Note: Descriptions are shown in the official language in which they were submitted.
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STAGE TOOL, WELLBORE INSTALLATION AND METHOD
FIELD
The invention relates to wellbore operations and, in particular, a stage tool,
a wellbore
installation and a method for wellbore cementing.
BACKGROUND
In wellbore operations, cementing may be used to control migration of fluids
outside a
liner installed in the wellbore. For example, cement may be installed in the
annulus
between the wellbore liner and the formation wall to deter migration of the
fluids axially
along the annulus.
Often cement is introduced by flowing cement down through the wellbore liner
to its
distal end and then forcing the cement around the bottom and up into the
annulus where it
is allowed to set.
Occasionally, it is desirable to introduce cement into the annulus without
pumping it
around the bottom end of the liner. A stage tool may be used for this purpose.
A stage
tool, is a tubular that can be installed along the length of the liner and
includes an inner
bore defined by an inner tubular surface, an outer tubular surface, a port
between the
inner tubular surface and the outer tubular surface through which fluid can be
passed to
cement the annulus along a length of the liner and a closure for the port
which is
openable and closeable to control the flow of cement through the port.
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Often the closure is opened by elevated fluid pressure. However, some
formations
cannot accommodate high pressures, as they damage the formation as by
fracturing.
SUMMARY
In accordance with another broad aspect of the present invention, there is
provided a
method for stage cementing a wellbore, the method comprising: increasing
pressure
within a tubing string within the wellbore to conduct an operation in the
tubing string, the
tubing string including a stage tool with an inner diameter in pressure
communication
with the tubing string; reducing pressure in the stage tool inner diameter;
opening the
stage tool when the pressure in the stage tool inner diameter is approximately
equal to
annular pressure in an annulus about the stage tool; and pumping cement
through the
stage tool into the annulus.
In accordance with another broad aspect of the present invention, there is
provided a
wellbore installation comprising: a bore hole in a formation; a tubing string
in the bore
hole, the tubing string including a lower end, an upper end and a tubular wall
between the
lower and the upper end, with an inner bore defined within the tubular wall
and an
annular space defined between the tubing string and a wall of the bore hole;
and a stage
tool installed in the tubing string, the stage tool having a cementing port
and the
cementing port configured to open when the pressure in the inner bore is
increased and
then decreased until the pressure in the inner bore is substantially equal
with the pressure
of the annular space.
It is to be understood that other aspects of the present invention will become
readily
apparent to those skilled in the art from the following detailed description,
wherein
various embodiments of the invention are shown and described by way of
illustration. As
will be realized, the invention is capable for other and different embodiments
and its
several details are capable of modification in various other respects, all
without departing
from the spirit and scope of the present invention. Accordingly the drawings
and detailed
description are to be regarded as illustrative in nature and not as
restrictive.
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BRIEF DESCRIPTION OF THE DRAWINGS
Several aspects of the present invention are illustrated by way of example,
and not by
way of limitation, in detail in the drawings.
The drawings include:
Figures 1A, 1B and 1C are sequential schematic sectional views through a
wellbore with
a wellbore installation therein, where Figure lA shows a stage tool being
activated,
Figure 1B shows a stage tool in a delayed mode where the stage tool ports have
not yet
been opened, but pressure is being equalized between the string and the
annulus, and
Figure 1C shows cement being pumped through the stage tool into the annulus.
Figures 2A, 2B and 2C are axial sectional views of a sleeve valve for a stage
tool in first,
second and final positions, respectively, according to one aspect of the
present invention.
Figures 3A, 3B and 3C are a series of sectional views along one embodiment of
a stage
tool.
Figures 3D and 3E are enlarged views of the stage tool of Figure 3A.
Figures 3F and 3G are enlarged views of another activation mechanism for a
stage tool.
DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS
The description that follows and the embodiments described therein are
provided by way
of illustration of an example, or examples, of particular embodiments of the
principles of
various aspects of the present invention. These examples are provided for the
purposes of
explanation, and not of limitation, of those principles and of the invention
in its various
aspects. In the description, similar parts are marked throughout the
specification and the
drawings with the same respective reference numerals. The drawings are not
necessarily
to scale and in some instances proportions may have been exaggerated in order
more
clearly to depict certain features.
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A cementing stage tool has been invented that opens when tubing pressure is
approximately the same as annular pressure. Thus, the stage tool has a port
that opens
only when a pressure differential is dissipated between the stage tool inner
diameter and
its outer surface, which is open to the annulus about the tool and thereby to
the formation.
Because substantially no opening or cementing pressure surge is applied to the
formation,
the stage tool is particularly useful for cementing in weak or unstable
formations. This is
primarily directed, at the current time, for shallow wells, and in particular
for thermal
applications such as those in oil sands formations such as Canadian oil sands
formations,
which are generally unconsolidated produced through in-situ, thermal, such as
steam-
assisted, operations.
There may be a requirement for stage cementing and for converting these
thermal wells
to a monobore. In a monobore scenario, the diameter of the production conduit
is
substantially uniform from the reservoir to surface. The simplest form of
monobore is a
string of tubing cemented in place that eliminates the need for one of the
casing strings or
liners when compared with a conventional wellbore design. In the formation of
the
monobore, a surface borehole is drilled and set with surface casing. Then a
wellbore
extension, such as a lateral, is drilled from the surface borehole in one
drilling procedure,
a monobore system is run and then a stage cementing operation is conducted.
The
monobore is run through the heel, where the borehole orientation transitions
from the
surface substantially vertical hole to the lateral, substantially horizontal
hole.
In such a procedure, stage cementing according to the invention can be carried
out
without providing a surge on the formation to avoid formation damage such as
break
down fracturing. Thus, although tubing pressure may be elevated significantly
over
annular pressure during initial operations: to pressure test and/or to actuate
pressure
responsive mechanisms, such as, for example, to set packers, to actuate stage
tools or
other tools, etc., that elevated pressure is not communicated to the annulus.
