Government Interest
[0001] This invention was made with government support under Contract No. DE-FC26-97FT343656.
Related Applications
[0002] This application is a continuation-in-part of U.S. Patent Application Serial no.
10/612,255 entitled Transmission Element for Downhole Drilling Components filed July
2, 2003 which claims priority to U.S. Patent Application Serial No. 10/453,076 entitled
Transducer for Downhole Drilling Components filed June 3, 2003.
BACKGROUND OF THE INVENTION
[0003] This invention relates to oil and gas drilling, and more particularly to apparatus
and methods for reliably transmitting information to the surface from downhole drilling
components.
[0004] For several decades, engineers have worked to develop apparatus and methods to effectively
transmit information from components located downhole on oil and gas drilling strings
to the ground's surface. Part of the difficulty lies in the development of reliable
apparatus and methods for transmitting information from one drill string component
to another, such as between sections of drill pipe. The goal is to provide reliable
information transmission between downhole components stretching thousands of feet
beneath the earth's surface, while withstanding hostile wear and tear of subterranean
conditions.
[0005] In an effort to provide solutions to this problem, engineers have developed a technology
known as mud pulse telemetry. Rather than using electrical connections, mud pulse
telemetry transmits information in the form of pressure pulses through fluids circulating
through a well bore. However, data rates of mud pulse telemetry are very slow compared
to data bandwidths needed to provide real-time data from downhole components.
[0006] For example, mud pulse telemetry systems often operate at data rates less than 10
bits per second. At this rate, data resolution is so poor that a driller is unable
to make crucial decisions in real time. Since drilling equipment is often rented and
very expensive, even slight mistakes incur substantial expense. Part of the expense
can be attributed to time-consuming operations that are required to retrieve downhole
data or to verify low-resolution data transmitted to the surface by mud pulse telemetry.
Often, drilling or other procedures are halted while crucial data is gathered.
[0007] In an effort to overcome limitations imposed by mud pulse telemetry systems, reliable
connections are needed to transmit information between components in a drill string.
For example, since direct electrical connections between drill string components may
be impractical and unreliable, other methods are needed to bridge the gap between
drill string components.
[0008] Various factors or problems may make data transmission unreliable. For example, dirt,
rocks, mud, fluids, or other substances present when drilling may interfere with signals
transmitted between components in a drill string. In other instances, gaps present
between mating surfaces of drill string components may adversely affect the transmission
of data therebetween.
[0009] Moreover, the harsh working environment of drill string components may cause damage
to data transmission elements. Furthermore, since many drill string components are
located beneath the surface of the ground, replacing or servicing data transmission
components may be costly, impractical, or impossible. Thus, robust and environmentally-hardened
data transmission components are needed to transmit information between drill string
components.
SUMMARY OF THE INVENTION
[0010] In view of the foregoing, it is a primary object of the present invention to provide
robust transmission elements for transmitting information between downhole tools,
such as sections of drill pipe, in the presence of hostile environmental conditions,
such as heat, dirt, rocks, mud, fluids, lubricants, and the like. It is a further
object of the invention to maintain reliable connectivity between transmission elements
to provide an uninterrupted flow of information between drill string components.
[0011] Consistent with the foregoing objects, and in accordance with the invention as embodied
and broadly described herein, an apparatus for transmitting data between downhole
tools is disclosed in one embodiment of the present invention as including an annular
core constructed of a magnetically-conductive material. At least one conductor, electrically
isolated from the annular core, is coiled around the annular core. An annular housing
constructed of an electrically conductive material is used to partially enclose the
annular core and the conductive coil. The annular housing is shaped to reside within
an annular recess formed into a surface of a downhole tool, and is electrically insulated
from the surface. A biasing member is used to cause a bias between the annular housing
and the annular recess, urging the annular housing in a direction substantially perpendicular
to the surface.
[0012] In selected embodiments, a retention mechanism may be provided to retain the annular
housing within the annular recess. In addition, the biasing member may be a metal
spring, an elastomeric material, or an elastomeric-like material.
[0013] In certain embodiments, the annular core may be characterized by an elongated cross-section.
The annular core may have a cross-section characterized by a height at least twice
that of its width.
[0014] In another aspect of the invention, a transmission element for transmitting information
between downhole tools is disclosed in one embodiment of the present invention as
including an annular core constructed of a magnetically conductive material. At least
one conductor, electrically isolated from the annular core, is coiled around the annular
core. An annular housing constructed of an electrically conductive material is used
to partially enclose the annular core and the conductive coil. The annular housing
is shaped to reside within an annular recess formed into a surface of a downhole tool,
and is electrically insulated from the surface. Means for effecting a bias between
the annular housing and the annular recess is provided.
[0015] In selected embodiments, means for effecting a bias between the annular housing and
the annular recess is provided by radial tension between surfaces of the annular housing
and the annular recess. This tension may be due to tension along the outside diameters,
the inside diameters, or a combination thereof, of the annular housing and the annular
recess.
