Note: Descriptions are shown in the official language in which they were submitted.
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TECHNIQUE AND APPARATUS FOR COMPLETING MULTIPLE ZONES
This is a divisional of Application Serial
No. 2,529,913, filed December 13, 2005.
BACKGROUND
5[001] The present invention generally relates to a
technique and apparatus to complete multiple zones.
[002] For purposes of enhancing production from a
subterranean well, the layers of the well may be fractured
using a pressurized proppant-containing fracturing fluid or
other treating fluids such as acid. The layers typically
are fractured one at a time by directing fracturing fluid to
the layer being fractured and isolating the other layers.
[003] A conventional fracturing system includes surface
pumps that pressurize fracturing fluid, which may be
communicated downhole via the central passageway of a
tubular string. The string extends downhole through a
wellbore that traverses the various layers to be fractured;
and the string may include valves (sleeve valves, for
example) that are generally aligned with the layers so that
the valves may be used to control fluid communication
between the central passageway of the string and the layers.
Thus, when a fracturing operation is performed on one of the
layers, one of the valves is opened so that fracturing fluid
may be communicated through the opened valve to the
associated layer.
[004] To remotely operate the valves from the surface of
the well, the valves may contain many different size ball
seats. More specifically, to target and actuate the valves,
differently sized balls may be dropped into the central
passageway of the string from the surface of the well. Each
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ball size may be uniquely associated with a different valve,
so that a particular ball size is used to actuate a specific
valve. The smallest ball opens the deepest valve. More
particularly, a free-falling ball lodges, or is "caught" by,
a ball seat of the targeted valve. To discriminate between
the different valves, each ball seat of the string has a
different diameter.
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[005] After a ball lodges in a ball seat, fluid flow through the central
passageway
of the string becomes restricted, a condition that allows fluid pressure to be
applied from
the surface of the well for purposes of exerting a downward force on the ball.
The ball
seat typically is attached to a sleeve of the valve to transfer the force to
the sleeve to
cause the valve to open.
[006] The annular area that is consumed by each ball seat restricts the cross-
sectional flow area through the string (even in the absence of a ball), and
the addition of
each valve (and ball seat) to the string further restricts the cross-sectional
flow area
through the central passageway of the string, as the flow through each ball
seat becomes
progressively more narrow as the number of ball seats increase. Thus, a large
number of
valves may significantly restrict the cross-sectional flow area through the
string.
[007] As an alternative to the ball seat being located in the string as part
of the
valves, a single activation tool may be selectively positioned in side the
central
passageway of the string to operate the valves. More specifically, a valve
actuation tool
may be lowered downhole by a conveyance mechanism (a slickline, for example)
to the
valve to be opened and to close previously-opened valves.
[008] A challenge with this alternative is that the fracturing pumps at the
surface
of the well may need to be idled after each layer is fractured. Furthermore,
each valve
typically is closed after its associated fracturing operation. The reclosure
of the valves
demands that the seals and sealing surfaces withstand the fracturing
operations without
damage.
[009] Thus, there is a continuing need for a technique and/or arrangement to
address one or more of the problems that are set forth above as well as
possibly address
one or more problems that are not set forth above.
SUMMARY
[0010] In an embodiment of the invention, an apparatus that is usable with a
well
includes a string and a plurality of tools that are mounted in the string. The
string
includes a passageway. The tools are mounted in the string and are adapted to
be placed
in a state to catch objects (free-falling objects and/or pumped-down objects,
as just a few
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examples) of substantially the same size, which are
communicated downhole through the passageway.
[0011] In another embodiment of the invention, an
apparatus that is usable with a well includes a tubular
member, a first tool and a second tool. The tubular member
includes a passageway. The first tool is attached to the
tubular member, and the first tool is adapted to be placed
in a state to catch a first object that is communicated
through the passageway and perform an operation after
catching the first object. The second tool is attached to
the tubular member and is adapted to transition to a state
to catch a second object communicated through the passageway
in response to the operation.
