Note: Descriptions are shown in the official language in which they were submitted.
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APPARATUS .AND METHOD FOR TRANSMITTING A SIGNAL FROM DEEP
IN A WELLBORE THROUGH A STRING OF TUBULARS
The present invention relates to an apparatus for
transmitting a signal from deep in a wellbore through a
string of tubulars. The invention particularly, but not
exclusively; relates to a method and apparatus for
transmitting communication data from deep in a wellbore
through a string of tubulars, such as a tool string or a
string of drill pipe to the surface during the
exploration, construction and production phases.
The transmission of data through a drill string has
been performed by several methods in the past. The first
of these was through the use of a Wire lina dropped
through the inside of the drill pipe. This wire line
would include a mechanical cable for placement and
retrieval of the sensors or controls as well as a
protected data pathway such as a wire or a fibre optic
cable. The expense of this system along with the
problems caused by damage to either the line or the pipe
and the pressure loss caused by this system led to the
development of other systems using communications methods
including the transmission of acoustic pulses caused by
pressure changes in the drilling fluids or the acoustic
transmission of the data to the surface. The primary
limitation of acoustic or pressure methods in the
transfer of data has been the very low data transfer
rate, in the order of a few bits per second. Further
attempts have been made in accomplishing the data
transfer by the use of loose wire or fibre optic cables
within the pipe, but none of these systems has proven to
be reliable.
U.S. Patent Application Publication No. 2002/0075114
CONFIRMATION COPY
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entitled "A Data Transmission System for A String of
Downhole Components", by Hall et al., teaches a system
for transmitting data through a string of downhole
components. In accordance with one aspect of the
invention, the system includes a plurality of downhole
components, such as sections of pipe in a drill string.
Each downhole component includes a pin end and a box end,
with the pin end of one downhole component being adapted
to be connected to the box end of an other. Each pin end
includes external threads and an internal pin face distal
to the external threads. Each box end includes an
internal shoulder face with internal threads distal to
the internal shoulder face. The internal pin face and the
internal shoulder face are aligned with and proximate
each other when the pin end of the one component is
threaded into a box end of the other component. The
system also includes a first communication element
located within a first recess formed in each internal pin
face and a second communication element located within a
second recess formed in each internal shoulder face. The
first and second communication elements are inductive
coils. The inductive coils each lie Within a magnetically
conductive, electrically insulating element, which take
the form of a U-shaped trough. The system also includes a
conductor in communication with and running between each
first and second communication element in each component.
The data transmission system of the Hall patent, however,
is difficult and expensive to manufacture. The Hall
system cannot be easily retrofitted into existing drill
pipe. If there is a failure in one section of pipe or in
a communication element between adjacent pipes, all data
communication is lost.
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The typical environment in which these downhole
communication systems are used requires that they be able
to withstand temperatures above 400 degrees Fahrenheit
and the turbulent flow of drilling fluids through the
pipe along with possible mechanical damage caused by
devices inserted through the pipe. Thus there is a need
for a reliable and durable communication method and
apparatus for transferring data at a high speed along a
drill pipe during operations down hole in a well bore.
Thus, there is a need for a downhole communication path
that is easy to manufacture and retrofit into existing
drill pipe.
In the prior art, transmission of signals from deep
in a well bore was carried out through Wires on a wire
lines or Wires wholly enclosed and encased in the wall of
the tubular, as disclosed a.n U.S. Patent Application,
publication under number 2002/0075114.
In accordance with the present invention, there is
provided an apparatus for transmitting a signal from deep
in a wellbore through a string of tubulars the apparatus
comprising an signal conductor and a tubular
characterised in that the signal conductor a.s located
adjacent an interior surface of the tubular. Preferably,
the signal conductor is fixed in relation to the interior
surface of the tubular.
Preferably, the signal conductor is an electrical
conductor. Most logging tools and downhole data
acquisition tools produce an electric signal. It is
preferred to retain the signal a.n electrical form.
Advantageously, the electrical conductor is isolated from
the interior surface of the tubular by a layer of
electrically insulative material. The insulative material
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may be a plastics material which is applied to the
electrical conductor or preferably, the interior surface
of the tubular is coated in the insulative layer.
Advantageously, the insulative layer adheres itself to
the interior wall of the tubular.
Advantageously, the electrical conductor is a wire.
The wire is preferably of round cross-section or most
preferably of rectangular cross-section, such that the
cross sectional area of the electrical conductor is
sufficient to carry the signal along a predetermined
length with an acceptable line loss and to minimise
impingement on the free internal diameter of the tubular.
It is important that tools, darts, bombs, plugs, wire
line tools, logging tools and any other objects or
instruments etc will not get stuck by a reduced diameter
bore in the tubular and also so that flow of mud will not
be affected. Preferably, the wire is embedded in a
protective layer . A thin layer over the top of the wire
preferably coats the conductor and provides a
electrically insulative layer and gives some damage
protection.
Alternatively or preferably, the electrical
conductor is a piece of foil. The piece or sheet of foil
may be a single sheet lining the entire surface of the
interior wall of the tubular. However, it is preferred
that the sheet of foil is split into a plurality,
preferably four strips separated by an electrically
insulative gap or protective layer. Advantageously, a
protective layer covers the sheet of foil.
Preferably, the electrical conductor comprises a micro
strip line. Advantageously, the micro strip comprises a
conductive core and an insulating layer encasing the
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conductive core. Preferably, the core is in the form of a
rectangular section strip. Advantageously, the core a.s
between 0.048mm (0.0019") and 0.05mm (0.002") thick. The
width of the core may be in the order of 1mm. Preferably,
the micro strip line has an overall thickness of less
than lmm and preferably less than 0.65mm, so that it does
not significantly impinge on the bore of the tubular.
Advantageously, the insulating layer is encased in an
outer conductive layer, preferably to form a coaxial
conductive path. Advantageously, the outer conductive
layer is earthed, which preferably reduces interference
and reduces line losses by acting as an electrical
shield.
Preferably, the signal conductor extends
substantially the entire length of the tubular.
Advantageously, the tubular comprises a plurality of
signal conductors. Preferably, to provide redundancy by
passing the same signal through each cable or to increase
the bandwidth of the apparatus. Preferably, one of the
plurality of signal conductors carries the signal and
another of the signal conductors carries substantially
the same signal.
Advantageously, the signal conductor is provided with
means for transferring the signal from the signal
conductor to another signal conductor in an adjacent
tubular. The means may comprise a coupling. The coupling
may be a conductive coupling, an inductive coupling, an
acoustic coupling, or a digital repeater may be used.
