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Title:
ADAPTIVE ROUTING SYSTEM AND METHOD FOR A DOWNHOLE WIRELESS COMMUNICATIONS SYSTEM
Document Type and Number:
WIPO Patent Application WO/2020/139621
Kind Code:
A1
Abstract:
A network management technique for an acoustic communication system made up of a network of communication nodes is disclosed. The network management technique includes an adaptive routing scheme according to which the communication nodes evaluate received messages during an operation phase of the network and continuously update stored routing information based on the evaluation. The network management technique also includes a message loss detection scheme that can be implemented in parallel with the adaptive routing scheme. The message loss detection scheme can provide an early indication that the communication nodes should update routing information.

Inventors:
MOUFFOK KHALED (US)
Application Number:
PCT/US2019/066822
Publication Date:
July 02, 2020
Filing Date:
December 17, 2019
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
SCHLUMBERGER TECHNOLOGY CORP (US)
SCHLUMBERGER CA LTD (CA)
SERVICES PETROLIERS SCHLUMBERGER (FR)
SCHLUMBERGER TECHNOLOGY BV (NL)
International Classes:
H04B11/00; E21B41/00; E21B47/12; H04W40/02; H04W40/24
Foreign References:
US5987011A1999-11-16
US20060242323A12006-10-26
US20160356152A12016-12-08
CN107682434A2018-02-09
Other References:
YU HAITAO; YAO NIANMIN; LIU JUN: "An adaptive routing protocol in underwater sparse acoustic sensor networks", AD HOC NETWORKS, ELSEVIER, AMSTERDAM, NL, vol. 34, 16 October 2014 (2014-10-16), AMSTERDAM, NL, pages 121 - 143, XP029320588, ISSN: 1570-8705, DOI: 10.1016/j.adhoc.2014.09.016
Attorney, Agent or Firm:
SNEDDON, Cameron R. et al. (US)
Download PDF:
Claims:
What is claimed is:

1. A method for communicating in a network of communication nodes interconnected by an acoustic transmission medium that includes a downlink and an uplink, comprising: storing in a memory, by a first communication node, routing information that includes current uplink routing information and current downlink routing information that the first communication node uses to transmit messages on the network;

evaluating, by the first communication node, a message received on the acoustic transmission medium that is transmitted by a second communication node, wherein evaluating comprises:

determining whether the current uplink routing information or the current downlink routing information stored by the first communication node can be improved;

if so, updating the stored routing information; and,

if not, waiting for a next message.

2. The method as recited in claim 1 , wherein the message is received on the downlink of the acoustic transmission medium, and wherein evaluating comprises:

determining whether the second communication node is located further away on the uplink than the current uplink routing information; and

if so, updating the routing information to include the second communication node in the current uplink routing information.

3. The method as recited in claim 1 , wherein the message is received on the uplink of the acoustic transmission medium, and wherein evaluating comprises:

determining whether the second communication node is located further away on the downlink than the current downlink routing information; and if so, updating the routing information to include the second communication node in the current downlink routing information.

4. The method as recited in claim 1 , wherein evaluating comprises:

evaluating a signal-to-noise ratio of the received message; and

determining, based on the signal-to-noise ratio, whether the current uplink routing information or the current downlink routing information stored by the first communication node can be improved.

5. The method as recited in claim 1 , further comprising:

transmitting, by the first communication node, a second message on the acoustic transmission medium that includes the updated routing information;

receiving, by the second communication node, the second message; and updating, by the second communication node, routing information stored in a memory of the second communication node based on the updated routing information included in the received second message.

6. The method as recited in claim 1 , wherein the current uplink routing information and the current downlink routing information each includes a modulation mode.

7. The method as recited in claim 1 , wherein the stored routing information includes default routing information.

8. The method as recited in claim 7, further comprising:

detecting loss of a message in the network; and

in response to detecting the loss of a message, automatically using the default routing information to transmit messages on the network.

9. The method as recited in claim 7, further comprising:

detecting loss of a message in the network; and in response to detecting the loss of a message addressed a particular communication node, automatically updating the routing information by removing the particular communication node from the current uplink information and/or the current downlink information.

10. An acoustic communication system, comprising:

a plurality of acoustic communication nodes interconnected via a plurality of acoustic communication links, the acoustic communication nodes including a source node, a destination node, and a plurality of repeater nodes, wherein the repeater nodes are configured to:

store routing information that identifies a current acoustic communication link on which to route a received message that is addressed to the repeater node;

receive a message on an acoustic communications link that is part of a communication session between the source node and the destination node, wherein the message includes a node identifier identifying an acoustic communication node that transmitted the message;

evaluate the received message without regard to whether the message is addressed to the repeater node; and

use the node identifier in the message to update the stored routing information if the node identifier corresponds to an acoustic communication node that is on a different acoustic communication link than the stored current acoustic communication link.

11. The system as recited in claim 10, wherein the different acoustic communication link interconnects the repeater node to an acoustic communication node that is further away from the repeater node than the stored current acoustic communication link.

12. The system as recited in claim 10, wherein the repeater nodes are configured to evaluate messages received during an operation phase of the network and continuously update the stored routing information during the operation phase.

13. The system as recited in claim 12, wherein the repeater nodes are configured to share the updated stored routing information with other repeater nodes.

14. The system as recited in claim 10, wherein the repeater nodes are configured to detect a loss of a message on the network during an operation phase and to automatically update the stored routing information based on detection of a lost message.

15. The system as recited in claim 10, wherein the acoustic communication links are provided by a tubing deployed in a hydrocarbon well, and wherein the destination node is an acoustic modem coupled to a downhole equipment.