In such an
embodiment, a stage tool may be employed that only opens to permit
communication
from the tubing string inner diameter to the folination once tubing pressure
is reduced to
be less than that which would damage the formation, such as a pressure that is
about the
same as or less than the annular pressure.
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In one embodiment the stage tool may include a delay mechanism configured to
permit
opening of the stage tool ports only after a selected period of time lapses.
The stage tool
ports open only that selected period of time after an activation of the delay
mechanism.
The delay mechanism therefore delays opening the stage tool ports until a
selected
amount of time has lapsed after activation of the port opening process.
Activating the
tool perntits the stage tool ports to be opened but does not open the ports,
the opening of
the ports being delayed by the delay mechanism.
The stage tool may include a signal receiver in addition to the delay
mechanism. The
signal receiver is configured to receive an activation signal indicating that
it is an
appropriate time to start the port opening process and the delay mechanism is
configured
to delay opening the stage tool ports until a selected amount of time after
activation. The
amount of time may be selected, for example, to be a time sufficient for all
pressured up
operations to be accomplished. Thus, while pressured up operations are
conducted, the
stage tool remains closed, but thereafter the stage tool ports are opened.
The delay mechanism can be a timer, a resistive force, a pressure sensor, etc.
The stage tool ports can open electrically, mechanically (such as by a driving
spring) or
hydraulically (such as by using a pressure chamber such as an atmospheric
chamber).
The delay mechanism can be activated at surface before being the tubing string
in which
the stage tool is installed is run in into the well. The activated delay
mechanism, such as
for example, may include a timer that is started before installation of the
stage tool and
tubing string. The delay mechanism, for example the timer, then delays the
stage tool
port-opening for a period of time sufficient to run in the string and the
stage tool and to
conduct string setting operations. Alternately, the delay mechanism may be
activated
when the stage tool is already in place in the wellbore, for example, using a
signal
receiver for the delay mechanism.
A signal receiver may be configured to receive a mechanical, a sonic, an
electrical or a
hydraulic, etc. activation signal. The signal receiver can be configured to
accept a signal
from (i) a mechanical contact, such as from contact by a conveyed activating
tool such as
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a dart or ball, (ii) sonically, (iii) electrically or (iv) hydraulically. For
example, in a
hydraulic system, the signal may be communicated to the stage tool by
pressuring up the
tubing string inner diameter and thereby the inner diameter of the stage tool,
which
through a pressure differential between the inner diameter pressure and
another piston
face, such as that within a pressure chamber, differential piston faces or
that exposed to
annular pressure.
Regardless of the mode of activation, the stage tool is configured to only
open its ports
when tubing pressure within the stage tool is reduced over the pressured up
level of the
tubing string. The tubing pressure is reduced to be substantially pressure
balanced with
annular pressure. The reduction of tubing pressure may be actively by reverse
pumping
or bleeding off pressure at surface.
In a hydraulic system, for example shown in Figures 1 A to 1C, the activating
signal may
be communicated through the string 8 to the stage tool 10 by pressuring up the
tubing
string, which is increasing tubing pressure in the string to a pressure P1
that is greater
than annular pressure Pa (Figure 1A). Communicating the activating signal by
pressuring
up may involve pumping an activating tool through the string to the stage
tool.
Alternately, without a separate activating tool, pressuring up may
hydraulically activate
the stage tool to be ready to open. While the activating signal activates the
stage tool,
closure 10a remains over cementing ports 10b of the stage tool. After being
activated,
the opening of the stage tool ports 10b is delayed (Figure 1B) until the
tubing string and
the annulus are substantially pressure balanced, wherein tubing pressure is
reduced to P2
which is substantially the same as Pa. To achieve a substantial pressure
balance between
the inner bore and the annulus, the tubing pressure is reduced. For example,
the tubing
pressure may be released and time may be permitted to allow the tubing
pressure to
dissipate from P1 to P2.
When P2 is substantially equal to Pa, the stage tool ports 10b open and
cement, arrows C,
can be circulated from the inner bore of the stage tool, through ports 10b and
into the
annulus (Figure 1C). The stage tool may be positioned adjacent to the heel of
the well,
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uphole of a packer such that the cement is placed in the annulus and the
cement extends
from the stage tool, as introduced through the cementing ports, upwardly
toward surface.
Achieving a substantial pressure balance before allowing the stage tool ports
to open
avoids putting a surge on the formation. Considering the fragility of the
formation,
cement circulation may be gentle, for example at low pump pressures,
circulated from the
inner bore of the stage tool, through ports 10b and into the annulus (Figure
1C). The
cementing ports may be open just prior to cement flow therethrough. For
example, to
avoid the generation of a surge due to pressure differentials, the cementing
port may be
open for the cement to pass therethrough. As such, the use of operable check
valves at
the cementing ports during cementing may be avoided.
One embodiment of a useful stage tool is shown in Figures 2A to 2C, wherein
the
activating signal is hydraulic and acts against a piston face on the stage
tool and the delay
mechanism is a form of pressure sensor that only allows the stage tool ports
to be opened
when the pressure inside the stage tool is about equal with the pressure
outside the stage
tool. A stage tool 10 with a hydraulically actuable sleeve valve is shown.
Stage tool 10
may include a tubular segment 12, a sleeve 14 supported by the tubular segment
and a
driver, shown generally at reference number 16, to drive the sleeve to move.
Stage tool 10 is configured to have durability suitable for use in wellbore
tool
applications, such as wellbore stage cementing. Tubular segment 12 may be a
wellbore
tubular such as of pipe, liner casing, etc. and may be a portion of a tubing
string. Tubular
segment 12 may include a bore 12a in communication with the inner bore of a
tubing
string such that pressures may be controlled therein and fluids may be
communicated
from surface therethrough, such as for actuation of the tool and conveying
cement.
Tubular segment 12 may be formed in various ways to be incorporated in a
tubular string.
