U.S. patent application number 16/382797 was filed with the patent office on 2019-08-01 for systems, methods, and apparatuses for downhole lateral detection using electromagnetic sensors.
The applicant listed for this patent is Saudi Arabian Oil Company. Invention is credited to Talha Jamal Ahmad, Muhammad Arsalan, Mohamed Nabil Noui-Mehidi.
Application Number | 20190235121 16/382797 |
Document ID | / |
Family ID | 56369201 |
Filed Date | 2019-08-01 |
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United States Patent
Application |
20190235121 |
Kind Code |
A1 |
Arsalan; Muhammad ; et
al. |
August 1, 2019 |
Systems, Methods, and Apparatuses for Downhole Lateral Detection
Using Electromagnetic Sensors
Abstract
Disclosed are systems, methods, and apparatuses to detect one or
more downhole laterals in a wellbore using electromagnetic sensors.
Certain embodiments include a subsurface unit including a
ruggedized encapsulation resistant to heat, pressure, and
variations in pH. The systems and apparatuses are communicable with
surface controls.
Inventors: |
Arsalan; Muhammad; (Dhahran,
SA) ; Ahmad; Talha Jamal; (Dhahran, SA) ;
Noui-Mehidi; Mohamed Nabil; (Dhahran, SA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Saudi Arabian Oil Company |
Dhahran |
|
SA |
|
|
Family ID: |
56369201 |
Appl. No.: |
16/382797 |
Filed: |
April 12, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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16051739 |
Aug 1, 2018 |
10324221 |
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16382797 |
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15188414 |
Jun 21, 2016 |
10061049 |
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16051739 |
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62183004 |
Jun 22, 2015 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
E21B 47/085 20200501;
E21B 47/13 20200501; G01V 3/28 20130101; E21B 41/0035 20130101 |
International
Class: |
G01V 3/28 20060101
G01V003/28; E21B 47/12 20060101 E21B047/12; E21B 41/00 20060101
E21B041/00; E21B 47/08 20060101 E21B047/08 |
Claims
1. A method for detecting lateral wellbores, the method comprising:
disposing, in a motherbore of a well, a subsurface unit comprising:
a control and communication system disposed at an uphole end of the
subsurface unit, the control and communication system comprising: a
wideband signal generator configured to generate electromagnetic
signals of frequencies within a wideband frequency range; a
controller; and a receiver; and a tool head disposed in a downhole
end of the subsurface unit, the tool head being detachably coupled
to the control and communication system, the tool head comprising a
wideband antenna configured to generate electromagnetic pulses
having frequencies within the wideband frequency range;
controlling, by the controller, the wideband signal generator to
generate an electromagnetic signal of a given frequency within the
wideband frequency range; receiving, by the wideband antenna, a
signal corresponding to the electromagnetic signal of the given
frequency; radiating, by the wideband antenna, into the environment
surrounding the subsurface unit, an electromagnetic pulse
corresponding to the signal, the electromagnetic pulse being of the
given frequency; detecting, by the wideband antenna, one or more
reflections resulting from the radiation of the electromagnetic
pulse into the environment surrounding the subsurface unit;
providing, by the wideband antenna to the receiver, one or more
reflection signals corresponding to the one or more reflections
detected; receiving, by the receiver, the one or more reflection
signals; and providing, by the receiver to a processing module, one
or more data signals corresponding to the one or more reflection
signals, the processing module configured to determine, based on
the one or more data signals, whether a lateral is present in the
environment surrounding the subsurface unit.
2. The method of claim 1, further comprising detaching the control
and communication system from the tool head.
3. The method of claim 2, wherein the control and communication
system is detached from the tool head in response to the tool head
being lodged in a wellbore of the well.
4. The method of claim 1, further comprising: controlling, by the
controller, the wideband signal generator to generate a second
electromagnetic signal of a second given frequency within the
wideband frequency range; receiving, by the wideband antenna, a
second signal corresponding to the second electromagnetic signal of
the second given frequency; radiating, by the wideband antenna,
into a second environment surrounding the subsurface unit, a second
electromagnetic pulse corresponding to the second signal, the
second electromagnetic pulse being of the second given frequency;
detecting, by the wideband antenna, one or more second reflections
resulting from the radiation of the second electromagnetic pulse
into the second environment surrounding the subsurface unit;
providing, by the wideband antenna to the receiver, one or more
second reflection signals corresponding to the one or more second
reflections detected; receiving, by the receiver, the second one or
more reflection signals; and providing, by the receiver to the
processing module, one or more second data signals corresponding to
the one or more second reflection signals, the processing module
configured to determine, based on the one or more second data
signals, whether a lateral is present in the second environment
surrounding the subsurface unit.
5. The method of claim 4, wherein the environment surrounding the
subsurface unit comprises a first portion of a motherbore of a
first well, and the second environment surrounding the subsurface
unit comprises a second portion of the motherbore of the first
well.
6. The method of claim 4, wherein the environment surrounding the
subsurface unit comprises a portion of a motherb ore of a first
well, and the second environment surrounding the subsurface unit
comprises a portion of a motherbore of a second well.
7. The method of claim 1, further comprising the processing module
determining that a lateral is present in the environment based on
the one or more data signals.
8. The method of claim 1, further comprising: the processing module
determining that a lateral is present in the environment
surrounding the subsurface unit based on the one or more data
signals indicating that the one or more reflections resulting from
the radiation of the electromagnetic pulse into the environment
surrounding the subsurface unit are relatively weak.
9. The method of claim 1, further comprising: the processing module
determining that a lateral is not present in the environment
surrounding the subsurface unit based on the one or more data
signals indicating that the one or more reflections resulting from
the radiation of the electromagnetic pulse into the environment
surrounding the subsurface unit are relatively strong.
10. The method of claim 1, wherein the subsurface unit comprises
the processing module.
11. The method of claim 1, wherein the processing module is located
in a surface unit.
Description
RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 16/051,739 filed on Aug. 1, 2018 and titled
"SYSTEMS, METHODS, AND APPARATUSES FOR DOWNHOLE LATERAL DETECTION
USING ELECTROMAGNETIC SENSORS", which is a continuation of U.S.
patent application Ser. No. 15/188,414 filed on Jun. 21, 2016 and
titled "SYSTEMS, METHODS, AND APPARATUSES FOR DOWNHOLE LATERAL
DETECTION USING ELECTROMAGNETIC SENSORS", which claims the benefit
of U.S. Provisional Patent Application No. 62/183,004 filed on Jun.
22, 2015 and titled "SYSTEMS, METHODS, AND APPARATUSES FOR DOWNHOLE
LATERAL DETECTION USING ELECTROMAGNETIC SENSORS", which are hereby
incorporated by reference in their entireties.
FIELD OF INVENTION
[0002] Embodiments relate to oil and gas exploration and, more
particularly, to downhole tools.
BACKGROUND OF THE INVENTION
[0003] In recent years, it has become possible to drill and
maintain increasingly complicated wellbores. In some cases, rather
than drilling multiple vertical wells, it may be advantageous to
drill relatively fewer vertical wells, but branch out from these
vertical wells with a greater number of lateral wells. Hence, a
primary wellbore with laterals branching out from it can provide
the coverage desired of a downhole formation at less expense and
time than would be needed to achieve the same coverage with
multiple vertical wells. The savings in time and money, however,
are accompanied by new challenges. Indeed, as the number of
laterals branching from a primary wellbore increases, so too does
the difficulty of locating and entering specific laterals.