[0016] In another aspect of the present invention, an apparatus for transmitting information
between downhole tools located on a drill string includes a transmission element,
having a contact, mounted to the end of a downhole tool. Another transmission element,
having another contact, is mounted to the end of another downhole tool connectable
to the first downhole tool. These contacts are configured to physically contact one
another upon connecting the first and second downhole tools. An isolation mechanism
is provided to isolate the contacts from their surrounding environment when they come
into contact with one another.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] The foregoing and other features of the present invention will become more fully
apparent from the following description, taken in conjunction with the accompanying
drawings. Understanding that these drawings depict only typical embodiments in accordance
with the invention and are, therefore, not to be considered limiting of its scope,
the invention will be described with additional specificity and detail through use
of the accompanying drawings in which:
Figure 1 is a perspective view illustrating one embodiment of transmission elements
installed in the box and pin ends of drill pipe sections to transmit and receive information
along a drill string;
Figure 2 is a perspective view illustrating one embodiment of the interconnection
and interaction between transmission elements;
Figure 3 is a perspective cross-sectional view illustrating various features of one
embodiment of an improved transmission element in accordance with the invention;
Figure 4 is a perspective cross-sectional view illustrating one embodiment of a multi-coil
or multi-strand conductor within a transmission element, and various locking shoulders
used to retain the MCEI segments within the annular housing;
Figure 5 is a perspective cross-sectional view illustrating one embodiment of a single
conductor or coil used within the transmission element;
Figure 6 is a perspective cross-sectional view illustrating one embodiment of a single
conductor or coil surrounded by an electrically insulating material used within the
transmission element;
Figure 7 is a perspective cross-sectional view illustrating another embodiment of
a transmission element having a flat or planar area formed on the conductor in accordance
with the invention;
Figure 8 is a perspective cross-sectional view illustrating one embodiment of a transmission
element having various biasing members to urge components of the transmission element
into desired positions;
Figure 9 is a perspective cross-sectional view illustrating one embodiment of a transmission
element having a shelf or ledge formed in the annular housing to accurately position
the transmission element with respect to a substrate;
Figure 10 is a perspective cross-sectional view illustrating one embodiment of a transmission
element having an elastomeric or elastomeric-like material to urge the components
of the transmission element into desired positions;
Figure 11 is a perspective cross-sectional view illustrating on embodiment of an annular
housing capable of retaining MCEI segments in substantially fixed positions within
the annular housing;
Figure 12 is a perspective view illustrating on embodiment of a transmission element
having an electrical conductor coiled around an annular magnetically conductive core;
Figure 13 is a perspective cross-sectional view illustrating one embodiment of the
transmission element of Figure 12 installed into an annular recess provided in the
pin end of a downhole tool;
Figure 14 is a cross-sectional view illustrating one embodiment of two transmission
elements coupled together for signal transmission therebetween;
Figure 15 is a cross-sectional view illustrating one embodiment of a transmission
element having an annular conductive housing layered with an insulating material;
Figure 16 is a cross-sectional view illustrating one embodiment of an elongated transmission
element;
Figure 17 is a cross-sectional view illustrating one alternative embodiment to the
transmission element illustrated in Figure 16;
Figure 18 is a cross-sectional view illustrating one embodiment of a transmission
element retained by locking shoulders formed into the transmission element and a substrate;
Figure 19 is a cross-sectional view illustrating one embodiment of two transmission
elements installed into the pin end and box end of respective downhole tools;
Figure 20 is a cross-sectional view illustrating one embodiment of two transmission
elements in the pin end and box end of two downhole tools connected together;
Figure 21 is a cross-sectional view illustrating one embodiment of transmission elements
installed into longitudinal surfaces of connected downhole tools;
Figure 22 is a cross-sectional view illustrating one embodiment of a biased or spring-loaded
transmission element having electrical contacts and means for isolating the contacts
from the surrounding environment;
Figure 23 is a cross-sectional view illustrating another embodiment of transmission
elements having electrical contacts residing in recesses located on longitudinal surfaces
of connected downhole tools;
Figure 24 is a perspective cross-sectional view illustrating one embodiment of a transmission
element having an annular electrical contact;
Figures 25A-C are cross-sectional views illustrating various positions of one embodiment
of a transmission element having electrical contacts and means for isolating the contacts;
Figures 26A-C are cross-sectional views illustrating various positions of another
embodiment of a transmission element having electrical contacts and means for isolating
the contacts; and
Figure 27 is a cross-sectional view illustrating one embodiment of a self-cleaning
contact that may be used for reliable electrical connections.
DETAILED DESCRIPTION OF THE INVENTION
[0018] It will be readily understood that the components of the present invention, as generally
described and illustrated in the Figures herein, could be arranged and designed in
a wide variety of different configurations. Thus, the following more detailed description
of embodiments of apparatus and methods of the present invention, as represented in
the Figures, is not intended to limit the scope of the invention, as claimed, but
is merely representative of various selected embodiments of the invention.
[0019] The illustrated embodiments of the invention will be best understood by reference
to the drawings, wherein like parts are designated by like numerals throughout. Those
of ordinary skill in the art will, of course, appreciate that various modifications
to the apparatus and methods described herein may easily be made without departing
from the essential characteristics of the invention, as described in connection with
the Figures. Thus, the following description of the Figures is intended only by way
of example, and simply illustrates certain selected embodiments consistent with the
invention as claimed herein.
[0020] In an effort to overcome limitations imposed by mud pulse telemetry systems, reliable
connections are needed to transmit information between components in a drill string.
For example, since direct electrical connections between drill string components may
be impractical and unreliable due to dirt, mud, rocks, air gaps, and the like between
components, converting electrical signals to magnetic fields for later conversion
back to electrical signals is suggested for transmitting information between drill
string components.
[0021] Like a transformer, current traveling through a first conductive coil, located on
a first drill string component, may be converted to a magnetic field. The magnetic
field may then be detected by a second conductive coil located on a second drill string
component where it may be converted back into an electrical signal mirroring the first
electrical signal. A core material, such as a ferrite, may be used to channel magnetic
fields in a desired direction to prevent power loss. However, past attempts to use
this "transformer" approach have been largely unsuccessful due to a number of reasons.
[0022] For example, power loss may be a significant problem. Due to the nature of the problem,
signals must be transmitted from one pipe section, or downhole tool, to another. Thus,
air or other gaps are present between the core material of transmission elements.
