WO2018044471A1

WO2018044471A1 - Methods of acoustically communicating and wells that utilize the methods

Info

Publication number: WO2018044471A1
Application number: PCT/US2017/044938
Authority: WO
Inventors: Scott William CLAWSON; Limin Song; Yibing Zhang; Henry Alan Wolf
Original assignee: Exxonmobil Upstream Research Company
Priority date: 2016-08-30
Filing date: 2017-08-01
Publication date: 2018-03-08
Also published as: CN109642457B; AU2017321139B2; AU2017321139A1; CA3033986A1; MX2019001987A; CN109642457A; CA3033986C

Abstract

The methods utilize an acoustic wireless network including a plurality of nodes spaced-apart along a length of a tone transmission medium, the methods include encoding an encoded character with an encoding node. The encoding includes selecting a first frequency based upon a first predetermined lookup table and the encoded character, and transmitting a first transmitted acoustic tone at the first frequency. The encoding further includes selecting a second frequency based upon a second lookup table and the encoded character, and transmitting a second transmitted acoustic tone at the second frequency.These methods also include decoding a decoded character with a decoding node. The decoding includes receiving the first and second acoustic tone, calculating first and second frequency distributions for the respective tones, and determining a first and second decoded character distribution for the decoded character and identifying the decoded character based upon the first and second decoded character distributions.

Description

METHODS OF ACOUSTICALLY COMMUNICATING AND WELLS THAT

UTILIZE THE METHODS

Cross Reference To Related Application

[0001] This application claims benefit of U.S. Provisional Application Serial No.

62/428,385, filed November 30, 2016 entitled "Methods of Acoustically Communicating And Wells That Utilize The Methods, " and claims benefit of and priority to U.S. Provisional Application Serial No. 62/381,330, filed August 30, 2016, entitled "Communication Networks, Relay Nodes for Communication Networks, and Methods of Transmitting Data Among a Plurality of Relay Nodes, " the disclosures of which are incorporated herein by reference in their entireties.

Field of the Disclosure

[0002] The present disclosure relates generally to methods of acoustically communicating and/or to wells that utilize the methods.

Background of the Disclosure

[0003] An acoustic wireless network may be utilized to wirelessly transmit an acoustic signal, such as a vibration, via a tone transmission medium. In general, a given tone transmission medium will only permit communication within a certain frequency range; and, in some systems, this frequency range may be relatively small. Such systems may be referred to herein as spectrum-constrained systems. An example of a spectrum-constrained system is a well, such as a hydrocarbon well, that includes a plurality of communication nodes spaced- apart along a length thereof.

[0004] Under certain circumstances, it may be desirable to transmit data, in the form of acoustic signals, within such a spectrum-constrained environment. However, conventional data transmission mechanisms often cannot be effectively utilized. Thus, there exists a need for improved methods of acoustically communicating and/or for wells that utilize the methods.

Summary of the Disclosure

[0005] Methods of acoustically communicating and wells that utilize the methods are disclosed herein. The methods generally utilize an acoustic wireless network including a plurality of nodes spaced-apart along a length of a tone transmission medium. In some embodiments, the methods include methods of communicating when the acoustic wireless network is spectrum-constrained. In these embodiments, the methods include encoding an encoded character with an encoding node of the plurality of nodes. The encoding includes selecting a first frequency based upon a first predetermined lookup table and the encoded character, and the transmitting a first transmitted acoustic tone at the first frequency. The encoding further includes selecting a second frequency based upon a second predetermined lookup table and the encoded character, and the transmitting a second transmitted acoustic tone at the second frequency. These methods also include decoding a decoded character with a decoding node of the plurality of nodes. The decoding includes receiving a first received acoustic tone, calculating a first frequency distribution for the first received acoustic tone, and determining a first decoded character distribution for the decoded character. The decoding also includes receiving a second received acoustic tone, calculating a second frequency distribution for the second received acoustic tone, and determining a second decoded character distribution for the decoded character. The decoding further includes identifying the decoded character based upon the first decoded character distribution and the second decoded character distribution.

[0006] In other embodiments, the methods include methods of determining a major frequency of a received acoustic tone transmitted via the tone transmission medium. These methods include receiving a received acoustic tone for a tone receipt time and estimating a frequency of the received acoustic tone. These methods also include separating the tone receipt time into a plurality of time intervals and calculating a frequency variation within each of the time intervals. These methods further include selecting a subset of the plurality of time intervals within which the frequency variation is less than a threshold frequency variation and averaging a plurality of discrete frequency values within the subset of the plurality of time intervals to determine the major frequency of the received acoustic tone.

[0007] In other embodiments, the methods include methods of conserving power in the acoustic wireless network. These methods include repeatedly and sequentially cycling a given node of the plurality of nodes for a plurality of cycles by entering a lower power state for a lower power state duration and subsequently transitioning to a listening state for a listening state duration. The low-power state duration is greater than the listening state duration. These methods also include transmitting, during the cycling and via a tone transmission medium, a transmitted acoustic tone for a tone transmission duration, receiving a received acoustic tone, and, responsive to the receiving, interrupting the cycling by transitioning the given node to an active state. The tone transmission duration is greater than the low-power state duration such that the acoustic wireless network detects the transmitted acoustic tone regardless of when the transmitting is initiated. Brief Description of the Drawings

[0008] Fig. 1 is a schematic representation of a well configured to utilize the methods according to the present disclosure.

[0009] Fig. 2 is a flowchart depicting methods, according to the present disclosure, of communicating in an acoustic wireless network that is spectrum-constrained.

[0010] Fig. 3 is a flowchart depicting methods, according to the present disclosure, of encoding an encoded character.

[0011] Fig. 4 is a flowchart depicting methods, according to the present disclosure, of decoding a decoded character.

[0012] Fig. 5 is an example of a first predetermined lookup table that may be utilized with the methods according to the present disclosure.

[0013] Fig. 6 is an example of a second predetermined lookup table that may be utilized with the methods according to the present disclosure.

[0014] Fig. 7 is an example of a plurality of encoded characters and a corresponding plurality of frequencies that may be utilized to convey the encoded characters.

[0015] Fig. 8 is an example of a plurality of encoded characters and a corresponding plurality of frequencies that may be utilized to convey the encoded characters.

[0016] Fig. 9 is a flowchart depicting methods, according to the present disclosure, of determining a major frequency of a received acoustic tone.

[0017] Fig. 10 is a plot illustrating a received amplitude of a plurality of received acoustic tones as a function of time.

[0018] Fig. 11 is a plot illustrating a received amplitude of an acoustic tone from Fig. 10.

[0019] Fig. 12 is a plot illustrating frequency variation in the received acoustic tone of Fig. 11.

[0020] Fig. 13 is a table illustrating histogram data that may be utilized to determine the major frequency of the received acoustic tone of Figs. 11-12.

[0021] Fig. 14 is a table illustrating a mechanism, according to the present disclosure, by which the major frequency of the acoustic tone of Figs. 11-12 may be selected.

[0022] Fig. 15 is a flowchart depicting methods, according to the present disclosure, of conserving power in an acoustic wireless network.

[0023] Fig. 16 is a schematic illustration of the method of Fig. 15.

Detailed Description and Best Mode of the Disclosure

[0024] Figs. 1-16 provide examples of methods 200, 300, and/or 400, according to the present disclosure, and/or of wells 20 including acoustic wireless networks 50 that may include and/or utilize the methods. Elements that serve a similar, or at least substantially similar, purpose are labeled with like numbers in each of Figs. 1 -16, and these elements may not be discussed in detail herein with reference to each of Figs. 1 -16. Similarly, all elements may not be labeled in each of Figs. 1-16, but reference numerals associated therewith may be utilized herein for consistency. Elements, components, and/or features that are discussed herein with reference to one or more of Figs. 1 -16 may be included in and/or utilized with any of Figs. 1 - 16 without departing from the scope of the present disclosure. In general, elements that are likely to be included in a particular embodiment are illustrated in solid lines, while elements that are optional are illustrated in dashed lines. However, elements that are shown in solid lines may not be essential and, in some embodiments, may be omitted without departing from the scope of the present disclosure.

[0025] Fig. 1 is a schematic representation of a well 20 configured to utilize methods 200, 300, and/or 400 according to the present disclosure. Well 20 includes a wellbore 30 that extends within a subsurface region 90. Wellbore 30 also may be referred to herein as extending between a surface region 80 and subsurface region 90 and/or as extending within a subterranean formation 92 that extends within the subsurface region. Subterranean formation 92 may include a hydrocarbon 94. Under these conditions, well 20 also may be referred to herein as, or may be, a hydrocarbon well 20, a production well 20, and/or an injection well 20.

