Note: Descriptions are shown in the official language in which they were submitted.
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SNEAK PATH ELIMINATOR FOR DIODE MULTIPLEXED
CONTROL OF DOWNHOLE WELL TOOLS
BACKGROUND
[0001] The present disclosure relates generally to operations performed and
equipment utilized
in conjunction with a subterranean well and, in an embodiment described
herein, more
particularly provides for sneak path elimination in diode multiplexed control
of downhole well
tools.
[0001] It is useful to be able to selectively actuate well tools in a
subterranean well. For example,
production flow from each of multiple zones of a reservoir can be individually
regulated by
using a remotely controllable choke for each respective zone. The chokes can
be interconnected
in a production tubing string so that, by varying the setting of each choke,
the proportion of
production flow entering the tubing string from each zone can be maintained or
adjusted as
desired.
[0002] Unfortunately, this concept is more complex in actual practice. In
order to be able to
individually actuate multiple downhole well tools, a relatively large number
of wires, lines, etc.
have to be installed and/or complex wireless telemetry and downhole power
systems need to be
utilized. Each of these scenarios involves use of relatively unreliable
downhole electronics
and/or the extending and sealing of many lines through bulkheads, packers,
hangers, wellheads,
etc.
[0003] Therefore, it will be appreciated that advancements in the art of
remotely actuating
downhole well tools are needed. Such advancements would preferably reduce the
number of
lines, wires, etc. installed, would preferably reduce or eliminate the need
for downhole
electronics, and would preferably prevent undesirable current draw.
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SUMMARY
[0004] In carrying out the principles of the present disclosure, systems and
methods are provided
which advance the art of downhole well tool control. One example is described
below in which a
relatively large number of well tools may be selectively actuated using a
relatively small number
of lines, wires, etc. Another example is described below in which a direction
of current flow
through a set of conductors is used to select which of two respective well
tools is to be actuated.
Yet another example is described below in which current flow is not permitted
through
unintended well tool control devices.
[0005] In one aspect, a system for selectively actuating from a remote
location multiple
downhole well tools in a well is provided. The system includes at least one
control device for
each of the well tools, such that a particular one of the well tools can be
actuated when a
respective control device is selected. Conductors are connected to the control
devices, whereby
each of the control devices can be selected by applying a predetermined
voltage potential across
a respective predetermined pair of the conductors. At least one lockout device
is provided for
each of the control devices, whereby the lockout devices prevent current from
flowing through
the respective control devices if the voltage potential across the respective
predetermined pair of
the conductors is less than a predetermined minimum.
[0006] In another aspect, a method of selectively actuating from a remote
location multiple
downhole well tools in a well is provided. The method includes the steps of:
selecting a first one
of the well tools for actuation by applying a predetermined minimum voltage
potential to a first
set of conductors in the well; and preventing actuation of a second one of the
well tools when the
predetermined minimum voltage potential is not applied across a second set of
conductors in the
well. At least one of the first set of conductors is the same as at least one
of the second set of
conductors.
[0007] In yet another aspect, a system for selectively actuating from a remote
location multiple
downhole well tools in a well includes at least one control device for each of
the well tools, such
that a particular one of the well tools can be actuated when a respective
control device is
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selected; conductors connected to the control devices, whereby each of the
control devices can
be selected by applying a predetermined voltage potential across a respective
predetermined pair
of the conductors; and at least one lockout device for each of the control
devices, whereby each
lockout device prevents a respective control device from being selected if the
voltage potential
across the respective predetermined pair of the conductors is less than a
predetermined
minimum.
[00089] One of the conductors may be a tubular string extending into the
earth, or in effect
"ground."
[0009] These and other features, advantages, benefits and objects will become
apparent to one of
ordinary skill in the art upon careful consideration of the detailed
description of representative
embodiments of the disclosure herein below and the accompanying drawings, in
which similar
elements are indicated in the various figures using the same reference
numbers.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a schematic view of a prior art well control system.
[0011] FIG. 2 is an enlarged scale schematic view of a flow control device and
associated
control device which embody principles of the present disclosure.
[0012] FIG. 3 is a schematic electrical and hydraulic diagram showing a system
and method for
remotely actuating multiple downhole well tools.
[0013] FIG. 4 is a schematic electrical diagram showing another configuration
of the system and
method for remotely actuating multiple downhole well tools.
[0014] FIG. 5 is a schematic electrical diagram showing details of a switching
arrangement
which may be used in the system of FIG. 4.
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[0015] FIG. 6 is a schematic electrical diagram showing details of another
switching
arrangement which may be used in the system of FIG. 4.
[0016] FIG. 7 is a schematic electrical diagram showing the configuration of
FIG. 4, in which a
current sneak path is indicated.
[0017] FIG. 8 is a schematic electrical diagram showing details of another
configuration of the
system and method, in which under-voltage lockout devices prevent current
sneak paths in the
system.
