Patent ID: 12203328

DETAILED DESCRIPTION

Referring toFIGS.1-5, herein. A transmission system like that described herein and in the prior art figures that may be used for transmitting data and power in a downhole environment comprises an annular housing310, see also10at prior artFIG.14, and an annular ferrite channel330within the annular housing310. The ferrite channel330may comprise electrically insulating and magnetically conductive materials. The ferrite channel330may comprise a plurality of ferrite segments, like30at prior artFIG.14, closely aligned end for end or it may be a single, continuous ferrite channel330without interruptions. An example of an annular linear coil is depicted at46, prior artFIG.14. An annular nonlinear electrically conductive coil335may be disposed within a core region420defined by the inside surface380of the annular ferrite channel330and the open top surface320of the channel330. The core region420may be filled or partially filled with a nonelectrically conductive filler material315. The core region420may be substantially circular or noncircular having a major and minor diameter. An end of the annular nonlinear electrically conductive coil410,350may be connected to an electrical cable running within a downhole tool or between downhole tools

The annular nonlinear coil may comprise a wavy coil wire335. The wavy coil wire335may comprise an average of between 1 and 5 waves385per inch of coil length around the interior core region420of the ferrite channel330. The waves385may be constrained within the core region420of the ferrite channel330and may not exceed the major diameter of the core region420of the ferrite channel330. The wave height may be between an average of 3% and 95% of the major diameter of the core region420of the ferrite channel330.

The annular electrically conductive nonlinear coil335may comprise a helix wire400comprising vertical loops405. The helix400may comprise an average of 2 to 27 vertical loops405per inch of the coil's length. The helix coil400may be constrained within the core region420of the ferrite channel330. The vertical loops405may be spaced evenly or unevenly along the length of the coil400. The diameter of the loops405may be between 3% and 95% of the major diameter of the core region420of the ferrite channel330.

The annular electrically conductive nonlinear coil390may comprise a wavy vertical ribbon or strip390. The wavy vertical strip390may comprise vertically oriented corrugations395along its length. The strip may comprise an average of 2 to 6 corrugations395per inch of the coil's length. The strip390may be constrained within the core region420of the ferrite channel330. The corrugations395may or may not be spaced evenly along the length of the coil390. The height of the strip390may be between 3% and 95% of the major diameter of the core region420of the ferrite channel330.

The annular housing310may comprise a metal ring, a nonmetal ring, an annular groove in the body of a downhole tool, or an annular polymeric block. An example of a metal ring is shown at10, prior artFIG.14. The downhole tool may comprise a drill pipe, a sub within the drill string, a tool positioned along the drillstring or within the bottom hole assembly, or a drill bit. See prior artFIG.6. The surfaces of the annular groove325in the body of the downhole tool305may comprise a hardness greater than the hardness of the body305of the downhole tool305adjacent the annular groove325. The ferrite channel330and the nonlinear coil335may be molded within the polymeric block310.

The annular polymeric block310,310A may comprise a polymer selected from the group consisting of polyether ether ketone (PEEK), polytetrafluoroethylene (PTFE) (Teflon), polybenzimidazole (PBI), polyoxymethylene (Delrin), and polydicyclopentadiene (pDCPD). The annular polymeric block may comprise a combination of one or more polymeric materials. The annular polymeric block310may be a composite of polymer and electrically insulating and magnetically conductive materials. The presence of the magnetic materials within the polymeric block310,310A may prevent stray electromagnetic wave interference with the functioning of the transmission system. The annular polymeric block310may comprise a volume of Fe and Mn particles averaging between 10% and 65% of the volume of polymer. The volume of Fe and Mn particles may range in average diameter between 10 nm and 3 mm.

The annular polymeric block310may comprise a bumper355on its peripheral side wall. The polymeric block310may comprise one or more bumpers355around the outside periphery of the block310. The bumper355may be intermittent or continuous around the periphery of the block310. The bumper355may be aligned with a bumper seat425formed in the sidewall of the annular groove325. The bumper355may assist in positioning and removably fixing the transmission system in the annular groove325. The bumper355may comprise an anterior dimple360that may contribute to the resilience of the bumper355as it is fitted into and removed from the housing or groove325.

The annular polymeric block310may further comprise at least one void opening365molded within the block310. The presence of the void openings365may contribute to the resilience of the polymeric block310as it is installed into the downhole tool housing325or experiences the forces concomitant with tool string makeup and drilling. The added resilience in the block310may promote the longevity of transmission system. A void opening365within the polymeric block310may be aligned proximate to the bumper355.