[0026] Well 20 also includes an acoustic wireless network 50. The acoustic wireless network also may be referred to herein as a downhole acoustic wireless network 50 and includes a plurality of nodes 60, which are spaced-apart along a tone transmission medium 100 that extends along a length of wellbore 30. In the context of well 20, tone transmission medium 100 may include a downhole tubular 40 that may extend within wellbore 30, a wellbore fluid 32 that may extend within wellbore 30, a portion of subsurface region 90 that is proximal wellbore 30, a portion of subterranean formation 92 that is proximal wellbore 30, and/or a cement 34 that may extend within wellbore 30 and/or that may extend within an annular region between wellbore 30 and downhole tubular 40. Downhole tubular 40 may define a fluid conduit 44.

[0027] Nodes 60 may include one or more encoding nodes 62, which may be configured to generate an acoustic tone 70 and/or to induce the acoustic tone within tone transmission medium 100. Nodes 60 also may include one or more decoding nodes 64, which may be configured to receive acoustic tone 70 from the tone transmission medium. A given node 60 may function as both an encoding node 62 and a decoding node 64 depending upon whether the given node is transmitting an acoustic tone (i.e., functioning as the encoding node) or receiving the acoustic tone (i.e., functioning as the decoding node). Stated another way, the given node may include both encoding and decoding functionality, or structures, with these structures being selectively utilized depending upon whether or not the given node is encoding the acoustic tone or decoding the acoustic tone.

[0028] In wells 20, transmission of acoustic tone 70 may be along a length of wellbore 30. As such, the transmission of the acoustic tone may be linear, at least substantially linear, and/or directed, such as by tone transmission medium 100. Such a configuration may be in contrast to more conventional wireless communication methodologies, which generally may transmit a corresponding wireless signal in a plurality of directions, or even in every direction.

[0029] As illustrated in Fig. 1, acoustic wireless network 50 may include nodes 60 that are positioned within wellbore 30. As such, these nodes may be inaccessible, or at least difficult to access. Thus, limiting power consumption, as is discussed herein with reference to methods 400 of Figs. 15-16, may be important to the operation and/or longevity of the acoustic wireless network.

[0030] Method 200, 300, and/or 400, which are discussed in more detail herein, are disclosed in the context of well 20, such as a hydrocarbon well. However, it is within the scope of the present disclosure that these methods may be utilized to communicate via an acoustic tone, such as described in methods 200 of Figs. 2-8, to determine a major frequency of a received acoustic tone, such as described in methods 300 of Figs. 9-14, and/or to conserve power, such as described in methods 300 of Figs. 15-16, in any suitable acoustic wireless network. As examples, methods 200, 300, and/or 400 may be utilized with a corresponding acoustic wireless network in the context of a subsea well and/or in the context of a subsea tubular that extends within a subsea environment. Under these conditions, the tone transmission medium may include, or be, the subsea tubular and/or a subsea fluid that extends within the subsea environment, proximal the subsea tubular, and/or within the subsea tubular. As another example, methods 200, 300 and/or 400 may be utilized with a corresponding acoustic wireless network in the context of a surface tubular that extends within the surface region. Under these conditions, the tone transmission medium may include, or be, the surface tubular and/or a fluid that extends within the surface region, proximal the surface tubular, and/or within the surface tubular.

[0031] Fig. 2 is a flowchart depicting methods 200, according to the present disclosure, of communicating in an acoustic wireless network that is spectrum-constrained. The acoustic wireless network includes a plurality of nodes spaced-apart along a length of a tone transmission medium. Examples of the acoustic wireless network are disclosed herein with reference to acoustic wireless network 50 of Fig. 1. Examples of the tone transmission medium are disclosed herein with reference to tone transmission medium 100 of Fig. 1.

[0032] With the above in mind, methods 200 may include establishing predetermined lookup tables at 210 and include encoding an encoded character at 220, which is illustrated in more detail in Fig. 3. Methods 200 further may include conveying an acoustic tone at 230 and include decoding a decoded character at 240, which is illustrated in more detail in Fig. 4. Methods 200 also may include repeating at least a portion of the methods at 280, and Figs. 5- 8 provide schematic examples of various steps of methods 200.

[0033] During operation of an acoustic wireless network, such as acoustic wireless network 50 of Fig. 1, methods 200 may be utilized to transmit and/or convey one or more characters and/or pieces of information along, or along the length of, the tone transmission medium. As an example, and as discussed in more detail herein, a first predetermined lookup table 201 , as illustrated in Fig. 5, and a second predetermined lookup table 202, as illustrated in Fig. 6, may correlate a plurality of characters, or encoded characters, (e.g., characters A-Q in Figs. 5-6) to a plurality of frequencies, or frequency ranges (e.g., frequencies Fi-Fn in Figs. 5-6). Under these conditions, a character, such as a "P," may be selected for transmission along the length of the tone transmission medium, and methods 200 may be utilized to encode this character into a corresponding frequency and subsequently to decode this character from the corresponding frequency. In the example of Figs. 5-6, the "P" corresponds to Fi6 in first predetermined lookup table 201 and to Fs in second predetermined lookup table 202. Thus, the encoding at 220 may include transmitting frequency Fi6, via the tone transmission medium and with an encoding node, and subsequently transmitting frequency Fs, via the tone transmission medium and with the encoding node, as illustrated in Fig. 7. The decoding at 240 then may include receiving frequency Fi6 and subsequently receiving frequency Fs, with a decoding node and from the tone transmission medium, and utilizing first predetermined lookup table 201 and second predetermined lookup table 202, respectively, to decode the received frequencies into their corresponding character (e.g., Pi and P₂, as illustrated in Fig. 8). This process may be repeated any suitable number of times to transmit any suitable number of characters, or encoded characters, along the length of the tone transmission medium, as illustrated in Figs. 7-8 with the corresponding frequencies for transmission of the characters P-A-I-L.

[0034] Establishing predetermined lookup tables at 210 may include establishing any suitable predetermined lookup table. This may include establishing the first predetermined lookup table and the second predetermined lookup table, and these predetermined lookup tables may be utilized during the encoding at 220 and/or during the decoding at 240. With this in mind, the establishing at 210, when performed, may be performed prior to the encoding at 220 and/or prior to the decoding at 240.

[0035] The establishing at 210 may be accomplished in any suitable manner. As an example, the establishing at 210 may include obtaining the first predetermined lookup table and/or the second predetermined lookup table from any suitable source, such as from a database of lookup tables.

[0036] As another example, the establishing at 210 may include generating, or creating, the first predetermined lookup table and/or the second predetermined lookup table. This may include transmitting, at 212, a calibration signal via the tone transmission medium and with an encoding node of the plurality of nodes. This also may include receiving, at 214, the calibration signal from the tone transmission medium and with a decoding node of the plurality of nodes. This further may include determining, at 216, at least one acoustic characteristic of the tone transmission medium. The at least one characteristic of the tone transmission medium may be determined and/or quantified based, at least in part, on the transmitting at 212 and/or on the receiving at 214.

[0037] Under these conditions, the establishing at 210 may include establishing the predetermined lookup tables based, at least in part, on the at least one acoustic characteristic of the tone transmission medium. As a more specific example, the establishing at 210 may include determining a bandwidth for acoustic communication within the tone transmission medium. This may include determining a bandwidth, or frequency range, within which the tone transmission medium has less than a threshold ambient acoustic noise level and/or within which the transmitting at 212 and the receiving at 214 may be performed with less than a threshold loss in signal quality, in signal amplitude, and/or in signal intensity between the encoding node and the decoding node.

[0038] An example of first predetermined lookup table 201 is illustrated in Fig. 5, while an example of second predetermined lookup table 202 is illustrated in Fig. 6. As illustrated in Figs. 5-6, predetermined lookup tables 201 and 202 generally correlate a plurality of characters, or encoded characters, such as the letters A through Q that are illustrated in the first row of Figs. 5-6, with a corresponding plurality of frequencies, or frequency ranges, such as frequencies Fi-Fn that are illustrated in the second row of Figs. 5-6.

[0039] First predetermined lookup table 201 and second predetermined lookup table 202 differ from one another. More specifically, and as illustrated, the frequency that correlates to a given character differs between first predetermined lookup table 201 and second predetermined lookup table 202. Additionally or alternatively, the first predetermined lookup table and the second predetermined lookup table may be configured such that, for a given character, the corresponding first frequency, as established by first predetermined lookup table 201, is unequal to and/or not a harmonic of the corresponding second frequency, as established by second predetermined lookup table 202. Such a configuration may increase an accuracy of communication when the tone transmission medium transmits one frequency more effectively, with less noise, and/or with less attenuation than another frequency.

[0040] It is within the scope of the present disclosure that first predetermined lookup table 201 and second predetermined lookup table 202 may utilize the same encoded characters and the same frequencies, or frequency ranges. Under these conditions, a different frequency, or frequency range, may be correlated to each encoded character in first predetermined lookup table 201 when compared to second predetermined lookup table 202. Additionally or alternatively, it is also within the scope of the present disclosures that at least one frequency, or frequency range, may be included in one of the first predetermined lookup table and the second predetermined lookup table but not in the other lookup table.

