DE102015017138B4 - Mud siren arrangement - Google Patents

Abstract

A mud siren assembly comprising:• a stator having at least a first partial stator and at least a second partial stator;• a first mud siren having a first rotor, the first mud siren having a first open cross-sectional area when the first partial stator and the first rotor at least partially overlap;• a second mud siren having a second rotor, the second mud siren having a second open cross-sectional area when the second partial stator and the second rotor at least partially overlap;• wherein the second partial stator partially surrounds the first partial stator;• wherein the second rotor partially surrounds the first rotor;• wherein the second open cross-sectional area partially surrounds the first open cross-sectional area.

Description

The invention relates to mud siren arrangements.

To monitor and control deep drilling, a drilling rig is usually equipped with various sensors and measuring devices that measure the so-called drilling path and examine the rock during drilling. The data obtained are to be transmitted from the bottom of the borehole to the surface during the so-called sinking of the borehole.

Data transmission in deep drilling technology is used to transmit the measurement data of the measured geological data (also known as logging while drilling, LWD) and the measured orientation data such as the inclination, the direction (azimuth), and the orientation of the drilling tool (also known as measuring while drilling, MWD) to the earth's surface (i.e. above ground). The measurement data enables a directional drill to precisely monitor the drilling process. The most common method for data transmission in a borehole is so-called mud pulse telemetry. It sends the information to the surface using coded pressure pulses via the drilling fluid, which is continuously pumped through a drill rod. There, the pressure pulses are received, decoded, and displayed using a pressure sensor. Various types of pulsers are usually used to generate pulses underground, one of which is the so-called mud siren.

A mud siren typically has a stator and a rotor, whereby continuous pressure pulses (also referred to as "tones") are generated by means of a rotational movement of the rotor relative to the stator. The maximum pressure in the drill string above the mud siren is reached each time the solid rotor blade(s) of the rotor cover the open spaces of the mud siren's stator. In contrast, the pressure in the drill string above the mud siren is minimal when the open spaces of the rotor correspond to free surfaces of the stator.

One disadvantage of the conventional mud siren is its low data rate. Since significantly less data can be transmitted above ground than is generated underground, it is usually necessary to carry out complex pre-processing of the measured raw data using an underground computer. However, this results in the need for a very complex and therefore expensive underground computing unit. The underground computing unit must also be adapted to the underground conditions, for example to the temperatures in the borehole of at least 150°C, to extreme shocks and vibrations, and to the very high pressures in the borehole.

EP 2 835 494 A1 describes a transmission device in which a plurality of valves are rotated and stopped at different frequencies, thereby generating pressure waves at respective frequencies. A stator and a rotor are components of a valve. The rotor is configured with four blades and rotates to block the holes of the stator (flow path) and increase the pressure therein. With a 360 degree rotation of the rotor, four cycles of pressure wave changes can be observed. Furthermore, in terms of data transmission, a pressure waveform is transmitted as symbols of 1/0 data by stopping the rotation of the rotor immediately to change the phase of the pressure wave.

US 2006/0 132 327 A1 describes measurements using dual sensors (flow or pressure) to attenuate pump noise in a mud pulse telemetry system. A pulser assembly is located in the internal bore of a tool housing. Drilling fluid flows through a stator and a rotor, passing through the annulus between the pulser housing and the inner diameter of the tool housing. The stator is fixed with respect to the pulser housing and has several longitudinal flow channels. The rotor channels are adapted to be aligned at an angular position with the stator channels to create a straight flow path. Angular displacement of the rotor with respect to the stator changes the effective flow area, creating pressure fluctuations in the circulating mud column. To achieve pressure cycling, it is necessary to open and close the flow channel by changing the angular position of the rotor blades with respect to the stator flow channel.

US 2006 / 0 077 757 A1 describes a method for seismic measurement during drilling. A seismic source and a seismic receiver are arranged in a drill string in a borehole, with the source and the receiver being mounted in the drill string at a predetermined distance from each other. A model is created which is characteristic of the underground formation. is by a first seismic shot at a first frequency as drilling progresses into a subterranean formation, wherein at least a second model characteristic of the subterranean formation is generated by executing at least one subsequent seismic shot at a higher frequency at at least one subsequent level. Using the first and at least second models in combination, the subterranean formation and the progress of the drill string relative to the formation can be evaluated. The drill string further includes an integrated downhole transmission network capable of transmitting data in real time. The waveforms acquired by the receiver as well as a pilot signal representative of the pulses generated by the seismic source are transmitted to the surface via the downhole network.

The invention is therefore based on the problem of increasing the achievable data rate of a mud siren arrangement.

The problem is solved according to the invention by the mud siren arrangements according to patent claims 1 to 10.

In various comparative examples, a mud siren arrangement is provided, comprising: a drilling assembly; a first mud siren arranged in the drilling assembly; at least one further mud siren arranged in the drilling assembly; and at least one coding device which is coupled to the first mud siren and the at least one further mud siren. The first mud siren and the at least one further mud siren are arranged in such a way and the coding device controls the first mud siren and the at least one further mud siren in such a way that at a coding time, information comprising several bits is encoded and transmitted by means of the first mud siren and the at least one further mud siren.

In this way, at one coding point in time, for example in a time slot, not only one-bit information can be transmitted, but information that has several bits. This multiplies the achievable data rate.

It should be noted that not only two mud sirens can be provided, but also three, four, five or even more mud sirens can be arranged in the drilling assembly, which even makes it possible to transmit information of more than two bits per coding time, for example per time slot. For example, with three mud sirens in the drilling assembly, it is possible to transmit three information bits per coding time, with four mud sirens in the drilling assembly, four information bits per coding time, with five mud sirens in the drilling assembly, five information bits per coding time, etc. The achievable data rate can thus be significantly increased.

In an embodiment according to the invention, the first mud siren and the at least one further mud siren (hereinafter also referred to as the second mud siren) can be arranged one behind the other in the drilling assembly (with respect to a flow direction of the mud siren arrangement). This clearly corresponds to a series connection of several mud sirens within the drilling assembly. If more than two mud sirens are arranged one behind the other in series within the drilling assembly, the respective mud sirens can be driven with different frequencies for encoding and transmitting the respective information.

The different frequencies should not be integer multiples of each other.

In another embodiment according to the invention, the first mud siren and the at least one further mud siren can be arranged next to one another in the drilling assembly (with respect to a flow direction of the mud siren arrangement). This clearly corresponds to a parallel connection of several mud sirens within the drilling assembly.

In this case too, the different frequencies should not be integer multiples of each other.

It should be noted that in various comparative examples, the different frequencies of the mud sirens can be achieved not only by adjusting the rotational speed, but also by changing the number of blades of the rotor and/or stator (in other words, by changing the number of rotor blades and/or stator blades in the mud sirens).

However, it can also be provided to change the speed and also to modify mud sirens with a different number of rotor blades and/or stator blades in the mud sirens in order to generate the desired frequencies.

In general, a plurality of mud sirens can be arranged within the drilling assembly in a combination of one or more series circuits with one or more parallel circuits and can be operated, for example, at different frequencies for coding and transmitting the information.