[0012] In yet another embodiment of the invention, a
technique that is usable with a well includes providing a
string that has a plurality of tools and a passageway that
extends through the tools. The technique includes without
running an activation tool into the passageway; and
selectively activating the tools of the string to cause each
activated tool to transition from a first state in which the
activated tool is configured to allow a free-falling object
to pass through the passageway to a second state in which
the activated tool is configured to catch the free-falling
object.
[0012A] According to one aspect of the present invention,
there is provided a system usable with a well, comprising: a
string to be run into the well and comprising a passageway;
and a valve attached to the string, the valve comprising a
housing having openings to establish fluid communication
between the passageway and a region outside of the string,
wherein at least one of the openings comprises a slot having
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a longitudinal length at least five times greater than a
width of the slot.
[0013] Advantages and other features of the invention
will become apparent from the following description, drawing
and claims.
BRIEF DESCRIPTION OF THE DRAWING
[0014] Fig. 1 depicts a fracturing system according to an
embodiment of the invention.
[0015] Figs. 2 and 3 depict a valve in a closed state and
before being placed in a ball catching state according to an
embodiment of the invention.
[0016] Fig. 4 depicts the valve in a closed state and
after being placed in a ball catching state according to an
embodiment of the invention.
[0017] Figs. 5 and 6 depict the valve in its open state
according to an embodiment of the invention.
[0018] Fig. 7 is a flow diagram depicting a technique to
fracture layers in a multiple layer well according to an
embodiment of the invention.
[0019] Fig. 8 is a perspective view illustrating surface
features on a bottom end of a collet sleeve of the valve
according to an embodiment of the invention.
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[0020] Figs. 9 and 10 depict different states of a valve that uses a C-ring as
a ball
catcher in accordance with an embodiment of the invention. [0021 ] Fig. 11 is
a perspective view of a valve housing according to another
embodiment of the invention.
DETAILED DESCRIPTION
[0022] Referring to Fig. 1, an embodiment 10 of a fracturing system includes a
string 12 that extends into a wellbore 11 that traverses N layers 15 (layers
151, 152, 153 ..
15N_1 and 15N, depicted as examples) of the well. As depicted in Fig. 1, the
string 12
includes valves 14 (valves 141, 142, 143 ... 14N_1 andl4N, depicted as
examples), each of
which is associated with a particular layer 15. For example, the valve 143 is
associated
with the layer 153. Thus, to fracture a particular layer 15, the associated
valve 14
(initially run downhole in a closed state) is opened by dropping a ball and
pumping up,
which shifts the sleeve valve open (as described below) to allow communication
between
the central passageway of the string 12 and the associated layer 15. This
communication,
in turn, permits fracturing fluid and pressure to be routed to the associated
layer 15.
[0023] More specifically, in some embodiments of the invention, each valve 14
controls communication between a central passageway of the string 12 and an
annular
region that surrounds the valve 14. When the string 12 is run downhole, all of
the valves
14 are initially closed. However, the valves 14 are successively opened one at
a time in a
predetermined sequence (described below) for purposes of fracturing the layers
15.
[0024] As a more specific example, in some embodiments of the invention, the
valves are opened in a sequence that begins at the bottom of the string 12
with the lowest
valve 14N, proceeds uphole to the next immediately adjacent valve 14, then to
the next
immediately adjacent valve 14, etc. Thus, the valve 14N is opened before the
valve 14N_1i
the valve 143, is opened before the valve 142, etc.
[0025] For purposes of opening a particular valve 14, a free-falling or pumped-
down object is deployed from the surface of the well into the central
passageway of the
string 12. It is assumed below for purposes of clarifying the following
discussion that the
object is a spherical ball. However, it is understood that in other
embodiments of the
invention, other object types and/or differently-shaped objects may be used.
