ELECTROMAGNETICALLY COUPLED BAND-GAP TRANSCEIVERS
Technical Field
[0001] The present disclosure relates generally to devices for use in well
systems. More specifically, but not by way of limitation, this disclosure relates to
electromagnetically coupled band-gap transceivers.
Background
[0002] A well system (e.g., an oil or gas well for extracting fluid or gas from a
subterranean formation) can include various well tools in a wellbore. It can be
desirable to communicate data between the well tools. In some examples, a cable
can be used to transmit data between the well tools. The cable can wear or fail,
however, as the well components rotate and vibrate to perform functions in the
wellbore. In other examples, the well tools can wirelessly transmit data to each
other. The power transmission efficiency of a wireless communication, however, can
depend on a variety of factors that may be impractical or infeasible to control. For
example, the power transmission efficiency of a wireless communication can depend
on the conductive characteristics of the subterranean formation. It can be
challenging to wirelessly communicate between well tools efficiently.
Brief Description of the Drawings
[0003] FIG. 1 depicts a well system that includes a system for using
electromagnetically coupled band-gap transceivers according to one example.
[0004] FIG. 2 depicts another well system that includes a system for using
electromagnetically coupled band-gap transceivers according to one example.
[0005] FIG. 3A is a cross-sectional end view of a transducer for use with a
transceiver or a coupler according to one example.
[0006] FIG. 3B is a cross-sectional side view of the transducer of FIG. 3A for
use with a transceiver or a coupler according to one example.
[0007] FIG. 4 is a cross-sectional side view of a transducer for use with a
transceiver or a coupler according to one example.
[0008] FIG. 5 is a graph depicting power transmission efficiencies using
electromagnetically coupled band-gap transceivers according to one example.
[0009] FIG. 6 is a graph depicting voltages received using an
electromagnetically coupled band-gap transceiver according to one example.
[0010] FIG. 7 is graph depicting voltages associated with electromagnetic
transmissions using electromagnetically coupled band-gap transceivers according to
one example.
[001 1] FIG. 8 is a block diagram of a band-gap transceiver that can
electromagnetically couple according to one example.
[001 2] FIG. 9 is a flow chart showing an example of a process for using
electromagnetically coupled band-gap transceivers according to one example.
Detailed Description
[001 3] Certain aspects and features of the present disclosure are directed to a
communication system that includes electromagnetically coupled band-gap
transceivers operable to transmit data between well tool components (e.g.,
subsystems) in a wellbore. The electromagnetically coupled band-gap transceivers
can include a transceiver with a cylindrically shaped band positioned around (e.g.,
positioned coaxially around) a subsystem of the well tool. The electromagnetically
coupled band-gap transceivers can also include another transceiver with a
cylindrically shaped band positioned around another subsystem of the well tool.
[0014] The transceivers can electromagnetically communicate (e.g., wirelessly
communicate using electromagnetic fields) with each other via the cylindrically
shaped bands. For example, power can be supplied to the cylindrically shaped band
of one transceiver. The power can generate a voltage between the cylindrically
shaped band and the outer housing of the associated subsystem. The voltage can
cause the cylindrically shaped band to emit an electromagnetic field through a fluid in
the wellbore and the surrounding formation (e.g., the subterranean formation). The
voltage can also cause the cylindrically shaped band to transmit current into the fluid
in the wellbore and the surrounding formation. If the fluid and formation have a high
resistivity, the current transmitted into the fluid and formation can attenuate and the
other transceiver can detect the electromagnetic field emitted by the transceiver. If
the fluid and formation have a low resistivity, the electromagnetic field emitted by the
transceiver can attenuate and the other transceiver can detect the current
transmitted through the fluid and the formation. In this manner, the transceivers can
wirelessly communicate (e.g., wirelessly couple) in low resistivity and high resistivity
downhole environments.
[0015] In some examples, the cylindrical shape of the bands can improve the
power transmission efficiency of the communication system. For example, the one
subsystem may rotate at a different speed and in a different direction than another
subsystem. If the transceivers use, for example, asymmetrically-shaped electrodes
positioned on the subsystems, the electrodes can rotate out of alignment with each
other due to the differing speeds and directions of rotation of the subsystems. When
the electrodes are misaligned, electromagnetic communications between the
electrodes may not be effective because the signal received by the misaligned
transceiver may not be detected properly. This can cause unexpected fluctuations in
the strength of the received signals during the rotation of the subsystem, which can
reduce the signal detection efficiency of the communication system. Conversely, the
cylindrically shaped bands cannot rotate out of alignment with one another, because
each of the cylindrically shaped bands traverses the entire circumference of its
associated subsystem. This can allow wireless communications to travel shorter
distances and without interference from the well tool. This can improve the signal
detection efficiency of the communication system and provide for a more stable
communication system.
[0016] In some examples, an intermediate subsystem can be positioned
between the transceivers. Because the intermediate subsystem can be long (e.g.,
40 feet or more), the distance between the transceivers may cause electromagnetic
communications between the transceivers to attenuate. This can affect the power
transmission efficiency of the communication system.