Preferably, the signal conductor is provided with an
antenna at at least one end of the tubular, to transmit
or receive the signal from an adjacent tubular or an
amplifier-receiver. Preferably, a receiving antenna is
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provided at one end of the tubular and a transmitting
antenna is provided at the other end of the.tubular, the
signal conductor arranged therebetween. Advantageously,
the antenna comprises the electrical conductor following
the interior perimeter of the tubular.
Preferably, the apparatus further comprises an
amplifier-receiver. The amplifier-receiver may be place
at the end of every tubular. Preferably, at one end of
every drill pipe, but alternatively at the end of every
IO stand of drill pipe. Preferably, the transmission
apparatus is the transmission apparatus as set out in the
following statements and the amplifier receiver is of the
type set out in those statements.
The signal conductor may be arranged in a recess in
I5 the interior wall of the tubular.
Preferably, tubular is drill pipe. Drill pipe of the
type used in drilling and in tool strings.
The present invention also provides a method for
transmitting a signal from deep in a wellbore through a
20 string of tubulars, the method comprising the steps of
passing the signal through an electrical conductor
located adjacent an interior surface of the tubular.
Preferably, the method for manufacturing a drill pipe,
the method comprising the steps of positioning and fixing
25 an electrical conductor adjacent an interior surface of a
drill pipe section.
The present invention also provides a transmission
apparatus for transmitting a signal from deep in a
wellbore through a string of tubulars, the apparatus
30 comprising an electrical conductor arranged in a tubular
characterised in that the apparatus further comprises an
amplifier-repeater. The electrical conductor could be
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wholly within the wall of the tubular, in a recess in the
interior wall of the tubular or wholly on the inner
surface of the tubular.
Preferably, the amplifier-repeater comprises a
signal amplifier and a power source. Advantageously, the
power source comprises a piezoelectric device. The
electric charge is obtained from vibration in the tubular
caused by flow of mud, action of a mud motor and/or by a
drill bit on the end of a pipe string. It is also within
the scope of this invention use this effect to create
electrical charge by any other means. Alternatively or
preferably, the power source comprises a battery. The
battery or a capacitor may be rechargeable and may have a
piezoelectric device charging the battery or capacitor.
Preferably, the transmission apparatus further
comprises a receiver antenna. Preferably, for receiving
an RF/induced signal from an antenna hard wired to the
end of an electrical conductor a.n an adjacent tubular,
the received signal is then amplified by the amplifier
receiver.
Advantageously, the electrical conductor comprises a
transmitter antenna. Preferably, the transmitter antenna
may simply be a length of the conductor arranged in
close, preferably parallel proximity to a corresponding
receiver antenna, which may be a similar length 'of
conductor which preferably has similar impedance
characteristics.
Advantageously, the apparatus further comprises a
transmitter antenna. Preferably, for transmitting an the
amplified signal by RF/induction to an antenna hard wired
on the end of an adjacent tubular.
Preferably, the electrical conductor comprises a
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receiver antenna. Preferably, the receiver antenna may
simply be a length of the conductor arranged in close,
preferably parallel proximity to a corresponding
transmitter antenna, which may be of a similar length of
conductor which preferably has similar impedance
characteristics.
Advantageously, the transmission apparatus further
comprises a second electrical conductor and a second
amplifier-repeater, which may be used to carry the same
signal, or a additional signal. Preferably, the
transmission apparatus further comprises communication
means between the first and second amplifier repeaters.
Preferably such that, if one line is cut, both amplifiers
can transmit the signal through the next tubular or if
one of the amplifier repeaters fails, the signal from the
one is automatically forwarded to the other amplifier-
repeater for transmission through the next tubular.
Preferably, the transmission apparatus further
comprises a third electrical conductor and a third
amplifier-repeater. Preferably, for carrying the same
signal, or advantageously a second signal.
Advantageously, the transmission apparatus further
comprises communication means between the first, second
and third amplifier repeaters. Preferably such that, if
one or two lines is cut, all three amplifiers can
transmit the signal through the next tubular or if one or
two of the amplifier repeaters fails, the signal from the
one is automatically forwarded to the other amplifier-
repeater for transmission through the next tubular.
Advantageously, the transmission apparatus further
comprises a fourth electrical conductor and a fourth
amplifier-repeater. Preferably, for carrying the same
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signal, or advantageously the second signal.
Preferably, the transmission apparatus a further
comprises communication means between the first, second,
third and fourth amplifier repeaters. Preferably, such
that, if one, two or three lines are cut, all four
amplifiers can transmit the signal through the next
tubular or if one, two or three of the amplifier
repeaters fails, the signal from the one working
amplifier repeater is automatically forwarded to the
other amplifier-repeaters in the next tubular.
Advantageously, the amplifier repeater is located a.n a
ring. The ring may form an integral part of the tubular,
or may be insertable, removable and replacable between
adjacent tubulars. The communication between the
electrical conductor and the amplifier-repeater in the
ring, may be through conductive contact or by inductive
antennae. Preferably, the tubular is a drill pipe having
a threaded pin at one end and a threaded box at the other
wherein the ring is insertable in the box of one drill
pipe section and fixed in position by the pin of an
adjacent drill pipe section. Advantageously, the ring
comprises a plurality of receiver-amplifiers.
The present invention also provides a ring of the
transmission apparatus of the invention. Preferably, the
ring comprises at least one amplifier-repeater, a power
supply, a receiver antenna, a transmitter antenna.
Advantageously, the ring further comprises at least a
second amplifier-repeater, a power supply, a receiver
antenna, a transmitter antenna. Preferably, the ring
comprises at least four such amplifier-repeater, a power
supplies, a receiver antennae, a transmitter antennae for
each.
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The invention also provides a tubular comprising the
transmission apparatus of the invention.
The invention also provides a string of the tubulars
of the invention, the tubulars connect end to end,
wherein the amplifier-repeaters are in series and are
powerful enough to drive the signal past at least one
following amplifier repeater and on to a third amplifier
repeater.
The invention also provides a method for transmitting a
signal from deep in a wellbore through a string of
tubulars, the method comprising the steps of passing a
signal through an electrical conductor arranged in a
tubular and amplifying the signal with an amplifier
repeater to enable the signal to travel at a distance
substantially equal to between one and ten lengths of the
tubular. Preferably, the method further comprises the
step of amplifying the signal with the amplifier-repeater
to enable the signal to travel at a distance
substantially equal to three to five lengths of the
tubular. Preferably, such that if an amplifier-repeater
fails, the signal can leapfrog over the broken amplifier
repeater to the next amplifier-repeater in the next
tubular in series with the first. Advantageously, the
step of passing the same signal through a second
electrical conductor arranged in the tubular and
amplifying the signal with a second amplifier-repeater to
enable the signal to travel at a distance substantially
equal to between one and ten lengths of the tubular.