The annular polymeric block310may comprise a gasket345protruding from its bottom side surface370. The block310may comprise a gasket seat375located within its bottom side surface370in which a gasket345may be installed. The gasket345may comprise a natural or artificial material suitable for withstanding the harsh, dynamic conditions downhole drilling. The gasket345may be molded within the block310and a portion of the gasket345may protrude from the block's bottom side surface370. The gasket345may promote rotational stability in the transmission system. The gasket345may comprise an opening through which an end of the nonlinear coil335, or a wire335attached to the nonlinear coil335, may exit the block310, as it passes from the ferrite channel330and the annular block310or other housing on its way350to connect with a cable running within the downhole tool305. The gasket345may seal the exiting wire340,350and the transmission system from the downhole environment. A similar gasket345may be used to seal the exiting wire that leads to ground415. The annular housing310of the annular ferrite channel330may comprise one or more ferrite segments, seeFIG.14at30, comprising openings for the passage of at least one end340of the annular electrically conductive nonlinear coil335. A continuous ferrite channel may also comprise openings to allow the passage of the annular coil335to connect with another cable in the tool or to connect with ground415. The gasket345may extend from the bottom of the core region420of the ferrite channel330through the housing310and into body of the downhole tool305adjacent the transmission system. Sealing the entire length of the exiting coil wire340,350as it passes into the tool body305.

The transmission system may further comprise an annular nonlinear electrically conductive coil comprising a twisted pair of wires as further described in prior artFIGS.20and21and related text.

The transmission system may further comprise an annular nonlinear electrically conductive coil comprises an electrically conductive core as further described in prior artFIGS.15-18and related text.

The following detailed description is taken from the '218 reference and applies equally to this application except where altered or modified by this application.

Referring to (Prior Art)FIG.6, a drill rig10may include a derrick12and a drill string14comprised of multiple sections of drill pipe16and other downhole tools16. A bottom-hole assembly20, connected to the bottom of the drill string14, may include a drill bit, sensors, and other downhole tools. Because a drill string14may penetrate into the ground 20,000 feet or more, receiving and transmitting data from a bottom-hole assembly20to the surface may present numerous obstacles. Data must be transmitted along what may be hundreds of sections of drill pipe, and across each tool joint.

Signal loss may occur at each of the tool joints due to coupling losses and mismatched transmission elements. For example, in selected embodiments, an electrical signal transmitted along the drill string14may be transmitted as a magnetic field across tool joints, losing energy each time it is converted. Signal loss may also occur because of voltage drops, or other factors, in cable, wires, or other transmission media extending the length of the drill string14. Thus, apparatus and methods are needed to ensure that data received from a bottom-hole assembly20or other downhole tools16is safely transmitted to the surface.

In selected embodiments in accordance with the invention, network nodes18may be inserted at desired intervals along the drill string14, such as every 1000 to 5000 feet, to perform various functions. For example, the network nodes18may function as signal repeaters18to regenerate data signals traveling up and down the drill string14. These nodes18may be integrated into an existing drill pipe16or downhole tool16or may be independent downhole tools18.

Referring to (Prior Art)FIG.7, in selected embodiments a downhole network17may be used to transmit information along a drill string14. A downhole network17may include multiple nodes18ae spaced up and down a drill string14. The nodes18ae may be intelligent computing devices18ae, or may be less intelligent connection devices, such as hubs or switches located along the length of the network17. Each of the nodes18may or may not be addressed on the network17. A node18emay be located to interface with a bottom hole assembly20located at the end of the drill string14. A bottom hole assembly20may include a drill bit, drill collar, and other downhole tools and sensors designed to gather data and perform various tasks.

Other intermediate nodes18bd may be located or spaced to act as relay points for signals traveling along the downhole network17the network17and to provide interfaces18bd to various tools or sensors located along the length of the drill string14. Likewise, a top-hole node18amay be located at the top or proximate the top of a drill string14to act as an interface to an analysis device28, such as a personal computer28.

Communication links24ad may be used to connect the nodes18ae to one another. The communication links24ad may be comprised of cables or other transmission media integrated directly into tools16of the drill string14, routed through the central bore of a drill string, or routed externally to the drill string. Likewise, in certain contemplated embodiments in accordance with the invention, the communication links24ad may be wireless connections. In certain embodiments, the downhole network17may function as a packet-switched or circuit-switched network17.