[001819] FIG. 9 is a schematic electrical diagram showing details of
another configuration
of the system and method, in which another configuration of under-voltage
lockout devices
prevent current sneak paths in the system.
[0019] FIG. 10 is a schematic electrical diagram showing details of another
configuration of the
system and method, in which yet another configuration of under-voltage lockout
devices prevent
current sneak paths in the system.
[0020] FIG. 11 is a schematic electrical diagram showing details of another
configuration of the
system and method, in which a further configuration of under-voltage lockout
devices prevent
current sneak paths in the system.
[0021] FIG. 12 is a schematic electrical diagram showing details of another
configuration of the
system and method, in which a further configuration of the lockout devices
prevent current sneak
paths in the system.
[0022] FIG. 13 is a schematic electrical diagram showing details of another
configuration of the
system and method, in which a further configuration of the lockout devices
prevents current
sneak paths in the system.
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[0023] FIG. 14 is a schematic electrical diagram showing details of another
configuration of the
system and method utilizing SCRs.
[0024] FIG. 15 is a schematic electrical diagram showing details of another
configuration of the
system and method for controlling bidirectional load devices, such as motors.
[00256] FIG. 16 is a schematic electrical diagram showing details of another
configuration of the
system and method utilizing alternate lock-out devices.
DETAILED DESCRIPTION
[0026] It is to be understood that the various embodiments of the present
disclosure described
herein may be utilized in various orientations, such as inclined, inverted,
horizontal, vertical, etc.,
and in various configurations, without departing from the principles of the
present disclosure.
The embodiments are described merely as examples of useful applications of the
principles of
the disclosure, which is not limited to any specific details of these
embodiments.
[00278] In the following description of the representative embodiments of the
disclosure,
directional terms, such as "above," "below," "upper," "lower," etc., are used
for convenience in
referring to the accompanying drawings. In general, "above," "upper," "upward"
and similar
terms refer to a direction toward the earth's surface along a wellbore, and
"below," "lower,"
"downward" and similar terms refer to a direction away from the earth's
surface along the
wellbore.
[002829] Representatively illustrated in FIG. 1 is a well control system 10
which is used to
illustrate the types of problems inherent in prior art systems and methods.
Although the drawing
depicts prior art concepts, it is not meant to imply that any particular prior
art well control system
included the exact configuration illustrated in FIG. 1.
[0029] The control system 10 as depicted in FIG. 1 is used to control
production flow from
multiple zones 12a-e intersected by a wellbore 14. In this example, the
wellbore 14 has been
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cased and cemented, and the zones 12a-e are isolated within a casing string 16
by packers 18a-e
carried on a production tubing string 20.
[0030] Fluid communication between the zones 12a-e and the interior of the
tubing string 20 is
controlled by means of flow control devices 22a-e interconnected in the tubing
string. The flow
control devices 22a-e have respective actuators 24a-e for actuating the flow
control devices open,
closed or in a flow choking position between open and closed.
[00312] In this example, the control system 10 is hydraulically operated, and
the actuators 24a-e
are relatively simple piston-and-cylinder actuators. Each actuator 24a-e is
connected to two
hydraulic lines--a balance line 26 and a respective one of multiple control
lines 28a-e. A pressure
differential between the balance line 26 and the respective control line 28a-e
is applied from a
remote location (such as the earth's surface, a subsea wellhead, etc.) to
displace the piston of the
corresponding actuator 24a-e and thereby actuate the associated flow control
device 22a-e, with
the direction of displacement being dependent on the direction of the pressure
differential.
[00323] There are many problems associated with the control system 10. One
problem is that a
relatively large number of lines 26, 28a-e are needed to control actuation of
the devices 22a-e.
These lines 26, 28a-e must extend through and be sealed off at the packers 18a-
e, as well as at
various bulkheads, hangers, wellhead, etc.
[0033] Another problem is that it is difficult to precisely control pressure
differentials between
lines extending perhaps a thousand or more meters into the earth. This can
lead to improper or
unwanted actuation of the devices 22a-e, as well as imprecise regulation of
flow from the zones
12a-e.
[0034] Attempts have been made to solve these problems by using downhole
electronic control
modules for selectively actuating the devices 22a-e. However, these control
modules include
sensitive electronics which are frequently damaged by the hostile downhole
environment (high
temperature and pressure, etc.).
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[0035] Furthermore, electrical power must be supplied to the electronics by
specialized high
temperature batteries, by downhole power generation or by wires which (like
the lines 26, 28a-e)
must extend through and be sealed at various places in the system. Signals to
operate the control
modules must be supplied via the wires or by wireless telemetry, which
includes its own set of
problems.
[0036] Thus, the use of downhole electronic control modules solves some
problems of the
control system 10, but introduces other problems. Likewise, mechanical and
hydraulic solutions
have been attempted, but most of these are complex, practically unworkable or
failure-prone.