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[0026] In some embodiments of the invention, a ball of the same dimension may
be used (although different size balls may be used in other embodiments of the
invention)
to open all of the valves 14, as only one of the previously-unopened valves
(called the
"targeted valve" herein) is in a "ball catching state" at any one time. More
specifically, in
accordance with some embodiments of the invention, all of the balls that are
pumped or
dropped downhole for purposes of opening one of the valves 14 may have
diameters that
vary less than approximately 0.125 inches from each other.
[0027] As described below, initially, all of the valves 14 are closed, and
none of
the valves 14 are in ball catching states. When a particular valve 14 opens,
the valve 14
places the next valve 14 in the sequence in the ball catching state. When in
the ball
catching state, the valve 14 forms a seat that presents a restricted cross-
sectional flow
passageway to catch a ball that is dropped into the central passageway of the
string 12.
For the sequence that is described above, the unopened valves 14 that are
located above
the unopened valve 14 that is in the ball catching state allow the ball to
pass through.
[0028] After the ball lodges in the ball catcher of the targeted valve 14, the
ball
significantly restricts, if not seals off, the central passageway of the
string 12 below the
ball so that fluid pressure may be applied above the ball to generate a force
to cause the
valve to open, as further described below.
[0029] As a more specific example, a ball may be dropped from the well's
surface
into the central passageway of the string 12 for purposes of opening a
previously-
unopened valve 14N that has previously been placed in a ball catching state.
In response
to the fluid pressure that is applied to the resultant restricted central
passageway, the
valve 14N opens to allow a fracturing operation to be performed on the
associated layer
15N. The opening of the valve 14N, in turn, places the next valve 14N_1 in the
sequence in
the ball catching state. Once the fracturing operation on the layer 15N is
complete,
another ball is dropped into the central passageway of the string 12 for
purposes of
opening the valve 14N_1 so that the layer 15N_1 can be fractured. Thus, this
sequence
continues until the last valve 141 is opened, and the associated layer 151 is
fractured.
[0030] As a more specific example, in accordance with some embodiments of the
invention, Figs. 2 and 3 depict upper 14A and lower 14B sections of an
exemplary valve
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14 that is closed and has not been placed in ball catching state (i.e., the
valve 14 is in its
initial states when run into the well). Thus, as depicted in Figs. 2 and 3,
the valve 14
does not restrict its central passageway 24. As further described below, the
valve 14 may
be subsequently placed in the ball catching state, a state in which the valve
14 compresses
a collet sleeve 30 to form an annular seat to catch the ball.
[0031 ] Turning now to the specific details of the embodiment that is depicted
in
Figs. 2 and 3, in some embodiments of the invention, the valve 14 includes a
generally
cylindrical upper housing section 20 (Fig. 2) that is coaxial with a
longitudinal axis 26 of
the valve 14. The upper housing section 20 includes an opening 19 to
communicate
fluids (well fluid, fracturing fluid, etc.) with the portion of the string 12
that is located
above and is attached to the upper housing section 20. At its lower end, the
upper
housing section 20 is coaxial with and is connected to a generally cylindrical
lower
housing section 22 (Figs. 2 and 3). As depicted in Fig. 2, in some embodiments
of the
invention, a seal such as an 0-ring 23 may be present between the upper 20 and
lower 22
housing sections.
[0032] The valve 14 includes a valve sleeve 60 (Fig. 2) that is coaxial with
the
longitudinal axis 26 and is constructed to move longitudinally within an
annular pocket
80 (see Fig. 3) that is formed in the upper 20 and lower 22 housing sections
of the valve
14. The central passageway of the valve sleeve 60 forms part of the central
passageway
24 of the valve 14. Upper 62 and lower 64 0-rings circumscribe the outer
surface of the
sleeve 60 and form corresponding annular seals between the outer surface of
the sleeve
60 and the inner surface of the housing section 20 for purposes of sealing off
radial
openings (not shown in Fig. 2) in the upper housing section 20 during the
closed state
(depicted in Figs. 2 and 3) of the valve 14. As further described below, when
the sleeve
60 moves in a downward direction to open the valve 14, openings in the upper
housing
section 20 are exposed to place the valve 14 in an open state, a state in
which fluid
communication occurs between the central passageway 24 of the valve 14 and the
region
that surrounds the valve 14.
