[0001] The present invention relates generally to methods and apparatus utilized in conjunction
with subterranean wells and, in an embodiment described herein, more particularly
provides a compact electrohydraulic actuation system for downhole tools used in subterranean
wells.
[0002] It would be desirable to be able to operate selected ones of multiple hydraulically
actuated well tools installed in a well. However, it is uneconomical and practically
unfeasible to run separate hydraulic control lines from the surface to each one of
numerous well tool assemblies. Instead, the number of control lines extending relatively
long distances should be minimized as much as possible. Additionally, it would be
desirable to effect the operation of multiple hydraulically actuated well tools with
a relatively low power consumption control system.
[0003] Therefore, it would be highly advantageous to provide a hydraulically-based control
system and associated control methods which reduce the number of control lines extending
relatively long distances between multiple hydraulically actuated well tools and the
surface. The control system would preferably permit individual ones of the well tools
to be selected for actuation as desired, and the selection of well tools should be
convenient and reliable.
[0004] EP 0898084 describes a hydraulic pressure pilot circuit for a hydraulic excavator.
[0005] US 2240901 describes a hydraulic transmission for an oil well.
[0006] In carrying out the principles of the present invention, in accordance with an embodiment
thereof, a compact hydraulic actuator and associated methods are provided which solve
the above problem in the art.
[0007] The present invention provides actuator apparatus as recited in the appended independent
claim 1.
[0008] Further features of the present invention are provided as recited in any of the appended
dependent claims.
[0009] Described herein is a downhole well tool assembly, representatively a flow control
device in the form of a variable inlet choke device, which is controlled using a fluid
power source connected thereto and which includes a first source of pressurized fluid
operable to power the downhole well tool assembly via a first fluid circuit portion
connectable to the downhole well tool assembly, and a second source of pressurized
fluid having a second fluid circuit portion interposed in the first fluid circuit
portion, the second source of pressurized fluid being operable to selectively alter
the routing of pressurized fluid to the downhole well tool assembly. The fluid power
source is preferably disposed entirely downhole, and is electrically operable.
[0010] In an illustrated embodiment of the actuator, the first source of pressurized fluid
includes a reciprocating hydraulic primary pump which is coupled to the well tool
assembly by the first circuit portion, and has a reversible electric drive motor.
Check valves interposed in the first circuit portion the primary pump a double pumping
action. The second source of pressurized fluid includes a reciprocating hydraulic
switching pump used to control fluid pressure operable pilot check valves in the second
fluid circuit portion and in a manner selectively reversing the fluid supply and return
flow directions to the controlled well tool assembly via the first fluid circuit portion.
[0011] In the illustrated embodiment of the actuator, the actuator construction includes
a body having first and second bores extending therethrough, the first and second
bores respectively having radially enlarged first and second cylinder portions with
opposite ends. First and second rods are reciprocably disposed in the first and second
bores and have radially enlarged piston portions slidably received in the first and
second cylinder portions and dividing each of them into opposing first and second
hydraulic chambers that may be coupled to fluid circuitry. First and second drive
portions extend outwardly from the body and have reversible electric motors respectively
coupled to the first and second rods, to reciprocate them in the first and second
body bores, via gearing and ball screw structures.
[0012] Also described herein is a pilot check valve, which is carried in the first bore
and is connectable to the first fluid circuit portion, the pilot check valve being
selectively engageable ay an end portion of the first rod to disable the fluid flow
blocking function of the pilot check valve.
[0013] Also described herein is a first accumulator, which is communicated with the first
fluid circuit portion, is chargeable by the first source of fluid pressure, and is
selectively communicatable with the controlled well tool assembly to rapidly open
or close a control drive portion thereof. A second, smaller accumulator is preferably
interconnected between the first accumulator and the first fluid circuit portion,
and functions to maintain a minimum fluid pressure in the first fluid circuit portion.
[0014] A well completion is provided in the wellbore of which are provided a spaced series
of downhole well tool assemblies which are representatively flow control devices in
the form of variable fluid chokes. Each flow control device is operatively connected
to one of the downhole hydraulic actuators, and, a control system is used to sense
the magnitudes of predetermined operational parameters of the chokes and responsively
control the operation of their associated first and second sources of pressurized
fluid in a manner maintaining the magnitudes of the sensed operational parameters
at predetermined levels.
[0015] Representatively, the sensed operational parameters are fluid pressure drops across
the variable inlet opening areas of the chokes. In various representative embodiments
of this control method, the control system is operative to maintain predetermined
minimum fluid pressure drops across the inlet opening area, representatively by maintaining
predetermined minimum positive exterior-to-interior fluid pressure drops across the
inlet opening areas.