Preferably, the first and second amplifier-repeaters are
in parallel and have communication means between them.
Advantageously, such that if one amplifier repeaters
fails or if one signal conductor fails]
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In accordance with the present invention, there is
provided a method and apparatus for transmitting data
through a drill pipe made up of multiple pieces of drill
pipe sections for communication between the surface and a
down hole tool in a well bore. The interior of the drill
pipe is coated with a thin non-conductive material. The
primary use of the present invention is in transferring
data between instruments and/or controls located at the
bottom and top of multiple lengths of pipe used for
drilling wells for oil, gas, or other natural resources.
Each length of this drill pipe contains one or more thin
conductive wires (for example, 36 gauge wire) or
conductive layers of material between the pipe and one or
more insulating layers of nonconductive coating.
Communication between drill pipe sections of data through
these conductive materials between drill pipe sections is
performed either by the coupling between drill pipe
sections through transmitter-receiver rings, mechanical
connections, inductive coupling, or the use of digital
repeaters within the collection of pipes. These
repeaters can be RF receiver-transmitters coupled either
mechanically or through the electromagnetic field
produced by these repeaters between the conductive
members within the pipes.
In a preferred embodiment, a transmitter receiver
ring (T-Rang) amplifier-repeater is provided at each end
of a drill pipe section. The T-Ring amplifier repeater
picks up signals from one or more wires embedded in an
adjacent pipe section above the T-Ring, receives and
amplifies the signals, and transmits the signals through
wires embedded in the pipe section below the connection.
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The preferred embodiment comprises four wires embedded in
a protective coating inside the drill pipe. These four
wires are brought to the face of each end of the drill
pipe section and embedded in a coating and extended on
the face as four quadrants of a circle, each section
occupying slightly less than 90 degrees, so that the
wires are insulated from each other through each drill
pipe section. In an alternative embodiment, a micro strip
line communication path is provided on the inside of the
drill pipe.
A ring-shape Transmission element or "T-Ring" is
provided between drill pipe sections. The ring-shaped T-
Ring volume can be fitted easily between drill pipe
sections. The T-Ring is inexpensive to manufacture and
easy to install between existing drill pipe sections
fitted with the transmission path of the present
invention. The signal received by each T-Ring is
amplified and electrically transmitted through the wires
in each succeeding drill pipe section to each successive
T-Ring. The T-Ring receives the signal, amplifies it,
and retransmits it to the adjacent wire through the next
pipe. Additional features include detecting failed T-
Ring sections and only retransmitting signals associated
with functional T-Ring sections. The T-Ring provides its
own power from a piezoelectric power generator powered by
drilling vibrations and mud flow turbulence through the
tool and T-Ring. The T-Ring provides intelligent
checksums cyclic redundancy checking and digital packet
hand shaking. The dynamic range of each T-Ring is
sufficient transmit a signal posting several (e.g. 2-10)
drill pipe sections to enable transmitting past failed T-
Rings. T-Rings can be active or passive and intermixed
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so that only every N (e. g., 5) T-Rings are amplifiers
placed in the drill string to boost the signal through
passive T-Rings between amplifier T-Rings. T-Rings can
also be alternately fired so that amplifying T-Rings take
turns amplifying and retransmitting the signal while
others rest and store energy to capacitively charge up
electric energy to amplify and retransmit when it is
their turn.
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For a better understanding of the present invention,
reference will now be made, by way of example, to the
accompanying drawings, in which:
Figure 1 is a schematic illustration of a typical
drilling system;
Figure 2 is a schematic illustration of a conductor
placed in a tubular under a protective coating in a
preferred embodiment of the present invention;
Figure 3 a.s a view in cross-section taken along line
III-III of Figure 2;
Figure 4 is an end view in cross-section of an
alternative embodiment of the present invention;
Figure 5 is a side view of a coupling ring located
between two drill pipe sections;
Figure 6 is an end view in cross section of the
preferred ring showing embedded wires;
Figure 7 is an end view of a preferred embodiment of
a T-Ring of the present invention;
Figure 8 is a cross section of the T-Ring shown in
Figure 7;
Figure 9 is an end view in cross section of a
preferred T-Ring shown with a piezoelectric material
coated on the interior surface for power generation;
Figure 10 is a schematic illustration of an
alternative embodiment wherein a micro strip line is
provided inside of a drill pipe section as a transmission
path;
Figure 11 a cross section of a preferred micro strip
line provided as a communication path inside of a drill
pipe;
Figure 12 is a table illustrating characteristic
impedance for a full-section strip transmission line and
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line widths; and
Figure 13 is an illustration of a quarter wave
impedance matching section.
The present invention enables high speed, real-time
data acquisition of formation evaluation data, e.g.,
resistivity and seismic data. In a preferred embodiment,
coatings are applied to the inside of the drill pipe
section via several methods. Internal coating must
protect the interior of the drill pipe and wires from
damage and corrosion in temperatures up to 260°C (500°F).
Sophisticated thermo plastics, such as Halar~ are
applied in coating thickness from 0.127mm to 0.76mm (5-30
1000th of an inch (mils)). Pipes can be drill pipe, log
pipe or tubing pipes which are thermally pre-cleaned to
remove oils and other contaminants that may cause
problems with reuse of the abrasive during blasting the
inside of the pipe. The blasting also loosens scale
inside the drill pipe. The internal surface is then
abrasive blasted to take the metal to SAE white metal
specification so nothing is left on the internal pipe
surface but steel.
Blasting leaves a 0.0127mm to 0.038mm (1/2 - 1 1/2
mil) deep rough pattern on the interior surface of the
drill pipe. A phenolic, epoxy or themoplastic primer is
then applied to the interior surface 0.05mm (2 mils)
thick to account for the 0.038mm (1 1/2) rough pattern
and provides a smooth surface on top of the rough
surface. Then depending whether a liquid or powered
coating is applied, multiple coatings are applied with an
intermediate bake cycle between each coating. The bake
cycle hardens the applied coating so that an application
lance running through the pipe does not score or harm a
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previously applied coating layer. Once the desired
thickness is reached by the application of multiple
layers, a final bake cycle is performed to consolidate
all the layers. The intermediate bake cycle is
approximately 177°C (350°F) and the final bake cycle
232°C to 246°C (450°F to 475°F).
