U.S. patent application number 09/769047 was filed with the patent office on 2002-03-28 for toroidal choke inductor for wireless communication and control.
Invention is credited to Bass, Ronald Marshall, Burnett, Robert Rex, Carl, Frederick Gordon JR., Savage, William Mountjoy, Vinegar, Harold J..
Application Number | 20020036085 09/769047 |
Document ID | / |
Family ID | 27586638 |
Filed Date | 2002-03-28 |
United States Patent
Application |
20020036085 |
Kind Code |
A1 |
Bass, Ronald Marshall ; et
al. |
March 28, 2002 |
Toroidal choke inductor for wireless communication and control
Abstract
An induction choke in a petroleum well where a voltage potential
is developed across the choke to power and communicate with devices
and sensors in the well. Preferably, the induction choke is a
ferromagnetic material and acts as an impedance to a time-varying
current, e.g. AC. The petroleum well includes a cased wellbore
having a tubing string positioned within and longitudinally
extending within the casing. A controllable gas lift valve, sensor,
or other device is coupled to the tubing. The valve sensor, or
other device is powered and controlled from the surface.
Communication signals and power are sent from the surface using the
tubing, casing, or liner as the conductor with a casing or earth
ground. For example, AC current is directed down a casing or tubing
or a lateral where the current encounters a choke. The voltage
potential developed across the choke is used to power electronic
devices and sensors near the choke. Such induction chokes may be
used in many other applications having an elongated conductor such
as a pipe, where it is desirable to power or communicate with a
valve, sensor, or other device without providing a dedicated power
or communications cable.
Inventors: |
Bass, Ronald Marshall;
(Houston, TX) ; Vinegar, Harold J.; (Houston,
TX) ; Burnett, Robert Rex; (Katy, TX) ;
Savage, William Mountjoy; (Houston, TX) ; Carl,
Frederick Gordon JR.; (Houston, TX) |
Correspondence
Address: |
Del S. Christensen
Shell Oil Company
Legal - Intellectual Property
P.O. Box 2463
Houston
TX
77252-2463
US
|
Family ID: |
27586638 |
Appl. No.: |
09/769047 |
Filed: |
January 24, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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60177999 |
Jan 24, 2000 |
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60186376 |
Mar 2, 2000 |
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60178000 |
Jan 24, 2000 |
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60186380 |
Mar 2, 2000 |
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60186505 |
Mar 2, 2000 |
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60178001 |
Jan 24, 2000 |
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60177883 |
Jan 24, 2000 |
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60177998 |
Jan 24, 2000 |
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60177997 |
Jan 24, 2000 |
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60181322 |
Feb 9, 2000 |
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60186504 |
Mar 2, 2000 |
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60186379 |
Mar 2, 2000 |
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60186394 |
Mar 2, 2000 |
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60186382 |
Mar 2, 2000 |
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60186503 |
Mar 2, 2000 |
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60186527 |
Mar 2, 2000 |
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60186393 |
Mar 2, 2000 |
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60186531 |
Mar 2, 2000 |
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60186377 |
Mar 2, 2000 |
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60186381 |
Mar 2, 2000 |
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60186378 |
Mar 2, 2000 |
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60177999 |
Jan 24, 2000 |
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Current U.S.
Class: |
166/250.01 ;
166/250.12; 166/313; 166/373; 166/386; 166/50; 166/66;
166/66.6 |
Current CPC
Class: |
E21B 17/028 20130101;
E21B 17/003 20130101; E21B 47/10 20130101; E21B 41/02 20130101;
E21B 37/06 20130101; E21B 47/06 20130101; E21B 43/12 20130101; E21B
43/123 20130101; E21B 41/0085 20130101; E21B 34/08 20130101; E21B
47/107 20200501; E21B 47/11 20200501; E21B 43/14 20130101; E21B
43/16 20130101; E21B 47/13 20200501; E21B 47/103 20200501; E21B
34/066 20130101; E21B 47/12 20130101; E21B 2200/22 20200501; E21B
43/122 20130101; H04B 13/02 20130101; E21B 34/16 20130101; E21B
33/1294 20130101 |
Class at
Publication: |
166/250.01 ;
166/250.12; 166/373; 166/313; 166/386; 166/50; 166/66;
166/66.6 |
International
Class: |
E21B 034/06; E21B
047/00 |
Claims
We claim:
1. A current impedance apparatus for using a time-varying
electrical current in a conductor, comprising an induction choke
generally configured for enveloping a portion of said conductor
such that with said choke positioned in enveloping relation about
said portion of said piping structure, and with a device
electrically connected to said conductor between one side of said
choke and another side of said choke, a voltage potential is
developed on the conductor on each side of said choke when a
time-varying electrical current is transmitted through and along
said portion of said conductor and such that a portion of said
current travels through said device electrically connected to said
conductor on each side of said choke.
2. A current impedance apparatus in accordance with claim 1,
wherein said induction choke is unpowered.
3. A current impedance apparatus in accordance with claim 1,
wherein said choke is generally cylindrical shaped with a generally
cylindrical shaped void formed therethrough, said void being
adapted to receive said portion of said piping structure
therein.
4. A current impedance apparatus in accordance with claim 1,
further comprising an insulating shell that substantially covers
the surfaces of said induction choke.
5. A current impedance apparatus in accordance with claim 3,
wherein said insulating shell comprises a composite material
comprising a cloth and an epoxy resin.
6. A current impedance apparatus in accordance with claim 4,
wherein said cloth comprises fiberglass.
7. A current impedance apparatus in accordance with claim 4,
wherein said cloth comprises kevlar.
8. A current impedance apparatus in accordance with claim 3,
wherein said insulating shell comprises a hard, abrasion resistant,
and corrosion resistant material.
9. A current impedance apparatus in accordance with claim 1,
wherein said induction choke is adapted to function without being
powered by an electrical connection due to its magnetic and
geometric properties.
10. A current impedance apparatus in accordance with claim 1,
wherein said induction choke comprises a ferromagnetic
material.
11. A current impedance apparatus in accordance with claim 1,
wherein said induction choke comprises a material selected from a
group consisting of low frequency transformer core alloys such as
Permalloy, Supermalloy, and high-frequency transformer and choke
materials such as ferrites.
12. A current impedance apparatus with claim 1, wherein said choke
has a relative permeability in the range of 1,000-150,000.
13. A current impedance apparatus with claim 1, wherein said
conductor comprises the production tubing in a petroleum well and
the induction choke is configured for concentric positioning around
a portion of the tubing.
14. A method of powering a device electrically connected to an
elongated conductor comprising the steps of: positioning an
induction choke in concentric relation about a portion of the
conductor; applying a time-varying electrical current to the
conductor on one side of the induction choke; developing a voltage
potential on each side of the induction choke when said
time-varying electrical current is applied; using the voltage
potential to power a device.
15. A system for defining an electrical circuit, comprising: a
piping structure comprising a first end, a second end, and an
electrically conductive portion extending from said first end to
said second end; a source of time-varying current electrically
connected to said electrically conductive portion of said piping
structure at a location along said first end; an induction choke
located about a portion of said electrically conductive portion of
said piping structure; a device comprising two terminals, said
device terminals each being electrically connected to said
electrically conductive portion of said piping structure such that
said choke is located along said piping structure between said
electrical connection locations for said device terminals; and an
electrical return electrically connecting between said electrically
conductive portion of said piping structure along said second end
and said source to complete said electrical circuit, such that said
electrical connection for one of said device terminals is between
said choke and said electrical connection location along said
piping structure for said electrical return.
16. A system in accordance with claim 15, wherein said choke is
located along said second end.
17. A system in accordance with claim 15, wherein said first end is
near the surface and said second end is downhole in a borehole.
18. A system in accordance with claim 15, further comprising: a
second induction choke located about a portion of said piping
structure along said first end, such that said source is connected
to said piping structure between said chokes.
19. A system in accordance with claim 15, wherein said choke is
located along said first end.
20. A system in accordance with claim 17, wherein said first end is
near the surface and said second end is downhole in a borehole.
21. A system in accordance with claim 17, further comprising: a
second induction choke located about a portion of said piping
structure along said second end.
22. A system in accordance with claim 15, further comprising a
plurality of induction chokes distributed within at least one
branch of a well, wherein at least some of said plurality of
induction chokes are adapted to provide power to an additional
device associated therewith using a voltage potential developed
across each of said at least some of said plurality of induction
chokes.
