U.S. patent application number 14/890004 was filed with the patent office on 2016-06-16 for multiple-depth eddy current pipe inspection with a single coil antenna.
This patent application is currently assigned to Halliburton Energy Services, Inc.. The applicant listed for this patent is Halliburton Energy Services, Inc.. Invention is credited to Burkay Donderici, Luis Sanmartin.
Application Number | 20160168975 14/890004 |
Document ID | / |
Family ID | 55064688 |
Filed Date | 2016-06-16 |
United States Patent
Application |
20160168975 |
Kind Code |
A1 |
Donderici; Burkay ; et
al. |
June 16, 2016 |
MULTIPLE-DEPTH EDDY CURRENT PIPE INSPECTION WITH A SINGLE COIL
ANTENNA
Abstract
A method includes introducing a pipe inspection tool into a
first pipe positioned within a wellbore and further positioned
within at least a second pipe. The pipe inspection tool includes an
electromagnetic sensor having a coil antenna that includes a coil
winding extending axially along at least a portion of the
electromagnetic sensor. An excitation signal is transmitted between
a first terminal and a second terminal of the coil antenna. A first
response signal is measured between a third terminal and a fourth
terminal of the coil antenna, wherein at least one of the third and
fourth terminals is different from the first and second terminals.
The first response signal is then processed to determine a
characteristic of the first pipe.
Inventors: |
Donderici; Burkay; (Houston,
TX) ; Sanmartin; Luis; (Houston, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Halliburton Energy Services, Inc. |
Houston |
TX |
US |
|
|
Assignee: |
Halliburton Energy Services,
Inc.
Houston
TX
|
Family ID: |
55064688 |
Appl. No.: |
14/890004 |
Filed: |
June 25, 2015 |
PCT Filed: |
June 25, 2015 |
PCT NO: |
PCT/US15/37631 |
371 Date: |
November 9, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62023490 |
Jul 11, 2014 |
|
|
|
Current U.S.
Class: |
324/238 |
Current CPC
Class: |
G01B 7/10 20130101; G01V
3/28 20130101; G01N 27/90 20130101; E21B 47/007 20200501; E21B
47/092 20200501; E21B 47/00 20130101 |
International
Class: |
E21B 47/00 20060101
E21B047/00; G01N 27/90 20060101 G01N027/90 |
Claims
1. A method, comprising: introducing a pipe inspection tool into a
first pipe positioned within a wellbore and further positioned
within at least a second pipe, the pipe inspection tool including
an electromagnetic sensor having a coil antenna that includes a
coil winding extending axially along at least a portion of the
electromagnetic sensor; transmitting an excitation signal between a
first terminal and a second terminal of the coil antenna; measuring
a first response signal between a third terminal and a fourth
terminal of the coil antenna, wherein at least one of the third and
fourth terminals is different from the first and second terminals;
and processing the first response signal to determine a
characteristic of the first pipe.
2. The method of claim 1, wherein transmitting the excitation
signal comprises transmitting a time-domain or frequency-domain
(steady-state) signal generated by a power source
electrically-coupled to the first and second terminals.
3. The method of claim 1, wherein measuring the first response
signal between the third terminal and the fourth terminal comprises
receiving the first response signal with a receiver
electrically-coupled to at least one of the third and fourth
terminals and included in the electromagnetic sensor.
4. The method of claim 1, further comprising: measuring a second
response signal between a fifth terminal and a sixth terminal of
the coil antenna, where an axial length of the coil antenna between
the fifth and sixth terminals is longer than an axial length of the
coil antenna between the third and fourth terminals; and processing
the first and second response signals to determine a characteristic
of one or both of the first and the second pipes.
5. The method of claim 1, wherein an axial length of the coil
antenna between the third and fourth terminals is longer than an
axial length of the coil antenna between the first and second
terminals, the method further comprising processing the first
response signal to determine a characteristic of the second
pipe.
6. The method of claim 1, wherein the coil winding is wound about a
segmented core comprising a plurality of core segments.
7. The method of claim 6, wherein each core segment exhibits an
axial length and is axially separated from an adjacent core by a
gap, and wherein the gap is at least one-fifth or more of the axial
length of each adjacent core segment.
8. A method, comprising: introducing a pipe inspection tool into a
first pipe positioned within a wellbore and further positioned
within at least a second pipe, the pipe inspection tool including
an electromagnetic sensor having a coil antenna that includes a
coil winding extending axially along at least a portion of the
electromagnetic sensor; transmitting a first excitation signal
between a first terminal and a second terminal of the coil antenna;
measuring a first response signal between the first and second
terminals; transmitting a second excitation signal between a third
terminal and a fourth terminal of the coil antenna, where the third
and fourth terminals are different from the first and second
terminals; measuring a second response signal between the third and
fourth terminals; and processing the first and second signals to
determine a characteristic of one or both of the first and second
pipes.
9. The method of claim 8, wherein transmitting the first excitation
signal comprises transmitting a first time-domain or
frequency-domain (steady-state) signal generated by a first power
source electrically-coupled to the first and second terminals, and
wherein transmitting the second excitation signal comprises
transmitting a second time-domain or frequency-domain
(steady-state) signal generated by a second power source
electrically-coupled to the third and fourth terminals.
10. The method of claim 8, wherein measuring the first response
signal between the first terminal and the second terminal comprises
receiving the first response signal with a first receiver
electrically-coupled to the first and second terminals and included
in the electromagnetic sensor, and wherein measuring the second
response signal between the third terminal and the fourth terminal
comprises receiving the second response signal with a second
receiver electrically-coupled to the third and fourth terminals and
included in the electromagnetic sensor.
11. The method of claim 8, wherein the coil winding is wound about
a segmented core comprising a plurality of core segments.
12. The method of claim 11, wherein each core segment exhibits an
axial length and is axially separated from an adjacent core by a
gap, and wherein the gap is at least one-fifth or more of the axial
length of each adjacent core segment.
13. A method, comprising: introducing a pipe inspection tool into a
first pipe positioned within a wellbore and further positioned
within at least a second pipe, the pipe inspection tool including
an electromagnetic sensor having a coil antenna that includes a
coil winding extending axially along at least a portion of the
electromagnetic sensor; transmitting a first excitation signal
between a first terminal and a second terminal of the coil antenna;
measuring a first response signal between the first and second
terminals; measuring a second response signal between the second
terminal and a third terminal of the coil antenna; summing the
first and second response signals to obtain a summed response
signal indicative of a measurement between the first and third
terminals; and processing the summed response signal to determine a
characteristic of at least one of the first and second pipes.
14. The method of claim 13, further comprising: subtracting the
first and second response signals to obtain a difference response;
and processing the difference response to determine the
characteristic of at least one of the first and second pipes.
15. The method of claim 13, wherein transmitting the excitation
signal comprises transmitting a time-domain or frequency-domain
(steady-state) signal generated by a power source
electrically-coupled to the first and second terminals.
16. The method of claim 13, wherein measuring the first response
signal between the first terminal and the second terminal comprises
receiving the first response signal with a first receiver
electrically-coupled to the first and second terminals and included
in the electromagnetic sensor, and wherein measuring the second
response signal between the second terminal and the third terminal
comprises receiving the second response signal with a second
receiver electrically-coupled to the second and third terminals and
included in the electromagnetic sensor.
17. The method of claim 13, wherein the coil winding is wound about
a segmented core comprising a plurality of core segments.
18. The method of claim 17, wherein each core segment exhibits an
axial length and is axially separated from an adjacent core by a
gap, and wherein the gap is at least one-fifth or more of the axial
length of each adjacent core segment.
19. A method, comprising: introducing a pipe inspection tool into a
first pipe positioned within a wellbore and further positioned
within at least a second pipe, the pipe inspection tool including
an electromagnetic sensor having a coil antenna that includes a
coil winding extending axially along at least a portion of the
electromagnetic sensor; selecting a number of consecutive terminals
on the coil antenna; transmitting an excitation signal between each
neighboring terminal of the consecutive terminals of the coil
antenna; receiving and recording a corresponding response signal
for each excitation signal between each neighboring terminal;
adding a subset of the response signals for each excitation signal
between any two terminals of the number of consecutive terminals to
obtain a synthesized signal; and processing the synthesized signal
to determine a characteristic of at least one of the first and
second pipes.
20. The method of claim 19, further comprising: combining the
subset of the response signals for each excitation signal between
any two terminals by one of addition, subtraction, or a weighted
sum, where weights of the weighted sum are positive or negative
numbers; and processing the synthesized signal to determine the
characteristic of at least one of the first and second pipes.
21. The method of claim 19, wherein the coil winding is wound about
a segmented core comprising a plurality of core segments.
22. The method of claim 21, wherein each core segment exhibits an
axial length and is axially separated from an adjacent core by a
gap, and wherein the gap is at least one-fifth or more of the axial
length of each adjacent core segment.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims priority to U.S. Provisional
Patent App. Ser. No. 62/023,490, filed on Jul. 11, 2014.
BACKGROUND
[0002] Wellbores in the oil and gas industry are typically drilled
using a drill string with a drill bit secured to its distal end.
