US20150077265A1

US20150077265A1 - Telemetry on tubing

Info

Publication number: US20150077265A1
Application number: US14/031,816
Authority: US
Inventors: Li Gao; Vimal V. Shah
Original assignee: Halliburton Energy Services Inc
Current assignee: Halliburton Energy Services Inc
Priority date: 2013-09-19
Filing date: 2013-09-19
Publication date: 2015-03-19
Also published as: WO2015041951A1

Abstract

In some embodiments, an apparatus and a system, as well as a method and an article, may operate to program a first acoustic repeater to transmit information at a first operating frequency; to couple the first acoustic repeater circumferentially around a coiled tubing portion, an inner diameter of the first acoustic repeater being about equal to an outer diameter of the coiled tubing portion; to program a second acoustic repeater to receive information transmitted by the first acoustic repeater; and to receive sensor information transmitted at the first operating frequency by the first acoustic repeater and relayed by the second acoustic repeater, the second acoustic repeater being coupled to the coiled tubing portion uphole from the first acoustic repeater. Additional apparatus, systems, and methods are disclosed.

Description

BACKGROUND

Tubing, such as coiled tubing, is a natural acoustic waveguide that can serve as a telemetry channel to establish bidirectional communication between surface operators and downhole sensors and tools in a subterranean well system. An acoustic telemetry system that operates on coiled tubing can include a single transmitter at the well system bottom hole assembly (BHA) and a receiver at the surface. For operations in extended and/or horizontal wells, however, the telemetry signal from the transmitter can be adversely attenuated.
Further, as coiled tubing is tripped into a well, it is commonly passed through a stripper packer to maintain well pressure. It may be difficult to use a conventional acoustic repeater to mitigate signal attenuation, because the combination of such a repeater and the coiled tubing may not fit through the stripper packer annulus while maintaining the well seal at the surface.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example coiled tube system including multiple acoustic repeaters in accordance with some embodiments.

FIG. 2 illustrates a front view of an example acoustic repeater in accordance with some embodiments.

FIG. 3 illustrates a section view of an example acoustic repeater in accordance with some embodiments.

FIG. 4 illustrates a section view of an example modular acoustic repeater in accordance with some embodiments.

FIG. 5 is a schematic diagram of an example electrical system for an acoustic repeater for coiled tube telemetry in accordance with some embodiments.

FIG. 6 illustrates an example data frame structure for data transmitted by the acoustic repeater in accordance with some embodiments.

FIG. 7 is a flow diagram for data transmission by the acoustic repeater in accordance with some embodiments.

FIG. 8 is a flow diagram for data reception by the surface system in accordance with some embodiments.

FIG. 9 is a flow chart illustrating a training and synchronization method in accordance with some embodiments.

FIG. 10 illustrates a single hop relay mode for acoustic repeater communication in accordance with some embodiments.

FIG. 11 illustrates a multi-hop relay mode for acoustic repeater communication in accordance with some embodiments.

FIG. 12 is a flowchart illustrating a method for providing communication between acoustic repeaters and a surface system in accordance with some embodiments.

