Note: Descriptions are shown in the official language in which they were submitted.
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SNORKEL DEVICE FOR FLOW CONTROL
Cross-Reference to Related Application
This application is a divisional application from Canadian Patent Application
Number 2,535,080 filed February 2, 2006.
Background of the Invention
[0001] Field of Invention. The present invention pertains to downhole flow
control devices, and particularly to downhole flow control devices using a
common
control line as a pressure source for operation.
[0002] Related Art. In running intelligent completions into subterranean
wells,
there are often limitations on the number of control line penetrations that
can be made at
the wellhead, the tubing hanger, or, in some cases, the production packer.
j0003] Intelligent completions use various means to regulate flow control
devices
placed downhole to control production from various zones. Such flow control
devices,
valves, for example; can typically be fully open, partially open (choked), or
fully closed.
Using a plurality of such valves allows an operator to selectively receive or
restrict
production from different zones. A simple version of such a flow control
device would
typically have two control lines, one acting on either side of a piston. When
multiple
valves of that kind are run in the hole, the number of control lines required
becomes a
problem. For example, three valves would require six control lines.
[0004] There also exist single control line flow control devices that rely on
energy
stored in the downhole device, such as a charge of compressed gas (e.g.,
nitrogen spring)
or a mechanical spring working in conjunction with either the annular or
tubing pressure.
Since downhole conditions may change over time, selection of the spring or
nitrogen
charge is critical and may limit the operational envelope of the flow control
device.
Various multiplexing schemes have been employed, but those typically require
some
complex scheme of valves to allow pressures at different levels to address one
valve or
another. A common return line has been proposed for simple, two position-type
valves
(i.e., open/close valves), but operation can be tricky as one must carefully
assess the state
of each valve to determine the proper pressure sequence to apply to the
various control
lines at surface.
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Summary
[0005] The present invention provides for the operation
of a downhole flow control device using a snorkel.
The invention relates to a snorkel device for use
in a well comprising: a flow control device; and a snorkel in
fluid communication with the flow control device to provide a
reference pressure for running the flow control device, the
snorkel extending to another zone in the well to serve as a
pressure regulator for the flow control device such that
pressure equalization and pressure adjustment during changes in
well pressure can be performed automatically, wherein the
snorkel terminates above a packer.
The invention also relates to a snorkel device
for flow control in a well comprising: a plurality of flow
control devices, each flow control device being in fluid
communication with a distinct control line; and a snorkel
in fluid communication with each flow control device.
The invention further relates to a method to
operate a flow control device in a well comprising: placing the
flow control device in a desired location in the well, the flow
control device being joined to a control line and a snorkel;
cycling the pressure in the control line above and below the
pressure in the snorkel to change the state of the flow control
device; using the snorkel to establish a reference pressure for
running the flow control device by extending the snorkel to
another zone in the well; operating the snorkel as a pressure
regulator for the flow control device such that pressure
equalization and pressure adjustment during changes in well
pressure can be performed automatically; and setting a packer
through which the control line and snorkel pass.
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The invention still further relates to a method
to establish a reference pressure for a tool in a well
comprising: using a snorkel to establish a reference pressure
for operating the tool in the well; positioning the snorkel to
transfer fluid pressure from one location above a packer in the
well to another location in the well; and utilizing the snorkel
as a pressure regulator for the tool such that pressure
equalization and pressure adjustment during changes in well
pressure can be performed automatically.
The invention yet further relates to a snorkel
device for use in a well comprising: a packer to isolate a
first production zone in the well from a second production
zone in the well; a first flow control device located in
the first production zone, the first flow control device
having a proportional controller; and a snorkel in fluid
communication with the first flow control device.
[0006] Advantages and other features of the invention
will become apparent from the following description,
drawings, and claims.
Brief Description of Drawings
[0007] Figure 1 shows a schematic view of a snorkel
device constructed in accordance with the present
invention.
[0008] Figure 2 shows a schematic view of an
alternative embodiment of the snorkel device of Figure 1.
[0009] Figure 3 shows a schematic view of a flow
control device used in the embodiment of the snorkel
device of Figure 2.
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Detailed Description
[0010] Figure 1 shows a snorkel device 10 being used to
operate a set of valves such as multi-position hydraulic
valves 12, 14, 16 in a well. The valves could also be
on/off valves. The invention is not limited to use on
valves, however. For example, the flow control device
could be a choke. Each valve 12, 14, 16 has a control
line 18, 20, 22, respectively, and an indexer 23 to shift
the valve to each of its various state positions. A
snorkel 24 is joined to each valve 12, 14, 16. Snorkel 24
is preferably a small diameter tubing such as that
commonly used for a control line. Snorkel 24 may be run
to the surface, but prefcrably terminates at its upper end
26 jusl. above a production packer 28. If upper end 26 of
snorkel 24 terminates at some level in the well, a
compensator 30 may be joined to upper end 26 to prevent
co-mingling of wellbore fluids with clean hydraulic fluid.
Compensator 30 allows fluid pressure in the annulus to be
transferred to the hydraulic fluid in snorkel 24 without
co-mingling. Though shown joined at upper end 26,
compensator 30 may be located anywhere in snorkel 24.