[0037] Turning now to FIG. 2, a system 30 and associated method for
selectively actuating
multiple well tools 32 are representatively illustrated. Only a single well
tool 32 is depicted in
FIG. 2 for clarity of illustration and description, but the manner in which
the system 30 may be
used to selectively actuate multiple well tools is described more fully below.
[003839] The well tool 32 in this example is depicted as including a flow
control device 38 (such
as a valve or choke), but other types or combinations of well tools may be
selectively actuated
using the principles of this disclosure, if desired. A sliding sleeve 34 is
displaced upwardly or
downwardly by an actuator 36 to open or close ports 40. The sleeve 34 can also
be used to
partially open the ports 40 and thereby variably restrict flow through the
ports.
[00390] The actuator 36 includes an annular piston 42 which separates two
chambers 44, 46. The
chambers 44, 46 are connected to lines 48a,b via a control device 50. D.C.
current flow in a set
of electrical conductors 52a,b is used to select whether the well tool 32 is
to be actuated in
response to a pressure differential between the lines 48a,b.
[00401] In one example, the well tool 32 is selected for actuation by flowing
current between the
conductors 52a,b in a first direction 54a (in which case the chambers 44, 46
are connected to the
lines 48a,b), but the well tool 32 is not selected for actuation when current
flows between the
conductors 52a,b in a second, opposite, direction 54b (in which case the
chambers 44, 46 are
isolated from the lines 48a,b). Various configurations of the control device
50 are described
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below for accomplishing this result. These control device 50 configurations
are advantageous in
that they do not require complex, sensitive or unreliable electronics or
mechanisms, but are
instead relatively simple, economical and reliable in operation.
[0041] The well tool 32 may be used in place of any or all of the flow control
devices 22a-e and
actuators 24a-e in the system 10 of FIG. 1. Suitably configured, the
principles of this disclosure
could also be used to control actuation of other well tools, such as selective
setting of the packers
18a-e, etc.
[0042] Note that the hydraulic lines 48a,b are representative of one type of
fluid pressure source
48 which may be used in keeping with the principles of this disclosure. It
should be understood
that other fluid pressure sources (such as pressure within the tubing string
20, pressure in an
annulus 56 between the tubing and casing strings 20, 16, pressure in an
atmospheric or otherwise
pressurized chamber, etc., may be used as fluid pressure sources in
conjunction with the control
device 50 for supplying pressure to the actuator 36 in other embodiments.
[0043] The conductors 52a,b comprise a set of conductors 52 through which
current flows, and
this current flow is used by the control device 50 to determine whether the
associated well tool
32 is selected for actuation. Two conductors 52a,b are depicted in FIG. 2 as
being in the set of
conductors 52, but it should be understood that any number of conductors may
be used in
keeping with the principles of this disclosure. In addition, the conductors
52a,b can be in a
variety of forms, such as wires, metal structures (for example, the casing or
tubing strings 16, 20,
etc.), or other types of conductors.
[00445] The conductors 52a,b preferably extend to a remote location (such as
the earth's surface,
a subsea wellhead, another location in the well, etc.). For example, a surface
power supply and
multiplexing controller can be connected to the conductors 52a,b for flowing
current in either
direction 54a,b between the conductors.
[0045] In the examples described below, n conductors can be used to
selectively control
actuation of n*(n-1) well tools. The benefits of this arrangement quickly
escalate as the number
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of well tools increases. For example, three conductors may be used to
selectively actuate six well
tools, and only one additional conductor is needed to selectively actuate
twelve well tools.
[0046] Referring additionally now to FIG. 3, a somewhat more detailed
illustration of the
electrical and hydraulic aspects of one example of the system 30 are provided.
In addition, FIG.
3 provides for additional explanation of how multiple well tools 32 may be
selectively actuated
using the principles of this disclosure.
[00478] In this example, multiple control devices 50a-c are associated with
respective multiple
actuators 36a-c of multiple well tools 32a-c. It should be understood that any
number of control
devices, actuators and well tools may be used in keeping with the principles
of this disclosure,
and that these elements may be combined, if desired (for example, multiple
control devices could
be combined into a single device, a single well tool can include multiple
functional well tools, an
actuator and/or control device could be built into a well tool, etc.).
[004849] Each of the control devices 50a-c depicted in FIG. 3 includes a
solenoid actuated spool
or poppet valve. A solenoid 58 of the control device 50a has displaced a spool
or poppet valve 60
to a position in which the actuator 36a is now connected to the lines 48a,b. A
pressure
differential between the lines 48a,b can now be used to displace the piston
42a and actuate the
well tool 32a. The remaining control devices 50b,c prevent actuation of their
associated well
tools 32b,c by isolating the lines 48a,b from the actuators 36b,c.