For example, the tubular segment may be formed integral or connected by
various means,
such as threading, welding etc., with another portion of the tubular string.
For example,
ends 12b, 12c of the tubular segment, shown here as blanks, may be formed for
engagement in sequence with adjacent tubulars in a string. For example, ends
12b, 12c
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may be formed as threaded pins or boxes to allow threaded engagement with
adjacent
tubulars.
Sleeve 14 may be installed to act as a piston in the tubular segment, in other
words to be
axially moveable relative to the tubular segment at least some movement of
which is
driven by fluid pressure. Sleeve 14 may be axially moveable through a
plurality of
positions. For example, as presently illustrated, sleeve 14 may be moveable
through a
first position (Figure 2A), a second position (Figure 2B) and a final or third
position
(Figure 2C). The installation site for the sleeve in the tubular segment is
formed to allow
for such movement.
Sleeve 14 may include a first piston face 18 in communication, for example
through ports
19, with the inner bore 12a of the tubular segment such that first piston face
18 is open to
tubing pressure. Sleeve
14 may further include a second piston face 20 in
communication with the outer surface 12d of the tubular segment. For example,
one or
more ports 22 may be formed from outer surface 12d of the tubular segment such
that
second piston face 20 is open to annulus, hydrostatic pressure about the
tubular segment.
First piston face 18 and second piston face 20 are positioned to act
oppositely on the
sleeve and act as the signal receiver to receive a hydraulic signal to
activate the stage tool
to open. Since the first piston face is open to tubing pressure and the second
piston face
is open to annulus pressure, a pressure differential can be set up between the
first piston
face and the second piston face to move the sleeve by offsetting or adjusting
one or the
other of the tubing pressure or annulus pressure. In particular, although
hydrostatic
pressure may generally be equalized between the tubing inner bore and the
annulus, by
increasing tubing pressure, as by increasing pressure in bore 12a from
surface, pressure
acting against first piston face 18 may be greater than the pressure acting
against second
piston face 20, which may cause sleeve 14 to move toward the low pressure
side, which
is the side open to face 20, into a selected second position (Figure 2B).
Seals 18a, such
as o-rings, may be provided to act against leakage of fluid from the bore to
the annulus
about the tubular segment such that fluid from inner bore 12a is communicated
only to
face 18 and not to face 20.
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One or more releasable setting devices 24 may be provided to releasably hold
the sleeve
in the first position. Releasable setting devices 24, such as one or more of a
shear pin (a
plurality of shear pins are shown), a collet, a c-ring, etc. provide that the
sleeve may be
held in place against inadvertent movement out of any selected position, but
may be
released to move only when it is desirable to do so. In the illustrated
embodiment,
releasable setting devices 24 may be installed to maintain the sleeve in its
first position
but can be released, as shown sheared in Figures 2B and 2C, by differential
pressure
between faces 18 and 20 to allow movement of the sleeve. Selection of a
releasable
setting device, such as shear pins to be overcome by a pressure differential
is well
understood in the art. In the present embodiment, the differential pressure
required to
shear out the sleeve is affected by the hydrostatic pressure and the rating
and number of
shear pins.
Driver 16 may be provided to move the sleeve into the final position. The
driver may be
selected to be unable to move the sleeve until releasable setting device 24 is
released.
Since driver 16 is unable to overcome the holding power of releasable setting
devices 24,
the driver can only move the sleeve once the releasable setting devices are
released.
Since driver 16 cannot overcome the holding pressure of releasable setting
devices 24 but
the differential pressure can overcome the holding force of devices 24, it
will be
appreciated then that driver 16 may apply a driving force less than the force
exerted by
the differential pressure such that driver 16 may also be unable to overcome
or act against
a differential pressure sufficient to overcome devices 24. Driver 16 may take
various
forms. For example, in one embodiment, driver 16 may include a spring and/or a
gas
pressure chamber such as an atmospheric chamber 26 to apply a push or pull
force to the
sleeve or to simply allow the sleeve to move in response to an applied force
such as an
inherent or applied pressure differential or gravity. In the illustrated
embodiment of
Figures 1, driver 16 employs hydrostatic pressure through piston face 20 that
acts against
trapped gas chamber 26 defined between tubular segment 12 and sleeve 14.
Chamber 26
is sealed by seals 18a, 28a, such as o-rings, such that any gas therein is
trapped. Chamber
26 includes gas trapped at atmospheric or some other low pressure. Generally,
chamber
26 includes air at surface atmospheric pressure, as may be present simply by
assembly of
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the parts at surface. In any event, generally the pressure in chamber 26 is
somewhat less
than the hydrostatic pressure downhole. As such, when sleeve 14 is free to
move, a
pressure imbalance occurs across the sleeve at piston face 20 causing the
sleeve to move
toward the low pressure side, as provided by chamber 26, if no greater forces
are acting
against such movement.
In the illustrated embodiment, sleeve 14 moves axially in a first direction
when moving
from the first position to the second position and reverses to move axially in
a direction
opposite to the first direction when it moves from the second position to the
third
position. In the illustrated embodiment, sleeve 14 passes through the first
position on its
way to the third position. The illustrated sleeve configuration and sequence
of movement
allows the sleeve to continue to hold pressure in the first position and the
second position.
When driven by tubing pressure to move from the first position into the second
position,
the sleeve moves from one overlapping, sealing position over port 28 into a
further
overlapping, port closed position and not towards opening of the port. As
such, as long
as tubing pressure is held or increased, the sleeve will remain in a port
closed position
and the tubing string in which the valve is positioned will be capable of
holding pressure.
The second position may be considered a closed but activated or passive
position,
wherein the sleeve has been acted upon, but the valve remains closed. In the
presently
illustrated embodiment, the pressure differential between faces 18 and 20
caused by
pressuring up in bore 12c does not move the sleeve into or even toward a port
open
position. Pressuring up the tubing string only releases the sleeve for later
opening. Only
when tubing pressure is dissipated to reduce or remove the pressure
differential, can
sleeve 14 move into the third, port open position.