[0033] At its lower end, the valve sleeve 60 is connected to the upper end of
the
collet sleeve 30, a sleeve whose state of radial expansion/contraction
controls when the
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valve 14 is in the ball catching state. The collet sleeve 30 is generally
coaxial with the
longitudinal axis 26. In some embodiments of the invention, the collet sleeve
30 includes
a lower end 32 in which longitudinal slots 34 are formed, and these slots 34
may be
regularly spaced about the longitudinal axis 26 of the collet sleeve 30.
[0034] In its expanded state (depicted in Fig. 2), the lower end 32 of the
collet
sleeve 30 is flared radially outwardly for purposes of creating the maximum
diameter
through the interior of the collet sleeve 30. Thus, as depicted in Fig. 2, in
this state of the
collet sleeve 30, an opening 38 in the lower end 32 of the sleeve 30 has its
maximum
inner diameter, thereby leaving the central passageway 24 unobstructed.
[0035] For purposes of radially compressing the lower end 32 of the collet
sleeve
30 to place the valve 14 in its ball catching state, the valve 14 includes a
mandre140. The
mandrel 40 is designed to slide in a downward longitudinal direction (from the
position
depicted in Fig. 2) for purposes of sliding a sleeve 48 over the lower end 32
to radially
compress the lower end 32. The mandrel 40 is depicted in Fig. 2 in a position
to allow
full radial expansion of the lower end 32 of the collet sleeve 30, and thus,
in this position,
the mandrel 40 does not configure the collet sleeve 30 to catch a ball.
[0036] For purposes of actuating the mandrel 40 to move the mandre140 in a
downward direction, the mandrel 40 includes a piston head 43 that has an upper
surface
44. The upper surface 44, in turn, is in communication with a fluid passageway
42 that
may be formed in, for example, the upper housing section 20. The upper surface
44 of
the piston head 43 is exposed to an upper chamber 90 (having its minimum
volume in
Fig. 2) of the valve 14 for the purpose of creating a downward force on the
mandre140 to
compress the lower end 32 of the collet sleeve 30.
[0037] As depicted in Fig. 2, an 0-ring 47 forms a seal between the inner
surface
of the piston head 43 and the outer surface of the collet sleeve 30; and a
lower 0-ring 72
is located on the outside of the mandre140 for purposes of forming a seal
between the
exterior surface of the mandrel 40 and the interior surface of the upper
housing section
20. Due to these seals, the upper chamber 90 is sealed off from a lower
chamber 75, a
chamber that is below a lower surface 73 of the piston head 43. As an example,
in some
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embodiments of the invention, the lower chamber 75 has gas such as air at
atmospheric
pressure or other low pressure or at a vacuum.
[0038] The lower end of the mandrel 40 is connected to the sleeve 48 that has
an
inner diameter that is sized to approximately match the outer diameter of the
section of
the collet sleeve 30 located above the flared lower end 32. Thus, when the
pressure that
is exerted on the upper surface 47 of the piston head 43 creates a force that
exceeds the
combined upward force exerted from the chamber 75 to the lower surface 73 and
the
reaction force that is exerted due to the compression of the lower end 32, the
sleeve 48
restricts the inner diameter of the lower end 32 of the collet sleeve 30 to
place the valve
14 in its ball catching state.
[0039] Fig. 4 depicts the upper section 14A of the valve 14 when the valve 14
is
in the ball catching state, a state in which the mandre140 is at its lowest
point of travel.
In this state, the valve sleeve 60 remains in its uppermost point of travel to
keep the valve
14 closed. As shown, in this position, the outer diameter of the lower end 32
of the collet
sleeve 40 is confmed by the inner diameter of the sleeve 48, and an interior
annular seat
94 is formed inside the collet sleeve 30. The seat 94, in turn, presents a
restricted inner
diameter for catching a ball.
