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
band-gap communications across a well tool with a modified exterior.
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 band-gap transceivers for
band-gap communications across a well tool with a modified exterior according to
one example.
[0004] FIG. 2A is a cross-sectional end view of a transducer for use with a
transceiver according to one example.
[0005] FIG. 2B is a cross-sectional side view of the transducer of FIG. 2A for
use with a transceiver according to one example.
[0006] FIG. 3 is a cross-sectional side view of a transducer for use with a
transceiver according to one example.
[0007] FIG. 4 depicts another well system that includes band-gap transceivers
for band-gap communications across a well tool with a modified exterior according to
one example.
[0008] FIG. 5 is a cross-sectional view of a well tool with a modified exterior
according to one example.
[0009] FIG. 6 is a graph depicting power transmission efficiencies of band-gap
communications across a well tool with a modified exterior according to one
example.
[001 0] FIG. 7 is a graph depicting voltages of band-gap communications
across a well tool with a modified exterior according to one example.
[001 1] FIG. 8 is a cross-sectional view of a well tool with a modified exterior
according to one example.
[001 2] FIG. 9 is a cross-sectional view of a well tool with a modified exterior
according to one example.
[001 3] FIG. 10 is a graph depicting power transmission efficiencies of bandgap
communications across a well tool with a modified exterior according to one
example.
[0014] FIG. 11 is a graph depicting power transmission efficiencies of bandgap
communications across a well tool with a modified exterior at high frequencies
according to one example.
[001 5] FIG. 12 is a graph depicting voltages of band-gap communications
across a well tool with a modified exterior according to one example.
[001 6] FIG. 13 is a graph depicting voltages of band-gap communications
across a well tool with a modified exterior at high frequencies according to one
example.
[001 7] FIG. 14 is a block diagram of a transceiver that can communicate
across a well tool with a modified exterior.
[001 8] FIG. 15 is a flow chart showing an example of a process for producing
a well tool with a modified exterior according to one example.
Detailed Description
[001 9] Certain aspects and features of the present disclosure are directed to
band-gap communications across a well tool with a modified exterior. The band-gap
communications can be between two transceivers. One transceiver can be include a
cylindrically shaped band positioned around (e.g., positioned coaxially around) a
subsystem of the well tool. The other transceiver can include a cylindrically shaped
band positioned around another subsystem of the well tool.
[0020] 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 radiate 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.
The transceivers can wirelessly communicate (e.g., wirelessly couple) in low
resistivity and high resistivity downhole environments.
[0021] 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.
[0022] In some examples, an intermediate subsystem (e.g., a mud motor) 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. Further, as
the electromagnetic field and/or current passes through the fluid and formation, the
electromagnetic field and/or current can electrically interact with the housing of the
intermediate subsystem. For example, a portion of the current can electrically short
to through the housing of the intermediate subsystem, reducing the amount of
current that reaches the receiving transceiver. This may cause the electromagnetic
field and/or current to attenuate, reducing the power transmission efficiency of the
communication system.
[0023] To reduce the attenuation due to the distance between the
transceivers, in some examples, the exterior of the intermediate subsystem can be
modified. For example, the exterior can include an insulator layer positioned around
(e.g., positioned coaxially around) the outer housing of the intermediate subsystem
and traversing the entire longitudinal length of the intermediate subsystem. This can
prevent the current from electrically shorting through the outer housing of the
intermediate subsystem. A metal sleeve can be positioned around the insulator
layer (e.g., to protect the insulator layer from damage). In some examples, the
insulator layer can include multiple insulative rings (e.g., O rings) positioned between
the outer housing of the intermediate subsystem and the metal sleeve. The
insulative rings can create a space between the intermediate subsystem and the
metal sleeve. This can electrically insulate the metal sleeve from the outer housing
of the intermediate subsystem. The metal sleeve can act as an electrical shield,
preventing current from electrically interacting with the outer housing of the
intermediate subsystem. In some examples, insulative buffers can be positioned
around the outer housing of the intermediate subsystem and adjacent to each
longitudinal end of the metal sleeve. This can help prevent the metal sleeve from
contacting metal components (e.g., a tubular joint) adjacent to the metal sleeve and
the intermediate subsystem, thereby maintaining the metal sleeve's electrical
isolation.
[0024] In one example, the well tool can include a logging-while-drilling tool
and the intermediate subsystem can include a mud motor. The mud motor can
include a modified exterior that includes an insulator positioned around an outer
housing of the mud motor. A metal sleeve can be positioned around the insulator.