This may incur significant energy loss, since the permeability of ferrite, and other
similar materials, may be far greater than air, lubricants, pipe sealants, or other
materials. Thus, apparatus and methods are needed to minimize power loss in order
to effectively transmit and receive data.
[0023] Referring to Figure 1, drill pipes 10a, 10b, or other downhole tools 10a, 10b, may
include a pin end 12 and a box end 14 to connect drill pipes 10a, 10b or other components
10a, 10b together. In certain embodiments, a pin end 12 may include an external threaded
portion to engage an internal threaded portion of the box end 14. When threading a
pin end 12 into a corresponding box end 14, various shoulders may engage one another
to provide structural support to components connected in a drill string.
[0024] For example, a pin end 12 may include a primary shoulder 16 and a secondary shoulder
18. Likewise, the box end 14 may include a corresponding primary shoulder 20 and secondary
shoulder 22. A primary shoulder 16, 20 may be labeled as such to indicate that a primary
shoulder 16, 20 provides the majority of the structural support to a drill pipe 10
or downhole component 10. Nevertheless, a secondary shoulder 18 may also engage a
corresponding secondary shoulder 22 in the box end 14, providing additional support
or strength to drill pipes 10 or components 10 connected in series.
[0025] As was previously discussed, apparatus and methods are needed to transmit information
along a string of connected drill pipes 10 or other components 10. As such, one major
issue is the transmission of information across joints where a pin end 12 connects
to a box end 14. In selected embodiments, a transmission element 24a may be mounted
proximate a mating surface 18 or shoulder 18 on a pin end 12 to communicate information
to another transmission element 24b located on a mating surface 22 or shoulder 22
of the box end 14. Cables 26a, 26b, or other transmission media 26, may be operably
connected to the transmission elements 24a, 24b to transmit information therefrom
along components 10a, 10b.
[0026] In certain embodiments, an annular recess may be provided in the secondary shoulder
18 of the pin end 12 and in the secondary shoulder 22 of the box end 14 to house each
of the transmission elements 24a, 24b. The transmission elements 24a, 24b may have
an annular shape and be mounted around the radius of the drill pipe 10. Since a secondary
shoulder 18 may contact or come very close to a secondary shoulder 22 of a box end
14, a transmission element 24a may sit substantially flush with a secondary shoulder
18 on a pin end 12. Likewise, a transmission element 24b may sit substantially flush
with a surface of a secondary shoulder 22 of a box end 14.
[0027] In selected embodiments, a transmission element 24a may be coupled to a corresponding
transmission element 24b by having direct electrical contact therewith. In other embodiments,
the transmission element 24a may convert an electrical signal to a magnetic field
or magnetic current. A corresponding transmission element 24b, located proximate the
transmission element 24a, may detect the magnetic field or current. The magnetic field
may induce an electrical current into the transmission element 24b. This electrical
current may then be transmitted from the transmission element 24b by way of an electrical
cable 26b along the drill pipe 10 or downhole component 10.
[0028] As was previously stated, a downhole drilling environment may adversely affect communication
between transmission elements 24a, 24b located on successive drill string components
10. Materials such as dirt, mud, rocks, lubricants, or other fluids, may inadvertently
interfere with the contact or coupling between transmission elements 24a, 24b. In
other embodiments, gaps present between a secondary shoulder 18 on a pin end 12 and
a secondary shoulder 22 on a box end 14, due to variations in component tolerances,
may interfere with communication between transmission elements 24a, 24b. Thus, apparatus
and methods are needed to reliably overcome these as well as other obstacles.
[0029] Referring to Figure 2, in selected embodiments, a transmission element assembly 33
may include a first transmission element 24a mounted in the pin end 12 of a drill
pipe 10 or other tool 10, and a second transmission element 24b mounted in the box
end 14 of a drill pipe 10 or other tool 10. Each of these transmission elements 24a,
24b may be operably connected by a cable 26a, such as electrical wires, coaxial cable,
optical fiber, or like transmission media. Each of the transmission elements 24 may
include an exterior annular housing 28. The annular housing 28 may function to protect
and retain components or elements within the transmission element 24. The annular
housing 28 may have an exterior surface shaped to conform to a recess milled, formed,
or otherwise provided in the pin 12 or box end 14 of a drill pipe 10, or other downhole
component 10.
[0030] In selected embodiments, the annular housing 28 may be surfaced to reduce or eliminate
rotation of the transmission elements 24 within their respective recesses. For example,
anti-rotation mechanisms, such as barbs or other surface features formed on the exterior
of the annular housing 28 may serve to reduce or eliminate rotation.
[0031] As is illustrated in Figure 2, a transmission element 24b located on a first downhole
tool 10 may communicate with a transmission element 24c located on a second downhole
tool 10. Electrical current transmitted through a coil 32 in a first transmission
element 24b may create a magnetic field circulating around the conductor 32. A second
transmission element 24c may be positioned proximate the first transmission element
24b such that the magnetic field is detected by a coil 32 in the transmission element
24c.
[0032] In accordance with the laws of electromagnetics, a magnetic field circulated through
an electrically conductive loop induces an electrical current in the loop. Thus, an
electrical signal transmitted to a first transmission element 24b may be replicated
by a second transmission element 24c. Nevertheless, a certain amount of signal loss
occurs at the coupling of the transmission element 24b, 24c. For example, signal loss
may be caused by air or other gaps present between the transmission elements 24b,
24c, or by the reluctance of selected magnetic materials. Thus, apparatus and methods
are needed to reduce, as much as possible, signal loss that occurs between transmission
elements 24b, 24c.