In powder coating, however, a single coat is
applied. Two methods are used to apply the powder
coating. One method is to run a lance down the centre of
a heated pipe, spraying the powder on the interior of the
pipe while the pipe is rotating. The lance is inserted
fully into the pipe and drawn along the pipe at a
standardized rate to achieve the desired thickness
coating the inside of the pipe. Another method is to
rotate the pipe, pull a vacuum on the pipe and place a
charge of powder into one end of the pipe and purge air
behind the charge so that the vacuum pulls the charge of
powder along the pipe. The pipe a.s preferably preheated
to facilitate adhesion of powder to the pipe. Still
another method of coating the internal wall of the pipe
is to place a fibreglass liner in the pipe and epoxy the
liner to the interior surface of the drill pipe. Epoxy
or grout is used to hold the liner in place . A wire or
fibre optic cable can be placed between the interior pipe
surface and the liner. Another method of coating a.s
centrifugal casting. A wire is placed on the interior
surface of the pipe and a fibreglass cloth placed over
the wire and spun to generate 9 g's of force at the
interior surface of the pipe. Epoxy is flowed into one
end of the pipe. The epoxy is smoothed out and the pipe
heated to cure the epoxy.
Each coating method can be used to place a wire or
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conductive path on the inside of the pipe beneath the
surface of the coating. After the pra.me step, wires or
conductive paths are laid down and coated. Preferably,
Teflon coated wires are laid down on the surface of the
pipe. Teflon is able to withstand 260°C (500°F), Which
is above the range of the application of the coating so
the Teflon wire survives the coating. 36 gauge wire can
be used with as little as 0.5mm (20 mils) of coating and
fully cover the wire. The coated wire in the pipe can
then be tested under high pressure and high temperature.
The thin coating is important so that the interior
diameter of the pipe is not reduced to the extent that it
adversely affects the hydrodynamic or pressure carrying
properties of the pipe. Initially the thin coating
smoothes and improves the hydraulic and hydrodynamic
properties of the pipe, however, further restriction or
reduction of the drill pipe interior diameter by
increasing the layer too much reduces fluid carrying
ability of the pipe.
Thicker coatings are also less flexible and reduce
the flexibility of the coating. Thus, the thinner
coating is used (0.75mm (30 mils) maximum, preferably,
2mm (80 mils) for Halar~ an other thermoplastics in
special cases) to make the coating flexible so that it
does not crack or break during use downhole.
Below 0.127mm to 1.52mm (5 to 6 mils) coating
thickness abrasion resistance may be a problem. For
example, mud flow at a velocity that causes turbulent
flow, exacerbated by cuttings in the mud, may cause
erosion in the coating that may prematurely reduce the
life of a coating due to erosion and/or penetration of
the coating.
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Thus, the coating is preferably between 0.127mm and
0.762mm (5 and 30 mils). Flexibility is extremely
desirable in highly deviated well bore. Thus, a 0.762mm
(30 mils) coating has been successfully tested in the
field with a 36 to 40 gauge wires (approximately
equivalent to 0.127mm to 0.0787mm diameter wire) under
the 0.762mm (30 mils) coating.
Another consideration a.s that the thin wire embedded
in pipe there is capacitance and inductance between the
wire and the pipe metal surface that forms a tuned
circuit. The tuned circuit is variable down the length
of the pipe. That is, one section of a pipe is tuned at
one frequency and another section of the pipe is tuned at
a different frequency. Increasing the resistance of the
wire by using a smaller Wire reduces the height of the
peak to obtain a more gradual peak (the Q of the
circuit). Thus you reduce the Q by increasing the wire
resistance. Thus, this may be an advantage since T-Ring
repeaters are provided.
In an alternative embodiment (Figure 4), a first
insulating layer is applied to the interior of the drill
pipe, then a conductive second coating and an insulating
top coat. This forms a layer of conductive coating. A
single breach a.n the insulating layer may cause the
conductive mud to short out the conductive layer. The
coating protects the conductive wires from turbulent mud
flow abrasion.
In another embodiment the conductive layer can be
divided into longitudinal strips so that the entirety of
the conductive paths are not shorted by a breach at a
single point in the insulating layer adjacent the mud.
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Multiple wires also serve to provide multiple conductive
paths that are not subject to a single point of failure.
In an alternative embodiment, electrical signals are
converted to an acoustic signal that travels down the
interior of the pipe or the body of the pipe. Travelling
down the body of the pipe of each drill pipe section and
bridging the juncture of drill pipe section with an
acoustic to electric conversion to overcome the
difference of acoustic impedance at the drill pipe
connections between sections.
The inside of the T-Ring is exposed to turbulent mud
flow which provides pressure variations on the
piezoelectric device formed on the interior surface of
the T-Ring adjacent the mud flow to generate power to the
T-Ring. Drilling vibrations can also be used to generate
power via the piezoelectric device. The processor in
each of the four receiver sections, in each T-Ring
preferably performs a check sum. The check sums are
compared and only the received signals with a matching
check sum are retransmitted by the T-Ring. In another
embodiment the T-Ring provides processor with memory
provide a store and forward digital packet communication
scheme wherein a digital packet is received and stored
until a signal is received from another device or T-Ring
to retransmit the packet. Preferably each T-Ring and
each individual T-Ring section has a unique digital
address so that a T-Ring or T-Ring section can be
reprogrammed, commanded or shut down by commands directed
to the address via the communication path. Specific
transmission and operations modes for the T-Rings can be
commanded by commands sent to the T-Rings and T-Ring
segments via the communication path. A lithographic
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technique can be used to form the antennae in the T-
Rings.
Figure 1 illustrates a schematic diagram of a MWD
(Measurement Whilst Drilling) system 10 with a drill
string 20 carrying a drilling assembly 90 (also referred
to as the Bottom Hole Assembly, or "BHA") conveyed in a
"well bore" or "borehole" 26 for drilling the well bore.
The drilling system 10 includes a conventional derrick 11
erected on a floor 12 Which supports a rotary table 14
that is rotated by a prime mover such as an electric
motor (not shown) at a desired rotational speed. The
drill string 20 includes tubing such as a drill pipe 22
extending downward from the surface into the borehole 26.
The drill bit 50 attached to the end of the drill string
breaks up the geological formations when it is rotated to
drill the borehole 26. If a drill pipe 22 is used, the
drill string 20 is coupled to a draw works 30 via a Kelly
joint 21, swivel 28 and line 29 through a pulley 23.