16. An acoustic network communication management method, comprising:

initiating an operation phase of an acoustic network that includes a communication session between a source node and a destination node;

transmitting, during the operation phase, a message from the source node to the destination node via an acoustic transmission medium interconnecting a network of acoustic communication nodes that include the source node, the destination node and a plurality of repeater nodes, the message including a request for data from the destination node;

receiving, by a repeater node, a message during the operation phase that includes the request;

evaluating, by the repeater node, the received message without regard to whether the received message is addressed to the repeater node;

updating, by the repeater node, stored routing information based on the evaluation of the received message; and

using, by the repeater node the updated stored routing information to route a next received message that is addressed to the repeater node.

17. The method as recited in claim 16, wherein the repeater node updates the stored routing information if the evaluation of the received message indicates that routing of messages can be improved.

18. The method as recited in claim 17, wherein the repeater node updates the stored routing information if the evaluation of the received message indicates that the message can be routed between the source node and the destination node using a fewer number of communication links.

19. The method as recited in claim 17, wherein the repeater node updates the stored routing information if the repeater node detects that a message has been lost on the network.

20. The method as recited in claim 16, wherein the acoustic network communication management method is implemented in an acoustic network deployed in a wellbore.

Description:
ADAPTIVE ROUTING SYSTEM AND METHOD FOR A DOWNHOLE WIRELESS

COMMUNICATIONS SYSTEM

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001 ] This application claims the benefit of European Patent Application

18306842.8 entitled“Adaptive Routing System and Method for A Downhole Wireless Communications System,” filed December 24, 2018, the disclosure of which is incorporated herein by reference.

BACKGROUND

[0002] Hydrocarbon fluids such as oil and natural gas are obtained from a subterranean geologic formation, referred to as a reservoir, by drilling a well that penetrates the hydrocarbon-bearing formation. Once a wellbore is drilled, various forms of well completion components may be installed in order to control and enhance the efficiency of producing the various fluids from the reservoir. Data representative of various downhole parameters, such as downhole pressure and temperature, are often monitored and communicated to the surface during operations before, during and after completion of the well, such as during drilling, perforating, fracturing and well testing operations. In addition, control information often is communicated from the surface to various downhole components to enable, control or modify the downhole operations.

[0003] Accurate and reliable communications between the surface and downhole components during operations can be difficult. Wired, or wireline, communication systems can be used in which electrical or optical signals are transmitted via a cable. However, the cable used to transmit the communications generally requires complex connections at pipe joints and to traverse certain downhole components, such as packers. In addition, the use of a wireline tool is an invasive technique which can interrupt productions or affect other operations being performed in the wellbore. Thus, wireless communication systems can be used to overcome these issues.

[0004] An example of a wireless system is an acoustic communication system. In acoustic systems, information or messages are exchanged between downhole components and surface systems using acoustic transmission mediums. As an example, a network of acoustic devices can be deployed downhole that uses tubing in the wellbore as the medium for transmitting information acoustically.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005] Certain embodiments of the invention are described with reference to the accompanying drawings, wherein like reference numerals denote like elements. It should be understood, however, that the accompanying drawings illustrate the various implementations described herein and are not meant to limit the scope of various technologies described herein. The drawings show and describe various embodiments of the current invention.

[0006] Fig. 1 is a schematic representation of an example of a well system that includes an acoustic communications network, according to an embodiment.

[0007] Fig. 2 is a schematic representation of an example of an acoustic modem that can be deployed in the acoustic communications network of Fig. 1 , according to an embodiment.

[0008] Fig. 3 is a timing diagram of an example of a known network discovery process that can be implemented in the acoustic communications network of Fig. 1 .

[0009] Fig. 4 is an example of a routing link table generated as a result of the network discovery process of Fig. 3.

[0010] Fig. 5 is a timing diagram of an example of an operation phase that can be implemented in the acoustic communications network of Fig. 1 in which routing is determined by the routing link table of Fig. 4.

[001 1 ] Fig. 6 is an example of a routing link table that can be used with an adaptive routing scheme implemented in the acoustic communications network of Fig. 1 , according to an embodiment.

[0012] Fig. 7 is a flow diagram of an adaptive routing scheme that can be implemented by the communication nodes in the acoustic communications network of Fig. 1 , according to an embodiment. [0013] Fig. 8 is a timing diagram of an operation phase of the acoustic communications network of Fig. 1 , during which the adaptive routing scheme of Fig. 7 is implemented, according to an embodiment.

[0014] Fig. 9 is a table illustrating an example of updating of link information by the adaptive routing scheme, according to an embodiment.

[0015] Fig. 10 is an example of a routing link table with updated link information, according to an embodiment.

[0016] Fig. 11 is a timing diagram of an operation phase of the acoustic communications network of Fig. 1 , during which routing is implemented in accordance with the updated routing link table of Fig. 10, according to an embodiment.

[0017] Fig. 12 is a timing diagram of an example of a message loss detection scheme that can be implemented in parallel with the adaptive routing scheme of Fig. 7, according to an embodiment.

SUMMARY

[0018] Certain embodiments of the present disclosure are directed to a method for communicating in a network of communication nodes interconnected by an acoustic transmission medium that includes a downlink and an uplink. A communication node stores in memory routing information that includes current uplink routing information and current downlink routing information. The method includes evaluating, by the communication node, a message received on the acoustic transmission medium. The evaluation includes determining whether the node’s current uplink routing information or the current downlink routing information can be improved. If so, the node updates its stored routing information. If not, the nodes waits for a next message.