[0033] Referring to Figure 3, a perspective cross-sectional view of one embodiment of a
transmission element 24 is illustrated. In selected embodiments, a transmission element
24 may include an annular housing 28, an electrical conductor 32, and a magnetically-conducting,
electrically-insulating material 34 separating the conductor 32 from the housing 28.
[0034] The MCEI material 34 may prevent electrical shorting between the electrical conductor
32 and the housing 28. In addition, the MCEI material 34 contains and channels magnetic
flux emanating from the electrical conductor 32 in a desired direction. In order to
prevent signal or power loss, magnetic flux contained by the MCEI material 34 may
be directed or channeled to a corresponding transmission element 24 located on a connected
downhole tool 10.
[0035] The MCEI material 34 may be constructed of any material having suitable magnetically-conductive
and electrically-insulating properties. For example, in selected embodiments, certain
types of metallic oxide materials such as ferrites, may provide desired characteristics.
Ferrites may include many of the characteristics of ceramic materials. Ferrite materials
may be mixed, pre-fired, crushed or milled, and shaped or pressed into a hard, typically
brittle state. Selected types of ferrite may be more preferable for use in the present
invention, since various types operate better at higher frequencies.
[0036] Since ferrites or other magnetic materials may be quite brittle, using an MCEI material
34 that is a single piece may be impractical, unreliable, or susceptible to cracking
or breaking. Thus, in selected embodiments, the MCEI material 34 may be provided in
various segments 34a-c. Using a segmented MCEI material 34a-c may relieve tension
that might otherwise exist in a single piece of ferrite. If the segments 34 are positioned
sufficiently close to one another within the annular housing 28, signal or power loss
between joints or gaps present between the segments 34a-c may be minimized.
[0037] The annular housing 28, MCEI material 34, and conductor 32 may be shaped and aligned
to provide a relatively flat face 35 for interfacing with another transmission element
24. Nevertheless, a totally flat face 35 is not required. In selected embodiments,
a filler material 38 or insulator 38 may be used to fill gaps or volume present between
the conductor 32 and the MCEI material 34. In addition, the filler material 38 may
be used to retain the MCEI segments 34a-c, the conductor 32, or other components within
the annular housing 28.
[0038] In selected embodiments, the filler material 38 may be any suitable polymer material
such as Halar, or materials such as silicone, epoxies, and the like. The filler material
38 may have desired electrical and magnetic characteristics, and be able to withstand
the temperature, stress, and abrasive characteristic of a downhole environment. In
selected embodiments, the filler material 38 may be surfaced to form to a substantially
planer surface 35 of the transmission element 24.
[0039] In selected embodiments, the annular housing 28 may include various ridges 40 or
other surface characteristics to enable the annular housing 28 to be press fit and
retained within an annular recess. These surface characteristics 40 may be produced
by stamping, forging, or the like, the surface of the housing 28. In selected embodiments,
the annular housing 28 may be formed to retain the MCEI material 34, the conductor
32, any filler material 38, and the like. For example, one or several locking shoulders
36 may be provided or formed in the walls of the annular housing 28. The locking shoulders
36 may allow insertion of the MCEI material 34 into the annular housing 28, while
preventing the release therefrom.
[0040] Referring to Figure 4, in selected embodiments, the electrical conductor 32 may include
multiple strands 32a-c, or multiple coils 32a-c, coiled around the circumference of
the annular housing 28. In selected embodiments, multiple coils 32a-c may enable or
improve the conversion of electrical current to a magnetic field. The coils 32a-c,
or loops 32a-c, may be insulated separately or may be encased together by an insulation
38 or filling material 38.
[0041] Referring to Figure 5, in another embodiment, the transmission element 24 may include
a single coil 32, or loop 32. The single loop 32 may occupy substantially the entire
volume within the MCEI material 34. An insulated conductor 32 may simply provide a
rounded surface for interface with another transmission element 24.
[0042] Referring to Figure 6, in another embodiment, the conductor 32 may be much smaller
and may or may not be surrounded by a filler material 38. The filler material 38 may
be leveled off to provide a planar or substantially flat surface 44 for interfacing
with another transmission element 24. In certain cases, a larger electrical conductor
32 may provide better performance with respect to the conversion of electrical energy
to magnetic energy, and the conversion of magnetic energy back to electrical energy.
[0043] Referring to Figure 7, in selected embodiments, a transmission element 24 may have
a rounded shape. The annular housing 28, the MCEI material 34, and the conductor 32
may be configured to interlock with one another. For example, the annular housing
28 may be formed to include one or more shoulders 48a, 48b that may interlock with
and retain the MCEI material 34.
[0044] In certain embodiments, a biasing member 50 such as a spring 50 or other spring-like
element 50 may function to keep the MCEI material 34 loaded and pressed against the
shoulders 48a, 48b of the annular housing 28. The shoulders 48a, 48b may be dimensioned
to enable the MCEI material 34 to be inserted into the annular housing 28, while preventing
the release thereof. In a similar manner, the conductor 32 may be configured to engage
shoulders 49a, 49b formed into the MCEI material 34. In the illustrated embodiment,
the conductor 32 has a substantially flat or planar surface 44. This may improve the
coupling, or power transfer to another transmission element 24.
[0045] Referring to Figure 8, in another embodiment, locking or retaining shoulders 52a,
52b may be milled, formed, or otherwise provided in a substrate material 54, such
as in the primary or secondary shoulders 16, 18, 20, 22 of drill pipes 10 or downhole
tools 10. Likewise, corresponding shoulders may be formed in the annular housing 28
to engage the shoulders 52a, 52b.