[0004] One proposed solution involves the installation of special
fixtures in the casing. The fixtures may be installed at the
connection point between a lateral and the primary wellbore,
thereby to allow for the landing of an intervention tool at the
connection point. Another proposed technique involves a specialized
downhole contraption, which includes an indexing tool, a kickover
knuckle joint attached at the lower end of the indexing tool, and a
wand attached at the lower end of the kickover knuckle joint. The
contraption may be lowered into a primary wellbore at the end of
coiled tubing. A user may tag the bottom of the primary wellbore in
order to establish a maximum depth. Then, the contraption may be
raised to the estimated location of a connection between a lateral
wellbore and the primary wellbore. At that point, the kickover
knuckle joint may be used to deflect the wand away from the
longitudinal axis of the downhole contraption, and the contraption
may be raised or lowered in the primary wellbore. To orient the
contraption in the primary wellbore, the indexing tool may be used
to rotate the wand relative to the coiled tubing. If a lateral is
located, the tip of the wand may be fully bent into the lateral.
When the wand is fully bent, pressurizing fluid in the downhole
contraption may be vented, which can provide a surface indication
to the user that a lateral wellbore has been located.
SUMMARY OF THE INVENTION
[0005] Applicant has recognized a number of problems in current
approaches to detect laterals. For example, Applicant has
recognized that the kickover and wand technique suffers from a
number of shortcomings. First, this technique is prone to error as
an operator can fail to locate a lateral simply because an
inappropriate wand length was chosen. In addition, Applicant has
recognized that these downhole contraptions do not include means
for accurate downhole depth control and yet rely heavily on such
depth control to detect laterals. Hence, Applicant has recognized
that this method can be highly inaccurate. In addition, the
kickover and wand technique is expensive, and the added cost
provides little in the way of added benefit.
[0006] Furthermore, the technique involving installation of special
fixtures in a casing requires, of course, a casing. If primary
casing has been installed, but is not yet cemented in place, these
fixtures cannot be installed. Moreover, there can be situations in
which the primary casing has not been installed at all. For
example, an operator might want to access a lateral directly from
an open-hole, or uncased, wellbore. In these situations, Applicant
has recognized that the special fixture technique cannot be used.
Hence, this technique can be used only at certain stages of
development, and then only at great cost. Applicant has recognized
that these costs negate some of the synergies provided by
multilateral wells in the first place. Moreover, Applicant has
recognized the need for systems, methods, and apparatuses to detect
laterals at all stages of development of a multilateral well in a
cost-effective matter.
[0007] Having recognized these and other problems, Applicant
proposes systems, methods, and apparatuses for enhanced and
economical detection of laterals. Embodiments can include a
subsurface unit, a surface unit, and a wireline or coil tubing
operably connecting the two. At times in this application, the
subsurface unit is referred to as a lateral detection tool. It will
be understood that the subsurface unit or lateral detection tool,
as with other components discussed in this application, can be made
and used independently of other components, and such manufacture
and use is within the scope of the invention. Moreover, it will be
understood by one skilled in the art that the steps performed by
each of the components discussed in this application, including
combinations of steps and sub-combinations, can form the steps of
one or more methods to detect laterals according to
embodiments.
[0008] In embodiments, the subsurface unit includes a ruggedized
encapsulation. The subsurface unit can be introduced into a
motherbore through a motherbore surface entry and have an uphole
end and a downhole end relative to the motherbore surface entry.
According to embodiments, the ruggedized encapsulation can be
high-temperature resistant, high-pressure resistant, and acid
resistant.
[0009] In embodiments, the subsurface unit includes a control and
communication subsystem disposed within the uphole end of the
subsurface unit. The control and communication subsystem can
include a controller adapted to control operations of the
subsurface unit and a signal generator adapted to generate a
wideband electromagnetic signal. The control and communication
subsystem further can include a modulator responsive to the
controller and the signal generator and adapted to modulate the
wideband electromagnetic signal in order to generate a modulated
signal. In addition, the control and communication subsystem can
include a transmitter responsive to the controller and the
modulator and adapted to transmit the modulated signal to an
antenna via a duplexer. The duplexer can be responsive to the
controller and the transmitter and adapted to allow for a
bidirectional signal path. The control and communication subsystem
further can include a receiver responsive to the controller and the
duplexer and adapted to detect reflections of an electromagnetic
pulse conveyed to the receiver from one or more antennas via the
duplexer. The reflections of the electromagnetic pulse characterize
a received signal. In embodiments, the control and communication
subsystem can include a demodulator responsive to the controller
and adapted to demodulate the received signal, thereby to generate
a demodulated signal. Moreover, the control and communication
subsystem can include a communication module adapted to receive the
demodulated signal and communicate the demodulated signal to the
surface unit as will be discussed more thoroughly in a succeeding
paragraph.
[0010] According to embodiments, the subsurface unit also can
include a tool head disposed within the downhole end of the
subsurface unit. The tool head can include one or more wideband
antennas. "Antenna," as used in this application, can refer to one
or multiple electromagnetic antennas. The term also can refer to a
plurality of electromagnetic antennas arranged in an antenna array.
For example, it is within the scope of the term "antenna," and
within the scope of the invention, to include one or more
transmitting antennas and one or more receiving antennas in an
antenna array. For brevity and clarity, Applicant uses the term
"antenna" to refer to these and other embodiments. For example, it
is within the scope of the invention to employ an antenna that
includes a single antenna, multiple antennas, or an antenna array.
Antennas in an array can take many configurations, including phased
arrays, dipole arrays, and other configurations that will be
apparent to one of skill in the art upon reading this disclosure.
The one or more wideband antennas can be responsive to the duplexer
and the transmitter and adapted to convert the modulated signal
transmitted by the transmitter via the duplexer into an
electromagnetic pulse. The one or more antennas further can be
adapted to radiate the electromagnetic pulse through a downhole
environment. In addition, the one or more wideband antennas can be
adapted to detect reflections of the electromagnetic pulse and
convey the reflections of the electromagnetic pulse to the receiver
via the duplexer.
[0011] Embodiments can include a wireline or coiled tubing adapted
to allow for data and power transfer. According to embodiments, the
surface unit can include one or more processors adapted to receive
data from the communication module via the wireline. The surface
unit further can include one or more displays in communication with
the one or more processors and tangible computer-readable medium in
communication with the one or more processors. The tangible
computer-readable medium can have stored internally a plurality of
operational modules, including a signal processing module adapted
to process the demodulated signal thereby to detect the presence
and location of laterals and sidetracks in the downhole
environment. According to embodiments, the one or more displays can
be adapted to display the presence and location of laterals and
sidetracks in the downhole environment.
