1. Field of the Invention
The present invention pertains to drill strings, and, more particularly, to a method and apparatus for testing electromagnetic connectivity in a drill string.
2. Description of the Related Art
Drilling operations, especially to establish production of hydrocarbon deposits, frequently employ relatively long drill strings terminated by a bit. The drill string is usually fed through the floor of a drilling rig. As the bit bores through the earth, additional sections of drill pipe, tools, etc. are made up and become a portion of the drill string. The drill string may eventually reach as long as 20,000″ 30,000″, or even longer.
As the industry evolves, obtaining information downhole regarding the drilling conditions is becoming more important. Some drilling applications also seek to control the direction of drilling from the surface by sending control signals downhole to the bit. The industry is therefore using a lot of instrumented tools and bits in drill strings. This requires electromagnetic connectivity up and down the drill string to provide power, transmit control information, and receive data.
Interruptions in this electromagnetic connectivity create numerous problems. The most immediate problem is the inability to send and receive signals to downhole, instrumented tools and bits. However, this problem leads to another significant problem namely, whether to proceed with drilling or to correct the connectivity problem. Fixing the connectivity problem typically involves tripping the drill string out of the bore, i.e., withdrawing the drill string one section at a time, and dissembling each section from the string. For relatively long drill strings, this may be a time-consuming practice costing significant amounts of money. Furthermore, if the interruption is toward the top of the drill string, it may be much more desirable to correct right away than it would be if the interruption were at the bottom of the drill string. Thus, it would be useful to know where in the drill string the interruption occurs. Knowing the location of the interruption would also be useful to expedite tripping the drill string out of the whole.
The invention is a method and apparatus for testing electromagnetic connectivity in a drill string. The method comprises transmitting a test signal down a transmission path in a drill string; receiving a reflection of the test signal; and determining from the reflection whether there is an interruption in the electromagnetic connectivity in the transmission path. In general, the apparatus comprises a signal generator for generating a test signal into the drill string; a receiver for receiving the reflection of the test signal; and means for determining from the reflection whether there is an interruption in the electromagnetic connectivity in the transmission path. Preferably, a common coil is included through which the test signal generated by the signal generator may be transmitted into a drill string and through which a reflection of the test signal may be received.
The invention may be understood by reference to the following description taken in conjunction with the accompanying drawings, in which like reference numerals identify like elements.
While the invention is susceptible to various modifications and alternative forms, the drawings illustrate specific embodiments herein described in detail by way of example. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.
Illustrative embodiments of the invention are described below. In the interest of clarity, not all features of an actual implementation are described in this specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developers″ specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort, even if complex and time-consuming, would be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.
The drill string 102 comprises “wired pipe” that is, it includes a transmission path (not shown, but discussed further below) down its length. In accordance with the present invention, the electromagnetic conductivity along this transmission path is tested using, in this particular embodiment, the method 200 illustrated in
The present invention contemplates wide variation in the implementation of the transmission path under test. However, the transmission path of the illustrated embodiment, and reasonable variations thereon, are more fully disclosed and claimed as follows:
A fuller description of the drill string 102 excerpted from these references will now follow to provide a firmer understanding of the transmission path under test in the illustrated embodiment.
Turning now to
However, other pin and box end designs may be employed.
Grooves 412, 415, best shown in
In the illustrated embodiment, the grooves 415, 412 are located so as to lie equidistant between the inner and outer diameter of the face 442 and the shoulder 445. Further, in this orientation, the grooves 415, 412 are located so as to be substantially aligned as the joint 103 is made up.
Parts of these references are excerpted below with respect to this particular embodiment of the electromagnetic couplers 416.
As previously mentioned, the electromagnetic coupler 416 consists of an Archimedean coil, or planar, radially wound, annular coil 503, inserted into a core 506. The laminated and tape wound, or solid, core 506 may be a metal or metal tape material having magnetic permeability, such as ferromagnetic materials, irons, powdered irons, ferrites, or composite ceramics, or a combination thereof. In some embodiments, the core material may even be a material without magnetic permeability such as a polymer, like polyvinyl chloride (“PVC”). More particularly, in the illustrated embodiment, the core 506 comprises a magnetically conducting, electrically insulating (“MCEI”) element. The annular coils 503 may also be wound axially within the core material and may consist of one or more than one layers of coils 503.