[0041] The plurality of frequencies utilized in the first predetermined lookup table and in the second predetermined lookup table, including the first frequency and/or the second frequency, may have any suitable value and/or may be within any suitable frequency range. As examples, each frequency in the plurality of frequencies may be at least 10 kilohertz (kHz), at least 25 kHz, at least 50 kHz, at least 60 kHz, at least 70 kHz, at least 80 kHz, at least 90 kHz, at least 100 kHz, at least 200 kHz, at least 250 kHz, at least 400 kHz, at least 500 kHz, and/or at least 600 kHz. Additionally or alternatively, each frequency in the plurality of frequencies may be at most 1000 kHz (1 megahertz), at most 800 kHz, at most 600 kHz, at most 400 kHz, at most 200 kHz, at most 150 kHz, at most 100 kHz, and/or at most 80 kHz.

[0042] Encoding the encoded character at 220 may include encoding the encoded character with the encoding node. As illustrated in Fig. 3, the encoding at 220 includes selecting a first frequency for a first transmitted acoustic tone at 222, transmitting the first transmitted acoustic tone at 224, selecting a second frequency for a second transmitted acoustic tone at 226, and transmitting the second transmitted acoustic tone at 228.

[0043] Selecting the first frequency for the first transmitted acoustic tone at 222 may include selecting based, at least in part, on the encoded character. Additionally or alternatively, the selecting at 222 also may include selecting from the first predetermined lookup table. The first frequency may be correlated to the encoded character in the first predetermined lookup table. As an example, and with reference to Fig. 5, the first encoded character may be a "P," and the first frequency may be Fi6, as indicated in the leftmost box of Fig. 7. The first predetermined lookup table may provide a one-to-one correspondence between the first frequency and the encoded character. Stated another way, each encoded character, and each frequency, may be utilized once and only once in the first predetermined lookup table.

[0044] Transmitting the first transmitted acoustic tone at 224 may include transmitting the first transmitted acoustic tone at the first frequency. Additionally or alternatively, the transmitting at 224 also may include transmitting the first transmitted acoustic tone via and/or utilizing the tone transmission medium. The transmitting at 224 further may include transmitting for a first tone-transmission duration.

[0045] The transmitting at 224 may be accomplished in any suitable manner. As an example, the transmitting at 224 may include inducing the first acoustic tone, within the tone transmission medium, with an encoding node transmitter of the acoustic wireless network. Examples of the encoding node transmitter include any suitable structure configured to induce a vibration within the tone transmission medium, such as a piezoelectric encoding node transmitter, an electromagnetic acoustic transmitter, a resonant microelectromechanical system (MEMS) transmitter, a non-resonant MEMS transmitter, and/or a transmitter array.

[0046] Selecting the second frequency for the second transmitted acoustic tone at 226 may include selecting based, at least in part, on the encoded character. Additionally or alternatively, the selecting at 226 also may include selecting from the second predetermined lookup table. In general, the second predetermined lookup table is different from the first predetermined lookup table and/or the second frequency is different from the first frequency. The second frequency may be correlated to the encoded character in the second predetermined lookup table. As an example, and with reference to Fig. 6, the second frequency may be Fs when the encoded character is "P," as indicated in the leftmost box of Fig. 7. The second predetermined lookup table may provide a one-to-one correspondence between the second frequency and the encoded character. Stated another way, each encoded character, and each frequency, may be utilized once and only once in the second predetermined lookup table.

[0047] Transmitting the second transmitted acoustic tone at 228 may include transmitting the first transmitted acoustic tone at the second frequency. Additionally or alternatively, the transmitting at 228 also may include transmitting the second transmitted acoustic tone via and/or utilizing the tone transmission medium. The transmitting at 228 further may include transmitting for a second tone-transmission duration.

[0048] The transmitting at 228 may be accomplished in any suitable manner. As an example, the transmitting at 228 may include inducing the second acoustic tone, within the tone transmission medium, with the encoding node transmitter. [0049] Conveying the acoustic tone at 230 may include conveying in any suitable manner. As an example, the decoding node may be spaced-apart from the encoding node such that the tone transmission medium extends between, or spatially separates, the encoding node and the decoding node. Under these conditions, the conveying at 230 may include conveying the first transmitted acoustic tone and/or conveying the second transmitted acoustic tone, via the tone transmission medium, from the encoding node to the decoding node.

[0050] The conveying at 230 further may include modifying the first transmitted acoustic tone, via a first interaction with the tone transmission medium, to generate a first received acoustic tone. Additionally or alternatively, the conveying at 230 may include modifying the second transmitted acoustic tone, via a second interaction with the tone transmission medium, to generate a second received acoustic tone. The modifying may include modifying in any suitable manner and may be active (i.e., purposefully performed) or passive (i.e., inherently performed as a result of the conveying). Examples of the modifying include modification of one or more of an amplitude of the first and/or second transmitted acoustic tone, a phase of the first and/or second transmitted acoustic tone, a frequency of the first and/or second transmitted acoustic tone, and/or a wavelength of the first and/or second transmitted acoustic tone. Another example of the modifying includes introducing additional frequency components into the first and/or second transmitted acoustic tone. Examples of mechanisms that may produce and/or generate the modifying include tone reflections, ringing, and/or tone recombination at the encoding node, within the tone transmission medium, and/or at the decoding node.

[0051] Decoding the decoded character at 240 may include decoding with the decoding node. As illustrated in Fig. 4, the decoding at 240 includes receiving, at 242, the first received acoustic tone, calculating, at 244, a first frequency distribution, and determining, at 250, a first decoded character distribution. The decoding at 240 also includes receiving, at 258, a second received acoustic tone, calculating, at 262, a second frequency distribution, and determining, at 268, a second decoded character distribution. The decoding at 240 further includes identifying, at 274, the decoded character. The decoding at 240 additionally or alternatively may include performing any suitable portion of methods 300, which are discussed herein with reference to Figs. 9-14.

[0052] Receiving the first received acoustic tone at 242 may include receiving the first received acoustic tone with the decoding node and/or from the tone transmission medium and may be performed subsequent to, or responsive to, the transmitting at 224. The receiving at 242 may include receiving the first received acoustic tone for a first tone-receipt duration. [0053] The receiving at 242 may include receiving with any suitable decoding node that is configured to receive the first received acoustic tone from the tone transmission medium. As examples, the receiving at 242 may include receiving with, via, and/or utilizing a piezoelectric decoding node receiver, a piezoresistive receiver, a resonant MEMS receiver, a non-resonant MEMS receiver, and/or a receiver array.

[0054] Calculating the first frequency distribution at 244 may include calculating the first frequency distribution for, or of, the first received acoustic tone and may be accomplished in any suitable manner. As examples, the calculating at 244 may include performing a Fourier transform of the first received acoustic tone, performing a fast Fourier transform of the first received acoustic tone, performing a discrete Fourier transform of the first received acoustic tone, performing a wavelet transform of the first received acoustic tone, performing a multiple least squares analysis of the first received acoustic tone, and/or performing a polyhistogram analysis of the first received acoustic tone. Examples of the polyhistogram analysis are disclosed herein with reference to methods 300 of Fig. 9.

[0055] It is within the scope of the present disclosure that the first received acoustic tone may include a plurality of first frequency components. These first frequency components may be generated during the transmitting at 224, during the conveying at 230, and/or during the receiving at 242, and examples of mechanisms that may generate the first frequency components are discussed herein with reference to the conveying at 230.

[0056] When the first received acoustic tone includes the plurality of first frequency components, the calculating at 244 may include calculating, at 246, a relative magnitude of each of the plurality of first frequency components and/or calculating, at 248, a histogram of the plurality of first frequency components.

[0057] Determining the first decoded character distribution at 250 may include determining the first decoded character distribution from the first frequency distribution and/or from the first predetermined lookup table. As an example, the plurality of first frequency components, as calculated during the calculating at 244, may correspond to a plurality of first received characters within first predetermined lookup table 201 of Fig. 5. Stated another way, the determining at 250 may include determining which character from the first predetermined lookup table corresponds to each frequency component in the plurality of first frequency components.

[0058] Under these conditions, the determining at 250 may include calculating, at 252, a relative probability that the first received acoustic tone represents each first received character in the plurality of first received characters and/or calculating, at 254, a histogram of the plurality of first received characters. Additionally or alternatively, the determining at 250 may include mapping, at 256, each first frequency component in the plurality of first frequency components to a corresponding character in the first predetermined lookup table.

[0059] Receiving the second received acoustic tone at 258 may include receiving the second received acoustic tone with the decoding node and/or from the tone transmission medium and may be performed subsequent, or responsive, to the transmitting at 228. The receiving at 258 may include receiving the second received acoustic tone for a second tone- receipt duration.