[0046] A biasing member, such as a spring 50a, or spring-like member 50a, may be inserted
between the annular housing 28 and the MCEI material 34. The biasing members 50a,
50b may enable the transmission element 24 to be inserted a select distance into the
annular recess of the substrate 54. Once inserted, the biasing members 50a, 50b may
serve to keep the annular housing 28 and the MCEI material 34 pressed against the
shoulders 48a, 48b, 52a, 52b.
[0047] In addition, shoulders 48a, 48b, 52a, 52b may provide precise alignment of the annular
housing 28, MCEI material 34, and conductor 32 with respect to the surface of the
substrate 54. Precise alignment may be desirable to provide consistent separation
between transmission elements 24 communicating with one another. Consistent separation
between transmission elements 24 may reduce reflections and corresponding power loss
when signals are transmitted from one transmission element 24 to another 24.
[0048] Referring to Figure 9, in selected embodiments, a transmission element 24 may include
an alignment surface 58 machined, cast, or otherwise provided in the exterior surface
of the annular housing 28. The alignment surface 58 may engage a similar surface milled
or formed into an annular recess of a substrate 54. This may enable precise alignment
of the annular housing 28 and other components 32, 34 with the surface of a substrate
54.
[0049] In certain embodiments, the conductor 32 may be provided with grooves 54a, 54b or
shoulders 54a, 54b that may engage corresponding shoulders milled or formed into the
MCEI material 34. This may enable a surface 44 of the conductor 32 to be level or
flush with the surface of the MCEI material 34 and the annular housing 28. In some
cases, such a configuration may enable direct physical contact of conductors 32 in
the transmission elements 24 when they are coupled together. This may enhance the
coupling effect of the transmission elements 24 and enable more efficient transfer
of energy therebetween. As is illustrated in Figure 9, lower shoulders 56a, 56b formed
into the annular housing 28 and the MCEI material 34 may provide a substantially fixed
relationship between the annular housing 28 and the MCEI material 34.
[0050] Referring to Figure 10, in selected embodiments, a biasing member 50 composed of
an elastomeric or elastomeric-like material may be inserted between components such
as the annular housing 28 and the MCEI material 34. As was previously described with
respect to Figure 7, the biasing member 50 may keep the MCEI material 34 pressed up
against shoulders 48a, 48b of the annular housing 28 to provide precise alignment
of the MCEI material 34 with the annular housing 28.
[0051] Referring to Figure 11, in selected embodiments, the annular housing 28 may be formed,
stamped, milled, or the like, as needed, to maintain alignment or positioning of various
components within the annular housing 28. For example, various retention areas 60
may be formed into the annular housing 28 to provide consistent spacing of MCEI segments
34a-c. The retention areas 60 may simply be stamped or hollowed areas within the annular
housing 28, or they may be cutout completely from the surface thereof.
[0052] Likewise, one or multiple ridges 62 or other surface features 62 may be provided
to retain the annular housing 28 in an annular recess when the annular housing 28
is press-fit or inserted into the recess. The annular housing 28 may also include
various shoulders 64a, 64b that may engage corresponding shoulders milled or formed
into the annular recess to provide precise alignment therewith and to provide a consistent
relationship between the surfaces of the transmission element 24 and the substrate
54.
[0053] Referring to Figure 12, in selected embodiments a transmission element 24 may include
an electrical conductor 72 coiled around a magnetically conductive annular core 70.
One end of the coil 72 may be connected to a conductor 26 or cable 26 for routing
along a downhole tool 10. The other end of the conductor 72 may be connected to a
return path or ground.
[0054] When a voltage is applied across the ends of the coil 72, an electrical begins to
flows through the coil 72. The electrical current induces a magnetic field through
the center of the coil. This magnetic field may flow through and be substantially
retained with the annular core 70. As in the other transmission elements 24 previously
described, an annular housing forming an open channel may be used to partially enclose
the coil 72 and the annular core 70. Likewise, an insulator 74 may cover a cable 26
or conductor 26 connected to the coil 72.
[0055] Referring to Figure 13, for example, a transmission element 24 having a configuration
like that described in Figure 12 may reside within an annular recess formed or milled
into a secondary shoulder 18 of a downhole tool 10. As illustrated, the transmission
element 24 includes a conductive coil 72 coiled around a magnetically conductive annular
core 70. An annular housing 28 may include an exterior insulating layer 76. The insulating
layer 76 may serve to isolate or insulate the inner conductive housing 28 from the
secondary shoulder 18. The reason for this will be explained in further detail in
the description of Figure 14.
[0056] Referring to Figure 14, a cross-sectional view of a pair of transmission elements
24a, 24b mated together is illustrated. In order to transmit an electrical signal
from a first transmission element 24a to another transmission element 24b, an electrical
current is transmitted through the conductive coil 72a. This current induces a magnetic
field or magnetic flux in the core material 70a that flows in a direction perpendicular
to the cross-section 70a, the direction being dependent on the direction current travels
through the coil 72a.
[0057] When a magnetic field or magnetic flux is induced in the core 70a, the magnetic flux
moves through the conductive loop formed by the conductive annular housing 28a and
annular housing 28b. A changing magnetic field through this loop 28a, 28b induces
an electrical current 80 to travel around the loop 28a, 28b. In turn, this current
80 causes a magnetic flux to travel through the core material 70b perpendicular to
the cross-section 70b, the direction depending on the direction electrical current
travels through the loop 28a, 28b.
[0058] A changing magnetic flux traveling through the core 70b, induces an electrical current
in the conductive coil 72b. Thus, electrical current flowing through the coil 72a
may induce an electrical current to flow through the coil 72b, thereby providing signal
transmission from one transmission element 24a to another 24b. In selected embodiments,
the core material 70a, 70b may be coated with an insulator 78a, 78b to prevent electrical
contact between the coil 72 and the core 70. In selected embodiments, the coil 72
may be coated with an insulating material to prevent shorting with itself, the annular
core 70, and the conductive housing 28.