[0016] Described below is apparatus for controlling operation of a downhole well tool assembly,
comprising:
a fluid power source including:
a first source of pressurized fluid operable to power the downhole well tool assembly
via a first fluid circuit portion connectable to the downhole well tool assembly,
and
a second source of pressurized fluid having a second fluid circuit portion interposed
in the first fluid circuit portion, the second source of pressurized fluid being operable
to selectively alter the routing of pressurized fluid to the downhole well tool assembly.
[0017] The fluid power source may be a self-contained, closed circuit fluid power source
positionable downhole with the well tool assembly. The first and second sources of
pressurized fluid are preferably electrically operable. Also, the first source of
pressurized fluid ideally includes a reciprocating hydraulic pump having a reversible
electric drive motor. Furthermore, the first fluid circuit portion may include check
valve apparatus interposed therein and may operate to provide the hydraulic pump with
a double pumping action.
[0018] The second source of pressurized fluid may include a reciprocating hydraulic pump
having a reversible drive motor. The second fluid circuit portion may include a plurality
of pilot check valves connected to receive fluid pilot pressure from the hydraulic
pump. Also, the apparatus may further comprise a pressurized fluid accumulator communicated
with the first fluid circuit portion and selectively operable to power the downhole
well tool assembly via the first fluid circuit portion. The pressurized fluid accumulator
may be selectively chargeable by the first source of pressurized fluid. The pressurized
fluid accumulator may be a first fluid pressure accumulator, and the apparatus may
further comprise a second fluid pressure accumulator in fluid pressure communication
with the first accumulator and the first fluid circuit portion, the second accumulator
being operative to maintain a predetermined minimum fluid pressure in the first fluid
circuit portion.
[0019] The apparatus further comprises control apparatus for sensing the magnitude of a
predetermined operational parameter of the well tool assembly and responsively controlling
the operation of the first and second sources of pressurized fluid in a manner maintaining
the magnitude of the sensed operational parameter at a predetermined level.
[0020] The first and second sources of pressurized fluid are ideally electrically operable,
and the apparatus may further comprise an electrical power source operably connectable
to the first and second sources of pressurized fluid.
[0021] The electrical power source may be a self-contained power source positionable entirely
downhole.
[0022] Also described below is a method of controlling operation of a downhole well tool
assembly, the method comprising the steps of:
connecting to the well tool assembly a fluid power source including a first source
of pressurized fluid operable to power the downhole well tool assembly via a first
fluid circuit portion connected thereto, and a second source of pressurized fluid
having a second fluid circuit portion interposed in the first fluid circuit portion,
the second source of pressurized fluid being operable to selectively alter the routing
of pressurized fluid to the downhole well tool assembly; and operating the first and
second sources of pressurized fluid.
[0023] The connecting step may include the step of positioning the fluid power source entirely
downhole.
[0024] The well tool assembly may be carried on a tubular downhole structure, and the connecting
step may include the step of mounting the fluid power source on the tubular downhole
structure adjacent the well tool assembly.
[0025] The operating step is ideally performed by electrically operating the first and second
sources of pressurized fluid.
[0026] Also, the method may further comprise the steps of:
sensing the magnitude of a predetermined operational parameter of the well tool assembly,
and responsively controlling the operation of the first and second sources of pressurized
fluid in a manner maintaining a predetermined magnitude of the sensed operational
parameter.
[0027] The connecting step may include the steps of:
connecting a reciprocating hydraulic primary pump to the first fluid circuit portion,
and connecting a reciprocating hydraulic switching pump to the second fluid circuit
portion.
[0028] Furthermore, the connecting step may further comprise the steps of:
interposing a plurality of pilot check valves in the first fluid circuit portion,
and connecting the switching pump to the pilot check valves.
[0029] Ideally, the connecting step further comprises connecting an accumulator in the first
fluid circuit, and
the method further comprises the step of using the first source of pressurized fluid
to charge the accumulator.
[0030] The method may also further comprise the step of:
utilizing a selectively variable one of the first source of pressurized fluid and
the charged accumulator to power the downhole well tool assembly.
[0031] A subterranean well completion is described below as comprising:
a wellbore;
a series of well tool assemblies disposed in the wellbore;
multiple self-contained, electrically operable hydraulic pressure sources interconnected
to corresponding ones of the well tool assemblies and useable to control their operation,
each self-contained hydraulic pressure source being disposed downhole and including
a first source of pressurized fluid operable to power the associated downhole well
tool assembly via a first fluid circuit portion connected thereto, and a second source
of pressurized fluid interposed in the first fluid circuit portion, the second source
of pressurized fluid being operable to selectively alter the routing of pressurized
fluid to the associated downhole well tool assembly; and
at least one source of electrical power operably coupled to the hydraulic pressure
sources.