As in most networks, packets22a,22bmay be transmitted between nodes18ae. The packets22bmay be used to carry data from tools or sensors, located downhole, to an up-hole node18a, or may carry protocols or data necessary to the functioning of the network17. Likewise, selected packets22amay be transmitted from up-hole nodes18ato downhole nodes18be. These packets22a, for example, may be used to send control signals from a top-hole node18ato tools or sensors located proximate various downhole nodes18be. Thus, a downhole network17may provide an effective means for transmitting data and information between components located downhole on a drill string14, and devices located at or near the surface of the earth19.

Referring to (Prior Art)FIG.8, a network node18in accordance with the invention may include hardware29providing functionality to the node18, as well as functions30performed by the node18. The functions30may be provided strictly by the hardware29, applications executable on the hardware29, or a combination thereof. For example, hardware29may include one or several processors31capable of processing or executing instructions or other data. Processors31may include hardware such as busses, clocks, cache, or other supporting hardware.

Likewise, hardware29may include volatile34and non-volatile36memory32providing data storage and staging areas for data transmitted between hardware components29. Volatile memory34may include random access memory (RAM) or equivalents thereof, providing high-speed memory storage. Memory32may also include selected types of non-volatile memory36such as read-only-memory (ROM), or other long term storage devices, such as hard drives and the like. Ports38such as serial, parallel, or other ports38may be used to input and output signals uphole or downhole from the node18, provide interfaces with sensors or tools located proximate the node18, or interface with other tools or sensors located in a drilling environment.

A modem40may be used to modulate digital data onto a carrier signal for transmission uphole or downhole along the network17. Likewise, the modem40may demodulate digital data from signals transmitted along the network17. A modem40may provide various built in features including but not limited to error checking, data compression, or the like. In addition, the modem40may use any suitable modulation type such as QPSK, OOK, PCM, FSK, QAM, or the like. The choice of a modulation type may depend on a desired data transmission speed, as well as unique operating conditions that may exist in a downhole environment. Likewise, the modem40may be configured to operate in full duplex, half duplex, or other mode. The modem40may also use any of numerous networking protocols currently available, such as collision-based protocols, such as Ethernet, or token-based protocols such as are used in token ring networks.

A node18may also include one or several switches42or multiplexers42to filter and forward packets between nodes18of the network17, or combine several signals for transmission over a single medium. Likewise, a demultiplexer may be included with the multiplexer42to separate multiplexed signals received on a transmission line.

A node18may include various sensors44located within the node18or interfacing with the node18. Sensors44may include data gathering devices such as pressure sensors, inclinometers, temperature sensors, thermocouplers, accelerometers, imaging devices, seismic devices, or the like. Sensors44may be configured to gather data for transmission up the network17to the grounds surface, or may also receive control signals from the surface to control selected parameters of the sensors44. For example, an operator at the surface may actually instruct a sensor44to take a particular measurement. Likewise, other tools46located downhole may interface with a node18to gather data for transmission uphole, or follow instructions received from the surface.

Since a drill string may extend into the earth 20,000 feet or more, signal loss or signal attenuation that occurs when transmitting data along the downhole network17, may be an important or critical issue. Various hardware or other devices of the downhole network17may be responsible for causing different amounts of signal attenuation. For example, since a drill string is typically comprised of multiple segments of drill pipe or other drill tools, signal loss may occur each time a signal is transmitted from one downhole tool to another. Since a drill string may include several hundred sections of drill pipe or other tools, the total signal loss that occurs across all of the tool joints may be quite significant. Moreover, a certain level of signal loss may occur in the cable or other transmission media extending from the bottom-hole assembly20to the surface.

To reduce data loss due to signal attenuation, amplifiers48, or repeaters48, may be spaced at various intervals along the downhole network17. The amplifiers48may receive a data signal, amplify it, and transmit it to the next node18. Like an amplifier48, a repeater48may be used to receive a data signal and retransmit it at a higher power. However, unlike an amplifier48, a repeater48may remove noise from the data signal.

Likewise, a node18may include various filters50. Filters50may be used to filter out undesired noise, frequencies, and the like that may be present or introduced into a data signal traveling up or down the network17. Likewise, the node18may include a power supply52to supply power to any or all of the hardware29. The node18may also include other hardware54, as needed, to provide desired functionality to the node18.