[001 7] To reduce the attenuation due to the distance between the
transceivers, in some examples, two couplers can be positioned on the intermediate
subsystem. Each of the couplers can include a cylindrically shaped band positioned
around the intermediate subsystem. One coupler can be positioned near (e.g.,
within one foot of) a longitudinal end of the intermediate subsystem and proximate to
one of the transceivers. The proximity of the coupler to the transceiver can allow the
transceiver to electromagnetically transmit a signal to the coupler with low signal
attenuation. The coupler can receive the signal and transmit the signal via a
conductor (e.g., a wire) to the other coupler. The other coupler can be positioned
near the opposite longitudinal end of the intermediate subsystem and proximate to
the other transceiver. The proximity of the other coupler to the other transceiver can
allow the other coupler to electromagnetically transmit the signal to the other
transceiver with low signal attenuation. By communicating via the couplers (rather
than one transceiver directly electromagnetically communicating with the other
transceiver), the communication system can have an improved power transmission
efficiency.
[001 8] In one example, the well tool can include a logging-while-drilling tool
and the intermediate subsystem can include a mud motor. One of the transceivers
can electromagnetically (e.g., wirelessly) transmit data to a coupler positioned at one
longitudinal end of the mud motor. For example, the transceiver can
electromagnetically transmit data associated with a drilling shock, a vibration, the
temperature of the drill bit, a rotation speed of a motor, and an inclination angle of
the drill bit to the coupler. The coupler can receive the data and transmit the data via
a conductor to the other coupler positioned at the opposite longitudinal end of the
mud motor. The other coupler can electromagnetically transmit the data to the other
transceiver. In this manner, the transceivers can communicate across the mud
motor via the couplers.
[0019] In some examples, improving the power transmission efficiency can
reduce the power consumed by the communication system. This can increase the
lifespan of the transceivers (which can operate on battery power). Improving the
power transmission efficiency can also improve the signal-to-noise ratio of signals
communicated between the transceivers. This can enhance the quality of the
signals and reduce errors in data associated with (e.g., derived from) the signals.
[0020] These illustrative examples are given to introduce the reader to the
general subject matter discussed here and are not intended to limit the scope of the
disclosed concepts. The following sections describe various additional features and
examples with reference to the drawings in which like numerals indicate like
elements, and directional descriptions are used to describe the illustrative aspects
but, like the illustrative aspects, should not be used to limit the present disclosure.
[0021] FIG. 1 depicts a well system 100 that includes electromagnetically
coupled band-gap transceivers 118a, 118b according to one example. The well
system 100 includes a wellbore 102 extending through various earth strata. The
wellbore 102 extends through a hydrocarbon bearing subterranean formation 104. A
casing string 106 extends from the surface 108 to the subterranean formation 104.
The casing string 106 can provide a conduit through which formation fluids, such as
production fluids produced from the subterranean formation 104, can travel from the
wellbore 102 to the surface 108.
[0022] The well system 100 can also include at least one well tool 114 (e.g., a
formation-testing tool). The well tool 114 can be coupled to a wireline, slickline, or
coiled tube 110 that can be deployed into the wellbore 102, for example, using a
winch 112.
[0023] The well tool 114 can include a transceiver 118a positioned on a
subsystem 116 . The transceiver 118a can include a transducer positioned on the
subsystem 116 . The transducer can include a cylindrically shaped band or one or
more electrodes. For example, the transducer can include multiple electrodes
positioned around the outer circumference of the subsystem 116. As another
example, the transducer can include a cylindrically shaped band positioned coaxially
around the subsystem 116 . The transducer can include any suitable conductive
material (e.g., stainless steel, lead, copper, or titanium).
[0024] The well tool 114 can also include another transceiver 118b positioned
on another subsystem 117. The transceiver 118b can include a transducer
positioned on the subsystem 117 . For example, the transducer can include a
cylindrically shaped band positioned coaxially around the outer circumference of the
subsystem 117 . In some examples, the transceivers 118a, 118b can directly
electromagnetically communicate with each other.
[0025] In some examples, the well tool 114 can also include a coupler 120a
positioned at or near (e.g., within 1 foot of) a longitudinal end 124 of an intermediate
subsystem 119. The well tool 114 can include another coupler 120b positioned at or
near an opposing longitudinal end 126 of the intermediate subsystem 119 . Each of
the couplers 120a, 120b can include a transducer positioned on the intermediate
subsystem 119. For example, each of the couplers 120a, 120b can include
cylindrically shaped bands positioned coaxially around the outer circumference of the
intermediate subsystem 119 . The transducers of the couplers 120a, 120b can
include the same conductive material or a different conductive material from the
transducers of the transceivers 118a, 118b.
[0026] The couplers 120a, 120b can be electrically coupled by a conductor
122. The conductor 122 can include a wire. The wire can be insulated. The
conductor 122 can positioned within a housing of the intermediate subsystem 119.