In another embodiment according to the invention, the coding device can control the first mud siren and the at least one further mud siren in such a way that the first mud siren and the at least one further mud siren are driven at different frequencies to encode the information comprising several bits. In order to ensure the best possible data transmission with the least possible attenuation of the transmitted signals, it is advantageous if the different frequencies are not selected to be too high.

Furthermore, the frequencies should not be integer multiples of each other.

The coding time can be the start of a time slot of a plurality of time slots. The coding time can thus be understood, for example, as the start of the coding and transmission of information with multiple bits.

The frequencies of the mud sirens during operation can be less than or equal to approximately 100 Hz, for example less than or equal to approximately 90 Hz, for example less than or equal to approximately 80 Hz, for example less than or equal to approximately 70 Hz, for example less than or equal to approximately 60 Hz, for example according to patent claim 10 less than or equal to approximately 50 Hz, for example less than or equal to approximately 40 Hz, for example less than or equal to 30 Hz, for example less than or equal to 25 Hz, for example less than or equal to 20 Hz, for example less than or equal to 15 Hz.

In various comparative examples, a mud siren arrangement is thus clearly provided with a plurality of mud sirens connected in parallel and/or in series, which are controlled in such a way that, on the one hand, they are preferably operated with different operating frequencies (for example, in such a way that the different frequencies are not integer multiples of one another) and, on the other hand, in such a way that they each encode a predeterminable code word at a predetermined coding time (for example, if two mud sirens are provided, the following code words are provided: "00", "01", "10", and "11") and transmit them by means of the fluid contained in the drill rod to the surface of the borehole, clearly to the beginning of the drill rod, which can be located above ground, where they are then received by a suitably configured receiver and decoded by a decoding device.

As a comparative example, a method for encoding and transmitting information comprising a plurality of bits is disclosed. The method can comprise operating a first mud siren arranged in a drilling assembly at a first frequency; operating at least one further mud siren arranged in the drilling assembly at a further frequency that is different from the first frequency; and controlling the first mud siren and the at least one further mud siren such that the information comprising a plurality of bits is encoded and transmitted at a coding time by means of the first mud siren and the at least one further mud siren.

In various embodiments, a substantially incompressible medium (for example a substantially incompressible liquid such as water or water- or oil-based drilling fluid) is flushed through the first mud siren and the at least one further mud siren to transmit the information to the earth's surface. A substantially incompressible medium is understood to mean a medium in which, when it flows through a mud siren, assuming a certain constant differential pressure across the mud siren, only as much of the medium (for example water) flows through a series connection of several mud sirens as fits through the mud siren that has the smallest cross-sectional opening of all the mud sirens connected in series.

The first mud siren and the at least one further mud siren can be arranged one behind the other in the drilling assembly (with respect to a flow direction of the mud siren arrangement).

Alternatively, the first mud siren and the at least one further mud siren can be arranged next to each other in the drilling assembly (with respect to a flow direction of the mud siren arrangement).

It should be noted in general that when several mud sirens are connected in parallel as a TFA, the sum of the individual TFAs of the individual mud sirens connected in parallel is determined.

Furthermore, the first mud siren and the at least one further mud siren can be driven at different frequencies for encoding the information comprising multiple bits.

The coding time may be a start of a time slot of a plurality of time slots.

The frequencies of the mud sirens in operation may be less than or equal to approximately 100 Hz, for example less than or equal to approximately 90 Hz, for example less than or equal to approximately 80 Hz, for example less than or equal to approximately 70 Hz, for example less than or equal to approximately 60 Hz, for example less than or equal to approximately 50 Hz, for example less than or equal to approximately 40 Hz, for example less than or equal to 30 Hz, for example less than or equal to 25 Hz, for example less than or equal to 20 Hz, for example less than or equal to 15 Hz.

In various comparative examples, a mud siren decoding arrangement is provided, comprising: a receiver configured to receive a mud siren signal transmitted by means of a drilling fluid; a decoder coupled to the receiver configured to decode the received mud siren signal; wherein the decoder is configured to decode the received mud siren signal into a first multi-bit signal if the determined frequency of the received mud siren signal is in a first frequency range, to decode the received mud siren signal into a second multi-bit signal if the determined frequency of the received mud siren signal is in a second frequency range, and to decode the received mud siren signal into a third multi-bit signal if the determined frequency of the received mud siren signal is in a third frequency range.

In one embodiment, the decoder can further be configured to decode the received mud siren signal to a fourth multi-bit signal if the determined frequency of the received mud siren signal is in a fourth frequency range or if the received mud siren signal in the time range or the energy of the received mud siren signal in the frequency range is below a predetermined threshold value and, for example, essentially no pressure wave signal (i.e. no change in pressure compared to a flushing process with the mud siren(s) fully open) is detected, for example, by the receiver.

In one embodiment, the receiver may have at least one pressure sensor for receiving the mud siren signal.

In another embodiment, the first multi-bit signal, the second multi-bit signal and the third multi-bit signal can each have at least or exactly two bits. In other words, the information that is encoded and transmitted by means of such a multi-bit signal at a coding time or during a time slot and is thus received during a corresponding reception time slot can have several bits, for example two bits, three bits, four bits, five bits, or even more bits.

Furthermore, the first frequency range and/or the second frequency range and/or the third frequency range may be less than or equal to approximately 50 Hz.

In various comparative examples, a method is provided for receiving and decoding a mud siren signal transmitted by a drilling fluid that is flushed through a plurality of mud sirens and through a drilling assembly. The method may include: receiving the mud siren signal transmitted by the drilling fluid; determining a frequency of the received mud siren signal; decoding the received mud siren signal into a first multi-bit signal if the determined frequency of the received mud siren signal is in a first frequency range; decoding the received mud siren signal into a second multi-bit signal if the determined frequency of the received mud siren signal is in a second frequency range; and decoding the received mud siren signal to a third multi-bit signal if the determined frequency of the received mud siren signal is in a third frequency range.

In another embodiment, the first multi-bit signal, the second multi-bit signal and the third multi-bit signal can each have at least or exactly two bits.

Furthermore, the first frequency range and/or the second frequency range and/or the third frequency range may be less than or equal to approximately 50 Hz.

In various embodiments, a mud siren assembly is provided, comprising: a stator having at least a first partial stator and at least a second partial stator; a first mud siren with a first rotor, the first mud siren having a first open cross-sectional area when the first partial stator and the first rotor at least partially overlap; a second mud siren with a second rotor, the second mud siren having a second open cross-sectional area when the second partial stator and the second rotor at least partially overlap; the second partial stator partially surrounding the first partial stator; the second rotor partially surrounding the first rotor; the second open cross-sectional area partially surrounding the first open cross-sectional area.

According to claim 2, the first partial stator can be part of the first mud siren and the second partial stator can be part of the second mud siren.

According to claim 3, the first partial stator part and the second partial stator part can be formed in one piece.

Such a mud siren arrangement clearly represents a parallel arrangement of two mud sirens. Clearly, the first mud siren is enclosed by at least one other mud siren. Both the first mud siren and the second mud siren can have one or more open cross-sectional areas (also referred to as a through opening). In various embodiments, the sum of the one or more open cross-sectional areas of the first mud siren can be equal to the sum of the one or more open cross-sectional areas of the second mud siren. With such dimensioning, the determination of the respective operating frequencies of the two mud sirens is made considerably easier.