DETAILED DESCRIPTION

To address some of the challenges described above, as well as others, systems, apparatus, and methods are described herein for using acoustic telemetry repeaters in a subterranean well system that employs coiled tubing. The acoustic repeaters may comprise a relatively thin, hinged annular housing, which can be coupled about the circumference of the coiled tubing before the stripper packer location along the tubing, as the tubing is tripped into a well. The annular housing of the acoustic repeater is configured to be concentric with the coiled tubing and symmetric about the longitudinal axis of the coiled tubing. Concentricity and symmetry combined with a relatively small radial thickness of the repeater housing enables the repeater to be attached to the coiled tubing before the tubing passes through the stripper packer into the well. Concentricity can also enable coupling of the repeater without creating discontinuities along the coiled tubing. When discontinuities are created, pressure may leak out, defeating the purpose of the stripper packer.
FIG. 1 illustrates a coiled tubing system (CTS) 10 including a reel 12, coiled tubing (CT) 14, a gooseneck 16, an injector head 18, and a stripper packer 20. CTS 10 is configured to trip the CT 14 into and out of a wellbore 22 within a casing 24. CTS 10 can be used for a number of interventions, and, in some cases, for production in subterranean wells.
In operation, injector head 18 draws CT 14 off of reel 12 and trips CT 14 into wellbore 22 through stripper packer 20. Injector head 18 includes a mechanism that pushes CT 14 into and pulls CT 14 out of wellbore 22. Injector head 18 operates in conjunction with gooseneck 16, which acts as a curved guide beam that threads CT 14 into injector head 18.
Below injector head 18 is stripper packer 20. Stripper packer 20 can include rubber pack off members, which provide a seal around casing 24 to isolate the pressure within the well from the surface. Stripper packer 20 can be hydraulically opened and closed to contain wellbore pressure. By applying hydraulic pressure at stripper packer 20, an operator at the surface of the well is able to compress rubber inserts and trip CT 14 into and out of wellbore 22 under pressure.
Although not shown in FIG. 1, CTS 10 can also include a blowout preventer (BOP) below stripper packer 20. The BOP can provide the ability to cut CT 14 and seal wellbore 22 (shear-blind) to hold and seal around CT 14 (pipe-slip).
Example CTS 10 also includes multiple acoustic repeaters 26, 27 communicatively coupling a downhole transmitter (not shown) and a surface receiver 28. The bottommost acoustic repeater 27 may serve as the downhole transmitter. As described in more detail below, acoustic repeaters 26 include a thin hinged annular housing, which can be coupled about the circumference of CT 14 before passing through stripper packer 20 as CT 14 is tripped into wellbore 22. The annular housing of acoustic repeaters 26 is configured to be concentric with CT 14 and symmetric about the longitudinal axis of the tubing, however embodiments are not limited thereto. Concentricity and symmetry combined with a relatively small radial thickness of the housing can enable acoustic repeaters 26 coupled to CT 14 to pass through stripper packer 20. The ability to trip acoustic repeaters 26 into wellbore 22 through stripper packer 20 enables multiple repeaters to be deployed downhole to mitigate signal attenuation in extended and/or horizontal subterranean wells.
FIG. 2 depicts a front view of an example acoustic repeater 26 in accordance with some embodiments. Acoustic repeater 26 includes an annular housing 28. Annular housing 28 engages an outer surface of CT 14 using, for example, hinges 30. While some example acoustic repeaters 26 may have a relatively smooth outer surface (e.g., spherical or ovoid as depicted in FIG. 2) that can be useful in some embodiments to provide less leakage as the repeater 26, 27 passes through the strip packet 20 and into the well, other acoustic repeaters 26, 27 can have other shapes, such as hexagonal or rectangular shapes.
FIG. 3 depicts a section view of acoustic repeater 26 in accordance with some embodiments. Annular housing 28 encloses acoustic transmitter 32. Acoustic transmitter 32 can also serve as an acoustic telemetry signal detector (e.g., a receiver). Acoustic transmitter 32 can include a piezoelectric actuator 56 (FIG. 5). The piezoelectric actuator 56 may be flexible to enable the piezoelectric actuator 56 to be mounted in annular housing 28 that is concentrically mounted about CT 14. The flexible piezoelectric actuator 56 can include a micro-fiber composite (MFC) piezoelectric actuator. Some references for MFC piezoelectric actuators quote stress generation capabilities of +/−4000 psi at temperatures up to 180 degrees Celsius. Acoustic transmitter 32 can include a plurality of flexible piezoelectric actuators (not shown in the figures) arranged in a stack to actuate together. In this manner, the actuators can generate acoustic signals with higher power than the actuators could individually generate for transmission on CT 14.
Acoustic repeater 26 includes electrical circuitry 34. Electrical circuitry 34 may include some of the elements described in more detail below with respect to FIG. 5 (e.g., elements 44-50 and 54). Annular housing 28 may enclose electrical circuitry 34, or electrical circuitry 34 may be enclosed in another separate annular housing as described below with respect to FIG. 4. Electrical circuitry 34 and acoustic transmitter 32 may be exposed to at least some ambient pressure to permit a thinner annular housing 28 design. A thinner annular housing 28 design may enable further reduction in the profile of acoustic repeater 26, as it appears against the outer surface of the coiled tubing. A thinner annular housing 28 may provide capability for insertion of additional electrical circuitry 34 into annular housing 28.