[0012] In some embodiments, provided is a system for detecting
lateral well bores that includes a subsurface unit adapted to be
disposed in a motherbore of a well The subsurface unit including a
controller, a receiver, and a wideband antenna. The wideband signal
generator adapted to generate electromagnetic signals of
frequencies within a wideband frequency range. The controller
adapted to identify a first frequency within the wideband frequency
range, and control the wideband signal generator to cause the
wideband signal generator to generate a first electromagnetic
signal of the first frequency. The receiver adapted to receive
signals corresponding to reflections resulting from radiation of
electromagnetic pulses into an environment surrounding the
subsurface unit. The wideband antenna adapted to generate
electromagnetic pulses having frequencies within the wideband
frequency range. The wideband antenna further adapted to receive a
first signal corresponding to the first electromagnetic signal of
the first frequency, radiate, into a first environment surrounding
the subsurface unit, a first electromagnetic pulse (of the first
frequency) corresponding to the first signal corresponding to the
first electromagnetic signal, and to detect one or more first
reflections resulting from the radiation of the first
electromagnetic pulse into the first environment surrounding the
subsurface unit. The antenna further adapted to provide one or more
first reflection signals corresponding to the one or more first
reflections to the receiver. The receiver being adapted to provide
the one or more first data signals corresponding to the one or more
first reflection signals to a processing module. The processing
module being adapted to determine whether a lateral is present in
the first environment based at least in part on the one or more
first data signals corresponding to the one or more first
reflection signals.
[0013] In certain embodiments, the controller is further adapted to
identify a second frequency within the wideband frequency range,
and control the wideband signal generator to cause the wideband
signal generator to generate a second electromagnetic signal of the
second frequency. The wideband antenna being further adapted to
receive a second signal corresponding to the second electromagnetic
signal of the second frequency, radiate, into a second environment
surrounding the subsurface unit, a second electromagnetic pulse (of
the second frequency) corresponding to the second signal
corresponding to the second electromagnetic signal, and detect one
or more second reflections resulting from the radiation of the
second electromagnetic pulse into the second environment
surrounding the subsurface unit. The antenna further adapted to
provide, to the receiver, one or more second reflection signals
corresponding to the one or more second reflections. The receiver
being adapted to provide one or more second data signals
corresponding to the one or more second reflection signals to the
processing module. The processing module being adapted to determine
whether a lateral is present in the second environment based at
least in part on the one or more second data signals corresponding
to the one or more second reflection signals.
[0014] In some embodiments, the first environment is a first
portion of a motherbore of a first well, and the second environment
is a second portion of the motherbore of the first well. In some
embodiments, the first environment is a portion of a motherbore of
a first well, and the second environment is a portion of a
motherbore of a second well.
[0015] In certain embodiments, the system includes the processing
module adapted to determine that a lateral is present in the first
environment in response to determining that the one or more first
reflections are relatively weak, and to determine that a lateral is
not present in the first environment in response to determining
that the one or more first reflections are relatively strong.
[0016] In some embodiments, the subsurface unit further includes: a
modulator adapted to modulate the first electromagnetic signal of
the first frequency to generate a first modulated signal, a
transmitter adapted to transmit the first modulated signal to the
duplexer, and the duplexer adapted to receive the first modulated
signal from the transmitter and transmit the first modulated signal
to the wideband antenna. The receiving, by the wideband antenna, of
the first signal corresponding to the first electromagnetic signal
of the first frequency comprising receiving the first modulated
signal form the duplexer. In certain embodiments, the duplexer is
adapted to receive, from the wideband antenna, one or more first
antenna signals corresponding to the one or more first reflections
resulting from the radiation of the first electromagnetic pulse
into the first environment surrounding the subsurface unit and to
transmit the one or more first antenna signals to the receiver, the
receiver is adapted to receive the one or more first antenna
signals from the duplexer and to transmit the one or more first
antenna signals to the demodulator, and the subsurface unit further
includes the demodulator adapted to demodulate the one or more
first antenna signals received from the receiver to generate one or
more first demodulated antenna signals and to transmit the one or
more first demodulated antenna signals to the processing module,
the one or more first data signals provided to the processing
module corresponding to the one or more first demodulated antenna
signals.
[0017] In some embodiments, the system further includes a surface
unit including the processing module, and the subsurface unit
further is adapted to determine whether a connection between the
communication module and the surface unit is available, and
communicate, in response to determining that a connection between
the communication module and the surface unit is available, the one
or more first data signals to the processing module of the surface
unit.
[0018] In certain embodiments, the system further includes a
surface unit and the subsurface unit further includes the
processing module. The processing module adapted to generate
lateral data indicative of whether a lateral is present in the
first environment based at least in part on the one or more first
data signals corresponding to the one or more first reflection
signals. The subsurface unit further adapted to determine whether a
connection between the communication module and the surface unit is
available, and communicate, in response to determining that a
connection between the communication module and the surface unit is
available, the lateral data to the surface unit.
[0019] In some embodiments, the wideband frequency range has a
bandwidth of about 5 gigahertz (GHz). In some embodiments, the
wideband frequency range has a range of about 1 kilohertz (KHz) to
about 5 GHz. In certain embodiments, the controller is further
adapted to identify a first transmission power for the first
electromagnetic signal, and control the wideband signal generator
to cause the wideband signal generator to generate the first
electromagnetic signal of the first frequency and the first
transmission power. In certain embodiments, the first transmission
power is determined based on one or more of the following
characteristics of the first environment: type of formation, prior
resistivity log, or wellbore hole (or opening) diameter.
[0020] In some embodiments, a method is provided that includes
identifying a first frequency within a wideband frequency range of
a wideband signal generator and a wideband antenna of a subsurface
unit (the first frequency being determined based on characteristics
of a first motherbore environment). The method includes, when the
unit is disposed in the first motherbore environment: generating,
by the wideband signal generator, a first electromagnetic signal of
the first frequency; radiating, by the wideband antenna of the
subsurface unit, a first electromagnetic pulse corresponding to the
first electromagnetic signal (the first electromagnetic pulse being
of the first frequency); and detecting, by the wideband antenna of
the subsurface unit, one or more first reflections resulting from
the radiation of the first electromagnetic pulse. A determination
of whether a lateral is present in the first motherbore environment
being based at least in part on the one or more first reflections
detected. The method also including identifying a second frequency
within the wideband frequency range of the wideband signal
generator and the wideband antenna of the subsurface unit (the
second frequency being determined based on characteristics of a
second motherbore environment). The method includes, when the unit
is disposed in the second motherbore environment: generating, by
the wideband signal generator, a second electromagnetic signal of
the second frequency; radiating, by the wideband antenna of the
subsurface unit, a second electromagnetic pulse corresponding to
the second electromagnetic signal (the second electromagnetic pulse
being of the second frequency); and detecting, by the wideband
antenna of the subsurface unit, one or more second reflections
resulting from the radiation of the first electromagnetic pulse. A
determination of whether a lateral is present in the second
environment being based at least in part on the one or more second
reflections detected.
[0021] In some embodiments, the first motherbore environment is a
first portion of a motherbore of a first well, and the second
motherbore environment is a second portion of the motherbore of the
first well. In some embodiments, the first motherbore environment
is a portion of a motherbore of a first well, and the second
motherbore environment is a portion of a motherbore of a second
well.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] These and other features, aspects, and advantages of the
present invention will become better understood with regard to the
following descriptions, claims, and accompanying drawings in which
like numbers represent like components. It is to be noted, however,
that the drawings illustrate only several embodiments and are not
to be considered limiting of the invention's scope as the invention
comprises other effective embodiments.