The node18may provide various functions that are implemented by software, hardware, or a combination thereof. For example, functions30of the node18may include data gathering56, data processing58, control60, data storage62, and other functions64. Data may be gathered56from sensors66located downhole, tools68, or other nodes70in communication with a selected node18. This data56may be transmitted or encapsulated within data packets transmitted up and down the network17.

Likewise, the node18may provide various data processing functions58. For example, data processing may include data amplification72or repeating72, routing74or switching74data packets transmitted along the network17, error checking76of data packets transmitted along the network17, filtering78of data, as well as data compression79or decompression79. Likewise, a node18may process various control signals60transmitted from the surface to tools80, sensors82, or other nodes84located downhole. Likewise, a node18may store data that has been gathered from tools, sensors, or other nodes18within the network17. Likewise, the node18may include other functions64, as needed.

Referring to (Prior Art)FIG.9, in one embodiment, a downhole network17in accordance with the invention may include various nodes18spaced at selected intervals along the network17. Each of the nodes18may be in operable communication with a bottom-hole assembly20. As data signals or packets travel up and down the network17, transmission elements86ae may be used to transmit signals across tool joints of a drill string14.

As illustrated, in selected embodiments, inductive coils86ae may be used to transmit data signals across tool joints. An inductive coil86may convert an electrical data signal to a magnetic field. A second inductive coil may detect the magnetic field and convert the magnetic field back to an electrical signal, thereby providing signal coupling across a tool joint. Thus, a direct electrical contact is not needed across a tool joint to provide effective signal coupling. Nevertheless, in other embodiments, direct electrical contacts may be used to transmit electrical signals across tool joints.

In selected embodiments, when using inductive coils86ae, consistent spacing should be provided between each pair86ae of inductive coils to provide consistent impedance or matching across each tool joint. This will help to prevent excessive signal loss caused by signal reflections or signal dispersion at the tool joint.

Referring to (Prior Art)FIG.10, in one embodiment, a downhole network17in accordance with the invention may include a top-hole interface18aand a bottom-hole interface18e. A bottom-hole interface18emay interface to various components located in or proximate a bottom-hole assembly20. For example, a bottom-hole interface18emay interface with a temperature sensor94, an accelerometer96, a DWD (diagnostic-while-drilling) tool98, or other tools100or sensors100, as needed.

The bottom-hole interface18emay communicate with an intermediate node18clocated up the drill string. The intermediate node18cmay also interface with or receive tool or sensor data92bfor transmission up or down the network17. Likewise, other nodes such as a second intermediate node18bmay be located along the drill string and interface with other sensors or tools to gather data92atherefrom. Any number of intermediate nodes18b,18cmay be used along the network17between the top-hole interface18aand the bottom-hole interface18e.

A physical interface90may be provided to connect network components to a drill string14. For example, since data is transmitted directly up the drill string on cables or other transmission media integrated directly into drill pipe or other drill string components, the physical interface90provides a physical connection to the drill string so data may be routed off the drill string14to network components, such as a top-hole interface18a, or personal computer28.

For example, a top-hole interface18amay be operably connected to the physical interface90. The top-hole interface18amay be connected to an analysis device28such as a personal computer28. The personal computer28may be used to analyze or examine data gathered from various downhole tools or sensors. Likewise, DWD tool data18amay be saved or output from the personal computer28. Likewise, in other embodiments, DWD tool data88bmay be extracted directly from the top-hole interface18afor analysis.

Referring to (Prior Art)FIG.11, in selected embodiments, a node18may include various components to provide desired functionality. For example switches42, multiplexers42, or a combination thereof may be used to receive, switch, and multiplex or demultiplex signals, received from other up-hole110band downhole110anodes18. The switches/multiplexers42may direct traffic such as data packets or other signals into and out of the node18, and may ensure that the packets or signals are transmitted at proper time intervals, frequencies, or a combination thereof.