[0040] The capture of the ball on the seat 94 substantially restricts, if not
seals
off, the central passageway of the valve 14 above the ball from the central
passageway of
the valve 14 below the ball. Due to this restriction of flow, pressure may be
applied from
the surface of the well for purposes of exerting a downward force on the
collet sleeve 30.
Because the upper end of the collet sleeve 30 is connected to the lower end of
the valve
sleeve 60, when pressure is applied to the lodged ball and collet sleeve 30, a
corresponding downward force is generated on the valve sleeve 60. The sleeve
60 may
be initially retained in the upward position that is depicted in Figs. 2 and 4
by such
mechanism(s) (not depicted in the figures) as one or more detent(s), one or
more shear
pins, trapped low pressure, or vacuum chamber(s). However, when a sufficient
downward force is applied to the valve sleeve 60, this retention mechanism
gives way to
permit downward movement of the valve sleeve 60.
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[0041 ] Thus, to open the valve 14, a ball is dropped from the surface of the
well,
and then a sufficient pressure is applied (aided by the restriction presented
by the lodged
ball) to cause the valve sleeve 60 to shift from its uppermost position to its
lowest
position, a position that is depicted in Figs. 5 and 6. More particularly,
Figs. 5 and 6
depict the valve 14 in its open state. As shown in Fig 5, in the open state,
one or more
radial ports 100 formed in the upper housing section 20 are exposed to the
central
passageway 24 of the valve 14. Thus, in the open state, fluid, such as
fracturing fluid (for
example), may be communicated from the central passageway 24 of the string
(see Fig.
1) to the annular region that surrounds the valve 14. It is noted that when
the valve 14 is
closed, the radial openings 1:00 are sealed off between the upper 62 and lower
64 0-rings.
[0042] Referring to Fig. 6, due to the pressure that is exerted on the valve
sleeve
60, the assembly that is formed from the valve sleeve 60, collet sleeve 30,
mandre140
and sleeve 48 travels downwardly until the bottom surface of the collet sleeve
30 and the
bottom surface of the sleeve 48 reside on an annular shoulder that is formed
at the bottom
of the annular pocket 80. Fig. 6 also depicts a sphere, or ball 150, that
rests on the seat
94 and has caused the valve 14 to transition to its open state.
[0043] Referring back to Fig. 5, in the open state of the valve 14, the
passageway
70 is in fluid communication with the central passageway 24. This is in
contrast to the
closed state of the valve in which the 0-ring 68 forms a seal between the
central
passageway 24 and the passageway 70, as depicted in Figs. 2 and 4. Therefore,
in the
valve's open state, fluid pressure may be communicated to the passageway 70
(see Fig. 5)
for purposes of transitioning another valve 14 of the string 12 (see Fig. 1)
to its ball
catching state.
[0044] As a more specific example, in some embodiments of the invention, the
passageway 70 may be in fluid communication with the passageway 42 of another
valve
14 (the immediately adjacent valve 14 above, for example). Therefore, in
response to the
valve sleeve 60 moving to its lower position, a downward force is applied
(through the
communication of pressure through the passageways 70 and 42) to the mandrel 40
of
another valve 14 of the string 12. As a more specific example, in some
embodiments of
the invention, the passageway 70 of each valve 14 may be in fluid
communication with
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the passageway 42 of the immediate upper adjacent valve in the string 12.
Thus,
referring to Fig. 1, for example, the passageway 70 of the valve 143 is
connected to the
passageway 42 of the valve 142, and the passageway 70 of the valve 142 is
connected to
the passageway 42 of the valve 141. It is noted that the valve 141 in the
exemplary
embodiment that is depicted in Fig. 1, is the uppermost valve 14 in the string
12. Thus, in
some embodiments of the invention, the passageway 70 of the valve l41 may be
sealed
off or non-existent.