The drilled wellbore is subsequently completed by cementing a
string of metal pipes connected end-to-end within the wellbore.
Commonly called "casing," such strings of metal pipes increase the
integrity of the wellbore and provide a flow path between the
earth's surface and selected subterranean formations. Moreover, in
some wellbores, one or more production pipes are extended into the
wellbore to provide a conduit for hydrocarbons to be conveyed to
the earth's surface. Accordingly, as used herein, the term "pipe"
or "wellbore pipe" will refer to metal pipes or pipelines that line
the walls of a wellbore, such as casing, and also production pipes
extended into a wellbore to facilitate hydrocarbon production
operations.
[0003] During the lifetime of a well, wellbore pipes are exposed to
high volumes of materials and fluids required to pass through them,
including chemically aggressive fluids. In harsh environments,
however, the pipes may be subject to corrosion that may affect
their functionality. Timely and accurate detection of structural
integrity problems such as cracks, pinholes, and corrosion is
essential to reducing costs associated with wellbore intervention,
since pulling wellbore pipes, such as casing, out of a wellbore for
further inspection and repairs and replacing can be a very
expensive task.
[0004] Some wellbores include multiple concentric pipes or strings
of casing secured within the wellbore with an innermost pipe that
exhibits a relatively narrow diameter. As will be appreciated, the
diameter of the innermost pipe limits the size of the monitoring
and intervention system that can be deployed to monitor the
integrity of all of the concentric pipes. With multiple concentric
pipes, another problem is the ability to effectively monitor the
outermost pipes from the innermost pipe, since any monitoring
system has to be able to sense through a number of pipe layers,
each of which may have developed distinct problems or defects.
[0005] Several different sensing methods have been proposed for
detecting corrosion and other types of defects in pipelines, some
of which have been applied to wellbore pipes used for extracting
hydrocarbons. The most common method utilizes acoustic wave pulses
and analysis of reflections from the surface of a pipe wall to
image any defects. Electromagnetic inspection methods are also used
for the same purpose, and are desirable since they allow an
operator to sense beyond the first pipe, and thereby obtain
measurements from second, third, or additional pipes beyond the
third pipe. Existing pipe inspection methods, however, are either
azimuthally sensitive and shallow or azimuthally insensitive and
deep.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] The following figures are included to illustrate certain
aspects of the present disclosure, and should not be viewed as
exclusive embodiments. The subject matter disclosed is capable of
considerable modifications, alterations, combinations, and
equivalents in form and function, without departing from the scope
of this disclosure.
[0007] FIG. 1 is a schematic diagram of an exemplary wireline
system that may employ the principles of the present
disclosure.
[0008] FIG. 2 is a partial cross-sectional side view of an
exemplary pipe inspection tool suspended within a wellbore.
[0009] FIG. 3 is a schematic flowchart of an exemplary method of
operating the electromagnetic sensor of FIG. 2.
[0010] FIG. 4 is a schematic flowchart of another exemplary method
of operating the electromagnetic sensor of FIG. 2.
[0011] FIG. 5 is a partial cross-sectional side view of another
exemplary pipe inspection tool suspended within a wellbore.
[0012] FIG. 6 is a schematic flowchart of an exemplary method of
operating the electromagnetic sensor of FIG. 5.
[0013] FIG. 7 is a schematic flowchart of another exemplary method
of operating the electromagnetic sensor of FIG. 5.
[0014] FIG. 8 is a partial cross-sectional side view of another
exemplary pipe inspection tool suspended within a wellbore.
[0015] FIG. 9 is a schematic flowchart of an exemplary method of
operating the electromagnetic sensor of FIG. 8.
[0016] FIG. 10 is a partial cross-sectional side view of another
exemplary pipe inspection tool suspended within a wellbore.
[0017] FIG. 11 is a schematic flowchart of an exemplary method of
operating the electromagnetic sensor of FIG. 10.
[0018] FIG. 12 is a schematic diagram of processing response
signals as voltages.
[0019] FIG. 13 is a schematic diagram of another embodiment of the
electromagnetic sensor of FIG. 10.
[0020] FIG. 14 is a block diagram of an exemplary data acquisition
and control system used for monitoring pipes in a wellbore.
[0021] FIG. 15 is a schematic flowchart of a method of converting
measurement data into one or more pipe characteristics.
DETAILED DESCRIPTION
[0022] The present disclosure is related to maintenance of
wellbores in the oil and gas industry and, more particularly, to
monitoring and evaluating corrosion in wellbore pipes with a pipe
inspection tool having a single coil antenna.
[0023] Embodiments described herein provide improved
electromagnetic inspection methods of wellbore pipes, such as
casings and production tubings. The presently described methods
rely on multiple excitation points and multiple measurement points
on the same coil winding of a coil antenna, which can achieve
variable or selective depth of investigation. While existing eddy
current inspection methods utilize z-coils that have multiple coil
antennas for achieving different depths of investigation, the
embodiments of the present disclosure use multiple terminals on a
single coil antenna to achieve the same result. Exemplary
characteristics of the wellbore pipes that may be measured include,
but are not limited to, thickness, magnetic permeability,
conductivity, and diameter. Such measurements may advantageously
provide an operator with an indication of defects on the wellbore
pipes. For example, a reduction in the thickness of a pipe can be
interpreted as metal loss or corrosion.
[0024] Moreover, according to the present disclosure, in order to
minimize cross-coupling between measurements without significantly
reducing signal strength, a ferrite core about which the coil
antenna is wound may be subdivided into multiple segments or
portions. The resulting response signals with the segmented core
can be decoupled using a special calibration on the measured
current or voltage that can be calculated using a data acquisition
and control system. In addition, a hardware or software control
could be employed to adjust the currents to achieve independent
measurements.
[0025] FIG. 1 is a schematic diagram of an exemplary wireline
system 100 that may employ the principles of the present
disclosure, according to one or more embodiments. As illustrated,
the wireline system 100 may include a surface platform 102
positioned at the earth's surface and a wellbore 104 that extends
from the surface platform 102 into one or more subterranean
formations 106. In other embodiments, such as in offshore
operations, a volume of water may separate the surface platform 102
and the wellbore 104. The wellbore 104 may be lined with one or
more pipes 108, also referred to as strings of casing. In some
embodiments, portions of the wellbore 104 may have only one pipe
108 positioned therein, but other portions of the wellbore 104 may
be lined with two or more concentrically-disposed pipes 108. The
pipes 108 may be made of plain carbon steel, stainless steel, or
another material capable of withstanding a variety of forces, such
as collapse, burst, and tensile failure.
[0026] The wireline system 100 may include a derrick 110 supported
by the surface platform 102 and a wellhead installation 112
positioned at the top of the wellbore 104. A pipe inspection tool
114 may be suspended into the wellbore 104 on a cable 116. In some
embodiments, the pipe inspection tool 114 may alternatively be
suspended within a production pipe (not shown) positioned within
the pipes 108 that line the wellbore 104 (i.e., casing). In such
embodiments, the production pipe may extend by itself within the
pipes 108 or alternatively be positioned adjacent one or more
eccentrically-located production pipes that are also positioned
within the pipes 108. Accordingly, as used herein, "pipes 108" may
refer to strings of casing that line the wellbore 104 and/or at
least one production pipe extended into the wellbore 104.
[0027] The pipe inspection tool 114 may comprise an
electromagnetic, non-destructive inspection tool. Its operation may
be based on either the flux-leakage principle or the eddy-current
principle, or a combination thereof, and may be insensitive to
non-conductive deposits and is operable irrespective of the nature
of the fluid mixture flowing into/out of the wellbore 104. The pipe
inspection tool 114 can be used for the detection of localized
damage or defects in the pipes 108. In operation, the pipes 108 are
subjected to a strong static magnetic field generated by the pipe
inspection tool 114 and, due to their ferromagnetic nature, the
magnetic return flux is mainly confined to the inside of the pipes
108. In the presence of discontinuities or defects in the metal of
the pipes 108, such as pits and holes caused by corrosion, the
changes in the magnetic field can be detected with the pipe
inspection tool 114.
[0028] To accomplish this, the pipe inspection tool 114 may include
one or more electromagnetic sensors 118, which may be communicably
coupled to the cable 116. The cable 116 may include conductors for
conveying power to the pipe inspection tool 114 and also for
facilitating communication between the surface platform 102 and the
pipe inspection tool 114. A logging facility 120, shown in FIG. 1
as a truck, may collect measurements from the electromagnetic
sensors 118, and may include computing facilities 122 for
controlling, processing, storing, and/or visualizing the
measurements gathered by the electromagnetic sensors 118. The
computing facilities 122 may be communicably coupled to the pipe
inspection tool 114 by way of the cable 116.
[0029] The electromagnetic sensors 118 may include one or more
electromagnetic coil antennas that may be used as transmitters,
receivers, or a combination of both (i.e., transceivers) for
obtaining in situ measurements of the pipe(s) 108 and thereby
determining the structural integrity or condition of each pipe 108.