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[0011] In operation, valve 12, for example, uses indexer 23 to advance the
valve
state (e.g., from partially open to fully open) one position each time
sufficient pressure is
applied to control line 18. Indexer 23 is moved by a piston (not shown) being
driven by
hydraulic pressure. To further advance the state position of the valve, the
pressure in
control line 18 is lowered and pressure is supplied to the backside of the
piston to reset
indexer 23. The resetting force may be reinforced by a spring force, as is
known in the
art. Pressure can then be applied to control line 18 again, driving the piston
and thereby
advancing indexer 23 and the valve state. Valves 14, 16 operate similarly via
control
lines 20, 22, respectively.
[0012] Snorkel 24 is in fluid communication with the backside of the piston in
each valve 12, 14, 16. Hydraulic pressure in snorkel 24 provides a return
force to each
piston. If snorkel 24 terminates at its upper end at. some level in the well,
the fluid
pressure in the well at that particular level serves as the source of the
hydraulic pressure
applied to the backside of each piston. The pressure at that particular level
could be the
ambient hydrostatic pressure, or it could be modified by changing the annular
pressure at
the surface using conventional methods. The fluid pressure in snorkel 24
establishes a
reference pressure against which downhole tools may be operated.
[0013] In the embodiment of Figure 1, three downhole flow control devices are
shown. However, the invention is not limited to three and may be used with as
few as
one.
[0014] In Figure 2, an alternative embodiment using snorkel device 10 is
shown.
In this embodiment, a first flow control device 32 is located in a high-
pressure production
zone 34 and a second flow control device 36 is located in a low-pressure
production zone
38. Flow control devices 32, 36 selectively control the inflow of formation
fluids into a
production tubing 40, but snorkel device 10 is not limited to those devices
and may be
used in safety valves and gas lift valves, as well as other devices.
[0015] Because high-pressure production zone 34 is at a higher pressure than
low-pressure production zone 38, formation fluids from high-pressure
production zone 34
need to be choked back so they may be introduced into tubing 40 at
substantially the
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same pressure as that in low-pressure production zone 38. Equalizing the
pressure
reduces the possibility of cross-flow between the formations. Although only
two
production zones are discussed in this example, other production zones may be
present
and the scope of the present invention includes those additional zones.
[0016] Figure 3 shows first flow control device 32 with a proportional
controller
42 to adjust the flow area based upon the differential pressure between high-
pressure
production zone 34 and low-pressure production zone 38. Proportional
controller 42 uses
differential areas and a spring 45 to adjust the flow area into production
tubing 40 via
flow control device 32.
[0017] Proportional controller. 42 may take many forms. In the example shown
in
Figure 3, pressure from high-pressure zone 34 acts on a first side of a piston
44. A
second side of piston 44 is acted on by a combination of pressure from low-
pressure
production zone 38 and a spring force. The spring force may be from, for
example,
mechanical spring 45 or a gas charge. Displacement of piston 44 changes the
position of
controller 42, which causes flow control device 32 to cover or uncover flow
openings
into production tubing 40, thereby decreasing or increasing flow. Depending on
the
particular design of the flow openings and spring selected, flow control
device 32 may
behave linearly or non-linearly with respect to fluid flow (and
correspondingly, pressure
drop) as a function of piston displacement.
[0018] The pressure from low-pressure production zone 38 is communicated to
the second side of piston 44 by snorkel tube 24. Snorkel 24 is run through an
isolation
packer 46 separating zones 34, 38. Thus, the position of controller 42 is
based on the
differential pressure between high-pressure production zone 34 and low-
pressure
production zone 38. If formation pressures should change over time, controller
42 will
automatically adjust to compensate and maintain the pressure balance.
[0019] Flow from low-pressure production zone 38 enters tubing 40 via second
flow control device 36. Second flow control device 36 may be any of various
conventional devices such as sliding sleeves, slotted pipe, or perforated
pipe.
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[0020] As in the embodiment of Figure 1, a compensator 30 may be joined to
snorkel 24 to isolate formation fluids from fluid within snorkel 24 in the
embodiment of
Figure 2. A tubing pressure override device (not shown) could be included to
allow flow
control devices 32, 36 to be run into the well in an open or closed position
and
subsequently be activated by applying tubing pressure. Gas or water detectors
may also
be incorporated to trigger the operation of a flow control device to reduce or
eliminate
flow from a particular zone.
[0021] Although only a few exemplary embodiments of this invention have been
described in detail above, those skilled in the art will readily appreciate
that many
modifications are possible in the exemplary embodiments without materially
departing
from the novel teachings and advantages of this invention. Accordingly, all
such
modifications are intended to be included within the scope of this invention
as defined in
the following claims. In the claims, means-plus-function clauses are intended
to cover
the structures described herein as performing the recited function and not
only structural
equivalents, but also equivalent structures. Thus, although a nail and a screw
may not be
structural equivalents in that a nail employs a cylindrical surface to secure
wooden parts
together, whereas a screw employs a helical surface, in the environment of
fastening
wooden parts, a nail and a screw may be equivalent structures. It is the
express intention
of the applicant not to invoke 35 U.S.C. 112, paragraph 6 for any
limitations of any of
the claims herein, except for those in which the claim expressly uses the
words `means
for' together with an associated function.