[0019] Further embodiments of the present disclosure are directed to an acoustic communication system that includes multiple acoustic communication nodes interconnected via a plurality of acoustic communication links. The nodes include a source node, a destination node, and a plurality of repeater nodes. The repeater nodes store routing information that identifies a current acoustic communication link on which to route a received message that is addressed to the repeater node; to receive a message on an acoustic communications link that is part of a communication session between the source node and the destination node, where the message includes a node identifier identifying an acoustic communication node that transmitted the message; to evaluate the received message without regard to whether the message is addressed to the repeater node; and to use the node identifier in the message to update the stored routing information if the node identifier corresponds to an acoustic communication node that is on a different acoustic communication link than the stored current acoustic communication link.

[0020] Yet further embodiments of the present disclosure are directed to an acoustic network communication management method. In accordance with the method, an operation phase of an acoustic network is initiated that includes a communication session between a source node and a destination node. During the operation phase, a message is transmitted from the source node to the destination node via an acoustic transmission medium interconnecting a network of acoustic communication nodes that include the source node, the destination node and a plurality of repeater nodes. The message includes a request for data from the destination node. When a repeater node receives a message that includes the request, the repeater node evaluates the message without regard to whether the message is addressed to the repeater node and then updates stored routing information based on its evaluation. The repeater node then uses the updated stored routing information to route a next received message that is addressed to the repeater node.

DETAILED DESCRIPTION

[0021 ] In the following description, numerous details are set forth to provide an understanding of the present invention. However, it will be understood by those skilled in the art that the present invention may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible.

[0022] In the specification and appended claims: the terms“connect”,“connection”, “connected”,“in connection with”, and“connecting” are used to mean“in direct connection with” or“in connection with via one or more elements”; and the term“set” is used to mean “one element” or “more than one element”. Further, the terms “couple”, “coupling”, “coupled”, “coupled together”, and“coupled with” are used to mean“directly coupled together” or“coupled together via one or more elements”. As used herein, the terms“up” and “down”, “upper” and “lower”, “upwardly” and downwardly”, “upstream” and “downstream”; “above” and“below”; and other like terms indicating relative positions above or below a given point or element are used in this description to more clearly describe some embodiments of the invention.

[0023] Communication systems for transmitting information between the surface and downhole components are faced with numerous challenges. As just one example, operations performed within downhole environments can introduce noise which can affect the quality of communications and, thus, the ability to reliably send and transmit messages in a wireless communication system. When the downhole environment is a hydrocarbon-producing well, noise levels can increase substantially due to the flow of the hydrocarbon production fluid. In general, provided that the Signal to Interference and Noise Ratio (“SINR”) or Signal to Noise Ratio (“SNR”) is sufficiently high, then messages can be reliably received and communicated. Likewise, when the SNR is too low, message quality can be degraded and difficulties encountered in reliably receiving a message. Further, due to the harsh environment in a well, the useful life of the downhole communication components may be limited, which also can led to difficulties in reliably sending and receiving messages.

[0024] One type of wireless communication system that can be deployed in a downhole environment is an acoustic communications system that uses an elastic medium as the communications path. The acoustic communication system can be used in multiple contexts, including testing, drilling or production operations, and can be used to transmit various types of information, such as information related to downhole measurements, tool status, actuation commands, etc. Generally, an acoustic communication system is considered for use when there is no apparent way to run a wired communications path between the communicating devices. The communicating devices may involve an operational team, where a computer (or control system) is used in the vicinity of the well (e.g., on a rig, waveglider, etc.) or at a remote location that is indirectly connected to a communication module connected to the acoustic network. In other implementations, the acoustic communication network operates autonomously between the various oil and gas equipment.

[0025] In general, an acoustic communications network is composed of an arrangement of communication nodes in the form of acoustic modems that receive and transmit messages. The acoustic modems use a pipe string (or tubing) as the elastic transmission medium. The communication network is established by connecting a plurality of acoustic modems to tubing at axially spaced locations along the string. Each modem includes a transducer that can convert an electrical signal to an acoustic signal (or message) that is then communicated using the tubing as the transmission medium. An acoustic modem within range of a transmitting modem receives the acoustic message and processes it, including by demodulating and decoding the message. An example of an acoustic communication network 100 is shown schematically in Fig. 1 .

[0026] Referring to Fig. 1 , a network 100 of communication nodes (e.g., acoustic modems) 102 a-f is deployed in a wellbore 104 so that communications can be exchanged between a surface control and telemetry system 106 and downhole equipment along both a downlink (from the surface to the downhole equipment) and an uplink (from the downhole equipment to the surface). The surface control and telemetry system 106 can include processing electronics, a memory or storage device and transceiver electronics to transmit and receive messages to and from the network 100 via a wired connection 108. In various embodiments, the processing electronics can include a signal conditioner, filter analog-to-digital converter, microcontroller, programmable gate array, etc. The memory or storage device can store telemetry data received from the downhole equipment so that it can be processed and analyzed at a later time. Yet further, the memory or storage device can store instructions of software for execution by the processing electronics to generate messages to control and monitor performance of a downhole operation. Still further, the memory or storage device con store instructions of software for execution by the processing electronics to initialize the network configuration and automatically update, modify or otherwise adapt the configuration as needed to enable communications and/or to more efficiently and reliably communicate messages between the surface and the downhole components. [0027] The modems 102a-f are acoustically coupled to an elastic medium, such as tubing 1 10, which can be a jointed pipe string, production tubing or a drillstring, that provides the acoustic communications path. It should be understood, however, that the elastic medium may be provided by other structures, such as a tubular casing 1 12 that is present in the wellbore 104.