[0032] The electrically operable hydraulic pressure sources are preferably free from physical
extensions thereof to the surface.
[0033] Each source of electrical power may be positioned downhole and may be free from physical
extensions thereof to the surface.
[0034] Each first source of pressurized fluid may include a reciprocating hydraulic pump
having a reversible electric motor.
[0035] Each first fluid circuit portion includes check valve apparatus interposed therein
and operative to provide its associated hydraulic pump with a double pumping action.
[0036] Each second source of pressurized fluid includes a reciprocating hydraulic pump having
a reversible drive motor.
[0037] Each second fluid circuit portion may include a plurality of pilot check valves connected
to receive fluid pilot pressure from the associated hydraulic pump.
[0038] The subterranean well completion may further comprising, for each hydraulic pressure
source, a pressurized fluid accumulator communicated with the first fluid circuit
portion and selectively operable to power the associated downhole well tool assembly
via the first fluid circuit portion.
[0039] For each hydraulic pressure source, the pressurized fluid accumulator may be selectively
chargeable by the first source of pressurized fluid.
[0040] Also for each hydraulic pressure source, the pressurized fluid accumulator may be
a first fluid pressure accumulator, and
the subterranean well completion further comprises, for each hydraulic pressure source,
a second fluid pressure accumulator in fluid pressure communication with the first
accumulator and the first fluid circuit portion, the second accumulator being operative
to maintain a predetermined minimum fluid pressure in the first fluid circuit portion.
[0041] The subterranean well completion may further comprise control apparatus for sensing
the magnitudes of predetermined operational parameters of the well tool assemblies
and responsively controlling the operation of their associated first and second sources
of pressurized fluid in a manner maintaining the magnitudes of the sensed operational
parameters at predetermined levels.
[0042] The downhole well tool assemblies are flow control devices mutually spaced apart
along the length of the wellbore and having variable opening areas communicating exterior
and interior portions thereof, and
the sensed operational parameters may be fluid pressure drops across the inlet opening
areas.
[0043] The flow control devices may be variable choke devices.
[0044] The control apparatus may be operative to maintain predetermined minimum fluid pressure
drops across the inlet opening areas.
[0045] The control apparatus may be operative to maintain minimum positive exterior-to-interior
fluid pressure drops across the inlet opening areas.
[0046] The control apparatus may be operative to maintain substantially equal pressure drops
across the inlet opening areas.
[0047] Furthermore, a method of controlling operation of multiple well tool assemblies positioned
downhole in the wellbore of a subterranean well is described below, the method comprising
the steps of:
interconnecting multiple self-contained, electrically operable hydraulic pressure
sources to corresponding ones of the well tool assemblies, each self-contained hydraulic
pressure source being disposed downhole and including a first source of pressurized
fluid operable to power the associated downhole well tool assembly via a first fluid
circuit portion connected thereto, and a second source of pressurized fluid interposed
in the first fluid circuit portion and being operable to selectively alter the routing
of pressurized fluid to the associated downhole well tool assembly; and
supplying electrical power to the hydraulic pressure sources.
[0048] The method may further comprise the step of controlling the operation of the downhole
well tool assemblies by sensing the magnitudes of predetermined operational parameters
thereof and responsively controlling the operation of their associated first and second
sources of pressurized fluid in a manner maintaining the magnitudes of the sensed
operational parameters at predetermined levels.
[0049] The downhole well tool assemblies may be flow control devices mutually spaced apart
along the length of the wellbore and having variable opening areas communicating exterior
and interior portions thereof, and
the sensing step may be performed by sensing fluid pressure drops across the inlet
opening areas.
[0050] The controlling step may be performed in a manner maintaining predetermined minimum
fluid pressure drops across the inlet opening areas.
[0051] The controlling step may be performed in a manner maintaining minimum positive exterior-to-interior
fluid pressure drops across the inlet opening areas.
[0052] The controlling step may be performed in a manner maintaining substantially equal
pressure drops across the inlet opening areas.
[0053] The invention will now be further described with reference to the drawings, in which:
FIG. 1 is a highly schematic cross-sectional view through a portion of a subterranean
well completion in which a series of well tool assemblies, representatively flow control
devices, are disposed and operated by specially designed electrohydraulic actuators
embodying principles of the present invention;
FIG. 2 is a schematic circuit diagram of one of the actuators;
FIG. 3 a schematic control diagram for a representative one of the actuators; and
FIG. 4 is a highly schematic cross-sectional view through a portion of an alternate
embodiment of the subterranean well completion shown in FIG. 1.