23. A system in accordance with claim 15, further comprising a
plurality of induction chokes distributed along said piping
structure, wherein at least some of said plurality of induction
chokes are adapted to provide power to an additional device
associated therewith using a voltage potential developed across
each of said at least some of said plurality of induction
chokes.
24. A system in accordance with claim 15, further comprising: an
additional induction choke that does not have an additional device
associated therewith, wherein said additional choke is adapted to
route current to other portions of said piping structure.
25. A system in accordance with claim 15, wherein said induction
choke comprises a ferromagnetic material.
26. A system in accordance with claim 15, wherein said induction
choke comprises a material selected from a group consisting of low
frequency transformer core alloys such as Permalloy, Supermalloy,
and high-frequency transformer and choke materials such as
ferrites.
27. A system in accordance with claim 15, wherein said induction
choke is not powered.
28. A system in accordance with claim 15, wherein said induction
choke comprises an insulating shell that substantially covers the
surfaces of said induction choke.
29. A system in accordance with claim 15, wherein said induction
choke is electrically insulated from said piping structure.
30. A system in accordance with claim 15, wherein said induction
choke h as a generally toroidal shape and is generally concentric
about said piping structure such that a voltage potential is
developed across said choke when a time-varying electrical current
is transmitted through and along said portion of said piping
structure where said choke is located and such that a portion of
said current travels through said device.
31. A system in accordance with claim 28, wherein said induction
choke is a generally cylindrical body having a bore formed
therethrough, said bore being adapted to receive said piping
structure.
32. A system in accordance with claim 15, wherein the geometry,
material properties, and size of said induction choke, and the
frequency of a time-varying current output from said source are
adapted to provide communications and power to said device using
said electrical circuit.
33. A system in accordance with claim 15, wherein said choke has a
relative permeability in the range of 1,000-150,000.
34. A system in accordance with claim 15, wherein a time-varying
current output from said source comprises an alternating
current.
35. A system in accordance with claim 15, wherein a time-varying
current output from said source comprises an varying direct
current.
36. A system in accordance with claim 15, wherein said piping
structure comprises at least a portion of a production tubing
string for a well.
37. A system in accordance with claim 15, wherein said piping
structure comprises at least a portion of a pumping rod for a
well.
38. A system in accordance with claim 15, wherein said piping
structure comprises at least a portion of a well casing for a
well.
39. A system in accordance with claim 15, wherein said piping
structure comprises at least a portion of a production tubing
string for a well and at least a portion of a well casing for said
well.
40. A system in accordance with claim 15, wherein said piping
structure comprises at least a portion of at least one branch of a
well.
41. A system in accordance with claim 15, wherein said piping
structure comprises at least a portion of an oil refinery piping
network.
42. A system in accordance with claim 15, wherein said piping
structure comprises at least a portion of above surface refinery
production pipes.
43. A system in accordance with claim 15, wherein said electrical
return comprises a well casing for a well.
44. A system in accordance with claim 15, wherein said electrical
return comprises at least a portion of an earthen ground.
45. A system in accordance with claim 15, wherein said electrical
return comprises at least a portion of a conductive fluid.
46. A system in accordance with claim 15, wherein said electrical
return comprises at least a portion of a packer.
47. A system in accordance with claim 15, wherein said electrical
return comprises at least a portion of another piping structure of
a same well.
48. A system in accordance with claim 15, wherein said electrical
return comprises at least a portion of another piping structure of
another well.
49. A system in accordance with claim 15, wherein said electrical
return comprises at least a portion of an equipment part having an
elongated bore containing at least a portion of said piping
structure therein.
50. A system in accordance with claim 15, further comprising an
electrical insulating barrier between said piping structure and at
least a portion of said electrical return.
51. A system in accordance with claim 48, wherein said barrier
comprises concrete.
52. A system in accordance with claim 48, wherein said barrier
comprises a non-metallic material.
53. A system in accordance with claim 15, wherein said device
comprises a control module adapted to control and communicate with
at least one additional electronic component electrically connected
thereto.
54. A system in accordance with claim 15, wherein said device
comprises a transformer.
55. A system in accordance with claim 15, wherein said device
comprises a battery.
56. A system in accordance with claim 15, wherein said device
comprises multiple components electrically connected together.
57. A system in accordance with claim 15, wherein said device
comprises an electrically controllable and electrically actuated
valve.
58. A system in accordance with claim 15, wherein said device
comprises an electrically controllable valve actuated by a low
current electric motor.
59. A system in accordance with claim 15, wherein said device
comprises a sensor for data acquisition.
60. A system in accordance with claim 15, wherein said device
comprises a sensor and an electrically controllable valve to form a
close loop system.
61. A system in accordance with claim 15, wherein said device
comprises a tracer fluid and an electrically controllable release
valve.
62. A system in accordance with claim 15, wherein said device
comprises a power transformer adapted to supply power to said
device, and a modem transformer adapted to provide communication
signals for said device.
63. A system in accordance with claim 15, wherein said device
comprises a testing probe.
64. A system in accordance with claim 15, further comprising: an
electrical insulator located at said first end of said piping
structure, said insulator being between said piping structure and
said electrical return such that said piping structure is
electrically insulated from said electrical return along said first
end.
65. A system in accordance with claim 62, wherein said insulator
comprises an insulated hanger.
66. A system in accordance with claim 62, wherein said insulator
comprises an insulated pipe section.
67. A system in accordance with claim 15, wherein at least a
portion of said piping structure is substantially electrically
isolated from the earth.
68. A system in accordance with claim 15, further comprising a
computer system adapted to send and receive data to and from said
device via said electric circuit.
69. A system for defining an electrical circuit, comprising: a
piping structure comprising a first location, a second location,
and an electrically conductive portion extending from said first
location to said second location; two induction chokes, a first of
said chokes being located about a portion of said piping structure
along said first location, and a second of said chokes being
located about a portion of said piping structure along said second
location; a source of time-varying current electrically connected
to said electrically conductive portion of said piping structure at
a location between said chokes; a device comprising two terminals,
said device terminals each being electrically connected to said
electrically conductive portion of said piping structure such that
said second choke is located along said piping structure between
said electrical connection locations for said device terminals; and
an electrical return electrically connecting between said
electrically conductive portion of said piping structure along said
second location and said source to complete said electrical
circuit, such that said electrical connection for one of said
device terminals is between said electrical connection location
along said piping structure for said electrical return and said
choke.
70. A method of operating a well having a pipe disposed in the
earth comprising the steps of: providing an induction choke coupled
to the pipe downhole and disposed in enveloping relationship to a
portion of the pipe; coupling time varying current to the pipe
uphole relative to the choke; inhibiting time varying current flow
distal to the choke and developing a voltage potential across the
choke; coupling a device to the pipe proximate the choke; and
operating said device with said voltage potential to operate said
well.
71. The method of claim 71, including converting said voltage
potential to direct current and operating said device coupled to
the pip with said direct current.
72. The method of claim 71, including coupling multiple devices to
said pipe and operating each device.
73. The method of claim 73, wherein a number of the devices are
powered by the voltage potential developed across a single
induction choke.
74. The method of claim 73, wherein a number of the devices are
associated with a number of induction chokes and each device is
powered by the voltage potential developed across the associated
induction choke.
75. The method of claim 71, wherein the device is a controllable
valve.