In general, mud siren telemetry can be used with the mud siren arrangement according to various embodiments for faster transmission of the information (data) measured underground to the surface. With the mud siren arrangement according to various embodiments, the achievable data rate in a conventional hydraulic data transmission system can be multiplied (for example doubled or tripled) compared to a conventional mud siren. This allows the boreholes to be drilled more efficiently and safely, which can lead to a reduction in drilling costs.

Aspects of embodiments of the invention as well as comparative examples are shown in the figures and are explained in more detail below.

• 1 ein Spülungspuls-Telemetrie-System mit einem Bohrgestänge und einer Mud-Sirenen-Anordnung gemäß einem Vergleichsbeispiel;
• 2 eine Bohrgarnitur gemäß einem Vergleichsbeispiel;
• 3A bis 3D eine herkömmliche Mud-Sirene in verschiedenen Durchlass-Zuständen;
• 4 ein Diagramm, in dem eine Codierung einer Ein-Bit-Information zur Datenübertragung dargestellt ist zur Vereinfachung des Verständnisses der Erfindung;
• 5 eine Mud-Sirenen-Anordnung gemäß verschiedenen erfindungsbemäßen Ausführungsbeispielen;
• 6A bis 6H eine Darstellung von Zwei-Bit-Mud-Sirenen-Signalen im Zeitbereich und im Frequenzbereich zur Erläuterung der Erfindung;
• 7A bis 7D eine Mud-Sirenen-Anordnung gemäß verschiedenen Vergleichsbeispielen in verschiedenen Durchlass-Zuständen zur Vereinfachung des Verständnisses der Erfindung;
• 8 ein Diagramm zur Erläuterung der Erfindung, in dem die Änderung der offenen Querschnittsfläche der Mud-Sirenen-Anordnung aus 6A bis 6D im zeitlichen Verlauf dargestellt ist;
• 9A und 9B Diagramme zur Erläuterung der Erfindung, in denen eine Mud-Sirenen-Signal-Überlagerung von zwei Mud-Sirenen dargestellt ist;
• 10 ein Ablaufdiagramm, in dem ein Verfahren zum Codieren und Übertragen von einer Mehrfach-Bit-Information gemäß verschiedenen Vergleichsbeispielen dargestellt ist;
• 11 ein Ablaufdiagramm, in dem ein Verfahren zum Empfangen und Decodieren eines Mud-Sirenen-Signals gemäß verschiedenen Vergleichsbeispielen dargestellt ist
• 12 eine Darstellung eines Beispiels einer Übertragungsfunktion des Strömungskreislaufs in einem Bohrstrang;
• 13 eine Darstellung der Ermittlung einer Übertragungsfunktion und der Übertragung der Steuerungsparameter zwischen Übertage und Untertage;
• 14 eine Mud-Sirenen-Anordnung gemäß verschiedenen erfindungsgemäßen Ausführungsbeispielen;
• 15A bis 15E die Mud-Sirenen-Anordnung gemäß 14 in verschiedenen Durchlass-Zuständen;
• 16A und 16B Diagramme zur Erläuterung der Erfindung, in denen ein von der Mud-Sirenen-Anordnung gemäß 14 erzeugtes Mud-Sirenen-Signal im Zeitbereich (16A) und im Frequenzbereich (16B) dargestellt ist;
• 17 eine Mud-Sirenen-Anordnung gemäß verschiedenen erfindungsgemäßen Ausführungsbeispielen;
• 18 eine Querschnittsansicht der Mud-Sirenen-Anordnung gemäß 17;
• 19 ein Ablaufdiagramm, in dem ein Verfahren zum Ermitteln eines Signalspektrums gemäß verschiedenen Vergleichsbeispielen dargestellt ist, wie es beispielsweise bei den erfindungsgemäßen Ausführungsformen zur Anwendung kommen kann;
• 20 ein Ablaufdiagramm, in dem ein Verfahren zum Ermitteln eines Signalspektrums gemäß verschiedenen Vergleichsbeispielen dargestellt ist, wie es beispielsweise bei den erfindungsgemäßen Ausführungsformen zur Anwendung kommen kann;
• 21 ein Ablaufdiagramm, in dem ein Verfahren zum Ermitteln eines Signalspektrums gemäß verschiedenen Vergleichsbeispielen dargestellt ist, wie es beispielsweise bei den erfindungsgemäßen Ausführungsformen zur Anwendung kommen kann;
• 22 ein Ablaufdiagramm, in dem ein Verfahren zum Ermitteln eines Signalspektrums gemäß verschiedenen Vergleichsbeispielen dargestellt ist, wie es beispielsweise bei den erfindungsgemäßen Ausführungsformen zur Anwendung kommen kann;
• 23 ein Ablaufdiagramm, in dem ein Verfahren zum Ermitteln eines Signalspektrums gemäß verschiedenen Vergleichsbeispielen dargestellt ist, wie es beispielsweise bei den erfindungsgemäßen Ausführungsformen zur Anwendung kommen kann;
• 24 ein Ablaufdiagramm, in dem ein Verfahren zum Ermitteln eines Signalspektrums gemäß verschiedenen Vergleichsbeispielen dargestellt ist, wie es beispielsweise bei den erfindungsgemäßen Ausführungsformen zur Anwendung kommen kann; und
• 25 ein Ablaufdiagramm, in dem ein Verfahren zum Ermitteln eines Signalspektrums gemäß verschiedenen Vergleichsbeispielen dargestellt ist, wie es beispielsweise bei den erfindungsgemäßen Ausführungsformen zur Anwendung kommen kann.

Show it

• 1 a mud pulse telemetry system with a drill string and a mud siren arrangement according to a comparative example;
• 2 a drilling assembly according to a comparative example;
• 3A to 3D a conventional mud siren in various states of operation;
• 4 a diagram showing a coding of one-bit information for data transmission to facilitate the understanding of the invention;
• 5 a mud siren arrangement according to various embodiments of the invention;
• 6A to 6H a representation of two-bit mud siren signals in the time domain and in the frequency domain to explain the invention;
• 7A to 7D a mud siren arrangement according to various comparative examples in different transmission states to simplify the understanding of the invention;
• 8th a diagram to explain the invention, in which the change in the open cross-sectional area of the mud siren arrangement from 6A to 6D is shown over time;
• 9A and 9B Diagrams for explaining the invention, in which a mud siren signal superposition of two mud sirens is shown;
• 10 a flowchart showing a method for encoding and transmitting multiple-bit information according to various comparative examples;
• 11 a flowchart showing a method for receiving and decoding a mud siren signal according to various comparative examples
• 12 a representation of an example of a transfer function of the flow circuit in a drill string;
• 13 a representation of the determination of a transfer function and the transfer of the control parameters between above ground and underground;
• 14 a mud siren arrangement according to various embodiments of the invention;
• 15A to 15E the mud siren arrangement according to 14 in different conduction states;
• 16A and 16B Diagrams for explaining the invention, in which a signal generated by the mud siren arrangement according to 14 generated mud siren signal in the time domain ( 16A) and in the frequency range ( 16B) is shown;
• 17 a mud siren arrangement according to various embodiments of the invention;
• 18 a cross-sectional view of the mud siren arrangement according to 17 ;
• 19 a flow chart showing a method for determining a signal spectrum according to various comparative examples, as can be used, for example, in the embodiments according to the invention;
• 20 a flow chart showing a method for determining a signal spectrum according to various comparative examples, as can be used, for example, in the embodiments according to the invention;
• 21 a flow chart showing a method for determining a signal spectrum according to various comparative examples, as can be used, for example, in the embodiments according to the invention;
• 22 a flow chart showing a method for determining a signal spectrum according to various comparative examples, as can be used, for example, in the embodiments according to the invention;
• 23 a flow chart showing a method for determining a signal spectrum according to various comparative examples, as can be used, for example, in the embodiments according to the invention;
• 24 a flow chart showing a method for determining a signal spectrum according to various comparative examples, as can be used, for example, in the embodiments according to the invention; and
• 25 a flow chart showing a method for determining a signal spectrum according to various comparative examples, as can be used, for example, in the embodiments according to the invention.