Acoustic repeater 26 can include a flexible battery element 36. Flexible battery element 36 can include a plurality of flexible battery portions, which may be housed in separate annular housing (not shown in FIG. 3). Some references for flexible battery elements quote a thickness of about 0.5 millimeters. Flexible battery portions may be combined in series or parallel to achieve greater power capacity in acoustic repeater 26. In some embodiments, a flexible battery such as the FLEXION (Model SF 4823-25EC) lithium polymer battery made by Solicore corporation (Lakeland, Fla., United States of America) can be used as the flexible battery element 36.
Annular housing 28 can have an inner diameter about equal to an outer diameter of CT 14 to prevent, for example, leakage or loss of pressure between acoustic repeater 26 and CT 14. Some references for CT quote outer diameters of about 1.2 inches to about 2.5 inches. Annular housing 28 may have an outer diameter larger than an inner diameter of stripper packer 20. For example, annular housing 28 may have an outer diameter larger than an inner diameter of rubber inserts of stripper packer 20, described above with respect to FIG. 1, yet small enough that the annual housing 28 does not apply excessive stress to the rubber inserts or other elements of stripper packer 20. Some references for the stripper packer 20 quote through-bore sizes of about 2.5 inches to about 5 inches.
FIG. 4 is a section view of acoustic repeater 26 arranged in a modular design in accordance with some embodiments. Acoustic repeater 26 can be separated into acoustic transmitter module 38, electrical module 40, battery modules 42 and 44, or any combination of modules thereof. Acoustic repeater 26 may be arranged in a modular design to gain flexibility in acoustic repeater 26 configuration and for ease of maintenance. For example, operators can add or remove additional battery modules 42, 44 to adjust to changing energy requirements or change or add electrical modules 40 to adjust to changing requirements or replace non-functioning modules of acoustic repeater 26. The modular design as shown in FIG. 4 may also allow for a further reduced profile of the overall acoustic repeater 26, with respect to the distance the repeater 26 rises above the outer surface of the coiled tubing.
FIG. 5 is a schematic diagram of an electrical system for acoustic repeater 26 in accordance with some embodiments. Acoustic repeaters 26 in accordance with this disclosure can be constructed with a number of electronic components. The components described with respect to FIG. 5 can include application-specific integrated circuits (ASICs) or field programmable gated arrays (FPGAs) designed for acoustic telemetry applications. Any of the components shown in FIG. 5 may be housed separately or together in the annular housing 28 (FIG. 2-3) or in one or more modules such as modules 38, 40, 42, 44 (FIG. 4) of the acoustic repeater 26. While some components are shown in FIG. 5, acoustic repeater 26 may include other components not shown in FIG. 5 or acoustic repeater 26 may include a subset of the components shown in FIG. 5. Different acoustic repeaters 26 of system 10 may have different subsets of the components shown in FIG. 5.
In some embodiments, acoustic repeater 26 includes a floating point digital signal processing (DSP) board 45. DSP board 45 is configured to receive digital data from, for example, transducer interface board 46, gamma board 48, accelerometer 50 or other data sources over communication links, for example an RS232 communication link or other data and control lines. Transducer interface board 46 can receive and digitize data from casing collar locator assembly 52, pressure transducers 54 or other sources within or external to the acoustic repeater 26 assembly.
Accelerometer 50 can be a single-axis accelerometer or a multi-axis accelerometer. For example, accelerometer 50 can be multi-axis to provide increased precision or sensitivity with respect to off-axis movement. Using accelerometer 50, acoustic repeater 26 can also detect pressure pulses in the fluid within, for example, CT 14 or elsewhere. In this way, acoustic repeater 26 can detect and relay mud pulse telemetry signals to surface system 28 (FIG. 1).
DSP board 45 compresses and packages the digital data and transmits the data over a communication link to acoustic driver board 54. Acoustic driver board 54 can be used to drive piezoelectric stack 56 of acoustic transmitter 32, which generates acoustic signals that are transmitted through CT 14 (FIG. 1-4). As described above with respect to FIG. 3-4, acoustic repeater 26 can include low profile batteries 36. Acoustic repeater 26 can also include power supply boards 60 and 62.
Piezoelectric stack 56, another piezoelectric stack (not shown in FIG. 5) or accelerometer 50 can also serve as a receiver for acoustic repeater 26. In some embodiments, acoustic repeater 26 may include processor 58 that can be programmed to implement different modulation schemes or trained to allow acoustic receiver 26 to receive and transmit on different frequencies as described below with respect to FIG. 7. In some embodiments, acoustic transmitter 32 can additionally or alternatively be programmed to implement different modulation schemes or trained to allow acoustic receiver 26 to receive and transmit on different frequencies.