[0023] FIG. 1 is a schematic diagram of a system that depicts a
surface unit with a signal processing module disposed internally, a
subsurface unit, and a wireline operably connecting the two,
according to an embodiment;
[0024] FIG. 2 is a schematic diagram of a system that depicts a
surface unit, a subsurface unit with a signal processing module
disposed internally, and a wireline operably connecting the two,
according to an embodiment;
[0025] FIG. 3 is a schematic diagram of a subsurface unit according
to an embodiment;
[0026] FIGS. 4A-C are schematic diagrams of subsurface units
introduced into various downhole environments according to
embodiments;
[0027] FIG. 5A is a schematic diagram of a system with an
application-specific integrated circuit (ASIC) according to an
embodiment;
[0028] FIG. 5B is a schematic diagram of an example ASIC according
to an embodiment;
[0029] FIG. 6 is a flowchart diagram that depicts a method to
detect a lateral in a well according to an embodiment; and
[0030] FIG. 7 is a flowchart that illustrates a method for
generating a wideband electromagnetic signal according to an
embodiment.
DETAILED DESCRIPTION
[0031] So that the manner in which the features and advantages of
the embodiments of systems, methods, and apparatuses of the present
invention, as well as others, which will become apparent, may be
understood in more detail, a more particular description of the
embodiments briefly summarized in the preceding section may be had
by reference to the embodiments thereof, which are illustrated in
the appended drawings, which form a part of this specification. It
is to be noted, however, that the drawings illustrate only various
embodiments of the embodiments and, therefore, are not to be
considered limiting of the embodiments of the present invention's
scope as the invention includes other effective embodiments as
well.
[0032] FIGS. 1 and 2 depict system embodiments. To provide a
clearer disclosure, these figures are discussed together for the
most part, with differences being highlighted. System embodiments
can include a subsurface unit 300, 300', a surface unit 100, 100',
and a wireline 110, 110' or coil tubing (not pictured) operably
connecting the subsurface unit 300, 300' and the surface unit 100,
100'. In embodiments, the subsurface unit 300, 300' includes a
ruggedized encapsulation 305, 305'. The ruggedized encapsulation
305, 305' protects components of the subsurface unit 300, 300' from
elements in the downhole environment, but permits the transmission
of electromagnetic signals. In embodiments, the ruggedized
encapsulation 305, 305' is constructed using a non-ferromagnetic
downhole material that can be machined or printed. For example, in
embodiments the ruggedized encapsulation 305, 305' can be
constructed partially or wholly with polyether ether ketone
(PEEK).
[0033] In embodiments, the subsurface unit 300, 300' includes a
control and communication subsystem 310, 310' disposed within the
uphole end of the subsurface unit 300, 300'. Uphole and downhole,
as used in this application, refer to components' relative distance
to a motherbore surface entry when the subsurface unit 300, 300' is
introduced into a motherbore. More detail will be provided with
reference to FIGS. 4A-C. To orient the reader, however, it is noted
that uphole components relative to the motherbore surface entry can
be thought of as elevationally above downhole components relative
to the motherbore surface entry when the subsurface unit 300, 300'
is oriented vertically in the motherbore. For example, the downhole
end of the subsurface unit 300 may refer to a front/head portion of
the subsurface unit 300 that enters and travels through the
motherbore ahead of the uphole end of the subsurface unit 300. The
uphole end of the subsurface unit 300 may refer to a rear/tail
portion of the subsurface unit 300 that enters and travels through
the motherbore behind the downhole end of the subsurface unit
300.
[0034] The control and communication subsystem 310, 310' can
include a controller 114, 114' configured to control operations of
the subsurface unit 300, 300' and a signal generator 116, 116'
configured to generate an electromagnetic signal. According to
embodiments, the electromagnetic (EM) signal is of a frequency that
falls within the frequency range of a wideband signal source used
to generate the signal, such as a wideband signal generator and the
wideband antenna ultimately used to transmit the signal. In some
embodiments, a signal source may emit wideband frequencies. In such
an embodiment, a narrower frequency of interest (within the
wideband frequency) may be analyzed based on the reflections
received at the receiver. The control and communication subsystem
310, 310' further can include a modulator 118, 118' responsive to
(e.g., controlled by) the controller 114, 114' and the signal
generator 116, 116' and configured to modulate the electromagnetic
signal, thereby to generate a modulated signal. In addition, the
control and communication subsystem 310, 310' can include a
transmitter 120, 120' responsive to the controller 114, 114' and
the modulator 118, 118' and configured to transmit the modulated
signal to an antenna 124, 124' via a duplexer 122, 122'. By using a
wideband signal generator 116, 1116' and a wideband antenna (e.g.,
including multiple antennas, such as a wideband antenna array) 124,
124', a wide bandwidth can be achieved, which, in turn, can be used
to facilitate a wide range of signal frequencies. This ensures the
proper frequencies for a given environmental condition can be
achieved. For example, a signal frequency that is appropriate for
the environmental conditions in which the subsurface unit 300, 300'
is located in can be selected from the wide range of frequencies
available with the signal generator 116, 116' (e.g., a wideband
signal generator) and the antenna 124, 124' (e.g., a wideband
antenna arrangement), and a signal of the selected frequency can be
generated and transmitted as described herein. Moreover, an antenna
array 124, 124' can offer precise control over various pulse
parameters, including the size, power, polarization, and beam angle
of the radiated pulse. Similar to the signal frequency, this can
further ensure proper pulse parameters for a given environmental
condition can be achieved. The wideband signal generator 116, 116'
may have a maximum operational frequency of about 5 GHz, and/or a
minimum operational frequency of about 1 KHz. The wideband signal
generator 116, 116' may have a bandwidth of about 5 GHz. For
example, the wideband signal generator 116, 116' can have an
operational frequency range of about 1 KHz to about 5 GHz. That is,
the wideband signal generator 116, 116' may be operable to generate
an electromagnetic signal having a frequency in the range of about
1 KHz to about 5 GHz. The wideband antenna 124, 124' may have a
maximum operational frequency of about 5 GHz, and/or a minimum
operational frequency of about 1 KHz. The wideband antenna 124,
124' may have a bandwidth of about 5 GHz. For example, the wideband
antenna 124, 124' can have an operational frequency range of about
1 KHz to about 5 GHz. That is, the wideband antenna (or antenna
array) 124, 124' may be operable to transmit an electromagnetic
signal having a frequency in the range of about 1 KHz to about 5
GHz. The signal generator 116, 116' and antenna 124, 124' described
may include a wideband signal generator and wideband antenna
although sometime referred to simply as a signal generator and an
antenna, respectively. The wideband antenna 124, 124' can be a
single antenna, such as fractal antenna, or a an array of antennas
covering the complete bandwidth (e.g., about 1 KHz to about 5
GHz).
[0035] The duplexer 122, 122' can be responsive to the controller
114, 114' and the transmitter 120, 120' and configured to allow for
a bidirectional signal path. In other words, the duplexer 122, 122'
can allow a signal from the transmitter 120, 120' to be radiated by
the antenna 124, 124' and further can allow reflected signals
detected by the antenna 124, 124' to be detected by the receiver
126, 126'. The receiver 126, 126', which also can be included
within the control and communication subsystem 310, 310', can be
responsive to the controller 114, 114' and the duplexer 122, 122'
and configured to detect reflections of an electromagnetic pulse
combined and transmitted to the receiver 126, 126' from one or more
antennas 124 via the duplexer 122, 122'. The reflections of the
electromagnetic pulse characterize a received signal. In
embodiments, the control and communication subsystem 310, 310' can
include a demodulator 128, 128' responsive to the controller 114,
114' and configured to demodulate the received signal, thereby to
generate a demodulated signal. Moreover, the control and
communication subsystem 310, 310' can include a communication
module 112, 112' configured to receive the demodulated signal and
communicate the demodulated signal to the surface unit 100, 100' as
discussed herein.