[0059] Referring to Figure 15, in selected embodiments, a conductive annular housing 28
may include an insulating layer 76 to prevent electrical contact of the annular housing
with the recess. In selected embodiments, the annular housing 28 may include flanges
82a, 82b to provide additional contact surface. The flanges 82a, 82b may also function
to accurately align the annular housing 28 with the insulating layer 76.
[0060] Referring to Figure 16, in selected embodiments, the conductive coil 72 and annular
core 70 may be elongated. Thus, the core 70 and coil 72 may have a relatively narrow
width 86 compared to height 84. Since a primary or secondary shoulder of a downhole
tool 10 may be quite narrow, this narrow configuration may permit the transmission
element 24 to reside within a narrower annular groove formed or milled into the shoulder
18. This may also reduce weakening of the shoulder 18 caused by a wider recess or
groove.
[0061] In addition, an elongated configuration like that described in Figure 16 may also
improve the power coupling properties of the transmission element 24. This may be
due to the increased cross-sectional area of the magnetically conductive core 70.
A larger cross-section may cause an increase in the magnetic flux passing therethrough.
In certain embodiments, it may be desirable that the height 84 is at least twice the
width 86. In selected embodiments, the annular housing 28 may have a rounded contour
as illustrated. The advantage of this will be explained in the description of Figure
18.
[0062] Referring to Figure 17, in other embodiments, the annular housing 28 containing the
conductive coil 72 and annular core 70 may have relatively parallel sides 88a, 88b.
This may enable the housing 28 to be press fit into an annular recess having sides
conforming thereto.
[0063] Referring to Figure 18, in selected embodiments, the annular housing 28 or insulator
76 may be formed to include a shoulder 96 that may interlock with a corresponding
shoulder 98 provided in a primary or secondary shoulder of a drill tool 10. The shoulder
96 may enable the housing to slip past the shoulder 98 when inserting the transmission
element 24 into the recess 90. However, once interlocked, the transmission element
24 may be retained within the recess 90
[0064] In selected embodiments, a wall of the annular housing 28 may form an angle 94 offset
with respect to a direction perpendicular to the shoulder surface 18. This angle 94
may urge the transmission element 24 in an upward direction 100, thereby giving the
transmission element 24 a bias with respect to the secondary shoulder 18. Designing
a transmission element 24 having a radius that is slightly smaller or larger than
that of the annular recess 90, into which it is inserted, may produce the bias.
[0065] Thus, after the retaining shoulder 96 engages the corresponding shoulder 98 of the
secondary shoulder 18, the transmission element 24 may be urged in a direction 100
until the shoulders 96, 98 engage. A top edge of the annular housing 28 and insulator
76 may actually sit above the surface of the secondary shoulder 18. When the transmission
element 24 comes into contact with another transmission element 24 located on another
tool 10, the transmission element 24 may be urged downward into the recess 90. The
upward bias force 100 may maintain reliable connection between the annular housing
28 of the transmission element 24 and a corresponding annular housing 28 located on
another transmission element 24, thereby providing reliable electrical contact between
the two.
[0066] Referring to Figure 19, for example, in selected embodiments, transmission elements
24a, 24b may be inserted into annular recesses 90a, 90b provided in the secondary
shoulders 18, 22 of a pin end and box end of downhole tools 10. In selected embodiments,
the recesses 90a, 90b may open up into the central bore 104 of the downhole tool 10.
This may reduce the weakening effect that the recesses 90a, 90b might have on the
secondary shoulders 18, 22 if they were located closer to the center of the shoulders
18, 22.
[0067] As was discussed with respect to Figure 18, angled sides of the recesses 90a, 90b
may provide a spring-force urging the transmission elements 24a, 24b out of their
respective recesses 90a, 90b. Because of retention shoulders 96a, 96b, the transmission
elements 24a, 24b may be retained within their respective recesses 90a, 90b. Nevertheless,
the transmission elements 24a, 24b may sit a select distance 105 from their respective
shoulders 18, 22 when not in contact with one another. Thus, gaps 106a, 106b may be
present between the transmission elements 24a, 24b and the bottoms of the recesses
90a, 90b, before the transmission elements 24a, 24b contact one another.
[0068] As is illustrated, the insulator 76a, 76b used to insulate the transmission elements
24a, 24b electrically from their respective shoulders 18, 22 may actually be exposed
to elements within the inside bore 104 of the downhole tools 10. Nevertheless, in
other embodiments, recesses 90a, 90b may be provided such that the transmission elements
24a, 24b are completely shielded from the central bore 104.
[0069] Referring to Figure 20, when the secondary shoulders 18, 22 come together, transmission
elements 24a, 24b may be urged into their respective recesses 90a, 90b. Thus, the
gaps 106a, 106b present between transmission elements 24a, 24b and the recesses 90a,
90b may decrease and retention shoulders 96a, 96b may release from corresponding retaining
shoulders formed in the recesses 90a, 90b. Since the transmission elements 24a, 24b
are spring-loaded with respect to the recesses 90a, 90b, the spring force may keep
conductive contact surfaces 82 firmly pressed together, thereby providing a reliable
electrical connection between the transmission elements 24a, 24b.
