U.S. patent application number 13/295784 was filed with the patent office on 2012-08-23 for system and method for remote sensing.
This patent application is currently assigned to Chevron U.S.A., Inc.. Invention is credited to David W. Beck, Manuel E. Gonzalez, M. Clark Thompson, Robert L. Williford.
Application Number | 20120211278 13/295784 |
Document ID | / |
Family ID | 45464825 |
Filed Date | 2012-08-23 |
United States Patent
Application |
20120211278 |
Kind Code |
A1 |
Gonzalez; Manuel E. ; et
al. |
August 23, 2012 |
SYSTEM AND METHOD FOR REMOTE SENSING
Abstract
A system, method and device may be used to monitor conditions in
a borehole. Well tubing and casing act as a conductive pair for
delivering power to one or more downhole active sensors. At the
surface, power and signal are isolated so that the same conductive
pair may act to transmit the sensor signals to the surface. In an
embodiment, the sensor signals are RF signals and the surface
electronics demodulate the RF signals from the sensor power.
Inventors: |
Gonzalez; Manuel E.;
(Kingwood, TX) ; Thompson; M. Clark; (Los Alamos,
NM) ; Williford; Robert L.; (Los Alamos, NM) ;
Beck; David W.; (Santa Fe, NM) |
Assignee: |
Chevron U.S.A., Inc.
San Ramon
CA
|
Family ID: |
45464825 |
Appl. No.: |
13/295784 |
Filed: |
November 14, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61413179 |
Nov 12, 2010 |
|
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Current U.S.
Class: |
175/40 |
Current CPC
Class: |
E21B 47/06 20130101;
E21B 47/12 20130101; E21B 47/13 20200501 |
Class at
Publication: |
175/40 |
International
Class: |
E21B 47/12 20120101
E21B047/12 |
Claims
1. A system for measuring a condition in a downhole environment in
a borehole beneath a surface, comprising: a source, configured and
arranged to transmit a power signal via a conductive line in the
borehole; a sensor module, in electrical communication with the
source via the conductive line, the sensor module comprising an
oscillator having a resonant frequency that varies with changes in
the condition in the downhole environment, the sensor module being
configured and arranged to receive power from the source and to
produce a sensor signal in response to the condition in the
downhole environment and to transmit the signal, via the conductive
line, toward the surface; and a detector, in electrical
communication with the sensor module via the conductive line and
configured and arranged to receive the sensor signal.
2. A system as in claim 1, further comprising: an upper
transformer; configured and arranged to receive the power signal
from the source, and to couple the power signal to the conductive
line, and to receive the sensor signal from the conductive line and
to couple the sensor signal to the detector; and a lower
transformer, configured and arranged to receive the power signal
from the conductive line and to couple the power signal to the
sensor module, and to receive the sensor signal from the sensor
module and to couple the sensor signal to the conductive line.
3. A system as in claim 1, further comprising: an upper insulator,
configured and arranged to electrically isolate a portion of the
conductive line from the surface; and a lower insulator, configured
and arranged to electrically isolate the portion of the conductive
line from a distal end of the conductive line, the upper insulator
and lower insulator defining respective ends of a conducting
portion of the conductive line for transmitting the power signal
and the sensor signal.
4. A system as in claim 1, wherein the sensor module further
comprises a power conditioning circuit.
5. A system as in claim 1, wherein the sensor module further
comprises a filter, constructed and arranged to separate the power
and data signals.
6. A system as in claim 5, wherein the filter comprises a low pass
filter, configured and arranged to pass the power signal, via a
power conditioning circuit, to the oscillator, and wherein the
sensor module further comprises: a frequency modulator, configured
and arranged to modulate the sensor signal for transmission to the
detector; and a high pass filter, configured and arranged to pass
the modulated sensor signal and to attenuate portions of the power
signal that would otherwise be transmitted to the detector.
7. A system as in claim 1, wherein the detector and the source
together comprise a surface system and wherein the surface system
further comprises a filter, constructed and arranged to separate
the power and data signals.