While the above-described sleeve movement may provide certain benefits, of
course
other directions, traveling distances and sequences of movement may be
employed
depending on the configuration of the sleeve, piston chambers, releasable
setting devices,
driver, etc. In the illustrated embodiment, the first direction, when moving
from the first
position to the second position, may be towards surface and the reverse
direction may be
downhole.
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Sleeve 14 may be installed in various ways on or in the tubular segment and
may take
various forms, while being axially moveable along a length of the tubular
segment. For
example, as illustrated, sleeve 14 may be installed in an annular opening 27
defined
between an inner wall 29a and an outer wall 29b of the tubular segment. In the
illustrated
embodiment, piston face 18 is positioned at an end of the sleeve in annular
opening 27,
with pressure communication through ports 19 passing through inner wall 29a.
Also in
this illustrated embodiment, chamber 26 is defined between sleeve 14 and inner
wall 29a.
Also shown in this embodiment but again variable as desired, an opposite end
of sleeve
14 extends out from annular opening 27 to have a surface in direct
communication with
inner bore 12a. Sleeve 14 may include one or more stepped portions 31 to
adjust its inner
diameter and thickness. Stepped portions 31, if desired, may alternately be
selected to
provide for piston face sizing and force selection. In the illustrated
embodiment, for
example, stepped portion 31 provides another piston face on the sleeve in
communication
with inner bore 12a, and therefore tubing pressure, through ports 33. The
piston face of
portion 31 acts with face 20 to counteract forces generated at piston face 18.
In the
illustrated embodiment, ports 33 also act to avoid a pressure lock condition
at stepped
portion 31. The face area provided by stepped portion 31 may be considered
when
calculating the total piston face area of the sleeve and the overall pressure
effect thereon.
For example, faces 18, 20 and 31 must all be considered with respect to
pressure
differentials acting across the sleeve and the effect of applied or inherent
pressure
conditions, such as applied tubing pressure, hydrostatic pressure acting as
driver 16.
Faces 18, 20 and 31 may all be considered to obtain a sleeve across which
pressure
differentials can be readily achieved.
In operation, sleeve 14 may be axially moved relative to tubular segment 12
between the
three positions. For example, as shown in Figure 2A, the sleeve valve may
initially be in
the first position with releasable setting devices 24 holding the sleeve in
that position. To
move the sleeve to the second position shown in Figure 2B, pressure may be
increased in
bore 12a, which pressure is not communicated to the annulus, such that a
pressure
differential is created between face 18 and face 20 across the sleeve. This
tends to force
the sleeve toward the low pressure side, which is the side at face 20. Such
force releases
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devices 24, for example shears the shear pins, such that sleeve 14 can move
toward the
end defining face 20 until it arrives at the second position (Figure 2B).
Thereafter,
pressure in bore 12a can be allowed to relax such that the pressure
differential is reduced
or eliminated between faces 18 and 20. At this point, since the sleeve is free
from the
holding force of devices 24, once the pressure differential is sufficiently
reduced, the
force in driver 16 may be sufficient to move the sleeve into the third
position (Figure 2C).
In the illustrated embodiment, for example, the hydrostatic pressure may act
on face 20
and, relative to low pressure chamber 26, a pressure imbalance is established
that may
tend to drive sleeve 14 to the third, and in the illustrated embodiment of
Figure 2C, final
position.
As such, a pressure increase within the tubular segment causes a pressure
differential that
releases the sleeve and renders the sleeve into a condition such that it can
be acted upon
by a driving force to move the sleeve to a further position. Pressuring up is
only required
to release the sleeve and not to move the sleeve into a port open position. In
fact, since
any pressure differential where the tubing pressure is greater than the
annular pressure
holds the sleeve in a port-closed, pressure holding position, the sleeve can
only be acted
upon by the driving force once the tubing pressure generated differential is
dissipated.
The sleeve may, therefore, be actuated by pressure cycling wherein a pressure
increase
within the tubular segment causes a pressure differential that releases the
sleeve and
renders the sleeve in a condition such that it can be acted upon by a driver,
such as
existing hydrostatic pressure, to move the sleeve to a further position.
The sleeve valve of the present invention may be useful in various
applications where it
is desired to move a sleeve through a plurality of positions, where it is
desired to actuate a
sleeve to open after increasing tubing pressure, where it is desired to open a
port in a
tubing string hydraulically but where the fluid pressure must be held in the
tubing string
for other purposes prior to opening the ports to equalize pressure. In the
illustrated
embodiment, for example, sleeve 14 in both the first and second positions is
positioned to
cover port 28 and seal it against fluid flow therethrough. However, in the
third position,
sleeve 14 has moved away from port and leaves it open, at least to some
degree, for fluid
flow therethrough. Although a tubing pressure increase releases the sleeve to
move into
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the second position, the valve can still hold pressure in the second position
and, in fact,
tubing pressure creating a pressure differential across the sleeve actually
holds the sleeve
in a port closed position. Only when pressure is released after a pressure up
condition,
can the sleeve move to the port open position. Seals 30 may be provided to
assist with
the sealing properties of sleeve 14 relative to port 28. Such port 28 may open
bore 12a to
the annular area about the tubular segment, such as may be required for
wellbore stage
cementing. In one embodiment, for example, the sleeve may be moved to open
port 28
through the tubular segment such that cement from bore 12a can be passed into
the
annulus open to outer surface 12b.
In the illustrated embodiment, for example, a plurality of ports 28 pass
through the wall
of tubular segment 12 for passage of cement between bore 12a and outer surface
12d and,
in particular, the annulus about the string.