Multiple measurements may be made by the electromagnetic sensors
118 as the pipe inspection tool 114 is lowered into the wellbore
104 (i.e., "down log") and/or raised back to the surface of the
well (i.e., "up log"). Each measurement gives an indication of the
condition of the pipes 108 at the specific depth where the pipe
inspection tool 114 is located.
[0030] The principle of measurement is based on two separate
mechanisms: magnetic fields that follow the magnetically shortest
path (such as in magnetic circuits) and eddy currents that are
induced on the pipes 108, which create signals as a function of the
electromagnetic skin depth of the pipes 108. Received signals are
also affected by casing collars and natural changes in the magnetic
properties of different pieces of a wellbore pipe. After received
signals are recorded, they are interpreted by an algorithm, and
features of the pipes 108 can be calculated from the measurements.
These calculations and determinations can be undertaken, for
example, using the computing facilities 122 at the logging facility
120. Advantageously, electromagnetic inspection tools, such as the
pipe inspection tool 114, provide a capability to make measurements
of the pipes 108 beyond the first or innermost wellbore pipe.
[0031] In some embodiments, the electromagnetic sensors 118 may be
designed to operate in a centralized position within the innermost
pipe 108, such as through the use of one or more centralizers (not
shown) attached to the body of the pipe inspection tool 114. In
other embodiments, however, the electromagnetic sensors 118 may be
designed to be adjacent or in intimate contact with the inner wall
of the innermost pipe 108. In such embodiments, the electromagnetic
sensors 118 may be mounted on one or more deployable sensor pads
(not shown) positioned on actuatable arms (not shown) that move the
electromagnetic sensors 118 radially outward toward the inner wall
of the innermost pipe 108.
[0032] FIG. 2 is a partial cross-sectional side view of an
exemplary pipe inspection tool 200 suspended within the wellbore
104, according to one or more embodiments of the present
disclosure. For simplicity, only one side or half of the wellbore
104 is shown in FIG. 2. The pipe inspection tool 200 may be the
same as or similar to the pipe inspection tool 114 of FIG. 1 and,
therefore, may be used to monitor the pipes 108 positioned within
the wellbore 104. In the illustrated embodiment, the pipes 108 are
shown as a first pipe 108a and a second pipe 108b, where the first
pipe 108a is the innermost wellbore pipe and/or
concentrically-located within the second pipe 108b. In some
embodiments, the first and second pipes 108a,b may line the walls
of the wellbore 104 as concentric strings of casing. In other
embodiments, however, the first pipe 108a may comprise a production
pipe concentrically- or eccentrically-positioned within the second
pipe 108b, which may comprise casing that lines the wellbore 104,
without departing from the scope of the disclosure. As will be
appreciated, more than two pipes 108a,b may be used in any of the
embodiments described herein.
[0033] As illustrated, the pipe inspection tool 200 includes a body
202 and at least one electromagnetic sensor 204 positioned within
or otherwise attached to the body 202. The electromagnetic sensor
204 may be similar to or the same as the electromagnetic sensor 118
of FIG. 1. As illustrated, the electromagnetic sensor 204 may
include a coil antenna 206 that has at least one coil winding 208
extending axially along at least a portion of the length of the
electromagnetic sensor 204. While not expressly shown in FIG. 2,
the coil antenna 206 may further include a core, and the coil
winding 208 may be wrapped about the core. As described in more
detail below, the core may be made of a magnetically-permeable
material and may help amplify or boost electromagnetic signals
emitted by the electromagnetic sensor 204. In some embodiments, the
core may comprise a solid, elongate rod. In other embodiments,
however, the core may be segmented or laminated into several axial
lengths.
[0034] In the illustrated embodiment, the coil winding 208 is
depicted as multiple closed (i.e., disconnected) loops for
illustration purposes only and, therefore, should not be considered
as limiting the present disclosure. Rather, the coil winding 208
will typically exhibit a continuous solenoid or helical winding
pattern that extends between the axial upper and lower ends of the
coil antenna 206. Moreover, while depicted in FIG. 2 as exhibiting
a generally square or rectangular shape or profile, the coil
winding 208 of the coil antenna 206 may alternatively exhibit a
circular or elliptical shape, without departing from the scope of
the disclosure.
[0035] In the illustrated embodiment, the coil winding 208 is
coupled to a power source 210 (e.g., an alternating current) at a
first terminal 212a and a second terminal 212b. The power source
210 may be characterized as a transmitter-side amplifier, and the
first and second terminals 212a,b may alternatively be referred to
as first and second "ports," respectively, that are electrically
connected to the input/output of the transmitter-side amplifier.
When excited by the power source 210, such as through the influx of
an alternating current or a voltage, the coil antenna 206 generates
a magnetic field 214 that extends radially away from the pipe
inspection tool 200 and penetrates at least one of the pipes
108a,b.
[0036] The electromagnetic sensor 204 may further include one or
more receivers 216 electrically connected to the coil antenna 206
at various axial locations along the coil winding 208. The
receivers 216 are depicted in FIG. 2 as a first receiver 216a, a
second receiver 216b, and a third receiver 216c. The first receiver
216a may be electrically coupled to the coil winding 208 at third
and fourth terminals 212c and 212d, the second receiver 216b may be
electrically coupled to the coil winding 208 at fifth and sixth
terminals 212e and 212f, and the third receiver 216c may be
electrically coupled to the coil winding 208 at seventh and eighth
terminals 212g and 212h. As illustrated, the seventh and eighth
terminals 212g,h axially interpose the fifth and sixth terminals
212e,f, the fifth and sixth terminals 212e,f axially interpose the
third and fourth terminals 212c,d, and the third and fourth
terminals 212c,d axially interpose the first and second terminals
212a,b. As a result, the first receiver 216a may exhibit a first
magnetic sensitivity 218a, the second receiver 216b may exhibit a
second magnetic sensitivity 218b, and the third receiver 216c may
exhibit a third magnetic sensitivity 218c, where the first magnetic
sensitivity 218a extends radially deeper than the second magnetic
sensitivity 218b, and the second magnetic sensitivity 218c extends
radially deeper than the third magnetic sensitivity 218c.
[0037] Since the radial depth of investigation is proportional to
the size (i.e., effective axial length) of the receiver 216a-c,
each measurement obtained by the receivers 216a-c will be
influenced differently by different pipes 108a,b. Such diverse
information allows for accurate interpretation of multiple features
of the pipes 108a,b, such as any defects or corrosion that may be
present on the pipes 108a,b. While three receivers 216a-c are
depicted in FIG. 2, it will be appreciated that more or less than
three receivers 216a-c may be employed in the electromagnetic
sensor 204, without departing from the scope of the disclosure.
[0038] FIG. 3 is a schematic flowchart of an exemplary method 300
of operating the electromagnetic sensor 200 of FIG. 2, according to
one or more embodiments. According to the method 300, an excitation
signal may be transmitted between first and second terminals of a
coil antenna, as at 302. The excitation signal may be a time-domain
or frequency-domain (steady-state) signal generated by the power
source 210 and conveyed through the coil antenna 206 between the
first and second terminals 212a,b. The excitation signal may result
in the generation of the magnetic field 214.
[0039] A first response signal may then be measured between third
and fourth terminals of the coil antenna, where at least one of the
third and fourth terminals is different from the first and second
terminals, as at 304. The first response signal may be received and
measured by any of the receivers 216a-c described above. In at
least one embodiment, one of the receivers 216a-c may share a
terminal with the power source 210. The first response signal may
then be processed to determine a characteristic of a first pipe
positioned in a wellbore, as at 306. Example characteristics of the
first pipe that may be determined include, but are not limited to,
the dimensions (i.e., diameter, wall thickness, etc.) of the first
pipe, the presence of a defect (e.g., corrosion, fractures, holes,
and decreased wall thickness) in the first pipe, and/or the
presence of a conductive or magnetically-permeable feature in the
first pipe.
[0040] In some embodiments, the first response signal may be
conveyed to the logging facility 120 (FIG. 1) and the associated
computing facilities 122 (FIG. 1) for processing via the cable 116
(FIG. 1). The first pipe of 306 may refer to either the first or
second pipes 108a,b of FIG. 2, and may depend on the axial distance
between the third and fourth terminals of 304. The first pipe 108a,
for instance, may be monitored with a shorter axial distance
between the third and fourth terminals, and the second pipe 108b
may be monitored with a longer axial distance between the third and
fourth terminals.
[0041] FIG. 4 is a schematic flowchart of another exemplary method
400 of operating the electromagnetic sensor 200 of FIG. 2,
according to one or more embodiments. According to the method 400,
an excitation signal may be transmitted between first and second
terminals of a coil antenna, as at 402. Again, the excitation
signal may be a time-domain or frequency-domain (steady-state)
signal generated by the power source 210 and conveyed through the
coil antenna 206 between the first and second terminals 212a,b, and
the excitation signal may result in the generation of the magnetic
field 214.