During drilling operations, the draw works 30 is operated
to control the weight on the drill bit 50, which is an
important parameter that affects the rate of penetration.
The operation of the draw works is well known in the art
and is thus not described in detail herein.
During drilling operations, a suitable drilling
fluid 31 from a mud pit (source) 32 is circulated under
pressure through a channel in the drill string 20 by a
mud pump 34. The drilling fluid passes from the mud pump
34 into the drill string 20 via a desurger 36, fluid line
38 and Kelly joint 21. The drilling fluid 32 is
discharged through an opening in the drill bit 50 at the
bottom of the borehole. The drilling fluid 31 circulates
up hole through the annular space 27 between the drill
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string 20 and the borehole 26 and returns to the mud pit
32 via a return line 35. The drilling fluid acts to
lubricate the drill bit 50 and to carry borehole cutting
or chips away from the drill bit 50. A sensor S1
preferably placed in the line 38 provides information
about the fluid flow rate. A surface torque sensor S2
and a sensor S3 associated with the drill string 20
respectively provide information about the torque and
rotational speed of the drill string. Additionally, a
sensor (not shown) associated with line 29 is used to
provide the hook load of the drill string 20.
In a preferred embodiment of the invention, a
downhole motor 55 (mud motor) is disposed in the drilling
assembly 90 to rotate the drill bit 50 and the drill pipe
22 is rotated usually to supplement the rotational power,
if required, and to effect changes in the drilling
direction.
In the preferred embodiment of Figure 1, the mud
motor 55 is coupled to the drill bit 50 via a drive shaft
(not shown) disposed in a bearing assembly 57. The mud
motor rotates the drill bit 50 when the drilling fluid 31
passes through the mud motor 55 under pressure. The
bearing assembly 57 supports the radial and axial forces
of the drill bit. A stabilizer 58 coupled to the bearing
assembly 57 acts as a centralizer for the lowermost
portion of the mud motor assembly.
A drilling sensor module 59 is placed near the drill
bit 50. The drilling sensor module 59 contains sensors,
circuitry and processing software and algorithms relating
to the dynamic drilling parameters. Such parameters
preferably include bit bounce, stick-slip of the drilling
assembly, backward rotation, torque, shocks, borehole and
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annulus pressure, acceleration measurements and other
measurements of the drill bit condition. A suitable
communication sub 72 sends data to the surface and
receives data from the surface a communication path
conductive path provided by the present invention. The
drilling sensor module 59 processes the sensor
information and transmits it to the surface control unit
40 via the communication path provided by the present
invention.
The communication sub 72, a power unit 78 and an
Nuclear Magnetic Resonance (NMR) tool 79 are all
connected in tandem with the drill string 20. Flex subs,
for example, are used in connecting the NMR tool 79 in
the drilling assembly 90. Such subs and tools form the
bottom hole drilling assembly (BHA) 90 between the drill
string 20 and the drill bit 50. The drilling assembly 90
makes various measurements including the pulsed nuclear
magnetic resonance measurements while the borehole 26 is
being drilled. The communication sub 72 obtains the
signals and measurements and transfers the signals via
the communication path provided by the present invention
to the surface to be processed. Alternatively, the
signals can be processed using a downhole processor in
the drilling assembly 90. The BHA 90 may be on the bottom
end of a drill string, which may be from 100m to 20,OOOm
or more a.n length.
The surface control unit or processor 40 also
receives signals from other downhole sensors and devices
and signals from sensors S1-S3 and other sensors used in
the system 10 and processes such signals according to
programmed instructions provided to the surface control
unit 40. The surface control unit 40 displays desired
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drilling parameters and other information on a
display/monitor 42 utilized by an operator to control the
drilling operations. The surface control unit 40
preferably includes a computer or a microprocessor-based
processing system, memory for storing programs or models
and data, a recorder for recording data, and other
peripherals. The control unit 40 is preferably adapted
to activate alarms 44 when certain unsafe or undesirable
operating conditions occur.
Turning now to Figure 2 a schematic illustration of
a tubular with one or more conductive wires 204
preferably paths, comprising 36 gauge wire or conductive
strips are provided. Preferably, the conductive strips
have an equivalent cross sectional conductive area to 36
gauge wire. The conductive Wires 204 are insulated from
the interior surface 210 of the wall 202 of the tubular
by the use of non-conductive material coating 208 bonded
to the pipe, preferably by the application of one or more
thin layers of non-conductive materials. Data is
transferred along a communication path between the
tubular 200 via the conductive path or conduit 204. The
communication path, preferably wires) 204 is then coated
by thin protective and/or insulating layer 206 to protect
communication path 204 from abrasion. The layers are
preferably approximately 0.05mm to 1mm (2 to 40 mils)
thick. Thicker Wires and layers can be utilized,
however, the thin wires and coating layers are preferred
for enhanced drill pipe flexibility during drilling
operations. A coating thinner than 0.127mm (5 mils),
preferably 5 millimetres is too thin to protect against
abrasion properly. The tubular shown may take the form of
a drill pipe, which additionally comprises a box at one
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end and a pin thread at the other.. It should be noted
that the relative dimensions of the wall of the tubular,
the wires 204, the insulative coating 208 and the
protective coating 206 are not to scale and are simply
for illustrative purposes only.
Turning now to Figure 3, a cross-section of the wire
provided in Figure 2 is illustrated taken along line III-
III. As shown in Figure 3, communication path 204 lies
between interior surface 210 of the wall 202 of the
tubular 200 and the interior surface 211 of coating 206.
The coating 206 may have a thickness which reaches the
top of the wire, as indicated by the dashed line, or may
cover the wire completely and may advantageously provide
a thickness above the top of the wire for protecting the
wire. An additional coating may be applied to the
interior surface 210 to insulate communication path 204
from the interior surface 210 of tubular 200.