[0054] Representatively and schematically illustrated in FIG. 1 is a downhole portion of
a subterranean well completion 10 which embodies principles of the present invention.
In the following description of the well completion 10 and other apparatus and methods
described herein, directional terms, such as "above", "below", "upper", "lower", etc.,
are used only for convenience in referring to the accompanying drawings. Additionally,
it is to be understood that the various embodiments of the present invention 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 invention.
[0055] The portion of the well completion 10 schematically illustrated in FIG. 1 representatively
includes a generally vertical cased and cemented-in wellbore 12 which illustratively
intersects three spaced apart subterranean production formations or zones 14, 16 and
18, with the usual wellbore perforations 20 communicating the production zones 14,
16 and 18 with the interior of the wellbore. Production tubing 22 is extended through
the wellbore 12 and forms therewith an annular space 24. Annular packers 26, 28 and
30 are used to sealingly divide the annular space 24 into longitudinal segments 24a,24b,
and 24c that are respectively communicated with the production zones 14, 16 and 18
via the various wellbore perforations 20.
[0056] While the apparatus and methods of the present invention described herein will be
described in conjunction with the representatively vertical, cased wellbore 12 it
is to be clearly understood that methods and apparatus embodying principles of the
present invention may be utilized in other environments, such as horizontal or inclined
wellbore portions, uncased wellbore portions, etc. Furthermore, the apparatus and
methods of the present invention will be representatively described herein in terms
of producing fluid from the well, but such apparatus and methods can also be utilized
in injection operations without departing from principles of the present invention.
As used herein, the term "wellbore" is intended to include both cased and uncased
wellbores.
[0057] Still referring to FIG. 1, a plurality of well tool assemblies 32a, 32b and 32c,
representatively hydraulically operable variable flow choke devices, are operatively
installed in the production tubing 22, with the choke 32a being disposed between the
packers 26,28 and associated with the production zone 14, the choke 32b being disposed
between the packers 28,30 and associated with the production zone 16, and the choke
32c being positioned below the packer 30 and associated with the production zone 18.
The chokes 32a-32c are of conventional construction, with each of them having a schematically
depicted inlet opening area 34 through which production fluid entering its associated
wellbore annulus portion may inwardly flow for upward transport to the surface via
the interior of the production tubing 22. While three chokes 32a-32c have been representatively
illustrated herein, it will be readily appreciated that a greater or lesser number
of such chokes could be incorporated in the well completion 10 without departing from
principles of the present invention.
[0058] One of the variable chokes, representatively choke 32a, is schematically depicted
in FIG. 2 and has a hydraulically operable drive portion 36 that is operable in a
known manner to selectively vary the inlet opening area 34 of the choke. The drive
portion 36 illustratively includes a hollow cylindrical body 38 through the opposite
ends of which a rod 40 slidingly and sealingly passes. Rod 40 has a radially enlarged
central portion which defines a piston 42 that slidingly and sealingly engages the
interior side surface of the body 38, is axially reciprocable therein, and divides
the interior of the body 38 into opposite right and left chambers 44 and 46.
[0059] When the hydraulic pressure in chamber 44 is greater than that in chamber 46, the
rod and piston structure 40,42 is shifted leftwardly relative to the body 38 to increase
the opening area 34 of choke 32a. Conversely, when the hydraulic pressure in chamber
46 is greater than that in chamber 44, the rod and piston structure 40,42 is shifted
rightwardly relative to the body 38 to decrease the opening area 34 of choke 32a.
As schematically depicted in FIG. 1, each of the chokes 32a,32b,32c has a position
sensing section 48 operable to output a control signal indicative of the position
of the rod and piston structure 42, and therefore indicative of the degree to which
its associated choke is open or closed to fluid inflow. For purposes later described
herein, the production tubing 22 (see FIG. 2), adjacent each of the variable chokes
32a,32b,32c, has associated therewith exterior and interior pressure sensors 50,52
which respectively monitor the fluid pressure exterior to the production tubing 22
and the pressure within the production tubing 22 and generate a combinative signal
indicative of the pressure drop across the inlet opening area 34 of their associated
choke 32.
[0060] According to a key aspect of the present invention, each of the chokes 32a,32b,32c
is controlled by a specially designed low power miniature hydraulic actuator 54 (see
FIG. 1) which is positioned downhole adjacent its associated choke and is electrically
operable at a low peak wattage which is illustratively in the range of about 5-10
watts. One of the actuators 54, representatively the one associated with the choke
32a, will now be described with reference to FIG. 2.