As can best be seen in the cross section in
The coil 503 is preferably embedded within a material (not shown) filling the trough 509 of the core 506. The material should be electrically insulating and resilient, the resilience adding further toughness to the core 506. Standard commercial grade epoxies combined with a ceramic filler material, such as aluminum oxide, in proportions of about 50/50 percent suffice. The core 506 is, in turn, embedding in a material (not shown) filling the groove 412 or 415. This second embedment material holds the core 506 in place and forms a transition layer between the core 506 and the steel of the pipe to protect the core 506 from some of the forces seen by the steel during joint makeup and drilling. This resilient, embedment material may be a flexible polymer, such as a two-part, heat-curable, aircraft grade urethane. Voids or air pockets should also be avoided in this second embedment material, e.g., by centrifuging at between 2500 to 5000 rpm for about 0.5 to 3 minutes.
In one particular embodiment (not shown), the core 506 is comprised of a plurality of segmented ferrite elements are held together in the appropriate configuration by means of a resilient material, such as an epoxy, a natural rubber, a fiberglass or carbon fiber composite, or a polyurethane, that forms a base for the segmented ferrite elements. Examples of such an embodiment may be found in:
However, such an embodiment for the core 506 is not necessary to the practice of the invention, and other suitable embodiments may be employed.
Returning to
An electrical conductor 448, shown in
However, other conductors (e.g., twisted wire pairs) may be employed in alternative embodiments.
The conductor loop represented by the coils 503 and the electrical conductor 448 is completely sealed and insulated from the pipe of the section 106. The shield (not otherwise shown) should provide close to 100% coverage, and the core insulation should be made of a fully-dense polymer having low dielectric loss, e.g., from the family of polytetrafluoroethylene (“PTFE”) resins, Dupont″s Teflon® being one example. The insulating material (not otherwise shown) surrounding the shield should have high temperature resistance, high resistance to brine and chemicals used in drilling muds. PTFE is again preferred, or a linear aromatic, semi-crystalline, polyetheretherketone thermoplastic polymer manufactured by Victrex PLC under the trademark PEEKÒ. The electrical conductor 448 is also coated with, for example, a polymeric material selected from the group consisting of natural or synthetic rubbers, epoxies, or urethanes, to provide additional protection for the electrical conductor 448.
Referring now to
Returning to
When the pin and box ends 406, 409 of two sections 106 are joined, the electromagnetic coupler 416 of the pin end 406 and the electromagnetic coupler 416 of the box end 409 are brought to at least close proximity. The coils 503 of the electromagnetic couplers 416, when energized, each produces a magnetic field that is focused toward the other due to the magnetic permeability of the core material. When the coils are in close proximity, they share their magnetic fields, resulting in electromagnetic coupling across the joint 103. Although is not necessary for the electromagnetic couplers 416 to contact each other for the coupling to occur, closer proximity yields a stronger coupling effect.
Returning now to
As those in the art having the benefit of this disclosure will appreciate, the test signal will be reflected by the termination of the transmission path over which it travels. The reflection is received via the coil 609 and the amplifier 612 and compared to a reference signal Vref by the amplifier 615. Depending on the output of the amplifier 615, the indicator 618 provides an indication of whether the electromagnetic connection across the joint 103, shown in
Consider the embodiment 800, shown in
The network analyzer 803, in turn, outputs the received reflected signal to the computing apparatus 809 over the line 827. The computing apparatus 809 is programmed with and executing a data handling software tool 827, such as one of the many commercially available from LABVIEWÒ. The data handling software tool 827 may be, for instance, encoded on the random access storage (not shown) of the computing apparatus 809 and executed by the processor (also not shown) thereof. The data handling software tool 827 collects and displays the data representing the reflected signal along with a reference standard. For instance, the data handling software tool 827 may display the trace 700 as the reference representing a good connection and a trace representing the reflected signal on the display 830 of the computing apparatus 809. A user may then visually inspect the two traces to determine whether a good connection has been made.