In the following detailed description, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. In this regard, directional terminology such as "top", "bottom", "front", "back", "fore", "rear", etc. will be used with reference to the orientation of the figure(s) being described. Since components of embodiments may be positioned in a number of different orientations, the directional terminology is for purposes of illustration and is in no way limiting. It is to be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the present invention. It is to be understood that the features of the various exemplary embodiments described herein may be combined with one another, unless specifically stated otherwise. The following detailed description is therefore not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims.

In this description, the terms "connected", "connected" and "coupled" are used to describe both a direct and an indirect connection, a direct or indirect connection and a direct or indirect coupling. In the figures, identical or similar elements are provided with identical reference numerals where appropriate.

In a borehole, data recorded by the sensors can be transmitted in real time. This data can make an important contribution to safe and cost-effective drilling. Mud pulse telemetry systems can use coded pressure pulses (also known as carriers) to transmit measured information (e.g. directional and geological information) from the borehole and can be transmitted in coded form to the surface in real time.

Detecting the pulses and their characteristics (e.g. discontinuity locations, durations and frequencies) from a noise through a signal measured in the mud at a point on the standpipe can be very important for obtaining important information and for making drilling decisions during drilling.

1 shows a mud pulse telemetry system 100 in a borehole 108 with a drill string and a mud siren assembly according to an embodiment. In 1 a wireless telemetry system is shown that can be used for data transmission in boreholes in quasi real time. Sensors 104 can be arranged in a drilling assembly 102. The information detected, for example measured, by the sensors 104 can be transmitted by means of a transmitter 106 (eg by means of a mud siren arrangement (hereinafter also referred to as mud siren arrangement) within a borehole 108. A drill string 110 can be connected to a drill bit of the drilling assembly 102. Drilling mud 112 can be located in the borehole 108. Drilling mud pumps 116, mud tanks 118 and a drilling rig 120 (for example a drilling tower and a drilling mast) can be provided, for example, above the borehole 108.

According to various embodiments, different types of wireless telemetry systems may be used for transmission, e.g., quasi-real-time transmission, of data in boreholes. During drilling, one type of wireless telemetry system may be used for transmission. According to one embodiment, processing of the data may be used for any type of wireless telemetry system.

A telemetry system can be used to measure data from the sensors 104 in the borehole. The data can then be encoded. Then, depending on the telemetry system used, the data can be additionally modulated. The transmitter can be controlled to send the information to the surface of the borehole 108.

According to one embodiment, a system that may be called pressure pulse telemetry or mud pulse telemetry may be provided. According to one embodiment, the data is sent by generating encoded pressure waves 113 (in other words: pressure waves 113 in the drilling mud 112). The pressure waves 113 propagate through the drilling mud 112 within the drill string 110. At the surface of the borehole 108, a pressure transducer, e.g., a receiver 114, is used to measure the pressure signal. According to various embodiments, more than one sensor, e.g., more than one pressure transducer, e.g., more than one receiver, may also be used. The receiver may be connected to a computer 124 via a cable 122 of the pressure pulse telemetry system (or the receivers may be connected to one or more cables).

According to one embodiment, a system that may be called an electromagnetic telemetry system or an electrodynamic telemetry system may be provided.

According to one embodiment, a system that may be called an acoustic telemetry system may be provided.

The same principles of transmitting data or commands (such as orders or control commands) can be applied from the surface to a device in the borehole 108, e.g. to the tool in the borehole 108. This may be referred to as a "downlink" while the transmission of data from the borehole to the surface may be referred to as an "uplink".

In 1 In addition to the representation of the borehole 108, steps of a method according to a comparative example are also shown. In 138, sensors can collect data (in other words: carry out a measurement of data). In 140, the measured data can be coded. In 142, the coded signal can be modulated. In 144, the modulated signal can be sent. The signal can be sent by means of a mud siren arrangement, as explained above and described in more detail below.

The encoded information can be converted into transmitter actuations to induce or generate pulses (in other words, waves) that propagate in the drilling fluid to the surface (i.e., above ground).

For example, the mud siren arrangement described in more detail below can be used.

At the surface (i.e., above ground), a receiver 114 may be used to measure the pressure in the drilling fluid 112. According to various embodiments, more than one receiver 114 may be used. The receiver(s) 114 may be connected to a computer 124 via a cable 122 (or multiple cables). After receiving and measuring the pressure, the reverse process (demodulation 150, decoding 152, and noise filtering 148) may be performed in the computer 124 to extract the information.

In 148, the received signal can be subjected to noise filtering. In 150, the signal can be demodulated. In 152, the signal can be decoded. In 154, the data (in other words, the information) can be extracted, for example for a real-time decision. In 156, the information can be displayed to a user, for example a drilling supervisor.

2 shows the drilling set 102 from 1 according to one embodiment in detail. It should be noted that a different type of drilling set or a differently equipped drilling set can also be provided in various embodiments.

For example, the drilling assembly 102 includes a drill bit 200 and a plurality of sensors.

• - ein Inklinationssensor 202, mit dem ermittelt werden kann, welche Neigung die Bohrung hat;
• - ein Drucksensor 204, mit dem ermittelt werden kann, welcher Druck im Bohrloch 108 herrscht;
• - ein Gammasensor 206, mit dem beispielsweise eine Entfernung zu einer Oberkante einer Lagerstätte ermittelt werden kann;
• - ein Widerstandssensor 208, mit dem beispielsweise eine Entfernung zu einer Unterkante einer Lagerstätte ermittelt werden kann;
• - ein Richtungssensor 210, mit dem ermittelt werden kann, ob in gerader Richtung gebohrt wird;
• - ein Vibrationssensor 212, mit dem ermittelt werden kann, ob die Bohrung ruhig läuft oder vibriert;
• - ein Kalibersensor 214, mit dem ein Durchmesser der Bohrung ermittelt werden kann;
• - ein Dichtesensor 216, mit dem ermittelt werden kann, ob es Poren im Gestein gibt, in denen Öl oder Gas zu finden ist; und/oder
• - ein Porösitätssensor 218, mit dem ermittelt werden kann, ob es Poren im Gestein gibt, in denen Öl oder Gas zu finden ist.