[0045] For the lowermost valve 14N, the passageway 42 is not connected to the
passageway of a lower valve. Thus, in some embodiments of the invention, the
lowermost valve 14N is placed in its ball catching state using a mechanism
that is
different from that described above. For example, in some embodiments of the
invention,
the valve 14N may be placed in its ball catching state in response to a fluid
stimulus that
is communicated downhole through the central passageway of the string 12.
Thus, the
lowermost valve 14N may include a mechanism such as a rupture disc that
responds to a
remotely-communicated stimulus to permit a downward force to be applied to the
mandrel 40.
[0046] As another example, in some embodiments of the invention, the above-
described actuator may move the mandrel 40 in a downward direction in response
to a
downhole stimulus that is communicated via a slickline or a wireline that are
run
downhole through the central passageway of the string 12. As yet another
example, the
stimulus may be encoded in an acoustic wave that is communicated through the
string 12.
[0047] As another example of a technique to place the valve 14N in its ball
catching state, in some embodiments of the invention, the mandrel 40 may have
a profile
on its inner surface for purposes of engaging a shifting tool that is lowered
downhole
through the central passageway of the string 12 for purposes of moving the
mandre140 in
a downward direction to place the valve 14N in its ball catching state. As yet
another
example of yet another variation, in some embodiments of the invention, the
valve 14N
may be run downhole with a collet sleeve (replacing the collet sleeve 30) that
is already
configured to present a ball catching seat. Thus, many variations are possible
and are
within the scope of the claimed invention.
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[0048] Because the valve 14N is the last the valve in the string 12, other
challenges may arise in operating the valve 14N. For example, below the lowest
layer
15N, there is likely to be a closed chamber in the well. If a ball were
dropped on the seat
94 (see Fig. 14, for example), the valve sleeve 60 of the valve 14N may not
shift
downwardly because any movement downward may increase the pressure below the
ball.
Thus, in some embodiments of the invention, the string 12 includes an
atmospheric
chamber 17 (see Fig. 1) that is located below the valve 14N. As an example,
the chamber
17 may be formed in a side pocket in a wall of the string 12. To initiate the
valve 14N for
operation, a perforating gun may be lowered downhole through the central
passageway of
the string 12 to the position where the atmospheric chamber 17 is located. At
least one
perforation formed from the firing of the perforating gun may then penetrate
the
atmospheric chamber 17 to create the lower pressure needed to shift the valve
sleeve 60
in a downward direction to open the valve 14N.
[0049] In some embodiments of the invention, when the atmospheric chamber 17
is penetrated, a pressure signal is communicated uphole, and this pressure
signal may be
used to signal the valve 14N to shift the operator mandrel 40 in a downward
direction to
place the valve 14N in the ball catching state. More specifically, in some
embodiments of
the invention, the valve 14N may include a pressure sensor that detects the
pressure signal
so that an actuator of the valve 14N may respond to the pressure signal to
move the
mandre140 in the downward direction to compress the lower end 32 of the collet
sleeve
30.
[0050] Alternatively, in some embodiments of the invention, the collet sleeve
30
of the valve 14N may be pre-configured so that the seat 94 is already in its
restricted
position when the string 12 is run into the well. A perforating gun may then
be lowered
through the central passageway of the string 12 for purposes of piercing the
atmospheric
chamber 17 to allow downward future movement of the sleeve valve 60, as
described
above.
[0051] Referring to Fig. 7, in some embodiments of the invention, a technique
200 may be used for purposes of fracturing multiple layers of a subterranean
well. The
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technique 200 is used in conjunction with a string that includes valves
similar to the ones
that are described above, such as the string 12 that contains the valves 14
(see Fig. 1).
[0052] Pursuant to the technique 200, the lowest valve of the string is placed
in its
ball catching state, as depicted in block 202. Next, the technique 200 begins
an iteration
in which the valves are opened pursuant to a sequence (a bottom-to-top
sequence, for
example). In each iteration, the technique 200 includes dropping the next ball
into the
string 12, as depicted in block 204. Next, pressure is applied (block 206) to
the ball to
cause the valve to open and place another valve (if another valve is to
opened) in the ball
catching state. Subsequently, the technique 200 includes performing (block
208)
fracturing in the layer that is associated with the opened valve. If another
layer is to be
fractured (diamond 210), then the technique 200 includes returning to block
204 to
perform another iteration.