[0042] A first response signal may then be measured between third
and fourth terminals of the coil antenna, as at 404, and a second
response signal may be measured between fifth and sixth terminals
of the coil antenna, as at 406, where an axial length of the coil
antenna between the fifth and sixth terminals is longer than an
axial length of the coil antenna between the third and fourth
terminals. In some embodiments, for example, the first response
signal may be received by the second or third receivers 216b,c
(FIG. 2) via the fifth and sixth terminals 212e,f (FIG. 2) or the
seventh and eighth terminals 212g,h (FIG. 2), respectively, and the
second response signal may be received by the first or second
receivers 216a,b (FIG. 2) via the third and fourth terminals 212c,d
(FIG. 2) or the fifth and sixth terminals 212e,f (FIG. 2),
respectively. In at least one embodiment, the first response signal
is received by the third receiver 216c via the seventh and eighth
terminals 212g,h, and the second response signal is received by the
first receiver 216a the third and fourth terminals 212c,d.
[0043] The first and second response signals may then be processed
to determine characteristics of first and second pipes positioned
in a wellbore, as at 408. The first and second pipes of 408 may
refer to the first and second pipes 108a,b of FIG. 2. Example
characteristics of the first and second pipes 108a,b that may be
determined include, but are not limited to, the dimensions (i.e.,
diameter, wall thickness, etc.) of the pipes 108a,b, the presence
of a defect (e.g., corrosion, fractures, holes, and decreased wall
thickness) in the pipes 108a,b, and/or the presence of a conductive
or magnetically-permeable feature in the pipes 108a,b. In some
embodiments, the first and second response signals may be conveyed
to the logging facility 120 (FIG. 1) and the associated computing
facilities 122 (FIG. 1) for processing via the cable 116 (FIG.
1).
[0044] FIG. 5 is a partial cross-sectional side view of another
exemplary pipe inspection tool 500 suspended within the wellbore
104, according to one or more embodiments of the present
disclosure. For simplicity, only one side or half of the wellbore
104 is shown in FIG. 5. The pipe inspection tool 500 may be similar
in some respects to the pipe inspection tool 200 of FIG. 2 and
therefore may be best understood with reference thereto, where like
numerals represent like elements or components not described again
in detail. Similar to the pipe inspection tool 200, the pipe
inspection tool 500 may be used to monitor the pipes 108a,b
positioned within the wellbore 104. Moreover, similar to the pipe
inspection tool 200, the pipe inspection tool 500 includes the
electromagnetic sensor 204 positioned within the body 202.
[0045] In the illustrated embodiment, the coil winding 208 of the
coil antenna 206 is electrically coupled to multiple power sources
210 at multiple terminals 212. More particularly, a first power
source 210a is coupled to the coil winding 208 at the first and
second terminals 212a,b, a second power source 210b is coupled to
the coil winding 208 at the third and fourth terminals 212c,d, a
third power source 210c is coupled to the coil winding 208 at the
fifth and sixth terminals 212e,f, and a fourth power source 210d is
coupled to the coil winding 208 at the seventh and eighth terminals
212g,h. When excited by the power sources 210a-d, the coil antenna
206 generates magnetic fields 214a, 214b, 214c, and 214d,
respectively, that extend radially away from the pipe inspection
tool 500 and penetrate at least one of the pipes 108a,b.
[0046] The electromagnetic sensor 204 of FIG. 5 may further include
a plurality of receivers 504 electrically connected to the coil
antenna 206 at various axial locations along the coil winding 208.
The receivers, shown as first, second, third, and fourth receivers
504a, 504b, 504c, and 504d, respectively, may be similar to the
receivers 210a-c of FIG. 2. As illustrated, the first receiver 504a
may be electrically coupled to the coil winding 208 at the first
and second terminals 212a,b, the second receiver 504b may be
electrically coupled to the coil winding 208 at the third and
fourth terminals 212c,d, the third receiver 504c may be
electrically coupled to the coil winding 208 at the fifth and sixth
terminals 212e,f, and the fourth receiver 504d may be electrically
coupled to the coil winding 208 at the seventh and eighth terminals
212g,h. Accordingly, the first receiver 504a may exhibit a first
magnetic sensitivity 506a, the second receiver 504b may exhibit a
second magnetic sensitivity 506b, the third receiver 504c may
exhibit a third magnetic sensitivity 506c, and the fourth receiver
504d may exhibit a fourth magnetic sensitivity 506d. The first
magnetic sensitivity 506a extends radially deeper than the second
magnetic sensitivity 506b, the second magnetic sensitivity 506b
extends radially deeper than the third magnetic sensitivity 506c,
and the third magnetic sensitivity 506c extends radially deeper
than the fourth magnetic sensitivity 506d.
[0047] Accordingly, the excitation signals of the power sources
210a-d may be applied at different terminals 212a-h of the coil
winding 208, which are also used for detecting response signals
obtained by the receivers 504a-d. In some embodiments, the
excitation signals may be applied simultaneously and at the same
frequency. In other embodiments, however, the excitation signals
may be applied at different frequencies. Moreover, the excitation
signals may be applied at different times, without departing from
the scope of the disclosure.
[0048] Multiple measurements with different excitations may be made
by implementing a frequency or time-multiplexing method. In
general, a combination of all N excitation signals and N receivers
produces a total of N.sup.2 measurements, all of which can be used
in determining characteristics of the pipes 108a,b. Similar to the
pipe inspection tool 200 of FIG. 2, the pipe inspection tool 500
may be able to generate multiple depths of investigation and
thereby allow multi-pipe 108a,b interpretation. However, due to
availability of excitations with smaller spacing, which exhibits
smaller sensitivity volumes, the embodiment of FIG. 5 may be
capable of producing much smaller depths of investigation. As will
be appreciated, this may allow a broader range of interpretation
and may, therefore, result in more accuracy in interpretation of
radially shallow features, such as those associated with the first
pipe 108a.
[0049] FIG. 6 is a schematic flowchart of an exemplary method 600
of operating the electromagnetic sensor 500 of FIG. 5, according to
one or more embodiments. According to the method 600, a first
excitation signal may be transmitted between first and second
terminals of a coil antenna, as at 602. The first excitation signal
may be a time-domain or frequency-domain (steady-state) signal
generated by any of the power sources 210a-d and conveyed through
the coil antenna 206 between a corresponding pair of the
electrically-coupled terminals 212a-h. The first excitation signal
may result in the generation of a corresponding magnetic field
214a-d. A first response signal may then be measured between the
first and second terminals, as at 604.
[0050] The method 600 may then proceed by transmitting a second
excitation signal between third and fourth terminals of the coil
antenna, as at 606, where the third and fourth terminals are
different from the first and second terminals. Similar to the first
excitation signal, the second excitation signal may be a
time-domain or frequency-domain (steady-state) signal generated by
any of the power sources 210a-d, excepting the power source 210a-d
used to generate the first excitation signal, and conveyed through
the coil antenna 206 between a corresponding pair of the
electrically-coupled terminals 212a-h, but different from the pair
of the terminals 212a-h used for the first excitation signal.
Moreover, the second excitation signal may result in the generation
of a corresponding magnetic field 214a-d (excepting the magnetic
field 214a-d generated by the first excitation signal). A second
response signal may then be measured between the third and fourth
terminals, as at 608.
[0051] In at least one embodiment, the first excitation signal is
generated by the first power source 210a and transmitted between
the first and second terminals 212a,b of the coil antenna 206, and
the first response signal is then measured by the first receiver
504a at the first and second terminals 212a,b. In such embodiments,
the second excitation signal may be generated by any of the second,
third, or fourth power sources 210b-d and transmitted between the
any corresponding pair of terminals 212c-h of the coil antenna 206,
and the second response signal is then measured by the
corresponding second, third, or fourth receiver 504c-d. It will be
appreciated, however, that several different scenarios or
configurations of operating the electromagnetic sensor 500 in
accordance with steps 602-608 may be had, without departing from
the scope of the disclosure.
[0052] The first and second response signals may then be processed
to determine characteristics of first and second pipes positioned
in a wellbore, as at 610. The first and second pipes of 610 may
refer to the first and second pipes 108a,b of FIG. 5, and the
characteristics of the first and second pipes 108a,b that may be
determined are as mentioned above. Moreover, in some embodiments,
the first and second response signals may be conveyed to the
logging facility 120 (FIG. 1) and the associated computing
facilities 122 (FIG. 1) for processing via the cable 116 (FIG.
1).
[0053] FIG. 7 is a schematic flowchart of another exemplary method
700 of operating the electromagnetic sensor 500 of FIG. 5,
according to one or more embodiments. According to the method 700,
a first excitation signal is transmitted between first and second
terminals of a coil antenna, as at 702. The first excitation signal
may be a time-domain or frequency-domain (steady-state) signal
generated by any of the power sources 210a-d and conveyed through
the coil antenna 206 between a corresponding pair of the
electrically-coupled terminals 212a-h. The first excitation signal
may result in the generation of a corresponding magnetic field
214a-d.
[0054] A first response signal is then measured between third and
fourth terminals of the coil antenna, where an axial length of the
coil antenna between the third and fourth terminals is longer than
an axial length of the coil antenna between the first and second
terminals, as at 704. Based on electromagnetic reciprocity, this
embodiment may produce substantially the same result as the
embodiment of the method 600 where first and third terminals are
switched, and the second and fourth terminals are switched (or
otherwise the role of excitation and reception is switched).