[0049] The control device 50a responds to current flow through a certain set
of the conductors
52. In this example, conductors 52a,b are connected to the control device 50a.
When current
flows in one direction through the conductors 52a,b, the control device 50a
causes the actuator
36a to be operatively connected to the lines 48a,b, but when current flows in
an opposite
direction through the conductors, the control device causes the actuator to be
operatively isolated
from the lines.
[0050] As depicted in FIG. 3, the other control devices 50b,c are connected to
different sets of
the conductors 52. For example, control device 50b is connected to conductors
52c,d and control
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device 50c is connected to conductors 52e,f.
[00512] When current flows in one direction through the conductors 52c,d, the
control device
50b causes the actuator 36b to be operatively connected to the lines 48a,b,
but when current
flows in an opposite direction through the conductors, the control device
causes the actuator to
be operatively isolated from the lines. Similarly, when current flows in one
direction through the
conductors 52e,f, the control device 50c causes the actuator 36c to be
operatively connected to
the lines 48a,b, but when current flows in an opposite direction through the
conductors, the
control device causes the actuator to be operatively isolated from the lines.
[00523] However, it should be understood that multiple control devices are
preferably, but not
necessarily, connected to each set of conductors. By connecting multiple
control devices to the
same set of conductors, the advantages of a reduced number of conductors can
be obtained, as
explained more fully below.
[00534] The function of selecting a particular well tool 32a-c for actuation
in response to current
flow in a particular direction between certain conductors is provided by
directional elements 62
of the control devices 50a-c. Various different types of directional elements
62 are described
more fully below.
[00545] Referring additionally now to FIG. 4, an example of the system 30 is
representatively
illustrated, in which multiple control devices are connected to each of
multiple sets of
conductors, thereby achieving the desired benefit of a reduced number of
conductors in the well.
In this example, actuation of six well tools may be selectively controlled
using only three
conductors, but, as described herein, any number of conductors and well tools
may be used in
keeping with the principles of this disclosure.
[00556] As depicted in FIG. 4, six control devices 50a-f are illustrated apart
from their respective
well tools. However, it will be appreciated that each of these control devices
50a-f would in
practice be connected between the fluid pressure source 48 and a respective
actuator 36 of a
respective well tool 32 (for example, as described above and depicted in FIGS.
2 & 3).
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[0057] The control devices 50a-f include respective solenoids 58a-f, spool
valves 60a-f and
directional elements 62a-f. In this example, the elements 62a-f are diodes.
Although the
solenoids 58a-f and diodes 62a-f are electrical components, they do not
comprise complex or
unreliable electronic circuitry, and suitable reliable high temperature
solenoids and diodes are
readily available.
[0056] A power supply 64 is used as a source of direct current. The power
supply 64 could also
be a source of alternating current and/or command and control signals, if
desired. However, the
system 30 as depicted in FIG. 4 relies on directional control of current in
the conductors 52 in
order to selectively actuate the well tools 32, so alternating current,
signals, etc. should be
present on the conductors only if such would not interfere with this selection
function. If the
casing string 16 and/or tubing string 20 is used as a conductor in the system
30, then preferably
the power supply 64 comprises a floating power supply.
[0057] The conductors 52 may also be used for telemetry, for example, to
transmit and receive
data and commands between the surface and downhole well tools, actuators,
sensors, etc. This
telemetry can be conveniently transmitted on the same conductors 52 as the
electrical power
supplied by the power supply 64.
[0058] The conductors 52 in this example comprise three conductors 52a-c. The
conductors 52
are also arranged as three sets of conductors 52a,b 52b,c and 52a,c. Each set
of conductors
includes two conductors. Note that a set of conductors can share one or more
individual
conductors with another set of conductors.
[00591] Each conductor set is connected to two control devices. Thus,
conductor set 52a,b is
connected to each of control devices 50a,b, conductor set 52b,c is connected
to each of control
devices 50c,d, and conductor set 52a,c is connected to each of control devices
50e,f.
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[00602] In this example, the tubing string 20 is part of the conductor 52c.
Alternatively, or in
addition, the casing string 16 or any other conductor can be used in keeping
with the principles
of this disclosure.
[00613] It will be appreciated from a careful consideration of the system 30
as depicted in FIG. 4
(including an observation of how the diodes 62a-f are arranged between the
solenoids 58a-f and
the conductors 52a-c) that different current flow directions between different
conductors in the
different sets of conductors can be used to select which of the solenoids 58a-
f are powered to
thereby actuate a respective well tool. For example, current flow from
conductor 52a to
conductor 52b will provide electrical power to solenoid 58a via diode 62a, but
oppositely
directed current flow from conductor 52b to conductor 52a will provide
electrical power to
solenoid 58b via diode 62b. Conversely, diode 62a will prevent solenoid 58a
from being
powered due to current flow from conductor 52b to conductor 52a, and diode 62b
will prevent
solenoid 58b from being powered due to current flow from conductor 52a to
conductor 52b.