8. A system as in claim 7, wherein the filter comprises a low pass
filter, configured and arranged to pass the power signal from the
source to a power conditioning circuit and wherein the surface
system detector further comprises: an additional low pass filter,
configured and arranged to pass the power signal from the power
conditioning circuit to the conductive line and to attenuate
portions of the sensor signal that would otherwise be transmitted
to the power conditioning circuit; a high pass filter, configured
and arranged to attenuate the power signal and to pass the sensor
signal to a demodulator, the demodulator being configured and
arranged to demodulate the sensor signal and to pass the
demodulated sensor signal to the detector.
9. A system as in claim 1, further comprising a short circuit,
positioned in the borehole below the sensor module and connecting
the conductive line to a casing of the borehole.
10. A method of measuring a condition in a downhole environment in
a borehole beneath a surface, comprising: transmitting a power
signal via a conductive line in the borehole; receiving power from
the source at a sensor module comprising an oscillator having a
resonant frequency that varies with changes in the condition in the
downhole environment and positioned in the downhole environment;
transmitting a sensor signal from the sensor module toward the.
surface via the conductive line; detecting the sensor signal at the
surface; and splitting the power signal and the sensor signal
during the receiving and the detecting while allowing the power
signal and the sensor signal to travel a common path via the
conductive line during the transmitting.
11. A method as in claim 10, wherein the splitting the power signal
and the sensor signal comprises filtering the signals on the basis
of frequency.
12. A method as in claim 10, wherein the splitting the power signal
and the sensor signal comprises low pass filtering a combined power
and sensor signal prior to the transmitting the power signal.
13. A method as in claim 10, wherein the splitting the power signal
and the sensor signal comprises high pass filtering a combined
power and sensor signal prior to the detecting the sensor signal at
the surface.
14. A method as in claim 10, further comprising, isolating a
portion of the conductive line used in the transmitting with
respective insulating sub assemblies at a top of the portion and a
bottom of the portion.
15. A method as in claim 10, wherein the power and sensor signals
are coupled to the conductive line by a pair of transformers, one
transformer defining a top of a portion of the drillstring used in
the transmitting and the other transformer defining a bottom of the
portion.
16. A system as in claim 1, wherein the conductive line comprises a
drillstring.
17. A system as in claim 1, wherein the conductive line comprises
production tubing.
18. A method as in claim 10, wherein the conductive line comprises
a drillstring.
19. A method as in claim 10, wherein the conductive line comprises
production tubing.
Description
[0001] This application claims the benefit of U.S. Provisional
Patent Application 61/413,179, filed Nov. 12, 2010, which is
incorporated herein by reference in its entirety.
BACKGROUND
[0002] 1. Field
[0003] The present invention relates generally to remote sensing
and more particularly to sensing pressures and temperatures in a
down hole environment.
[0004] 2. Background
[0005] In resource recovery, it may be useful to monitor various
conditions at locations remote from an observer. In particular, it
may be useful to provide for monitoring temperatures and pressures
at depth in a borehole that has been drilled either for exploratory
or production purposes. Because such boreholes may extend several
miles, it is not always practical to replace power supplies for
sensors located in the borehole.
SUMMARY
[0006] An aspect of an embodiment of the present invention includes
an apparatus for monitoring conditions in a borehole. The well
tubing and casing act as a conductive pair for delivering power to
one or more downhole active sensors. At the surface, power and
signal are isolated so that the same conductive pair may act to
transmit the sensor signals to the surface.
[0007] An aspect of an embodiment of the present invention includes
a system for measuring a condition in a downhole environment in a
borehole beneath a surface, including a source, configured and
arranged to transmit a power signal via a drillstring in the
borehole a sensor module, in electrical communication with the
source via the drillstring, the sensor module comprising an
oscillator having a resonant frequency that varies with changes in
the condition in the downhole environment, the sensor module being
configured and arranged to receive power from the source and to
produce a sensor signal in response to the condition in the
downhole environment and to transmit the signal, via the
drillstring, toward the surface, and a detector, in electrical
communication with the sensor module via the drillstring and
configured and arranged to receive the sensor signal.