As illustrated, tool 10 may include one or more locks, as desired. For
example, a lock
may be provided to resist sleeve 14 of the valve from moving from the first
position
directly to the third position and/or a lock may be provided to resist the
sleeve from
moving from the third position back to the second position. In the illustrated
embodiment, for example, an inwardly biased c-ring 32 is installed to act
between a
shoulder 34 on tubular member 12 and a shoulder 36 on sleeve 14. By acting
between
the shoulders, they cannot approach each other and, therefore, sleeve 14
cannot move
from the first position directly toward the third position, even when shear
pins 24 are no
longer holding the sleeve. C-ring 32 does not resist movement of the sleeve
from the first
position to the second position. However, the c-ring may be held by another
shoulder 38
on tubular member 12 against movement with the sleeve, such that when sleeve
14
moves from the first position to the second position the sleeve moves past the
c-ring.
Sleeve 14 includes a gland 40 that is positioned to pass under the c-ring as
the sleeve
moves and, when this occurs, c-ring 32, being biased inwardly, can drop into
the gland.
Gland 40 may be sized to accommodate the c-ring no more than flush with the
outer
diameter of the sleeve such that after dropping into gland 40, c-ring 32 may
be carried
with the sleeve without catching again on parts beyond the gland. As such,
after c-ring
32 drops into the gland, it does not inhibit further movement of the sleeve.
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Another lock may be provided, for example, in the illustrated embodiment to
resist
movement of the sleeve from the third position back to the second position.
The lock
may also employ a device such as a c-ring 42 with a biasing force to expand
from a gland
44 in sleeve 14 to land against a shoulder 46 on tubular member 12, when the
sleeve
carries the c-ring to a position where it can expand. The gland for c-ring 42
and the
shoulder may be positioned such that they align when the sleeve moves
substantially into
the third position. When c-ring 42 expands, it acts between one side of gland
44 and
shoulder 46 to prevent the sleeve from moving from the third position back
toward the
second position.
The tool may be formed in various ways. As will be appreciated, it is common
to form
wellbore components in tubular, cylindrical form and oftentimes, of threadedly
or
weldedly connected subcomponents. For example, tubular segment in the
illustrated
embodiment is formed of a plurality of parts connected at threaded intervals.
The
threaded intervals may be selected to hold pressure, to form useful shoulders,
etc., as
desired.
Stage tool 10 has a port-recloseable function. For example, in some
applications it may
be useful to open ports 28 to permit cement flow therethrough and then later
close the
ports to hold the cement in the annulus. In one embodiment, for example,
sleeve 14 may
be moveable from the third position to a position overlying and blocking flow
through
ports. The stage tool may further include a contingency closing secondary
sleeve.
Another embodiment of a useful stage tool includes a delay hydraulic opening
device,
wherein the closure for the stage tool ports is moveable from a closed
position to an open
position, but the movement is resisted and thereby delayed. The closure is
activated by
receiving a force to shear pins on the closure so that it is allowed to begin
moving. The
force may be a physical force by a tool such as a dart passing thereby or by a
hydraulic
force, as by pressuring up. Then, once activated, the closure is restricted to
move very
slowly to the open position, the restriction being selected to delay the
opening long
enough that any pressure differential between the tubing string and the
annulus is
substantially dissipated. Thus, for example, the string inner diameter may be
pressured
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up to activate the delay hydraulic closure and then a driving force can be
applied against
the resistive force to keep the closure slowly opening. The driving force may
be by an
atmospheric pressure charge, a nitrogen dome charge, a spring, a motor, such
as an
electric motor, and/or an existing hydrostatic to move to the open position.
The resistive
force may be hydraulic fluid metering device, a frictional system, etc. In any
event, once
the stage tool goes to the open position, there is substantially no pressure
differential,
and, therefore, substantially no surge on the formation. Thereafter, cement
can be gently
circulated at low pump pressure to cement the annulus through the stage tool.
Such a stage tool is shown in Figures 3. The tool includes a tubular housing
110 defining
an inner bore 112 and an outer surface 110a, a port 114 (two ports can be
seen, but other
numbers are possible) through the wall of the tubular housing and a closure
for the port.
In this embodiment the closure is a sliding sleeve 116. The sliding sleeve has
a port-
closed position (Figure 3A), wherein the sliding sleeve maintains port 114 in
a closed
condition by overlying the port. Seals 118a, 118b, such as o-rings in glands,
act between
sleeve 116 and the tubular housing in the port-closed position to generally
prevent
leakage of fluid through the port from inner diameter 112 to outer surface
110a. Sleeve
116 is actuable and, thereafter, capable of moving to a port-open position
(Figure 3C). In
the port-open position, the port is open to fluid flow therethrough. In Figure
3C, for
example, sleeve 116 is withdrawn from over port 114, but it will be
appreciated that as
soon as the sleeve is removed from its overlapping position over the seal
118b, the port
will be open to permit some amount of fluid flow therethrough.
The system further includes a port opening delay mechanism 120 configured to
act after
actuation of the sliding sleeve 116. After the sliding sleeve 116 is in the
active position,
port opening delay mechanism 120 acts to slow movement of the port-closure
such that it
only reaches the port-open position after a selected time has lapsed, that
selected time
being longer than the time it would take the closure to move from the port-
closed to the
port-open position if the delay mechanism was not in place.
Tubular housing 110 can be foimed as a sub, such as one to be installed in a
wellbore
tubing string. Such a sub may include ends (not shown) formed for connection
to
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adjacent tubulars in the string. Suitable forming may include, for example,
threading,
tapering, etc. Generally, tubular housing 110 will be cylindrical but other
forms may be
employed.
Port 114 extends through the wall of the tubular housing, providing fluid
access through
the wall. The fluid access may flow inwardly or outwardly through the port
between
inner bore 112 and the housing's outer surface 110a (as shown).
Sliding sleeve 116 moves axially through the tubular housing when moving from
the
port-closed to the port open position. This movement could be along the outer
surface.
In this embodiment, sleeve 116 moves towards surface, arrows B, when moving to
the
port-open position, but this could be reversed with a few modifications.