[0028] In addition to the modems 102a-f, the installation shown in Fig. 1 includes a packer 1 14 positioned on the tubing 1 10 at a region of interest 1 16. Various pieces of downhole equipment for testing and the like are connected to the tubing 1 10, either above or below the packer 1 14, such as a test valve 1 18 above the packer and a sensor 120 below the packer 1 14.

[0029] Two types of communication nodes generally are deployed in the acoustic network 100. The first type is a modem that is connected to an external tool (e.g., test valve 1 18 or sensor 120) at a fixed depth. This type of communication node is referred to as an“Interfaced Modem” (“IM”). The second type is a modem that is used to repeat (or forward), as well as to amplify (or boost), an acoustic message. This second type of communication node is referred to as a“Repeater Modem” (“RM”).

[0030] The repeater modems are used to account for the fact that wireless communication signals between surface systems and devices located furthest from the surface generally lack the strength to reach their destination. In many downhole applications, acoustic signals can experience an attenuation of about 10 decibels/1000 feet. Accordingly, when acoustic noise is present in the environment, it can be substantial relative to the strength of the acoustic signal.

[0031 ] A schematic illustration of a modem 102 is illustrated in Fig. 2. Modem 102 includes a housing 130 that supports an acoustic transceiver assembly 132 that includes electronics and a transducer 134 which can be driven to create an acoustic signal in the tubing 1 10 and/or excited by an acoustic signal received from the tubing 1 10 to generate an electrical signal. The transducer 134 can include, for example, a piezoelectric stack, a magneto restrictive element, and/or an accelerometer or any other element or combination of elements that are suitable for converting an acoustic signal to an electrical signal and/or converting an electrical signal to an acoustic signal. The modem 102 also includes transceiver electronics 136 for transmitting and receiving electrical signals. Power can be provided by a power supply 138, such as a lithium battery, although other types of power supplies are possible, including supply of power from a source external to the modem 102.

[0032] The transceiver electronics 136 are arranged to receive an electrical signal from and transmit an electrical signal to the downhole equipment, such as the sensor 120 and the valve 1 18. The electrical signal can be in the form of a digital signal that is provided to a processing system 140, which can encode and modulate the signal, amplify the signal as needed, and transmit the encoded, modulated, and amplified signal to the transceiver assembly 132. The transceiver assembly 132 generates a corresponding acoustic signal for transmission via the tubing 1 10.

[0033] The transceiver assembly 132 of the modem 102 also is configured to receive an acoustic signal transmitted along the tubing 1 10, such as by another modem 102. The transceiver assembly 132 converts the acoustic signal into an electric signal. The electric signal then can be passed on to processing system 140, which processes it for transmission as a digital signal to the downhole equipment. In various embodiments, the processing system 140 can include a signal conditioner, filter, analog-to-digital converter, demodulator, modulator, amplifier, encoder, decoder, microcontroller, programmable gate array, etc. The modem 102 also can include a memory or storage device 142 to store data received from the downhole equipment so that it can be transmitted or retrieved from the modem 102 at a later time. Yet further, the memory or storage device 142 can store instructions of software for execution by the processing system 140 to perform the various modulation, demodulation, encoding, decoding, etc. processes described above and the network management techniques and routing information that will be described below.

[0034] Returning again to Fig. 1 , to account for SNR limitations, communications between the surface and a downhole component often are performed as a series of hops. This is accomplished by positioning RMs at axially spaced intervals (e.g., 1000 ft.) along the acoustic communications path (e.g., a tubing) so that the RMs can forward acoustic messages to the final IM node. Because a communication system is designed to operate reliably in different types of noise conditions, the spacing between RMs often is configured to account for the worst case noise scenario.

[0035] Acoustic messages that are transmitted in downhole applications can include queries or commands that are sent from a surface system to one or more nodes. The surface system includes a surface modem that transmits the message to the addressed IM node via a route of RM nodes that has been determined when the network was established (e.g., during a network discovery phase) and/or a route that has been automatically modified or adapted, as will be described below. In many systems, redundancies are built in so that more than one modem along the route can be capable of receiving a given message.

[0036] In embodiments, communications on network 100 are packet-based. In general, a packet includes a preamble that includes information that enable the receiving nodes in the network 100 to detect the arrival of a new packet. That is, a portion of the message will contain network information from which the receiving modem can determine whether the message is addressed to it or another modem. If the message is addressed for another device, then the receiving modem amplifies it and acoustically retransmits it along the tubing. This process repeats until the communication reaches its intended destination. In embodiments, the information in the preamble also can include communication mode information that can be used to synchronize the transmitter and the receiver in the sending and receiving modems.

[0037] A packet also includes a header that contains information regarding the routing of the packets. Depending on the network management strategy, the header can include the identifications of the data source modem (e.g., an IM) connected to the device, the transmitting or repeater modem (e.g., an RM), the recipients, the direction of propagation (e.g., uplink, downlink), and/or the final destination modem (e.g., a surface modem or requestor), as examples. The header also can include an identifier associated with the packet and keys to decode the data portion of the packet, which contains the actual information that is communicated between the initial (or source) transmitting modem to the final destination modem. [0038] In the network 100 illustrated in Fig. 1 , when a message is detected, the receiving modem attempts to demodulate and decode it. As mentioned, the preamble of the message packet will include network information so that, when demodulated and decoded, the receiving modem can determine whether the message is locally addressed to it. If so, the modem manages the message by either forwarding it or executing the command. If the message calls for retransmission of a message, such as forwarding a message to another modem along the route or responding to a command or query, then the modem will transmit a new message that has been encoded and modulated in an appropriate manner.

