U.S. patent application number 11/837115 was filed with the patent office on 2007-11-29 for technique and apparatus for completing multiple zones.
This patent application is currently assigned to SCHLUMBERGER TECHNOLOGY CORPORATION. Invention is credited to Liana M. Mitrea, Gary L. Rytlewski, Ashish Sharma.
Application Number | 20070272413 11/837115 |
Document ID | / |
Family ID | 40765641 |
Filed Date | 2007-11-29 |
United States Patent
Application |
20070272413 |
Kind Code |
A1 |
Rytlewski; Gary L. ; et
al. |
November 29, 2007 |
TECHNIQUE AND APPARATUS FOR COMPLETING MULTIPLE ZONES
Abstract
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 examples) of
substantially the same size, which are communicated downhole
through the passageway.
Inventors: |
Rytlewski; Gary L.; (League
City, TX) ; Sharma; Ashish; (Sugar Land, TX) ;
Mitrea; Liana M.; (Houston, TX) |
Correspondence
Address: |
SCHLUMBERGER RESERVOIR COMPLETIONS
14910 AIRLINE ROAD
ROSHARON
TX
77583
US
|
Assignee: |
SCHLUMBERGER TECHNOLOGY
CORPORATION
300 Schlumberger Drive
Sugar Land
TX
77478
|
Family ID: |
40765641 |
Appl. No.: |
11/837115 |
Filed: |
August 10, 2007 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
11081005 |
Mar 15, 2005 |
|
|
|
11837115 |
Aug 10, 2007 |
|
|
|
10905073 |
Dec 14, 2004 |
|
|
|
11081005 |
Mar 15, 2005 |
|
|
|
Current U.S.
Class: |
166/318 |
Current CPC
Class: |
E21B 43/14 20130101;
E21B 43/26 20130101; E21B 34/14 20130101 |
Class at
Publication: |
166/318 |
International
Class: |
E21B 34/14 20060101
E21B034/14 |
Claims
1. 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 a longitudinal length at least five times greater than a
width of the slot.
2. The system of claim 1, wherein the valve comprises a sleeve
adapted to move to selectively block the openings to control the
fluid communication between the passageway and the region.
3. The system of claim 1, wherein the longitudinal length is at
least ten times greater than the width.
4. The system of claim 1, wherein the longitudinal length is at
least twenty times greater than the width.
5. The system of claim 1, wherein the openings extend in a spiral
pattern about the longitudinal axis of the valve.
Description
[0001] This application is a divisional of U.S. patent application
Ser. No. 11/081,005 entitled, "TECHNIQUE AND APPARATUS FOR
COMPLETING MULTIPLE ZONES," filed on Mar. 15, 2005 which is a
continuation-in-part of U.S. patent application Ser. No. 10/905,073
entitled, "SYSTEM FOR COMPLETING MUTLIPLE WELL INTERVALS," filed on
Dec. 14, 2004, which is hereby incorporated by reference in its
entirety.
BACKGROUND
[0002] The present invention generally relates to a technique and
apparatus to complete multiple zones.
[0003] 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 time by
directing fracturing fluid to the layer being fractured and
isolating the other layers.
[0004] 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.
[0005] 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 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.
[0006] 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.
[0007] 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.
[0008] 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.
[0009] 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.
[0010] 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
[0011] 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 examples) of substantially the same size,
which are communicated downhole through the passageway.
[0012] 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.
[0013] 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.
[0014] Advantages and other features of the invention will become
apparent from the following description, drawing and claims.
BRIEF DESCRIPTION OF THE DRAWING
[0015] FIG. 1 depicts a fracturing system according to an
embodiment of the invention.
[0016] 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.
[0017] 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.
[0018] FIGS. 5 and 6 depict the valve in its open state according
to an embodiment of the invention.
[0019] FIG. 7 is a flow diagram depicting a technique to fracture
layers in a multiple layer well according to an embodiment of the
invention.
[0020] 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.
[0021] 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.
[0022] FIG. 11 is a perspective view of a valve housing according
to another embodiment of the invention.
DETAILED DESCRIPTION
[0023] 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 15.sub.1, 15.sub.2, 15.sub.3 . . . 15.sub.N-1
and 15.sub.N, depicted as examples) of the well. As depicted in
FIG. 1, the string 12 includes valves 14 (valves 14.sub.1,
14.sub.2, 14.sub.3 . . . 14.sub.N-1 and 14.sub.N, depicted as
examples), each of which is associated with a particular layer 15.
For example, the valve 14.sub.3 is associated with the layer
15.sub.3. 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.
[0024] 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.