Turning now to Figure 4, in an alternative
embodiment, a method and apparatus according to the
present invention comprises the use of one or more layers
260 of a non-conductive material applied to coat the
interior surface 210 of a tubular 200, such as a section
of drill pipe. The application of the non-conductive
material is followed by the application of one or more
layers of conductive material 250 and the further
application of non-conductive materials over the
conductive material 240. The conductive material 250
forms a communication path for data from one end of a
drill pipe section to the other. This alternation of
application of conductive and nonconductive layers can be
repeated allowing multiple separate conductive layers and
communication. These layers of conductive material are
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then connected through a T-Ring described below or by
mechanical means, induction, or shared electromagnetic
fields from one section of drill pipe to another section
of drill pipe allowing the transfer of data between
multiple joints of the preferred drill pipe. In an
alternative embodiment, the present invention comprises
repeaters 212 located at points within the communication
path or conduit. These repeaters can be located between
the internal upset on the back end of the box connection
of the drill pipe and the end of the pin connection made
up into it. It is also possible to temperature stabilize
the electronics by boiling a coolant into the pipe ID at
the high pressures normally encountered. The repeaters
or T-Rings can be powered by piezoelectric, magneto
hydrodynamic or other methods or generating power down
hole. A battery may also be used to provide power.
The advantages provided by the addition of a layer
of non-conductive material over the conductive materials
include the protection of the conductive materials from
abrasion damage and the intrusion of partially conductive
materials as well as the reduced pressure loss allowed by
the location of the conductive materials on the pipe
surface. The addition of the internal coating preferably
also provides improved hydrodynamics for flow within the
drill pipe. The communication path coating is preferably
non-conductive to insulate the conductive communication
path from the interior of the drill pipe section, or from
other conductive paths formed inside the drill pipe
section.
Each section of drill pipe is preferably abrasive
blasted and coated with a plastic (or other non
conductive) coating having a high resistivity as known in
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the state of the art. This drill pipe section is then
tested to insure that the high resistance coating is not
breached by metal shavings, or pinholes in the coating.
After this testing is completed a conductive material is
applied. This can be a metal filled plastic coating, a
thin layer of conductive foil treated to adhere to the
plastic coating, or one or more wire conductors treated
to adhere to the coating. This conductive layer is then
covered by one or more additional layers of non-
conductive coating. This drill pipe section is again
tested to insure that the conductive layer is intact and
that it has a high resistance to the pipe body or to a
conductive fluid held Within the pipe. The conductive
layer is then connected to either an electrical
connector, or to an inductive coupling ring, or to an
electronic repeater. The system a.s then further sealed
by a non-conductive coating and tested.
Once multiple drill pipe sections have been prepared
the drill pipe sections are connected to form a drill
string having a communication path. The communication
path enables data to be transmitted through the
conductive layer from one end of the connected drill pipe
section to the other end. The conductive path may also
be formed as conductive longitudinal strips rather than a
continuous layer.
There are many methods of installing a suitable wire
for the present invention. These include centrifugal
casting of a coating, preferably plastic over the wire,
preheating the pipe and depositing the coating using a
vacuum system, or applying the coating by flocking the
coating over the wire or conductive path.
These techniques perform well in harsh environmental
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conditions associated with down hole drill pipe service.
In another embodiment, the apparatus and method comprises
using Teflon coated wire pairs. These Teflon coated wire
pairs are applied over a non-conductive primer coat
giving dual insulation. The finish coat is applied over
the wire. On a section through the wire one would find
the substrate, a thin phenolic primer, teflon, copper,
teflon, and the finish coat of epoxy-phenolic.
Turning now to Figures 5 and 6, a preferred
embodiment of a communication coupling ring (T-Ring) is
illustrated. A major difficulty in communication through
wire inside drill pipe is the connection problem between
drill pipe sections. In a passive system without an
amplifier-repeater between drill pipe sections, the
coefficient of coupling between sections would have to be
at least 990 on each of the 700 connections possible on a
deep well string to enable communications through the
drill string within the dynamic range of present
electronics.
An electronic device, such as a sensor/transducer
produces an electrical signal which is generally
amplified and transmitted through a wire to a processing
unit such as a computer. Due to line losses in the wire,
the signal can only travel a specified distance through a
wire. An amplifier-repeater is inserted at a point equal
or less than the recommended distance along the wire that
the signal can be sent. The amplifier-repeater boosts the
signal at those points so that the signal can travel
through the following section of wire. A problem with
known amplifier-repeaters is that they require a source
of power and are often the weak point in reliability.
The environment in the drill string may include pressures
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above 700 bar (20,000 psi) absolute pressures and
temperatures above 200 degrees Centigrade with possible
excursions up to 250 degrees Centigrade.
Thus, in a preferred embodiment, a T-Ring amplifier
s repeater is preferably provided at each drill pipe
connection between drill pipe sections. The T-Ring
amplifier repeaters pick up signals from the conductive
path, e.g., one or more conductive paths, wires or strips
are embedded in a drill pipe section above the T-Ring,
amplifies the signals, and transmits the signals through
wires or conductive paths embedded in the pipe below the
T-Ring connection. A preferred embodiment comprises four
wires embedded in a protective coating inside the drill
pipe. These four wires are brought to the face of the
drill pipe connection on each end of a drill pipe section
and embedded in the coating as four sections or quadrants
of a circle, each section occupying slightly less than 90
degrees, so that the wires are insulated from each other
through each drill pipe section. The connection between
the drill pipe is provided by a T-Ring with a ring-shaped
volume which is fitted with the transmitter/receiver
amplifier-repeater. The signal is electrically
transmitted through the conductive path, a . g . , wire in a
drill pipe section to each T-Ring. The T-Ring receives
the signal from the wire in the drill pipe, amplifies the
signal, and transmits the amplified signal to the
adjacent wire through the next drill pipe section.
The T-Ring comprises of (one or more of each) a
power source, preferably utilizing mechanical energy
available from the drill pipe to create electrical power,
a receiver that senses the signal from the wire in the
transmitting pipe, an amplifier to increase the signal
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power, and a transmitter which couples the amplified
signal to wire in the next pipe. This unit is totally
sealed and easily replaceable while the drill pipe
sections are being connected. The electronics in the T-
Ring preferably provide signal conditioning devices,
dedicated logic circuits for fault detection, and self-
repair by eliminating the signal conduits which are
damaged. The T-Ring provides sufficient dynamic range so
that the complete failure of one or more T-Ring
amplifier-repeaters can be tolerated by amplification of
surrounding rings that enable a T-Ring to transmit past a
failed T-Ring to the next drill pipe section or T-Ring.
In an alternative embodiment, the T-Rings simply receive
and retransmit between each other without the benefit of
a conductive path in the drill pipe section between the
T-Rings.
In an alternative embodiment the drill pipe wires
terminate in a passive antenna at both ends of the drill
section pipe and the T-Ring amplifier-repeater acts as an
active receiver and transmitter without any connection
between the drill pipe wires and the ring. Thus the ring
is a drop in part that fits loosely between the gap
between the bottom of the pin and the bore of the box
much like corrosion rings inserted in drill strings
today.