76. The method of claim 71, wherein the device is a sensor.
77. In a petroleum well having a piping structure embedded in an
elongated borehole extending into the earth, the improvement
comprising: an induction choke configured for enveloping a portion
of said piping structure and operable for developing a voltage
potential on the piping structure on each side of the induction
choke when a time-varying current is applied to the piping
structure on one side of the induction choke.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] This application claims the benefit of the U.S. Provisional
Applications in the following table, all of which are hereby
incorporated by reference:
1 U.S. PROVISIONAL APPLICATIONS Serial T&K # Number Title
Filing Date TH 1599 60/177,999 Toroidal Choke Inductor Jan. 24,
2000 for Wireless Communication and Control TH 1599x 60/186,376
Toroidal Choke Inductor Mar. 2, 2000 TH 1600 60/178,000
Ferromagnetic Choke in Jan. 24, 2000 Wellhead TH 1600x 60/186,380
Ferromagnetic Choke in Mar. 2, 2000 Wellhead TH 1601 60/186,505
Reservoir Production Mar. 2, 2000 Control from Intelligent Well
Data TH 1602 60/178,001 Controllable Gas-Lift Well Jan. 24, 2000
and Valve TH 1603 60/177,883 Permanent, Downhole, Jan. 24, 2000
Wireless, Two-Way Telemetry Backbone Using Redundant Repeater,
Spread Spectrum Arrays TH 1668 60/177,998 Petroleum Well Having
Jan. 24 2000 Downhole Sensors, Communication, and Power TH 1669
60/177,997 System and Method for Jan. 24, 2000 Fluid Flow
Optimization TS6185 60/181,322 Optimal Predistortion in Feb. 9,
2000 Downhole Communications System TH 1671 60/186,504 Tracer
Injection in a Mar. 2, 2000 Production Well TH 1672 60/186,379
Oilwell Casing Electrical Mar. 2, 2000 Power Pick-Off Points TH
1673 60/186,394 Controllable Production Mar. 2, 2000 Well Packer TH
1674 60/186,382 Use of Downhole High Mar. 2, 2000 Pressure Gas in a
Gas Lift Well TH 1675 60/186,503 Wireless Smart Well Casing Mar. 2,
2000 TH 1677 60/186,527 Method for Downhole Power Mar. 2, 2000
Management Using Energization from Distributed Batteries or
Capacitors with Reconfigurable Discharge TH 1679 60/186,393
Wireless Downhole Well Mar. 2, 2000 Interval Inflow and Injection
Control TH 1681 60/186,394 Focused Through-Casing Mar. 2, 2000
Resistivity Measurement TH 1704 60/186,531 Downhole Rotary
Hydraulic Mar. 2, 2000 Pressure for Valve Actuation TH 1705
60/186,377 Wireless Downhole Mar. 2, 2000 Measurement and Control
For Optimizing Gas Lift Well and Field Performance TH 1722
60/186,381 Controlled Downhole Mar. 2, 2000 Chemical Injection TH
1723 60/186,378 Wireless Power and Mar. 2, 2000 Communications
Cross-Bar Switch
[0002] The current application shares some specification and
figures with the following commonly owned and concurrently filed
applications in the following table, all of which are hereby
incorporated by reference:
2 COMMONLY OWNED AND CONCURRENTLY FILED U.S. PATENT APPLICATIONS
T&K # Ser. No. Title Filing Date TH 1600US 09/.sub.----------
Induction Choke for Power January 24, Disribution in Piping 2001
Structure TH 1602US 09/.sub.---------- Controllable Gas-Lift
January 24, Well and Valve 2001 TH 1603US 09/.sub.----------
Permanent, Downhole, January 24, Wireless, Two-Way 2001 Telemetry
Backbone Using Redundant Repeaters TH 1668US 09/.sub.----------
Petroleum Well Having January 24, Downhole Sensors, 2001
Communication, and Power TH 1669US 09/.sub.---------- System and
Method for January 24, Fluid Flow Optimization 2001
FIELD OF THE INVENTION
[0003] The present invention relates to the use of a ferromagnetic
choke in a petroleum well where a voltage potential is developed
across the choke to power and communicate with devices and sensors
in the well.
DESCRIPTION OF RELATED ART
[0004] Several methods have been devised to place Controllable
valves and other devices and sensors downhole on the tubing string
in a well, but all such known devices typically use an electrical
cable along the tubing string to power and communicate with the
devices and sensors. It is undesirable and in practice difficult to
use a cable along the tubing string either integral with the tubing
string or spaced in the annulus between the tubing and the casing
because of the number of failure mechanisms present in such a
system. Other methods of communicating within a borehole are
described in U.S. Pat. Nos. 5,493,288; 5,576,703; 5,574,374;
5,467,083; 5,130,706.
[0005] U.S. Pat. No. 6,070,608 describes a surface controlled gas
lift valve for use in oil wells. Methods of actuating the valve
include electro-hydraulic, hydraulic, and pneumo-hydraulic. Sensors
relay the position of the variable orifice and critical fluid
pressures to a panel on the surface. However, when describing how
electricity is provided to the downhole sensors and valves, the
means of getting the electric power/signal to the valves/sensors is
described as an electrical conduit that connects between the
valve/sensor downhole and a control panel at the surface. U.S. Pat.
No. 6,070,608 does not specifically describe or show the current
path from the device downhole to the surface. The electrical
conduit is shown in the figures as a standard electrical conduit,
i.e., an extended pipe with individual electrically insulated wires
protected therein, such that the pipe provides physical protection
and the wires therein provide the current path. But such standard
electrical conduits can be difficult to route at great depths,
around turns for deviated wells, along multiple branches for a well
having multiple lateral branches, and/or in parallel with coil
production tubing. Hence, there is a need for a system and method
of providing power and communications signals to downhole devices
without the need for a separate electrical conduit filled with
wires and strung along side of production tubing.
[0006] U.S. Pat. No. 4,839,644 describes a method and system for
wireless two-way communications in a cased borehole having a tubing
string. However, this system describes a downhole toroid antenna
for coupling electromagnetic energy in a waveguide TEM mode using
the annulus between the casing and the tubing. This toroid antenna
uses an electromagnetic wave coupling which requires a
substantially nonconductive fluid (such as refined, heavy oil) in
the annulus between the casing and the tubing and a toroidal cavity
and wellhead insulators. Therefore, the method and system described
in U.S. Pat. No. 4,839,644 is expensive, has problems with brine
leakage into the casing, and is difficult to use as a scheme for
downhole two-way communication.
[0007] Other downhole communication schemes such as mud pulse
telemetry (U.S. Pat. Nos. 4,648,471; 5,887,657 have shown
successful communication at low data rates but are of limited
usefulness as a communication scheme where high data rates are
required or it is undesirable to have complex, mud pulse telemetry
equipment downhole. Still other downhole communication methods have
been attempted, see U.S. Pat. Nos. 5,467,083; 4,739,325; 4,578,675;
5,883,516; and 4,468,665 as well as downhole permanent sensors and
control systems: U.S. Pat. Nos. 5,730,219; 5,662,165; 4,972,704;
5,941,307; 5,934,371; 5,278,758; 5,134,285; 5,001,675; 5,730,219;
5,662,165.
[0008] It would, therefore, be a significant advance in the
operation of petroleum wells if the tubing, casing, liners and
other conductors installed in the well could be used for the
communication and power conductors to control and operate devices
and sensors downhole in a petroleum well.
[0009] Induction chokes have been used in connection with sensitive
instrumentation to protect against surges and stray voltage. For
example, most personal computers have some sort of choke
incorporated into its AC power cord and video signal cable for such
protection. Such protection chokes work well for their intended
purpose, but do not operate to define a power or communication
circuit.
[0010] All references cited herein are incorporated by reference to
the maximum extent allowable by law. To the extent a reference may
not be fully incorporated herein, it is incorporated by reference
for background purposes and indicative of the knowledge of one of
ordinary skill in the art.
SUMMARY OF THE INVENTION
[0011] The problems outlined above are largely solved and met by a
petroleum well having one or more ferromagnetic chokes in
accordance with the present invention. Broadly speaking, the
petroleum well includes a cased wellbore having a tubing string
positioned within and longitudinally extending within the casing. A
controllable valve, sensor, or other device is coupled to the
tubing. The valve sensor, or other device is powered and controlled
from the surface. Communication signals and power are sent from the
surface using the tubing, casing, or liner as the conductor. For
example, AC current may be directed down the tubing to a point
where the current encounters a choke. The voltage potential
developed across the choke is used to power communication modems,
valves, electronic devices and sensors near the choke.
[0012] In more detail, a surface computer includes a modem with an
AC signal imparted to a conductive conduit, such as the tubing or
casing. The AC signal develops a potential across a choke and a
power supply creates DC voltage to power a connected controllable
valve, sensor, or other device. Preferably, the casing or liner
terminates at earth and is used as the ground return conductor,
although an independent ground wire may be used. In a preferred
embodiment, the powered device comprises a controllable valve that
regulates passage of gas between the annulus and the interior of
the tubing.
[0013] In enhanced forms, the petroleum well includes one or more
sensors downhole which are preferably in contact with the downhole
power and communications module and communicate with the surface
computer. Such sensors as temperature, pressure, acoustic, valve
position, flow rates, and differential pressure gauges are
advantageously used in many situations. The sensors supply
measurements to the modem for transmission to the surface or
directly to a programmable interface controller operating a
downhole device, such as controllable valve for controlling the gas
flow through the valve.