For example, the wire can be within the inner diameter of, or embedded within the
structure of, the housing of the intermediate subsystem 119. The conductor 122 can
traverse the longitudinal length of the intermediate subsystem 119.
[0027] The transceiver 118a can electromagnetically couple with the coupler
120a. The other transceiver 118b can electromagnetically couple with the other
coupler 120b. This can form a communication path between the transceivers 118a,
118b. For example, the transceiver 118a can electromagnetically transmit data (e.g.,
wirelessly transmit data using electromagnetic fields) to the coupler 120a. The
coupler 120a can receive the data and transmit the data via the conductor 122 to the
other coupler 120b. The other coupler 120b can electromagnetically transmit the
data to the other transceiver 118b. In this manner, the transceiver 118a can transmit
data to the other transceiver 118b via the couplers 120a, 120b. As another example,
the transceiver 118b can electromagnetically transmit data to the coupler 120b. The
coupler 120b can receive the data and transmit the data via the conductor 122 to the
other coupler 120a. The other coupler 120a can electromagnetically transmit the
data to the other transceiver 118a. The transceiver 118a can receive the data and,
for example, communicate the data uphole via wireline. In this manner, the
transceiver 118b can transmit data to the other transceiver 118a via the couplers
120a, 120b.
[0028] In some examples, an object can be positioned between the one or
more of the subsystems 116, 117, 119. The object can be fluid, another well tool, a
component of the well tool 114, a portion of the subterranean formation 104, etc.
The wireless coupling of the transceiver 118a with the coupler 120a, and the other
transceiver 118b with the other coupler 120b, can allow for a communication path
between the transceivers 118a, 118b that may otherwise be blocked by the object.
For example, this communication path may not be possible in traditional wired
communications systems, because the object may block a wire from passing
between the subsystems 116, 117, 119 .
[0029] In some examples, one or more of the subsystems 116, 117, 119 can
rotate with respect to each other. The wireless coupling of the transceiver 118a with
the coupler 120a, and the other transceiver 118b with the other coupler 120b, can
generate a communication path between the transceivers 118a, 118b. This
communication path may not be possible in a traditional wired communications
system, because the rotation of the subsystems 116, 117, 119 may sever the wire or
otherwise prevent the wire from passing between the subsystems 116, 117, 119 .
[0030] FIG. 2 depicts another well system 200 that includes a system for using
electromagnetically coupled band-gap transceivers 118a, 118b according to one
example. In this example, the well system 200 includes a wellbore 102. A well tool
202 (e.g., logging-while-drilling tool) can be positioned in the wellbore 102. The well
tool 202 can include various subsystems 206, 208, 2 10, 212. For example, the well
tool 202 can include a subsystem 206 that can include a communication subsystem.
The well tool 202 can also include a subsystem 2 10 that can include a saver
subsystem or a rotary steerable system. A tubular section or an intermediate
subsystem 208 (e.g., a mud motor or measuring-while-drilling module) can be
positioned between the other subsystems 206, 210. In some examples, the well tool
202 can include a drill bit 214 for drilling the wellbore 102. The drill bit 2 12 can be
coupled to another tubular section or subsystem 212 (e.g., a measuring-while-drilling
module or a rotary steerable system).
[0031] The well tool 202 can also include tubular joints 2 16a, 2 16b. Tubular
joint 2 16a can prevent a wire from passing between a subsystem 206 and the
intermediate subsystem 208. Tubular joint 2 16b can prevent a wire from passing
between a subsystem 2 10 and the intermediate subsystem 208.
[0032] The wellbore 102 can include fluid 220. The fluid 220 can flow in an
annulus 218 positioned between the well tool 202 and a wall of the wellbore 102. In
some examples, the fluid 220 can contact the transceivers 118a, 118b and the
couplers 120a, 120b. This contact can allow for electromagnetic communication, as
described in greater detail with respect to FIG. 3B.
[0033] One transceiver 118a can be coupled to one subsystem 206 and the
other transceiver 118b can be coupled to another subsystem 2 10 . One coupler 120a
can be positioned at or near a longitudinal end of the intermediate subsystem 208
and proximate to a transceiver 118a (e.g., for electromagnetically communicating
with the transceiver 118a). The other coupler 120b can be positioned at or near an
opposing longitudinal end of the intermediate subsystem 208 and proximate to the
other transceiver 118b (e.g., for electromagnetically communicating with the other
transceiver 118b). A conductor 122 can electrically couple the coupler 120a with the
other coupler 120b.