Port opening delay mechanism 120 acts to slow movement of the port-closure
such that it
only reaches the port-open position after a selected time has lapsed, that
selected time
being longer than the time it would take the closure to move from the port-
closed to the
port-open position if the delay mechanism was not in place. The port opening
delay
mechanism is configured to act after actuation of sleeve 116 to resist, and
therefore delay,
opening of the port to fluid flow therethrough until after the selected time
has lapsed. In
this embodiment, the delay mechanism includes a hydraulic chamber between
housing
110 and sleeve 116 that has metered movement of hydraulic fluid therein to
slow any
movement between the parts. In particular, in the embodiment of Figures 3, as
best seen
in Figure 3D, the delay mechanism 120 includes hydraulic chamber with a
metering
valve 122 moveable therein, which separates the chamber into a first hydraulic
chamber
124 and a second hydraulic chamber 126. The metering valve is driven by
relative
movement between housing 110 and sleeve 116 to move through the chamber,
reducing
the size of one chamber, while at the same time increasing the size of the
other chamber
such that fluid must move through a restriction in metering valve 122 from one
chamber
to the other. Thus, while the sleeve, after being actuated, can move toward
its port-open
position, it is slowed in that movement by the resistance exerted by metering
valve in the
hydraulic chamber.
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The chamber is, in this embodiment, an annular space between housing 110 and
the
sleeve. Seals 128a and 128b, such as o-rings in glands, are positioned between
sleeve
116 and the inner wall of the tubular housing at either end of the chamber to
pressure
isolate the chamber from inner diameter 112 and from fluid pressures about
outer surface
110a. As such any fluid in the chamber, which may be introduced through ports
30, is
trapped in the chamber. In the illustrated embodiment, chamber 124 is filled
with air and
chamber 126 is filled with a hydraulic fluid, such as oil, both at atmospheric
pressure.
While both chambers could be filed with any fluid, a hydraulic fluid offers
predictable
viscosity and cannot immediately flow through valve 122 such that the flow,
while
capable of occurring through valve, occurs at a slow rate. While both chambers
could be
filled with the same fluid, having a compressible fluid in the receiving
chamber allows
for pressure relief should the hydraulic-fluid filled chamber undergo pressure
fluctuations
while handling, such as when being moved from surface into borehole
conditions.
Metering valve 122, in this embodiment, is secured to the outer surface of
sleeve 116.
The metering valve therefore moves with the sleeve. Metering valve 122
includes an
annular ring that separates the annular chamber into the two chambers 124,
126. The
movement of sleeve 116 to achieve port-opening, forces metering valve 122 to
move
through the chamber to increase the volume of first chamber 124 while reducing
the
volume of second chamber 126. In response to this relative volume change
between the
two chambers, one's volume increasing and the other's volume decreasing,
hydraulic fluid
in the chamber of decreasing volume must pass the restriction presented by
metering
valve to permit the sleeve movement. In the illustrated embodiment, the
restriction
includes an orifice 132 providing limited fluid movement between the two
chambers 124,
126 through openings 132a, 132b. Seals 134 prevent fluid from bypassing around
the
piston. While sleeve could otherwise move readily within the housing, the
movement is
resisted by the restriction of metering valve 122 moving through the hydraulic-
fluid-filled
chamber. Thus, the valve 122 slows movement of the sleeve, corresponding to
the rate at
which the hydraulic fluid in the chamber may pass through the valve's fluid
orifice 132.
It will be appreciated that various modifications can be made to the delay
mechanism.
For example, the piston could be carried on the housing. In one embodiment,
the delay
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mechanism is adjustable to control the degree of resistance imparted thereby.
For
example in an embodiment employing a hydraulic chamber, the viscosity of the
hydraulic
fluid and/or the size of the valve orifice can be selected, to control the
metering effect and
therefore the delay imparted by the mechanism.
The port closure, in this embodiment, sleeve 116 may be actuated to begin the
port
opening process by a pressure driven mechanism. The pressure driven mechanism
actuates the closure to an active position (Figure 3B) where the closure can
move from
the port-closed position to the port-open position. The pressure driven
mechanism may
vary depending on the sleeve. In one embodiment, for example, the pressure
driven
mechanism is incorporated in the closure mechanism such as, for example, in a
fluid
pressure responsive valve as described above. As described therein, the fluid
pressure
responsive valve is actuated in response to pressure differentials across the
valve to begin
opening. The actuation is a release of the sleeve such that it becomes free to
move to the
port-open position.
In Figures 3, the pressure driven mechanism involves the use of a pressure
driven tool.
Figures 3A to 3E show one embodiment of a tool and Figures 3F and 3G show
another
embodiment. In Figures 3A to 3E: Figure 3E shows the assembly pre-actuation
(in a run-
in condition); Figure 3A shows the assembly mid-actuation; Figure 3B shows the
assembly after actuation, when sleeve 116 is activated and ready to move; and
Figure 3C
shows the assembly after sleeve 116 has moved. In Figures 3F and 3G: Figure 3F
shows
the assembly mid-actuation and Figure 3G shows the assembly after actuation,
when
sleeve 116 has moved.
In these embodiments, sleeve 116 is actuated to begin the port opening process
by a
pressure driven tool that acts by direct contact or proximity to actuate the
closure to begin
moving to the port-open position. The pressure driven tool is drivable through
the
tubular housing by fluid pressure. The pressure driven tool may take various
forms, for
example, it may be single or multipart. In one embodiment, for example, the
pressure
driven tool includes a conveyed part, such as a plug 136, for example a ball
(as shown) or
dart, etc. that lands against a release mechanism, such as a sleeve with a
seat, a latch, etc.
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that is substantially not pressure drivable until the conveyed part is landed
thereagainst.