Turning now to Figure 5, a preferred T-Ring 300 is
shown installed between two adjacent drill pipe sections
200 . As shown in Figure 5 , T-Ring 300 drops in between
drill pipe sections 200 during connection and assembly of
a series of drill pipe sections to form a drill string.
Turning now to Figure 6, the drill pipe end 302 of a
drill pipe section 200 is illustrated showing four
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conductive paths 308, 310, 312, and 314, terminating at
the drill pipe end 302 of drill pipe section 200. Each
conductive path is extended in a quadrant of
approximately 85 degrees forming an arc along the
circular cross section 302 of the drill pipe section end.
Conductive paths 308, 310, 312, and 314 are extended
along the drill pipe section end face 302 a.n arcs 309,
311, 313, and 315 respectively. The centre 318 of the
drill pipe section is hollow to allow flow through the
drill pipe. The conductive path arcs 309, 311, 313 and
315 are covered with a coating or washer to insulate
and/or protect the conductive path arcs 309, 311, 313 and
315 forming the communication path end. The arcs are
separated by a space 301 to prevent the conductive paths
from touching.
Turning now to Figure 7, a cross section of a
preferred T-Ring 400 a.s shown. The face of T-Ring 400
comprises four T-ring segments 409, 411, 413, and 415
receiver-transmitter antennae of the cylindrical T-Ring
400.
As shown in Figure 7, each T-Ring has a power supply
420 and an amplifier 422. The power supply 420 can be a
heat resistant battery, either long life or disposable or
rechargeable or a power generating device such as a
piezoelectric element that generates electric power from
the mechanical vibration of drilling or turbulent flow
and pressure fluctuations of mud flow through centre
opening 418 of T-Ring 400. A mud motor may also generate
power transferred to the T-Rings via inductive coupling
or through the conductive paths. In this case, the data
signal is super imposed over the power on the data path
308, 310, 312, or 314. Amplifier 422 contains signal
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conditioning circuitry and a processor to perform cyclic
redundancy checking, fault detection and digital packet
reception and retransmission.
In a preferred embodiment the T-Rings take turns
storing power for operation and alternately receiving and
retransmitting data signals. Preferably a T-Ring has
sufficient dynamic range to transmit past a failed T
Ring. Thus in a series of five consecutive T-Rings only
one of five rings need be active at one time to receive
and transmit while the other four T-Rings are storing
power in e.g. a capacitor. Each T-Ring takes 1 of 5
turns receiving and transmitting. If one of the five T-
Rings fails it is skipped over by adjacent T-Rings. For
example if T-Ring 3 fails T-Ring 2 would communicate with
T-Ring 4 instead of the normal T-Ring 2 to 3 and T-Ring 3
to 4 T-Ring communication.
Figure 8 is a cross section AA of Figure 7. As
shown in Figure 8, T-ring segment 409 comprises a
receiver antenna (not referenced) located on face 401 and
a transmitter antenna (not shown) located on face 402. T-
ring segment 411 comprises a receiver antenna (not
referenced) located on face 401 and a transmitter antenna
(not shown) located on face 402. T-ring segment 413
comprises a receiver antenna 413a located on face 401 and
a transmitter antenna 413b located on face 402. T-ring
segment 415 comprises a receiver antenna 415a located on
face 401 and a transmitter antenna 415b located on face
402. The receiving and transmitter antennae are covered
with a protective coating 421. The receiver antennae are
located on T-Ring face 401 and each receives signals from
an antenna 309, 311, 313 and 315 on the end 302 of an
adjacent drill pipe section 200. The signal received by
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receiver antenna is amplified by its own amplifier 420
powered by its own power supplies 422 and retransmitted
by the transmitter antenna to antennae in the pin of a
connected drill pipe.
Processor/Amplifiers 420 are interconnected by data
path 423 for status and reporting between the four T-Ring
segments 409; 411; 413; and 415. Figure 9 is a cross
section of a preferred T-Ring shown with a piezoelectric
material coated on the interior surface for power
generation.
Thus each T-Ring comprises four sections 409; 411;
413; and 415 each comprising receiver and transmitter
antennas, power supplies 422 and process/amplifiers 420.
The processor can detect when a section 409, 411, 413, or
415 has failed and will retransmit only the sections that
are functional. Thus if T-ring section 409 fails, only
signals received by sections 411, 413 and 415 will be
retransmitted.
If wire 309 is damaged and unable to carry a signal
along the length of the drill pipe, the other three 311,
313 and 315 of the four wires will be able to carry the
signal and received by receiver antennae 411a, 413a and
415a. The signal will then be passed between all four
processor units 420 and transmitted through all four
transmitter antennae 409b, 4llb, 413b and 415b and
received by all four wires (conductors) in the pin end of
the adjacent drill pipe. In the same way, two or three
wires may fail in each drill pipe section whilst still
maintaining data integrity through the entire drill
string.
A transmission line using number 26 enameled wire,
0.4mm (0.0159") diameter copper, enamel coated (standard
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magnet wire) can be utilized for the transmission path.
The wires are preferably placed a few mils apart, side-
by-side, to act as an RF line. The wires can be coated
into position very loosely twisted the wires together or
laid out side-by-side. In a test, at 730 MHz the loss in
a 3.15m (10' 4") section is about 6 dB for this
configuration of the communication path. The wires were
tested in a balanced configuration, driven and loaded by
a 5052 coaxial system. In the test no baluns or any form
of matching was used. The wire ends were soldered to some
SMA coax connectors. The VSWR in a 5052 system and the
transmission losses Were measured. Squeezing and
manipulating the wire pair at various points where there
might have been gaps resulted in a return loss of about
20dB at which time the transmission loss was minimized
and was about 6 dB for the section. The same length of
RG-174 was measured at 3.1 to 3.2dB loss at 730 MHz using
the same connectors. Building RF transmission lines with
parallel ribbon conductors, which could be wider than the
#26 wires, form an assembly thin enough to fit desired
maximum overall thickness of less than lmm (40 mils) for
the coating inside of a drill pipe section.
Figure 10 is a schematic illustration of an
alternative embodiment wherein a micro strip line is
provided inside of a drill pipe section as a transmission
path . Figure 11 is a cross section of a preferred micro
strip line provided as a communication path inside of a
drill pipe. Figure 12 is a table illustrating
characteristic impedance for a full-section strip
transmission line and line widths. Figure 13 a.s an
illustration of a quarter wave impedance matching
section. Turning now to Figure 10, a preferred micro
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strip line communication path is illustrated.