To transmit an electromagnetic communication, one transceiver can apply a voltage
to its cylindrically shaped band. This can generate electromagnetic waves and an
electric current associated with the wireless communication that can propagate
through the wellbore. The modified exterior of the mud motor can reduce the
attenuation of the electromagnetic waves and current due to electrical interactions
with the outer housing of the mud motor. With less attenuation, more energy
associated with each communication can be received by the other transceiver. In
this manner, the transceivers can communicate across the mud motor with an
improved power transmission efficiency.
[0025] In some examples, improving the power transmission efficiency can
reduce the power consumed by the transceivers. 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.
[0026] 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.
[0027] FIG. 1 depicts a well system 100 that includes band-gap transceivers
118a, 118b for band-gap communications across a well tool 114 with a modified
exterior 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.
[0028] 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.
[0029] The well tool 114 can include a transceiver 118a positioned on a
subsystem 116 of the well tool 114. 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).
[0030] 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 .
[0031] The well tool 114 can also include an intermediate subsystem 119 . In
some examples, the intermediate subsystem 119 can include a mud motor. The
transceivers 118a, 118b can electromagnetically communicate (e.g., wirelessly
communicate using electromagnetic fields) across the intermediate subsystem 119.
[0032] In some examples, an object can be positioned between one
subsystem 116 and the intermediate subsystem 119 and/or between another
subsystem 117 and the intermediate subsystem 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 transceivers 118a, 118b 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.
[0033] In some examples, one or more of the subsystems 116, 117, 119 can
rotate with respect to each other. The wireless coupling of the transceivers 118a,
118b 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 .
[0034] FIG. 2A is a cross-sectional end view of a transducer 202 for use with a
transceiver according to one example. In this example, the transducer 202 includes
a cylindrically shaped band. The transducer 202 can be positioned around a well
tool 200 (e.g., the housing 206 of the well tool 200). In some examples, an insulator
204 can be positioned between the transducer 202 and the housing 206 of the well
tool 200. This can prevent the transducer 202 from conducting electricity directly to
the well tool 200. The insulator 204 can include any suitable electrically insulating
material (e.g., rubber, PEEK, plastic, or a dielectric material).
[0035] The diameter of the transducer 202 can be larger than the diameter of
the housing 206 of the well tool 200. For example, the diameter of the transducer
202 can be 4.75 inches and the diameter of the housing 206 of the well tool 200 can
be 3.2 inches. In some examples, the thickness 2 12 of the transducer 202 can be
thicker or thinner than the thickness 208 of the insulator 204, the thickness 2 10 of
the housing 206 of the well tool 200, or both. For example, the transducer 202 can
have a thickness of 0.2 inches.
[0036] In some examples, as the length (e.g., length 2 11 depicted in FIG. 2B)
of the transducer 202 increases, the power transmission efficiency can increase.
Space limitations (e.g., due to the configuration of the well tool 200), however, can
limit the length of the transducer 202. In some examples, the length of the
transducer 202 can be the maximum feasible length in view of space limitations. For
example, the length of the transducer 202 can be 15.240 cm. This may allow the
transducer 202 to fit between components of the well tool 200. The length of the
insulator 204 can be the same as or greater than the length of the transducer 202.
[0037] In some examples, each of the transducers 118 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 118 with different diameters from one another.
[0038] FIG. 2B is a cross-sectional side view of the transducer 202 of FIG. 2A
for use with a transceiver according to one example. In some examples, the
transceiver can apply electricity to the transducer 202 to transmit a wireless signal.
For example, the transceiver can include an AC signal source 2 16 . The positive lead
of the AC signal source 2 16 can be coupled to the transducer 202 and the negative
lead of the AC signal source 2 16 can be coupled to the housing 206 of the well tool
200. The AC signal source 2 16 can generate a voltage 214 between the transducer
202 and the housing 206 of the well tool 200.
[0039] The voltage 214 can cause the transducer 202 to radiate an
electromagnetic field through a fluid in the wellbore and the formation (e.g., the
subterranean formation). The voltage 214 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 the 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 the 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 the formation.
[0040] The combination of the electromagnetic field and current can allow the
transducer 202 to wirelessly communicate (e.g., wirelessly couple) with another
transducer 202 in both low resistivity and high resistivity downhole environments.
Further, the combination of the electromagnetic field and current can allow the
transducer 202 can transfer the voltage 2 11 between the transducer 202 and the
housing 206 to another transducer 202. This voltage-based wireless coupling can
be different from traditional wireless communications systems, which may use coilbased
induction for wireless communication.
[0041] FIG. 3 is a cross-sectional side view of a transducer 302 for use with a
transceiver according to one example. In some examples, the housing 306 of the
well tool 300 can include a recessed area 304. The transducer 302 can be
positioned within the recessed area 304. An insulator 303 can be positioned within
the recessed area 304 and between the transducer 302 and the housing 306 of the
well tool 300. In some examples, the transducer 302 can operate similarly to the
transducer 302 described with respect to FIG. 2 .