FIG. 6 illustrates a generic data frame structure for a data frame 64 transmitted by acoustic repeater 26 in accordance with some embodiments. Data frame 64 can include preamble 66. Preamble 66 can include a pattern of data to allow acoustic repeaters 26, surface system 28 or other devices to detect new incoming data frames 64. Data frame 64 can include a data frame delimiter 68 to denote the end of preamble 66. Data frame 64 can include a header 70. Header 70 can have identification information for data frame 64 such as type identifiers, sources of the data, etc. Data frame 64 can include a data payload 72, which can include sensor data or other data being transmitted by acoustic repeater 26. Data frame 64 can include a cyclic redundancy check (CRC) 74 for detection of corrupted data within data frame 64. Data frame 64 can include all of fields 66, 68, 70, 72, and 74, or a subset of these fields, or other fields (not shown in FIG. 6).
FIG. 7 is a flow diagram for data transmission by acoustic repeater 26 in accordance with some embodiments. Functional elements can be performed within acoustic repeater 26 by, for example, DSP board 44, acoustic driver board 54, processor 58, or acoustic transmitter 32.
Data to be transmitted 76 may be received at acoustic transmitter 32, or as digital data received from the acoustic driver board 54 and encoded as acoustic data in an encoder 78. Circuitry, for example the circuitry of processor 58 or acoustic transmitter 32, can perform modulation 80, preamble generation 82, and header generation 84 to assemble 86 a data packet 64 (FIG. 6). Acoustic transmitter 32 transmits the data packet 64. For example, piezoelectric stack 56 of the acoustic transmitter 32 can launch an acoustic signal into CT 14, which then acts as an acoustic transmission medium.
Modulation 80 can be performed according to various modulation schemes, including at least one of pulse position modulation (PPM), on-off keying (OOK), frequency shift keying (FSK), amplitude modulation (AM), and phase shift keying (PSK).
Modulation 80 can also be performed using orthogonal frequency division multiplexing (OFDM), which is a method currently used in some broadband communication applications for encoding digital data on multiple carrier frequencies. With OFDM, a large number of closely-spaced orthogonal sub-carrier signals are used to carry the data on parallel channels. Each sub-carrier is modulated with a modulation scheme such as, for example, FSK, at a low symbol rate.
In some embodiments, OFDM may be used because the movement of CT 14 can generate loud noises or other interference. OFDM can reduce the impact of the noise at the surface, where signals may be processed, thus improving reliability of some embodiments. OFDM can reduce the impact of noise at least because OFDM's low symbol rate can permit the use of a guard interval between symbols (e.g., a representation of bits of data), thus reducing or eliminating interference between symbols and, in turn, leading to a signal-to-noise ratio improvement.
FIG. 8 is a flow diagram for data reception by surface system 28 in accordance with some embodiments. In functional blocks 88, 90, 92, 94, and 96, surface system 28 can detect various portions of a data frame 64 (FIG. 6). In functional block 94, surface system 28 can perform a demodulation of the data signal that was modulated by acoustic repeater 26. Surface system 28 can perform error checking in functional block 96. Surface system 28 can then, in functional block 98, receive or prepare to receive a next data frame 64.
FIG. 9 is a flow chart illustrating a training and synchronization method 900 in accordance with some embodiments. The training and synchronization method 900 can be performed when acoustic repeaters 26, 27 are downhole. The training and synchronization method 900 can be performed when the surface system 28 detects that downhole conditions have change, when additional acoustic repeaters 26 are coupled to CT 14, or for other reasons. Training and synchronization may be executed by processor 58 or acoustic transmitter 32 of an acoustic repeater 26. The training and synchronization method 900 can include functionalities 901 performed by surface system 28 and other functionalities 903 performed by acoustic repeaters 26, 27.
Surface system 28 can scan 902 a set of predetermined frequency channels. Acoustic repeater 26 can transmit 904 on the predetermined frequency channels. Surface system 28 can listen on the predetermined frequency channels for these transmissions of acoustic repeater 26 to identify 906 frequency channels that have at least a threshold signal-to-noise ratio (SNR). Acoustic repeater 26 can wait 908 for a certain time duration after each transmission, and then turn on 910 a listen mode to listen for a channel identifier. If a channel identifier is received 912 from the surface system 28, acoustic repeater 26 can send an acknowledgement 914 and repeater identifier on the frequency channel identified.
If surface system 28 receives 916 a response, including an acknowledgement and an acoustic repeater identifier, to the surface system 28's transmission of the channel identifier, the acoustic repeater 26 can begin 918 transmissions on the determined frequency channel, and surface system 28 can receive 920 data from acoustic repeater 26 on the frequency channel. Otherwise, the synchronization process may begin anew, or other channel identifiers can be transmitted to the acoustic repeater 26.
Instead of or in addition to the process described above with respect to FIG. 9, acoustic repeaters can be pre-programmed to transmit on a given frequency channel. The frequency channel can be adapted at a later time using the process described above with respect to FIG. 9.
FIG. 10 illustrates an example single hop relay mode for acoustic repeater 26 communication in accordance with some embodiments. In the illustrative example, two frequency channels f1 and f2 are in use. At least one acoustic repeater 26 receives data on frequency channel f1 and retransmits on frequency channel f2. Adjacent acoustic repeaters 26 transmit on different frequency channels f1, f2 to avoid signal contamination between the channels. Frequency channels f1 and f2 may have been programmed into acoustic repeaters 26 when the acoustic repeaters 26 were coupled to CT 14, or at a later time during a synchronization process as described above with respect to FIG. 9.