[0039] In known communication networks, routing of messages between the communication nodes generally is predetermined and typically is based on a worst case noise environment. As such, regardless of the acoustic channel conditions or problems with the communication hardware, the nodes adhere to a fixed routing scheme even in situations where a message could be reliably received on a more efficient path or a lost message could be recovered. Accordingly, embodiments disclosed herein are directed to an adaptive method for setting communication links, modulation modes and other routing information between communication nodes that is performed automatically by the communication nodes. In embodiments, the adaptive method selects communication links, modulation modes and other routing information based on the furthest reachable node in the downlink and uplink directions.

[0040] It should be understood, however, that other selection criteria can be defined so that the routing decisions can encompass nodes other than the furthest reachable node. Examples of selection criteria that can be employed include quality metrics, such as SINR, SNR, the ratio between transmission and reception, a minimum number of receptions during a defined time period, a calculated success rate, etc. Regardless of the selection criteria, in accordance with the techniques described herein, received messages are continuously evaluated by the communication nodes to set and adapt routing information so that messages are forwarded to the downlink and uplink neighbors that can be reliably reached, such as the furthest downlink and uplink neighbors. [0041 ] In general, each node in the wireless network has a unique identifier that is referred to as a Node ID. Each node in the network has the ability to repeat received messages and can send and receive messages to and from at least its immediately adjacent neighbor (i.e. , the N+/-1 neighbors) in both the uplink and downlink directions. Each node maintains in its memory link information, such as a routing link table, that identifies the possible communication links and modulation modes between the nodes in the network. Each node also implements a routing function that uses the link information to determine the next node to which a received message should be routed. In known systems, the routing function is set to a default so that each node attempts to route messages to its N+2/N-2 neighbor, even in conditions in which the node could actually communicate further. If the communication to the N+2/N-2 neighbor fails, then the node will revert to the N+1/N-1 neighbor.

[0042] Before communications can occur on a network, the network is be configured during a configuration phase. In general, the configuration phase occurs prior to deploying the network. For example, in a wellbore application, the communication nodes are configured at the surface by assigning each modem a unique identifier (i.e., Node ID). Once the communication nodes are configured and run in hole, a surface controller that is hardwired to the node closest to the surface initiates a network discovery phase where each communication node tests communications two levels up and two levels down to enable a routing path and set the link information in the link table that is stored in memory. At the conclusion of the network discovery phase, the surface control system can be used in an operation phase in which it can request information from the network. The request and the requested information are routed through the network in accordance with the links that are set in the routing link table.

[0043] To illustrate the features that can be attained with the network management techniques described herein, a known network discovery technique will first be described. In accordance with this known technique, five types of acoustic messages are used:

1 . Discover: a message from the surface controller to the first communication node to initiate a network discovery process or from one communication node to another communication node to pass hand. Discovery messages include information about the links discovered by the previous communication nodes.

2. Test: a message sent from a communication node to test that node’s N+2 and N-2 communications.

3. Acknowledgement: an answer to a successful Test message reception.

4. Set: an answer to a successful Acknowledgement message reception from N+2.

5. Traceroute: when the last communication node (e.g., the node furthest from the surface, such as an IM node) completes the discovery process, the node will initiate an uplink message that summarizes the links discovered in order to share them with the communication nodes of the network to update their table of links.

[0044] Turning now to Fig. 3, a timing diagram of a known network discovery process 300 in a wireless network that includes five communication nodes RM1 , RM2, RM3, RM4 and IM5 and that uses these five types of messages is illustrated. In this example, RM1 is hardwired to a system controller 302 that is located in a surface control system 303. Communications between RM1 -4 and IM5 are implemented using wireless (e.g., acoustic) techniques.

[0045] In Fig. 3, the system controller 302 initiates the discovery process 300 by sending a Discovery message 304 to RM1 . RM1 responds by sending a Test message 306 addressed to its N+2 neighbor, RM3. In this example, RM2 also hears the Test message 306, and thus responds with an Acknowledge message 308 back to RM1 . RM3 successfully receives Test message 306 and responds with an Acknowledge message 310 back to RM1. In response to the Acknowledge message 310 from RM3, RM1 sends a Set message 312 to RM3 setting the parameters to use for communications in an operation phase. RM1 then sends a Discover message 314 to RM2 to pass hand so that RM2 can test its N+2 link. Discovery message 314 also include the routing information discovered by RM1 so that RM2 can use it to update the routing information in its link table. [0046] RM2 sends its Test message 316 to RM4. RM3 hears the Test message 316 and responds with Acknowledge message 318. When RM4 successfully receives Test message 316, RM4 responds to RM2 with an Acknowledge message 320. In response to Acknowledge message 320, RM2 sends a Set message 322 to RM4 with the communication parameters, and a Discover message 324 to RM3 to pass hand and provide the link information discovered by RM1 and RM2.

[0047] RM3 then sends a Test message 326 to IM5. RM4 hears the Test message 326 and responds with an Acknowledge message 328. When IM5 successfully receives Test message 326, IM5 responds to RM3 with an Acknowledge message 330. In response, RM3 sends a Set message 332 to IM5 with the communication parameters and a Discover message 334 to RM4 to pass hand and provide the link information discovered thus far by RM1 , RM2 and RM3.

[0048] RM4 sends a Test message 336 to IM5 (since RM4 does not have an N+2 neighbor on the downlink). IM5 responds with an Acknowledge message 338. RM4 then sends a Discover message 340 to IM5. Because IM5 is the last node in the network, IM5 responds with a Traceroute message 342 to RM4 that summarizes the links discovered in the discovery phase. RM4 repeats the Traceroute message 342 to RM3 and so forth so that the communication nodes in the network can update their link tables with the information discovered by other nodes.