For example, one or more of the following sensors may be provided in the drilling assembly 102:

• - an inclination sensor 202, which can be used to determine the inclination of the borehole;
• - a pressure sensor 204, which can be used to determine the pressure prevailing in the borehole 108;
• - a gamma sensor 206, with which, for example, a distance to an upper edge of a deposit can be determined;
• - a resistance sensor 208, with which, for example, a distance to a lower edge of a deposit can be determined;
• - a direction sensor 210, which can be used to determine whether drilling is taking place in a straight direction;
• - a vibration sensor 212, which can be used to determine whether the bore is running smoothly or vibrating;
• - a caliber sensor 214, with which a diameter of the bore can be determined;
• - a density sensor 216 which can be used to determine whether there are pores in the rock in which oil or gas can be found; and/or
• - a porosity sensor 218, which can be used to determine whether there are pores in the rock in which oil or gas can be found.

According to various embodiments, the measured data may include information measured during drilling to monitor and control the borehole progress (so-called MWD data), information logged during drilling to obtain information about the nature of the drilled rock (so-called LWD data), and data about the dynamic state of the drill string 110 and/or the drilling assembly 102 during drilling (vibrations, impacts, etc.).

For example, MWD data can contain direction data (inclination, azimuth and tool orientation).

For example, LWD data may include data on gamma radiation, resistivity, density, porosity, caliper, pressure, temperature, seismic activity during drilling, speed of sound, rock hardness, permeability, borehole images, and/or mud properties (such as resistivity, density, hydrogen sulfide content, temperature, and/or pressure).

Data on drilling dynamics may include the weight on bit force and/or torque on the drill bit 200 and in the drill string 102 and bending moments together.

According to various embodiments, real-time services may benefit or be provided based on telemetry data, and the real-time services may benefit from the telemetry data. The real-time services may include directional drilling, reservoir navigation, drilling optimization, borehole stability, and/or pressure management. This may result in increased production and/or productivity, reduced drilling costs, facilitated risk management, and/or safer drilling.

Furthermore, the drilling assembly 102 can have a mud siren assembly 222 according to various embodiments, as will be explained in more detail below. The mud siren assembly 222 can be provided at the end of the drilling assembly 102 that is opposite the end to which the drill bit 200 is attached.

According to various embodiments, the mud siren assembly 222 can be used in all types of wells, from shallow to deep wells, even when using mud loss containment materials. It can be used in reservoir navigation applications or in seismic-while-drilling applications, i.e. in applications where high data transmission rates are required.

For a more detailed explanation of pressure pulse telemetry, reference is first made to 3A until 3D and 4 the structure and functionality of a conventional Mud Siren 300 is shown.

The conventional mud siren 300 typically has a stationary stator 302 (with one or more stationary stator blades 304, in the example four stator blades 304 are shown, but in general the number of stator blades 304 can be any) and a rotor 310 (with one or more rotor blades 312, in the example four rotor blades 312 are shown, but in general the number of rotor blades 312 can be any). The rotor 310 is mounted so as to be rotatable about an axis. The stator 302 is designed such that the stator blade 304 or the stator blades 304 define one or more flow openings 306 through which the drilling fluid 112 can flow when the mud siren 300 is inserted into the drill string 110. The stator blade 304 or the stator blades 304 clearly block the drilling fluid 112 in the drill string 110. For example, the stator blades 304 form circular segments whose outer circumference defines the outer circumference of the mud siren 300. The rotor blade 312 or the rotor blades 312 rotate about an axis, which is usually a common axis with the stator 302. Depending on the position of the rotor blade(s) 312 relative to the stator blade(s) 304, more or less of the area of the one or more flow openings 306 of the stator 302 is covered, whereby more or less of the drilling fluid 112 passed through by the stator 302 is still blocked. In this way, the amount of drilling fluid 112 that can flow through the mud siren 300 per unit of time is varied, whereby the pressure within the drilling fluid 112 can be varied. This pressure change can be detected above ground by means of one or more pressure sensors and data can be transmitted in this way. Usually, but not necessarily, the rotor blades 312 are designed relative to the stator blades 304 such that they can cover substantially the entire area of the flow openings 306 at least in one position, thus allowing the mud siren 300 to flow through the drilling flushing 112 is substantially completely blocked and thus prevented. The rotor 310 can be rotated, for example, clockwise or counterclockwise relative to the stator 302.

3A shows the conventional mud siren 300 in a first state in which the rotor blades 312 are substantially completely overlapped with the stator blades 304. 3B shows the mud siren 300 in a second state in which the rotor blades 312 are partially overlapped with the stator blades 304 and partially cover the flow openings 306; in this way, the amount of drilling fluid 112 that can flow through the flow openings 306 per unit of time is reduced compared to the first state. 3C shows the mud siren 300 in a third state in which the rotor blades 312 are substantially completely covered by the flow openings 306, thereby substantially completely preventing the drilling fluid 112 from flowing through the mud siren 300. 3D shows the mud siren 300 in a fourth state, in which the rotor blades 312 are again partially overlapping with the stator blades 304 and partially covering the flow openings 306; thus, at least compared to the third state, it is now again possible for a certain amount of drilling fluid 112 to flow through the mud siren 300.

This cyclical rotation of the rotor 310 relative to the stator 302 generates a pressure oscillation in the drilling fluid 112, which can be detected above ground by the pressure sensor(s).

4 shows a diagram 400 in which a coding of a one-bit information for data transmission is shown. The diagram 400 shows a pressure curve over time. As shown in the diagram 400, a first bit value "1" is assigned to a first operating state (for example "state 1" (also referred to as the first frequency)) of the mud siren 300 and a second bit value "0" is assigned to a second operating state (for example "state 2" (also referred to as the second frequency)) of the mud siren 300. Each of these two states generates a characteristic pressure curve in the drilling fluid 112 in a respective time slot 402 (a first pressure curve 404 for the first bit value "1" and a second pressure curve 406 for the second bit value "0"), which can be detected by means of the pressure sensors. In this way, a binary bit sequence can now be encoded and transmitted (in the 4 In the example shown, the bit sequence “11010” is encoded).

It should be noted that any other type of modulation, including all types of modulation currently known per se, can be used in various embodiments. For example, a first bit value "1" is assigned to a first operating state (for example "activated state" (on)) of the mud siren and a second bit value "0" is assigned to a second operating state (for example "deactivated state" (off)) of the mud siren (this modulation is used below to explain the various embodiments).

Conventionally, however, only exactly one bit is encoded and transmitted per time slot.

Table 1 shows a corresponding coding for a conventional mud siren (an activated state (On) of the mud siren is assigned a first bit value of “1” and a deactivated state (Off) of the mud siren is assigned a second bit value of “0”): Table 1: Coding for a conventional mud siren with a frequency Mud Siren One-bit coding At 1 Out of 0

In order to multiply the achievable data rate, the mud siren arrangement according to various embodiments can simultaneously (i.e. in a common time slot) generate pressure waves in the drilling fluid with several different frequencies, for example two or three or more frequencies simultaneously, independently of one another. With such a mud siren arrangement according to various embodiments, several bits of information can then be transmitted per unit of time (generally at a respective coding time), for example per predetermined time slot (predetermined length) in a transmission scheme with a large number of time slots, instead of conventionally only one bit of information per unit of time (for example per time slot). This is shown by way of example in Table 1 and Table 2. A time slot can, for example, have a respective time duration in a range from approximately 0.1 seconds to approximately 1 second, for example in a range of about 0.2 seconds to about 0.9 seconds, for example in a range of about 0.2 seconds to about 0.8 seconds.