However, the impedance loading of embodiments will be different
from each other since portions of the coil antenna that are driven
with excitation may be different. As a result, this method 700 may
be preferred as compared to the method 600 based on electrical
design considerations.
[0055] The first response signal may then be processed to determine
a characteristic of a second pipe positioned in a wellbore, as at
706, where the second pipe is concentrically-positioned about a
first pipe positioned within the wellbore. The second pipe of 306
may refer to second pipe 108b of FIG. 5, and example
characteristics of the second pipe that may be determined include,
but are not limited to, the dimensions (i.e., diameter, wall
thickness, etc.) of the second pipe, the presence of a defect
(e.g., corrosion, fractures, holes, and decreased wall thickness)
in the second pipe, and/or the presence of a conductive or
magnetically-permeable feature in the second pipe. In some
embodiments, the first response signal may be conveyed to the
logging facility 120 (FIG. 1) and the associated computing
facilities 122 (FIG. 1) for processing via the cable 116 (FIG.
1).
[0056] Referring now to FIG. 8, illustrated is a partial
cross-sectional side view of another exemplary pipe inspection tool
800 suspended within the wellbore 104, according to one or more
embodiments of the present disclosure. For simplicity, only one
side or half of the wellbore 104 is shown in FIG. 8. The pipe
inspection tool 800 may be similar in some respects to the pipe
inspection tools 200 and 500 of FIGS. 2 and 5, respectively, and
therefore may be best understood with reference thereto, where like
numerals represent like elements or components not described again
in detail. Similar to the pipe inspection tools 200 and 500, for
instance, the pipe inspection tool 800 may be used to monitor the
pipes 108a,b positioned within the wellbore 104. Moreover, the pipe
inspection tool 800 includes the electromagnetic sensor 204
positioned within the body 202.
[0057] As illustrated, the coil winding 208 of the coil antenna 206
is electrically coupled to the power source 210 at the first and
second terminals 212a,b located at opposing axial ends of the coil
winding 208. When excited by the power source 210, the coil antenna
206 generates the magnetic field 214 that extends radially away
from the pipe inspection tool 200 and penetrates at least one of
the pipes 108a,b.
[0058] The electromagnetic sensor 204 may further include a
plurality of receivers 216 electrically connected to the coil
antenna 206 at various axial locations along the coil winding 208.
More particularly, the electromagnetic sensor 204 may include
receivers 216a, 216b, 216c, 216d, 216e, 216f, and 216g, each being
electrically coupled to each other and also to the coil winding 208
at a plurality of terminals 802, shown as terminals 802a, 802b,
802c, 802d, 802e, and 802f. Since the radial depth of investigation
is proportional to the size (i.e., length) of the receiver 216a-g,
the short axial distances along the coil antenna 206 between
adjacent terminals 212a, 802a-f, and 212b results in the receivers
216a-g exhibiting corresponding shallow magnetic sensitivities 804,
shown as magnetic sensitivities 804a, 804b, 804c, 804d, 804e, 804f,
and 804g.
[0059] Although each of the measurements derived from the receivers
216a-g may have shallow (low) depth of investigation, it is
possible to consider summation of different measurements to
synthesize measurement between any combinations of the terminals
212a, 802a-f, and 212b. As an example, summation of all the
measurements depicted in FIG. 8 may provide the result of an
equivalent measurement at the first and second terminals 212a,b. As
another example, summation of the three measurements provided at
the center of the coil antenna 206 may produce the results of a
single measurement between the uppermost terminals 212a and 802a-c
and the lowermost terminals 802d-f and 212b that belong to the
three measurements obtained by the receivers 216c-e located at the
center. As will be appreciated, this may allow synthesis of any
depth of investigation as required or desired.
[0060] FIG. 9 is a schematic flowchart of an exemplary method 900
of operating the electromagnetic sensor 800 of FIG. 8, according to
one or more embodiments. According to the method 900, an excitation
signal may be transmitted between first and second terminals of a
coil antenna, as at 902. The excitation signal may be a time-domain
or frequency-domain (steady-state) signal generated by the power
source 210 (FIG. 8) and conveyed through the coil antenna 206
between the first and second terminals 212a,b, and the excitation
signal may result in the generation of the magnetic field 214 (FIG.
8).
[0061] A first response signal may then be measured between the
first and second terminals, as at 904, and a second response signal
may be measured between the second and a third terminal of the coil
antenna, as at 906. In the embodiment of FIG. 8, for example, the
first response signal may be measured between the first and second
terminals 212a,b and the second response signal may be measured
between the second terminal 212b and any of the remaining terminals
802a-f.
[0062] The method 900 may then proceed by summing the first and
second response signals to obtain a summed response signal that is
indicative of a measurement between first and third terminals, as
at 908. The summed response signal may then be processed to
determine a characteristic of first and/or second pipes positioned
in a wellbore, as at 910. As with prior embodiments, the first and
second pipes of 910 may refer to the first and second pipes 108a,b
of FIG. 8, and the characteristics of the first and second pipes
108a,b that may be determined are as mentioned above. Moreover, in
some embodiments, the first and second response signals may be
conveyed to the logging facility 120 (FIG. 1) and the associated
computing facilities 122 (FIG. 1) for processing via the cable 116
(FIG. 1).
[0063] FIG. 10 is a partial cross-sectional side view of another
exemplary pipe inspection tool 1000 suspended within the wellbore
104, according to one or more embodiments of the present
disclosure. For simplicity, only one side or half of the wellbore
104 is shown in FIG. 10. The pipe inspection tool 1000 may be
similar in some respects to the pipe inspection tools 200, 500, and
800 of FIGS. 2, 5, and 8, respectively, and therefore may be best
understood with reference thereto, where like numerals represent
like elements or components not described again in detail. Similar
to the pipe inspection tools 200, 500, 800, for instance, the pipe
inspection tool 1000 may be used to monitor the pipes 108a,b
positioned within the wellbore 104. Moreover, the pipe inspection
tool 1000 includes the electromagnetic sensor 204 positioned within
the body 202.
[0064] As illustrated, the coil winding 208 of the coil antenna 206
is electrically coupled to multiple power sources 210a-g at
multiple terminals 1002a-h, where the power sources 210a-g are
coupled in series to each of the terminals 1002a-h. Upon excitation
by the various power sources 210a-g, the coil antenna 206 may
generate corresponding magnetic fields 1004a-g.
[0065] The electromagnetic sensor 204 may further include a
plurality of receivers 216 electrically connected to the coil
antenna 206 at various axial locations along the coil winding 208.
More particularly, the electromagnetic sensor 204 may include
receivers 216a-g each being electrically coupled in series to each
other and also to the coil winding 208 at the plurality of
terminals 1002a-h. Since the radial depth of investigation is
proportional to the size (i.e., length) of the receiver 216a-g, the
short axial distances along the coil antenna 206 between adjacent
terminals 1002a-h results in the receivers 216a-g exhibiting
corresponding shallow magnetic sensitivities 1006a-g.
[0066] Accordingly, the pipe inspection tool 1000 may be configured
to conduct excitations and measurements at each of the terminals
1002a-h. In this configuration, any combination of measurements is
possible between any of the power sources 210a-g and receivers
216a-g. It is also possible synthesize a measurement from any
combination of exciter terminals 1002a-h to any combination of
receiver terminals 1002a-h by summing different power source 210a-g
and different receiver 216a-g measurements accordingly.
[0067] As an example, summation of all combination of N power
source 210 measurements and N receiver 216 measurements (a total of
N.sup.2) would produce a measurement that is equivalent to a
measurement where excitation is applied between the axial end
points of the coil antenna 206, and receiving terminals 1002a-h are
also placed at the axial end points of the coil antenna 206. It is
noted that when multiple depth measurements are considered, not all
measurements will be unique, since some measurements are simply a
depth-shifted version of other measurements.
[0068] Referring now to FIG. 11, illustrated is a schematic
flowchart of an exemplary method 1100 of operating the
electromagnetic sensor 1000 of FIG. 10, according to one or more
embodiments. According to the method 1000, a number (i.e., N+1) of
consecutive terminals are selected on a coil antenna, as at 1102.
An excitation signal is then transmitted between each neighboring
terminal, and thereby producing a total of N excitation signals, as
at 1104. For each excitation signal, a corresponding response
signal is received and recorded between each neighboring terminal,
and thereby producing a total of N.sup.2 measurements, as at 1106.
Next, a summation operation is performed between a subset of the
measurements that corresponds to an excitation signal between any
two of the N+1 terminals, and response signal reception between any
two of the N+1 terminals to obtain a synthesized signal, as at
1108. Finally, the synthesized signal is used in the calculation of
a characteristic of a plurality of wellbore pipes, as at 1110. In a
more general case, the synthesized signal can be generated by using
weighted averages of multiple receiver signals measured at multiple
pairs of receivers, with weight 1 equivalent to a sum, weight -1
equivalent to a subtraction, and any other weight possible
depending on the convenience in processing the data.