[00624] Similarly, current flow from conductor 52b to conductor 52c will
provide electrical
power to solenoid 58c via diode 62c, but oppositely directed current flow from
conductor 52c to
conductor 52b will provide electrical power to solenoid 58d via diode 62d.
Diode 62c will
prevent solenoid 58c from being powered due to current flow from conductor 52c
to conductor
52b, and diode 62d will prevent solenoid 58d from being powered due to current
flow from
conductor 52b to conductor 52c.
[00635] Current flow from conductor 52a to conductor 52c will provide
electrical power to
solenoid 58e via diode 62e, but oppositely directed current flow from
conductor 52c to conductor
52a will provide electrical power to solenoid 58f via diode 62f. Diode 62e
will prevent solenoid
58e from being powered due to current flow from conductor 52c to conductor
52a, and diode 62f
will prevent solenoid 58f from being powered due to current flow from
conductor 52a to
conductor 52c.
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[0064] The direction of current flow between the conductors 52 is controlled
by means of a
switching device 66. The switching device 66 is interconnected between the
power supply 64
and the conductors 52, but the power supply and switching device could be
combined, or could
be part of an overall control system, if desired.
[0065] Examples of different configurations of the switching device 66 are
representatively
illustrated in FIGS. 5 & 6. FIG. 5 depicts an embodiment in which six
independently controlled
switches are used to connect the conductors 52a-c to the two polarities of the
power supply 64.
FIG. 6 depicts an embodiment in which appropriate combinations of switches are
closed to select
a corresponding one of the well tools for actuation. This embodiment might be
implemented, for
example, using a rotary switch. Other implementations (such as using a
programmable logic
controller, etc.) may be utilized as desired.
[00668] Note that multiple well tools 32 may be selected for actuation at the
same time. For
example, multiple similarly configured control devices 50 could be wired in
series or parallel to
the same set of the conductors 52, or control devices connected to different
sets of conductors
could be operated at the same time by flowing current in appropriate
directions through the sets
of conductors.
[006769] In addition, note that fluid pressure to actuate the well tools 32
may be supplied by one
of the lines 48, and another one of the lines (or another flow path, such as
an interior of the
tubing string 20 or the annulus 56) may be used to exhaust fluid from the
actuators 36. An
appropriately configured and connected spool valve can be used, so that the
same one of the lines
48 is used to supply fluid pressure to displace the pistons 42 of the
actuators 36 in each direction.
[00680] Preferably, in each of the above-described embodiments, the fluid
pressure source 48 is
pressurized prior to flowing current through the selected set of conductors 52
to actuate a well
tool 32. In this manner, actuation of the well tool 32 immediately follows the
initiation of current
flow in the set of conductors 52.
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[00691] Referring additionally now to FIG. 7, the system 30 is depicted in a
configuration
similar in most respects to that of FIG. 4. In FIG. 7, however, a voltage
potential is applied
across the conductors 52a, 52c in order to select the control device 50e for
actuation of its
associated well tool 32. Thus, current flows from conductor 52a, through the
directional element
62e, through the solenoid 58e, and then to the conductor 52c, thereby
operating the shuttle valve
60e.
[00702] However, there is another path for current flow between the conductors
52a,c. This
current "sneak" path 70 is indicated by a dashed line in FIG. 7. As will be
appreciated by those
skilled in the art, when a potential is applied across the conductors 52a,c,
current can also flow
through the control devices 50a,c, due to their common connection to the
conductor 52b.
[00713] Since the potential in this case is applied across two solenoids 58a,c
in the sneak path
70, current flow through the control devices 50a,c will be only half of the
current flow through
the control device 50e intended for selection, and so the system 30 is still
operable to select the
control device 50e without also selecting the unintended control devices
50a,c. However,
additional current is flowed through the conductors 52a,c in order to
compensate for the current
lost to the control devices 50a,c, and so it is preferred that current not
flow through any
unintended control devices when an intended control device is selected.
[00724] This is accomplished in various examples described below by preventing
current flow
through each of the control devices 50a-f if a voltage potential applied
across the control device
is less than a minimum level. In each of the examples depicted in FIGS. 8-11
and described more
fully below, under-voltage lockout devices 72a-f prevent current from flowing
through the
respective control devices 50a-f, unless the voltage applied across the
control devices exceeds a
minimum.
[0073] In FIG. 9, each of the lockout devices 72a-f includes a relay 74 and a
resistor 76. Each
relay 74 includes a switch 78 interconnected between the respective control
device 50a-f and the
conductors 52a-c. The resistor 76 is used to set the minimum voltage across
the respective
conductors 52a-c which will cause sufficient current to flow through the
associated relay 74 to
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close the switch 78.