In the illustrated embodiment, for example, the assembly includes an
activation sleeve
140 with a seat 142 formed thereon sized to act with plug 136. Plug 136 and
seat 142 are
correspondingly sized such that when plug 136 is pressure driven through the
tubular
housing 110, the plug cannot pass through the seat. Plug 136 therefore lands
on the
activation sleeve's seat 142 and, the sleeve with the plugging device landed
therein,
occludes inner bore 112 of the tubular housing to create a pressure
differential across the
activation sleeve. Sleeve 140, therefore, can be driven along by the pressure
differential
toward the low pressure side, arrow A, and this movement can actuate, and in
particular
release, sleeve 116 to begin to move, arrow B, to the port-open position
(Figure 3C).
The pressure driven tool can serve further purposes in the wellbore. For
example, in one
embodiment as shown, plug 136, once having actuated the sleeve, may pass
through seat
142 and may continue on and land on a seat (not shown) below. The seat may
serve
various purposes, after it has plug 136 landed therein. For example, it may
act to divert
fluid to ports 114, once they are opened. As such, seat 142, while formed to
initially
retain plug 136, may also be formed to be overcomeable, such as by
deformation, so that
plug 136 can pass through the seat and proceed downhole.
The actuation assembly as illustrated, includes activation sleeve 140 with
seat 142 and
plug 136 sized to be retained in seat 142 long enough to cause actuation of
the system.
Seat 142 is deformable and includes a main body 142a installed in sleeve 140
and a
subsleeve 142b slidably installed in a bore through main body 142a. The
subsleeve 142b
defines the bore through which plug 136 passes and is retained. In particular,
annular
ledge 142c creates a stop against which the plug is caught when passing
through the bore
of the subsleeve 142b. The subsleeve is locked in a first position by keys
142d, Figure
3A, 11E. In the first position, subsleeve 142b is captured radially in the
bore of main
body 142a such that the subsleeve's walls about ledge 142c cannot radially
expand.
However, if keys 142d are retracted, the subsleeve is freed to move to a
second position,
Figure 3B. In the second position, the subsleeve's walls about ledge 142c
extend into an
enlarged diameter area in the bore of main body 142a, such that the walls can
be
expanded radially to enlarge the diameter across ledge 142c. Keys 142d can
retract when
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main activation sleeve 140 moves down into a releasing position (Figure 3B,
3F), where
the keys 142d are positioned in a space where they have room to retract. Plug
136 is
retained in subsleeve 142b when it is in the first position and plug 136 can
pass through
subsleeve 142b when it is in the second position, which is the position
achieved after plug
136 has driven activation sleeve 140 to actuate sleeve 116.
While activation sleeve 140 could operate in numerous ways to actuate sleeve
116, to
free it for movement, it is noted that sleeve 140 is initially secured to
sleeve 116 by a C-
ring lock 144 wedged between the sleeves. C-ring lock 144 is positioned in an
annular
gland 146 in an end extension of sleeve 116 and is supported at its back side
by an
annular extension 140a of sleeve 140. When sleeve 140 is pulled out from
behind C-ring
lock 144, it is free to expand out of gland 146 and sleeve 116 is freed by the
actuation
assembly to move.
The actuator may include a releasable lock that is released by the pressure
driven
mechanism. For example, shear pins may be employed to ensure sleeve 140 is
initially
locked in position. Shear pins 150 may be used to ensure that sleeve 116 does
not
inadvertently move out of position. However, the shear pins are selected to
have a
holding force capable of being overcome by appropriate pressures.
Locks may also be employed to hold the parts in their final positions. For
example, a C-
ring lock 151 may be employed to ensure sleeve 140 remains in its position
after
activation of sleeve 116. C-ring lock 152 may be positioned to engage between
sleeve
116 and housing 110 after sleeve 116 has moved to the port-open position, to
ensure that
sleeve 116 does not inadvertently move out of the port-open position.
While a sleeve with a deformable subsleeve has been disclosed as the
activation
mechanism for the system, the activation of sleeve 116 for movement may be
accomplished in various ways. For example, Figure 3F shows an alternative
deformable
seat. In this embodiment, seat 142 is formed by a plurality of collet fingers
182 that are
compressed together during run in to form the ball-catching seat, but are
pushed into a
WSLEGAL\045023 \00417\11731577v3
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recess 184 that allows fingers to expand, when the activation sleeve 184 is
driven by the
plug and fluid pressure.
The above-noted pressure driven plugging device and sleeve actuates the
closure by
direct manipulation. In another embodiment, the pressure driven tool may
operate by
proximity such as by emitting a signal that is detected by the closure. In
such an
embodiment, for example, the pressure driven tool is conveyable, such as
including a
non-plugging dart, a plug (such as a ball or dart), etc. that emits a signal
and the closure's
actuator includes a receiver that receives the signal. The pressure driven
tool signals the
actuator to begin the opening process, when the pressure driven tool passes in
signaling
proximity thereto. In one of these embodiments, for example, the conveyed tool
and
actuator may employ RF technology for emitters and receivers. Such technology
is
disclosed, for example, in US Patent Document 2007/0272411. As such, it is to
be
understood that there are various ways to actuate the closure to assume its
port-open
condition.
From the foregoing, it will be appreciated that the pressure driven tool may
actuate the
closure to begin opening, but in this embodiment does not actually drive the
closure open.
For example, in one embodiment, a conveyed tool may land against a tubing ID
restriction and may apply a force as it passes the restriction, which force
actuates the
closure to begin the opening process. However, the conveyed tool may activate
the stage
tool to initiate opening but the conveyed tool does not actually drive the
closure open. In
such an embodiment, a driver may be required, as discussed below, to impart a
drive
force to the closure. Thus, the port closure system may further include a
driver that
provides the energy to move the closure to the open position, after it is
actuated. The
driver may include one or more of a motor, a biasing member such as a spring
or a
pressure charge (i.e. a nitrogen chamber charge or an atmospheric pressure
chamber), a
piston configuration to respond to differential well/tubing pressures, etc.