[0042] In some examples, positioning the transducer 302 within the recessed
area 304 allows the well tool 300 and transducer 302 to take up less total space in
the well system. Further, positioning the transducer 302 within the recessed area
304 can protect the transducer 302 from damage. For example, less of the
transducer 302 can be exposed to downhole fluid, temperatures, and impact with
other well system components.
[0043] FIG. 4 depicts another well system 400 that includes band-gap
transceivers 118a, 118b for band-gap communications across a well tool 402 with a
modified exterior according to one example. In this example, the well system 400
includes a wellbore 401 . A well tool 402 (e.g., logging-while-drilling tool) can be
positioned in the wellbore 401 . The well tool 402 can include various subsystems
406, 408, 4 10, 412. For example, the well tool 402 can include a subsystem 406
that includes a communication subsystem. The well tool 402 can also include a
subsystem 4 10 that includes a saver subsystem or a rotary steerable system. A
tubular section or an intermediate subsystem 408 (e.g., a mud motor or measuringwhile-
drilling module) can be positioned between the other subsystems 406, 4 10 . In
some examples, the well tool 402 can include a drill bit 414 for drilling the wellbore
401 . The drill bit 4 12 can be coupled to another tubular section or intermediate
subsystem 412 (e.g., a measuring-while-drilling module or a rotary steerable
system).
[0044] The well tool 402 can also include tubular joints 4 16a, 4 16b. Tubular
joint 4 16a can prevent a wire from passing between one subsystem 406 and the
intermediate subsystem 408. Tubular joint 4 16b can prevent a wire from passing
between the other subsystem 410 and the intermediate subsystem 408.
[0045] The wellbore 401 can include fluid 420. The fluid 420 (e.g., mud) can
flow in an annulus 4 18 positioned between the well tool 402 and a wall of the
wellbore 401 . In some examples, the fluid 420 can contact the transceivers 118a,
118b. This contact can allow for wireless communication between the transceivers
118a, 118b.
[0046] In some examples, one transceiver 118a can apply a voltage to an
associated transducer to transmit an electromagnetic communication. This can
cause the transducer to radiate an electromagnetic field through a fluid in the
wellbore 401 and the formation. The voltage can also cause the cylindrically shaped
band to transmit current 422 into the fluid in the wellbore and the formation. In some
examples, as the electromagnetic field and/or current 422 passes through the fluid
and the formation, the electromagnetic field and/or current 422 can electrically
interact with the housing 424 of the tubular section or intermediate subsystem 408.
For example, a portion of the current 422 can electrically short to through the
housing 424 of the intermediate subsystem 408. This may cause the
electromagnetic field and/or current 422 to attenuate, reducing the power
transmission efficiency of the communication system.
[0047] In some examples, the housing 424 of the tubular section or
intermediate subsystem 408 can be modified to include an insulator. This can
prevent the electromagnetic field and/or current 422 from electrically interacting with
the housing 424, which can increase the power transmission efficiency of the
transceivers 118a, 118b. Examples of modifications to the tubular section or
intermediate subsystem 408 are described below.
[0048] FIG. 5 is a cross-sectional view of an example of a well tool 500 with a
modified exterior according to one example. The well tool 500 can be positioned in a
wellbore 501 . The well tool 500 can include a subsystem 506, another subsystem
508, and a tubular joint 5 10 positioned between the subsystems 506, 508 (e.g.
similar to the example configuration of Fig. 3).
[0049] Fluid 520 can flow through the wellbore 501 . The fluid 520 can contact
a transducer 502 coupled to a subsystem 506. The transducer 502 can be coaxially
positioned around the outer housing 524 of the well tool 500. In some examples, the
transducer 502 can be positioned within a recessed area in the outer housing 524 of
the well tool 500.
[0050] In some examples, the well tool 500 can be completely or partially
insulated for reducing attenuation of current and/or electromagnetic waves output by
a transducer 502. For example, an insulator 503 can be positioned around an inner
mandrel 504 of the well tool 500. The inner mandrel 504 can include a metal
material. The insulator 503 can include an insulator sleeve positioned coaxially
around the inner mandrel 504 of the well tool 500. The insulator 503 can include any
suitable electrically insulating material (e.g., rubber, PEEK, plastic, or a dielectric
material). In some examples, the insulator 503 can include an insulating paint,
coating, or sleeve. The insulator 503 can traverse the longitudinal length of the well
tool 402. For example, the insulator 503 can traverse the longitudinal length of one
subsystem 506, another subsystem 508, and the tubular joint 5 10 between the
subsystems 506, 508.