The invention contemplates variation in this aspect of the invention. For instance, in some embodiments, a user may use peripheral devices, such as the keyboard 833 and the mouse 836, to interact with the data handling software tool 827 through a graphical user interface (“GUI”, not shown). Such interaction may be to impose one or more of the exemplary traces 700704 to assist in the evaluation, or to manipulate the display in some fashion. In these embodiments, the traces 700704 may be stored in the storage of the computing apparatus 809, as shown in
Returning to
Also as was earlier noted, there is no theoretical limitation on the length of the drill string 102 and, hence, the transmission path. However, there may be practical limitations various alternative embodiments. Referring now again to
The present invention also is not limited to applications in which the drill string 102 is assembled and tested on the floor of the drilling rig. For instance, the present invention may be used in quality assurance testing after the sections 102 are manufactured but before they are shipped to a customer. Use of the invention in this fashion can, for example, test the transmission path to see if various portions, e.g., the electromagnetic couplers 416, shown best in
The present invention can also be used to test electromagnetic connectivity in a drill string downhole.
The drilling operation 900 includes a rig 906 from which the drill string 903 is suspended through a kelly 909. A data transceiver 912 is fitted on top of the kelly 909, which is, in turn, connected to a drill string 903 comprised of a plurality of sections of drill pipe 915 (only one indicated). Also within the drill string 903 are tools (not indicated) such as jars and stabilizers. Drill collars (also not indicated) and heavyweight drill pipe 918 are located near the bottom of the drill string 903. A data and crossover sub 921 is included just above the bit 902. The drill string 903 interfaces with a computing apparatus 925 through the kelly 909 by means of a swivel, such as is known in the art. One particular implementation employs a swivel disclosed more fully in U.S. application Ser. No. 10/315,263, entitled “Signal Connection for a Downhole Tool String”, and filed Dec. 10, 2002, in the name of the inventors David R. Hall, et al.
The drill string 903 will include a variety of instrumented tools for gathering information regarding downhole drilling conditions. For instance, the bit 902 is connected to a data and crossover sub 921 housing a sensor apparatus 924 including an accelerometer (not otherwise shown). The accelerometer is useful for gathering real time data from the bottom of the hole. For example, the accelerometer can give a quantitative measure of bit vibration. The data and crossover sub 921 includes a transmission path such as that described above for the sections 106 in
The joints 927 between these sections of the drill string 903, as well as the other joints (not indicated) of the drill string 903 comprise joints such as the joint 103 best shown in
To accommodate the transmission of the anticipated volume of data, the drill string 903 will transmit data at a rate of at least 100 bits/second, and on up to at least 1,000,000 bits/second. However, signal attenuation is a concern. A typical length for a section of pipe (e.g., the section 106 in
Such repeaters can be simple “dumb” repeaters that only increase the amplitude of the signal without any other modification. A simple amplifier, however, will also amplify any noise in the signal. Although the down-hole environment may be relatively free of electrical noise in the RF frequency range preferred by the illustrated embodiment, a “smart” repeater that detects any errors in the data stream and restores the signal, error free, while eliminating baseline noise, is preferred. Any of a number of known digital error correction schemes can be employed in a down-hole network incorporating a “smart” repeater. One suitable smart repeater is disclosed in U.S. application Ser. No. 10/613,549, entitled “Link Module For a Downhole Drilling Network,” and filed Jul. 1, 2003, in the name of David R. Hall, et al.
As is the case with the repeaters 930, the drill string 903 also includes a number of testing apparatuses, such as the testing apparatus 933. Each testing apparatus 933 may comprise a dedicated section of the drill string 903, as is the case for the embodiment illustrated in
Each of the testing apparatuses 933 generates a test signal, transmits it across a predetermined number of joints 927 further down in the drill string 903, and receive the reflections thereof. The testing apparatuses 933 then transmit the reflections, or data representing the reflections, back uphole to the computing apparatus 925. The computing apparatus 925 is programmed with respect to the invention in a manner similar to the computing apparatus 809 in
Thus, the computing apparatus 925 is programmed to facilitate determining from the reflection whether there is an interruption in the electromagnetic connectivity in the transmission path. Note, however, that the computing apparatus 925 may make the determination itself; for example, in a manner analogous to the embodiment 500 in
Note that some portions of the detailed descriptions herein are consequently presented in terms of a software implemented process involving symbolic representations of operations on data bits within a memory in a computing system or a computing device. These descriptions and representations are the means used by those in the art to most effectively convey the substance of their work to others skilled in the art. The process and operation require physical manipulations of physical quantities. Usually, though not necessarily, these quantities take the form of electrical, magnetic, or optical signals capable of being stored, transferred, combined, compared, and otherwise manipulated. It has proven convenient at times, principally for reasons of common usage, to refer to these signals as bits, values, elements, symbols, characters, terms, numbers, or the like.