[0061] Each actuator 54 includes an overall fluid power source that illustratively comprises
a generally rectangularly shaped metal body 56 which carries a first fluid pressure
source, representatively in the form of an electrically operable reciprocating hydraulic
primary pump 58, and a second fluid pressure source, representatively in the form
of an electrically operable reciprocating hydraulic switching pump 60.
[0062] Pump 58 includes a cylinder structure 62 defined by a radially enlarged portion of
a circular bore 64 extending inwardly through the left end of the body 56, the cylinder
62 having left and right ends 66,68 and slidingly and sealingly receiving an enlarged
central piston portion 70 of a rod 72 reciprocably received in the bore 64. Piston
70 divides the interior of the cylinder 62 into left and right opposing chambers 74
and 76, and a left end portion of the rod 72 projects outwardly through the left end
of the body 56 into a cylindrical housing structure 78.
[0063] At the left end of the housing structure 78 is a reversible electric motor 80 which
is drivingly connected, via a gear train 82, to a schematically depicted ball screw
84 which, in turn, is drivingly connected to the rod 72. Motor 80 is connected, via
leads 86 and 88, to an electrical power source which, as schematically depicted in
FIG. 1, is representatively disposed on the surface and extended downhole via an electrical
cable 90. Alternately, the electrical power source may be disposed downhole (as schematically
depicted in FIG. 4) in the form of, for example, one or more batteries 92 or another
type of self-contained downhole electrical power source well known in this particular
art.
[0064] A first fluid circuit portion is interconnected between the primary pump 58 and the
choke drive portion 36 and includes hydraulic lines 94-99 which are interconnected
as schematically shown in FIG. 2. Four check valves 100,102,104,106 are respectively
interposed as shown in the hydraulic lines 94-97, with each of these four check valves
permitting fluid flow therethrough only in the direction indicated by the flow arrow
adjacent such valve.
[0065] For purposes later described herein, a main fluid pressure accumulator 108 and a
smaller auxiliary fluid pressure accumulator 110 are incorporated in the actuator
54. Accumulator 108 has a piston 112 slidingly and sealingly disposed therein and
dividing the interior of the accumulator 108 into opposing left and right chambers
114 and 116. A coiled compression spring 118 disposed in the chamber 116 resiliently
biases the piston 112 toward the left end of the accumulator 108. The smaller auxiliary
accumulator 110 is of a similar construction, having a piston 120 slidingly and sealingly
disposed therein and dividing the interior of the accumulator 110 into opposing top
and bottom chambers 122 and 124. A coiled compression spring 126 resiliently biases
the piston 120 toward the upper end of the accumulator 110.
[0066] Chamber 114 of the accumulator 108 is communicated with the right end of the body
bore 64 by a hydraulic line 128, and the chamber 116 of the accumulator 108 is communicated
with the hydraulic line 97, and with the chamber 122 of the accumulator 110, by a
hydraulic line 130. For purposes later described herein, a mechanically operable pilot
check valve 132 is disposed within the body bore 64 and is coupled between the hydraulic
lines 95a and 128 as indicated. Under normal operation thereof the check valve 132
is open to flow therethrough from the line 95a to the line 128 (as indicated by the
flow arrow adjacent the valve 132) but blocks flow therethrough from the line 128
to the line 95a. However, when a mechanical pilot force is exerted on the left end
of the valve 132, its flow blocking function is disabled to permit fluid flow in either
direction therethrough. This mechanical pilot force may be applied to the valve 132
by a reduced diameter right end portion 134 of the rod 72 which forcibly contacts
the left end of the valve 132 when the primary pump piston 70 is stroked clear to
the right or distal end 68 of the cylinder 62 as later described herein.
[0067] The switching pump 60 includes a cylinder structure 136 defined by a radially enlarged
portion of a circular bore 138 extending inwardly through the left end of the body
56, the cylinder 136 having left and right ends 140,142 and slidingly and sealingly
receiving an enlarged central piston portion 144 of a rod 146 reciprocably received
in the bore 138. Piston 144 divides the interior of the cylinder 136 into left and
right opposing chambers 148 and 150, and a left end portion of the rod 146 projects
outwardly through the left end of the body 56 into a cylindrical housing structure
152.
[0068] At the left end of the housing structure 152 is a reversible electric motor 154 which
is drivingly connected, via a gear train 156, to a schematically depicted ball screw
158 which, in turn, is drivingly connected to the rod 146. Motor 154 is connected,
via leads 160 and 162, to the previously mentioned electrical power source.