[0051] In some examples, an outer housing 524 (e.g., a metal sleeve) can be
positioned around the insulator 503. Because the insulator 503 may be unable to
endure the hostile environment downhole, the outer housing 524 can protect the
insulator 503 (e.g., against chemical and mechanical abrasion). The insulator 503 in
combination with the outer housing 524 can form the modified exterior of the well tool
500.
[0052] The insulator 503 can electrically insulate the outer housing 524 of the
well tool 500 from the inner mandrel 504 of the well tool 500. This can prevent
current and/or electromagnetic waves from the transducer 502 from electrically
interacting with the inner mandrel 504, causing attenuation. Examples of power
transmission efficiency and voltage gains due to modifying the exterior of the well
tool 500 are described in FIGs. 6-7.
[0053] In some examples, the transducer 502 can generate transverse
electromagnetic waves (TEM waves). A TEM wave can be an electromagnetic wave
in which the electric field or the magnetic field is transverse to the direction of the
transmission of the wave. By positioning (e.g., sandwiching) the insulator 503
between the outer housing 524 and the inner mandrel 504, the outer housing 524
and the inner mandrel 504 can act as a waveguide. The TEM waves can reflect
(e.g., bounce) off the outer housing 524 and the inner mandrel 504 to propagate
towards a receiving transducer. In this manner, TEM waves can additionally or
alternatively be used to wirelessly communicate between transceivers.
[0054] FIG. 6 is a graph depicting power transmission efficiencies of band-gap
communications across a well tool with a modified exterior 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 an
electromagnetic communication can affect the power transmission efficiency of the
electromagnetic communication. FIG. 6 depicts examples of power transmission
efficiencies when the transmission path (e.g., the mud and the subterranean
formation) has a high resistivity (e.g., 20 ohm-m) and when the transmission path
has a low resistivity (e.g., 1 ohm-m).
[0055] As shown in FIG. 6, the power transmission efficiency is roughly -5 dB
when the well tool has a fully insulated exterior (e.g., as shown in FIG. 5), both when
communicating through a high resistivity transmission path and when communicating
through a low resistivity transmission path. This can be 30 dB higher than the power
transmission efficiency when the well tool has an exposed exterior (e.g., when the
well tool does not have the insulation layer) and the electromagnetic communications
are transmitted at low frequencies (e.g., 5 kHz). This can also be 180 dB higher than
the power transmission efficiency when the well tool has an exposed exterior and the
electromagnetic communications are transmitted at high frequencies (e.g., 1 MHz).
[0056] FIG. 7 is a graph depicting voltages of band-gap communications
across a well tool with a fully insulated exterior according to one example. As shown
in FIG. 7, the voltage of an electromagnetic communication received by a transceiver
is between 5 and 8 dB when the well tool has a fully insulated exterior, both when
communicating through a high resistivity transmission path and when communicating
through a low resistivity transmission path. This can be 15 dB higher than the
voltage of an electromagnetic communication received by a transceiver when the
well tool has an exposed exterior (e.g., when the well tool does not have the
insulation layer) and the electromagnetic communications are transmitted at low
frequencies (e.g., 1 kHz). This can also be 95 dB higher than the voltage of an
electromagnetic communication received by a transceiver when the well tool has an
exposed exterior and the electromagnetic communications are transmitted at high
frequencies (e.g., 1 MHz).
[0057] 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. 7, with a fully insulated exterior, the
transmission frequency of a recognizable electromagnetic communication can be 10
MHz or higher. 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.
[0058] FIG. 8 is a cross-sectional view of a well tool 800 with a modified
exterior according to one example. The well tool 800 can include a subsystem 808.
The subsystem 808 can be coupled to a tubular joint 8 10.
[0059] In some examples, the well tool 800 can include an inner mandrel 802.
The inner mandrel 802 can include a metal material. An insulator 804 can be
positioned around the inner mandrel. The insulator 804 can include any suitable
electrically insulating material (e.g., rubber, PEEK, plastic, or a dielectric material).
[0060] An outer housing 8 12 (e.g., a metal sleeve) can be positioned around
the insulator 804 and between insulative buffers 806a, 806b. The insulative buffers
806a, 806b (e.g., O rings) can be positioned around (e.g., positioned coaxially
around) the inner mandrel 802 and near the longitudinal ends of the inner mandrel
802. For example, the insulative buffers 806a, 806b can be positioned adjacent to
either end of the outer housing 8 12 . The insulative buffers 806a, 806b can include
any suitable electrically insulating material (e.g., rubber, PEEK, plastic, or a dielectric
material). The insulative buffers 806a, 806b may or may not include the same
insulating material as the insulator 804. The insulative buffers 806a, 806b and the
insulator 804 can electrically isolate the outer housing 8 12 from the inner mandrel
802 and the tubular joint 8 10 . The outer housing 8 12 can prevent current and/or
electromagnetic waves from electrically interacting with the inner mandrel 802,
causing attenuation.