[0014] Such ferromagnetic chokes are coupled to a conductor
(tubing, casing, liner, etc.) to act as a series impedance to
current flow. In one form, a ferromagnetic choke is placed around
the tubing or casing downhole and the AC used for power and
communication signal is imparted to the tubing, casing or liner
near the surface. The downhole choke around the tubing, casing or
liner develops a potential used to power and communicate with a
controllable valve or sensor.
[0015] In another form, a surface computer is coupled via a surface
master modem and the tubing or casing to a plurality of laterals,
each having a downhole slave modem to operate a controllable valve
in a lateral. The surface computer can receive measurements from a
variety of sources, such as the downhole sensors, measurements of
the oil output, and measurements of the fluid flow in each lateral.
Using such measurements, the computer can compute an optimum
position of each controllable valve, more particularly, the optimum
amount or composition of fluid production from each lateral.
Additional enhancements are possible, such as controlling the
amount of compressed gas input into the well at the surface,
controlling a surfactant injection system, and receiving production
and operation measurements from a variety of other wells in the
same field to optimize the production of the field.
[0016] Construction of such a petroleum well is designed to be as
similar to conventional construction methodology as possible. That
is, the well completion process comprises cementing a casing or
liner within the borehole, placing production tubing within the
casing or liner and generally concentric with such casing or liner,
and placing a packer above the production zone to control fluid
passage in the annulus between the tubing and the casing or liner.
The completed well includes a choke concentric with the tubing,
casing or liner. After cementing the well the casing is partially
isolated from the earth. The tubing string passes through the
casing and packer and communicates with the production zone. In the
section of the tubing string near the choke, sensors or operating
devices are coupled to the string. With such configuration a
controllable gas lift valve or sensor pod may be directly
permanently coupled to the tubing (i.e. "tubing conveyed").
Alternatively, , a controllable gas lift valve or sensor pod may be
inserted in a side pocket mandrel. A power and communications
module uses the voltage potential developed across the choke to
power the valve and sensors.
[0017] A sensor and communication pod can be inserted without the
necessity of including a controllable gas lift valve or other
control device. That is, an electronics module having pressure,
temperature or acoustic sensors, power supply, and a modem is
inserted into a side pocket mandrel for communication to the
surface computer using the tubing and casing conductors.
Alternatively, such electronics modules may be mounted directly on
the tubing and not be configured to be wireline replaceable. If
directly mounted to the tubing an electronic module or a device may
only be replaced by pulling the entire tubing string. In another
form, an insulated tubing section near the wellhead may be used to
ensure electrical isolation.
[0018] In one broad aspect, the present invention relates to a
current impedance device, particularly useful in petroleum wells,
comprising a cylindrical choke of ferromagnetic material having an
annular bore extending longitudinally therein and adapted for
receiving petroleum well cylindrical conductor therein. Many
modifications are, of course possible, with such ferromagnetic
chokes being applicable to casing, tubing, liners, and headers and
other conductors used downhole in a petroleum well.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] Other objects and advantages of the invention will become
apparent upon reading the following detailed description and upon
referencing the accompanying drawings, in which:
[0020] FIG. 1 is a schematic of a petroleum well illustrating the
general disposition of the major elements of the present invention
in relation to the major elements of a conventional well;
[0021] FIG. 2 is related to FIG. 1 and shows in more detail a
petroleum well incorporating electrical chokes and associated
communication, measurement and control equipment in accordance with
the methods of the present invention;
[0022] FIG. 3 is related to FIG. 2, and shows the electrical
equivalent circuit of that well;
[0023] FIG. 4a is related to FIG. 2, and shows the overall assembly
of one of the chokes of FIG. 1;
[0024] FIG. 4b is related to FIG. 4a, and shows in detail the
components used in the construction of the choke assembly of FIG.
4a;
[0025] FIG. 5a is an axial cross-section of a choke showing
variables used in the design analysis of a choke disposed between
tubing and casing;
[0026] FIG. 5b is a radial cross-section of a choke showing
variables used in the design analysis of a choke disposed between
tubing and casing;
[0027] FIG. 5c is an axial cross-section of a choke showing
variables used in the design analysis of a choke external to both
tubing and casing;
[0028] FIG. 5d is a radial cross-section of a choke showing
variables used in the design analysis of a choke external to both
tubing and casing;
[0029] FIG. 6 is a schematic of a multilateral petroleum well
incorporating electrical chokes of the present invention;
[0030] FIG. 7a is a schematic of a petroleum well illustrating
downhole equipment power and communications connections in
electrical series;
[0031] FIG. 7b is a schematic of a petroleum well illustrating
downhole equipment power and communications connections in
electrical parallel;
[0032] FIG. 7c is a schematic of a switching circuit enabling
reconfiguration of downhole power and communications
connections;
[0033] FIG. 8 is a schematic of a petroleum well illustrating the
control of power and communications zones by the use of chokes of
the present invention;
[0034] FIG. 9 shows a system in accordance with another embodiment
of the present invention, in which chokes are disposed external to
the well casing;
[0035] FIG. 10 shows a system in accordance with another embodiment
of the present invention, in which a single choke is disposed to
direct power into a lateral;
[0036] FIG. 11 shows a system in accordance with another embodiment
of the present invention, in which two chokes are disposed to
direct power into a lateral;
[0037] FIG. 12 shows a system in accordance with another embodiment
of the present invention, in which chokes are disposed on a pump
rod;
[0038] FIG. 13 is alternative embodiment to FIG. 12; and
[0039] FIG. 14 is a schematic showing the use of chokes to provide
electrical power and communications between a central field
facility and individual well heads using collection lines as the
transmission path.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0040] Referring now to the drawings, wherein like reference
numbers are used to designate like elements throughout the various
views, several embodiments of the present invention are further
described. The figures are not necessarily drawn to scale, and in
some instances the drawings have been exaggerated or simplified for
illustrative purposes only. One of ordinary skill in the art will
appreciate the many possible applications and variations of the
present invention based on the following examples of possible
embodiments of the present invention.
[0041] The terms "first end" and "second end" as used herein are
defined generally to call out a side or portion of a piping
structure, which may or may not encompass the most proximate
locations, as well as intermediate locations along a called out
side or portion of the piping structure. Similarly, in accordance
with conventional terminology of oilfield practice, the descriptors
"upper", "lower", "uphole" and "downhole" refer to distance along
hole depth from the surface, which in deviated wells may or may not
accord with absolute vertical placement measured with reference to
the ground surface.
[0042] FIG. 1 shows a system defining an electrical circuit for
providing power and/or communications in a well or borehole via a
piping structure by using one or more unpowered induction chokes in
accordance with a first embodiment of the present invention. The
system of the first embodiment comprises an electrically resistive
device 146, an unpowered induction choke 32, an electrically
conductive piping structure 34, a well casing 36, a source of
time-varying current 38, and a device pod 40.
[0043] A piping structure can be one single pipe, a tubing string,
a well casing, a pumping rod, a series of interconnected pipes or
rods, a branch or lateral extension of a well, or a network of
interconnected pipes. For the present invention, at least a portion
of the piping structure needs to be electrically conductive, such
electrically conductive portion may be the entire piping structure
(e.g., steel pipes, copper pipes) or a longitudinal extending
electrically conductive portion combined with a longitudinally
extending non-conductive or partially resistive portion. In other
words, an electrically conductive piping structure is one that
provides an electrical conducting path from a first end where a
power source is electrically connected to a second end where a
device and/or electrical return is electrically connected. The
piping structure will typically be conventional round metal tubing,
but the cross-section geometry of the piping structure, or any
portion thereof, can vary in shape (e.g., round, rectangular,
square, oval) and size (e.g., length, diameter, wall thickness)
along any portion of the piping structure.
[0044] In the first embodiment shown in FIG. 1, the piping
structure comprises a production tubing string 34 for a well, which
is typically steel tubing. The system has an electrical impeding
device 146 located about the tubing 34 along a first end 41 near
the surface. Device 146 may consist of an electrically insulating
joint as shown in FIG. 1, or an unpowered choke of the present
invention. A lower choke 32 is located about the tubing along a
second end 42 downhole within the well. The source of time-varying
current 38 is electrically connected to the tubing 34 between the
impeding devices 30, 32. The time-varying current can be
alternating current (AC) or a varying direct current (DC), but AC
is typically more practical in use. AC power and communications
signals from the source 38 are connected by conductor 44 to the
tubing 34 via an insulating feedthrough 76. The device 40 comprises
two terminals 51, 52. A device terminal is defined generally as an
electrical connection point for a device, which may include but is
not limited to: a wire, a device enclosure, a prong, a pin, a
contact pad, a solder point, a female receptacle, a shaft, or any
combination thereof. A first device terminal 51 is electrically
connected to the tubing 34 downhole between the connection location
for the source of current 38 and the lower choke 32.