FIG. 11 illustrates a multi-hop relay mode for acoustic repeater communication in accordance with some embodiments. In the multi-hop relay mode, adjacent acoustic repeaters 26 still transmit on different frequencies f1, f2. Each acoustic repeater 26 receives and retransmits on a same frequency f1 or f2. Accordingly, when data is transmitted on, for example, frequency f1, that data is not received by a next adjacent acoustic repeater 26 but instead by a subsequent acoustic repeater 26.
FIG. 12 is a flowchart illustrating an example method 1200 for providing communication between acoustic repeaters and a surface system in accordance with some embodiments. Some elements of method 1200 can be implemented by a surface receiver system 28 (FIG. 1).
Example method 1200 starts at block 1210 with programming a first acoustic repeater 26 to transmit information at a first operating frequency. In some embodiments, the programming of block 1210 proceeds similarly to the training and synchronization method described above with respect to FIG. 9. In some embodiments, first acoustic repeater 26 is preprogrammed to transmit at a first operating frequency and later trained to transmit at different operating frequencies as described above with respect to FIG. 9. First acoustic repeater 26 can also be programmed to use a modulation scheme for modulating signals containing the sensor information. The modulation scheme can include OFDM, as described above with respect to FIG. 7.
Example method 1200 continues at block 1220 with coupling the first acoustic repeater 26 circumferentially around a CT 14 portion, an inner diameter of the first acoustic repeater 26 being about equal to an outer diameter of the CT 14 portion.
Example method 1200 continues at block 1230 with programming a second acoustic repeater 26 to receive information transmitted by the first acoustic repeater 26.
Example method 1200 continues at block 1240 with receiving sensor information transmitted at the first operating frequency by the first acoustic repeater and relayed by the second acoustic repeater. The second acoustic repeater is coupled to the coiled tubing portion uphole from the first acoustic repeater. The second acoustic repeater can relay the information on a second operating frequency different from the first operating frequency.
Any number of additional acoustic repeaters 26 can be coupled to CT 14. The number can be selected based on or in response to a determination that a wellbore condition has changed. If additional acoustic repeaters 26 are added, a synchronization process as described above can be performed. This process can include at least transmitting synchronization instructions to the first acoustic repeater, subsequent to the coupling or uncoupling, to instruct the first acoustic repeater to transmit test information using another frequency different from the first frequency.
Example method 1200 can include receiving mud pulse telemetry signals from first acoustic repeater 26 based on a measurement by an accelerometer 50 (FIG. 5) of first acoustic repeater 26.
It should be noted that the methods described herein do not have to be executed in the order described, or in any particular order. Moreover, various activities described with respect to the methods identified herein can be executed in iterative, serial, or parallel fashion.
In summary, using the apparatus, systems, and methods disclosed herein can provide surface systems with downhole sensor data that uses the coiled tubing itself as an acoustic communication channel between a series of acoustic repeaters. As a result, real-time downhole conditions can be monitored during CT-delivered services or processes, such as fracturing processes, in extended or horizontal wells. At the same time, a surface system can send commands, through the repeaters, to instruct downhole tools to carry out desired operations. The low-profile of the repeaters makes it possible to trip them into a well, through a conventional stripper packer, without loss of pressure or other problems, and without the need to modify existing surface equipment.
The accompanying drawings that form a part hereof, show by way of illustration, and not of limitation, specific embodiments in which the subject matter may be practiced. The embodiments illustrated are described in sufficient detail to enable those skilled in the art to practice the teachings disclosed herein. Other embodiments may be utilized and derived therefrom, such that structural and logical substitutions and changes may be made without departing from the scope of this disclosure. This Detailed Description, therefore, is not to be taken in a limiting sense, and the scope of various embodiments is defined only by the appended claims, along with the full range of equivalents to which such claims are entitled.
Such embodiments of the inventive subject matter may be referred to herein, individually and/or collectively, by the term “invention” merely for convenience and without intending to voluntarily limit the scope of this application to any single invention or inventive concept if more than one is in fact disclosed. Thus, although specific embodiments have been illustrated and described herein, it should be appreciated that any arrangement calculated to achieve the same purpose may be substituted for the specific embodiments shown. This disclosure is intended to cover any and all adaptations or variations of various embodiments. Combinations of the above embodiments, and other embodiments not specifically described herein, will be apparent to those of ordinary skill in the art upon reviewing the above description.