[0060] Calculating the second frequency distribution at 262 may include calculating the second frequency distribution for, or of, the second received acoustic tone and may be accomplished in any suitable manner. As examples, the calculating at 260 may include performing a Fourier transform of the second received acoustic tone, performing a fast Fourier transform of the second received acoustic tone, performing a discrete Fourier transform of the second received acoustic tone, performing a wavelet transform of the second received acoustic tone, performing a multiple least squares analysis of the second received acoustic tone, and/or performing a polyhistogram analysis of the second received acoustic tone. Examples of the polyhistogram analysis are disclosed herein with reference to methods 300 of Fig. 9.

[0061] Similar to the first received acoustic tone, the second received acoustic tone may include a plurality of second frequency components. These second frequency components may be generated during the transmitting at 228, during the conveying at 230, and/or during the receiving at 258, as discussed herein with reference to the calculating at 244.

[0062] When the second received acoustic tone includes the plurality of second frequency components, the calculating at 260 may include calculating, at 262, a relative magnitude of each of the plurality of second frequency components and/or calculating, at 264, a histogram of the plurality of second frequency components.

[0063] Determining the second decoded character distribution at 268 may include determining the second decoded character distribution from the second frequency distribution and/or from the second predetermined lookup table. As an example, the plurality of second frequency components, as calculated during the calculating at 260, may correspond to a plurality of second received characters within second predetermined lookup table 202 of Fig. 6. Stated another way, the determining at 266 may include determining which character from the second predetermined lookup table corresponds to each frequency component in the plurality of second frequency components. [0064] Under these conditions, the determining at 266 may include calculating, at 268, a relative probability that the second received acoustic tone represents each second received character in the plurality of second received characters and/or calculating, at 270, a histogram of the plurality of second received characters. Additionally or alternatively, the determining at 266 may include mapping, at 272, each second frequency component in the plurality of second frequency components to a corresponding character in the second predetermined lookup table.

[0065] Identifying the decoded character at 274 may include identifying the decoded character based, at least in part, on the first decoded character distribution and the second decoded character distribution. The identifying at 274 may be accomplished in any suitable manner. As an example, the identifying at 274 may include identifying which character in the first decoded character distribution has the highest probability of being the encoded character and/or identifying which character in the second decoded character distribution has the highest probability of being the encoded character.

[0066] As a more specific example, the identifying at 274 may include combining the first decoded character distribution with the second decoded character distribution to produce and/or generate a composite decoded character distribution and identifying, as indicated at 276, the highest probability character from the composite decoded character distribution. The first decoded character distribution and the second decoded character distribution may be combined in any suitable manner. As an example, the first decoded character distribution and the second decoded character distribution may be summed. As another example, the first decoded character distribution and the second decoded character distribution may be combined utilizing a one-and-one-half moment method. As another more specific example, and as indicated in Fig. 4 at 278, the identifying at 274 may include selecting a most common character from the first decoded character distribution and from the second decoded character distribution.

[0067] Repeating at least the portion of the methods at 280 may include repeating any suitable portion of methods 200 in any suitable order. As an example, the encoding node may be a first node of the plurality of nodes, and the decoding node may be a second node of the plurality of nodes. Under these conditions, the repeating at 280 may include repeating the encoding at 220 with the second node and repeating the decoding at 240 with a third node of the plurality of nodes, such as to transmit the encoded character along the length of the tone transmission medium. This process may be repeated a plurality of times to propagate the encoded character among the plurality of spaced-apart nodes. The third node may be spaced- apart from the second node and/or from the first node. Additionally or alternatively, the second node may be positioned between the first node and the third node along the length of the tone transmission medium.

[0068] As another example, the encoded character may be a first encoded character, and the decoded character may be a first decoded character. Under these conditions, the repeating at 280 may include repeating the encoding at 220 to encode a second encoded character and repeating the decoding at 240 to decode a second decoded character. This is illustrated in Figs. 7-8, wherein the characters P-A-I-L sequentially are encoded, as illustrated in Fig. 7, utilizing corresponding frequencies from the first and second predetermined lookup tables of Figs. 5 and 6. The characters subsequently are decoded, as illustrated in Fig. 8, by comparing the received frequencies to the frequencies from the first and second predetermined lookup tables.

[0069] Methods 200 have been described herein as utilizing two predetermined lookup tables (e.g., first predetermined lookup table 201 of Fig. 5 and second predetermined lookup table 202 of Fig. 6). However, it is within the scope of the present disclosure that methods 200 may include and/or utilize any suitable number of frequencies, and corresponding predetermined lookup tables, for a given encoded character. As examples, the encoding at 220 may include selecting a plurality of frequencies for a plurality of transmitted acoustic tones from a corresponding plurality of lookup tables and transmitting the plurality of transmitted acoustic tones via the tone transmission medium. As additional examples, the decoding at 240 may include receiving a plurality of received acoustic tones, calculating a plurality of frequency distributions from the plurality of received acoustic tones, determining, from the plurality of frequency distributions and the plurality of predetermined lookup tables, a plurality of decoded character distributions, and identifying the decoded character based, at least in part, on the plurality of decoded character distributions. The plurality of decoded character distributions may include any suitable number of decoded character distributions, including at least 3, at least 4, at least 6, at least 8, or at least 10 decoded character distributions.

[0070] It is within the scope of the present disclosure that methods 200 may be performed utilizing any suitable tone transmission medium and/or in any suitable environment and/or context, including those that are disclosed herein. As an example, and when methods 200 are performed within a well, such as well 20 of Fig. 1 , methods 200 further may include drilling wellbore 30. Stated another way, methods 200 may be performed while the wellbore is being formed, defined, and/or drilled. As another example, methods 200 further may include producing a reservoir fluid from subterranean formation 92. Stated another way, methods 200 may be performed while the reservoir fluid is being produced from the subterranean formation. [0071] As discussed herein, the encoding at 220 and/or the decoding at 240 may utilize predetermined lookup tables, such as first predetermined lookup table 201 and/or second predetermined lookup table 202, to map predetermined frequencies, or frequency ranges, to predetermined characters, or encoded characters. As such, methods 200 may be performed without, without utilizing, and/or without the use of a random, or pseudorandom, number generator.

[0072] Fig. 9 is a flowchart depicting methods 300, according to the present disclosure, of determining a major frequency of a received acoustic tone that is transmitted via a tone transmission medium, while Figs. 10-14 illustrate various steps that may be performed during methods 300. Methods 300 may be performed utilizing any suitable structure and/or structures. As an example, methods 300 may be utilized by an acoustic wireless network, such as acoustic wireless network 50 of Fig. 1. Under these conditions, methods 300 may be utilized to communicate along a length of wellbore 30.

[0073] Methods 300 include receiving a received acoustic tone at 310, estimating a frequency of the received acoustic tone at 320, and separating a tone receipt time into a plurality of time intervals at 330. Methods 300 also include calculating a frequency variation at 340, selecting a subset of the plurality of time intervals at 350, and averaging a plurality of discrete frequency values at 360. Methods 300 further may include transmitting a transmitted acoustic tone at 370.

[0074] Receiving the received acoustic tone at 310 may include receiving with a decoding node of an acoustic wireless network. Additionally or alternatively, the receiving at 310 may include receiving from the tone transmission medium and/or receiving for a tone receipt time. The receiving at 310 may include receiving for any suitable tone receipt time. As examples, the tone receipt time may be at least 1 microsecond, at least 10 microseconds, at least 25 microseconds, at least 50 microseconds, at least 75 microseconds, or at least 100 microseconds. The receiving at 310 also may include receiving at any suitable frequency, or tone frequency. Examples of the tone frequency include frequencies of at least 10 kilohertz (kHz), at least 25 kHz, at least 50 kHz, at least 60 kHz, at least 70 kHz, at least 80 kHz, at least 90 kHz, at least 100 kHz, at least 200 kHz, at least 250 kHz, at least 400 kHz, at least 500 kHz, and/or at least 600 kHz. Additionally or alternatively, the tone frequency may be at most 1 megahertz (MHz), at most 800 kHz, at most 600 kHz, at most 400 kHz, at most 200 kHz, at most 150 kHz, at most 100 kHz, and/or at most 80 kHz.

[0075] The receiving at 310 may include receiving with any suitable decoding node, such as decoding node 64 of Fig. 1. Additionally or alternatively, the receiving at 310 may include receiving with an acoustic tone receiver. Examples of the acoustic tone receiver include a piezoelectric tone receiver, a piezoresistive tone receiver, a resonant MEMS tone receiver, a non-resonant MEMS tone receiver, and/or a receiver array.