[0034] In some examples, one transceiver 118a can directly
electromagnetically communicate with the other transceiver 118b. In other
examples, the one transceiver 118a can indirectly communicate with the other
transceiver 118b via the couplers 120a, 120b. This can improve the overall power
transmission efficiency of the communication system (e.g., the transceivers 118a,
118b and couplers 120a, 120b). For example, one transceiver 118a can transmit a
wireless signal to an associated coupler 120a. Because the distance between the
transceiver 118a and the coupler 120a can be small (e.g., 1 foot or less), there can
be low attenuation of the wireless signal. The coupler 120a can receive the wireless
signal, convert the wireless signal into an electrical signal, and transmit the electrical
signal via a wire to the other coupler 120b. There may be minimal attenuation of the
electrical signal because the electrical signal is transmitted via the wire. The other
coupler 120b can receive the electrical signal, convert the electrical signal to a
wireless signal, and transmit the wireless signal to the other transceiver 118b.
Because the distance between the other coupler 120b and the other transceiver
118b can be small, there can be low attenuation of the wireless signal. In this
manner, one transceiver 118a can indirectly communicate with the other transceiver
118b via the couplers 120a, 120b to improve the power transmission efficiency of the
communication system.
[0035] FIG. 3A is a cross-sectional end view of a transducer 302 for use with a
transceiver or a coupler according to one example. In this example, the transducer
302 includes a cylindrically shaped band. The transducer 302 can be positioned
around a well tool 300 (e.g., the housing 306 of the well tool 300). In some
examples, an insulator 304 can be positioned between the transducer 302 and the
housing 306 of the well tool 300. This can prevent the transducer 302 from
conducting electricity directly to the well tool 300. The insulator 304 can include any
suitable electrically insulating material (e.g., rubber, PEEK, or plastic).
[0036] The diameter of the transducer 302 can be larger than the diameter of
the housing 306 of the well tool 300. For example, the diameter of the transducer
302 can be 4.75 inches and the diameter of the housing 306 of the well tool 300 can
be 3.2 inches. In some examples, the thickness 3 12 of the transducer 302 can be
thicker or thinner than the thickness 3 10 of the insulator 304, the thickness 3 10 of
the housing 306 of the well tool 300, or both. For example, the transducer 302 can
have a thickness 3 12 of 0.2 inches.
[0037] In some examples, as the length (e.g., length 3 11 depicted in FIG. 3B)
of the transducer 302 increases, the power transmission efficiency can increase.
Space limitations (e.g., due to the configuration of the well tool 300), however, can
limit the length of the transducer 302. In some examples, the length of the
transducer 302 can be the maximum feasible length in view of space limitations. For
example, the length of the transducer 302 can be 6 inches. The length of the
insulator 304 can be the same as or greater than the length of the transducer 302.
[0038] In some examples, each of the transducers 302 in the communication
system can have characteristics (e.g., the length, thickness, and diameter) that are
the same as or different from one another. For example, the transceivers can
include transducers 302 with different diameters from one another. As another
example, the couplers can include transducers 302 with different diameters from one
another.
[0039] FIG. 3B is a cross-sectional side view of the transducer 302 of FIG. 3A
for use with a transceiver or a coupler according to one example. In some
examples, the transceiver can apply electricity to the transducer 302 to transmit an
electromagnetic signal. For example, the transceiver can include an AC signal
source 3 16 . The positive lead of the AC signal source 3 16 can be coupled to the
transducer 302 and the negative lead of the AC signal source 3 16 can be coupled to
the housing 306 of the well tool 300. The AC signal source 3 16 can generate a
voltage 314 between the transducer 302 and the housing 306 of the well tool 300.
[0040] The voltage 314 can cause the transducer 302 to transmit an
electromagnetic field through a fluid in the wellbore and the formation (e.g., the
subterranean formation). The voltage 314 can also cause the cylindrically shaped
band to transmit current into the fluid in the wellbore and the formation. If the fluid
and formation have a high resistivity, the current can attenuate and the
electromagnetic field can propagate through the fluid and formation with a high
power transmission efficiency. This can generate a wireless coupling that is
primarily in the form of an electromagnetic field. If the fluid and formation have a low
resistivity, the electromagnetic field can attenuate and the current can propagate
through the fluid and formation with a high power transmission efficiency. This can
generate a wireless coupling that is primarily in the form of current flowing through
the fluid and formation.
[0041] The combination of the electromagnetic field and current can allow the
transducer 302 to wirelessly communicate (e.g., wirelessly couple) with another
transducer 302 in both low resistivity and high resistivity downhole environments.
Further, the combination of the electromagnetic field and current can allow the
transducer 302 can transfer the voltage 314 between the transducer 302 and the
housing 306 to another transducer 302. This voltage-based wireless coupling can
be different from traditional wireless communications systems, which may use coilbased
induction for wireless communication.
[0042] FIG. 4 is a cross-sectional side view of a transducer 402 for use with a
transceiver or a coupler according to one example. In some examples, the housing
406 of the well tool 400 can include a recessed area 404. The transducer 402 can
be positioned within the recessed area 404. An insulator 403 can be positioned
within the recessed area 404 and between the transducer 402 and the housing 406
of the well tool 400.