Claims

What is claimed is:

1. A coiled tubing acoustic telemetry system, comprising:

a length of coiled tubing; and

a first repeater apparatus including,

an acoustic transmitter,

electrical circuitry configured to drive the acoustic transmitter to generate acoustic signals, and

an annular housing configured to enclose the acoustic transmitter and to engage an outer surface of the coiled tubing, the annular housing having an inner diameter about equal to an outer diameter of the length of coiled tubing; and

a second repeater apparatus coupled to the coiled tubing portion and spaced at a distance downhole from the first repeater apparatus, the second repeater apparatus including an acoustic transmitter and an annular housing configured to enclose the acoustic transmitter and to engage an outer surface of the coiled tubing, the annular housing having an inner diameter about equal to an outer diameter of the coiled tubing portion.

2. The system of claim 1 wherein the annular housing has an outer diameter larger than an inner diameter of a stripper packer assembly.

3. The system of claim 1, wherein the acoustic transmitter includes a flexible piezoelectric actuator.

4. The system of claim 1, wherein the electrical circuitry is housed in another annular housing separate from the annular housing.

5. The system of claim 1, wherein the first repeater apparatus further includes a flexible battery element including a plurality of battery portions.

6. The system of claim 5, wherein a battery portion of the plurality of battery portions being enclosed in another annular housing separate from the annular housing.

7. A method for providing communication between acoustic repeaters and a surface system, the method comprising:

programming a first acoustic repeater to transmit information at a first operating frequency;

coupling the first acoustic repeater circumferentially around a coiled tubing portion, an inner diameter of the first acoustic repeater being about equal to an outer diameter of the coiled tubing portion;

programming a second acoustic repeater to receive information transmitted by the first acoustic repeater; and

receiving sensor information transmitted at the first operating frequency by the first acoustic repeater and relayed by the second acoustic repeater, the second acoustic repeater being coupled to the coiled tubing portion uphole from the first acoustic repeater.

8. The method of claim 7, wherein the second acoustic repeater relays the information on a second operating frequency different from the first operating frequency.

9. The method of claim 7, further comprising:

coupling additional acoustic repeaters to the coiled tubing portion responsive to a determination that a wellbore condition has changed; and

transmitting synchronization instructions to the first acoustic repeater, subsequent to the coupling or uncoupling, to instruct the first acoustic repeater to transmit test information using another frequency different from the first frequency.

10. The method of claim 7, further comprising:

programming the first acoustic repeater to use a modulation scheme for modulating signals containing the sensor information.

11. The method of claim 10, wherein the modulation scheme includes orthogonal frequency division multiplexing.

12. The method of claim 7, further comprising:

receiving mud pulse telemetry signals from the first acoustic repeater based on a measurement by an accelerometer of the first acoustic repeater.

13. An apparatus, comprising:

an acoustic transmitter;

electrical circuitry configured to drive the acoustic transmitter to generate acoustic signals;

an annular housing configured to enclose the acoustic transmitter and to engage an outer circumference of a section of coiled tubing; and

a receiver.

14. The apparatus of claim 13, wherein the acoustic transmitter includes a flexible piezoelectric actuator.

15. The apparatus of claim 13, wherein the electrical circuitry is enclosed in the annular housing.

16. The apparatus of claim 15, further comprising additional electrical circuitry enclosed in another annular housing separate from the annular housing, the additional electrical circuitry including one or more of a transducer interface board, a digital signal processing board, or a gamma board.

17. The apparatus of claim 16, wherein the annular housing has an outer diameter larger than an inner diameter of a stripper packer assembly.

18. The apparatus of claim 13, further comprising a flexible battery element.

19. The apparatus of claim 18, wherein the flexible battery element includes a plurality of flexible battery portions.

20. The apparatus of claim 19, wherein a battery portion of the plurality of battery portions is enclosed in a second annular housing different from the annular housing.