[0076] An example of a plurality of received acoustic tones is illustrated in Fig. 10, while an example of a single received acoustic tone is illustrated in Fig. 1 1. Figs. 10-1 1 both illustrate amplitude of the received acoustic tone as a function of time (e.g., the tone receipt time). As illustrated in Figs. 10-11, the amplitude of the received acoustic tone may vary significantly during the tone receipt time. This variation may be caused by non-idealities within the tone transmission medium and/or with the tone transmission process. Examples of these non- idealities are discussed herein and include acoustic tone reflection points within the tone transmission medium, generation of harmonics during the tone transmission process, ringing within the tone transmission medium, and/or variations in a velocity of the acoustic tone within the tone transmission medium. Collectively, these non-idealities may make it challenging to determine, to accurately determine, and/or to reproducibly determine the major frequency of the received acoustic tone, and methods 300 may facilitate this determination.

[0077] Estimating the frequency of the received acoustic tone at 320 may include estimating the frequency of the received acoustic tone as a function of time and/or during the tone receipt time. This may include estimating a plurality of discrete frequency values received at a corresponding plurality of discrete times within the tone receipt time and may be accomplished in any suitable manner.

[0078] As an example, the received acoustic tone may include, or be, a received acoustic wave that has a time-varying amplitude within the tone receipt time, as illustrated in Figs. 10- 11. The time-varying amplitude may define an average amplitude, and the estimating at 320 may include measuring a cycle time between the time-varying amplitude and the average amplitude, measuring a period of individual cycles of the received acoustic wave, and/or measuring a plurality of zero-crossing times of the received acoustic wave.

[0079] The estimating at 320 may be utilized to generate a dataset that represents the frequency of the received acoustic tone as a function of time during the tone receipt time. An example of such a dataset is illustrated in Fig. 12. As may be seen in Fig. 12, the frequency of the received acoustic tone includes time regions where there is a relatively higher amount of variation, such as the time regions from To to Ti and from T2 to T3 in Fig. 12, and a time region where there is a relatively lower amount of variation, such as time region from Ti to T2 in Fig. 12. [0080] Separating the tone receipt time into the plurality of time intervals at 330 may include separating such that each time interval in the plurality of time intervals includes a subset of the plurality of discrete frequency values that was received and/or determined during that time interval. It is within the scope of the present disclosure that each time interval in the plurality of time intervals may be less than a threshold fraction of the tone receipt time. Examples of the threshold fraction of the tone receipt time include threshold fractions of less than 20%, less than 15%, less than 10%, less than 5%, or less than 1 %. Stated another way, the separating at 330 may include separating the tone receipt time into at least a threshold number of time intervals. Examples of the threshold number of time intervals includes at least 5, at least 7, at least 10, at least 20, or at least 100 time intervals. It is within the scope of the present disclosure that a duration of each time interval in the plurality of time intervals may be the same, or at least substantially the same, as a duration of each other time interval in the plurality of time intervals. However, this is not required to all implementations, and the duration of one or more time interval in the plurality of time intervals may differ from the duration of one or more other time intervals in the plurality of time intervals.

[0081] Calculating the frequency variation at 340 may include calculating any suitable frequency variation within each time interval and/or within each subset of the plurality of discrete frequency values. The calculating at 340 may be performed in any suitable manner and/or may calculate any suitable measure of variation, or frequency variation. As an example, the calculating at 340 may include calculating a statistical parameter indicative of variability within each subset of the plurality of discrete frequency values. As another example, the calculating at 340 may include calculating a frequency range within each subset of the plurality of discrete frequency values. As yet another example, the calculating at 340 may include calculating a frequency standard deviation of, or within, each subset of the plurality of discrete frequency values. As another example, the calculating at 340 may include scoring each subset of the plurality of discrete frequency values.

[0082] As yet another example, the calculating at 340 may include assessing a margin, or assessing the distinctiveness of a given frequency in a given time interval relative to the other frequencies detected during the given time interval. This may include utilizing a magnitude and/or a probability density to assess the distinctiveness and/or utilizing a difference between a magnitude of a most common histogram element and a second most common histogram element within the given time interval to assess the distinctiveness.

[0083] As a more specific example, and when the calculating at 340 includes calculating the frequency range, the calculating at 340 may include binning, or separating, each subset of the plurality of discrete frequency values into bins. This is illustrated in Fig. 13. Therein, a number of times that a given frequency (i.e., represented by bins 1-14) is observed within a given time interval (i.e., represented by time intervals 1-10) is tabulated. A zero value for a given frequency bin-time interval combination indicates that the given frequency bin was not observed during the given time interval, while a non-zero number indicates the number of times that the given frequency bin was observed during the given time interval.

[0084] Under these conditions, the calculating at 340 may include determining a span, or range, of the frequency bins. In the example of Fig. 13, the uppermost bin that includes at least one count is bin 14, while the lowermost bin that includes at least one count is bin 11. Thus, the span, or range, is 4, as indicated.

[0085] Selecting the subset of the plurality of time intervals at 350 may include selecting a subset within which the frequency variation, as determined during the calculating at 340, is less than a threshold frequency variation. Experimental data suggests that time intervals within which the frequency variation is less than the threshold frequency variation represent time intervals that are more representative of the major frequency of the received acoustic tone. As such, the selecting at 350 includes selectively determining which time intervals are more representative of, or more likely to include, the major frequency of the received acoustic tone, thereby decreasing noise in the overall determination of the major frequency of the received acoustic tone.

[0086] The selecting at 350 may include selecting a continuous range within the tone receipt time or selecting two or more ranges that are spaced-apart in time within the tone receipt time. Additionally or altematively, the selecting at 350 may include selecting at least 2, at least 3, at least 4, or at least 5 time intervals from the plurality of time intervals.

[0087] The selecting at 350 additionally or alternatively may include selecting such that the frequency variation within each successive subset of the plurality of discrete frequency values decreases relative to a prior subset of the plurality of discrete frequency values and/or remains unchanged relative to the prior subset of the plurality of discrete frequency values.

[0088] An example of the selecting at 350 is illustrated in Fig. 13. In this example, time intervals with a span of less than 10 are selected and highlighted in the table. These include time intervals 1, 4, and 5.

[0089] Averaging the plurality of discrete frequency values at 360 may include averaging within the subset of the plurality of time intervals that was selected during the selecting at 350 and/or averaging to determine the major frequency of the received acoustic tone. The averaging at 360 may be accomplished in any suitable manner. As an example, the averaging at 360 may include calculating a statistical parameter indicative of an average of the plurality of discrete frequency values within the subset of the plurality of time intervals. As another example, the averaging at 360 may include calculating a mean, median, or mode value of the plurality of discrete frequency values within the subset of the plurality of time intervals.

[0090] As a more specific example, and with reference to Figs. 13-14, the averaging at 360 may include summing the bins for the time intervals that were selected during the selecting at 350. As discussed, and utilizing one criteria for the selecting at 350, bins 1 , 4, and 5 from Fig. 13 may be selected. The number of counts in these three bins then may be summed to arrive at Fig. 14, and the bin with the most counts, which represents the most common, or mode, frequency of the selected time intervals, may be selected. In the example of Fig. 14, this may include selecting bin 12, or the frequency of bin 12, as the major frequency of the received acoustic tone.

[0091] Transmitting the transmitted acoustic tone at 370 may include transmitting with an encoding node of the acoustic wireless network. The transmitting at 370 may be subsequent, or responsive, to the averaging at 360; and a transmitted frequency of the transmitted acoustic tone may be based, at least in part, on, or equal to, the major frequency of the received acoustic tone. Stated another way, the transmitting at 370 may include repeating, or propagating, the major frequency of the received acoustic tone along the length of the tone transmission medium, such as to permit and/or facilitate communication along the length of the tone transmission medium.

[0092] Fig. 15 is a flowchart depicting methods 400, according to the present disclosure, of conserving power in an acoustic wireless network including a plurality of nodes, while Fig. 16 is a schematic illustration of an example of the method of Fig. 15. As illustrated in Fig. 15, methods 400 include repeatedly and sequentially cycling a given node at 410, transmitting a transmitted acoustic tone at 420, receiving a received acoustic tone at 430, and interrupting the cycling for a threshold tone-receipt duration at 440. Methods 400 further may include remaining in an active state for the threshold tone-receipt duration at 450 and/or repeating at least a portion of the methods at 460.

[0093] Methods 400 may be performed by an acoustic wireless network, such as acoustic wireless network 50 of Fig. 1. In such a network, at least one node 60 of the plurality of nodes 60 is programmed to perform the cycling at 410 and the receiving at 430, and an adjacent node 60 of the plurality of nodes is programmed to perform the transmitting at 420.

[0094] Repeatedly and sequentially cycling the given node at 410 may include cycling the given node for a plurality of cycles. Each cycle in the plurality of cycles includes entering, for a low-power state duration, a low-power state in which the given node is inactive, as indicated at 412. Each cycle in the plurality of cycles further includes subsequently transitioning, for a listening state duration, to a listening state in which a receiver of the given node listens for a received acoustic tone from a tone transmission medium, as indicated at 414.