Table 2 shows an example of a coding for a mud siren arrangement according to various embodiments with a first mud siren and a second mud siren that are operated at different frequencies (an activated state (on) of the respective mud siren is assigned a respective first bit value "1" and a deactivated state (off) of the respective mud siren is assigned a respective second bit value "0"): Table 2: Coding for a mud siren arrangement according to various embodiments with a first mud siren and a second mud siren with two independent frequencies First Mud Siren Second Mud Siren Sign Out of Out of 0 0 Out of At 0 1 At Out of 1 0 At At 1 1

• - erste Mud-Sirene deaktiviert (ausgeschaltet) und zweite Mud-Sirene deaktiviert (ausgeschaltet):
  • erste Bit-Wert-Kombination „0 0“;
• - erste Mud-Sirene deaktiviert (ausgeschaltet) und zweite Mud-Sirene aktiviert (angeschaltet):
  • zweite Bit-Wert-Kombination „0 1“;
• - erste Mud-Sirene aktiviert (angeschaltet) und zweite Mud-Sirene deaktiviert (ausgeschaltet):
  • dritte Bit-Wert-Kombination „1 0“; und
• - erste Mud-Sirene aktiviert (angeschaltet) und zweite Mud-Sirene aktiviert (angeschaltet):
  • vierte Bit-Wert-Kombination „1 1“.

This results in the following state combinations of the two mud sirens per coding point in time (e.g. per time slot), each of which is assigned a unique 2-bit value:

• - first mud siren deactivated (switched off) and second mud siren deactivated (switched off):
  • first bit-value combination “0 0”;
• - first mud siren deactivated (switched off) and second mud siren activated (switched on):
  • second bit-value combination “0 1”;
• - first mud siren activated (switched on) and second mud siren deactivated (switched off):
  • third bit-value combination “1 0”; and
• - first mud siren activated (switched on) and second mud siren activated (switched on):
  • fourth bit-value combination “1 1”.

In general, with n independently adjustable frequencies (and thus with n mud sirens in a mud siren arrangement according to various embodiments), a number of n bits can be coded and transmitted per coding time, i.e. per time unit (for example per time slot).

5 shows a mud siren arrangement 500 according to various embodiments.

The mud siren arrangement 500 comprises a plurality of at least two mud sirens 502, 504, in which 5 In the example shown, there is a first mud siren 502 and a second mud siren 504. The two mud sirens 502, 504 can be arranged in a drilling assembly (for example in the drilling assembly 102), in this example clearly in a series connection, i.e. one behind the other within the drilling assembly 102 in the flow direction of the drilling fluid 112. Furthermore, a coding device 506 is provided (for example implemented in the form of a computer), which is electrically connected to both the first mud siren 502 and the second mud siren 504, wherein the coding device 506 is connected to the first mud siren 502, for example by means of a first electrical connection 508 (for example a first cable 508) and is connected to the second mud siren 504 by means of a second electrical connection 510 (for example a second cable 510).

As will be explained in more detail below, the first mud siren 502 and the second mud siren 504 are arranged, for example, within the drilling assembly 102 and the coding device 506 controls the first mud siren 502 and the second mud siren 504 in such a way that at a coding time (for example at the beginning of a time slot of a predetermined duration) information comprising several bits is encoded and transmitted by means of the first mud siren 502 and the second mud siren 504. The coding can be carried out in a manner as shown in Table 2 above.

The coding device 506 is further configured to communicate with one or more sensors, which are also included in the drill string 102, for example with one or more sensors as described in connection with 2 described above. For example, the coding device 506 can be set up to read out sensor values which have been recorded by the sensor(s), optionally in addition to carrying out signal processing of the read out data and to encode the read out data in digital form and to transmit the encoded data by means of the at least two mud sirens 502 and 504. The coding device 506 is thus clearly set up to communicate with a receiver which is arranged above ground above the borehole 110 by controlling the mud sirens 502, 504 to generate pressure waves in the pressure flush 112 with different frequencies, as will be explained in more detail below.

It should be noted in this context that in principle any number of mud sirens can be provided in the mud siren arrangement 500 in order to further increase the achievable data rate. Such a mud siren arrangement 500, which has several mud sirens 502, 504, which are operated at different frequencies, can also be referred to as a multi-tone siren.

A basic idea of such a mud siren arrangement 500 is that the more frequencies are used simultaneously for data transmission, the more characters (also referred to as symbols or code words) can be transmitted per time slot (also referred to as slot). Table 2 shown and explained above illustrates this basic idea for a mud siren arrangement with two adjustable frequencies. It can initially be assumed that in this case two characters could be transmitted simultaneously per time slot.

However, in various tests it has been found that if two Mud Sirens 502, 504 are connected in series, as in 5 As shown, when the two mud sirens 502, 504 are operated simultaneously (generally when several mud sirens are operated simultaneously), interference frequencies are generated which make data transmission more difficult.

This situation is illustrated below using a non-limiting concrete example. A series connection of two mud sirens, such as mud sirens 502, 504, was installed on a test facility, in which the mud sirens 502, 504 were set (using the coding device 506) so that the first mud siren 502 generated a 15 Hz tone and the second mud siren 504 generated a 39 Hz tone. When only the first mud siren 502 of the two mud sirens 502, 504 of this mud siren arrangement 500 was operated, a 15 Hz tone was induced in the drilling fluid 112, which could be registered in a robust manner by the receiver 114. When the second mud siren 504 was operated alone, a 39 Hz tone was induced in the drilling fluid 112, which could also be registered by the receiver 114 in a robust manner. However, when the two mud sirens 502, 504 were operated simultaneously (operation of the first mud siren 502 to generate a 15 Hz tone and operation of the second mud siren 504 to generate a 39 Hz tone), two dominant frequencies were created, which in this example were 15 Hz and 24 Hz.

It has thus been found that in this example, when several mud sirens are operated simultaneously, which are connected in series (in other words, arranged in series), the multi-tone siren does not induce the two individual frequencies set for the respective mud sirens 502, 504 into the drilling fluid 112 and thus into the pipe system, but rather the lower set frequency (i.e. the frequency at which the first mud siren 502 is operated, thus 15 Hz) and the difference between the two set individual frequencies (in this specific case, therefore 39 Hz -15 Hz = 24 Hz). At other speeds (frequencies), different acoustic relationships arise under the respective operating conditions. The dominant frequencies that arise when the first mud siren 502 and the second mud siren 504 are operated simultaneously, as described above, are shown in a frequency diagram 512 in 5 shown.

Furthermore, 5 an optional pump 514 which pumps the drilling fluid from 112 through the drill string 102 and then through the drilling assembly 102.

For data transmission using such a mud siren arrangement 500, this means that with such a series connection of the two mud sirens 502, 504 according to this embodiment, three frequencies are used for data transmission, as shown in the following Table 3: Table 3: Coding and the frequencies used for data transmission in a mud siren arrangement according to various embodiments with a first mud siren and a second mud siren with two independent frequencies First Mud Siren Second Mud Siren 15Hz 39Hz 24Hz Sign Out of Out of - - - 0 0 Out of At - + - 0 1 At Out of + - - 10 At At + (-) + 1 1

The symbol "-" indicates that the respective frequency is not contained in the generated mud siren signal. The symbol "+" indicates that the respective frequency is contained in the generated mud siren signal. The symbol "(-)" indicates that the respective frequency is not contained in the generated mud siren signal at a strength that could be used for data transmission using, for example, the drilling fluid.