[0070] Referring to Figure 21, in other embodiments, a pair of transmission elements 24a,
24b may reside in recesses formed into longitudinal surfaces 108a, 108b parallel to
the central bore 104. Thus, when the secondary shoulders 18, 22 come together, transmission
elements 24a, 24b may align with one another and flanges 82a, 82b or contact points
82a, 82b may contact one another to provide an electrical connection. Since the transmission
elements 24a, 24b may need to slide past one another when the secondary shoulder 18
approaches the secondary shoulder 22, the transmission elements 24a, 24b may need
to sit flush with the surfaces 108a, 108b such that they don't interfere with one
another.
[0071] Referring to Figure 22, in selected embodiments, it may be desirable to directly
transmit an electrical signal from one pipe section 10 to another 10 using a direct
electrical connection without converting the signal to and from a magnetic field.
Since dirt, mud, lubricant, or other materials may interfere with the direct contacts,
it may be desirable that the surfaces be self-cleaning. Thus, curved or irregular
contact surfaces may be advantageous to push away undesired substances. Moreover,
because direct electrical contacts may cause arcing when they are connected or disconnected,
it may also be desirable to isolate the electrical contacts such that arcing does
not ignite flammable gasses, liquids, or the like, that may be present in a drilling
environment.
[0072] For example, in one embodiment, transmission elements 24a, 24b having electrical
contacts 112a, 112b may be inserted into annular recesses 90a, 90b provided in the
secondary shoulders 18, 22 of drill pipes 10 or drill tools 10. In selected embodiments,
these transmission elements 24a, 24b may be spring-loaded for the same reasons discussed
with respect to Figures 19 and 20. Moreover, additional biasing members 110a, 110b
constructed of an elastomeric, elastomeric-like, or spring-like material, may be used
to provide a bias to the electrical contacts 112a, 112b. This may enable the contacts
112a, 112b to be firmly pressed together to maintain a reliable connection.
[0073] To isolate arcing that may occur when electrical contacts 112a, 112b contact one
another, seals 114a, 114b that unite with corresponding contact surfaces 116a, 116b
may effectively isolate the contacts 112a, 112b, thereby avoiding exposure to explosive
or flammable substances.
[0074] Referring to Figure 23, in another embodiment, electrical contacts 126a, 126b located
in annular housings 28a, 28b, may reside in recesses formed into longitudinal surfaces
122, 123. The contacts 126a, 126b may be elastic or spring-loaded such that they remain
effectively pressed together to provide reliable connectivity. For example, the contacts
126a, 126b may compress or expand select distances 128a, 128b. In selected embodiments,
to isolate the contacts 126a, 126b from explosive or flammable substances that may
be present within a drill string bore 104, a seal 120 may be provided in one of the
shoulders 18, 22 to seal with a surface 122. Thus, the contacts 126a, 126b may be
effectively isolated from the central bore 104.
[0075] Referring to Figure 24, a transmission element 24 may include an annular contact
130 around the radius of the transmission element 24. The annular contact 130 may
be operably connected to an electrical conductor 26 or other transmission media 26
within an insulator 74. The annular contact 130 may be surrounded by an insulating
material 132 that may also have various elastic properties as will be discussed in
Figures 25A-C.
[0076] Likewise, the transmission element 24 may include seals 114a, 114b that may effectively
isolate the annular contact from the internal environment of the central bore. The
transmission element 24 may include an annular housing 28 that may reside in an annular
recess 90 formed or milled into the secondary shoulder 18. As has been discussed previously,
the annular housing 28 may interlock with shoulders or other retention mechanisms
provided within the annular recess 90. Moreover, angled surfaces of the annular housing
28 and recess 90 may provide a biasing effect to urge the transmission element 24
into a position slightly above the surface of the secondary shoulder 18.
[0077] Referring to Figures 25A-C, various positions of transmission elements 24a, 24b are
illustrated. As was previously mentioned, transmission elements 24a, 24b may use electrical
contacts 130a, 130b to directly transmit an electrical signal therebetween. The electrical
contacts 130a, 130 may be connected to electrical conductors 26a, 26b for transmission
along the drill string. The electrical contacts 130a, 130b may be surrounded by an
elastic insulating material 132a, 132b to provide electrical isolation from the annular
housings 28a, 28b, which may be constructed of an electrically conductive material.
[0078] The annular housings 28a, 28b may include various shoulders 136a, 136b that may interlock
with corresponding shoulders in the recesses 90a, 90b. Likewise, the annular housings
28a, 28b may include seals 114a, 114b that may mate with seal contact surfaces 116a,
116b before the electrical contacts 130a, 130b meet. With respect to Figure 25B, when
the seals 114 and corresponding surfaces 116 meet, the electrical contacts 130a, 130b
may still be separated.
[0079] Referring to Figure 25C, when the secondary shoulders 18, 22 come together, the annular
housings 28a, 28b may be urged into their corresponding recesses 90a, 90b. Since the
sides of the recesses 90a, 90b may be angled, this may exert side pressure 138a, 138b
on the annular housings 28a, 28b. This pressure 138a, 138b may flex the annular housings
28a, 28b and cause compression of the elastic insulating material 132a, 132b. This
may urge the electrical contacts 130a, 130b to contact one another. Moreover, since
the material 132a, 132b is elastic, the annular housings 28a, 28b may actually shift
in position with respect to the electrical contacts 130a, 130b, thereby allowing them
to make contact.
[0080] Referring to Figures 28A-C, in another embodiment, a rounded or curved contact 130b
may be configured to contact a relatively flat electrical contact 130a. As in the
example illustrated in Figures 27A-C, the contacts 130a, 130b may be surrounded by
an elastic insulating material 132a, 132b. The elastic material 132a, 132b may include
various contact points 138a, 138b that may contact one another before contact of the
electrical contacts 130a, 130b. Thus, the electrical contacts 130a, 130b may be effectively
isolated from their surrounding environment, preventing arcing or ignition of explosive
or flammable substances that may be present in a downhole-drilling environment.