[00746] If at least the minimum voltage does not exist across the two of the
conductors 52a-c to
which the control device 50a-f is connected, the switch 78 will not close.
Thus, current will not
flow through the associated solenoid 58a-f, and the respective one of the
control devices 50a-f
will not be selected.
[00757] As in the example of FIG. 7, sufficient voltage would not exist across
the two
conductors to which each of the lockout devices 72a,c is connected to operate
the relays 74
therein if a voltage is applied across the conductors 52a,c in order to select
the control device
50e. However, sufficient voltage would exist across the conductors 52a,c to
cause the relay 74 of
the lockout device 72e to close the switch 78 therein, thereby selecting the
control device 50e for
actuation of its associated well tool 32.
[0076] In FIG. 9, the lockout devices 72a-f each include the relay 74 and
switch 78, but the
resistor is replaced by a zener diode 80. Unless a sufficient voltage exists
across each zener diode
80, current will not flow through its associated relay 74, and the switch 78
will not close. Thus, a
minimum voltage must be applied across the two conductors 52a-c to which the
respective one
of the control devices 50a-f is connected, in order to close the associated
switch 78 of the
respective lockout device 72a-f and thereby select the control device.
[0077] In FIG. 10, a thyristor 82 (specifically in this example a silicon
controlled rectifier) is
used instead of the relay 74 in each of the lockout devices 72a-f. Other types
of thyristors and
other gating circuit devices (such as TRIAC, GTO, IGCT, SIT/SITh, DB-GTO, MCT,
CSMT,
RCT, BRT, etc.) may be used, if desired. Unless a sufficient voltage exists
across the source and
gate of the thyristor 82, current will not flow to its drain. Thus, a minimum
voltage must be
applied across the two of the conductors 52a-c to which the respective one of
the control devices
50a-f is connected, in order to cause current flow through the thyristor 82 of
the respective
lockout device 72a-f and thereby select the control device. The thyristor 82
will continue to
allow current flow from its source to its drain, as long as the current
remains above a
predetermined level.
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[00780] In FIG. 11, a field effect transistor 84 (specifically in this example
an n-channel
MOSFET) is interconnected between the control device 50a-f and one of the
associated
conductors 52a-c in each of the lockout devices 72a-f. Unless a voltage exists
across the gate and
drain of the transistor 84, current will not flow from its source to its
drain. The voltage does not
exist unless a sufficient voltage exists across the zener diode 80 to cause
current flow through the
diode. Thus, a minimum voltage must be applied across two of the conductors
52a-c to which the
respective one of the control devices 50a-f is connected, in order to cause
current flow through
the transistor 84 of the respective lockout device 72a-f and thereby select
the control device.
[00791] It may now be fully appreciated that the above disclosure provides
several
improvements to the art of selectively actuating downhole well tools. One such
improvement is
the elimination of unnecessary current draw by control devices which are not
intended to be
selected for actuation of their respective well tools.
[00802] The above disclosure provides a system 30 for selectively actuating
from a remote
location multiple downhole well tools 32 in a well. The system 30 includes at
least one control
device 50a-f for each of the well tools 32, such that a particular one of the
well tools 32 can be
actuated when a respective control device 50a-f is selected. Conductors 52 are
connected to the
control devices 50a-f, whereby each of the control devices 50a-f can be
selected by applying a
predetermined voltage potential across a respective predetermined pair of the
conductors 52. At
least one lockout device 72a-f is provided for each of the control devices 50a-
f, whereby the
lockout devices 72a-f prevent current from flowing through the respective
control devices 50a-f
if the voltage potential across the respective predetermined pair of the
conductors 52 is less than
a predetermined minimum.
[0081] Each of the lockout devices 72a-f may include a relay 74 with a switch
78. The relay 74
closes the switch 78, thereby permitting current flow through the respective
control device 50a-f
when the predetermined minimum voltage potential is applied across the lockout
device 72a-f.
[0082] Each of the lockout devices 72a-f may include a thyristor 82. The
thyristor 82 permits
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current flow from its source to is drain, thereby permitting current flow
through the respective
control device 50a-f when the predetermined minimum voltage potential is
applied across the
lockout device 72a-f.
[0083] Each of the lockout devices 72a-f may include a zener diode 80. Current
flows through
the zener diode 80, thereby permitting current flow through the respective
control device 50a-f
when the predetermined minimum voltage potential is applied across the lockout
device 72a-f.
[0084] Each of the lockout devices 72a-f may include a transistor 84. The
transistor 84 permits
current flow from its source to is drain, thereby permitting current flow
through the respective
control device 50a-f when the predetermined minimum voltage potential is
applied across the
lockout device 72a-f.