[0061] FIG. 9 is a cross-sectional view of a well tool 900 with a modified
exterior according to one example. The well tool 900 can include a subsystem 808.
The subsystem 808 can be coupled to a tubular joint 8 10 . The well tool 800 can
include an inner mandrel 802. Insulative buffers 806a, 806b (e.g., O rings) can be
positioned around (e.g., positioned coaxially around) the inner mandrel 802. The
insulative buffers 806a, 806b can be positioned adjacent to the outer housing 8 12.
At least one insulative buffer 806a can also be positioned adjacent to the tubular joint
8 10.
[0062] The well tool 900 can also include multiple interior insulative buffers
906a-e. The interior insulative buffers 906a-e (e.g., O rings) can be positioned
around (e.g., positioned coaxially around) the inner mandrel 802. In some examples,
the interior insulative buffers 906a-e can be evenly spaced along the longitude of the
inner mandrel 802. The interior insulative buffers 906a-e can include any suitable
electrically insulating material (e.g., rubber, PEEK, plastic, or a dielectric material).
The interior insulative buffers 906a-e can create a space 902 between the inner
mandrel 802 and an outer housing 8 12 positioned around the interior insulative
buffers 906a-e. The space 902 can electrically insulate the outer housing 812 from
the inner mandrel 802. This can prevent current and/or electromagnetic waves from
electrically interacting with the inner mandrel 802, causing attenuation.
[0063] In some examples, the outer housing 8 12 can include grooves 904
(e.g., slots). The grooves 904 can receive the interior insulative buffers 906a-e. The
grooves 904 can help position the support the interior insulative buffers 906a-e.
[0064] FIG. 10 is a graph depicting power transmission efficiencies of bandgap
communications across a well tool with a modified exterior according to one
example. Line 1002 depicts an example of power transmission efficiencies when the
well tool has an exposed (e.g., uninsulated) outer housing and when the
transmission path includes a high resistivity. Line 1004 depicts an example of power
transmission efficiencies when the well tool has an exposed outer housing and when
the transmission path includes a low resistivity. Line 1006 depicts an example of
power transmission efficiencies when the well tool has a partially insulated outer
housing (e.g., as shown in FIGs. 8-9) and when the transmission path includes a
high resistivity. Line 1008 depicts an example of power transmission efficiencies
when the well tool has a partially insulated outer housing and when the transmission
path includes a low resistivity.
[0065] The power transmission efficiency can be between -32 dB and - 18 dB
when the well tool has a partially insulated outer housing and when electromagnetic
communications are transmitted using frequencies up to 1 MHz. Conversely, the
power transmission efficiency can be between - 180 dB and -60 dB when well tool
has an exposed outer housing and when electromagnetic communications are
transmitted using frequencies up to 1 MHz. Further, as shown in FIG. 11, the power
transmission efficiency can be between -95 dB and -50 dB when the well tool has a
partially insulated outer housing and when electromagnetic communications are
transmitted using frequencies up to 100 MHz.
[0066] FIG. 12 is a graph depicting voltages of band-gap communications
across a well tool with a modified exterior according to one example. Line 1202
depicts voltages of received electromagnetic signals when using a well tool with an
exposed outer housing and when the transmission path includes a high resistivity.
Line 1204 depicts voltages of received electromagnetic signals when using a well
tool with an exposed outer housing and when the transmission path includes a low
resistivity. Line 1206 depicts voltages of received electromagnetic signals when
using a partially insulated outer housing and when the transmission path includes a
high resistivity. Line 1208 depicts voltages of received electromagnetic signals when
using a partially insulated outer housing and when the transmission path includes a
low resistivity. When the well tool includes a partially insulated outer housing, the
transceivers can receive electromagnetic signals with higher voltages at higher
frequencies (e.g., frequencies greater than 1 MHz) than when the well tool includes
an exposed outer housing. This can occur both when the transmission path has a
low resistivity and when the transmission path has a high resistivity.
[0067] In some examples, the minimal voltage level to receive a recognizable
electromagnetic communication (e.g., a wireless communication that is not too noisy)
can be -30 dB. As shown in FIG. 12, using a well tool with a partially insulated outer
housing, the transmission frequency of a recognizable electromagnetic
communication can be higher than 10 MHz when communicated through a
transmission path with either a low resistivity or a high resistivity. As shown in FIG.
13, using a well tool with a partially insulated outer housing, the transmission
frequency of a recognizable electromagnetic communication can be higher than 200
MHz when communicated through a high resistivity transmission path. The
transmission frequency of a recognizable electromagnetic communication can be
higher than 15 MHz when communicated through a low 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.