[0081] As illustrated by Figure 26B, as the annular housings 28a, 28b come together, the
elastic insulating materials 132a, 132b meet at contact points 138a, 138b before contact
of electrical contacts 130a, 130b. As illustrated by Figure 26C, as the secondary
shoulders 18, 22 continue to come together, the annular housings 28a, 28b are likewise
brought together. This compresses the elastic insulating materials 132a, 132b further
urging the contacts 130a, 130b into contact with one another.
[0082] Referring to Figure 27, one example of an electrical contact 130 is illustrated.
In certain embodiments, an electrical contact 130 may include a conductor 137 having
peaks 130. These peaks 139 may create an irregular surface which may improve reliable
contact by pushing away dirt, fluids, or other substances that might interfere with
the contact 130. In selected embodiments, the conductor 137 may be contained in a
surrounding material 140 which may or may not be electrically conductive. The contact
130 may be connected to a conductor 26 that may be routed along a drill string. This
conductor 36 may be coated by a insulating material 74.
[0083] The present invention may be embodied in other specific forms without departing from
its essence or essential characteristics. The described embodiments are to be considered
in all respects only as illustrative, and not restrictive. The scope of the invention
is, therefore, indicated by the appended claims, rather than by the foregoing description.
All changes within the meaning and range of equivalency of the claims are to be embraced
within their scope.
1. A transmission element for transmitting information between downhole tools located
on a drill string, the transmission element comprising:
an annular core constructed of a magnetically-conductive material;
at least one conductor coiled around the annular core and electrically isolated therefrom;
an annular housing constructed of an electrically conductive material and partially
enclosing the annular core and the at least one conductor;
the annular housing further shaped to reside with an annular recess formed into a
surface of a downhole tool, and being electrically insulated from the surface thereof;
a biasing member to effect a bias between the annular housing and the annular recess,
urging the annular housing in a direction substantially perpendicular to the surface.
2. The transmission element of claim 1, further comprising a retention mechanism for
retaining the annular housing within an annular recess.
3. The transmission element of claim 1, wherein the at least one conductor is coated
with an electrically insulating material.
4. The transmission element of claim 1, wherein the surface is selected from the group
consisting of a secondary shoulder of a pin end, a secondary shoulder of a box end,
a primary shoulder of a pin end, and a primary shoulder of a box end of a downhole
tool.
5. The transmission element of claim 1, wherein the annular housing is at least partially
exposed to the central bore of a downhole tool;
6. The transmission element of claim 1, wherein the biasing member is selected from the
group consisting of a metal spring, an elastomeric material, and an elastomeric-like
material.
7. The transmission element of claim 1, wherein the annular core is characterized by an elongate cross-section.
8. The transmission element of claim 1, wherein the annular core has a cross-section
characterized by a height at least twice that of its width.
9. The transmission element of claim 1, wherein the annular housing further comprises
a shoulder formed along the exterior thereof, configured to engage a corresponding
shoulder formed within an annular recess.
10. The transmission element of claim 1, wherein the annular housing is configured to
make electrical contact with a second annular housing located on a second transmission
element, and wherein the contact surfaces of each annular housing are formed to be
self-cleaning.
11. A transmission element for transmitting information between downhole tools located
on a drill string, the transmission element comprising:
an annular core constructed of a magnetically-conductive material;
at least one conductor coiled around the annular core and electrically isolated therefrom;
an annular housing constructed of an electrically conductive material and partially
enclosing the annular core and the at least one conductor;
the annular housing further shaped to reside with an annular recess formed into a
surface of a downhole tool, and being electrically insulated from the surface thereof;
means for effecting a bias between the annular housing and the annular recess;
12. The transmission element of claim 11, wherein the means for effecting a bias between
the annular housing and the annular recess is due to radial tension between surfaces
of the annular housing and an annular recess.
13. The transmission element of claim 12, wherein the radial tension between the surfaces
of the annular housing and the annular recess are due to tension along at least one
of the outside diameters, the inside diameters, and a combination thereof, of the
annular housing and annular recess.
14. The transmission element of claim 11, further comprising a retention mechanism for
retaining the annular housing within an annular recess.
15. The transmission element of claim 11, wherein the annular housing is at least partially
exposed to the central bore of a downhole tool;
16. An apparatus for transmitting information between downhole tools located on a drill
string, the apparatus comprising:
a first transmission element, mounted to the end of a first downhole tool, the first
transmission element comprising a first contact;
a second transmission element, mounted to the end of a second downhole tool connectable
to the first downhole tool, the second transmission element comprising a second contact
configured to physically contact the first contact upon connecting the first and second
downhole tools; and
an isolation mechanism configured to isolate the first and second contacts from an
adjacent environment when contact occurs between the first and second contacts.
17. The apparatus of claim 16, wherein the isolation mechanism further comprises:
a first isolation component connected to the first transmission element; and
a second isolation component connected to the second transmission element, the second
isolation mechanism configured to engage the first isolation mechanism upon connecting
the first and second downhole tools.
18. The apparatus of claim 17, wherein the first and second isolation components are annular
housings having substantially U-shaped cross-sections and are formed to reside within
annular recesses formed in the first and second downhole tools, respectively.
19. The apparatus of claim 18, wherein the first and second contacts are conductive rings
formed to reside within the first and second annular housings, respectively.
20. The apparatus of claim 19, wherein the conductive rings are electrically insulated
from the first and second annular housings, respectively.
21. The apparatus of claim 19, wherein the conductive rings are coupled to the first and
second annular housings, respectively, by a at least one of a resilient, an elastomeric,
and an elastomeric-like material.