[0069] A second fluid circuit portion is interposed in the previously described first fluid
circuit portion 94-99 and is operable as later described herein to selectively alter
the routing of pressurized hydraulic fluid to the choke drive portion 36. This second
fluid circuit portion comprises four fluid pressure operated pilot check valves 164,166,168,170
and hydraulic lines 172-177 which are connected to the pump 60, the pilot check valves
164,166,168 and 170, and the first fluid circuit hydraulic lines 95,97,98 and 99 as
schematically depicted in FIG. 2.
[0070] Each of the pilot check valves 164,166,168 and 170 is normally operable to permit
fluid flow therethrough in the single direction indicated by the flow arrow adjacent
the valve, but to block fluid flow in the reverse direction therethrough. However,
when pilot fluid pressure is exerted on the right end of any of the check valves 164,166,168
and 170, its flow blocking function is disabled, and fluid may flow therethrough in
either direction.
[0071] The switching pump 60 and its associated second fluid circuit portion just described
provides the overall hydraulic circuitry of the actuator 54 with a mechanical switching
logic that permits various control manipulations of the choke drive portion 36 to
be carried out by selectively controlling the pilot check valves 164,166,168 and 170
to variably route pressurized hydraulic fluid to and from the chambers 44 and 46 of
the choke drive portion 36.
[0072] Switching pump 60 may be controlled to position its piston 144 in a selected one
of three positions within its cylinder 136 - (1) a centered position (shown in FIG.
2) in which all of the pilot check valves 164,166,168 and 170 are operative to permit
fluid flow leftwardly therethrough, but block fluid flow rightwardly therethrough;
(2) a rightwardly shifted position in which pilot fluid pressure from the right cylinder
chamber 150 is transmitted via hydraulic line 172 to the right ends of the check valves
164 and 170 to disable their fluid flow blocking functions and thereby permit both
leftward and rightward fluid flow therethrough while the check valves 166,168 continue
to preclude rightward fluid flow therethrough; and (3) a leftwardly shifted position
in which pilot fluid pressure from the left cylinder chamber 148 is transmitted via
hydraulic line 173 to the right ends of the check valves 166,168 to disable their
fluid flow blocking functions and thereby permit both leftward and rightward fluid
flow therethrough while the check valves 164,170 continue to preclude rightward fluid
flow therethrough.
[0073] During normal operation of the primary hydraulic pump 58 its electric motor 80 is
cyclically reversed to cause reciprocation of the piston 70 within its cylinder 62
between left and right limit positions inwardly offset from the opposite ends 66,68
of the cylinder 62. During this normal reciprocating operation of the primary hydraulic
pump 58, the piston 70 does not reach the right or distal end of the cylinder 62.
Accordingly, the pilot check valve 132 is not forcibly contacted by the right end
portion 134 of the rod 72 and thus continues to block fluid flow leftwardly therethrough.
[0074] To move the choke drive piston 42 in a leftward opening direction, the switching
pump piston 144 is driven rightwardly from its centered position within the cylinder
136 to pressurize line 172 and disable the fluid blocking functions of the pilot check
valves 164 and 170, and the main pump piston 70 is caused to reciprocably stroke in
its normal pumping mode. On each rightward stroke of the main pump piston 70, an incremental
amount of pressurized hydraulic fluid is forced into the choke drive portion chamber
44 from the primary pump chamber 76 sequentially through the lines 95 and 174, the
pilot check valve 164, and the line 98. With the accumulator 108 being previously
charged in a manner later described herein, pressurized hydraulic fluid in the accumulator
chamber 114 is communicated (via line 128) with the right end of the bore 64 to thereby
prevent rightward flow of fluid through the pilot check valve 132.
[0075] Entry of pressurized hydraulic fluid into the choke drive portion chamber 44 drives
the piston 42 leftwardly a small distance within the body 38 and forcibly returns
a corresponding incremental volume of hydraulic fluid from the choke drive portion
chamber 46 into the left chamber 74 of the primary pump 58 sequentially through lines
99 and 177, pilot check valve 170, and lines 176, 97, 96 and 94. The presence of the
four check valves 100,102,104,106 in the hydraulic circuitry of the actuator 54 provides
the primary pump 58 with a double pumping action such that when the primary pump piston
70 is subsequently stroked in a leftward direction within the cylinder 62 another
incremental volume of pressurized hydraulic fluid is forced into the choke drive portion
chamber 44 - this time from the left cylinder chamber 74 sequentially through lines
94, 95 and 174, pilot check valve 164, and line 98. The resulting leftward incremental
movement of the choke drive portion piston 42 forcibly returns a corresponding volume
of hydraulic fluid to the right main pump chamber 76 sequentially through lines 99
and 177, the pilot check valve 170, and the lines 176, 97 and 95.