In certain embodiments, the multiplexer42may transmit several signals simultaneously on different carrier frequencies. In other embodiments, the multiplexer42may coordinate the time-division multiplexing of several signals. Signals or packets received by the switch/multiplexer42may be amplified48and filtered50, such as to remove noise. In certain embodiments received signals may simply be amplified48. In other embodiments, the signals may be received, data may be demodulated therefrom and stored, and the data may be remodulated and retransmitted on a selected carrier frequency having greater signal strength. A modem40may be used to demodulate analog signals received from the switch/multiplexer into digital data and modulate digital data onto carriers for transfer to the switches/multiplexer where they may be transmitted uphole or downhole. The modem40may also perform various tasks such as error-checking76. The modem40may also communicate with a microcontroller104. The microcontroller104may execute any of numerous applications106. For example, the microcontroller104may run applications106whose primary function is to acquire data from one or a plurality of sensors44a-c. For example, the microcontroller104may interface to sensors44such as inclinometers, thermocouples, accelerometers, imaging devices, seismic data gathering devices, or other sensors. Thus, the node18may include circuitry that functions as a data acquisition tool.

In other embodiments, the microcontroller104may run applications106that may control various devices46located downhole. That is, not only may the node18be used as a repeater, and as a data gathering device, but may also be used to receive or provide control signals to control selected devices as needed. The node18may include a memory device34such as a FIFO34that may be used to store data needed by or transferred between the modem40and the microcontroller104.

Other components of the node18may include non-volatile memory36, which may be used to store data, such as configuration settings, node addresses, system settings, and the like. One or several clocks102may be provided to provide clock signals to the modem40, the microcontroller104, or any other device. A power supply52may receive power from an external power source such as batteries. The power supply52may provide power to any or all of the components located within the node18. Likewise, an RS232 port38may be used to provide a serial connection to the node circuit18.

Thus, the node18described inFIG.6may have many more functions than those supplied by a simple signal repeater. The node18may provide many of the advantages of an addressable node on a local area network. The addressable node may amplify signals received from uphole110bor downhole110asources, be used as a point of data acquisition, and be used to provide control signals to desired devices46. These represent only a few examples of the versatility of the node18. Thus, the node18, although useful and functional as a repeater30, may have a greatly expanded capability.

Referring to (Prior Art)FIG.12, a packet112containing data, control signals, network protocols, and the like may be transmitted up and down the drill string. For example, in one embodiment, a packet112in accordance with the invention may include training marks114. Training marks114may include any overhead, synchronization, or other data needed to enable another node18to receive a particular data packet112.

Likewise, a packet112may include one or several synchronization bytes116. The synchronization byte116or bytes may be used to synchronize the timing of a node18receiving a packet112. Likewise, a packet112may include a source address118, identifying the logical or physical address of a transmitting device, and a destination address120, identifying the logical or physical address of a destination node18on a network17.

A method for synchronizing the timing of a node18receiving a packet112comprises determining a total signal latency between a control device and the node and then sending a synchronizing time from the control device to the node adjusted for the signal latency. Electronic time stamps may be used to measure latency between the control device and the node.

A method for triggering an action of the node synchronized to an event else where on the network comprises determining latency, sending a latency adjusted signal, and performing the action. The latency may be determined between a control device located near the surface and the node. The latency adjusted signal for triggering an action is sent to the node and the action is performed downhole synchronized to the event.

An apparatus for fixing computational latency within a deterministic region in a node may comprise a network interface modem, a high priority module and at least one deterministic peripheral device. The network interface modem is in communication with the network. The high priority module is in communication with the network interface modem. The at least one deterministic peripheral device is connected to the high priority module. The high priority module comprises a packet assembler/disassembler, and hardware for performing at least one operation.

A packet112may also include a command byte122or bytes122to provide various commands to nodes18within the network17. For example, commands122may include commands to set selected parameters, reset registers or other devices, read particular registers, transfer data between registers, put devices in particular modes, acquire status of devices, perform various requests, and the like.

Likewise, a packet112may include data or information124with respect to the length124of data transmitted within the packet112. For example, the data length124may be the number of bits or bytes of data carried within the packet112. The packet112may then include data126comprising a number of bytes. The data126may include data gathered from various sensors or tools located downhole, or may contain control data to control various tools or devices located downhole. Likewise one or several bytes128may be used to perform error checking of other data or bytes within a packet112. Trailing marks129may trail other data of a packet112and provide any other overhead or synchronization needed after transmitting a packet112. One of ordinary skill in the art will recognize that network packets112may take on many forms and contain varied information. Thus, the example presented herein simply represents one contemplated embodiment in accordance with the invention, and is not intended to limit the scope of the invention.