[0036] According to embodiments, the subsurface unit 300, 300' also
can include a tool head 320, 320' disposed within the downhole end
of the subsurface unit 305, 305'. The one or more antennas 124,
124' previously noted can be disposed within the tool head 320,
320'. In this manner, reusable, costly components, including
circuitry, are included in the control and communication subsystem
310, 310', while the one or more wideband antennas 124, 124' are
segregated into the tool head 320, 320'. Thus, in embodiments the
tool head 320, 320' can be sacrificed inside the lateral, and the
control and communication subsystem 310, 310' can be recovered. For
example, the tool head 320, 320' may be a module that is detachable
from the communication subsystem 310, 310', and during operation,
the tool head 320, 320' may be physically separated from the
communication subsystem 310, 310' such that it remains in the
lateral or wellbore, and the communication subsystem 310, 310' is
retrievable without the tool head 320, 320'. This may be
advantageous, for example, if the tool head 320, 320' becomes
lodged in the lateral or wellbore such that it is not immediately
retrievable, and the communication subsystem 310, 310' can be
retrieved from the lateral or wellbore via detachments from the
tool head 320, 320'. It is within the scope of the invention to
employ a single antenna, multiple antennas, or an antenna array in
the tool head 320, 320'. The one or more wideband antennas 124,
124' can be responsive to the duplexer 122, 122' and the
transmitter 120, 120' and be configured to convert the modulated
signal transmitted by the transmitter 120, 120' via the duplexer
into an electromagnetic pulse. The one or more wideband antennas
124, 124' further can be configured to radiate the electromagnetic
pulse through a downhole environment. In addition, the one or more
wideband antennas 124, 124' can be configured to detect reflections
of the electromagnetic pulse and combine and transmit signals
corresponding to the reflections of the electromagnetic pulse to
the receiver 126, 126' via the duplexer 122, 122'.
[0037] Embodiments can include a wireline 110, 110' or coiled
tubing configured to allow for data and power transfer. For
example, settings of the controller 114, 114' can be adjusted via
the wireline 110, 110'. In addition, data transferred via the
wireline 110, 110' can be used to convey data regarding the
operational status of various components of the subsurface unit
300, 300'. It will be understood by one skilled in the art that
various other power and data channels can be used in place of the
wireline 110, 110' while staying within the scope of the invention.
For example, according to embodiments, the subsurface unit 300,
300' is powered by an internally-disposed battery. Meanwhile, data
can be transferred between the subsurface unit 300, 300' and the
surface unit 100, 100' via a cable optimized for data transfer or,
in embodiments, wirelessly.
[0038] According to embodiments, the surface unit 100, 100' can
include one or more processors 102, 102' configured to receive data
from the communication module 112, 112' via the wireline 110, 110'.
The surface unit 100, 100' further can include one or more displays
104, 104' in communication with the one or more processors 102,
102'.
[0039] In embodiments, the surface unit 100 includes tangible
computer-readable medium 106 in communication with the one or more
processors 102. The tangible computer-readable 106 medium can have
stored internally a plurality of operational modules, including a
signal processing module 108 configured to process the demodulated
signal thereby to detect the presence and location of laterals and
sidetracks in the downhole environment. Such a configuration can
resemble the configuration illustrated schematically in FIG. 1. In
other embodiments, including, for example, that shown in FIG. 2,
tangible computer-readable medium 106' and embedded signal
processing module 108' can be included in subsurface unit 300'.
Hence, for example, if a reliable high speed data link is not
available, signal processing module 108' can process the
demodulated signal locally in the subsurface unit 300'. The
processed demodulated signal then can be transmitted to the
communication module 112', where data embodying the processed
signal will remain until a reliable data channel allows
communication of the processed signal to the surface unit 100'. The
communication module 112, 112' can include modules operable to both
receive and transmit data, including, for example,
transmitter-receivers and transceivers. One or more additional
communication modules, not pictured, can be used to relay power or
data to the subsurface unit 300, 300' or to relay data from the
subsurface unit 300, 300' to the surface unit 100, 100', for use by
the one or more processors 102, 102'. Various digital and analog
communication protocols known to those skilled in the art can be
used to manage communication between units. According to
embodiments, the one or more displays 104, 104' can be configured
to display the presence and location of laterals and sidetracks in
the downhole environment.
[0040] One possible configuration of the components discussed in
this application is shown in FIG. 3. The subsurface unit 300'',
otherwise known as a lateral detection tool 300'', is depicted
oriented horizontally with the tool head 320'' (e.g., a
downhole/front/head portion of the subsurface unit 300'' depicted
on the right side of FIG. 3). The tool head 320'' may refer to a
downhole/front/head portion of the subsurface unit 300'' that
enters and travels through the motherbore ahead of a tool tail
322'' of the subsurface unit 300'' (e.g., an uphole/rear/tail
portion of the subsurface unit 300'' depicted on the left side of
FIG. 3). Thus, the tool tail 322'' may refer to a portion of the
subsurface unit 300'' that enters and travels through the
motherbore behind the tool head 320'' of the subsurface unit 300''.
In operation, the tool head 320'' can be the leading/lowest portion
of the lateral detection tool 300'', though this does not have to
be the case, as in, for example, when the lateral detection tool
300'' enters a detected lateral. That is, when the lateral
detection tool 300'' is introduced into a motherbore by the
wireline 110'' or coil tubing, the lateral detection tool 300'' can
have a substantially vertical profile with the tool head 320''
elevationally below the control and communication subsystem 310''.
As noted, the wireline 110'' or coil tubing can allow for power and
bi-directional communication for commands, controls, and data
transfer. The control and communication subsystem 310'' can include
a signal processing module, for example, according to the internal
configuration shown in FIG. 2. In embodiments, the signal
processing module can be located elsewhere, for example, according
to the configuration shown in FIG. 1. In either case, the lateral
detection tool 300'' includes a ruggedized encapsulation 305''.
According to embodiments, the ruggedized encapsulation 305'' can be
high-temperature resistant, high-pressure resistant, and acid
resistant. The ruggedized encapsulation 305'' can be constructed
non-uniformly in some embodiments. For example, conductive alloys
(e.g., EM conductive alloys or polymers) can be built into the
ruggedized encapsulation at the tool head 320'' to aid the one or
more antennas in both radiating an electromagnetic pulse and
detecting reflections of the electromagnetic pulse. Certain
configurations may be favored if the lateral detection tool 300''
communicates wirelessly with a surface unit. For example,
additional metals (e.g., carbon fiber with PEEK) can be included in
the ruggedized encapsulation 305'' to ensure enhanced reception of
wireless signals. In some embodiments, the antenna 124 may be
oriented to direct the generated signal laterally (e.g., at least
partially in a direction ahead of the lateral detection tool 300'',
such as in the direction of arrow 330'', such that the signal
encounters lateral portions of the motherbore adjacent the tool
300'') and/or longitudinally (e.g., at least partially in a
direction ahead of the lateral detection tool 300'', such as in the
direction of arrow 332'') such that the signal encounters downhole
portions of the motherbore ahead of the tool 300''. Such a
longitudinal signal can, for example, enable the detection of a
lateral before the lateral detection tool 300'' is adjacent the
lateral. For example, if an upper wall of a lateral intersects a
motherbore at a depth of about 1000 meters in the motherbore, the
lateral may be detected when the tool head 320'' of the detection
tool 300'' is located at a depth of about 999 meters in the
motherbore.