[00857] Also described above is a method of selectively actuating from a
remote location
multiple downhole well tools 32 in a well. The method includes the steps of:
selecting a first one
of the well tools 32 for actuation by applying a predetermined minimum voltage
potential to a
first set of conductors 52a,c in the well; and preventing actuation of a
second one of the well
tools 32 when the predetermined minimum voltage potential is not applied
across a second set of
conductors in the well 52a,b or 52b,c. At least one of the first set of
conductors 52a,c is the same
as at least one of the second set of conductors 52a,b or 52b,c.
[0086] The selecting step may include permitting current flow through a
control device 50a-f of
the first well tool in response to the predetermined minimum voltage potential
being applied
across a lockout device 72a-f interconnected between the control device 50a-f
and the first set of
conductors 52a,c.
[0087] The current flow permitting step may include actuating a relay 74 of
the lockout device
72a-f to thereby close a switch 78, thereby permitting current flow through
the control device
50a-f when the predetermined minimum voltage potential is applied across the
lockout device
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72a-f.
[00880] The current flow permitting step may include permitting current flow
from a source to a
drain of a thyristor 82 of the lockout device 72a-f, thereby permitting
current flow through the
control device 50a-f when the predetermined minimum voltage potential is
applied across the
lockout device 72a-f.
[00891] The current flow permitting step may include permitting current flow
through a zener
diode 80 of the lockout device 72a-f, thereby permitting current flow through
the control device
50a-f when the predetermined minimum voltage potential is applied across the
lockout device
72a-f.
[00902] The current flow permitting step may include permitting current flow
from a source to a
drain of a transistor 84 of the lockout device 72a-f, thereby permitting
current flow through the
control device 50a-f when the predetermined minimum voltage potential is
applied across the
lockout device 72a-f.
[00913] The above disclosure also describes a system 30 for selectively
actuating from a remote
location multiple downhole well tools 32 in a well, in which the system 30
includes: at least one
control device 50a-f for each of the well tools 32, such that a particular one
of the well tools 32
can be actuated when a respective control device 50a-f is selected; conductors
52 connected to
the control devices 50a-f, whereby each of the control devices 50a-f can be
selected by applying
a predetermined voltage potential across a respective predetermined pair of
the conductors 52;
and at least one lockout device 72a-f for each of the control devices 50a-f,
whereby each lockout
device 72a-f prevents a respective control device 50a-f from being selected if
the voltage
potential across the respective predetermined pair of the conductors 52 is
less than a
predetermined minimum.
[00924] FIG. 12 is a schematic electrical diagram showing details of another
configuration of the
system and method, in which a further configuration of the lockout devices
prevent current sneak
paths in the system. In this example, the system 100 has a DC power supply
110. Alternative
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power supplies are explained above and will be apparent to one of skill in the
art. The power
supply could also be a source of AC and/or command and control signals,
however, the system
as depicted in FIG. 12 relies on directional control of current in order to
selectively actuate the
loads, so alternating current, signals, etc. should be present on the
conductors only if such would
not interfere with this selection function.
[00935] The system utilizes a set of conductors 152 comprising, in this
example, four conductors
152a-d. For example, a three-wire TEC can be utilized, where the three wires
act as conductors
152a-c and the sheath acts as the conductor 152d. It should be understood that
any number of
conductors may be used in keeping with the principles of this disclosure. In
addition, the
conductors 152a-d can be in a variety of forms, such as wires, metal
structures (for example, the
casing or tubing strings 16, 20, etc.), or other types of conductors.
[0094] The exemplary diagram utilizes twelve loads (L), 150a-1, are shown,
each of which is
actuated by a unique application of voltage potential across a pair of
conductors and direct
current in a selected direction. The twelve loads are generically represented
(L) and can be any
device requiring an electrical load to operate. For example, load devices can
include control
devices, actuators for well tools, solenoids and the like, as explained above,
or motors, pumps,
etc. Each load 150a-1 has an associated directional element 162a-1, such as a
diode, to isolate the
loads depending on the direction of current applied.
[00957] As can be seen by inspection, a current flow from the power supply 110
along conductor
152a to 152b will flow along path 171 through directional element 162a and
provide electrical
power to load 150a. Thus, application of a voltage potential across conductors
152a and 152b,
with current supplied in the direction from 152a to 152b, selects load 150a
for operation.
However, there are other paths for current flow between the conductors 152a-b.
These current
"sneak" or "leak" paths are indicated by arrows 170 in FIG. 12. The voltage
potential is applied
across four loads, 150c, e, i and k, in the sneak paths 170. Only half of the
power goes through
the desired path from 152a to 152b, while a quarter of the power goes through
152a to 152c to
152 b, and a quarter from 152a to 152d to 152 b. Half the power is wasted
where the loads
require the full voltage drop to be actuated, such as with solenoids, etc.
This reduces the
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available power to the selected load. The leak path current can also create
problems where the
load which operates on partial power, such as a pump or motor, or where each
load requires
different power levels to operate. It is preferred that current not flow
through any unintended
load devices when an intended load device is selected. Problems are also
encountered in alternate
systems when differing resistances are encountered in the conductors.