[0043] In some examples, a conductor 422 (e.g., a wire, insulated wire, or any
suitable conductive material) can electrically couple the transducer 402 to another
transducer 402. The conductor 422 can be embedded within the housing 406 of the
well tool 400. In some examples, the conductor 422 can be positioned inside of
(e.g., within the inner diameter of) the housing 406 of the well tool 400 or positioned
outside of the housing 406 of the well tool 400.
[0044] FIG. 5 is a graph depicting power transmission efficiencies using
electromagnetically coupled band-gap transceivers according to one example. In
some examples, obstacles in the transmission path of an electromagnetic
communication can affect the power transmission efficiency of the electromagnetic
communication. For example, the conductivity of a fluid (and the conductivity of the
subterranean formation) in the transmission path of a electromagnetic
communication can affect the power transmission efficiency of the electromagnetic
communication. FIG. 5 depicts examples of power transmission efficiencies when
the transmission path has a high resistivity (e.g., 20 ohm-m) and when the
transmission path has a low resistivity (e.g., 1 ohm-m).
[0045] For example, line 502 depicts an example of power transmission
efficiencies using direct electromagnetic communication between transceivers when
the transmission path includes a high resistivity. Line 504 depicts an example of
power transmission efficiencies using direct electromagnetic communication
between transceivers when the transmission path includes a low resistivity. Line 506
depicts an example of power transmission efficiencies using indirect electromagnetic
communication between transceivers (e.g., communication via the couplers) when
the transmission path includes a high resistivity. Line 508 depicts an example of
power transmission efficiencies using indirect electromagnetic communication
between transceivers when the transmission path includes a low resistivity.
[0046] Using the couplers can improve the power transmission efficiency (e.g.,
at frequencies greater than 150 kHz), both when the transmission path has a low
resistivity and when the transmission path has a high resistivity. This can reduce the
power consumed by the transceivers, which can increase the lifespan of the
transceivers (which can operate on battery power). In some examples, improving
the power transmission efficiency can also improve the signal-to-noise ratio of the
transmitted signals. This can enhance the quality of the transmitted signals and
reduce errors in data associated with (e.g., derived from) the transmitted signals.
[0047] FIG. 6 is a graph depicting voltages received using an
electromagnetically coupled band-gap transceiver according to one example. Line
602 depicts voltages of received electromagnetic signals when using direct
electromagnetic communication between transceivers and when the transmission
path includes a high resistivity. Line 604 depicts voltages of received
electromagnetic signals when using direct electromagnetic communication between
transceivers and when the transmission path includes a low resistivity. Line 606
depicts voltages of received electromagnetic signals when using indirect
electromagnetic communication (e.g., communication via the couplers) when the
transmission path includes a high resistivity. Line 608 depicts voltages of received
electromagnetic signals when using indirect electromagnetic communication when
the transmission path includes a low resistivity. Using indirect electromagnetic
communication, the transceivers can receive electromagnetic signals with higher
voltages at higher frequencies (e.g., frequencies greater than 1 MHz) than when
using direct electromagnetic communication. This can occur both when the
transmission path has a low resistivity and when the transmission path has a high
resistivity.
[0048] In some examples, the minimal voltage level to receive a recognizable
electromagnetic communication (e.g., an electromagnetic communication that is not
too noisy) can be -30 dB. As shown in FIG. 6, using indirect electromagnetic
communication, the transmission frequency of a recognizable electromagnetic
communication can be 3 MHz or higher when communicated through a transmission
path with a low resistivity. As shown by line 606 of FIG. 7, using indirect
electromagnetic communication, the transmission frequency of a recognizable
electromagnetic communication can higher than 200 MHz when communicated
through a high resistivity transmission path. In some examples, by being able to
transmit recognizable electromagnetic communications at high frequencies, the
transceivers can communicate more data (e.g., more than 30 bps) in shorter periods
of time.
[0049] FIG. 8 is a block diagram of an example of a band-gap transceiver 118
that can electromagnetically couple according to one example. In some examples,
the components shown in FIG. 8 (e.g., the computing device 802, power source 812,
and transducer 302) can be integrated into a single structure. For example, the
components can be within a single housing. In other examples, the components
shown in FIG. 8 can be distributed (e.g., in separate housings) and in electrical
communication with each other.
[0050] The electromagnetically coupled band-gap transceiver 118 can include
a computing device 802. The computing device 802 can include a processor 804, a
memory 808, and a bus 806. The processor 804 can execute one or more
operations for operating the electromagnetically coupled band-gap transceiver 118.
The processor 804 can execute instructions 8 10 stored in the memory 808 to
perform the operations. The processor 804 can include one processing device or
multiple processing devices. Non-limiting examples of the processor 804 include a
Field-Programmable Gate Array ("FPGA"), an application-specific integrated circuit
("ASIC"), a microprocessor, etc.