[0041] According to embodiments, the subsurface unit 400, 400',
400'' can be introduced into a motherbore 450, 450', 450'' through
a motherbore surface entry 405, 405', 405'' and have an uphole end
and a downhole end relative to the motherbore surface entry 405,
405', 405''. Subsurface units 400, 400', 400'' oriented as such and
in operation are shown, for example, in FIGS. 4A-C, though it will
be understood by one skilled in the art that other orientations are
possible. For example, a subsurface unit 400, 400', 400'' can be
disposed within a lateral after such a lateral is detected. It will
be understood in that event that the subsurface unit 400, 400',
400'' will have a non-vertical absolute profile, but it still will
have an uphole/downhole perspective with respect to a device axis
that is substantially parallel with the axis of the wellbore in
which the device is positioned. Indeed, if the subsurface unit 400,
400', 400'' enters a sidetrack, the subsurface unit 400, 400',
400'' can be oriented horizontally. Hence, it will be understood
that portions of the of the subsurface unit 400, 400', 400''
referred to as uphole and those referred to as downhole can, at
times, have a substantially similar absolute distance to the
motherbore surface entry 405, 405', 405''. In other words, uphole
and downhole are not used in an absolute elevation sense. Rather
these terms orient the reader as to the relative positions of
components in the subsurface unit 400, 400', 400'' with respect to
the motherbore surface entry.
[0042] Advantageously, embodiments can distinguish between various
types of multilateral wells. For example, FIGS. 4A-C show a lateral
detection tool 400, 400', 400'' in communication with a wireline
408, 408', 408'' and deployed within a motherbore 450, 450', 450''
adjacent a lateral 460, 460', 460''. A radiated electromagnetic
pulse 410, 410', 410'' strikes surrounding objects in the
environment430, 430', 430'' (e.g., including walls of casing or
liner 432, 432', and the surrounding formation 434, 434', 434'',
including the walls of the bores 436, 436', 436''). Detected
reflections of the electromagnetic pulse 420, 420', 420'' are
received by one or antennas in the lateral detection tool 400,
400', 400''. According to embodiments, processing the received
signal provides information that can be used to determine the
location and orientation of the lateral 460, 460', 460'' with
respect to the motherbore 450, 450', 450''.
[0043] Moreover, advantageously, processing the received signal can
provide an accurate representation of detected laterals regardless
of the type of motherbore and type of lateral. For example,
embodiments accurately portray the presence and location of a cased
lateral 460 adjacent a cased motherbore 450, as shown in the
configuration of FIG. 4A. Moreover, embodiments accurately portray
the presence and location of an open-hole lateral 460' adjacent a
cased motherbore 450' as shown in the configuration of FIG. 4B.
Still further, embodiments accurately portray the presence and
location of an open-hole lateral 460'' adjacent an open-hole
motherbore 450'' as shown in the configuration of FIG. 4C.
[0044] Certain features of the electromagnetic pulse 410, 410',
410'' contribute to such functionality. For example,
electromagnetic waves are often not used in the presence of water,
particularly as salinity increases, due to high attenuation of the
electromagnetic signal. This aspect of electromagnetic waves is
employed advantageously in embodiments, however. Indeed, by using a
wideband signal source and a wideband antenna, a wide range of
frequencies can be achieved. The wide range of transmitted signal
frequencies permits calibration of the electromagnetic pulse at a
frequency determined to minimize attenuation of the transmitted and
reflected signals in the downhole environment. Moreover, because
the signal travel distance, or the distance between the antenna and
detectable objects, can be a few inches in the downhole
environment, some degree of attenuation can be beneficial. In other
words, embodiments include tuning the one or more antennas such
that attenuation increases at a certain threshold distance greater
than the distance between the antennas and detectable objects. This
prevents noise from far-off objects from interfering with the
detection of detectable laterals. Put another way, some degree of
attenuation offers a favorable signal to noise ratio, which enables
more accurate detection of the entryway for a lateral along the
motherbore wall.
[0045] In addition, a combination of transmitted power and
frequency, as well as other features of the lateral detection
algorithm allow for the detection of the various lateral openings
discussed with reference to FIGS. 4A-C. For example, the lateral
detection algorithm, in part, involves calculating the power of the
signal returning to the one or more antennas 124, 124' (FIGS. 1-2).
The general radar equation can be modified when the transmitting
antenna and receiving antenna are in the same location. The
resulting equation in this case is given by Equation (1):
P r = P t G t A r .sigma. F 4 ( 4 .pi. ) 2 R 4 ( 1 )
##EQU00001##
[0046] In this application of the radar equation, P.sub.r=received
power, P.sub.t=transmitter power; G.sub.t=gain of transmitter
antenna; A.sub.r=effective aperture (area) of the receiving
antenna; F=pattern propagation factor; .sigma.=radar cross section,
or scattering coefficient, of the target; and R=range.
[0047] The lateral detection algorithm further considers that the
lateral detection tool 400, 400', 400' can perform while moving
towards or away from the opening of a lateral 460, 460', 460''. In
these situations, the lateral detection algorithm factors in the
change in the reflected frequency, which can be quantified by the
Doppler Effect. A calculation of the Doppler frequency shift can be
achieved with Equation (2):
F D = 2 .times. F T .times. ( V R C ) ( 2 ) ##EQU00002##
[0048] In Equation (2), F.sub.D=doppler frequency; F.sub.t=transmit
frequency; V.sub.r=radial velocity; and C=speed of light.
[0049] Further still, the lateral detection algorithm factors in
the polarization of reflections of the electromagnetic pulse 420,
420', 420''. In electromagnetic radiation, the electric field is
perpendicular to the direction of propagation of a wave. The
orientation of this electric field is referred to as the
polarization of the wave. According to embodiments, the
polarization of the wave can be controlled to achieve different
effects. For example, horizontal, vertical, linear, and circular
polarizations can be used to detect different types of reflections.
Linear and random polarization returns are particularly relevant.