Referring to (Prior Art)FIG.13, a module130housing the node18may include a cylindrical housing134defining a central bore132. The cylindrical housing134may be substantially circular, or in other embodiments, may be polygonal. The central bore132may have a diameter that is slightly smaller than the inner bore diameter of a typical section of drill pipe16to accommodate and provide space to components of the node158.

Nevertheless, in selected embodiments, as batteries and electronic components become more compact, it is feasible that the central bore132of the module130could be substantially equal to that normally encountered in sections of drill pipe16or other downhole tools16. The module130may be configured for insertion into a host downhole tool16. Thus, the module130may be removed or inserted as needed to access or service components located therein.

In selected embodiments, the module130may include one or several grooves136or seal contact surfaces136to seal the module130within a host downhole tool. Seals inserted into the seal contact surfaces136or grooves136may prevent fluids such as drilling mud, lubricants, oil, water, and the like from contaminating circuitry or components inside the module130. Moreover, the entry of other substances such as dirt, rocks, gasses, and the like, may also be prevented.

In selected embodiments, the module130may include one or several recesses138ac to house various components contained in the module130. Selected recesses138may contain circuitry158while others138may be used for batteries154or other components. One or several channels141may be milled or formed into the cylindrical housing134to provide for the routing of wires between recesses138. In selected embodiments, a connector140may be used to connect node circuitry158to a cable, wire, or other link, traveling up or down the drill string14.

As illustrated, the module130may be characterized by a general wall thickness148. Likewise, in regions proximate recesses138or other channels141, a thinner wall thickness may be present. Nevertheless, a critical wall thickness should be maintained to provide structural reliability to the module130to support stresses encountered in a downhole environment. The cylindrical housing134may be constructed of any suitable material including steel, aluminum, plastics, and the like, capable of withstanding the pressures, stresses, temperatures, and abrasive nature of a downhole environment.

As illustrated, one or several transmission paths142may be milled or formed into the wall of the module130to provide an outlet for cables, wires, or other transmission media exiting the recess138. In selected embodiments, a connector140may be provided to simply link up with or connect to node circuitry158, or in other embodiments, a channel142amay enable the routing of cables, wires, and the like from a node circuit158, within the recess138c, to a transmission element152. A transmission element152may be provided in an annular recess144milled or otherwise formed into the end of the cylindrical housing134.

As illustrated, a module130is equipped with components or circuitry158needed to provide functionality to the module130. For example, batteries154connected in series or parallel may be inserted into selected recesses138of the module130. Wires156may be routed through channels141interconnecting the recesses138to connect the batteries154together, or to connect the batteries to node circuitry158.

Likewise, node circuitry158, or components158, may be located within other recesses138. As was previously stated, a conductor160, cable160, or other transmission media160, may travel from the node circuitry158to a transmission element152. The transmission element152may transmit energy to another transmission element in contact therewith. The transmission element152may have an annular shape and may transmit energy by direct electrical contact, or may convert an electrical current to a magnetic field. The magnetic field may then be detected by another transmission element in close proximity thereto located on a subsequent downhole tool16.

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.

Referring to (Prior Art)FIG.14(taken from FIG. 10 of the '003 reference) is an exploded view of the components used to produce the inductive coupler70and will be used to discuss the methods of assembling the same. The primary components, a generally U-shaped annular housing10, a plurality of generally U-shaped magnetically conductive electrically insulating (MCEI) segments30, and a conductor such as an insulated wire40are provided and form an assembly which will then be consolidated with a melted polymer. A generally U-shaped annular housing10forms the “backbone” of the inductive coupler. The annular housing10defines an opening17therethrough which communicates with the recess15. In one embodiment a bridge (not shown) formed in a T-shape with a through hole can be placed in the opening17. The bridge helps support the generally normal bend45in the insulated wire40when such a need is deemed appropriate.

Next, a meltable polymer liner150is placed in the recess15. In a preferred embodiment the meltable polymer liner is generally U-shaped with an open end152. A first end154and second end156of the annular liner150form a gap155adjacent the opening17through the annular housing10. The MCEI segments30are arranged so as to provide a gap135therebetween adjacent the opening and placed on top of the annular liner so as not to interfere with the gap155. Furthermore the MCEI segments are aligned to form a generally circular trough75.

