the
sliding sleeve 38 may initially be held in a closed position by a
shear member 68, e.g. shear pins, which are sheared upon buildup of
pressure against the ultimate ball seat 42 and corresponding ball
46.
[0030] Referring generally to FIG. 7, an example of a system 20 is
illustrated as comprising a plurality of fracturing stages 32. In
this example, the fracturing stages 32 are actuated to enable
injection of fracturing fluid into the corresponding well zone 34
in sequential order beginning with the fracturing stage 32 at the
toe 30 of deviated wellbore 26. The first fracturing stage 32 at
toe 30 is actuated to an open flow position by dropping the first
ball 46 through the preceding/uphole stages 32. As the first ball
46 passes through the plurality of fracturing stages 32, an
individual stackable member 42, e.g. ball seat, is moved through
the restriction 50 into the second side region 54 of each
fracturing stage. The first ball 46 seats in the initial fracturing
stage 32 at toe 30 to enable actuation of the corresponding
valve/sliding sleeve for fracturing of the corresponding well zone
34. The second ball 46, of a similar diameter, passes through each
of the fracturing stages 32 and moves a second stackable
member/ball seat 42 through the restriction 50 of each fracturing
stage 32 until reaching the penultimate fracturing stage 32.
[0031] At the penultimate fracturing stage 32, the second stackable
member/ball seat 42 is prevented from passing through the
restriction 50. Consequently, the ball seat 42 is held in its
radially contracted position and blocks passage of ball 46, as
illustrated in FIG. 8. The pressure of the fracturing fluid is then
used to shift the sliding sleeve 38 and to expose flow port 40, as
further illustrated in FIG. 8. This process may be repeated to
sequentially actuate each subsequent fracturing stage 32 until
reaching the last stage to be actuated, e.g. the fracturing stage
32 proximate heel 28.
[0032] In the example illustrated, each sequential fracturing stage
32 comprises an increased number of stackable members/ball seats 42
which enables the sequential opening of flow ports 40 in each
sequential fracturing stage 32 moving from, for example, the toe 30
toward the heel 28. By way of example, a plurality of the
sequential fracturing stages 32 may each comprise a single
additional ball seat 42 relative to the preceding fracturing stage
when moving in a direction from the toe 30 toward the heel 28.
Single size balls 46 may be used to individually actuate the
sequential fracturing stages 32. As described in greater detail
below, however, the fracturing stages 32 may be divided into groups
of fracturing stages in which each group is actuated by balls
having a common diameter or size.
[0033] Furthermore, if the restriction 50 is located at a common
area in each sliding sleeve 38, spacers 70 may be used in
cooperation with the stackable members/ball seats 42 in the second
side region 54 of each fracturing stage 32. The spacers 70 are
sized to hold the appropriate ball seat 42 within restriction 50
when that particular fracturing stage 32 is to be actuated to an
open flow position. As illustrated, each sequential spacer 70 is
shorter by the axial length of a single ball seat 42 so as to place
the ultimate ball seat 42 within restriction 50 during the
appropriate cycle for opening that fracturing stage and releasing
fracturing fluid into the corresponding well zone 34 of the
surrounding formation. In this example, the first fracturing stage
32 and the last fracturing stage 32 in a given group of fracturing
stages 32 may be constructed without spacers 70.
[0034] Referring generally to FIG. 9, another embodiment of the
system 20 is illustrated. In this example, the stages 32 similarly
comprise fracturing stages designed to control the flow of
fracturing fluid injected into corresponding well zones 34. In this
example, the fracturing stages 32 are actuated to enable injection
of fracturing fluid into the corresponding well zones 34 in
sequential order beginning with the fracturing stage 32 at the toe
30 of deviated wellbore 26. However, the overall number of
fracturing stages 32 is divided into a plurality of groups of
fracturing stages 32, such as a first group 72 operated by a
common, smaller diameter ball 46 and a second group 74 operated by
a common, larger diameter ball 46. It should be noted the overall
number of stages 32 may be divided into additional groups of stages
in which each group of stages is operated by a specific ball type,
e.g. a specifically sized ball. In this type of application, the
smaller sized balls 46 are initially used to sequentially actuate
the fracturing stages 32 for the first group 72, according to the
methodology described above. Subsequently, larger sized balls 46
are used to sequentially actuate the fracturing stages 32 for the
second group 74, according to the methodology described above. This
process also may be repeated for additional groups of fracturing
stages 32. It should further be noted that FIG. 7-9 illustrate a
portion of the fracturing stages 32 in the overall sequence of
fracturing stages 32 due to the overall length of the fracturing
system embodiment.
[0035] The construction of system 20 may vary substantially
according to the parameters of a given operation, and the
sequential flow control may be used in fracturing operations, other
well operations, and non-well operations in which fluid flow is
sequentially controlled with respect to a plurality of
corresponding zones. Additionally, the outflow of fluid through
port 40 may be controlled by sliding sleeves or a variety of other
valve types, including ball valves, piston controlled valves, and
other suitable valve types. Sleeve 38 also may be constructed in a
variety of actuator forms suitable for actuating a given valve
type. Similarly, the ball seats 42 may be designed in a variety of
shapes and configurations. In some examples, the ultimate ball seat
42 comprises seat 44 which forms a sealing engagement with ball 46,
while the earlier shifted ball seats are simply stackable members
which serve to fill the length of second side region 54 until the
ultimate ball seat 42 is received in restriction 50.
[0036] Many types of balls 46 also may be used to selectively
actuate stages 32. For example, spherical balls, partially
spherical balls, darts, cylinders, plugs, and other suitable balls
may be used to both shift stackable members/ball seats through the
restriction while also engaging the ultimate ball seat in a manner
which enables shifting of the stage to an open flow configuration.
The balls 46 also may be made from a variety of dissolvable
materials or otherwise frangible materials which allow the ball to
be broken down into smaller pieces for removal from the stage upon
completion of the fracturing or other flow control operation. The
number and arrangement of stages also may vary greatly from one
application to another. In some fracturing operations, for example,
30, 50, 75, or even 100 or more stages may be utilized to
facilitate fracturing in numerous well zones.
[0037] Although a few embodiments of the disclosure have been
described in detail above, those of ordinary skill in the art will
readily appreciate that many modifications are possible without
materially departing from the teachings of this disclosure.
Accordingly, such modifications are intended to be included within
the scope of this disclosure as defined in the claims.
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