[0095] In general, the low-power state duration is greater than the listening state duration. As examples, the low-power state duration may be at least 2, at least 3, at least 4, at least 6, at least 8, or at least 10 times greater than the listening state duration. As such, the given node may conserve power when compared to a node that might remain in the listening state indefinitely.

[0096] An example of the cycling at 410 is illustrated in Fig. 16, which illustrates the state of the given node as a function of time. As illustrated beginning on the leftmost side of Fig. 16, the given node remains in a low-power state 480 for a low power state duration 481 and subsequently transitions to a listening state 482 for a listening state duration 483. As also illustrated, the given node repeatedly cycles between the low-power state and the listening state. Each cycle defines a cycle duration 486, which is a sum of low-power state duration 481 and listening state duration 483.

[0097] It is within the scope of the present disclosure that the given node may have, or include, an internal clock. The internal clock, when present, may have and/or exhibit a low- power clock rate when the given node is in the low-power state, a listening clock rate when the given node is in the listening state, and an active clock rate when the given node is in the active state. The low-power clock rate may be less than the listening clock rate, thereby permitting the given node to conserve power when in the low-power state. In addition, the listening clock rate may be less than the active clock rate, thereby permitting the given node to conserve power in the listening state when compared to the active state. It is within the scope of the present disclosure that the listening clock rate may be sufficient to detect, or detect the presence of, the received acoustic tone but insufficient to resolve, or to determine a frequency of, the received acoustic tone. In contrast, the active clock rate may be sufficient to resolve, or detect the frequency of, the received acoustic tone.

[0098] Transmitting the transmitted acoustic tone at 420 may include transmitting during the cycling at 410 and/or transmitting via the tone transmission medium. The transmitting at 420 further may include transmitting for a tone transmission duration, and the tone transmission duration is greater than the low-power state duration of the given node. As examples, the tone transmission duration may be at least 110%, at least 120%, at least 150%, at least 200%, or at least 300% of the low-power state duration. Additionally or alternatively, the tone transmission duration may be at least as large as, or even greater than, the cycle duration. Examples of the tone transmission duration include durations of at least 1 millisecond (ms), at least 2 ms, at least 4 ms, at least 6 ms, at least 8 ms, or at least 10 ms.

[0099] The transmitting at 420 may be accomplished in any suitable manner. As an example, the transmitting at 420 may include transmitting with a transmitter of another node of the plurality of nodes. The other node of the plurality of nodes may be different from and/or spaced-apart from the given node of the plurality of nodes. Stated another way, the tone transmission medium may extend between, or spatially separate, the given node and the other node.

[00100] The transmitting at 420 is illustrated in Fig. 16. As illustrated therein, the transmitter output may include a time period 490 in which there is no transmitted acoustic tone. In addition, the transmitter output also may include a time period 492 in which the transmitter transmits the transmitted acoustic tone for a tone transmission duration 493. Since tone transmission duration 493 is greater than low-power state duration 481 , the given node must be in listening state 482 for at least a portion of tone transmission duration 493 regardless of when transmission of the acoustic tone is initiated by the transmitter. As such, the given node cycles between low-power state 480 and listening state 482, thereby conserving power, while, at the same time, always being available to detect, or hear, the transmitted acoustic tone.

[00101] Receiving the received acoustic tone at 430 may include receiving during the listening state of a given cycle of the plurality of cycles and with the given node. The receiving at 430 further may include receiving from the tone transmission medium and/or with the receiver of the given node and may be subsequent, or responsive, to the transmitting at 420.

[00102] Interrupting the cycling for the threshold tone-receipt duration at 440 may include transitioning the given node to the active state for at least a threshold active state duration and may be subsequent, or responsive, to the receiving at 430. This is illustrated in Fig. 16, with the given node transitioning to an active state 484 and remaining in the active state for a threshold active state duration 485 responsive to the receiving at 430.

[00103] The threshold active state duration may be greater than the low-power state duration. As examples, the threshold active state duration may be at least 1.5, at least 2, at least 2.5, at least 3, at least 4, or at least 5 times larger than the low-power state duration, and the interrupting at 440 may permit the given node to receive one or more subsequent transmitted acoustic tones in succession. As an example, the transmitted acoustic tone may be a first transmitted acoustic tone and the method may include transmitting a plurality of transmitted acoustic tones separated by a plurality of pauses, or time periods 490 in which no acoustic tone is transmitted. Each pause may have a pause duration 494, and the interrupting at 440 may include remaining in the active state responsive to the pause duration being less than the threshold active state duration.

[00104] Repeating at least the portion of the methods at 460 may include repeating any suitable portion of methods 400 in any suitable manner. As an example, and responsive to not receiving an acoustic tone for the threshold active state duration, the repeating at 460 may include returning to the cycling at 410, thereby conserving power while permitting the given node to detect a subsequent acoustic tone, which might be received from the tone transmission medium subsequent to the given node returning to the cycling at 410.

[00105] The acoustic wireless network and/or the nodes thereof, which are disclosed herein, including acoustic wireless network 50 and/or nodes 60 of Fig. 1 , may include and/or be any suitable structure, device, and/or devices that may be adapted, configured, designed, constructed, and/or programmed to perform the functions discussed herein with reference to methods 200, 300, and/or 400. As examples, the acoustic wireless network and/or the associated nodes may include one or more of an electronic controller, a dedicated controller, a special-purpose controller, a special-purpose computer, a display device, a logic device, a memory device, and/or a memory device having computer-readable storage media.

[00106] The computer-readable storage media, when present, also may be referred to herein as non-transitory computer readable storage media. This non-transitory computer readable storage media may include, define, house, and/or store computer-executable instructions, programs, and/or code; and these computer-executable instructions may direct the acoustic wireless network and/or the nodes thereof to perform any suitable portion, or subset, of methods 200, 300, and/or 400. Examples of such non-transitory computer-readable storage media include CD-ROMs, disks, hard drives, flash memory, etc. As used herein, storage, or memory, devices and/or media having computer-executable instructions, as well as computer- implemented methods and other methods according to the present disclosure, are considered to be within the scope of subject matter deemed patentable in accordance with Section 101 of Title 35 of the United States Code.

[00107] In the present disclosure, several of the illustrative, non-exclusive examples have been discussed and/or presented in the context of flow diagrams, or flow charts, in which the methods are shown and described as a series of blocks, or steps. Unless specifically set forth in the accompanying description, it is within the scope of the present disclosure that the order of the blocks may vary from the illustrated order in the flow diagram, including with two or more of the blocks (or steps) occurring in a different order and/or concurrently. It is also within the scope of the present disclosure that the blocks, or steps, may be implemented as logic, which also may be described as implementing the blocks, or steps, as logics. In some applications, the blocks, or steps, may represent expressions and/or actions to be performed by functionally equivalent circuits or other logic devices. The illustrated blocks may, but are not required to, represent executable instructions that cause a computer, processor, and/or other logic device to respond, to perform an action, to change states, to generate an output or display, and/or to make decisions.

[00108] As used herein, the term "and/or" placed between a first entity and a second entity means one of (1) the first entity, (2) the second entity, and (3) the first entity and the second entity. Multiple entities listed with "and/or" should be construed in the same manner, i.e., "one or more" of the entities so conjoined. Other entities may optionally be present other than the entities specifically identified by the "and/or" clause, whether related or unrelated to those entities specifically identified. Thus, as a non-limiting example, a reference to "A and/or B," when used in conjunction with open-ended language such as "comprising" may refer, in one embodiment, to A only (optionally including entities other than B); in another embodiment, to B only (optionally including entities other than A); in yet another embodiment, to both A and B (optionally including other entities). These entities may refer to elements, actions, structures, steps, operations, values, and the like.

[00109] As used herein, the phrase "at least one," in reference to a list of one or more entities should be understood to mean at least one entity selected from any one or more of the entity in the list of entities, but not necessarily including at least one of each and every entity specifically listed within the list of entities and not excluding any combinations of entities in the list of entities. This definition also allows that entities may optionally be present other than the entities specifically identified within the list of entities to which the phrase "at least one" refers, whether related or unrelated to those entities specifically identified. Thus, as a non-limiting example, "at least one of A and B" (or, equivalently, "at least one of A or B," or, equivalently "at least one of A and/or B") may refer, in one embodiment, to at least one, optionally including more than one, A, with no B present (and optionally including entities other than B); in another embodiment, to at least one, optionally including more than one, B, with no A present (and optionally including entities other than A); in yet another embodiment, to at least one, optionally including more than one, A, and at least one, optionally including more than one, B (and optionally including other entities). In other words, the phrases "at least one," "one or more," and "and/or" are open-ended expressions that are both conjunctive and disjunctive in operation. For example, each of the expressions "at least one of A, B and C," "at least one of A, B, or C," "one or more of A, B, and C," "one or more of A, B, or C" and "A, B, and/or C" may mean A alone, B alone, C alone, A and B together, A and C together, B and C together, A, B and C together, and optionally any of the above in combination with at least one other entity.