[0045] A second device terminal 52 is also electrically connected
to the tubing 34, but at a location on the opposite side of the
lower choke 32 relative to the electrical connection location for
the first device terminal 51. As described further below with
equations, a voltage potential exists across the choke 32 when a
time-varying current flows through the tubing. Hence, the device 40
is electrically connected across the voltage potential on the
tubing developed by the choke 32 when AC flows in the tubing 34,
which provides current flow through the device 40.
[0046] Device 146 may consist of an electrically insulating joint
hanger, or a choke in accordance with the present invention. While
electrically insulating joint hangers provide true electrical
isolation, they must sustain significant mechanical loads on
insulating materials such as plastics or ceramics, and are
therefore subject to damage from those loads. Chokes cannot provide
complete isolation, but are able to sustain high mechanical loads
since they are constructed such that all the load-bearing elements
are composed of metal.
[0047] At least a portion of the well casing 36 is electrically
conductive. The electrically conductive portion of the well casing
36 is electrically connected to the tubing 34 (e.g., via conductive
fluid 82 and/or packer 56) and the source of current 38. Hence, the
electrically conductive portion of the well casing 36 acts as part
of an electrical return to complete the electrical circuit.
[0048] Where centralizers are used to control the position of the
tubing 34 relative to the casing 36, such centralizers which are
disposed between devices 30 and 32 must not be electrically
conductive. Suitable centralizers are typically composed of molded
or machined plastic.
[0049] Therefore, the electrical circuit is formed by the system of
the first embodiment, wherein the time-varying current (e.g., AC)
can flow from the power source 38 to the tubing 34, along the
tubing 34 between the device 146 and the choke 32, through the
device 40 to the tubing 34 below the lower choke 32, to the casing
36 via the packer 56 and/or the conductive fluid 82, and along the
well casing 36 to the source 38 to complete the electrical circuit.
Thus, the downhole device 40 can receive power, as well as
send/receive communication signals, using the tubing 34 between the
upper and lower devices 146, 32 as one of the primary conductors
and as a power and/or communications path.
[0050] In the application of the first embodiment shown in FIG. 1,
the gas-lift oil well extends from the surface 64 through a
borehole and extends into a production zone 66 downhole. A
production platform 68 is schematically illustrated above the
surface 64. A hanger 54 supports the production tubing string 34
from the well casing 36. The casing 36 is conventional, i.e., it is
typically metal tubing held in place by injecting cement 70 between
the casing and the earth in the borehole during well completion.
Similarly the tubing string 34 is generally conventional comprising
a plurality of elongated tubular metal production pipe sections
joined by threaded couplings (not shown) at each end of each tubing
section.
[0051] A gas input throttle 74 is employed to permit the input of
compressed gas into the tubing 34 via one or more valves contained
within pod 40 for lifting oil during production. Schematically
illustrated is a computer system and power source 38 at the surface
64 with power and communication feeds 44 passing through
electrically isolating pressure seal 76 and using return connection
78, which is electrically connected to the casing 36. The degree of
opening of gas lift valve may be controlled by means of setpoint
commands sent by communication from the surface modem to the
downhole modem and interpreted by a downhole control interface for
the motor of the gas lift valve. Sensor readings from the downhole
pod may either be processed locally within the pod to provide
autonomous control, or the sensor readings may be conveyed to the
surface by means of the communications between the downhole and
surface modems, for analysis at the surface.
[0052] The choke 32 is unpowered and made from a material having a
high magnetic permeability (e.g., a relative permeability of 1000
to 150,000), such as a ferromagnetic metal alloy or a ferrite. The
choke 32 is electrically insulated from the tubing 34 and acts to
create a reactive impedance to AC flow in the tubing. In the case
where the upper device 146 is a choke (rather than an electrically
insulating joint), its action and construction is essentially the
same as the lower choke 32. The choke 32 (and 146 in the case where
it is a choke) are mounted concentric and external to the tubing 34
and are typically coated with shrink-wrap plastic to provide
electrical insulation, and may additionally be enclosed within an
epoxy or other structurally equivalent shell (not shown) to
withstand rough handling and corrosive conditions. As described in
the mathematical analysis below, the size and material of chokes
can be chosen to achieve a desired series impedance value. FIG. 2
illustrates in greater detail the preferred embodiment of the
invention outlined in FIG. 1 as it is applied to a gas-lift oil
well. FIG. 2 illustrates such a well consisting of casing 36
extending from the surface and containing production tubing 34. At
the well head the upper portion of the production tubing is
electrically isolated from the lower portion by means of an
electrically insulating joint hanger 146. At depth within the well
the annular space between casing 36 and tubing 34 contains
completion fluid 82, and an electrically conductive packer 56 which
hydraulically isolates the completion fluid from the production
zone 66. Fluids from the production zone 66 are conveyed to the
surface by passage through the production tubing 34. In FIG. 2 the
disposition of two chokes 32 are shown at depth within the well,
each of which is used to power electrical pods 40. These pods
implement any combination of communication, measurement and control
functions to assist well production operations.
[0053] Referring still to FIG. 2, the general disposition of
surface equipment is illustrated, consisting of an AC power source
48, a 1:10 power transformer 86, and a modem 39. One output side of
the surface power transformer and modem circuits are connected by
means of conductor 44 through a pressure sealed electrical
isolation feedthrough 76 to the production tubing section below the
electrically isolating hanger. The other output sides of the power
transformer and the surface master modem circuits are electrically
connected to the well casing.
[0054] FIG. 2 shows each pod being used to power and control a
motorized gas lift valve 24. For this purpose a suitable
implementation of the pod consists of a power transformer 111 with
a winding ratio such that 2 Volts on the tubing side creates 15
Volts on the electronics module side (and vice versa), and a main
printed circuit board (PCB) 112 having a modem 122 and other
electrical components to power and control the motorized gas lift
valve 24. The downhole modems within the pods communicate with the
modem at the surface, and possibly with each other, allowing data
to be transferred from each pod to the surface or between pods, and
instructions to be passed from the surface to control each gas lift
valve. Each modem is individually addressable, and each control or
sensor device within each pod is individually addressable.
[0055] While FIG. 2 illustrates the case where two downhole modules
are operated in the well, it will be readily apparent that the same
principle may be used to provide an arbitrary number of downhole
modules. This is useful in an application where a conductive
completion fluid 82 is present in the annulus before unloading a
gas-lift well. Each choke will not work sufficiently to develop a
voltage potential at its respective device when the choke is
submerged in conductive fluid, but as the conductive fluid is
progressively removed during the unloading process, each device can
receive power and/or communications (thus being controllable) when
the respective choke is no longer submerged in conductive fluid.
Hence, as the conductive fluid level drops during unloading, the
devices sequentially become controllable, which aids in achieving a
more controlled unloading procedure.
[0056] Referring to FIG. 3, the electrical equivalent circuit of
the power and communications path of FIG. 2 may be analyzed. The
casing and tubing form the major transmission paths for both the
power and communication signals. The casing is represented by the
conductor 101. The tubing is represented by conductor 102. Resistor
218 represents the combined distributed resistance offered by
casing and tubing, and is typically of the order of 1 Ohm. The
choke impedances are represented by inductors 32. At the frequency
of the AC power the reactive impedance offered by each choke is of
the order of 2 Ohms.
[0057] Referring still to FIG. 3, the surface modem ensemble 39 is
represented by resistor 212 for its receiver, and an AC source 214
for its transmitter. AC power input at the surface is represented
by AC source 216. The downhole electronic pods associated with each
choke are represented by power converter and modem ensembles 122,
composed of resistors 106 for the power converters and modem
receivers, and AC sources 108 for the modem transmitters. The
circuit is completed by the metal packer 56 which has a negligibly
small electrical impedance.
[0058] It is seen from FIGS. 2 and 3 that the downhole pods are
powered by the AC voltage developed on the tubing by each choke,
caused by the back-EMF created by the passage of current along the
tubing which passes through the choke. The chokes are designed to
develop about 2 Volts from the AC which passes through them, and
this AC is converted to DC in the power conditioning circuit which
is coupled through the power supply input transformer, following
standard practice for such AC-to-DC power conversion and
conditioning circuits. This DC power is typically supplied to the
pod sensors, modem, and control circuits at about 15 Volts, and of
the order of 10 Watts is typically available to power these
downhole sub-systems.