[0068] FIG. 14 is a block diagram of a transceiver that can transmit
communicate across a well tool with a modified exterior. In some examples, the
components shown in FIG. 14 (e.g., the computing device 1402, power source 141 2,
and transducer 202) 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. 14 can be distributed (e.g., in separate housings) and in electrical
communication with each other.
[0069] The transceiver 118 can include a computing device 1402. The
computing device 1402 can include a processor 1404, a memory 1408, and a bus
1406. The processor 1404 can execute one or more operations for operating a
transceiver. The processor 1404 can execute instructions 141 0 stored in the
memory 1408 to perform the operations. The processor 1404 can include one
processing device or multiple processing devices. Non-limiting examples of the
processor 1404 include a Field-Programmable Gate Array ("FPGA"), an applicationspecific
integrated circuit ("ASIC"), a microprocessor, etc.
[0070] The processor 1404 can be communicatively coupled to the memory
1408 via the bus 1406. The non-volatile memory 1408 may include any type of
memory device that retains stored information when powered off. Non-limiting
examples of the memory 1408 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 1408 can include a medium from
which the processor 1404 can read the instructions 141 0 . A computer-readable
medium can include electronic, optical, magnetic, or other storage devices capable
of providing the processor 1404 with computer-readable instructions or other
program code. Non-limiting 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.
[0071] The transceiver 118 can include a power source 1412. The power
source 141 2 can be in electrical communication with the computing device 1402 and
the transducer 202. In some examples, the power source 1412 can include a battery
(e.g. for powering the transceiver 118). In other examples, the transceiver 118 can
be coupled to and powered by an electrical cable (e.g., a wireline).
[0072] Additionally or alternatively, the power source 141 2 can include an AC
signal generator. The computing device 1402 can operate the power source 1412 to
apply a transmission signal to the transducer 202. For example, the computing
device 1402 can cause the power source 1412 to apply a modulated series of
voltages to the transducer 202. The modulated series of voltages can be associated
with data to be transmitted to another transceiver 118 . The transducer 202 can
receive the modulated series of voltages and transmit the data to the other
transducer 202. In other examples, the computing device 1402, rather than the
power source 1412, can apply the transmission signal to the transducer 202.
[0073] The transceiver 118 can include a transducer 202. As described
above, a voltage can be applied to the transducer 202 (e.g., via power source 141 2)
to cause the transducer 202 to transmit data to another transducer 202 (e.g., a
transducer 202 associated with another transceiver).
[0074] In some examples, the transducer 202 can receive an electromagnetic
transmission. The transducer 202 can communicate data (e.g., voltages) associated
with the electromagnetic transmission to the computing device 1402. In some
examples, the computing device 1402 can analyze the data and perform one or
more functions. For example, the computing device 1402 can generate a response
based on the data. The computing device 1402 can cause a response signal
associated with the response to be transmitted to the transducer 202. The
transducer 202 can communicate the response to another transceiver 118. In this
manner, the computing device 1402 can receive, analyze, and respond to
communications from another transceiver 118 .
[0075] FIG. 15 is a flow chart showing an example of a process for producing
a well tool with a modified exterior according to one example.
[0076] In block 1502, a cylindncally shaped band transmits a wireless signal
(e.g., an electromagnetic signal) to another cylindncally shaped band. One
cylindrically shaped band can be associated with one subsystem and the other
cylindrically shaped band can be associated with the other subsystem. The
subsystems can be well tool subsystems. In some examples, the cylindrically
shaped band can radiate an electromagnetic field to transmit the wireless signal. In
other examples, the cylindrically shaped band can apply current to a fluid (e.g., in a
wellbore and between the cylindrically shaped bands) and the formation to transmit
the wireless signal.
[0077] In block 1504, a portion of an inner mandrel can be insulated from
electrically interacting with the wireless signal. In some examples, insulating can
include completely eliminating the electrical interaction of the wireless signal with the
inner mandrel. In other examples, insulating can include substantially reducing but
not completely eliminating the electrical interaction of the wireless signal with the
inner mandrel.
[0078] The portion of the inner mandrel can be insulated from electrically
interacting with the wireless signal via an insulator positioned around a portion of the
inner mandrel. The inner mandrel can be associated with an intermediate
subsystem (e.g., a mud motor) that can be positioned between the other
subsystems. A cylindrically shaped band can transmit the wireless signal across the
intermediate subsystem with reduced attenuation due to the insulator.