[0051] The processor 804 can be communicatively coupled to the memory
808 via the bus 806. The non-volatile memory 808 may include any type of memory
device that retains stored information when powered off. Non-limiting examples of
the memory 808 include electrically erasable and programmable read-only memory
("EEPROM"), flash memory, or any other type of non-volatile memory. In some
examples, at least some of the memory 808 can include a medium from which the
processor 804 can read the instructions 8 10 . A computer-readable medium can
include electronic, optical, magnetic, or other storage devices capable of providing
the processor 804 with computer-readable instructions or other program code. Nonlimiting
examples of a computer-readable medium include (but are not limited to)
magnetic disk(s), memory chip(s), ROM, random-access memory ("RAM"), an ASIC,
a configured processor, optical storage, or any other medium from which a computer
processor can read instructions. The instructions may include processor-specific
instructions generated by a compiler or an interpreter from code written in any
suitable computer-programming language, including, for example, C, C++, C#, etc.
[0052] The electromagnetically coupled band-gap transceiver 118 can include
a power source 8 12. The power source 812 can be in electrical communication with
the computing device 802 and the transducer 302. In some examples, the power
source 812 can include a battery (e.g. for powering the electromagnetically coupled
band-gap transceiver 118). In other examples, the electromagnetically coupled
band-gap transceiver 118 can be coupled to and powered by an electrical cable
(e.g., a wireline).
[0053] Additionally or alternatively, the power source 8 12 can include an AC
signal generator. The computing device 802 can operate the power source 8 12 to
apply a transmission signal to the transducer 302. For example, the computing
device 802 can cause the power source 8 12 to apply a modulated series of voltages
to the transducer 302. The modulated series of voltages can be associated with
data to be transmitted to another transducer 302 (e.g., a transducer 302 associated
with a coupler or another electromagnetically coupled band-gap transceiver 118).
The other transducer 302 can receive the modulated series of voltages and transmit
the data to still another transducer 302. In other examples, the computing device
802, rather than the power source 8 12, can apply the transmission signal to the
transducer 302.
[0054] The electromagnetically coupled band-gap transceiver 118 can include
a transducer 302. As described above, a voltage can be applied to the transducer
302 (e.g., via power source 8 12) to cause the transducer 302 to transmit data to
another transducer 302 (e.g., a transducer 302 associated with a coupler).
[0055] In some examples, the transducer 302 can receive a wireless
transmission. The transducer 302 can communicate data (e.g., voltages) associated
with the wireless transmission to the computing device 802. In some examples, the
computing device 802 can analyze the data and perform one or more functions. For
example, the computing device 802 can generate a response based on the data.
The computing device 802 can cause a response signal associated with the
response to be transmitted to the transducer 302. The transducer 302 can
communicate the response to another electromagnetically coupled band-gap
transceiver 118 . In this manner, the computing device 802 can receive, analyze, and
respond to communications from another electromagnetically coupled band-gap
transceiver 118 .
[0056] FIG. 9 is a flow chart showing an example of a process for using
electromagnetically coupled band-gap transceivers according to one example.
[0057] In block 902, a cylindrically shaped band transmits a wireless signal
(e.g., an electromagnetic signal) to a coupler. The cylindrically shaped band can be
positioned around a subsystem of a well tool. The coupler can be positioned around
(e.g., positioned coaxially around an outer housing of) and at a longitudinal end of an
intermediate subsystem of the well tool. In some examples, the cylindrically shaped
band can emit an electromagnetic field to transmit the wireless signal. In other
examples, the cylindrically shaped band can apply current to a fluid and the
formation to transmit the wireless signal.
[0058] In block 904, the coupler can transmit an electrical signal associated
with the wireless signal to another coupler via a conductor (e.g., a wire). The other
coupler can be positioned around (e.g., positioned coaxially around an outer housing
of) and at another longitudinal end of the intermediate subsystem of the well tool.
The conductor can be inside, outside, or embedded within the intermediate
subsystem (e.g., within the housing of the subsystem).
[0059] In block 906, the other coupler can transmit another wireless signal
(e.g., a wireless signal associated with the electrical signal) to another cylindrically
shaped band. The cylindncally shaped band can be positioned around another
subsystem of the well tool. The cylindncally shaped band can receive the wireless
signal. In some examples, the cylindncally shaped band can transmit the received
wireless signal to a computing device, another well tool subsystem, and/or uphole.
[0060] In some aspects, a system for electromagnetically coupled band-gap
transceivers is provided according to one or more of the following examples:
[0061] Example # 1: A communication system for use in a wellbore can include
a first cylindrically shaped band. The first cylindrically shaped band can be
positioned around a first outer housing of a first subsystem of a well tool. The first
cylindrically shaped band can be operable to electromagnetically couple with a
second cylindrically shaped band via an electromagnetic field and/or by transmitting
a current to the second cylindrically shaped band through a fluid in the wellbore. The
second cylindrically shaped band can be positioned around a second outer housing
of a second subsystem of the well tool.