[0076] To move the choke drive portion piston 42 in a rightward closing direction, the primary
pump 58 is operated in its normal reciprocating pumping mode with the switching pump
piston 144 leftwardly shifted from its center position to thereby pressurize line
173 and disable the fluid blocking function of the pilot check valves 166 and 168.
During a rightward stroke of the primary pump piston 70, an incremental volume of
pressurized hydraulic fluid is forced into the left choke drive portion chamber 46
from the primary pump chamber 76 sequentially through lines 95 and 174, pilot check
valve 166 and line 199. The resulting rightward incremental movement of the choke
drive portion piston 42 forcibly returns a corresponding volume of hydraulic fluid
to the left primary pump chamber 74 sequentially via lines 98 and 175, pilot check
valve 168, and lines 176, 97, 96 and 94.
[0077] During the subsequent leftward stroke of the primary pump piston 70, an incremental
amount of pressurized hydraulic fluid is forced into the left choke drive portion
chamber 46 from the left main pump chamber 74 sequentially through lines 94, 95 and
174, the pilot check valve 166 and the line 99. The resulting rightward incremental
movement of the piston 42 forcibly returns a corresponding incremental volume of hydraulic
fluid from the right choke drive portion chamber 44 to the right primary pump chamber
76 sequentially through the lines 98 and 175, the pilot check valve 168, and lines
176, 97 and 94. As will be appreciated, the total opening or closing distance that
the choke drive portion piston 42 is moved corresponds (for a given piston stroke
distance) to the total number of pumping strokes imparted to the primary pump piston
70 by its associated reversible electrical drive motor 80.
[0078] As just described, the choke drive portion piston 42 may be incrementally driven
by the electrohydraulic actuator 54 leftwardly or rightwardly to progressively (and
rather slowly) increase or decrease the inlet opening area 34 of its associated variable
choke 32a (see FIG. 1). Additionally, in a manner which will now be described with
continuing reference to FIG. 2, the accumulator 108 may be selectively utilized to
effect a rapid total opening or total closing of the variable choke 32a if conditions
warrant.
[0079] To ready the accumulator 108 for its rapid choke opening and closing functions, it
is first charged by reciprocating the main pump piston 70 in its normal pumping mode
while the switching pump piston 144 is in its centered position in which all four
of the pilot check valves 164,166,168 and 170 block rightward fluid flow therethrough.
This reciprocation of the primary pump piston 70 pressurizes the chamber 114 of the
accumulator 108, via lines 94, 95 and 95a, the pilot check valve 132, and the line
128, and correspondingly compresses the accumulator spring 118. This pressurization
of the accumulator chamber 114 also serves to pressurize the chamber 122 of the smaller
auxiliary accumulator 110 and compress its spring 126. The charged auxiliary accumulator
110 functions, via its connection to line 97, to maintain a predetermined minimum
pressure in the first fluid circuit portion of the actuator 54.
[0080] When it is desired to relatively rapidly open the choke 32a, the switching pump piston
144 is moved rightwardly away from its centered position to thereby pressurize line
172 and disable the fluid blocking functions of pilot check valves 164 and 170. The
main pump piston 70 is then stroked to its distal or rightmost limit position which
causes the right end portion 134 of the rod 72 to forcibly engage the pilot check
valve 132 and disable its fluid blocking function. This causes pressurized hydraulic
fluid in the accumulator chamber 114 to be flowed into the right choke drive portion
chamber 44 (sequentially via line 128, pilot check valve 132, lines 95a, 95 and 174,
pilot check valve 164 and line 98) to relatively rapidly drive the piston 42 leftwardly
and fully open the choke 32a.
[0081] When it is desired to relatively rapidly close the choke 32a, the switching pump
piston 144 is moved leftwardly away from its centered position to thereby pressurize
line 173 and disable the fluid blocking functions of pilot check valves 166 and 168.
The main pump piston 70 is then stroked to its distal or rightmost limit position
which causes the right end portion 134 of the rod 72 to forcibly engage the pilot
check valve 132 and disable its fluid blocking function. This causes pressurized hydraulic
fluid in the accumulator chamber 114 to be flowed into the left choke drive portion
chamber 46 (sequentially via lines 128, pilot check valve 132, lines 95a, 95 and 174,
pilot check valve 166 and line 99) to relatively rapidly drive the piston 42 rightwardly
and fully close the choke 32a.