A conductor such as an insulated wire40comprises a first portion46and a second portion48. The first portion46is generally normal at a bend45to the second portion48. The conductor first portion46is placed within the circular trough75formed by the aligned MCEI segments30with the second portion48extending through the gap155and passing through the opening17of the annular housing10. In the most preferred embodiment, the shape of the MCEI segments will require prior stringing of the MCEI segments30on the conductive loop46thus creating a sub-assembly. Such a shape is discussed above. In this situation, the MCEI segments30, first portion46, and second portion48are placed as a sub-assembly within the annular housing10and on top of the meltable polymer liner150in one step.

An end47of the first portion46is preferably electrically connected to the annular housing10forming an attachment. This is preferably accomplished by welding the housing and end together. Another method of attachment is brazing the end to the housing or even a combination of the two. Additionally, the means of electrically connecting the two may employ any method so long as it places the end in electrical communication with the annular housing.

Following the electrical connection step of the assembly process, a generally circular, meltable polymer cap170preferably with a protrusion (not shown) is placed adjacent the circular trough75formed by the plurality of MCEI segments30such that the protrusion fits within the trough and preferably rests on top of the insulated conductor. This feature will be shown in greater detail in subsequent drawings.

The assembly is then placed in a thermal press such as that depicted inFIG.8and heated to a sufficient temperature to at least partially melt the cap and liner together, thereby consolidating the inductive coupler. Preferably, the amount of polymer in the liner and cap, the heat and the pressure are all selected so as to ensure that all spaces between the segments, the annular housing and the conductor are filled with polymer upon cooling.

Referring to (Prior Art)FIGS.15and16(taken from FIGS. 16A and 16B of the '962 reference)FIG.16Aschematically illustrates a wired link according to the conduits (e.g., WDPs) ofFIGS.2-4. Thus, a pair of opposing toroidal transformers226,236(components of respective communicative couplers) are interconnected by a cable214having a pair of insulated conducting wires that are routed within the tubular body of a conduit. Each toroidal transformer employs a core material having high magnetic permeability (e.g., Supermalloy), and is wrapped with N turns of insulated wire (N.about.100 to 200 turns). The insulated wire is uniformly coiled around the circumference of the toroidal core to form the transformer coils (not separately numbered). Four insulated soldered, welded or crimped connections or connectors215are utilized to join the wires of the cable214with the respective coils of the transformers226,236.

Reliability is critical for such WDP joints. If any wire in such a joint breaks, then the entire WDP system that employs the failing WDP joint also fails. There are several failure modes that might occur. For example, “cold solder joints” are not uncommon—where solder does not bond correctly to both wires. These can be intermittently open and then fail in the open condition. Prolonged vibration can cause wires to fatigue and break if they are not rigidly secured. Thermal expansion, shock, or debris might damage or cut the wire used to wrap the toroidal core.

FIG.16Bschematically illustrates a pair of independent wired links for employment by a conduit such as a WDP joint in accordance with the present invention. Thus, a pair of opposing toroidal transformers1626,1636each includes a coil system having two independent coil windings, with each coil winding lying substantially within a 180.degree. arc of the coil system. More particularly, toroidal transformer1626has a first coil winding1626aand a second coil winding1626b, each of which is independently and uniformly coiled about half the circumference of the toroidal core of transformer1626. Similarly, toroidal transformer1636has a first coil winding1626aand a second coil winding1626b, each of which is independently and uniformly coiled about half the circumference of the toroidal core of transformer1636. A pair of insulated conducting wires, referred to as cable1614a, extend between and are connected at respective ends thereof to the coil windings1626a,1626aby way of four insulated solder joints1615a. Similarly, a pair of insulated conducting wires, referred to as cable1614b, extend between and are connected at respective ends thereof to the coil windings1626b,1626bby way of four insulated solder joints1615b. Cable1614ais routed independently of cable1614b(meaning separate electrical pathways, but not necessarily remote routing locations within a WDP) so that the cables and their respective interconnected coil windings establish two independently-wired links.

It will be appreciated that WDP reliability can be improved by using a double wrap (or other multiple wrap) configuration as shown inFIG.16B. In this design, there is a second, redundant circuit. Each toroidal core is wrapped with two separate coil windings (indicated by the dotted and dashed lines). In a particular embodiment, each winding has the same number of turns (M). However, the two wraps could have a different number of turns and still provide most of the benefits of redundancy. If M=N, then the electromagnetic properties of the new design are essentially the same as the previous design.