Alternatively dielectric-supported strip lines such as
parallel ribbon conductors, can be used, thereby
maximizing the conductor widths while keeping within the
desired overall thickness limitations of the
approximately 0.635mm (0.025") coating thickness. Figure
illustrates a thin, full-section micro strip line
transmission line or communication path inside of a drill
pipe section to maintain 5052 impedance levels with
10 convenient line widths. A thin, full-section micro strip
line as shown in Figure 10 works well. As shown in
Figure 10, er is Er, the relative dielectric constant, of
the material inside of the full-section strip line
transmission line assembly. The edges of the assembly are
Z5 preferably rounded as shown in the Figure 11 diagram
below, as long as the width of the ground plane portions
is 3 or 4 times the width of the centre conductor, w.
Preferably, the centre conductor width is maximized in
order to minimize losses, since the centre conduct is
where most of the losses manifest. The wider the centre
conductor, the lower the losses in the centre conductor.
The characteristic impedance, Zo, of the micro strip line
transmission path shown in Figure 10 and 11 decreases
with increasing width, however, so there is a
compromising process.
Preferably, a foil package is fabricated with a
center conductor suspended in a material with a
dielectric constant, with Er, as low as possible having a
low loss tangent. TFE or Teflon is a suitable material,
with an Er of 2.1 and dissipation factor between 0.0003
and 0.0004, although Teflon filled with hollow silica
macro-spheres or a similar material is preferred, with an
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Er of 1.2 and substantially the same dissipation factor.
The table shown in Figure 12 shows some representative
characteristic impedance values for Teflon in various
center conductor widths "w" 1010 and thickness "t" 1012
and material thickness "b" 1014 and coating thickness
1002.
In the full-section strip line, RF current flows on
both sides of the center strip 1108 so the area to
support current is comparable to a coaxial line with a
round center conductor of a diameter substantially less
than the width w. The predicted losses for the micro
strip lines shown in Figure 10 and 11 above using TFE
dielectric are less than for miniature coaxial lines. It
is expected that less than the 8 dB per 9.1m (30 feet)
will be typical for a preferred embodiment. The
preferred full-section strip line transmission lines
should be more efficient than the RG-174 coaxial cable.
The circumference of the # 26 centre conductor in the RG-
174 coax is about 0.127mm (0.050") whereas the effective
width of the 25 ohm line below (third up from the bottom)
is l.3mm (0.051") and the solid, smooth ground planes
should be slightly better than the single-thickness braid
used on the coax outside conductor. Also, the dielectric
material in the strip line is preferably better than the
polyethylene used in the coax.
As shown in Figure 12, W/b and Zo data a.s from the
Microwave Engineers' Handbook, Vol 1, Artech House. The
last column in the chart is the total thickness of the
coatings and the transmission line assembly.
As shown in Figure 13, allowing the impedance, Zo of
the strip line 1000 to go down to 25 ohms allows the
center conductor to become wider to exhibit lower losses.
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A quarter wavelength (about l0cm) impedance matching
section 1302, as shown below in Figure 13, matches (step-
up) the line to the effective impedance (resistance at
resonance) of the coupling loops 1304 at the passive ends
of the pipe length. The amplifier assembly is used for
matching to the intermediate loops. In this way, most of
the line length (9m (29 feet)) can be lower loss.
As shown in Figure 12, a preferred embodiment
comprises strips of 0.05mm (0.002") copper foil about
20 0.635mm (0.025") wide. Standard 1 oz. Cu PCB foil is
0.0356 (0.0014") thick and 2 oz. Cu clad is 0.0711mm
(0.0028") thick. Skin depth is about 0.006mm (1~ mil)
enabling use of 1 oz. Cu stock. The Cu stock is
preferably glued to a strip of Teflon and a line
fabricated. Since we can measure the impedance
characteristics accurately with the UNR network analyzer,
we can separate matching losses from hR losses.
Therefore, a 3.05m (10 feet) length should be enough to
determine possibilities.
The dielectric material 1116 in the transmission
line holds the centre conductor strip a.n place between
the ground planes and preferably, the dielectric material
does not have to uniformly surround the centre strip
1118. All dimensions are non-critical, with 10~
tolerances. Once the preferred embodiment is manufactured
it can be characterized and used however it comes out.
The preferred communication path assembly then stays
relatively constant. The dielectric preferably comprises
two separate strips of Teflon-like material, one below
the center strip 1118 and one above 1114, and the whole
positioned in between the outer conductors 1104 and 1106.
The outer conductors 1104 and 1106, or ground planes
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are preferably one piece of copper foil, wrapped around
the insides, folded and crimped, or cold-welded, on the
open side to form a surrounding structure enveloping the
dielectric material 1116 and centre conductor 1108.
Alternatively, one of the dielectric strips could be
extruded with a 0.05mm x 0.0635mm (0.002" x 0.025")
channel extruded into it to hold the centre strip.
Alternatively, the dielectric strip can be run through a
machine to cut a grove along its length. There numerous
manufacturing techniques to fabricate the preferred
communication path assembly.
The invention provides a drill pipe communication
path comprising: a drill pipe section having a conducting
member located adjacent an interior surface of the drill
pipe; and a coupling for connecting a plurality of the
drill pipe sections so that data can be transferred,from
one end of the drill pipe section to the next.
Preferably, the apparatus further comprises a thin
coating for covering the conducting member.
Advantageously, the conducting member further comprises a
micro strip line. Preferably, the coupling comprises a
repeater-amplifier. Advantageously, an inductive
coupling, an acoustic coupling, or a digital repeater may
be used.
The invention also provides a method for
manufacturing a drill pipe communication path comprising:
positioning a conductive member adjacent an interior
surface of a drill pipe section; and connecting a
plurality of drill pipe sections so that data can be
transferred along .the communication path from one end of
the drill pipe section to the next. Preferably, the
method further comprises covering the conductive member
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with a thin coating. Advantageously, the method further
comprises depositing a micro strip line inside of the
drill pipe.
While the foregoing disclosure is directed to the
preferred embodiments of the invention various
modifications will be apparent to those skilled in the
art. It is intended that all variations within the scope
and spirit of the appended claims be embraced by the
foregoing disclosure. Examples of the more important
features of the invention have been summarized rather
broadly in order that the detailed description thereof
that follows may be better understood, and in order that
the contributions to the art may be appreciated. There
are, of course, additional features of the invention that
will be described hereinafter and which will form the
subject of the claims appended hereto.