[0062] Example #2: The communication system of Example # 1 may feature
the first cylindrically shaped band being operable to electromagnetically couple with
the second cylindrically shaped band via the electromagnetic field in response to a
resistivity of the fluid being below a threshold. The first cylindrically shaped band
may be further operable to electromagnetically couple with the second cylindrically
shaped band via the current transmitted through the fluid in response to the
resistivity of the fluid being above the threshold.
[0063] Example #3: The communication system of any of Examples # 1-2 may
feature the second subsystem including a mud motor. The first cylindrically shaped
band and the second cylindrically shaped band can be positioned for
electromagnetically coupling across a tubular joint positioned between the first
subsystem and the mud motor.
[0064] Example #4: The communication system of any of Examples # 1-3 may
feature a mud motor being positioned between the first subsystem and the second
subsystem. The first cylindrically shaped band can be operable to
electromagnetically communicate with the second cylindrically shaped band across
the mud motor.
[0065] Example #5: The communication system of any of Examples # 1-4 may
feature the second cylindrically shaped band being coupled to a longitudinal end of
the second subsystem and to a conductor embedded within the second outer
housing. The conductor can be coupled to a third cylindrically shaped band
positioned around the second outer housing and at an opposing lateral end of the
second subsystem.
[0066] Example #6: The communication system of any of Examples # 1-5 may
feature a third cylindrically shaped band being operable to electromagnetically
couple with a fourth cylindrically shaped band positioned around a third outer
housing of a third subsystem of the well tool.
[0067] Example #7: The communication system of any of Examples # 1-6 may
feature an insulator being positioned between the first cylindrically shaped band and
the first outer housing of the first subsystem.
[0068] Example #8: The communication system of any of Examples # 1-7 may
feature the second outer housing of the second subsystem including a recessed
area. The second cylindrically shaped band can be positioned within the recessed
area.
[0069] Example #9: The communication system of any of Examples # 1-8 may
feature an insulator being positioned within the recessed area and between the
second cylindrically shaped band and the second outer housing.
[0070] Example #10: An assembly may include a well tool. The assembly
may also include a first cylindrically shaped band positioned around an outer housing
and at a longitudinal end of a subsystem of the well tool. The first cylindrically
shaped band operable to electromagnetically couple with a transceiver. The
assembly may further include a second cylindrically shaped band positioned around
the outer housing and at an opposite longitudinal end of the subsystem. The second
cylindrically shaped band can be operable to electromagnetically couple with another
transceiver. The first cylindrically shaped band can be coupled to the second
cylindrically shaped band by a conductor.
[0071] Example # 11: The assembly of Example # 10 may feature the first
cylindrically shaped band being operable to electromagnetically couple with the
transceiver via an electromagnetic field in response to a resistivity of a fluid in a
wellbore being below a threshold. The first cylindrically shaped band may also be
operable to electromagnetically couple with the transceiver via a current transmitted
through the fluid in response to the resistivity of the fluid being above the threshold.
[0072] Example # 12 : The assembly of any of Examples # 10-1 1 may feature
the conductor being embedded within the outer housing.
[0073] Example # 13 : The assembly of any of Examples # 10-12 may feature
the subsystem including a mud motor. The first cylindrically shaped band can be
positioned for electromagnetically coupling across a tubular joint positioned between
the mud motor and another subsystem.
[0074] Example #14: The assembly of any of Examples # 10-13 may feature
an insulator being positioned between the first cylindrically shaped band and the
outer housing.
[0075] Example # 15 : The assembly of any of Examples # 10-14 may feature
the outer housing including a recessed area. The first cylindrically shaped band can
be positioned within the recessed area.
[0076] Example # 16 : The assembly of any of Examples # 10-15 may feature
an insulator being positioned within a recessed area and between the first
cylindrically shaped band and the outer housing.
[0077] Example # 17 : A method can include transmitting an electromagnetic
signal, by a cylindrically shaped band, to a coupler positioned around an outer
housing and at a longitudinal end of a subsystem of a well tool. The method can
also include transmitting, by the coupler, an electrical signal associated with the
electromagnetic signal to another coupler via a wire. The other coupler can be
positioned around the outer housing and at another longitudinal end of the
subsystem. The method can further include transmitting another electromagnetic
signal, by the other coupler, to another cylindrically shaped band positioned around
another subsystem of the well tool.
[0078] Example # 18 : The method of Example # 17 may feature the outer
housing including a recessed area. The coupler can be positioned within the
recessed area.
[0079] Example # 19: The method of any of Examples # 17-1 8 may feature an
insulator being positioned within a recessed area and between the coupler and the
outer housing. The wire can be embedded in the outer housing.
[0080] Example #20: The method of any of Examples #17-1 9 may feature the
subsystem including a mud motor. The cylindrically shaped band and the coupler
can be positioned for electromagnetically coupling across a tubular joint positioned
between the cylindrically shaped band and the coupler.