[0049] The discovery process 300 illustrated in Fig. 3 consumed twenty-two messages to establish the link information shown in the routing link table 400 of Fig. 4, which defines the N+1 and N+2 links on the downlink and the N-1 and N-2 links on the uplink for each of the communication nodes. The routing link table 400 is stored in the memory of each of the communication nodes (e.g., memory 142 in Fig. 2). Once the discovery phase is complete, the network can enter an operation phases in which information can be exchanged between the surface controller 302 and downhole components in accordance with the network routing defined by the link table 400.

[0050] An example of a network communication in the operation phase is shown in Fig. 5. In this example, the system controller 302 has requested information from IM5. In accordance with the link table 400, RM1 routes the request in a message 402 to RM3, which repeats the request in a message 404 to IM5. IM5 responds with the requested information in a message 406 to RM3, which repeats the information in a message 408 to RM1 for transmission to the surface controller 302.

[0051 ] In general, in the operation phase in this example, if the N+2 communication is unsuccessful than the N+1 node will take hand. However, if the characteristics of the acoustic channel have changed to the extent that messages are being lost, then the discovery process 300 is reinitiated by the user via the system controller 302. The network management scheme described above thus is inefficient in terms of the large number of messages that are transmitted to discover the links, the inflexibility of the routing to adapt to changes in the acoustic channel or hardware problems once the discovery phase has been completed, and the need for user intervention in the event that messages are being lost.

[0052] Accordingly, embodiments described herein are directed to an adaptive routing technique that can automatically adapt (without user intervention) to changes in the acoustic channel and to hardware problems. Acoustic messages received during the operation phase of the acoustic network are evaluated in order to select and continuously adapt the routing information for the communication nodes. In embodiments, selection criteria can dictate that the selected routing information should set the links to the furthest node with which a node can successfully communicate. However, the selection criteria may also take into consideration other factors that can result in selection of a link to a node that is a further node but not the furthest possible node. In embodiments in which multiple different wireless communication or transmission modes can be implemented on the network, routing link tables specific to each mode can be established.

[0053] In embodiments, a message loss detection scheme can be implemented In parallel with the adaptive routing scheme. The message loss detection scheme can be implemented by the requesting node and the repeater nodes to trigger the requester to retry sending, or the repeaters to repeat the message in accordance with their respective repeating priorities. When the message loss detection scheme is implemented in conjunction with the adaptive routing scheme, the combination can enable an early network adaption to changes in the wireless channel or communication hardware issues. [0054] In general, the adaptive routing scheme starts with default routing information that includes a set of default links and a default modulation mode which the communication nodes use in the operation phase and thus may eliminate the need for a discovery phase. For example, the default links may be the most pessimistic network configuration in which the links are to each node’s N+1 and N-1 neighbors. An example of default links set in a link table 600 is shown in Fig. 6, in which the default pessimistic links on the downlink and uplink are set to N+1 and N-1 , respectively.

[0055] Fig. 7 illustrates a flow diagram of an example of an adaptive routing scheme 700 according to which the communication nodes can continuously update their routing information during the operation phase of an acoustic network as soon as a message is successfully received from a communication node that is further away on the uplink or downlink than the currently set communication node. At block 702, a communication node receives an acoustic message. The message can be addressed to the communication node. Or, the message may not be addressed to the communication node, but is received by the node through propagation on the acoustic medium. At block 704, the communication node examines the message to determine the message source node (e.g., based on a source identifier contained in the preamble of the message). In embodiments, at block 704, the communication node also evaluates the quality metrics of the message (e.g., SNR). At block 706, the communication node determines whether the message source node is below the communication node in the network (i.e. , on the communication node’s downlink). For example, the location of the source node can be determined based on information in the preamble of the message.

[0056] If the source node is on the downlink, then the communication node determines whether it can improve its downlink routing information (block 708). For example, routing can be improved if the source node is further down the downlink than the node to which the communication node currently routes downlink messages (e.g., as determined by the node’s current link table) and the quality metrics are satisfactory (e.g., SNR is satisfactory, a calculated success rate is satisfactory, etc.). If the downlink routing cannot be improved (e.g., the source node is not further down the downlink or the quality metrics indicate that communications may not be reliable or that the node should use a different modulation mode, as examples), then the communication node waits for the next acoustic message (block 710). If the downlink routing can be improved, then the communication node updates its routing information accordingly (block 712). For example, the node can add the new link to a list of possible current links or can replace a current link with the new link or can specify that a different modulation mode should be used. The node then waits for the next acoustic message (block 710).

[0057] Returning to block 706, if the communication node determines that the source node is not on its downlink, then the communication node determines if its uplink routing can be improved (e.g., the source node is further up the uplink than the node to which the communication node currently routes uplink messages, a calculated success rate has improved, etc.) (block 714). If the uplink routing cannot be improved, then the communication node waits for the next acoustic message (block 710). If the uplink routing can be improved, the communication node updates its uplink routing information in accordingly (block 716). For example, the node can add the new link to a list of possible current links or can replace a current link with the new link or can specify a different modulation mode. The node then waits for the next acoustic message (block 710).