[0008] An aspect of an embodiment of the present invention includes
a system for monitoring conditions in a borehole. The well tubing
and casing act as a conductive pair for delivering power to one or
more downhole active sensors. At each of the surface and the
sensor, power and sensor signals are isolated so that the same
conductive pair may act to transmit the sensor signals to the
surface.
[0009] Another aspect of an embodiment of the present invention
includes a method of monitoring conditions in a borehole. A power
signal is transmitted via the drillstring to one or more downhole
active sensors. The sensor signal is transmitted via the
drillstring to the surface. At each of the surface and the sensor,
power and sensor signals are isolated.
[0010] Aspects of embodiments of the present invention include
tangible computer readable media encoded with computer executable
instructions for performing any of the foregoing methods and/or for
controlling any of the foregoing apparatuses or systems.
DESCRIPTION OF THE DRAWINGS
[0011] Other features described herein will be more readily
apparent to those skilled in the art when reading the following
detailed description in connection with the accompanying drawings,
wherein:
[0012] FIG. 1 is a schematic illustration of a system for
interrogating a downhole environment in a borehole beneath a
surface in accordance with an embodiment of the present
invention;
[0013] FIG. 2 is an electrical schematic diagram illustrating a
circuit configured to provide DC power to a sensor in a down hole
location and to accept input from the sensor for transmission to
the surface;
[0014] FIG. 3 is a schematic diagram illustrating an alternating
current embodiment of a transmission system for power and signal
for a remote sensor;
[0015] FIG. 4 is a schematic diagram illustrating a direct current
embodiment of a transmission system for power and signal for a
remote sensor;
[0016] FIG. 5 is a block diagram of a transformer coupling system
in accordance with an embodiment of the present invention;
[0017] FIG. 6 is a block diagram of a sensor module assembly in
accordance with an embodiment of the present invention;
[0018] FIG. 7 is a block diagram of a sensor module interface in
accordance with an embodiment of the present invention; and
[0019] FIG. 8 is a block diagram of an insulated system in
accordance with an embodiment of the present invention.
DETAILED DESCRIPTION
[0020] FIG. 1 illustrates an example of an apparatus 100 for
monitoring a condition in a subsurface borehole. The apparatus 100
includes an electromagnetically transmissive medium, such as a
conductive line 102, for conducting electromagnetic energy through
the borehole. It will be appreciated by those having ordinary skill
in that art that the conductive line 102 may take different forms
or embodiments, depending on the state of the borehole. Thus, for
example, the conductive line 102 may comprise a production tubing
string in a completed borehole or a drillstring in a borehole under
construction. Near the top of the conductive line 102, a
transformer 104 is provided to couple the conductive pipe to a
source of electromagnetic energy. Alternate coupling methods to the
transformer 104 may be employed. For example, the transmission line
may directly couple to a coaxial cable or any other suitable
cable.
[0021] In the example embodiment as shown, the transformer 104
includes a stack of ferrite rings 106, and a wire 108 wound around
the rings. The wire 108 includes leads 110 that may be coupled to a
signal generator 112 which may be configured to produce a pulsed or
a continuous wave signal, as necessary or desirable. The wire 108
may further be coupled to a receiver 114. The receiver 114 may be
embodied as a computer that includes a bus for receiving signals
from the apparatus 100 for storage, processing and/or display. In
this regard, the computer 114 may be provided with a display 118
which may include, for example, a graphical user interface.
[0022] The computer 114 may be programmed to process the received
sensor signals to provide a measure of the sensed characteristic.
The computer 114 may perform any desired processing of the detected
signal including, but not limited to, a statistical (e.g., Fourier)
analysis of the signal, a deconvolution of the signal, a
correlation with another signal or the like. Commercial products
are readily available and known to those skilled in the art that
can be used to perform any suitable frequency detection.