[0069] In any one of the exemplary pipe inspection tools 200, 500,
800, 1000 of FIGS. 2, 5, 8, and 10, respectively, described herein,
it may be possible to combine the measured responses (i.e.,
voltages) to obtain voltage differences. The voltage differences
are useful because they may provide more information about the
local defects in the wellbore pipes 108a,b. This is particularly
the case in scenarios where the combined receiver voltages
correspond to receivers that are symmetrically disposed with
respect to the active transmitter.
[0070] To describe this concept more clearly, reference is again
made to the pipe inspection tool of FIG. 10, where the transmitters
(i.e., power sources 210a-g) and the receivers 216a-g each have the
same axial length along the coil antenna 206. The multiple
transmitters can be operated sequentially. By considering in each
case the measurements of the receiver 216a-g closest to the active
transmitter, those measurements, in case there is symmetry along
the axial direction of the wellbore 104, would be identical.
However, when the pipes 108a,b contain defects that break the
symmetry along the axial direction of the wellbore 104, the
cancellation will not be exact, with the difference being caused by
the presence of the defect. The subtraction of these response
signals will result in relatively small voltages. To reduce the
error in the measurement of the differences it is convenient to
subtract them in hardware and measure the difference directly.
[0071] This process is schematically illustrated in FIG. 12, which
shows that the difference is measured directly instead of being
evaluated from the measurements of V.sub.1 and V.sub.2. Different
combinations of voltage differences can be generated and all should
be considered as expressly included in this disclosure. The use of
difference measurements can improve the inversion of pipe
thickness, as described in more detail below, and the voltage
differences should be considered as included in the voltage
measurement there described. As stated above, the signals can be
combined by using weighted averages, with weight numbers being
positive or negative, and then adding the weighted signals to
generate a combined signal that can be used to extract information
about the pipes 108a,b.
[0072] Referring now to FIG. 13, with continued reference to FIG.
10, illustrated is a schematic diagram of another embodiment of the
electromagnetic sensor 1000 of FIG. 10. When an excitation signal
is applied between different terminals 1002a-h of the coil antenna
206, an unwanted coupling may be formed due to the presence of a
ferrite core 1302, about which the coil winding 208 may be wound
and which is typically used to amplify (boost) the magnetic fields
generated by the coil antenna 206. This is due to magnetic fields
that complete the magnetic circuit using the shortest path that is
available, which is through the material of the core 1302, which is
typically a magnetically-permeable material.
[0073] In order to avoid this, and in accordance with the present
embodiment, the core 1302 may be segregated or otherwise subdivided
into multiple pieces or core segments 1304, shown as core segments
1304a, 1304b, 1304c, 1304d, 1304e, 1304f, and 1304g. Segregating
the core 1302 into the multiple core segments 1304a-g may allow
magnetic fields to escape the material of the core 1302 at the
axial ends of each core segment 1304a-g if they have an incentive
to do so, such as in the event the return path is short
geometrically. Each subdivided core segment 1304a-g may exhibit an
axial length 1306 and may be axially separated or offset from an
adjacent core segment 1304a-g by a gap 1308. The magnetic fields
generated by the coil antenna 206 may be able to escape the coil
antenna 206 at the gap 1308 defined between axially adjacent core
segments 1304a-g.
[0074] In some embodiments, axially adjacent core segments 1304a-g
may be separated by a gap 1308 that is one-fifth the axial length
1306 of each core segment 1304a-g. In other embodiments, axially
adjacent core segments 1304a-g may be separated by a gap 1308 that
is one-third the axial length 1306 of each core segment 1304a-g. In
yet other embodiments, axially adjacent core segments 1304a-g may
be separated by a gap 1308 that is equal to the axial length 1306
of each core segment 1304a-g, without departing from the scope of
the disclosure. The distance between the terminals 1002a-h is an
integer multiple of the total size of the core segments 1304a-g, so
that each consecutive terminal 1002a-h is magnetically decoupled
for obtaining as diverse information as possible.
[0075] It is also possible to decouple the magnetic fields by using
an excitation in the opposite direction from a different
combination of terminals 1002a-g. In general, for the general case
of N+1 terminals, N excitation sources and N receivers, as shown in
FIG. 13, one can write the total vector of measured voltages in a
case with the core 1302 and no pipes 108a,b (FIG. 10) present as
follows:
[ Z 11 Z 1 N Z N 1 Z NN ] [ I 1 I N ] = [ V 1 V N ] Equation ( 1 )
##EQU00001##
[0076] where Z.sub.ij is the voltage at the i'th receiver, when
only the j'th exciter is activated with unit current (also called
mutual impedance), I.sub.i is the adjusted current of i'th exciter,
and V.sub.i is the voltage of the i'th receiver, all for the case
with the core 1302 and without any pipes. As it can be seen by
Equation (1), it may be possible to adjust the currents I.sub.i to
obtain a desired total voltage V.sub.i. A similar equation can be
written for a case where no core 1302 and no pipe is present:
[ Z 11 ' Z 1 N ' Z N 1 ' Z NN ' ] [ I 1 ' I N ' ] = [ V 1 ' V N ' ]
Equation ( 2 ) ##EQU00002##
[0077] where V'.sub.ij is the voltage at the i'th receiver, when
only the j'th exciter is activated with unit current (also called
mutual impedance), I'.sub.i is the adjusted current of i'th
exciter, and V'.sub.i is the voltage of the i'th receiver, all for
the case without the core and without any pipes. In order to use a
pipe inspection tool with the core 1302 (i.e., to have improvements
in signal strength) but obtain results that are as decoupled as a
pipe inspection tool without the core 1302, the following currents
equation may be used instead:
[ I 1 I N ] = [ Z 11 Z 1 N Z N 1 Z NN ] - 1 [ Z 11 ' Z 1 N ' Z N 1
' Z NN ' ] [ I 1 ' I N ' ] Equation ( 3 ) ##EQU00003##
[0078] Alternatively, a correction on the voltages could be used,
as follows:
[ V 1 V N ] = [ Z 11 Z 1 N Z N 1 Z NN ] - 1 [ Z 11 ' Z 1 N ' Z N 1
' Z NN ' ] [ V 1 ' V N ' ] Equation ( 4 ) ##EQU00004##
[0079] Computation of impedances, Z.sub.ij, for the decoupling
operation above can be performed through modeling or experiments by
individually exciting each coil and measuring the signal at all
other coils. For example, In order to calculate the first row of
the impedance matrix in Equation (1), current in exciter 1 can be
set to 1 Ampere, and all other currents can be set to 0. Resulting
voltages at the receivers can be normalized to 1 Ampere to produce
the impedances in the first column of the impedance matrix.
[0080] Referring now to FIG. 14, illustrated is a block diagram of
an exemplary data acquisition and control system 1400 that may be
used for monitoring pipes in a wellbore, according to one or more
embodiments of the present disclosure. Those skilled in the art
will readily appreciate that the data acquisition and control
system 1400 as described herein is merely one example of a wide
variety of data acquisition systems that can operate in accordance
with the principles of this disclosure. Accordingly, the data
acquisition and control system 1400 is not to be limited solely to
the specific details described herein and other changes or
alterations to the structure and processing capabilities may be
introduced without departing from the scope of the disclosure.
[0081] As illustrated, the data acquisition and control system 1400
may include at least one coil antenna 1402, which may be the same
as or similar to the coil antenna 206 shown in any of the
embodiments described herein. The coil antenna 1402 may be driven
by transmitter electronics 1404, which may include one or more
transmitters, a demultiplexer, a digital-to-analog converter, and
other modules or devices used to support operation of the
transmitters. Each transmitter may be configured to transmit at
least one signal at a particular frequency and, depending on the
monitoring application, multiple signals may be transmitted at
different frequencies. In some embodiments, a signal generator 1406
may be configured to generate the signals for transmission by the
transmitters, the digital-to-analog converter may be configured to
convert digital signals to analog signals, and the demultiplexer
may be configured to selectively couple the signal generator 1406
to the transmitters. As will be appreciated, any combination of one
or more signal generators 1406, digital-to-analog converters, and
demultiplexers may be used to drive the transmitters.
Alternatively, the transmitters may each perform the function of
the signal generator 1406, and the separate signal generator 1406
as part of the transmitter electronics 1404 may be omitted from the
data acquisition and control system 1400.
[0082] Signals from the coil antenna 1402 may be received with
receiver electronics 1408, which may include one or more receivers,
an analog-to-digital converter, and other modules or devices used
to support operation of the receivers. A system control center 1410
may communicably couple the receiver electronics 1408 to the
transmitter electronics 1404 and thereby control overall operation
of the data acquisition and control system 1400. As illustrated,
the system control center 1410 may further be communicably coupled
to at least a data acquisition unit 1412 and a data processing and
communication unit 1414, thereby placing the receiver electronics
1408 also in communication with such components. In some
embodiments, the data acquisition unit 1412 may be configured to
determine an amplitude and/or a phase of a received signal. The
acquired signal information may be stored, along with acquisition
time information in a data buffer of the data acquisition unit
1412. The data buffer may be useful when pipe characteristics are
determined based on signals received at different times and/or at
different positions within a wellbore.