It should be borne in mind, however, that all of these and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels applied to these quantifies. Unless specifically stated or otherwise as may be apparent, throughout the present disclosure, these descriptions refer to the action and processes of an electronic device, that manipulates and transforms data represented as physical (electronic, magnetic, or optical) quantities within some electronic device″s storage into other data similarly represented as physical quantities within the storage, or in transmission or display devices. Exemplary of the terms denoting such a description are, without limitation, the terms “processing,” “computing,” “calculating,” “determining,” “displaying,” and the like.
Note also that the software implemented aspects of the invention are typically encoded on some form of program storage medium or implemented over some type of transmission medium. The program storage medium may be magnetic (e.g., a floppy disk or a hard drive) or optical (e.g., a compact disk read only memory, or “CD ROM”), and may be read only or random access. Similarly, the transmission medium may be twisted wire pairs, coaxial cable, optical fiber, or some other suitable transmission medium known to the art. The invention is not limited by these aspects of any given implementation.
In one embodiment, shown in
The bottom-hole node 1002x interfaces with the bottom-hole assembly 928 located at the end of the drill string 903. Other, intermediate, nodes 10021-1002x-1 may be located or spaced to act as relay points for signals traveling along the down-hole network 1000 and to interface with various tools or sensors (not shown in
Communication links 100601006x-1 may be used to connect the nodes 100201002x to one another. The communication links 100601006x-1 may be comprised of cables or other transmission media integrated directly into sections 106 of the drill string 903, 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 links 100601006x-1 may be wireless connections. In certain embodiments, the down-hole network 1000 may function as a packet-switched or circuit-switched network 1000.
As in most networks, a plurality of packets 1009, 1012 are used to transmit information among the nodes 100201002x. The packets 1012 may be used to carry data from tools or sensors, located down-hole, to an up-hole node 10020, or may carry protocols or data necessary to the functioning of the network 1000. Likewise, selected packets 1009 may be transmitted from up-hole nodes 10020 to down-hole nodes 10021-1002x. These packets 1009, for example, may be used to send control signals from a top-hole node 1002x to tools or sensors located proximate various down-hole nodes 10021-1002x. Thus, a down-hole network 1000 may provide an effective means for transmitting data and information between components located down-hole on a drill string 903, and devices located at or near the surface of the earth 102.
To accommodate the transmission of the anticipated volume of data, the drill string 903 will transmit data at a rate of at least 100 bits/second, and on up to at least 1,000,000 bits/second. However, signal attenuation is a concern. A typical length for a section 106 of pipe is 30″ 120″. Drill strings in oil and gas production can extend as long as 20,000″ 30,000″, or longer, which means that as many as 700 sections of drill pipe, down hole tools, collars, subs, etc. can found in a drill string such as the drill string 903. The transmission line created through the drill string by the pipe described above will typically transmit the information signal a distance of 1,000 to 2,000 feet before the signal is attenuated to the point where amplification will be desirable. Thus, the repeaters 930 are provided for approximately for some of the components in the drill string 903, for example, 5% of components not to exceed 10%, in the illustrated embodiment. In the illustrated embodiment, the repeaters 930 are housed in the nodes 1002, as will be described more fully below, although this is not necessary to the practice of the invention.
Still referring to
The bottom-hole interface 1101 may communicate with an intermediate node 1002x-1 located up the drill string 903. The intermediate node 1002x-1 may also interface with or receive tool or sensor data 1112 for transmission up or down the network 1000. Likewise, other nodes 1002, such as a second intermediate node 10021, may be located along the drill string 903 and interface with other sensors or tools to gather data 1112 therefrom. Any number of intermediate nodes 1002 may be used along the network 1000 between the top-hole interface 1100 and the bottom-hole interface 1101.