[0079] In some aspects, band-gap communications across a well tool with a
modified exterior is provided according to one or more of the following examples:
[0080] Example # 1: A communication system can include a first subsystem of
a well tool. The first subsystem can include a first cylindrically shaped band
positioned around the first subsystem and operable to electromagnetically couple
with a second cylindrically shaped band. The communication system can also
include a second subsystem of the well tool. The second subsystem can include the
second cylindrically shaped band being positioned around the second subsystem.
The communication system can also include an intermediate subsystem positioned
between the first subsystem and the second subsystem. The intermediate
subsystem can include an insulator positioned coaxially around the intermediate
subsystem.
[0081] Example #2: The communication system of Example # 1 may feature
the intermediate subsystem including a mud motor and a tubular joint being
positioned between the first subsystem and the intermediate subsystem.
[0082] Example #3: The communication system of any of Examples # 1-2 may
feature a metal sleeve being positioned coaxially around the insulator.
[0083] Example #4: The communication system of Example #3 may feature
the insulator being included in multiple insulators positioned between an inner
mandrel of the intermediate subsystem and the metal sleeve.
[0084] Example #5: The communication system of Example #4 may feature
the metal sleeve including multiple grooves for receiving the multiple insulators. The
multiple insulators can be operable to create a space between the inner mandrel and
the metal sleeve.
[0085] Example #6: The communication system of any of Examples #3-5 may
feature two insulative buffers being positioned around an inner mandrel and at
opposite longitudinal ends of the metal sleeve from one another.
[0086] Example #7: The communication system of Example #6 may feature
one of the two insulative buffers being positioned adjacent to a tubular joint.
[0087] Example #8: The communication system of any of Examples # 1-3 may
feature two insulative buffers being positioned around an inner mandrel of the
intermediate subsystem and at opposite longitudinal ends of the metal sleeve from
one another. The insulator can extend along a full longitudinal length of the inner
mandrel between the two insulative buffers. One of the two insulative buffers can be
positioned adjacent to a tubular joint.
[0088] Example #9: The communication system of any of Examples # 1-8 may
feature the insulator being operable to electrically insulate a metal sleeve from the
intermediate subsystem.
[0089] Example # 10 : The communication system of any of Examples # 1-9
may feature the insulator being operable to separate a metal sleeve from an inner
mandrel of the intermediate subsystem.
[0090] Example # 11: An assembly can include an inner mandrel positioned
within an intermediate subsystem of a well tool. The assembly can also include an
insulator positioned coaxially around the inner mandrel. The assembly can further
include a metal sleeve positioned coaxially around the insulator and making up an
outer housing of the intermediate subsystem. The assembly can also include two
insulative buffers positioned coaxially around the inner mandrel and at opposite
longitudinal ends of the metal sleeve from one another.
[0091] Example # 12 : The assembly of Example # 11 may feature the
intermediate subsystem including a mud motor and one of the two insulative buffers
being positioned adjacent to a tubular joint.
[0092] Example # 13 : The assembly of any of Examples # 11-12 may feature
the insulator being included in multiple insulators positioned between the inner
mandrel and the metal sleeve.
[0093] Example #14: The assembly of any of Examples # 11-13 may feature
the metal sleeve including multiple grooves for receiving multiple insulators. The
multiple insulators can be operable to create a space between the inner mandrel and
the metal sleeve.
[0094] Example # 15 : The assembly of any of Examples # 11-14 may feature
the insulator being operable to electrically insulate the metal sleeve from the
intermediate subsystem.
[0095] Example # 16 : The assembly of any of Examples # 11-15 may feature
the insulator being operable to separate the metal sleeve from the inner mandrel.
[0096] Example # 17 : The assembly of any of Examples # 11-16 may feature a
first cylindrically shaped band being positioned around a first subsystem of the well
tool. The first cylindrically shaped band can be operable to electromagnetically
couple with a second cylindrically shaped band. The second cylindrically shaped
band can be positioned around a second subsystem of the well tool. The
intermediate subsystem can be positioned between the first subsystem and the
second subsystem.
[0097] Example # 18 : A method can include transmitting an electromagnetic
signal, by a cylindrically shaped band associated with a first subsystem of a well tool,
to another cylindrically shaped band associated with a second subsystem of the well
tool. The method can also include insulating, by an insulator positioned around an
intermediate subsystem that is positioned between the first subsystem and the
second subsystem, a portion of an inner mandrel of the intermediate subsystem from
electrically interacting with the electromagnetic signal.
[0098] Example # 19 : The method of Example # 18 may feature the insulator
being included within multiple insulators positioned coaxially around the inner
mandrel of the intermediate subsystem. A metal sleeve can be positioned coaxially
around the multiple insulators and can include multiple grooves for receiving the
multiple insulators. The multiple insulators can separate the inner mandrel from the
metal sleeve.