[0083] Data processing may be performed at the earth's surface or
at a downhole location where the data acquisition and control
system 1400 is arranged. If the data processing is to be performed
at the surface, the acquired signal information from the receiver
electronics 1408, the data acquisition unit 1412, and the buffered
signal information from the data buffer may be conveyed to the data
processing and communication unit 1414 which may be configured to
transmit the data to the surface 1416 and to a computer or other
processing system (not shown) arranged at the surface 1416. If the
data processing is to be performed downhole, the data processing
and communication unit 1414, in conjunction with the other
components of the data acquisition and control system 1400, may be
configured to perform the necessary data processing.
[0084] Both the computer at the surface 1416 and the system control
center 1410 may include multiple processors and a memory configured
to receive and store data. The memory may be any non-transitory
machine-readable medium that has stored therein at least one
computer program with executable instructions that cause the
processor(s) to perform the data processing on the received
signals. The memory may be, for example, random access memory
(RAM), flash memory, read only memory (ROM), programmable read only
memory (PROM), electrically erasable programmable read only memory
(EEPROM), registers, hard disks, removable disks, a CD-ROM, a DVD,
any combination thereof, or any other suitable storage device or
medium.
[0085] Since the system control center 1410 is coupled to various
components of the data acquisition and control system 1400, the
system control center 1410 may be configured to adjust or otherwise
regulate various parameters of the data acquisition and control
system 1400 in order to optimize operation. For example, the system
control center 1410 may control the frequencies generated by the
signal generator 1406 in the transmitter electronics 1404 or the
transmitters. The system control center 1410 may also control the
timing of the transmitters. For instance, the system control center
1410 may cause the transmitters to operate sequentially or
according to a predetermined transmission sequence such that
time-lapse measurements or signals may be obtained by the
receivers. From the received signals, characteristics of the pipes
may be calculated and otherwise extracted.
[0086] More particularly, the excitation and measurement is
performed between a number of terminals (1 . . . N) of the coil
antenna 1402. It is possible to excite and measure between the same
combination of terminals of the coil antenna 1402, which
constitutes a self-impedance measurement. It is also possible to
excite and measure between a different combination of terminals of
the coil antenna 1402, which constitutes a mutual impedance
measurement. While such measurements are taking place, other ports
of the coil antenna 1402 may be shorted (in case of
voltage-controlled sources) or opened (in case of
current-controlled sources).
[0087] In general, excitation may be activated by the system
control center 1410 and a time-varying signal may be generated by
an amplifier included in the signal generator 1406, which is
typically converted to analog from digital by using the
digital-to-analog converter in the transmitter electronics 1404.
The time-varying signal may be sinusoidal with the phase and
amplitude of it controlled to a desired value. Typical operating
frequency of such a system is between 0.1-1000 Hz. High frequencies
suffer attenuation in pipes due to small skin depth, and low
frequencies suffer low signal level due to the inductive nature of
the measurement. The excitation may also be a pulse of different
shapes such as rectangular or triangular pulses.
[0088] The resulting magnetic fields that are generated are coupled
electromagnetically to the features of the pipes that are next to
the antenna coils 1402. At low frequencies, coupling is only
through magnetic permeability, but at higher frequencies,
conductivity may also be important due to decreasing skin depth.
Detected defects in the pipes generate differences in magnetic
fields either through magnetic permeability coupling or through
conductivity coupling. These changes contain information about the
features of the pipes and they are recorded by the receiving
antenna of the receiver electronics.
[0089] In the case of frequency-domain operation, the received
signals can be represented as voltage or current numbers in complex
domain with real and imaginary parts, in phasor domain as amplitude
and phase, or any other domain that can be obtained by analytical
mapping from any of these domains. In the time-domain operation,
received signals are magnitudes as a function of time, which can be
positive or negative. Results from time and frequency domain can be
transferred from one to another by using Fourier transform or
inverse Fourier transform. Results may be transferred from analog
to digital domain through the use of the analog-to-digital
converter included in the receiver electronics 1408. The results
may be normalized by the excitation magnitude (excitation current
in case of current controlled excitation, excitation voltage in
case of voltage controlled excitation), which can yield an
impedance measurement.
[0090] In addition to the eddy currents that exhibit pipe feature
information, a direct coupling from the transmitters to the
receivers exists. This direct coupling can be removed by software
through the use of an additive term, which is computed in an air
calibration step. Yet, another method is to use pulsed excitation
with temporally separated transmitting and receiving cycles. In the
listening period, the direct coupling dies out polynomially or
exponentially and only reflections, scattering or eddy currents
from the features are received. In the sinusoidal type excitation,
the length of the listening period determines the signal-to-noise
ratio (SNR) of the system. Longer listening times are required to
improve SNR, while this also causes slower logging speeds for a
fixed vertical resolution for the system.
[0091] The sampling frequency also can be optimized to reduce noise
while producing enough definition in time to resolve pipe features
at different distances to the tool. Listening time is also an
important parameter, since features of pipes that are far away
mostly arrive at late time. Since downhole memory is limited, it is
important to minimize listening time while still maintaining the
sensitivity to features that are further away from the tool such as
second or third pipe features. For a specific transmitter
excitation, multiple receivers can be recorded at the same time.
Similarly, multiple excitations and measurements can be performed
at the same time and they can be time, frequency or jointly
multiplexed for latter demultiplexing operation at the receiver.
Upon reception of the signals, they are digitized, stored in a
buffer, preprocessed and sent to the surface 1416 using the data
processing and communication unit 1414. The data is later inverted
and the results of the inversion or raw data can be visualized.
Decisions on what to do with the pipes being monitored can be made
based on the visualization logging or production.
[0092] Referring now to FIG. 15, illustrated is a schematic
flowchart of a method 1500 of converting measurement data 1502 into
one or more pipe characteristics 1504, according to one or more
embodiments of the present disclosure. More particularly, the
method 1500 may take measurement data 1502 in the form of impedance
signals V and convert them into one or more pipe characteristics
such as, but not limited to, thickness, magnetic permeability,
conductivity, and diameter measurements of any of the pipes.
[0093] In the illustrated method, a signal V is measured at time t
(time-domain operation) or frequency f (frequency domain operation)
at antenna depth z between the antenna terminals i.sub.r1 and
i.sub.r2 as a result of excitation between the ports i.sub.t1 and
i.sub.t2. The received signal V may then be preprocessed, as at
1506. Preprocessing the measurement data 1502 may include
performing temperature corrections through the use of correlation
tables or performing "software focusing" to remove drifts in the
electronics. Preprocessing the measurement data 1502 may also
include calibration, which may include normalization with the
excitation signal amplitude, eccentricity (stand-off) correction,
to remove the effect of a sensor pad (if used) not touching the
pipe, and temporal or spatial filters to reduce noise.
[0094] The preprocessed signal Vp may then be optionally
synthesized to obtain other measurements from existing
measurements, as at 1508. This may be accomplished by synthesizing
measurements from any combination of exciter terminals to any
combination of receiver terminals by summing different transmitter
and receiver measurements. In a most general case, as stated
before, the synthesized signal can be generated by using weighted
averages of multiple receiver signals measured at multiple pairs of
receivers, with weight 1 equivalent to a sum, weight -1 equivalent
to a subtraction, and any other weight possible depending on the
convenience in processing the data. A synthesized and/or
preprocessed signal Vp may then be fed to an inversion algorithm,
as at 1510, which looks up the measured signal in a database that
contains mappings between modeled signals and pipe features
(thickness, magnetic permeability, conductivity and diameter). The
pipe characteristics corresponding to the modeled signal that
matches with least mismatch with the measured processed signal is
selected. This formulation can be written as follows:
( t _ ( z ) , .mu. _ ( z ) , .sigma. _ ( z ) , d _ ( z ) ) = arg
min t _ , .mu. _ , .sigma. _ , d _ ( t / f , i t 1 , i t 2 , i r 1
, i r 2 ( V p ( z , t / f , i t 1 , i t 2 , i r 1 , i r 2 - V m ( t
_ , .mu. _ , .sigma. _ , d _ , t / f , i t 1 , i t 2 , i r 1 , i r
2 ) ) 2 ) Equatio n ( 5 ) ##EQU00005##
[0095] where t(z) is the inverted vector of pipe thicknesses,
.mu.(z) is the inverted vector of pipe magnetic permeabilities,
.sigma.(z) is the inverted vector of pipe conductivities, d(z) is
the inverted vector of pipe diameters, V.sub.m is the modeled (and
processed) measurement, t is the vector of pipe thicknesses of the
model, .mu. is the vector of pipe magnetic permeabilities of the
model, .sigma. is the vector of pipe conductivities of the model,
and d is the vector of pipe diameters of the model. The foregoing
vectors contain information related to a number of pipes, i.e.,
first element of the vector is the characteristic associated with
the first pipe, the second element of the vector is the
characteristic associated with the second pipe, etc.
[0096] Different cost functions that involve weighted differences
and different norms may be used. If a quick forward model is
available, search of the above minimum may be conducted by using an
iterative method, such as conjugate gradient, etc., in the place of
the database lookup. It is also possible use lab measurements in
the place of computer models. A range of pipes with different
features may be measured and measured signals may be used to
construct a library. In the case the decoupling method that
described by Equation (3) above is applied to the excitation
current, the same method should be applied to the model described
above.