Alternately, the computer may be provided with a look-up table in
memory or in accessible storage, that correlates received modulated
signals to sensed conditions in the borehole.
[0023] In a typical drilling application, the borehole will be
lined with a borehole casing 120 which is used to provide
structural support to the borehole. This casing 120 is frequently
made from a conductive material such as steel, in which case it
will cooperate with the line 102 in order to form a coaxial
transmission line, and it is not necessary to provide any
additional conductive medium. Where the casing is not conductive, a
conductive sleeve (not shown) may be provided within the casing in
order to form the coaxial structure. In order to maintain a spacing
between the line 102 and the casing 120, the apparatus 100 may
include dielectric rings 122 disposed periodically along the
conductive line 102.
[0024] The spacers can, for example, be configured as insulated
centralizers which can be disks formed from any suitable material
including, but not limited to, nylon or polytetrafluoroethylene
(PTFE). Though the illustrated embodiment makes use of a coaxial
transmission line, it is contemplated that alternate embodiments of
a transmission line may be employed, such as a single conductive
line, paired conductive lines, or a waveguide. For example, the
casing alone may act as a waveguide for certain frequencies of
electromagnetic waves. Furthermore, lengths of coaxial cable may be
used in all or part of the line. Such coaxial cable may be
particularly useful when dielectric fluid cannot be used within the
casing 120 (e.g., when saline water or other conductive fluid is
present in the casing 120).
[0025] A probe portion 124 is located near the distal end of the
apparatus 100. In principle, the probe portion may be located at
any point along the length of the transmission line. Indeed,
multiple such probe portions may be placed at intervals along the
length. In principle, wavelength multiplexing on the coaxial line
could be used to allow for multiple probes to use a single
communication line without interfering with each other.
[0026] The probe portion may include a port 126 that is configured
to communicate ambient pressures and/or temperatures from fluid
present in the borehole into the probe where it may be sensed by
the sensor (not shown in FIG. 1). Below the probe is illustrated a
packer 128 and packer teeth 130.
[0027] FIG. 2 is an electrical schematic illustrating a down hole
portion of an embodiment of the system in accordance with the
invention. An RC terminator 200 is intended to reduce or eliminate
reflections at the line end. From the line end, the path of the
power signal depends on whether it is a DC or an AC signal. Applied
DC will take the upper path 202 through the high inductance
inductor 204 (which may be, for example, about 1 mH) and pass
through diode 206, arriving at the DC power out 208 at the right of
the Figure. On the other hand, applied AC will pass through the
relatively lower inductance inductor 212 (which may be, for
example, about 17 .mu.H). The AC energy passes through a power
transformer 214 and a bridge rectifier 216 to produce DC power at
the same DC power out portion of the circuit 208. The sensors
produce a signal (generally an RF signal) that is accepted at the
RF sensor input portion of the circuit 218 and coupled back to the
conductive pair for transmission to the surface.
[0028] The inventors have determined that an electrically isolated
wellstring would enable better matching of the wellstring impedance
with regard to an RF signal being propagated. Additionally, and
concurrently, such an isolator would enable the transmission of AC
and DC power along the tubing to power functions deeper in the
well. A passive power switching method and apparatus allows
selective application of power to down hole circuits and loads.
[0029] The physical implementation of a (DC) wellstring isolator
generally requires robust mechanical components, which, when
combined into the assembly, can reliably support up to 200,000
pounds of wellstring tubing, withstand severe coupling torques, and
withstand chemical and environmental abuse.
[0030] In theory, an isolator may be nothing more than a dielectric
break in an otherwise solid piece of tubing. In actual practice,
such an isolator needs to fit within well casings with sufficient
clearance, exhibit low end-to-end capacitance, be able to standoff
many hundreds of volts of applied potential, and perhaps most
importantly, be received by wellsite managers with confidence that
it will not fail. Built-in failsafe design features may also be
useful, or required for acceptance by users.