A physical interface 1115 may be provided to connect network components to a drill string 903. For example, since data is transmitted directly up the drill string 903 on cables or other transmission media integrated directly into drill pipe or other drill string components, the physical interface 1115 provides a physical connection to the drill string so data may be routed off of the drill string 903 to network components, such as a top-hole interface 1100, or the computing apparatus 925, shown in
For example, a top-hole interface 1100 may be operably connected to the physical interface 1115. The top-hole interface 1100 may be connected to an analysis device, such as a computing apparatus 925. The computing apparatus 925 may be used to analyze or examine data gathered from various down-hole tools or sensors, e.g., the data 1112. Likewise, DWD tool data 1118 may be saved or output from the computing apparatus 925. Likewise, in other embodiments, DWD tool data 1118 may be extracted directly from the top-hole interface 1100 for analysis.
Referring to
Likewise, the hardware 1200 may include memory 1209, both volatile memory 1212 and non-volatile memory 1215, providing data storage and staging areas for data transmitted between hardware components 1200. Volatile memory 1212 may include random access memory (“RAM”) or equivalents thereof, providing high-speed memory storage. Memory 1209 may also include selected types of non-volatile memory 1215 such as read-only-memory (“ROM”), or other long term storage devices, such as hard drives and the like. Ports 1218 such as serial, parallel, or other ports 1218 may be used to input and output signals up-hole or down-hole from the node 1002, provide interfaces with sensors or tools located proximate the node 1002, or interface with other tools or sensors located in a drilling environment.
A modem 1221 may be used to modulate digital data onto a carrier signal for transmission up-hole or down-hole along the network 1000. Likewise, the modem 1221 may demodulate digital data from signals transmitted along the network 1000. A modem 1221 may provide various built in features including but not limited to error checking, data compression, or the like. In addition, the modem 1221 may 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 down-hole environment. Likewise, the modem 1221 may be configured to operate in full duplex, half duplex, or other mode. The modem 1221 may 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 node 1002 may also include one or several switches or multiplexers 1223 to filter and forward packets between nodes 1002 of the network 1000, or combine several signals for transmission over a single medium. Likewise, a demultiplexer (not shown) may be included with the multiplexer 1223 to separate multiplexed signals received on a transmission line.
A node 1002 may include various sensors 1226 located within the node 1002 or interfacing with the node 1002. Sensors 1226 may include data gathering devices such as pressure sensors, inclinometers, temperature sensors, thermocouplers, accelerometers, imaging devices, seismic devices, or the like. Sensors 1226 may be configured to gather data for transmission up the network 1000 to the grounds surface, or may also receive control signals from the surface to control selected parameters of the sensors 1226. For example, an operator at the surface may actually instruct a sensor 1226 to take a particular measurement. Likewise, other tools 1225 located down-hole may interface with a node 1002 to gather data for transmission up-hole, 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 down-hole network 1000, may be an important or critical issue. Various hardware or other devices of the down-hole network 1000 may 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 down-hole 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 118 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 assembly 928 to the surface.
To reduce data loss due to signal attenuation, amplifiers or repeaters 1272, may be spaced at various intervals along the down-hole network 1000. Amplifiers receive a data signal, amplify it, and transmit it to the next node 1002. Like an amplifier, a repeater receives a data signal and retransmits it at a higher power. However, unlike an amplifier, a repeater may remove noise from the data signal and, in some embodiments, check for and remove errors from the data stream.
Amplifiers, or “repeaters,” are provided for approximately for some of the components in the drill string 903, for example, 5% of components not to exceed 10%, in the illustrated embodiment. Although the amplifiers/repeaters 1272 are shown comprising a portion of the node 1002 in
Still referring to
The node 1002 may provide various functions 1203 that are implemented by software, hardware, or a combination thereof. For example, functions 1203 of the node 1002 may include data gathering 1236, data processing 1239, control 1242, data storage 1245, and other functions 1248. Data may be gathered from sensors 1252 located down-hole, tools 1255, or other nodes 1258 in communication with a selected node 1002. This data 1236 may be transmitted or encapsulated within data packets transmitted up and down the network 1000.