[0097] Embodiments disclosed herein include:
[0098] A. A method that includes introducing a pipe inspection tool
into a first pipe positioned within a wellbore and further
positioned within at least a second pipe, the pipe inspection tool
including an electromagnetic sensor having a coil antenna that
includes a coil winding extending axially along at least a portion
of the electromagnetic sensor, transmitting an excitation signal
between a first terminal and a second terminal of the coil antenna,
measuring a first response signal between a third terminal and a
fourth terminal of the coil antenna, wherein at least one of the
third and fourth terminals is different from the first and second
terminals, and processing the first response signal to determine a
characteristic of the first pipe.
[0099] B. A method that includes introducing a pipe inspection tool
into a first pipe positioned within a wellbore and further
positioned within at least a second pipe, the pipe inspection tool
including an electromagnetic sensor having a coil antenna that
includes a coil winding extending axially along at least a portion
of the electromagnetic sensor, transmitting a first excitation
signal between a first terminal and a second terminal of the coil
antenna, measuring a first response signal between the first and
second terminals, transmitting a second excitation signal between a
third terminal and a fourth terminal of the coil antenna, where the
third and fourth terminals are different from the first and second
terminals, measuring a second response signal between the third and
fourth terminals, and processing the first and second signals to
determine a characteristic of one or both of the first and second
pipes.
[0100] C. A method that includes introducing a pipe inspection tool
into a first pipe positioned within a wellbore and further
positioned within at least a second pipe, the pipe inspection tool
including an electromagnetic sensor having a coil antenna that
includes a coil winding extending axially along at least a portion
of the electromagnetic sensor, transmitting a first excitation
signal between a first terminal and a second terminal of the coil
antenna, measuring a first response signal between the first and
second terminals, measuring a second response signal between the
second terminal and a third terminal of the coil antenna, summing
the first and second response signals to obtain a summed response
signal indicative of a measurement between the first and third
terminals, and processing the summed response signal to determine a
characteristic of at least one of the first and second pipes.
[0101] D. A method that includes introducing a pipe inspection tool
into a first pipe positioned within a wellbore and further
positioned within at least a second pipe, the pipe inspection tool
including an electromagnetic sensor having a coil antenna that
includes a coil winding extending axially along at least a portion
of the electromagnetic sensor, selecting a number of consecutive
terminals on the coil antenna, transmitting an excitation signal
between each neighboring terminal of the consecutive terminals of
the coil antenna, receiving and recording a corresponding response
signal for each excitation signal between each neighboring
terminal, adding a subset of the response signals for each
excitation signal between any two terminals of the number of
consecutive terminals to obtain a synthesized signal, and
processing the synthesized signal to determine a characteristic of
at least one of the first and second pipes.
[0102] Each of embodiments A, B, C, and D may have one or more of
the following additional elements in any combination: Element 1:
wherein transmitting the excitation signal comprises transmitting a
time-domain or frequency-domain (steady-state) signal generated by
a power source electrically-coupled to the first and second
terminals. Element 2: wherein measuring the first response signal
between the third terminal and the fourth terminal comprises
receiving the first response signal with a receiver
electrically-coupled to at least one of the third and fourth
terminals and included in the electromagnetic sensor. Element 3:
further comprising measuring a second response signal between a
fifth terminal and a sixth terminal of the coil antenna, where an
axial length of the coil antenna between the fifth and sixth
terminals is longer than an axial length of the coil antenna
between the third and fourth terminals, and processing the first
and second response signals to determine a characteristic of one or
both of the first and the second pipes. Element 4: wherein an axial
length of the coil antenna between the third and fourth terminals
is longer than an axial length of the coil antenna between the
first and second terminals, the method further comprising
processing the first response signal to determine a characteristic
of the second pipe. Element 5: wherein the coil winding is wound
about a segmented core comprising a plurality of core segments.
Element 6: wherein each core segment exhibits an axial length and
is axially separated from an adjacent core by a gap, and wherein
the gap is at least one-fifth or more of the axial length of each
adjacent core segment.
[0103] Element 7: wherein transmitting the first excitation signal
comprises transmitting a first time-domain or frequency-domain
(steady-state) signal generated by a first power source
electrically-coupled to the first and second terminals, and wherein
transmitting the second excitation signal comprises transmitting a
second time-domain or frequency-domain (steady-state) signal
generated by a second power source electrically-coupled to the
third and fourth terminals. Element 8: wherein measuring the first
response signal between the first terminal and the second terminal
comprises receiving the first response signal with a first receiver
electrically-coupled to the first and second terminals and included
in the electromagnetic sensor, and wherein measuring the second
response signal between the third terminal and the fourth terminal
comprises receiving the second response signal with a second
receiver electrically-coupled to the third and fourth terminals and
included in the electromagnetic sensor. Element 9: wherein the coil
winding is wound about a segmented core comprising a plurality of
core segments. Element 10: wherein each core segment exhibits an
axial length and is axially separated from an adjacent core by a
gap, and wherein the gap is at least one-fifth or more of the axial
length of each adjacent core segment.
[0104] Element 11: further comprising subtracting the first and
second response signals to obtain a difference response, and
processing the difference response to determine the characteristic
of at least one of the first and second pipes. Element 12: wherein
transmitting the excitation signal comprises transmitting a
time-domain or frequency-domain (steady-state) signal generated by
a power source electrically-coupled to the first and second
terminals. Element 13: wherein measuring the first response signal
between the first terminal and the second terminal comprises
receiving the first response signal with a first receiver
electrically-coupled to the first and second terminals and included
in the electromagnetic sensor, and wherein measuring the second
response signal between the second terminal and the third terminal
comprises receiving the second response signal with a second
receiver electrically-coupled to the second and third terminals and
included in the electromagnetic sensor. Element 14: wherein the
coil winding is wound about a segmented core comprising a plurality
of core segments. Element 15: wherein each core segment exhibits an
axial length and is axially separated from an adjacent core by a
gap, and wherein the gap is at least one-fifth or more of the axial
length of each adjacent core segment.
[0105] Element 16: further comprising combining the subset of the
response signals for each excitation signal between any two
terminals by one of addition, subtraction, or a weighted sum, where
weights of the weighted sum are positive or negative numbers, and
processing the synthesized signal to determine the characteristic
of at least one of the first and second pipes. Element 17: wherein
the coil winding is wound about a segmented core comprising a
plurality of core segments. Element 18: wherein each core segment
exhibits an axial length and is axially separated from an adjacent
core by a gap, and wherein the gap is at least one-fifth or more of
the axial length of each adjacent core segment.
[0106] By way of non-limiting example, exemplary combinations
applicable to A, B, C, and D include: Element 5 with Element 6;
Element 9 with Element 10; Element 14 with Element 15; and Element
17 with Element 18.
[0107] Therefore, the disclosed systems and methods are well
adapted to attain the ends and advantages mentioned as well as
those that are inherent therein. The particular embodiments
disclosed above are illustrative only, as the teachings of the
present disclosure may be modified and practiced in different but
equivalent manners apparent to those skilled in the art having the
benefit of the teachings herein. Furthermore, no limitations are
intended to the details of construction or design herein shown,
other than as described in the claims below. It is therefore
evident that the particular illustrative embodiments disclosed
above may be altered, combined, or modified and all such variations
are considered within the scope of the present disclosure. The
systems and methods illustratively disclosed herein may suitably be
practiced in the absence of any element that is not specifically
disclosed herein and/or any optional element disclosed herein.
While compositions and methods are described in terms of
"comprising," "containing," or "including" various components or
steps, the compositions and methods can also "consist essentially
of" or "consist of" the various components and steps. All numbers
and ranges disclosed above may vary by some amount. Whenever a
numerical range with a lower limit and an upper limit is disclosed,
any number and any included range falling within the range is
specifically disclosed. In particular, every range of values (of
the form, "from about a to about b," or, equivalently, "from
approximately a to b," or, equivalently, "from approximately a-b")
disclosed herein is to be understood to set forth every number and
range encompassed within the broader range of values. Also, the
terms in the claims have their plain, ordinary meaning unless
otherwise explicitly and clearly defined by the patentee. Moreover,
the indefinite articles "a" or "an," as used in the claims, are
defined herein to mean one or more than one of the element that it
introduces. If there is any conflict in the usages of a word or
term in this specification and one or more patent or other
documents that may be incorporated herein by reference, the
definitions that are consistent with this specification should be
adopted.
[0108] As used herein, the phrase "at least one of" preceding a
series of items, with the terms "and" or "or" to separate any of
the items, modifies the list as a whole, rather than each member of
the list (i.e., each item). The phrase "at least one of" allows a
meaning that includes at least one of any one of the items, and/or
at least one of any combination of the items, and/or at least one
of each of the items. By way of example, the phrases "at least one
of A, B, and C" or "at least one of A, B, or C" each refer to only
A, only B, or only C; any combination of A, B, and C; and/or at
least one of each of A, B, and C.
* * * * *