[0059] Referring to FIG. 4a, the construction of a suitable choke
may be described. A choke for a given application may be divided
into multiple sub-sections along its length (L). In other words,
stacking multiple sub-sections of chokes 134 together along the
choke axis 60, as shown in FIGS. 4a and 4b, provides the same
effect as have one large choke of length (L). Multiple sub-sections
134 stacked on top of one another act as a series of impedances,
which added together provide the same total impedance as a single
choke having the same total length of ferromagnetic material as the
aggregated sub-sections.
[0060] Referring to FIG. 4b, the details of a suitable choke
assembly are illustrated, though it will be clear to one familiar
with the art that alternative designs are feasible. The tubing
section 34 is composed of type 316 stainless steel and typically
has an outer diameter of 3.5 inches and a length of 10 feet. Each
end of the production tubing section 34 is furnished with New VAM
male threads by which mating sections of conventional production
tubing are attached. (New VAM is a registered Trademark of
Vallourec Mannesman Oil & Gas France, and defines a thread form
suitable for this purpose). At the upper and lower extremities of
the choke section are welding collars 50 with internal diameter
3.55 inches, length 2 inches, and wall thickness one quarter of an
inch. The section of tubing 34 between the welding collars is
covered with PTFE heat-shrink tubing 20 of 0.020 inches wall
thickness, and thus tubing 20 lies between the production tubing
section 34 and the internal walls of all the choke sub-sections
134. Each end of the choke assembly is furnished with a machined
plastic centralizer 114. A suitable machinable plastic is
polyetheretherketone (PEEK) which is a commodity material available
from many commercial sources.
[0061] Choke sub-sections 134 are formed by winding about 60 sheet
laminations of a high-permeability ferromagnetic alloy such as
Permalloy (Permalloy is a registered Trademark, of Western Electric
Company). Permalloy is a nickel/iron alloy with a nickel content in
the range 35% to 90% and is available as a commodity material from
many commercial sources. A suitable alloy is composed of 86%
nickel/14% iron, and the laminations are 0.014 inches thick and
2.35 inches wide such that the final dimensions of each choke
section are 3.6 inches internal diameter, 5.45 inches external
diameter, and 2.35 inches in the direction of the choke axis 60.
The laminating material is coated with a non-conductive material
such that adjacent laminations are electrically isolated from each
other, as in standard transformer construction practice. Fifteen
such choke sections are stacked to form a total choke assembly
suitable for usual power frequencies, 50 or 60 Hertz. At power
frequencies up to a few hundred Hertz, the laminated ferromagnetic
alloy construction can be used for the choke sections, as in
standard transformer design practice, and as described above.
Lamination is required to reduce eddy current losses which would
otherwise degrade the effectiveness of the choke. For material with
absolute magnetic permeability of 50,000 operating at 60 Hertz the
required lamination thickness for 2 skin depths is 0.8-millimeters
(0.031 inches), which is realistic and practical.
[0062] Between each choke section is a polytetrafluoroethylene
(PTFE) washer 136 with internal diameter 3.6 inches, external
diameter 5.45 inches, and thickness 0.030 inches. After all the
chokes are threaded onto the tubing, the entire section of chokes
is covered with PTFE heatshrink tubing 138 having 0.020 inches wall
thickness. The stainless steel rod 51 is 0.125 inches diameter
covered with polyethylene (PE) heat-shrink tubing and extends along
the length of the completed choke assembly. It is attached to the
upper welding collar 50 and passes through holes in the
centralizers 114. Its lower end is electrically connected to the
input of the electrical pod which is below the choke assembly.
[0063] The impedance offered by the choke is a critical
implementation issue, since this determines what proportion of
total power supplied to the pipe will be lost to leakage through
the choke, and what proportion will be available to power and
communicate with the devices installed in the isolated section of
the pipe. Since the impedance presented by an inductor increases
with frequency, the AC power frequency is used in both the
theoretical analysis and the testing of alternative choke
configurations, as this is normally equal to or lower than the
communication frequencies.
[0064] FIGS. 5a-d indicate the parameters used in the choke design
analysis. FIGS. 5a and 5b illustrate the case where the choke is
placed within the annulus 58 between the tubing 34 and the casing
36. FIGS. 5c and 5d illustrate an alternative case where the choke
is placed outside the casing 36. The basis for the analysis is the
same in both cases, but it is important to realize that the
electrical current value (I) used in the design analysis is the net
current linked by the choke. In the case where the choke is
disposed in the annulus 58 (FIGS. 5a and b), the current is that on
the tubing alone. When the choke is disposed external to the casing
(FIGS. 5c and 5d), the current is the vector sum of the separate
currents on the casing and tubing. Thus if these currents were to
be equal but opposite in phase there would be no net choking effect
with the configuration shown in FIGS. 5c and 5d.
[0065] The defining variables and a self-consistent set of physical
units are:
[0066] L=length of choke, meters;
[0067] a=choke inner radius, meters;
[0068] b=choke outer radius, meters;
[0069] r=distance from choke axis, meters;
[0070] I=r.m.s. net current through choked section, Amperes;
[0071] .omega. angular frequency of leakage current, radians per
second;
[0072] absolute magnetic permeability of choke material at radius
r, equal to the absolute permeability of free space
(4.pi..times.10.sup.-7 Henrys per meter) multiplied by the relative
permeability of the magnetic material of the choke.
[0073] By definition, .omega.=2.pi.f where f=frequency in
Hertz.
[0074] At a distance r from the current I, the r.m.s. free space
magnetic field H, in Henries per meter, is given by:
H=I/r
[0075] The field H is circularly symmetric about the choke axis,
and can be visualized as magnetic lines of force forming circles
around that axis.
[0076] For a point within the choke material, the r.m.s. magnetic
field B, in Teslas, is given by:
B=H =.mu.I/2.pi.r
[0077] The r.m.s. magnetic flux F contained within the choke body,
in Webers, is given by:
F=.intg.B dS
[0078] where S is the cross-sectional area of the choke in square
meters as shown in FIGS. 5a and 5c and the integration is over the
area S. Performing the integration from the inner radius of the
choke (a), to the outer radius of the choke (b), over the length of
the choke (L), we obtain:
F=.mu.LI ln(b/a)/2.pi.
[0079] where ln is the natural logarithm function.
[0080] The voltage generated by the flux F, ln Volts, is given
by:
V=.omega.F=2.pi.f F=.mu.LIf ln (b/a)
[0081] Note that the back-e.m.f. (V) is directly proportional to
the length (L) of the choke for constant values of (a) and (b), the
choke element internal and external radii. Thus by altering the
length of the choke, any desired back-e.m.f. can be generated for a
given current.
[0082] Inserting representative values:
.mu.=50,000.times.(4.pi..times.10.sup.-7), L=1 meter, I=10 Amperes,
f=60 Hertz,
[0083] a=0.045 meters (3.6 inch inner diameter), b=0.068 meters
(5.45 inch external diameter):
[0084] then the back-e.m.f. developed V=2.6 Volts
[0085] showing that such a choke is effective in developing the
required downhole voltage, and does so when realistic and safe
currents and voltages are impressed upon the tubing and transmitted
from the well head to downhole equipment.
[0086] FIG. 6 shows a petroleum well application of a second
embodiment in accordance with the present invention for a
multilateral completion. The second embodiment is similar to the
first embodiment in that the piping structure comprises the
production tubing 34 but the electrical return comprises the earth
72 and the casing 36. The main borehole 87 branches into four
laterals 88. The source 38 comprises a computer system having an AC
power source and a modem. As long as a time-varying current is
output to the electrical circuit, the source 38 may comprise any
variety of electronic components, including but not limited to: a
computer system, a modem, a power supply, a software program for
analyzing data, a software program for controlling downhole
devices, or any combination thereof. The source 38 is electrically
connected at a first end 41 of the main borehole 87 between an
upper choke or insulating tubing joint 30 and a lower choke 32. The
lower choke 32 is located at the downhole end of the main borehole
87, below the branch points of the laterals. The lower choke 32
routes the current flowing in the tubing 34 of the main borehole 87
into the tubing 34 in the branches 88. An additional choke 31 is
located within each lateral branch 88 (details of only two branches
shown). Current is directed through a device 40 and across the
voltage potential formed at each choke 31 within each lateral
branch 88. As shown in FIG. 6, the tubing 34 is electrically
connected to the earthen ground 72 at various places to complete
the circuit stemming from each choke (30, 31, 32).