• - erste Mud-Sirene 502 deaktiviert (ausgeschaltet) und zweite Mud-Sirene 504 deaktiviert (ausgeschaltet):
  • erste Bit-Wert-Kombination „0 0“;
  • auf den Betriebsfrequenzen der Mud-Sirenen 502, 504 wird kein veränderliches Druckwellensignal erzeugt und übertragen;
• - erste Mud-Sirene 502 deaktiviert (ausgeschaltet) und zweite Mud-Sirene 504 aktiviert (angeschaltet):
  • zweite Bit-Wert-Kombination „0 1“;
  • es wird ein veränderliches Druckwellensignal auf der Betriebsfrequenz der ersten Mud-Sirene 502 (15 Hz) erzeugt und übertragen;
• - erste Mud-Sirene 502 aktiviert (angeschaltet) und zweite Mud-Sirene 504 deaktiviert (ausgeschaltet):
  • dritte Bit-Wert-Kombination „1 0“;
  • es wird ein veränderliches Druckwellensignal auf der Betriebsfrequenz der zweiten Mud-Sirene 504 (39 Hz) erzeugt und übertragen; und
• - erste Mud-Sirene 502 aktiviert (angeschaltet) und zweite Mud-Sirene 504 aktiviert (angeschaltet):
  • vierte Bit-Wert-Kombination „1 1“
  • es wird ein veränderliches Druckwellensignal auf der Differenzfrequenz (24 Hz) aus der Betriebsfrequenz der zweiten Mud-Sirene 504 (39 Hz) und der Betriebsfrequenz der ersten Mud-Sirene 502 (15 Hz) erzeugt und übertragen.

This results in the following state combinations of the two mud sirens for each coding time (for example, per time slot), each of which is assigned a unique 2-bit value, with different frequencies being used for data transmission via the drilling fluid 112:

• - first mud siren 502 deactivated (switched off) and second mud siren 504 deactivated (switched off):
  • first bit-value combination “0 0”;
  • no variable pressure wave signal is generated and transmitted on the operating frequencies of the mud sirens 502, 504;
• - first mud siren 502 deactivated (switched off) and second mud siren 504 activated (switched on):
  • second bit-value combination “0 1”;
  • a variable pressure wave signal is generated and transmitted at the operating frequency of the first Mud Siren 502 (15 Hz);
• - first mud siren 502 activated (switched on) and second mud siren 504 deactivated (switched off):
  • third bit-value combination “1 0”;
  • a variable pressure wave signal is generated and transmitted at the operating frequency of the second Mud Siren 504 (39 Hz); and
• - first mud siren 502 activated (switched on) and second mud siren 504 activated (switched on):
  • fourth bit-value combination “1 1”
  • a variable pressure wave signal is generated and transmitted at the difference frequency (24 Hz) between the operating frequency of the second mud siren 504 (39 Hz) and the operating frequency of the first mud siren 502 (15 Hz).

6A until 6H show a representation of two-bit mud signals in the time domain and the frequency domain.

The respective pressure wave signals in the drilling fluid are thus clearly shown in the time domain and in the frequency domain for the four characters, which can be coded using two bits. In the time domain, the signal is shown for a period of time (i.e. for a time slot of duration) 0.7 seconds. In the frequency domain, the range from 0 Hz to 100 Hz is shown. The signal in the frequency domain represents a fast Fourier transformation of the respective time signal. In general, however, any other spectral transformation can also be used to determine the respective frequency ranges.

A first time diagram 600 in 6A shows essentially no change in the pressure in the drilling fluid (first mud siren 502 is deactivated and second mud siren 504 is deactivated) over the entire period of 0.7 seconds (see first time signal 602), and thus essentially no significant change in the frequency response (see first frequency signal 612 in a first frequency diagram 610 in 6B) . Such a first time signal is thus used to encode the character "0 0" with two bits. After calibration, as explained in more detail below, the receiver is set to detect signals in various frequency ranges, each of which is assigned to a coded character. If the receiver (for example receiver 114) does not detect a signal whose amplitude is above a predetermined first threshold value over the entire frequency range from 0 Hz to 100 Hz, for example, it decodes the signal in the respective time slot to the character "0 0".

A second timing diagram 620 in 6C shows a sinusoidal curve of the change in the pressure in the drilling fluid (first mud siren 502 is activated and second mud siren 504 is deactivated) over a period of 0.7 seconds (see second time signal 622), which shows a frequency component in the frequency domain that essentially represents the operating frequency of the first mud siren 502 of 15 Hz (see second frequency signal 632 in a second frequency diagram 630 in 6D ). Such a second time signal is thus used to encode the character "1 0" with two bits. If the receiver (for example receiver 114) detects, for example, a signal that has at least one spectral component in a first frequency range (for example in a frequency range from 12 Hz to 18 Hz) whose amplitude is above a predetermined second threshold value, it decodes the signal in the respective time slot to the character "1 0". In this example, a clear spectral component can be seen in the first frequency range with a maximum in a range of approximately 15 Hz, whereby the receiver would decode the character "1 0" for this time slot.

A third timing diagram 640 in 6E also shows an approximately sinusoidal curve of the change in pressure in the drilling fluid (first mud siren 502 is deactivated and second mud siren 504 is activated) over a period of 0.7 seconds (see third time signal 642), which shows a frequency component in the frequency domain that essentially represents the operating frequency of the second mud siren 504 of 39 Hz (see third frequency signal 652 in a third frequency diagram 650 in 6F) . Such a third time signal is thus used to encode the character "0 1" with two bits. If the receiver (for example receiver 114) detects, for example, a signal that has at least one spectral component in a second frequency range (for example in a frequency range from 37 Hz to 41 Hz) whose amplitude is above a predetermined third threshold value, it decodes the signal in the respective time slot to the character "0 1". In this example, a clear spectral component can be seen in the second frequency range with a maximum in a range of approximately 39 Hz, whereby the receiver would decode the character "0 1" for this time slot.

• - eine erste Frequenzkomponente 672, die im Wesentlichen die Betriebsfrequenz der ersten Mud-Sirene 502 von 15 Hz repräsentiert (siehe viertes Frequenzsignal 678 in einem vierten Frequenzdiagramm 670 in 6H);
• - eine zweite Frequenzkomponente 676, die im Wesentlichen die Betriebsfrequenz der zweiten Mud-Sirene 504 von 39 Hz repräsentiert; und
• - eine dritte Frequenzkomponente 674, die im Wesentlichen die Differenz der beiden obigen Betriebsfrequenzen (in einem anderen Beispiel kann die Beziehung zu den Betriebsfrequenzen anders sein), von 24 Hz repräsentiert.