Because the two circuits are in parallel, if one circuit fails, the other circuit can still carry the telemetry signal. Furthermore, the characteristic impedance of the transmission line will not change significantly, so that such a failure will not increase the attenuation. The series resistance of the connecting wires will increase in this section of drill pipe if one circuit has failed, but the series resistance of the connecting wires does not dominate the transmission loss anyway. The leakage flux from the toroidal core will also increase slightly if one circuit fails, but this will have a minor effect as well. Because the cores' magnetic permeability is very large, most of the flux from the one winding will still remain in the core.

Referring to (Prior Art)FIGS.17and18(taken from FIGS. 2 and 4 of the '962 reference) WDP joint210is shown to have communicative couplers221,231—particularly inductive coupler elements—at or near the respective end241of box end222and the end234of pin end232thereof. A first cable214extends through a conduit213to connect the communicative couplers,221,231in a manner that is described further below.

The WDP joint210is equipped with an elongated tubular body211having an axial bore212, a box end222, a pin end232, and a first cable214running from the box end222to the pin end232. A first current-loop inductive coupler element221(e.g., a toroidal transformer) and a similar second current-loop inductive coupler element231are disposed at the box end222and the pin end232, respectively. The first current-loop inductive coupler element221, the second current-loop inductive coupler element231, and the first cable214collectively provide a communicative conduit across the length of each WDP joint. An inductive coupler (or communicative connection)220at the coupled interface between two WDP joints is shown as being constituted by a first inductive coupler element221from WDP joint210and a second current-loop inductive coupler element231′ from the next tubular member, which may be another WDP joint. Those skilled in the art will recognize that, in some embodiments of the present invention, the inductive coupler elements may be replaced with other communicative couplers serving a similar communicative function, such as, e.g., direct electrical-contact connections of the sort disclosed in U.S. Pat. No. 4,126,848 by Denison.

FIG.4depicts the inductive coupler or communicative connection220ofFIG.3in greater detail. Box end222includes internal threads223and an annular inner contacting shoulder224having a first slot225, in which a first toroidal transformer226is disposed. The toroidal transformer226is connected to the cable214. Similarly, pin-end232′ of an adjacent wired tubular member (e.g., another WDP joint) includes external threads233′ and an annular inner contacting pipe end234′ having a second slot235′, in which a second toroidal transformer236′ is disposed. The second toroidal transformer236′ is connected to a second cable214′ of the adjacent tubular member9a. The slots225and235′ may be clad with a high-conductivity, low-permeability material (e.g., copper) to enhance the efficiency of the inductive coupling. When the box end222of one WDP joint is assembled with the pin end232′ of the adjacent tubular member (e.g., another WDP joint), a communicative connection is formed.FIG.4thus shows a cross section of a portion of the resulting interface, in which a facing pair of inductive coupler elements (i.e., toroidal transformers226,236′) are locked together to form a communicative connection within an operative communication link. This cross-sectional view also shows that the closed toroidal paths240and240′ enclose the toroidal transformers226and236′, respectively, and that the conduits213and213′ form passages for internal electrical cables214and214′ that connect the two inductive coupler elements disposed at the two ends of each WDP joint.

The above-described inductive couplers incorporate an electric coupler made with a dual toroid. The dual-toroidal coupler uses inner shoulders of the pin and box ends as electrical contacts. The inner shoulders are brought into engagement under extreme pressure as the pin and box ends are made up, assuring electrical continuity between the pin and the box ends. Currents are induced in the metal of the connection by means of toroidal transformers placed in slots. At a given frequency (for example 100 kHz), these currents are confined to the surface of the slots by skin depth effects. The pin and the box ends constitute the secondary circuits of the respective transformers, and the two secondary circuits are connected back to back via the mating inner shoulder surfaces.

Referring to (Prior Art)FIGS.19-21(taken from FIGS. 5, 6, and 7 of the '177 reference). InFIGS.5,6, and7the fractional loops67,70are half of a full loop. It is believed that the half loops have half the inductance that a full loop may have. It is believed that the fraction of inductance of a coil with fractional loops of equal distance may be determined in relation to a full loop coil by the following equation: L=1/n.sup.2., wherein L represents inductance and n is the number of fractional loops. According to the equation, a coil45comprising two half loops67,70would have ¼ the inductance. A coil45with three equal fractional loops would have 1/9 the inductance. A coil45with four equal fractional loops82,83,84,85(shown inFIG.8) would have 1/16 the inductance. It is believed that the reduced inductance is made up in the reduced impedance reflections, which is believed to cause signal loss and attenuation.