[0053] As a more specific example, in some embodiments of the invention, the
lowest valve 15N (see Fig. 1) may be open via a rupture disc and an
atmospheric
chamber. More specifically, the string 12 is pressured up, the rupture disc
breaks and
then fluid pushes on side of a piston. The other side of this piston is in
contact with an
atmospheric chamber or a vacuum chamber.
[0054] Contrary to conventional strings that use ball catching valves, the
valves
14 are not closed once opened, in some embodiments of the invention.
Furthermore, in
some embodiments of the invention, each valve 14 remains in its ball catching
state once
placed in this state. Because the valves 14 are designed to trap a ball of the
same size, the
cross-sectional flow area through the central passageway of the string is not
significantly
impeded for subsequent fracturing or production operations.
[0055] It is noted that for an arbitrary valve 14 in the string 12, once the
valve 14
is placed in its ball catching state, the restricted diameter formed from the
lower end of
the collet sleeve 30 prevents a ball from below the collet sleeve 30 below
from flowing
upstream. Therefore, during flowback, each ball may be prevented from flowing
past the
lower end 32 of the collet sleeve 30 of the valve 14 above.
[0056] However, in accordance with some embodiments of the invention, each
ball may be formed from a material, such as a dissolvable or frangible
material, that
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allows the ball to disintegrate. Thus, although a
particular ball may flow upstream during flowback and
contact the bottom end of the collet sleeve 30 above, the
ball is eventually eroded or at least sufficiently dissolved
to flow upstream through the valve to open up communication
through the string 12.
[0057] In some embodiments of the invention, captured
ball used to actuate a lower valve 14 may push up on the
collet sleeve 30 of a higher valve in the string 12 until
the collet sleeve 30 moves into an area (a recessed region
formed in the lower housing 22, for example) which has a
pocket in the inner diameter to allow the collet sleeve 30
to reopen. Thus, when the collet sleeve 30 reopens, the
inner diameter is no longer small enough to restrict the
ball so that the ball can flow uphole. Other variations are
possible and are within the scope of the appended claims.
[0058] Referring to Fig. 8, in accordance with some
embodiments of the invention, a bottom surface 251 of the
lower end 32 of the collet sleeve 30 is designed to be
irregular to prevent a ball that is located below the collet
sleeve 30 (and has not dissolved or eroded enough to pass
through) from forming a seal that blocks off fluid
communication. Thus, as depicted in Fig. 8, in some
embodiments of the invention, the surface 251 may have one
or more irregularities, such as a depression 251 that
permits the surface 32 from becoming an effective valve
seat. Other types of irregularities may be introduced to
the surface 251, such as raised portions, generally rough
surfaces, etc., depending the particular embodiment of the
invention.
[0059] Other embodiments are within the scope of the
appended claims. For example, referring to Fig. 9, in some
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embodiments of the invention, in a valve 290 (that replaces
the valve 14) the collet sleeve 30 may be replaced by a C-
ring 300. The valve 290 has the same generally design of
the valve 14, except for the C-ring 300 and the following
differences. The C-ring 300, in some embodiments of the
invention, includes a single open slot 309 when the valve is
not in the ball catching state. Thus, as depicted in
Fig. 9, in this state, a mandrel 302 is located above the C-
ring 300 so that the open ends 307 of the C-ring 300 do not
compress to close the slot 309. As depicted in Fig. 9, an
end 304 of the mandrel 302 may be inclined, or beveled, in
some embodiments of the invention so that when the
mandrel 302 slides downhole, as depicted in Fig. 10, the
ends
13a
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307 meet to close the slot 309 (Fig. 9) and thus restrict the inner diameter
through the C-
ring 300. In the state that is depicted in Fig. 10, the valve is in a ball
catching state, as the
inner diameter has been restricted for purposes of catching a free-falling or
pumped down
object.