[0099] Example #20: The method of any of Examples #18-1 9 may feature the
intermediate subsystem including a mud motor. The method may also feature two
insulative buffers being positioned at opposite longitudinal ends of a metal sleeve
coaxially surrounding the insulator. One of the two insulative buffers can be
positioned adjacent to a tubular joint.
[001 00] 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 comprising:
a first subsystem of a well tool, the first subsystem comprising a first
cylindrically shaped band positioned around the first subsystem and operable to
electromagnetically couple with a second cylindrically shaped band;
a second subsystem of the well tool, the second subsystem comprising the
second cylindrically shaped band positioned around the second subsystem; and
an intermediate subsystem positioned between the first subsystem and the
second subsystem, wherein the intermediate subsystem comprises an insulator
positioned coaxially around the intermediate subsystem.
2 . The communication system of claim 1, wherein the intermediate subsystem
comprises a mud motor and wherein a tubular joint is positioned between the first
subsystem and the intermediate subsystem.
3 . The communication system of claim 1 or 2, wherein a metal sleeve is
positioned coaxially around the insulator.
4 . The communication system of claim 3, wherein the insulator is included in a
plurality of insulators positioned between an inner mandrel of the intermediate
subsystem and the metal sleeve.
5 . The communication system of claim 4, wherein the metal sleeve comprises a
plurality of grooves for receiving the plurality of insulators, and wherein the plurality
of insulators are operable to create a space between the inner mandrel and the
metal sleeve.
6 . The communication system of claim 5, wherein two insulative buffers are
positioned around the inner mandrel and at opposite longitudinal ends of the metal
sleeve from one another.
7 . The communication system of claim 6, wherein one of the two insulative
buffers is positioned adjacent to a tubular joint.
8 . The communication system of claim 3, wherein two insulative buffers are
positioned around an inner mandrel of the intermediate subsystem and at opposite
longitudinal ends of the metal sleeve from one another, wherein the insulator
extends along a full longitudinal length of the inner mandrel between the two
insulative buffers, and wherein one of the two insulative buffers is positioned
adjacent to a tubular joint.
9 . The communication system of claim 3, wherein the insulator is operable to
electrically insulate the metal sleeve from the intermediate subsystem.
10 . The communication system of claim 3, wherein the insulator is operable to
separate the metal sleeve from an inner mandrel of the intermediate subsystem.
11. An assembly comprising:
an inner mandrel positioned within an intermediate subsystem of a well tool;
an insulator positioned coaxially around the inner mandrel;
a metal sleeve positioned coaxially around the insulator and making up an
outer housing of the intermediate subsystem; and
two insulative buffers positioned coaxially around the inner mandrel and at
opposite longitudinal ends of the metal sleeve from one another.
12 . The assembly of claim 11, wherein the intermediate subsystem comprises a
mud motor and one of the two insulative buffers is positioned adjacent to a tubular
joint.
13 . The assembly of claim 11, wherein the insulator is included in a plurality of
insulators positioned between the inner mandrel and the metal sleeve.
14. The assembly of claim 13, wherein the metal sleeve comprises a plurality of
grooves for receiving the plurality of insulators, and wherein the plurality of insulators
are operable to create a space between the inner mandrel and the metal sleeve.
15 . The assembly of claim 11, wherein the insulator is operable to electrically
insulate the metal sleeve from the intermediate subsystem.
16 . The assembly of claim 11, wherein the insulator is operable to separate the
metal sleeve from the inner mandrel.
17 . The assembly of claim 11, wherein a first cylindrically shaped band is
positioned around a first subsystem of the well tool and operable to
electromagnetically couple with a second cylindrically shaped band positioned
around a second subsystem of the well tool, wherein the intermediate subsystem is
positioned between the first subsystem and the second subsystem.
18 . A method comprising:
transmitting an electromagnetic signal, by a cylindrically shaped band
associated with a first subsystem of a well tool, to another cylindrically shaped band
associated with a second subsystem of the well tool; and
insulating, by an insulator positioned around an intermediate subsystem that
is positioned between the first subsystem and the second subsystem, a portion of an
inner mandrel of the intermediate subsystem from electrically interacting with the
electromagnetic signal.
19 . The method of claim 18, wherein the insulator is included within a plurality of
insulators positioned coaxially around the inner mandrel of the intermediate
subsystem, wherein a metal sleeve is positioned coaxially around the plurality of
insulators and comprises a plurality of grooves for receiving the plurality of
insulators, and wherein the plurality of insulators separate the inner mandrel from the
metal sleeve.
20. The method of claim 18, wherein the intermediate subsystem comprises a
mud motor, wherein two insulative buffers are positioned at opposite longitudinal
ends of a metal sleeve coaxially surrounding the insulator, and wherein one of the
two insulative buffers is positioned adjacent to a tubular joint.