Linear polarization, for example, indicates metal surfaces. Hence,
the lateral detection algorithm can be used to interpret linear
polarization returns as casing. In addition, random polarization
indicates a fractal structure, such as rocks or soil. Hence, the
lateral detection algorithm can be used to interpret random
polarization returns as formation rocks. These features of the
lateral detection algorithm allow for the precise detection of the
location and orientation of laterals in a downhole environment and
also allow for the identification of various types of laterals
branching off of various types of motherbores, including for
examples the various lateral and motherbore combinations discussed
with reference to FIGS. 4A-C. In addition, when one or more
antennas are arranged in an array, the lateral detection algorithm
can analyze the differences between the characteristics of signals
received by the different antennas in the array to provide a more
accurate picture of the downhole environment. In certain
embodiments, the traditional transit time principle of radar is not
considered, or is given less weight in the lateral detection
algorithm, due to the relatively short distances traveled by
radiated waves 410, 410', 410'' and reflected waves 420, 420',
420'' in the downhole environment. Instead, comparatively more
weight can be given to frequency modulation, reflected power
levels, and, in the case of a moving lateral detection tool 400,
400', 400'', pulse-Doppler signal processing. The presence of
larger lateral opening may result in a weaker reflection of the
pulse (e.g., due to the absence of the casing, the wall of the
motherbore, or the formation to reflect of the pulse), and
conversely, the absence of a lateral opening may result in a
stronger reflection of the pulse (e.g., due to the presence of the
casing, the wall of the motherbore, or the formation to reflect the
pulse). Thus, in some embodiments, it may be determined that a
lateral is present based on receipt of a relatively weak reflection
of a pulse, and, conversely, it may be determined that a lateral is
not present based on receipt of a relatively strong reflection of a
pulse. Once an accurate location for a lateral 460, 460', 460'' has
been determined, a tool steering mechanism can be used to direct
the lateral detection tool 400, 400', 400' into the detected
lateral 460, 460', 460''. Steering can be an automated process in
which received data is fed back to a tool steering mechanism
control system and the tool is steered responsive to the received
data. In some embodiments, a surface operator manually steers the
subsurface unit.
[0050] FIGS. 5A-B provide an example of another configuration
within the scope of the invention. For example, a surface unit
100'' can be in communication with a subsurface unit 300'' via a
wireline 110''' or coil tubing. As with other embodiments, the
subsurface unit 300'' can include one or more antennas 505, for
example, arranged in an array (e.g., the same or similar to that of
antennas 124, 124', 124''). The one or more antennas 505 can be
disposed within a downhole end of the subsurface unit 300''. Other
components can be disposed within a uphole end of the subsurface
unit 300''. According to embodiments, these other components can
form portions of an application specific integrated circuit (ASIC)
500. One possible configuration of microelectronic components on an
ASIC is illustrated in FIG. 5B. For example, an ASIC 500' can
include a signal generator 516, which, in embodiments, can be
configured to generate a wideband electromagnetic signal (e.g., the
same or similar to that of signal generator 116, 116' described
herein). An ASIC 500' further can include a modulator 518 (e.g.,
the same or similar to that of modulator 118, 118'), a transmitter
520 (e.g., the same or similar to that of transmitter 120, 120'), a
duplexer 522 (e.g., the same or similar to that of duplexer 122,
122'), a receiver 526 (e.g., the same or similar to that of
receiver 122, 122'), a demodulator 528 (e.g., the same or similar
to that of demodulator 128, 128'), a signal processing module 508
(e.g., the same or similar to that of signal processing module 108,
108'), and a communication module 512 (e.g., the same or similar to
that of communication module 112, 112'). A controller 530 (e.g.,
the same or similar to that of controller 114, 114') on the ASIC
500' can be used to control operations of the components on the
ASIC 500'. In embodiments, these microelectronic components can be
included on a chip with memory and processor components as well.
Hence, the components disclosed as situated on an ASIC can be
included on a system-on-a-chip in certain embodiments. According to
embodiments, these microelectronic components can function similar
to their analogues discussed previously. Moreover, these components
can be arranged in the same manner with respect to one another,
though it will be understood by one skilled in the art that other
configurations can be used without departing from the scope of the
invention.
[0051] As noted, various methods are within the scope of the
invention. For example, FIG. 6 depicts steps of a method according
to an embodiment. A method can include generating a wideband
electromagnetic signal 600, modulating the electromagnetic signal
to generate a modulated signal 602, and transmitted the modulated
signal to one or more antennas via a duplexer 604. An example
method of generating a wideband electromagnetic signal 600 is
described herein with regard to at least method 700 of FIG. 7.
According to embodiments, the method further can include converting
the modulated signal into an electromagnetic pulse using the one or
more antennas 606. The electromagnetic pulse can be radiated into a
downhole environment with the one or more antennas 608. When the
electromagnetic pulse strikes objects in the downhole environment,
it can be expected that some of the waves will be scattered and
some will be reflected back to the source. Accordingly, embodiments
can include detecting reflections of the electromagnetic pulse with
the one or more antennas and characterizing these reflections as a
received signal 610. The received signal can be combined from the
one or more antennas and provided to a receiver via the duplexer
612. The method further can include demodulating the received
signal to generate a demodulated signal 614.
[0052] Methods within the scope of the invention can include varied
steps, dependent on whether a reliable high speed data link exists
between a communication module in a subsurface unit and
communication equipment at a remote location, which can include,
for example, a surface unit. Hence, a determination is made whether
such a reliable high speed data link exists 616. If so, in
embodiments, the method can include transmitting the demodulated
signal to the communication module 618 and communicating the
demodulated signal to the remote location for processing 620. The
method further can include processing the demodulated signal at the
remote location to generate a processed signal indicative of
detected laterals 622. For example, processing the demodulated
signal can include using a lateral detection algorithm similar that
that disclosed in this application. Once the demodulated signal has
been processed, the processed signal can be interpreted to display
detected laterals on one or more displays at the remote location
636.
[0053] In certain embodiments, for example, if a reliable high
speed data link does not exist at step 616, embodiments of the
method can include processing the demodulated signal locally, at
the subsurface unit, thereby to generate a processed signal
indicative of detected laterals 624. It will be understood that
such local processing is not strictly dependent on the absence of a
reliable high speed data link, but is only illustrated as such
according to some embodiments. In other embodiments, circumstances
may dictate local processing even when a reliable high speed data
link between a subsurface unit and surface unit exists and is fully
functional. In any event, once the demodulated signal has been
processed locally to generate a processed signal 624, the processed
signal can be transmitted to a communication module 630, and the
communication module may communicate the processed signal to the
remote location 634. . In embodiments, a second check can occur
(e.g., after block 624 and before block 630) to determine whether a
reliable high speed data link exists that can be used to transmit
the processed signal to the communication module. If it is
determined that a reliable high speed data link does exists , the
method can include, then, transmitting the processed signal to a
communication module 630 via the high speed data link, and the
communication module communicating the processed signal to the
remote location 634. If it is determined that a reliable high speed
data link does not exists, the method can include re-checking the
data link repeatedly until such a link is restored or initially
established, and transmitting the processed signal to a
communication module 630 via the high speed data link (once
established) for communication to the remote location 634.
According to embodiments, the processed signal can be stored
indefinitely until such a reliable high speed data link is
established. In certain cases, the subsurface unit can be recovered
to download the processed signal data from the subsurface unit and
manually upload the processed signal data to a surface unit. From
there, the detected laterals can be displayed on one or more
displays at the remote location 636.
[0054] FIG. 7 is a flowchart that illustrates a method 700 for
generating a wideband electromagnetic signal in accordance with an
embodiment. Such a method 700 may be performed at step 600 of the
method described with regard to FIG. 6. Method 700 may include
determining one more characteristics of an environment where an
electromagnetic signal is to be generated to detect a lateral in a
motherbore (block 702), determining one or more signal
characteristics corresponding to the determined characteristics of
the environment (block 704), and generating an electromagnetic
signal having the determined signal characteristics (block
706).