[0096] This is accomplished through the use of lock-out devices as described
above. FIG. 13 is a
schematic electrical diagram showing details of another configuration of the
system and method,
in which a further configuration of the lockout devices prevents current sneak
paths in the
system. In FIG. 13, each of the lockout devices 172a-1 includes a silicon
controlled rectifier
(SCR) 182a-1, a type of thyristor, to control current flow through the load
device based on a gate
voltage. Essentially, the SCR blocks current until the voltage to the gate
reaches a known critical
level. At that point, current is allowed to flow from a selected conductor to
another selected
conductor in a selected direction. Furthermore, current will continue to flow
regardless of the
gate voltage until the current is dropped to zero or below a holding current
value.
[0097] Each lockout device 172 includes resistors 176a-1 and gate 174a-1. The
resistors 176 are
used to set the minimum voltage across the respective conductors 152a-d which
will cause
sufficient current to flow through the associated gate 174 to close the SCR
172. Then current is
allowed to flow through the SCR and the load device. When power is initially
applied, current
will flow through each resistor in the network, along the selected path and
leak paths. However,
twice as much current will go through the resistors 176a in the desired path
than through the
resistors 176c, e, i and k, along the leak paths 170. Once the current is
sufficient to create
sufficient voltage at the gate 174a, the SCR 172a will "turn on." Once
activated, the SCR will act
as a short and allow full power to go through load device 150a. At this point,
the system voltage
will drop to that required by the load device and very little current will be
routed through the
resistors 176a.
[0098] The arrangement described increases the available power since little
power is lost to the
leak paths. Further, the system allows loads that operate at partial power
since only the selected
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load device receives power. The system reduces problems with varying
resistance in the
conductors. Finally, the system allows for multiple types and loads downhole.
[00991] FIG. 14 is a schematic electrical diagram showing details of another
configuration of
the system and method utilizing SCRs. SCRs can also be used without a specific
gate voltage by
exceeding their breakdown voltage in the forward biased direction. After the
breakdown voltage
is exceeded, the SCR acts as if the gate voltage had been applied. SCRs 172a-1
are seen on an
electrical diagram otherwise similar to that of FIG. 13. The SCR can be "re-
set" by elimination
or reduction of the current through the system.
[01002] FIG. 15 is a schematic electrical diagram showing details of another
configuration of the
system and method for controlling bidirectional load devices, such as motors.
FIG. 15 shows an
electrical diagram similar to that of FIG. 14, having a system 100 with
conductors 152a-d and
power supply 110. Here the four conductors are utilized to selectively operate
six bidirectional
load devices 182a-f, such as bidirectional DC motors, M. It is understood that
other bidirectional
load devices can be substituted or similarly used, such as pumps, motion
controllers, etc. In this
system, the direction of current across a conductor pair correlates to the
direction of the
bidirectional device, forward or backward. For use with bidirectional load
devices, SCRs 172a-1
are used in parallel in pairs for each bidirectional load device 182a-f
(SCRs172a-b for load
device 182a; SCRs 172c-d for load device 182b, etc.). This allows each
bidirectional load device
to be run forward or backward using the same set of conductors. Resistors 176a-
1 are employed
as discussed above with respect to FIG. 13.
[0101] As before, the SCRs can be used without the resistors by simply
exceeding the
breakdown voltage of the SCRs.
[01024] FIG. 16 is a schematic electrical diagram showing details of another
configuration of the
system and method utilizing alternate lock-out devices. In FIGS. 13-15 above,
SCRs are a
preferred type of thyristor or gated lockout device. Other types of thyristors
and/or other gating
circuit devices (such as TRIAC, GTO, IGCT, SIT/SITh, DB-GTO, MCT, CSMT, RCT,
BRT,
DIAC, diactor, SIDAC, etc.) may be used. FIG. 16 shows a diagram for operating
multiple
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downhole bidirectional load devices 182a-f, such as motors, M. A DIAC 184a-f
is arranged in
series with a corresponding bidirectional load device 182a-f, as shown. SIDACs
can be used
in place of the DIAC devices. The DIAC is bidirectional, allowing it to be
used with
bidirectional load devices. The DIAC allows current flow only after its
breakdown voltage
has been reached. After the breakdown voltage is reached, current continues to
flow through
the DIAC until the current is reduced to zero or below a holding current
value. The diagram is
similar to that seen in FIG. 15 and will not be described in great detail
here.
[01035] Although in the preferred embodiments described herein a single type
of lockout
device is utilized in any single embodiment, it is understood that multiple
types of lockout
devices can be utilized in a single system.
101046] The scope of the claims should not be limited by the preferred
embodiments set forth
in the examples, but should be given the broadest interpretation consistent
with the
description as a whole.
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