[0031] In accordance with an embodiment of the invention, a
technique for DC isolation includes a ceramic or other
non-conductive insulator inserted in series with well tubing. This
may be, for example, built-in to a 4 foot section of tubing,
commonly referred to as a "sub".
[0032] The ceramic and tubing parts may be clamped together and
should be connected without electrically shorting the tubing parts
together. An insulating coating may be applied to the internal and
external surfaces of the assembly as electrical breakdown
protection across the gap.
[0033] In an embodiment, the RF (sensor signal) and DC (power)
connection is made to the tubing thru a common connection, with
signal separation handled electronically outside the well.
[0034] Multiple mechanical topologies have been drawn and built.
Many have exhibited values of electrical resistance too low for
practical use. In practice, isolation values of 2,000 ohms or
greater have proven useful.
[0035] An example of a set-up in accordance with an embodiment of
the invention is schematically illustrated in FIG. 3. In the
example of FIG. 3, the power signal generated at the surface is an
AC signal delivered to input 300. The AC signal is coupled into the
conductor pair via power cores 302 which may be of the ferrite
transformer type described above in relation to FIG. 1. FIG. 4
illustrates an alternate approach in which the power signal is a DC
signal.
[0036] As can be seen from FIGS. 3 and 4, a primary difference is
the use of a transformer which may be, for example, a toroidal
transformer made with tape wound cores on the wellstring tubing
just below the wellhead and above a set of RF ferrite cores 304. In
this approach, a small number of turns make up the primary of the
transformer, with the well tubing making up the secondary winding
of the transformer. In an example, it may be a single turn
secondary winding. The sensor module 310 and bowspring centralizer
312 used in the DC isolator approach remains unchanged in such an
AC application.
[0037] In this manner, the power signals generated by power supply
318 are provided to the sensor module 310 from the lower
transformer 304. In the reverse direction, the sensor module 310
generates communication signals that are transmitted to the lower
transformer 304. The communication signals are conducted up the
tubing string to the upper transformer 302 and then transmitted to
the receiver 320 of the surface system 500 (as illustrated in FIG.
5). The electrical path is completed by grounding the tubing string
on unused sides of the upper and lower transformers and by
grounding the surface system and sensor module 310. In practice,
the casing is generally grounded. Thus, the tubing string above the
upper transformer may be grounded by coupling the tubing string to
the casing through the wellhead. The tubing string below the lower
transformer 304 may be grounded by connecting the tubing string to
the casing via the bowspring centralizer 312, for example.
[0038] In an embodiment, the transformers are formed by formed by
using the tubing string as one of the windings of each transformer.
For example, at the upper transformer, the power signal from the
surface system is transmitted to the primary winding of a toroidal
transformer positioned around the tubing string. The tubing string
itself is the single turn secondary winding of the transformer for
the power circuit. Similarly, the lower transformer is another
toroidal transformer surrounding the tubing string and includes,
for the power circuit, a primary winding that is the tubing string
itself and a secondary winding that is connected to the sensor
module 310. In the communication circuit, signals are transmitted
using the same transformers, though (as compared to the power
circuit) the roles of the primary and secondary windings in each
transformer are reversed.
[0039] In an embodiment, the technique for AC isolation includes an
isolator built-up on a short section of steel tubing, incorporating
AC and RF magnetics. Separate AC and RF electrical connections
(300, 314 respectively) may be made through a wellhead hanger 316.
A suitable impedance for the RF signal may be established by
selection of the RF magnetic material. A suitable impedance for the
AC source may be established by selection of the AC transformer
characteristics.
[0040] In this approach, the RF impedance, established by the RF
magnetics, is also affected by the presence of the AC magnetics,
which represent a very high impedance to the RF. As such, it may be
necessary to provide an electrical path around the AC magnetics to
the wellhead for the RF currents travelling up the wellstring from
the sensor package 310. In that case, two different electrical
connections to the wellhead would be required.