While the driver
may be capable of applying a force to rapidly move the closure from the port-
closed to
the port-open position, the port opening delay mechanism resists and therefore
slows
such movement. A driver may permit a closure to be moved without maintaining
the
original pressure drive that initiated the movement. For example, if the
actuation is by
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pressuring up the tubing string, the pressure may be dissipated but the driver
continues to
apply a driving force to the sleeve. In one embodiment, the driver may be
selected to
operate apart from the actuation of the closure. For example, the driver may
be a biasing
member that generates or stores energy that can only be dissipated after the
sleeve is
actuated to begin opening. In the illustrated embodiment, the driver includes
opposing
piston faces across which a pressure differential is established to drive the
sleeve toward
the lower pressure side. For example, seals 128a create one piston face and
seals 128b
create a second piston face. The larger diameter of seals 128b over seals 128a
provides a
greater surface area of seal 128b vs. seal 128a. The greater surface area of
seals 128b
compared to seals 128a creates a pressure differential across atmospheric
chambers 124,
126 that drives the sleeve toward seals 128a. Fluid can be communicated to
seals 128b
through fluid ports 129.
Once the port 114 is open, it can remain open until cementing is complete and
then it can
be closed to trap the cement in the wellbore annulus against the outer surface
of the stage
tool. A plug or running tool could be deployed after the fact to selectively
close the port,
after it is opened.
The delay mechanism allows pressurized operation to open the port but the port
remains
closed to fluid flow therethrough until after a selected time which allows
time for the
pressure to be dissipated before the ports are actually opened. For example,
with
reference to Figures 3, the delay mechanism is in place to ensure that there
is sufficient
time to allow the pressure required to convey activation device, plug 136, to
dissipate
before communication is established with the wellbore.
In operation, the stage tool may be installed in a string and run into a
wellbore. Plug 136
is released uphole of tubular 110 and is conveyed by gravity and fluid
pressure to
activation sleeve 140. When plug 136 reaches sleeve 140, it lands in seat 142.
Pressure
is increased from surface to break shear pins (not shown) and the sleeve 140
moves down
(arrow A). This allows the release of C-ring lock 144. Lock ring 151 locks
sleeve 140 in
the shifted position when the ring expands behind a shoulder 153 in housing
110. After
the sleeve shifts, the plug 136 continues to create a seal in the seat.
Increased pressure
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yields the seat and allows the plug 136 to continue down the string. In
particular, seat
142 yields when subsleeve 142b shifts and ledge 142c expands to release the
plug. In
another embodiment, plug 136 remains in the seat.
With the release of C-ring lock 144, sleeve 116 is considered actuated, being
free to
move. Any pressure in the string then can act on the differential areas of
seals 128a,
128b against the fluid filled chambers 124, 126. This causes sleeve 116 to
begin shifting
and overcomes any holding force exerted by shear pins 150. In this embodiment,
the
movement of sleeve 116 is uphole. Any movement of the sleeve is resisted and
therefore
slowed by the changing volume of chambers 124, 126, metering valve 122 between
the
chambers and the viscosity of the hydraulic fluid in chamber 126, which
together act as a
delay mechanism. In particular, the differential forces between seals 128a and
128b
acting against the atmospheric conditions of the fluid in chambers, causes
sleeve 116 to
move toward seals 128a and this movement causes metering valve 122 to move
with the
sleeve through the annular chamber such that fluid is forced from chamber 126
to
chamber 124 through orifice 132 of metering valve 122. In this embodiment, a
driving
force is applied to the sleeve after actuation thereof by ensuring that the
seals 128a, 128b
have a differential area and by selecting the pressure in the chambers to be
less than the
downhole pressures, considering the downhole temperature and pressure
conditions. The
delay mechanism acts against the force applied by the driver and slows the
movement of
the sleeve.
The driving force causes sleeve to continue to move until it is stopped for
example when
C-ring lock 152 expands into a gland in chamber 124 or become butted against a
stop
wall. In so doing sleeve 116 is withdrawn from its position covering port 114
such that
port is opened. The driver, which is the effect of the differential areas of
seals 128a, 128b
acting against the atmospheric chambers 124, 126, continues to apply a driving
force on
the sleeve while tubing pressure is dissipated and even after the port opens.
While the above-noted sleeve is driven by pressure differentials between seals
128a, 128b
acting against the atmospheric chambers 124, 126, it is to be understood that
the driver
that applies a driving force against the resistance of the delay mechanism,
chambers 124,
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WSLEGAL\045023\00417\11731577v3
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126, could take other forms. For example, in one embodiment, the driver may be
a
pressure charged chamber, such as one containing nitrogen. In another
embodiment, a
spring may be used as the driver. In these embodiments, the pressure charge
and the
spring act to apply the driving force to urge the sleeve open, against the
resistance of the
delay mechanism.
Port 116 only opens after time is permitted to allow the pressure in inner
bore to
substantially equalize to the pressure about the outer surface. Once port 116
is opened,
stage cementing can proceed. For example, in one embodiment cement is pumped
out
though port 116 and into the annulus about the outer surface of the stage
tool.
The previous description of the disclosed embodiments is provided to enable
any person
skilled in the art to make or use the present invention. Various modifications
to those
embodiments will be readily apparent to those skilled in the art, and the
generic
principles defined herein may be applied to other embodiments. Thus, the
present
invention is not intended to be limited to the embodiments shown herein, but
is to be
accorded the full scope consistent with the claims, wherein reference to an
element in the
singular, such as by use of the article "a" or "an" is not intended to mean
"one and only
one" unless specifically so stated, but rather "one or more". All structural
and functional
equivalents to the elements of the various embodiments described throughout
the
disclosure that are known or later come to be known to those of ordinary skill
in the art
are intended to be encompassed by the elements of the claims. Moreover,
nothing
disclosed herein is intended to be dedicated to the public regardless of
whether such
disclosure is explicitly recited in the claims. No claim element is to be
construed under
the provisions of 35 USC 112, sixth paragraph, unless the element is expressly
recited
using the phrase "means for" or "step for".
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