[0025] 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 14.sub.N, proceeds
uphole to the next immediately adjacent valve 14, then to the next
immediately adjacent valve 14, etc. Thus, the valve 14.sub.N is
opened before the valve 14.sub.N-1, the valve 14.sub.3, is opened
before the valve 14.sub.2, etc.
[0026] 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.
[0027] 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.
[0028] 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.
[0029] 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.
[0030] 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 14.sub.N 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 14.sub.N opens to allow a fracturing
operation to be performed on the associated layer 15.sub.N. The
opening of the valve 14.sub.N, in turn, places the next valve
14.sub.N-1 in the sequence in the ball catching state. Once the
fracturing operation on the layer 15.sub.N is complete, another
ball is dropped into the central passageway of the string 12 for
purposes of opening the valve 14.sub.N-1 so that the layer
15.sub.N-1 can be fractured. Thus, this sequence continues until
the last valve 14.sub.1 is opened, and the associated layer
15.sub.1 is fractured.
[0031] 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 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.
[0032] 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.
[0033] 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.
[0034] 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 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.
[0035] 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.
[0036] 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 mandrel 40. 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.
[0037] For purposes of actuating the mandrel 40 to move the mandrel
40 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 mandrel 40 to compress the lower
end 32 of the collet sleeve 30.
[0038] 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 mandrel 40 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
embodiments of the invention, the lower chamber 75 has gas such as
air at atmospheric pressure or other low pressure or at a
vacuum.
[0039] 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.
[0040] 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
mandrel 40 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 confined 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.
[0041] 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.
[0042] 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 100 are scaled off between the
upper 62 and lower 64 0-rings.
[0043] 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, mandrel 40 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.
[0044] 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.
[0045] 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
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 14.sub.3 is connected to the passageway 42 of the
valve 14.sub.2, and the passageway 70 of the valve 14.sub.2 is
connected to the passageway 42 of the valve 14.sub.1. It is noted
that the valve 14.sub.1 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 14.sub.1 may be sealed off or non-existent.
[0046] For the lowermost valve 14.sub.N, the passageway 42 is not
connected to the passageway of a lower valve. Thus, in some
embodiments of the invention, the lowermost valve 14.sub.N 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 14.sub.N 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 14.sub.N 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.
[0047] 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.
[0048] As another example of a technique to place the valve
14.sub.N 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 mandrel 40 in a downward direction to place the valve
14.sub.N in its ball catching state. As yet another example of yet
another variation, in some embodiments of the invention, the valve
14.sub.N 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.
[0049] Because the valve 14.sub.N is the last the valve in the
string 12, other challenges may arise in operating the valve
14.sub.N. For example, below the lowest layer 15.sub.N, 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 14.sub.N 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 14.sub.N.
As an example, the chamber 17 may be formed in a side pocket in a
wall of the string 12. To initiate the valve 14.sub.N 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
14.sub.N.
[0050] 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 14.sub.N
to shift the operator mandrel 40 in a downward direction to place
the valve 14.sub.N in the ball catching state. More specifically,
in some embodiments of the invention, the valve 14.sub.N may
include a pressure sensor that detects the pressure signal so that
an actuator of the valve 14.sub.N may respond to the pressure
signal to move the mandrel 40 in the downward direction to compress
the lower end 32 of the collet sleeve 30.
[0051] Alternatively, in some embodiments of the invention, the
collet sleeve 30 of the valve 14.sub.N 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.
[0052] 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 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).
[0053] 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.
[0054] As a more specific example, in some embodiments of the
invention, the lowest valve 15.sub.N (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.
[0055] 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.
[0056] 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.
[0057] 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 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.
[0058] 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.
[0059] Referring to FIG. 8, in accordance with some embodiments of
the invention, a bottom surface 252 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 252 may have one or more
irregularities, such as a depression 252 that permits the surface
32 from becoming an effective valve seat. Other types of
irregularities may be introduced to the surface 252, such as raised
portions, generally rough surfaces, etc., depending the particular
embodiment of the invention.
[0060] Other embodiments are within the scope of the appended
claims. For example, referring to FIG. 9, in some 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 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.
[0061] 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.
[0062] 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.
[0063] 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 Ser. No. 10/905,073 entitled, "SYSTEM FOR
COMPLETING MUTLIPLE WELL INTERVALS," filed on Dec. 14, 2004.
[0064] 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 fracturing
operating allows radial deflection when pressuring up, which
increases stress in the rock and thus, reduces the fracturing
initiation pressure.
[0065] Depending on the particular embodiment of the invention, the
valve may contain, as examples, three (spaced apart by 120.degree.
around the longitudinal axis 26, for example) or six (spaced apart
by 60.degree. 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.
[0066] 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.
[0067] 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.
[0068] 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.
[0069] 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
appended claims cover all such modifications and variations as fall
within the true spirit and scope of this present invention.
* * * * *