[0087] Each device 40 comprises a control module 110, sensors 120,
a modem 122, an electric motor 124, and an electrically
controllable valve 126. The control module 110 receives power
and/or communications from the tubing 34, which it uses to provide
power, control, and communications for the sensors 120, modem 122,
and electric motor 124. The control module 110 can contain various
logic structures for closed loop control of the valve 126 based on
measurements taken by the sensors 120. In this example, there is a
pressure sensor, a temperature sensor, and a flow sensor. However,
other types of sensors 120 can also be used or substituted (e.g.,
acoustic sensor, chemical composition sensor). The modem 122 in the
device 40 can send data from the sensors 120 to the computer system
at the surface 64. Also, the modem 122 can receive control signals
from the computer system via the modem in the source 38. The
control module 110 provides power and control for the electric
motor 124, which is capable of operating with low current. The
electric motor 124 is used to open, close, or adjust the valve 126.
Each control module 110 for each lateral branch 88 can be
separately addressable, each sensor 120 can be separately
monitored, and each valve 126 can be independently operated. Hence,
using a system incorporating the third embodiment, each valve 126
in each lateral branch 88 can be electrically controlled to manage
the fluid flow from each lateral.
ALTERNATIVE EMBODIMENTS
[0088] It will be clear to those skilled in the art that the effect
of the chokes in offering an impedance to AC current flow can be
exploited in a variety of ways as alternative embodiments for the
provision and distribution of power along the metal structures of
wells.
[0089] FIGS. 7a and 7b illustrate an alternative configuration for
the power supply and communications circuits which would be used in
cases where a plurality of downhole pods 40 are needed. It will be
apparent that the configuration of FIG. 7a is based on the basic
configuration illustrated in FIGS. 1 and 2. The power and
communications connections from each pod 40 have an associated
choke 31, and the power and communication AC signals are in series
as shown in the equivalent circuit illustrated in FIG. 3. FIG. 7b
shows an alternative configuration where the tubing between uphole
choke or insulating tubing joint 30,and downhole choke 32, is a
common power supply and communications connection for all the pods
40 between devices 30 and 32. The power and communications signal
return connections are all made to the casing using a sliding
contactor 52 between each pod and the casing 36. Thus the power and
communications connections are in this case in electrical parallel,
as contrasted with the series connections of FIG. 7a. The parallel
configuration of FIG. 7b has the advantage that the voltages needed
to supply power to a plurality of downhole pods are not additive,
and thus the applied voltage at connector 44, needed to operate a
plurality of pods, will not exceed a safety limit, typically taken
as 24 Volts. The parallel configuration has the disadvantage that
the the annulus 58 must be cleared of conductive fluids 82 to a
level below the lowermost choke 32 as shown in FIG. 7b.
[0090] A combination of the configurations of FIGS. 7a and 7b is
possible, and a system that provides dynamic switching between the
embodiments of FIGS. 7a and 7b is shown in FIG. 7c. As shown in the
figure, the input to the pod power supply input transformer 111 is
connected through two switches 104 and 105. The settings of these
switches are controlled by commands sent from the surface and
received by the modem of the pod. The switches allow power routing
within the pod to be reconfigured. With the switches 104 and 105
set as indicated in FIG. 7c, the transformer 111 is powered from
the potential developed on tubing section above and below choke 32.
This state thus corresponds to the series connection for a pod as
illustrated in FIG. 7a. When switch 105 is set to to its other
state, power is routed to the input transformer 111 from the tubing
section 34 above the choke 32, but is returned to the casing 36
through switch 105 and the sliding contactor connection 52 to the
casing 36. This corresponds to the parallel power configuration of
FIG. 7b. Switch 104 is optional but is desirable in certain
applications, since it allows current to flow around the choke 32
when the switch is closed, and therefore in this state the choke
ceases to impede current flow in tubing 34, and thus allows this
current to flow without impediment to devices lower in the
well.
[0091] The ability to reconfigure power routing to multiple
downhole pods as shown in FIG. 7c may be applied, for instance, to
the unloading of a gas lift well where the casing/tubing annulus 58
is filled with conductive fluid at the start of unloading. In this
case, each downhole pod controls a gas lift valve as illustrated in
FIG. 2. Initially all the pods are set to the series power
configuration. As the unloading proceeds the conductive fluid level
is driven past each pod, which then becomes powered and
controllable. When the conductive fluid level has fallen below a
pod its switch 105 may be set to the parallel power configuration.
When the fluid level has passed the next pod in sequence downhole,
switch 104 may be configured to remove the current impeding effect
of the upper pod choke, and both pods then draw power from the
potential on the tubing developed by the action of the lower pod
choke. By this method, as the unloading sequence progresses, the
pods are progressively switched to parallel connection, and the
voltage required to be applied at the wellhead may be kept low,
which is desirable for the safety of personnel.
[0092] FIG. 8 shows an alternative embodiment of the present
invention, allowing power to be applied selectively to separate
zones within a well, where each zone may contain one or more
downhole pods. As an example, FIG. 8 illustrates a gas lift well
with a plurality of chokes 30, 31, 32, and associated downhole pods
40. As shown in the choke design analysis already described by
reference to FIGS. 5a-d, the effect of the choke in impeding AC
flow is dependent linearly on the frequency of the AC and the
length dimension of the choke (L), all other parameters being held
equal. In the well of FIG. 8, chokes 30 and 32 are designed and
constructed to impede current flow at low frequencies, for instance
60 Hertz, and chokes 31 are designed to effectively impede current
flow only at a significantly higher frequency, for instance 400
Hertz. Following the example given in the design analysis, this may
be accomplished by using 15 choke subsections (132 of FIG. 4b) for
chokes 30 and 32, but only 3 such choke subsections for chokes 31.
With such a disposition of choke sizes, 60 Hertz AC supplied from
the surface equipment 38 will energize only the lowest pod
associated with choke 32, since chokes 30 will develop insufficient
voltage on their associated tubing sections to energize their
associated pods. When the AC applied by surface equipment 38 is at
400 Hertz, all the pods will be energized, since all of the chokes
are able to develop sufficient potential on their associated tubing
section to activate their associated pods. In the case of the gas
lift well of FIG. 8 this may aid in the transition from the
unloading process to the production process. Since all the gas lift
valves are used during the unloading sequence, the AC supplied at
the wellhead is 400 Hertz during unloading. Only the lowermost
valve, associated with choke 32, is needed during production, so
when the unloading has been completed the AC power frequency may be
switched to 60 Hertz, so that only the lowermost pod and valve are
powered.
[0093] There exists a constraint on this zone power selection
method. Pods lower in the well must respond to lower applied AC
frequency, and pods higher in the well must respond to higher AC
frequency, so that the AC impeding effect of the upper chokes does
not significantly prevent power from flowing to the lower
chokes.
[0094] FIG. 9 shows a petroleum well application in accordance with
another embodiment of the present invention, where the chokes are
external to the casing. In this embodiment, the piping structure
used to carry the electrical current for the downhole device 40
comprises the casing 36, which is a conductive metal tubing in this
case, and the electrical return comprises the earthen ground 72.
Thus, in this embodiment, the chokes 30, 32 are located about the
casing 36 rather than being located only about the tubing 34 as in
the embodiments described previously. In this embodiment, the
current flows from the power source 38 to the casing 36 below the
upper choke 30, along the casing 36 to a first device terminal 51
(due to the upper choke 30), through the device 40 (due to a
voltage potential developed across the lower choke 32) to the earth
ground 72 via the casing 36 below the lower choke 32, and back to
the source 38 via the earthen ground 72 (and vice versa because
AC).
[0095] In the choke design analysis previously described with
reference to FIGS. 5c-d, current in both the casing 36 and the
tubing 34 is impeded by a choke such as 30 or 32 of FIG. 9 since
currents on both the casing and the tubing link the choke. The
tubing cannot be used as the current return path for power applied
to the casing since the magnetic fields from the supply and return
currents would balance within the chokes, which would become
ineffective. It is for this reason that that the ground return path
72 is necessary.
[0096] The potential developed on the casing across the choke 32 is
connected by electrical conductors 51 and 52 to power and
communicate with an instrument pod 40 located external to the
casing. Chokes 30, 32, and the instrument pod 40, are set in the
well with the casing and before the cement 70 is injected. As in
the previous embodiments the instrument pod 40 may provide
bidirectional communication through a modem to return data to the
surface from sensors to measure conditions such as formation
pressure, temperature, acoustic signals etc connected to pod 40,
and to accept control commands from the surface.