[0058] The process shown in the flow diagram of Fig. 7 is performed continuously by the communication nodes. In embodiments, the process of Fig. 7 is performed continuously while the network is in the operation phase. In this manner, the communication nodes continuously update their routing information so that routing in the network can automatically adapt to changes in channel conditions and/or problems with the communication hardware. The nodes maintain their respective routing information in their local memories, and, in embodiments, can share their updated routing information with their neighbor nodes. For example, when a node next transmits a message on the network, the node can include the updated routing information as side information in the message. Any neighboring nodes that can hear the message can then see the update routing information, extract and decode the information, and then update their own routing information accordingly. In embodiments in which multiple different wireless communication or transmission modes can be implemented on the network, routing link tables specific to each mode can be established and stored. In embodiments, if messages are being lost in the network, then the communication nodes can automatically attempt a different transmission mode and/or can change to a previously successful link stored in the routing information and/or can revert to the default links defined in the link table for a particular mode.

[0059] The features of the adaptive routing scheme 700 can be seen in the example timing diagram of Fig. 8, which represents a communication session on an acoustic network where messages are exchanged between five nodes RM1 , RM2, RM3, RM4, and IM5 during the operation phase.

[0060] In the example of Fig. 8, messages are initially routed in the operation phase using the default links shown in the link table 900 of Fig. 9, where each node routes messages to its N+1 neighbor on the downlink and its N-1 neighbor on the uplink. Thus, in Fig. 8, RM1 routes (and addresses) a message 802 to its N+1 neighbor RM2. Message 802 is received by RM2 but also propagates on the downlink so that it also is received by RM3 and RM4 (although RM3 and RM4 are not the addressed recipients of the message 802). Since RM1 is further up the uplink than the nodes currently selected for each of RM3 (i.e. , RM2) and RM4 (i.e, RM3), then RM3 and RM4 update the uplink routing information in their respective link tables. That is, RM3 replaces RM2 with RM1 , and RM4 replaces RM3 with RM1 .

[0061 ] In Fig. 8, the transmission of messages that are addressed to a specific node is represented by solid arrows, and the propagation of messages that are received by nodes that are not addressed by the message is represented by dashed arrows.

[0062] An illustrative example of the manner in which routing information is updated is shown in the table 900 of link updates in Fig. 9. Specifically, for the message 802 sent by RM1 and received by RM2, RM3 updates link entry 902 and RM4 updates link entry 904.

[0063] Next, returning to Fig. 8, RM2 sends a message 804 to RM3 in accordance with the default N+1 entry in table 900. RM3 receives message 804 and, because the source of message 804 (i.e., RM2) is not further up RM3’s uplink (see entry 906 in table 900), RM3 does not update the link routing information. Flowever, message 804 also propagates to RM4. Because the message source, RM2, is not further up RM4’s uplink than RM4’s current link entry (i.e., RM1 in entry 904), RM4 also does not update the link routing information. [0064] Next, RM3 sends a message 806 to RM4. RM4 does not update its link routing information because RM3 is not further up the uplink than RM1 (i.e. , the current link for RM4 in entry 904). Message 806 also propagates to IM5. Because RM3 is further up the uplink than RM4 (i.e., the current link for IM5 as set in entry 908 in table 900), then IM5 updates entry 908 in the link table 900 and replaces RM4 with RM3 in entry 910.

[0065] Next, RM4 sends a message 808 to IM5. IM5 does not update its routing information.

[0066] Next, IM5 sends a message 810 on the uplink to RM4. RM4 does not update its link routing information. However, message 810 also propagates to RM3. Since IM5 (the source of message 810) is further down the downlink than RM3’s current link (i.e., RM4), the RM3 updates entry 912 in the link table 900 and replaces RM4 with IM5 in entry 914.

[0067] RM4 then sends a message 812 on the uplink to RM3. The message is received by RM3 and also propagates on the uplink to RM2 and RM1 . RM3 does not update its routing information. However, RM2 updates entry 916 on the downlink and replaces RM3 with RM4 at entry 918. Likewise, RM1 updates entry 920 on the downlink and replaces RM2 with RM4 at entry 922.

[0068] Next, RM3 sends a message 814 on the uplink to RM2, which also propagates to RM1. RM2 does not update its routing information. RM1 also does not update its routing information because RM3 is not further down the downlink than RMT current link RM4.

[0069] Finally, RM2 sends a message 816 on the uplink to RM1 , and the communication session ends.

[0070] An updated routing information table 1000 is shown in Fig. 10. Table 1000 corresponds to the adaptive routing scheme 700 implemented during the communication session of Figs. 8 and 9 and is used by the communication nodes in the next communication session during the operation phase. For example, as shown in the timing diagram of Fig. 1 1 , RM1 sends a message 1 102 that is addressed to RM4 that includes a request for information from IM5. RM4 repeats the information in a message 1 104 addressed to IM5. IM5 responds with the requested information in a message 1 106 addressed to RM3 on the uplink. RM3 repeats the information in a message 1 108 addressed to RM1 on the uplink.

[0071 ] Comparing the adaptive routing technique 700 to the prior technique shown in Fig. 3, the efficiencies attained by adaptive routing technique 700 are apparent. Because adaptive routing is performed during the operation phase, only eight messages were needed to both set the link and acquire the data from downhole. In contrast, using the prior technique, twenty-two messages were needed to set the links during a discovery phase, and another four messages were needed to acquire data during the subsequent operation phase. In other words, eighteen fewer messages were sent using the adaptive routing technique 700.