[0060] The C-ring design may be advantageous, in some embodiments of the
invention, in that the C-ring 300 includes a single slot 309, as compared to
the multiple
slots 34 (see Fig. 2, for example) that are present in the collet sleeve 30.
Therefore, the
C-ring design may be advantageous in that sealing is easier because less
leakage occurs
when the C-ring ring 300 contracts.
[0061] Referring to back to Fig. 1, in some embodiments of the invention, the
string 12 may be deployed in a wellbore (e.g., an open or uncased hole) as a
temporary
completion. In such embodiments, sealing mechanisms may be employed between
each
valve and within the annulus defined by the tubular string and the wellbore to
isolate the
formation zones being treated with a treatment fluid. However, in other
embodiments of
the invention, the string 12 may be cemented in place as a permanent
completion. In
such embodiments, the cement serves to isolate each formation zone.
[0062] The cementing of the string 12 may potentially block valve openings, if
not for certain features of the valve 14. For example, referring back to Fig.
5, in some
embodiments of the invention, the valve 14 may include lobes 101 that are
spaced around
the longitudinal axis 26. Each lobe 101 extends radially outwardly from a main
cylindrical wall 103 of the upper housing 20, and each radial port 100 extends
through
one of the lobes 101. The lobes 101 restrict the space otherwise present
between the
valve 14 and the wellbore to limit the amount of cement that may potentially
block fluid
communication between the central passageway 24 and the region outside of the
valve
14, as described in co-pending U.S. Patent Application Serial No. 10/905,073
entitled,
"SYSTEM FOR COMPLET'ING MUTLIPLE WELL INTERVALS," filed on December
14, 2004.
[0063] In accordance with some embodiments of the invention, each radial port
100 is formed from an elongated slot whose length is approximately equal to at
least five
times its width. It has been discovered that such a slot geometry when used in
a
14
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fracturing operating allows radial deflection when pressuring up, which
increases stress
in the rock and thus, reduces the fracturing initiation pressure.
[0064] Depending on the particular embodiment of the invention, the valve may
contain, as examples, three (spaced apart by 120 around the longitudinal axis
26, for
example) or six (spaced apart by 60 around the longitudinal axis 26, for
example) lobes
101. In some embodiments of the invention, the valve 14 does not contain the
lobes 101.
Instead, the upper housing section 20 approximates a circular cylinder, with
the outer
diameter of the cylinder being sized to closely match the inner diameter of
the wellbore.
[0065] Other variations are possible in accordance with the various
embodiments
of the invention. For example, depending on the particular embodiment of the
invention,
each radial port 100 may have a length that is at least approximately equal to
ten or (in
other embodiments) is approximately equal to twenty times its length.
[0066] The radial slots 100 are depicted in Fig. 5 as being located at
generally the
same longitudinal position. However, in other embodiments of the invention, a
valve
(Fig. 11) may include a valve housing 400 (replacing the upper valve housing
20) that
includes radial slots 420 that extending along a helical, or spiral path 422,
about the
longitudinal axis 26. As shown in Fig. 11, the valve housing 400 does not
contain the
radially-extending lobes. Thus, many variations are possible and are within
the scope of
the appended claims.
[0067] Although directional and orientational terms (such as "upward,"
"lower,"
etc.) are used herein to describe the string, the valve, their components and
their
operations, it is understood that the specific orientations and directions
that are described
herein are not needed to practice the invention. For example, in some
embodiments of
the invention, the valve sleeve may move in an upward direction to open. As
another
example, in some embodiments of the invention, the string may be located in a
lateral
wellbore. Thus, many variations are possible and are within the scope of the
appended
claims.
[0068] While the present invention has been described with respect to a
limited
number of embodiments, those skilled in the art, having the benefit of this
disclosure, will
appreciate numerous modifications and variations therefrom. It is intended
that the
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appended claims cover all such modifications and variations as fall within the
true spirit
and scope of this present invention.
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