[0097] FIG. 10 shows a petroleum well application in accordance
with another embodiment of the present invention This embodiment
provides a means to divert power and/or communications signals into
the casing or liner of a lateral. Power and/or communications
signals are conveyed on the casing of the main well bore using the
same disposition of surface equipment as in FIG. 9. The main well
bore is furnished with upper and lower packers 56. Choke 32 is
external to the main wellbore casing 36. The electrical potential
developed in the casing by choke 32 acts to divert current and/or
communications signals from the main wellbore casing 36 onto the
casing or liner of the lateral 88. By this means power is made
available to pods 40 external to the lateral casing or liner using
the same method as the downhole pod illustrated in FIG. 9.
[0098] FIG. 11 shows a petroleum well application in accordance
with another embodiment of the present invention. This embodiment
provides an alternative means to route power and/or communications
signals to the casing or liner of a lateral 88. Power and/or
communications signals are supplied from the source at the surface
through an armored cable 140. The cable 140 is set within the
cement 70 between the casing 36 and the earth 72, and it is routed
outside of an upper choke 30. In this example, the upper choke 30
is at the second end 42 of the main borehole 87 just above the
lateral branch 88. However, upper choke 30 may be placed anywhere
along the casing 36 between the surface and the branch point 70 of
the lateral 88. An upper packer 142 in the main borehole 87 is
located between the upper choke 30 and the lateral branch 88, and
the upper packer 142 electrically connects the tubing 34 and casing
36. The tubing 34 and casing 36 above the upper choke 30
electrically lead back to the earthen ground 72. Because the cable
140 is electrically connected to the casing 36 below the upper
packer 142 and the upper choke 30, the current travels in the same
direction at any given time within both the tubing 34 and casing 36
at the upper choke 30. Hence, the upper choke 30 impedes current
from flowing through the tubing 34 and casing 36 at the upper
choke. Similarly, a lower packer 144 in the main borehole 87 is
located between the lateral branch 88 and a lower choke 32, and the
lower packer 144 electrically connects the tubing 34 to the casing
36. The tubing 34 and casing 36 also electrically lead to the
earthen ground 72 below the lower choke 32. Hence, the lower choke
32 impedes current from flowing through the tubing 34 and casing 36
at the lower choke. Thus, AC flowing through the cable 140 is
routed into the tubing 34 and casing 36 within the lateral branch
88. By this means power is made available to a pod external to the
lateral casing or liner using the same method as the downhole pod
illustrated in FIG. 9.
[0099] Many of the examples described thus far have focused on gas
lift petroleum wells. However, a rod pumping artificial lift or
"sucker rod" oil well may also incorporate the present invention.
FIGS. 12 and 13 show a petroleum well in accordance with another
embodiment of the present invention. In this embodiment, the piping
structure for carrying current to a device 40 downhole comprises a
pumping rod 100 of a rod pumping artificial lift oil well, and the
return is on the casing 36. If rod guides are required to prevent
the rod 100 from touching the casing, they must be electrically
insulating.
[0100] FIG. 14 illustrates an embodiment using the methods of the
present invention in the case where it is desired to locate the
surface power and communications equipment at a distance from the
well head. The power and communications elements located at the
central field facility 201 comprise collector tubing 234, a choke
230, an AC power source 248, the modem receiver represented by its
input impedance 212, and the modem transmitter represented by its
AC generator 214. One side of the power and modem elements is
connected to ground 72, and the other side is connected to the
collector tubing 234.
[0101] Referring still to FIG. 14, the collector tubing 234 extends
from the central facility 201 to the wellhead location 202. At the
wellhead the collector tubing is furnished with choke 230, and an
electrical cable 240 carries the power and communications AC
through the insulating feedthrough 276 to the production tubing
below the well upper choke. By this means the power and
communications ACs are not required to pass over the section of
production tubing where it passes into the well. In standard well
construction practice this section of the tubing 234 is
electrically connected to the casing 236 at the point where it
passes through the tubing hanger 254, and in this case the separate
electrical connection 240 is required. If non-standard construction
practice is acceptable, then the use of electrically isolating
tubing joints and feedthroughs may eliminate the need for the
separate conductor 240 and its associated chokes.
[0102] At depth 203 in the well, the production tubing 234 is
furnished with a choke 232 and an electrical pod 210. These
function as described in reference to FIGS. 1 and 2, with the
return connection from the downhole equipment being effected by the
downhole ground connection 72.
[0103] Even though many of the examples discussed herein are
applications of the present invention in petroleum wells, the
present invention also can be applied to other types of wells,
including but not limited to: water wells and natural gas
wells.
[0104] Also in a possible embodiment (not shown) of the present
invention, the piping structures of two adjacent wells can be used
to form a current loop for the electrical circuit. For example, a
second end of a piping structure of a first well may be
electrically connected (e.g., via a wire, conductive fluid, and/or
the earth) to a second end of a piping structure of a second well
adjacent to the first well, and a first end of the piping structure
of the first well is electrically connected to a first terminal of
a power source and a first end of the piping structure of the
second well is electrically connected to a second terminal of the
source, such that the electrical circuit is formed by using the
piping structures of both wells. Hence, one of the piping
structures will act as an electrical return. In another possible
embodiment (not shown), two piping structures of a same well (e.g.,
two adjacent lateral branches) can be used to form a current loop
for an electrical circuit. For example, the piping structure can be
a first lateral branch and the electrical return can be a second
lateral branch.
[0105] One skilled in the art will see that the present invention
can be applied in many areas where there is a need to provide power
and/or communication within a borehole, well, or any other area
that is difficult to access. As discussed above, a production
tubing string, as used in oil fields for withdrawing oil from a
reservoir, is an example of a well with limited access downhole.
Another example is the use of the present invention to provide
power and/or communications to a device within a borehole of a
machine part, where access within the borehole is limited. For
example, when looking for cracks in a steam turbine using
nondestructive testing techniques (e.g., ultrasonics, eddy
current), there is often a need to provide power and communications
to a sensor deep within a borehole of the steam turbine rotor that
may be three to six inches in diameter and thirty feet long. The
piping structure can comprise a rod or tube that physically
supports the sensor, and the electrical return can comprise the
machine part being inspected. Hence, the use of the present
invention can provide a system and method of providing power and
communications to a sensor deep within the borehole where access is
limited.
[0106] Also, one skilled in the art will see that the present
invention can be applied in many areas where there is an already
existing conductive piping structure and a need to route power
and/or communications in a same or similar path as the piping
structure. A water sprinkler system or network in a building for
extinguishing fires is an example of a piping structure that may be
already existing and having a same or similar path as that desired
for routing power and/or communications. In such case another
piping structure or another portion of the same piping structure
may be used as the electrical return. The steel structure of a
building may be used as an electrically conductive structure and/or
electrical return for transmitting power and/or communications in
accordance with the present invention. The steel reinforcing bar in
a concrete dam or a street pavement may be used as an electrically
conductive structure and/or electrical return for transmitting
power and/or communications in accordance with the present
invention. The transmission lines and network of piping between
wells or across large stretches of land may be used as a piping
structure and/or electrical return for transmitting power and/or
communications in accordance with the present invention. Surface
refinery production pipe networks may be used as a piping structure
and/or electrical return for transmitting power and/or
communications in accordance with the present invention. Thus,
there are numerous applications of the present invention in many
different areas or fields of use.
[0107] It will be appreciated by those skilled in the art having
the benefit of this disclosure that this invention provides a
system that uses at least one unpowered induction choke to form an
electrical circuit in a piping structure. It will also be
appreciated by those skilled in the art having the benefit of this
disclosure that this invention provides a system for providing
power and/or communications to a device downhole in a borehole of a
well using an electrical circuit formed in a piping structure by
using at least one unpowered induction choke. It should be
understood that the drawings and detailed description herein are to
be regarded in an illustrative rather than a restrictive manner,
and are not intended to limit the invention to the particular forms
and examples disclosed. On the contrary, the invention includes any
further modifications, changes, rearrangements, substitutions,
alternatives, design choices, and embodiments apparent to those of
ordinary skill in the art, without departing from the spirit and
scope of this invention, as defined by the following claims. Thus,
it is intended that the following claims be interpreted to embrace
all such further modifications, changes, rearrangements,
substitutions, alternatives, design choices, and embodiments.
* * * * *