[0072] In embodiments, a message loss detection scheme 1200 (MLDS) can also be implemented in conjunction with the adaptive routing technique. In embodiments, the MLDS 1200 can be implemented as a timeout mechanism after message transmission and reception. In the event that an addressed communication node does not repeat the message due to either a hardware issue or a channel response change, the message source node will notice the issue and attempt to re-send the message. For example, the source node can attempt to re-send the message to the same repeater node or can try to send the message to a repeater node that is adjacent to the failed repeater node. Or, the communication nodes that received the message by acoustic propagation could regenerate the lost message and transmit it on to the final destination. In the latter case, the communication nodes can take over transmission of the message in accordance with a timeout/priority scheme that is based on their distance from the sender. As an example, the communication node closest to the source node could be the first communication node to attempt transmission. If that transmission is not successful, then the next closest node can try to send the message and so on, using the following formula as an example:

Timeout(id) = (Repeater ID - Sender ID) * T,

where“id” is different from Sender ID. [0073] If the repeater nodes cannot repeat the message, then the sender node can try to re-send the message either to the original repeater or to a repeater adjacent to the original repeater.

[0074] Fig. 12 illustrates an example of a MLDS scheme 1200 in which RM2 is not operational. In Fig. 12, message 1202 sent by RM1 is addressed to, but not received by, RM2. Thus after Timeout(1 ) period 1204, RM1 either sends the message 1202 to RM2 again or selects another node adjacent or close to RM2 or switches to another mode of transmission to send the message 1202 to RM2 in a different transmission mode that could be more robust than the previous transmission mode. In embodiments, RM1 can continue trying different transmission modes until the message 1202 either is successfully received by RM2 or all transmission modes have been attempted. In parallel with the attempts by RM1 , the communication nodes that received message 1202 through propagation - in this case RM3 and RM4 - will hold on to message 1202 temporarily for respectively timeout(3) period 1206 and timeout(4) period 1208, waiting for RM2 to repeat message 1202 or RM1 (the original sender) to retry sending message 1202. If RM2 does not repeat a re-transmitted message 1202 from RM1 , then RM3 takes over the process after timeout(3) period 1206 and repeats message 1202 in the form of message 1210, as illustrated in Fig. 12. If RM3 fails to repeat message 1202, then RM4 can take over after timeout period 1208 and repeat message 1202 in the form of message 1212.

[0075] As shown in the example of Fig. 12, IM5 responds to message 1212 with a message 1214 addressed to RM4 and which also propagates to RM3. RM4 repeats message 1214 in the form of message 1216 addressed to RM3 (which also propagates to RM2 and RM1 ). RM3 then sends message 1218 addressed to RM2, which also propagates to RM1 . RM2 does not successfully receive message 1218. After timeout(3’) period 1220, RM3 attempts to re-send message 1218 to RM2. Message 1218 again is not received by RM2, but propagates to RM1 . After timeout(T) period 122, RM1 takes over the process and uses message 1218 (block 1224).

[0076] In embodiments, in the event that RM3 or RM4 takes over, the messages sent by RM3 or RM4 could also include information about the failed attempts by RM1 and RM2, thus providing the communication nodes with an early notification of a network communication issue that may require the nodes to reevaluate and readapt their routing information. As an example, the information provided may indicate that the communication nodes need to revert to their default links and re-initiate the adaptive routing scheme from the default starting point and update the routing information accordingly. Or, the information provided in the message may indicate that the issue is local such that only routing relevant to the node that lost the message should be updated.

[0077] The MLDS technique can enhance the adaptive routing technique in many other manners. For example, when a sending node transmits a message on the network and a backup repeater node takes over because of a failure and repeats the message, the sending node will detect that the backup node has taken action. The sending node can then update its routing information, such as by removing the failed repeater node from the sending node’s currently routing information. Similarly, if a repeater node detects that a sending node has re-sent a message, the repeater node can update its routing information accordingly. Yet further, a node can update its routing information using a time-based strategy. For example, routing information can be updated if a node has not communicated with or has not received a message from a particular node after a pre defined period of time (i.e. , an inactive link). By implementing the MLDS 1200 technique, the communication nodes can provide an early indication of a communication condition on the network and take action to avoid potential communication failures and costly downtime.

[0078] The network management techniques, which include the adaptive routing scheme 700 and the message loss detection scheme 1200, described herein are particularly useful for use in hydrocarbon well environments. During oil and gas operations, the acoustic conditions change rapidly, which poses challenges with acoustic communications. The noise can be due to fluid flow in the string of pipes, or due to mechanical activity such as wireline, coil-tubing, or due to external factors such as rotation, friction and pipe banging. Because of these ever-changing noise conditions, loss of some of the point-to-point communications is inevitable and expected.

[0079] For oil and gas operations, the network management techniques described herein can be used for offshore and onshore operations. In offshore operations, the noise conditions are known to be more challenging around the seabed and in the riser section. In the riser section, external parameters such as wind, waves, and current generate movements of the riser and the landing string. Those movements can induce shocks of the riser with the landing string, which, in turn, generates acoustic noise in the landing string. Accordingly, embodiments described above can operate to provide a more reliable communication subsurface, as well as to provide the ability to implement acoustic communication in the riser section.

[0080] It should be further understood that the techniques described herein can be implemented in a variety of wireless communications systems, and that the physical layer of the communication is not limited to the acoustic telemetry system that has been described above. Further, single or multi-carrier modulation systems can be used in any wireless communication system. As an example, orthogonal frequency division multiplexing (OFDM) is a modulation technique that is suitable for frequency selective channels. Flowever, embodiments disclosed herein are not limited to the use of any particular type of modulation system.

[0081 ] While the present disclosure has been disclosed with respect to a limited number of embodiments, those skilled in the art, having the benefit of this disclosure, will appreciate numerous modifications and variations there from. It is intended that the appended claims cover such modifications and variations as fall within the true spirit and scope of the invention.