[0082] Turning now to FIG. 3, at each variable choke 32 (or other well tool assembly as
the case may be), the actuator 54 with its source of fluid pressure 58 and its pressurized
fluid routing system 178 (representatively the switching pump 60 and its associated
pilot check valves and hydraulic circuitry) are powered by a source of electrical
power such as via the electrical cable 90 connected to a surface electrical power
source, and are incorporated in a control system 180 used to monitor and responsively
control the operation of the variable choke 32 with which it is associated.
[0083] A suitable electronic controller 182 is incorporated into the control system 180,
and is utilized to control an operating parameter of its associated variable choke
32, representatively the outside-to-inside fluid pressure drop (as sensed by the exterior
and interior pressure sensors 50,52 shown in FIG. 2) at the production tubing 22 adjacent
the choke. In this manner, with a control system 180 operatively associated with each
of the chokes 32a-32c, the fluid pressure drop at each choke may be controlled to
provide a variety of production operational characteristics, such as assuring that
a minimum positive exterior-to-interior pressure drop exists at each variable choke
(to prevent unwanted zone-to-zone fluid transfer), maintaining essentially identical
fluid pressure drops at each choke, etc.
[0084] As schematically indicated in FIG. 3, a desired choke operating parameter value signal
184 (such as a desired minimum fluid pressure drop across the choke) is appropriately
input to the controller 182 which also respectively receives operational feedback
signals 186,188,190 from the fluid pressure source 58, the pressurized fluid routing
system 178 and the choke 32. Representatively, the feedback signal 186 can include
one or more sensed operating parameters of the main pump 58 such as the position of
its piston 70, the feedback signal 188 can include one or more sensed operating parameters
of the switching pump 60 such as the position of its piston 144, and the feedback
signal 190 can include one or more sensed operating parameters of the choke 32 such
as the position of its drive piston 42 (as monitored by the choke's position sensing
section 48) and the adjacent production tubing fluid pressure drop (as transmitted
from its pressure sensors 50 and 52).
[0085] In response to the receipt of these feedback signals 186,188,190 the controller 182
respectively transmits control signals 192,194 to the pumps 58 and 60 to regulate
their operation in a manner maintaining the controlled operating parameter of the
choke 32 at a magnitude corresponding to that set by the operating parameter set point
signal 184 transmitted to the controller 182.
[0086] In addition to desirably requiring only a relatively low electrical power input,
each self-contained, closed circuit actuator 54 is quite compact, and does not require
any hydraulic line connection to any surface equipment. Accordingly, as can be seen
in FIGS. 1 and 4, none of the wellbore space needs to be dedicated to hydraulic lines
routed from the surface to the actuators 54. Additionally, when the electrical power
source 92 for each actuator 54 is located downhole, as schematically illustrated in
FIG. 4, no well bore space is taken up by electrical lines routed from the surface
to the actuators 54.
[0087] Representatively, each actuator 54 is compactly mounted on the production tubing
22 (see FIG. 1) in generally annular housings 196 and 198 which outwardly circumscribe
the production tubing 22 just above the position sensing section 48 of each choke
32. The accumulator portions 108,110 of each actuator 54 are disposed within the housings
196, with controllers 182 and the balances of the actuators 54 being disposed in the
housings 198.
[0088] While the well tool assemblies 32 representatively illustrated and described herein
are variable choke assemblies, the actuators 54 could also be operatively associated
with a wide variety of other types of well tool assemblies as well without departing
from principles of the present invention. For example, the actuators 54 could be operatively
associated with other types of flow control devices such as sliding sleeve devices,
safety valves, variable flow area sand screens, and the like. Also, the actuators
54 could be operatively associated with various non-flow control types of downhole
well tool assemblies such as, for example, packer structures.
[0089] Additionally, while the first and second sources of pressurized fluid incorporated
in the self-contained, closed circuit actuators 54 have been representatively illustrated
and described herein as being reciprocable hydraulic pumps, it will be readily appreciated
by those of ordinary skill in this particular art that other types of pumps, as well
as other types of non-pump sources of pressurized fluid, could alternatively be utilized
without departing from principles of the present invention.
[0090] Of course, a person skilled in the art would, upon a careful consideration of the
above description of representative embodiments of the invention, readily appreciate
that many modifications, additions, substitutions, deletions, and other changes may
be made to the specific embodiments, and such changes are contemplated by the principles
of the present invention. Accordingly, the foregoing detailed description is to be
clearly understood as being given by way of illustration and example only, the spirit
and scope of the present invention being limited solely by the appended claims.