[0081] The foregoing description of certain examples, including illustrated
examples, has been presented only for the purpose of illustration and description
and is not intended to be exhaustive or to limit the disclosure to the precise forms
disclosed. Numerous modifications, adaptations, and uses thereof will be apparent to
those skilled in the art without departing from the scope of the disclosure.

Claims
What is claimed is:
1. A communication system for use in a wellbore, the communication system
comprising:
a first cylindrically shaped band positioned around a first outer housing of a
first subsystem of a well tool, wherein the first cylindrically shaped band is operable
to electromagnetically couple with a second cylindrically shaped band positioned
around a second outer housing of a second subsystem of the well tool via an
electromagnetic field or by transmitting a current to the second cylindrically shaped
band through a fluid in the wellbore.
2 . The communication system of claim 1, wherein the first cylindrically shaped
band is operable to (i) electromagnetically couple with the second cylindrically
shaped band via the electromagnetic field in response to a resistivity of the fluid
being below a threshold and (ii) electromagnetically couple with the second
cylindrically shaped band via the current transmitted through the fluid in response to
the resistivity of the fluid being above the threshold.
3 . The communication system of claim 1, wherein the second subsystem
comprises a mud motor, and wherein the first cylindrically shaped band and the
second cylindrically shaped band are positioned for electromagnetically coupling
across a tubular joint positioned between the first subsystem and the mud motor.
4 . The communication system of claim 1, wherein a mud motor is positioned
between the first subsystem and the second subsystem, and the first cylindrically
shaped band is operable to electromagnetically communicate with the second
cylindrically shaped band across the mud motor.
5 . The communication system of claim 1, wherein the second cylindrically
shaped band is coupled to a longitudinal end of the second subsystem and to a
conductor embedded within the second outer housing, wherein the conductor is
coupled to a third cylindncally shaped band positioned around the second outer
housing and at an opposing lateral end of the second subsystem.
6 . The communication system of claim 5, wherein the third cylindncally shaped
band is operable to electromagnetically couple with a fourth cylindncally shaped
band positioned around a third outer housing of a third subsystem of the well tool.
7 . The communication system of claim 1, wherein an insulator is positioned
between the first cylindrically shaped band and the first outer housing of the first
subsystem.
8 . The communication system of claim 1, wherein the second outer housing of
the second subsystem comprises a recessed area, and wherein the second
cylindrically shaped band is positioned within the recessed area.
9 . The communication system of claim 8, wherein an insulator is positioned
within the recessed area and between the second cylindrically shaped band and the
second outer housing.
10 . An assembly comprising:
a well tool;
a first cylindrically shaped band positioned around an outer housing and at a
longitudinal end of a subsystem of the well tool, the first cylindrically shaped band
operable to electromagnetically couple with a transceiver; and
a second cylindrically shaped band positioned around the outer housing and
at an opposite longitudinal end of the subsystem, the second cylindrically shaped
band operable to electromagnetically couple with another transceiver, wherein the
first cylindrically shaped band is coupled to the second cylindrically shaped band by
a conductor.
11. The assembly of claim 10, wherein the first cylindrically shaped band is
operable to (i) electromagnetically couple with the transceiver via an electromagnetic
field in response to a resistivity of a fluid in a wellbore being below a threshold and
(ii) electromagnetically couple with the transceiver via a current transmitted through
the fluid in response to the resistivity of the fluid being above the threshold.
12 . The assembly of claim 10, wherein the conductor is embedded within the
outer housing.
13 . The assembly of claim 10, wherein the subsystem comprises a mud motor,
and wherein the first cylindncally shaped band is positioned for electromagnetically
coupling across a tubular joint positioned between the mud motor and another
subsystem.
14. The assembly of claim 10, wherein an insulator is positioned between the first
cylindrically shaped band and the outer housing.
15 . The assembly of claim 10, wherein the outer housing comprises a recessed
area, and wherein the first cylindrically shaped band is positioned within the
recessed area.
16 . The assembly of claim 15, wherein an insulator is positioned within the
recessed area and between the first cylindrically shaped band and the outer housing.
17 . A method comprising:
transmitting an electromagnetic signal, by a cylindrically shaped band, to a
coupler positioned around an outer housing and at a longitudinal end of a subsystem
of a well tool;
transmitting, by the coupler, an electrical signal associated with the
electromagnetic signal to another coupler via a wire, wherein the other coupler is
positioned around the outer housing and at another longitudinal end of the
subsystem; and
transmitting another electromagnetic signal, by the other coupler, to another
cylindrically shaped band positioned around another subsystem of the well tool.
18 . The method of claim 17, wherein the outer housing comprises a recessed
area, and wherein the coupler is positioned within the recessed area.
19 . The method of claim 18, wherein an insulator is positioned within the
recessed area and between the coupler and the outer housing, and wherein the wire
is embedded in the outer housing.
20. The method of claim 17, wherein the subsystem comprises a mud motor, and
wherein the cylindrically shaped band and the coupler are positioned for
electromagnetically coupling across a tubular joint positioned between the
cylindrically shaped band and the coupler.