[00110] In the event that any patents, patent applications, or other references are incorporated by reference herein and (1) define a term in a manner that is inconsistent with and/or (2) are otherwise inconsistent with, either the non-incorporated portion of the present disclosure or any of the other incorporated references, the non-incorporated portion of the present disclosure shall control, and the term or incorporated disclosure therein shall only control with respect to the reference in which the term is defined and/or the incorporated disclosure was present originally.

[00111] As used herein the terms "adapted" and "configured" mean that the element, component, or other subject matter is designed and/or intended to perform a given function. Thus, the use of the terms "adapted" and "configured" should not be construed to mean that a given element, component, or other subject matter is simply "capable of performing a given function but that the element, component, and/or other subject matter is specifically selected, created, implemented, utilized, programmed, and/or designed for the purpose of performing the function. It is also within the scope of the present disclosure that elements, components, and/or other recited subject matter that is recited as being adapted to perform a particular function may additionally or alternatively be described as being configured to perform that function, and vice versa.

[00112] As used herein, the phrase, "for example," the phrase, "as an example," and/or simply the term "example," when used with reference to one or more components, features, details, structures, embodiments, and/or methods according to the present disclosure, are intended to convey that the described component, feature, detail, structure, embodiment, and/or method is an illustrative, non-exclusive example of components, features, details, structures, embodiments, and/or methods according to the present disclosure. Thus, the described component, feature, detail, structure, embodiment, and/or method is not intended to be limiting, required, or exclusive/exhaustive; and other components, features, details, structures, embodiments, and/or methods, including structurally and/or functionally similar and/or equivalent components, features, details, structures, embodiments, and/or methods, are also within the scope of the present disclosure. Industrial Applicability

[00113] The wells and methods disclosed herein are applicable to the acoustic wireless communication, to the hydrocarbon exploration, and/or to the hydrocarbon production industries.

[00114] It is believed that the disclosure set forth above encompasses multiple distinct inventions with independent utility. While each of these inventions has been disclosed in its preferred form, the specific embodiments thereof as disclosed and illustrated herein are not to be considered in a limiting sense as numerous variations are possible. The subject matter of the inventions includes all novel and non-obvious combinations and subcombinations of the various elements, features, functions and/or properties disclosed herein. Similarly, where the claims recite "a" or "a first" element or the equivalent thereof, such claims should be understood to include incorporation of one or more such elements, neither requiring nor excluding two or more such elements.

[00115] It is believed that the following claims particularly point out certain combinations and subcombinations that are directed to one of the disclosed inventions and are novel and non- obvious. Inventions embodied in other combinations and subcombinations of features, functions, elements and/or properties may be claimed through amendment of the present claims or presentation of new claims in this or a related application. Such amended or new claims, whether they are directed to a different invention or directed to the same invention, whether different, broader, narrower, or equal in scope to the original claims, are also regarded as included within the subject matter of the inventions of the present disclosure.

Claims

1. A method of communicating in an acoustic wireless network that is spectrum- constrained and includes a plurality of nodes spaced-apart along a length of a tone transmission medium, the method comprising:

encoding an encoded character with an encoding node of the plurality of nodes, wherein the encoding includes:

(i) selecting, based upon the encoded character and from a first predetermined lookup table, a first frequency for a first transmitted acoustic tone;

(ii) transmitting the first transmitted acoustic tone, at the first frequency, via the tone transmission medium;

(iii) selecting, based upon the encoded character and from a second predetermined lookup table, a second frequency for a second transmitted acoustic tone, wherein the second frequency is different from the first frequency; and

(iv) transmitting the second transmitted acoustic tone, at the second frequency, via the tone transmission medium; and

decoding a decoded character with a decoding node of the plurality of nodes, wherein the decoding includes:

(i) responsive to the transmitting the first transmitted acoustic tone, receiving a first received acoustic tone from the tone transmission medium;

(ii) calculating a first frequency distribution for the first received acoustic tone;

(iii) determining, from the first frequency distribution and the first predetermined lookup table, a first decoded character distribution for the decoded character;

(iv) responsive to the transmitting the second transmitted acoustic tone, receiving a second received acoustic tone from the tone transmission medium;

(v) calculating a second frequency distribution for the second received acoustic tone;

(vi) determining, from the second frequency distribution and the second predetermined lookup table, a second decoded character distribution for the decoded character; and

(vii) identifying the decoded character based, at least in part, on the first decoded character distribution and the second decoded character distribution.

2. The method of claim 1, wherein the decoding node is spaced-apart from the encoding node such that the tone transmission medium extends between the encoding node and the decoding node.

3. The method of any of claims 1-2, wherein the method further includes conveying the first transmitted acoustic tone from the encoding node to the decoding node via the tone transmission medium, and further wherein the conveying the first transmitted acoustic tone includes modifying the first transmitted acoustic tone, via a first interaction between the first transmitted acoustic tone and the tone transmission medium, to generate the first received acoustic tone.

4. The method of any of claims 1-3, wherein the method further includes conveying the second transmitted acoustic tone from the encoding node to the decoding node via the tone transmission medium, and further wherein the conveying the second transmitted acoustic tone includes modifying the second transmitted acoustic tone, via a second interaction between the second transmitted acoustic tone and the tone transmission medium, to generate the second received acoustic tone.

5. The method of any of claims 1 -4, wherein the tone transmission medium includes at least one of:

(i) a downhole tubular that extends within a wellbore;

(ii) a wellbore fluid that extends within the wellbore;

(iii) a subterranean formation that defines the wellbore;

(iv) a cement that extends within the wellbore;

(v) a subsea tubular that extends within a subsea environment; and

(vi) a subsea fluid that extends within the subsea environment.

6. The method of any of claims 1-5, wherein the second predetermined lookup table is different from the first predetermined lookup table.

7. The method of any of claims 1-6, wherein the first frequency is correlated to the encoded character in the first predetermined lookup table.

8. The method of any of claims 1 -7, wherein the second frequency is correlated to the encoded character in the second predetermined lookup table.

9. The method of any of claims 1 -8, wherein the first predetermined lookup table provides a one-to-one correspondence between the first frequency and the encoded character.

10. The method of any of claims 1 -9, wherein the second predetermined lookup table provides a one-to-one correspondence between the second frequency and the encoded character.

11. The method of any of claims 1-10, wherein the first predetermined lookup table includes a plurality of characters and a corresponding plurality of first frequencies, wherein each character in the plurality of characters corresponds to only one first frequency of the plurality of first frequencies.

12. The method of claim 11, wherein the second predetermined lookup table includes the plurality of characters and a corresponding plurality of second frequencies, wherein each character in the plurality of characters corresponds to only one second frequency of the plurality of second frequencies.

13. The method of claim 12, wherein the plurality of first frequencies and the plurality of second frequencies both include the same plurality of frequencies.

14. The method of any of claims 12-13, wherein a different frequency corresponds to each character in the plurality of characters in the first predetermined lookup table when compared to the second predetermined lookup table.

15. The method of any of claims 12-14, wherein the plurality of first frequencies and the plurality of second frequencies are selected such that, for a given character in the plurality of characters, a corresponding first frequency of the plurality of first frequencies is unequal to a corresponding second frequency of the plurality of second frequencies.

16. The method of any of claims 12-15, wherein the plurality of first frequencies and the plurality of second frequencies are selected such that, for the given character in the plurality of characters, the corresponding first frequency is not a harmonic of the corresponding second frequency within the tone transmission medium.

17. The method of any of claims 1-16, wherein the transmitting the first transmitted acoustic tone includes transmitting the first transmitted acoustic tone for a first tone- transmission duration.

18. The method of any of claims 1-17, wherein the transmitting the second transmitted acoustic tone includes transmitting the second transmitted acoustic tone for a second tone- transmission duration.

19. The method of any of claims 1-18, wherein the first frequency is at least 50 kilohertz (kHz) and at most 1000 kHz.

20. The method of any of claims 1-19, wherein the second frequency is at least 50 kilohertz (kHz) and at most 1000 kHz.

21. The method of any of claims 1-20, wherein the transmitting the first transmitted acoustic tone includes inducing the first transmitted acoustic tone, within the tone transmission medium, with an encoding node transmitter.

22. The method of claim 21, wherein the transmitting the second transmitted acoustic tone includes inducing the second transmitted acoustic tone, within the tone transmission medium, with the encoding node transmitter.

23. The method of any of claims 21 -22, wherein the encoding node transmitter includes at least one of:

(i) a piezoelectric encoding node transmitter configured to induce a vibration within the tone transmission medium;

(ii) an electromagnetic acoustic transmitter configured to induce the vibration within the tone transmission medium;

(iii) a resonant microelectromechanical system (MEMS) transmitter configured to induce the vibration within the tone transmission medium;

(iv) a non-resonant MEMS transmitter configured to induce the vibration within the tone transmission medium; and

(v) a transmitter array configured to induce the vibration within the tone transmission medium.