Likewise, the node 1002 may provide various data processing functions 1239. For example, data processing may include data amplification or repeating 1260, routing or switching 1263 data packets transmitted along the network 1000, error checking 1266 of data packets transmitted along the network 1000, filtering 1269 of data, as well as data compression or decompression 1272. Likewise, a node 1002 may process various control signals 1242 transmitted from the surface to tools 1275, sensors 1278, or other nodes 1281 located down-hole. Likewise, a node 1002 may store data that has been gathered from tools, sensors, or other nodes 1002 within the network 1000. Likewise, the node 1002 may include other functions 1248, as needed.
Referring to
In certain embodiments, the multiplexer 1223 may transmit several signals simultaneously on different carrier frequencies. In other embodiments, the multiplexer 1223 may coordinate the time-division multiplexing of several signals. Signals or packets received by the switch/multiplexer 1223 may be amplified by the amplifiers/repeaters 1227 and filtered by the filters 1230, such as to remove noise. 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. The modem 1221 may 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 down-hole The modem 1221 may also perform various tasks such as error-checking 1266. The modem 1221 may also communicate with a processor 1206. The processor 1206 may execute any of numerous applications 106. For example, the processor 1206 may run applications 1304 whose primary function is acquire data from one or a plurality of sensors 1226a-c. For example, the processor 1206 may interface to sensors 1226 such as inclinometers, thermocouplers, accelerometers, imaging devices, seismic data gathering devices, or other sensors. Thus, the node 1002 may include circuitry that functions as a data acquisition tool.
In other embodiments, the processor 1206 may run applications 1304 that may control various devices 1306 located down-hole. That is, not only may the node 1002 be 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 node 1002 may include a memory device 1209 implementing a data structure, such as a first-in, first out (“FIFO”) queue, that may be used to store data needed by or transferred between the modem 1221 and the processor 1206.
Other components of the node 1002 may include non-volatile memory 1212, which may be used to store data, such as configuration settings, node addresses, system settings, and the like. One or several clocks 1308 may be provided to provide clock signals to the modem 1221, the processor 1206, or any other device. A power supply 1233 may receive power from an external power source such as batteries. The power supply 1233 may provide power to any or all of the components located within the node 1002. Likewise, an RS232 port 1218 may be used to provide a serial connection to the node 1002.
Thus, the node 1002 described in
In general, the node 1002 may be housed in a module (not shown) having a cylindrical or polygonal housing defining a central bore. Size limitations on the electronic components of the node 1002 may restrict the diameter of the bore to slightly smaller than the inner bore diameter of a typical section of drill pipe 106. The module is configured for insertion into a host down-hole tool and may be removed or inserted as needed to access or service components located therein. In one particular embodiment, at least some of the electronic components are mounted in sealed recesses on the external surface of the housing and channels are milled into the body of the module for routing electrical connections between the electronic components.
Likewise, a packet 1400 may include one or several synchronization bytes 1406. The synchronization byte 1406 or bytes may be used to synchronize the timing of a node 1002 receiving a packet 1400. Likewise, a packet 1400 may include a source address 1409, identifying the logical or physical address of a transmitting device, and a destination address 120, identifying the logical or physical address of a destination node 1002 on a network 1000.
A packet 1400 may also include a command byte 1412 or bytes 1412 to provide various commands to nodes 1002 within the network 1000. For example, the command bytes 1412 may 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 packet 1400 may include data or information 1415 with respect to the length of data 1418 transmitted within the packet 1400. For example, the data length 1415 may be the number of bits or bytes of data carried within the packet 1400. The packet 1400 may then include data 1418 comprising a number of bytes. The data 1418 may include data gathered from various sensors or tools located down-hole, or may contain control data to control various tools or devices located down-hole. Likewise one or several CRC bytes 1421 may be used to perform error checking of other data or bytes within a packet 1400. Trailing marks 1424 may trail other data of a packet 1400 and provide any other overhead or synchronization needed after transmitting a packet 1400. One of ordinary skill in the art will recognize that network packets 1400 may take 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.
In the embodiment of
The following patents and patent application are hereby incorporated herein by reference for all purposes as if expressly set forth verbatim herein:
This concludes the detailed description. The particular embodiments disclosed above are illustrative only, as the invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the invention. Accordingly, the protection sought herein is as set forth in the claims below.
This invention was made with government support under Contract No. DE-FC26-97FT343656 awarded by the U.S. Department of Energy. The government has certain rights in the invention.