[0055] In some embodiments, determining one more characteristics of
an environment where an electromagnetic signal is to be generated
to detect a lateral in the motherbore (block 702) includes
determining one or more characteristics of the wellbore, casing,
and the formation in a location of the motherbore where an
electromagnetic signal is to be generated to detect a lateral in a
motherbore. This may include, for example, characteristics of an
environment surrounding or expected to surround the subsurface unit
300, 300', 300'' during transmission of the electromagnetic signal
via the antenna 124, 124'. For example, if the subsurface unit 300,
300', 300'' is located at a depth in the motherbore, then
determining one more characteristics of an environment where an
electromagnetic signal is to be generated to detect a lateral in
the motherbore may include determining one or more characteristics
of the wellbore, one or more characteristics of any casing at or
near a depth in the motherbore, and one or more characteristics the
formation at the depth. Relevant characteristics of the wellbore
may include diameter, depth, whether casing is present in the
motherbore, whether casing is present in the lateral that is to be
located, a diameter of the casing, a thickness of the casing,
and/or the like. Relevant characteristics of the formation may
include a reflectivity, resistivity, impedance and/or the like of
the portion of the formation surrounding the motherbore.
[0056] In some embodiments, determining one or more signal
characteristics corresponding to the determined characteristics of
the environment (block 704) includes selecting determining a signal
frequency and a signal transmission power that corresponds to the
determined characteristics of the environment. For example, if a
first environment (e.g., in a first motherbore, or at a first depth
in the first motherbore) has a first set of characteristics (e.g.,
a wellbore diameter of 20 cm, a casing inner diameter of 19 cm, a
casing outer diameter of 20 cm, and the surrounding formation
having reflectivity coefficient value of about 0.2) a first set of
signal characteristics can be determined (e.g., a frequency of
about 1 MHz, and a transmission power of about 1 Watt (W). If a
second environment (e.g., in a second motherbore, or at a second
depth in the first motherbore) has a first set of characteristics
(e.g., a wellbore diameter of 15 cm, a casing inner diameter of 14
cm, a casing outer diameter of 15 cm, and a formation having a
reflectivity coefficient value of about 0.4) a second set of signal
characteristics can be determined (e.g., a frequency of about 100
KHz, and a transmission power of about 2 W. In some embodiments,
the frequency is selected from within an operational range of the
signal source. For example, if the signal generator 116, 116' and
the antenna 124, 124', 124'' have an operational frequency range of
about 1 KHz to about 5 GHz (e.g., the operational frequency ranges
of the signal generator 116, 116' and the antenna 124, 124', 124''
overlap in the range of about 1 KHz to about 5 GHz), then the
frequency may be selected from within that operational range. In
some embodiments, the transmission power is selected from within an
operational range of the signal source. For example, if the signal
generator 116, 116' and the antenna 124, 124', 124'' have an
operational power range of about 1 KHz to about 5 GHz, then the
transmission power may be selected from within that operational
range.
[0057] In some embodiments, generating an electromagnetic signal
having the determined signal characteristics (block 706) includes
generating an electromagnetic signal using the subsurface unit 300,
300', 300'' to generate an electromagnetic signal having the
determined signal characteristics (e.g., the determined frequency
and transmission power). This can be accomplished, for example, in
a manner consistent with that described with regard to at least
blocks 602 to 608 of FIG. 6. Moreover, the reflections creating as
a result of the radiation of a corresponding electromagnetic pulse
may be detected, processed and presented in a manner consistent
with that described with regard to at least blocks 610-636 of FIG.
6.
[0058] In some embodiments, the method 700 can be performed for
various locations of the subsurface unit 300, 300', 300'' so that
the electromagnetic signal can be customized for particular
conditions. For example, a first set of wellbore characteristics
may be determined for a first motherbore, and a corresponding first
set of signal characteristics may be used for generation of
electromagnetic signals/pulses as the subsurface unit 300, 300',
300'' is advanced through the various portions of the motherbore.
That is, for example, the same set of signal characteristics may be
used throughout the motherbore. As a further example, a first set
of signal characteristics may be determined and used for a first
motherbore having a first set of characteristics, and a second set
of signal characteristics may be determined and used for a second
motherbore having a second set of characteristics. That is, for
example, a single subsurface unit 300, 300', 300'' may be
customized to generate different electromagnetic signals/pulses for
different motherbores. This may be enabled at least in part by use
of a wideband signal source (e.g., including the wideband signal
generator 116, 116' and the wideband antenna 124, 124', 124'') that
allow for a single subsurface unit 300, 300', 300'' to generate
electromagnetic signals/pulses with varying characteristics (e.g.,
varying frequency and transmission power). As yet another example,
a first set of signal characteristics may be determined and used
for a first portion of a motherbore (e.g., at a first depth) having
a first set of characteristics, and a second set of signal
characteristics may be determined and used for a second portion of
the motherbore (e.g., at a second depth) having a second set of
characteristics. That is, for example, the subsurface unit 300,
300', 300'' may be customized to generate electromagnetic
signals/pulses for different portions of the same motherbore. In
some embodiments, updated signal characteristics may be determined
periodically. For example, the signal characteristics may be
determined for about every 10 meters the subsurface unit 300, 300',
300'' is advanced in the motherbore. Thus, the subsurface unit 300,
300', 300'' may be customized on the fly, in real-time to take into
account the changing characteristics of the environment as the
subsurface unit 300, 300', 300'' is moved through the motherbore in
search of a lateral.
[0059] In the various embodiments described in this application, a
person having ordinary skill in the art will recognize that various
types of memory are readable by a computer, such as the memory
described in this application in reference to the various
computers, e.g., computer, computer server, web server, or other
computers with embodiments. Examples of computer-readable media can
include but are not limited to: nonvolatile, hard-coded type media,
such as read only memories (ROMs), CD-ROMs, and DVD-ROMs, or
erasable, electrically programmable read only memories (EEPROMs);
recordable type media, such as floppy disks, hard disk drives,
CD-R/RWs, DVD-RAMs, DVD-R/RWs, DVD+R/RWs, flash drives, memory
sticks, and other newer types of memories; and transmission type
media such as digital and analog communication links. For example,
such media can include operating instructions, as well as
instructions related to the systems, apparatuses, computer media,
and the method steps described can operate on a computer. It will
be understood by those skilled in the art that such media can be at
other locations instead of, or in addition to, the locations
described to store computer program products, e.g., including
software thereon. It will be understood by those skilled in the art
that the various software modules or electronic components
described can be implemented and maintained by electronic hardware,
software, or a combination of the two, and that such embodiments
are contemplated by embodiments of the present invention.
[0060] In the drawings and specification, there have been disclosed
embodiments of systems, apparatuses, and methods, and although
specific terms are employed, the terms are used in a descriptive
sense only and not for purposes of limitation. Embodiments have
been described in considerable detail with specific reference to
illustrated embodiments. It will be apparent, however, that various
modifications and changes can be made within the spirit and scope
of the embodiments of the present invention as described in the
foregoing specification, and such modifications and changes are to
be considered equivalents and part of this disclosure. Moreover, it
is noted that various features described with respect to certain
embodiments are to be imputed to other embodiments as well unless
specifically stated otherwise.
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