24. The method of any of claims 1 -23, wherein the receiving the first received acoustic tone includes receiving the first received acoustic tone for a first tone-receipt duration.

25. The method of any of claims 1-24, wherein the receiving the second received acoustic tone includes receiving the second received acoustic tone for a second tone-receipt duration.

26. The method of any of claims 1 -25, wherein the receiving the first received acoustic tone includes receiving the first received acoustic tone with at least one of:

(i) a piezoelectric receiver configured to receive the first received acoustic tone from the tone transmission medium;

(ii) a piezoresistive receiver configured to receive the first received acoustic tone from the tone transmission medium;

(iii) a resonant microelectromechanical system (MEMS) receiver configured to receive the first received acoustic tone from the tone transmission medium;

(iv) a non-resonant MEMS receiver configured to receive the first received acoustic tone from the tone transmission medium; and

(v) a receiver array configured to receive the first received acoustic tone from the tone transmission medium.

27. The method of any of claims 1-26, wherein the calculating the first frequency distribution includes at least one of:

(i) performing a Fourier transform of the first received acoustic tone;

(ii) performing a fast Fourier transform of the first received acoustic tone;

(iii) performing a discrete Fourier transform of the first received acoustic tone;

(iv) performing a wavelet transform of the first received acoustic tone; (v) performing a multiple least squares analysis of the first received acoustic tone; and

(vi) performing a zero-crossing analysis of the first received acoustic tone.

28. The method of any of claims 1-27, wherein the calculating the second frequency distribution includes at least one of:

(i) performing a Fourier transform of the second received acoustic tone;

(ii) performing a fast Fourier transform of the second received acoustic tone;

(iii) performing a discrete Fourier transform of the second received acoustic tone;

(iv) performing a wavelet transform of the second received acoustic tone;

(v) performing a multiple least squares analysis of the second received acoustic tone; and

(vi) performing a zero-crossing analysis of the second received acoustic tone.

29. The method of any of claims 1 -28, wherein the first received acoustic tone includes a plurality of first frequency components, and further wherein the calculating the first frequency distribution includes at least one of:

(i) calculating a relative magnitude of each of the plurality of first frequency components; and

(ii) calculating a histogram of the plurality of first frequency components.

30. The method of claim 29, wherein the second received acoustic tone includes a plurality of second frequency components, and further wherein the calculating the second frequency distribution includes at least one of:

(i) calculating a relative magnitude of each of the plurality of second frequency components; and

(ii) calculating a histogram of the plurality of second frequency components.

31. The method of claim 30, wherein the plurality of first frequency components corresponds to a plurality of first received characters within the first predetermined lookup table, and further wherein the determining the first decoded character distribution includes at least one of:

(i) calculating a relative probability that the first received acoustic tone represents each first received character in the plurality of first received characters; and

(ii) calculating a histogram of the plurality of first received characters.

32. The method of any of claims 30-31 , wherein the plurality of second frequency components corresponds to a plurality of second received characters within the second predetermined lookup table, and further wherein the determining the second decoded character distribution includes at least one of: (i) calculating a relative probability that the second received acoustic tone represents each second received character in the plurality of second received characters; and

(ii) calculating a histogram of the plurality of second received characters.

33. The method of any of claims 30-32, wherein the determining the first decoded character distribution includes mapping each first frequency component in the plurality of first frequency components to a corresponding character in the first predetermined lookup table.

34. The method of any of claims 30-33, wherein the determining the second decoded character distribution includes mapping each second frequency component in the plurality of second frequency components to a corresponding character in the second predetermined lookup table.

35. The method of any of claims 1-34, wherein the identifying the decoded character includes identifying which character in the first decoded character distribution and in the second decoded character distribution has the highest probability of being the encoded character.

36. The method of any of claims 1-35, wherein the identifying the decoded character includes combining the first decoded character distribution with the second decoded character distribution to generate a composite decoded character distribution and selecting the most common character from the composite decoded character distribution.

37. The method of claim 36, wherein the combining includes at least one of:

(i) summing the first decoded character distribution and the second decoded character distribution;

(ii) combining utilizing a one-and-one-half moment method.

38. The method of any of claims 1-37, wherein the encoding node is a first node of the plurality of nodes, wherein the decoding node is a second node of the plurality of nodes, and further wherein the method includes:

repeating the encoding with the second node; and

repeating the decoding with a third node of the plurality of nodes, wherein the third node is spaced-apart from the second node along the length of the tone transmission medium.

39. The method of claim 38, wherein the second node is between the first node and the third node along the length of the tone transmission medium.

40. The method of any of claims 1-39, wherein the method includes repeating the encoding and the decoding a plurality of times to propagate the encoded character along the length of the tone transmission medium.

41. The method of any of claims 1-40, wherein the encoding further includes: (i) selecting a plurality of frequencies for a plurality of transmitted acoustic tones from a corresponding plurality of predetermined lookup tables; and

(ii) transmitting the plurality of transmitted acoustic tones via the tone transmission medium;

and further wherein the decoding includes:

(i) responsive to the transmitting of the plurality of transmitted acoustic tones, receiving a plurality of received acoustic tones from the tone transmission medium;

(ii) calculating a plurality of frequency distributions from the plurality of received acoustic tones;

(iii) determining, from the plurality of frequency distributions and the plurality of predetermined lookup tables, a plurality of decoded character distributions; and

(iv) identifying the decoded character based, at least in part, on the plurality of decoded character distributions.

42. The method of claim 41 , wherein the plurality of decoded character distributions includes at least 3 decoded character distributions.

43. The method of any of claims 1 -42, wherein, prior to both the encoding and the decoding, the method further includes establishing both the first predetermined lookup table and the second predetermined lookup table, wherein the establishing includes:

(i) transmitting a calibration signal from the encoding node and via the tone transmission medium, wherein the calibration signal includes a plurality of frequencies that span a frequency range;

(ii) receiving the calibration signal from the tone transmission medium with the decoding node;

(iii) determining at least one acoustic characteristic of the tone transmission medium; and

(iv) establishing the first predetermined lookup table and the second predetermined lookup table based, at least in part, on the at least one acoustic characteristic of the tone transmission medium.

44. The method of any of claims 1-43, wherein the encoded character is a first encoded character, wherein the decoded character is a first decoded character, and further wherein the method includes:

repeating the encoding to encode a second encoded character, wherein the repeating the encoding includes:

(i) selecting, based upon the second encoded character and from the first predetermined lookup table, a third frequency for a third transmitted acoustic tone; (ii) transmitting the third transmitted acoustic tone, at the third frequency, via the tone transmission medium;

(iii) selecting, based upon the second encoded character and from the second predetermined lookup table, a fourth frequency for a fourth transmitted acoustic tone, wherein the fourth frequency is different from the third frequency; and

(iv) transmitting the fourth transmitted acoustic tone, at the fourth frequency, via the tone transmission medium; and

repeating the decoding to decode a second decoded character, wherein the repeating the decoding includes:

(i) responsive to the transmitting the third transmitted acoustic tone, receiving a third received acoustic tone from the tone transmission medium;

(ii) calculating a third frequency distribution for the third received acoustic tone;

(iii) determining, from the third frequency distribution and the first predetermined lookup table, a third decoded character distribution for the second decoded character;

(iv) responsive to the transmitting the fourth transmitted acoustic tone, receiving a fourth received acoustic tone from the tone transmission medium;

(v) calculating a fourth frequency distribution for the fourth received acoustic tone;

(vi) determining, from the fourth frequency distribution and the second predetermined lookup table, a fourth decoded character distribution for the second decoded character; and

(vii) identifying the second decoded character based, at least in part, on the third decoded character distribution and the fourth decoded character distribution.

45. The method of any of claims 1-44, wherein the method further includes drilling the wellbore, and further wherein the method includes performing at least the encoding and the decoding during the drilling.

46. The method of any of claims 1-45, wherein the wellbore extends within a subterranean formation, wherein the method further includes producing a reservoir fluid from the subterranean formation, and further wherein the method includes performing at least the encoding and the decoding during the producing.

47. The method of any of claims 1 -46, wherein the method includes performing the encoding and the decoding without utilizing a pseudorandom number generator.

48. The method according to any of claims 1-47, used in a well, the well comprising: a wellbore that extends within a subterranean formation; and

a downhole acoustic wireless network including a plurality of nodes spaced-apart along a length of the wellbore, wherein the plurality of nodes includes an encoding node and a decoding node, and further wherein the plurality of nodes is programmed to wirelessly transmit a character along the length of the wellbore utilizing the method of any of claims 1-47.

49. The well of claim 48, wherein a single node of the plurality of nodes defines both a respective encoding node and a respective decoding node.

50. The according to any of claims 1 -49, further comprising at least one of a decoding a decoded character with a decoding node of the plurality of nodes, calculating a first frequency distribution, and calculating a second frequency distribution.