[0041] In practice the power frequencies may be between 5 kHz and
200 kHz, for example. On the other hand, the RF frequencies for
data may be between 3 MHz and 8 MHz. In an embodiment, power is
supplied in a range between 1 and 10 kHz and data is transmitted
using a frequency-shift keying modulation scheme at frequencies in
the range between 15 and 30 kHz. Power frequencies above the RF
range are, in theory, usable. Sensor data frequencies may also be
selected outside the foregoing ranges. Because the transmission
frequencies of the power and sensor signals are different, it is
possible to separate them using filtering at either the surface
system 500 and/or at the sensor module 310.
[0042] As a result of the transformer-based power and communication
transmission via the drill string, there may be no need for current
limiting or directing devices (i.e. devices to ensure current flows
either up or down the tubing). Because there is no requirement for
directing power and data transmission along the tubing string, it
tends to be less susceptible to attenuation than it would if
current directing devices were required. This, in turn, allows for
the use of low-power (e.g., less than <10V) sensors in the
sensor module. These low power sensors enable the system as a whole
to tolerate significant attenuation between the power source and
the downhole sensors.
[0043] FIG. 6 is a block diagram of a sensor module 600 assembly in
accordance with an embodiment of the present invention. As will be
appreciated the sensor module 600 is similar to the arrangement
illustrated in FIG. 2 and represents an alternate approach to
illustrating similar concepts.
[0044] The sensor module 600 connects to the lower transformer by
way of a bus 602 that carries both the power signal and the sensor
data signal. A low pass filter 604 passes the low frequency power
signal to the sensor module power circuitry which is made up of a
transformer 606, a rectifier 608, and a voltage regulator 610.
Power is supplied to a microprocessor 612 and to one or more
digital gauges 614, each of which may be, for example, a
Quartzdyne.RTM. gauge, available from Quartzdyne, Inc. of Salt Lake
City, Utah. Such gauges constitute a quartz resonator and are often
packaged along with an accompanying oscillator circuit and
processor (e.g., frequency counter), and may include reference and
temperature crystals along with their respective oscillator
circuitry.
[0045] Output from the gauges 614 is provided to the processor 612
which processes the data and outputs a communication signal through
a frequency modulator 616. The communication signal is passed back
to the tubing string by way of the bus 602 and the lower
transformer. A high pass filter 618 (which may be a capacitor), in
conjunction with the low pass filter 604, isolates the
communication signal from the power pathway.
[0046] A portion of the surface system 500 that acts as a gauge
interface module is shown in block diagram form in greater detail
in FIG. 7. A bus 702 communicates with the upper transformer 302. A
serial input 704 obtains power from a power supply, not shown. An
MPU 706 manages the input power and outputs the power by way of a
low pass filter 708, digital attenuator 710, and power amplifier
712. A power monitor 714 senses the output power and returns data
on the sensed power to the MPU 706. A second low pass filter 716,
which in the illustrated embodiment is an inductor, passes the
power signal to the bus 702 and excludes the higher frequency data
signals that are being returned from the sensor module. The data
signals instead pass through a high pass filter 718 to a
demodulator 720 and thence to the MPU 706. Output from the MPU may
be passed via an Ethernet connection 722, or other type of
connection.
[0047] FIG. 8 is a block diagram illustrating an arrangement
similar to that illustrated in FIG. 4 and represents an alternate
approach to illustrating similar concepts. As described above, this
approach makes use of ceramic insulated tubing subs in order to
isolate a portion of the tubing. One insulating sub forms the upper
isolator 319 while another forms the lower isolator 321. An
intermediate tubing portion 802 becomes the transmission line for
signals and power in the system. Similarly to the transformer
embodiment, the tubing string conducts power signals from a
connection point located just below the upper ceramic insulated
tubing sub (upper insulator 319) to a connection point located just
above the lower ceramic insulated tubing sub (lower insulator 321).
The power signals are provided to a sensor module/gauge assembly
310 from the connection point located just above the lower
insulator 321. In the reverse direction, the sensor module 310
generates communication signals that are transmitted to the
connection point located just above the lower insulator 321. The
communication signals are conducted up the tubing string to the
connection point located just below the upper insulator 319 and
then transmitted to the surface system 500. The electrical path is
completed by grounding the tubing string above the upper ceramic
insulated tubing sub and below the lower ceramic insulated tubing
sub and by grounding the surface system and sensor module. In
practice, the casing is generally grounded. Thus, the tubing string
above the upper ceramic insulated tubing sub may be grounded by
coupling the tubing string to the casing through the wellhead. The
tubing string below the lower ceramic insulated tubing sub may be
grounded by connecting the tubing string to the casing via a
bowspring shorting centralizer, for example.
[0048] In an experimental test, the inventors arranged up to
17,000' of coaxial cable that matched the losses of a field test
(i.e., simulated the depth of a typical deep well). A remote
full-wave AC power rectifier/filter was provided at the end of the
cable to provide DC power to amplify the sensor signal.
[0049] A low frequency 60 hertz AC voltage was transmitted down the
cable. It provided about 10 volts DC (out of the rectifier/filter)
at the cable terminus. An amplified sensor signal (frequency peak)
was received at the surface using an HF radio detector. This setup
allowed receipt of over 120 readings per second at the surface.
[0050] In an embodiment, parameters such as pressure or temperature
are measured (singularly or simultaneously) at great depth using
the well string hardware as both the path to power the sensors (and
other associated devices), and to transport data signals from the
sensors. As such, this technique uses the same conduction system
for both electrical power and the signal path for the parameter
data. Applied power can be DC and/or AC power at various
frequencies to accommodate a multitude of lower powered remote
functions or higher powered uses including artificial lifting
systems (pumps).
[0051] This technique uses the well tubing and casing as a
conductive pair (CP) to carry the power down to the remote, powered
sensor set or associated devices. This is accomplished with a
magnetic core (transformer like) AC coupler or an insulated tubing
member 319 just below the tubing string hanger (at the surface) and
a similar insulated tubing member 321 near the terminal end of the
tubing string for a DC application. The tubing is maintained on
center of the well-casing with annular insulator spacers
("centralizers") such that the conductive pair (tubing and casing)
do not electrically short to each other. At the end of the tubing
string, below the lower insulated tubing member there should be a
conductive "packer" or bow-spring centralizer 312 or other
mechanism to make contact with the casing to complete the
circuit.
[0052] As will be appreciated, by up-hole electronic
separation/isolation of power and signal, this same conductor pair
can perform as the path to the wellhead for processing of the data
from the sensor set. Those familiar with the art will understand
selective frequency filtering methods used here to separate power
from signal and function from function. This process uses sensors
that translate the parameter of interest to a low power Radio
Frequency (RF) transmitter. The carrier of each transmitter is
modulated to provide the imbedded data to surface level
instrumentation. The RF carrier is then demodulated at the surface
electronics for use.
[0053] A second use of the CP arrangement of the well hardware
described herein is to power an electrical submersible pump (ESP)
system for artificial lifting of fluids in the producing zones.
Electrical power sent to the ESP, via the tubing string, can be
used to power attached sensor systems with the signals from those
sensors using the same CP as the RF path back to surface
instruments.
[0054] In an embodiment, methods for commanding various functions
down-hole might be accomplished by selecting a specific power
frequency that would perform various separate remote operations
(i.e. multiple zone valve control, etc.) by using resonant,
frequency selective networks at the remote valve location.
[0055] Those skilled in the art will appreciate that the disclosed
embodiments described herein are by way of example only, and that
numerous variations will exist. The invention is limited only by
the claims, which encompass the embodiments described herein as
well as variants apparent to those skilled in the art. In addition,
it should be appreciated that structural features or method steps
shown or described in any one embodiment herein can be used in
other embodiments as well.
* * * * *