A fourth timing diagram 660 in 6G also shows a superposition of several sinusoidal signals, which represent the course of the change in pressure in the drilling fluid (first mud siren 502 is activated and second mud siren 504 is activated) over a period of 0.7 seconds (see third time signal 642). In the frequency range, several frequency components with a relevant amplitude arise, namely

• - a first frequency component 672 which essentially represents the operating frequency of the first mud siren 502 of 15 Hz (see fourth frequency signal 678 in a fourth frequency diagram 670 in 6H) ;
• - a second frequency component 676 which substantially represents the operating frequency of the second mud siren 504 of 39 Hz; and
• - a third frequency component 674 which essentially represents the difference of the two operating frequencies above (in another example the relationship to the operating frequencies may be different), of 24 Hz.

Such a fourth time signal 662 is thus used to encode the character "1 1" with two bits. If the receiver (for example receiver 114) detects, for example, a signal that has at least one spectral component in a third frequency range (for example in a frequency range from 22 Hz to 26 Hz) whose amplitude is above a predetermined fourth threshold value, it decodes the signal in the respective time slot to the character "1 1". In this example, a clear spectral component can be seen in the third frequency range with a maximum in a range of approximately 24 Hz, whereby the receiver would decode the character "1 1" for this time slot.

When using three or more mud sirens in a series connection with different operating frequencies, the relationships between the individually set operating frequencies of the mud sirens and the frequencies induced in the drilling fluid and thus in the pipe system are zen (especially when several mud sirens are active at the same time), but in principle they are of the same nature. The individual operating frequencies set on the mud sirens are partly drowned out by other frequencies in the drilling fluid and thus in the pipe system, so the receiver(s) should be calibrated accordingly.

This clearly shows that when several mud sirens are connected in series, additional frequencies are generated during operation, which in some cases significantly overlay the set basic frequencies (also referred to as individual operating frequencies) of the respective individual mud sirens and are therefore taken into account during decoding on the receiver side.

As described above, when several mud sirens connected in series are operated simultaneously (where a first mud siren, operated individually, generates a first frequency f1 and another (second) mud siren, operated individually, generates a second frequency f2), a multi-tone is generated that contains frequencies (interference frequencies) other than the frequencies actually to be generated (f1 and f2). The interference frequencies are sometimes significantly louder than the set fundamental frequencies (f1 or f2). This effect of "detuning" was recognized according to various embodiments and transferred to a coding process and taken into account therein (for example in a model for calculating the operating frequencies required in each case to generate the desired transmission frequencies within the drilling fluid). This model is used in various embodiments to calculate the speeds at which the individual mud sirens connected in series must be operated in order to create the desired dominant frequencies in the pressure wave of the drilling fluid, which are to be used for data transmission. It should be noted that in various embodiments the different frequencies can alternatively or additionally be realized by setting a corresponding number of rotor blades and/or stator blades. Various models for calculating the respective frequencies are explained in more detail below.

Thus, according to various comparative examples, a method is provided with which a series connection of several individual mud sirens can be constructed, configured and operated, which generates freely selectable multi-tones that can be used for faster data transmission.

To make it easier to understand the “detuning” of the multi-tone mud siren arrangement, the signal generation is first explained using a simplified mud siren arrangement in which the mud siren has only one stator blade and one rotor blade.

First, the size of the resulting open cross-sectional area (hereinafter also referred to as total flow area (TFA)) for the flow (for example for the drilling fluid) is shown when a single mud siren is operated (see 7A until 7D ). The mud siren 700 has a rotor 702 with exactly one rotor blade and a stator 704 with exactly one stator blade. The cross-sectional area depends on the angle of rotation α of the rotor 702. In the 7A until 7D different rotor positions of the rotor 702 are shown. For the sake of simplicity, both the rotor blade of the rotor 702 and the stator blade of the stator 704 are assumed to be semicircles. This means that the maximum possible TFA, also referred to below as TFA _max , is also half a circle. When the mud siren 700 is put into operation, the rotor position and thus the TFA changes over time. The TFA change over time (in other words, the time course 802 of the TFA) is shown in 8th shown in a TFA diagram 800 for the mud siren 700. The time course 802 of the TFA results for this simplified case as a signal in sawtooth form.

If the angle of rotation α of the rotor 702 relative to the stator 704 is 0° or 360° (cf. 7A) , the rotor blade of the rotor 702 essentially completely closes the free cross-sectional area 706 and thus no medium, for example no liquid, for example no water (and thus possibly no drilling fluid) can flow through the mud siren 700. In this case, the TFA is the minimum TFA _min (see points A and E in the TFA diagram 800). It should be noted, however, that in practice the fluid flow should never be completely closed because otherwise a so-called strong "water hammer effect" occurs. Thus, in a practical implementation of various embodiments, a small gap will usually remain open between the mud sirens. If the angle of rotation α of the rotor 702 relative to the stator 704 is 90° (cf. 7B) , the TFA is half of TFA _max (see point B in the TFA diagram 800). If the angle of rotation α of the rotor 702 relative to the stator 704 is 180°, the rotor blade of the rotor 702 is essentially completely behind the stator blade of the stator 704 and exposes the entire semicircular cross-section, in other words the entire open cross-sectional area 706 (cf. 7C ). In this case, the TFA is the maximum TFAmax (see point C in the TFA diagram 800). If the angle of rotation α of the rotor 702 relative to the stator 704 is 270° (cf. 7D ), the TFA is half of TFA _max (see point D in the TFA diagram 800).

Analogously, a series connection of two mud sirens is now considered. The mud sirens are to be operated at different frequencies. Thus, each rotor 702 of the respective mud siren has its own time-dependent angle of rotation. Accordingly, each mud siren generates its own TFA curve in the time domain and in the frequency domain, which are, however, similar to the one in 8th shown TFA curve.

Since the medium, for example the drilling fluid, that flows through the mud siren can be regarded as essentially incompressible, at a certain differential pressure that is assumed to be constant across the respective mud sirens, only as much medium, for example water, for example drilling fluid, can flow through the series connection of several mud sirens as fits through the mud siren that has the smallest TFA of all the mud sirens in the series connection.

9A and 9B show diagrams showing a mud signal overlay from two mud sirens. 9A shows the overlay in the time domain in a time diagram 900 and 9B shows the superposition in the frequency domain in a frequency diagram 910.

9A and 9B thus clearly illustrate the situation for a series connection of two mud sirens, which are operated at different frequencies, in this case for example at 15 Hz or 39 Hz.

9A shows in a first characteristic curve 902 how the TFA of the series connection of several mud sirens changes over time if the smaller TFA of the two mud sirens is considered to be decisive for the flow through the series connection of the mud sirens.

9B shows in a second characteristic curve 912 the result of a spectral transformation (in other words a frequency analysis) which has been applied to the first characteristic curve 902. For example, a Fast Fourier Transformation is applied to the first characteristic curve 902, resulting in the second characteristic curve 912. From 9B it can be seen that the series connection of the math sirens actually describes the "detuning" observed in the experiment described above. The two set frequencies 15 Hz (frequency component is designated with reference number 914) and 39 Hz (frequency component is designated with reference number 916) are shown, but also additional interference frequencies that arise, for example the interference frequency at 24 Hz described above (frequency component is designated with reference number 918).

This understanding is used in various embodiments in a corresponding mathematical model to calculate the speed at which the respective individual (for example two) mud sirens must be operated so that two or more desired frequencies are induced in the flow (for example in the drilling fluid). The operation of a multi-frequency mud siren is thus made possible.

10 shows a flowchart illustrating a method 1000 for encoding and transmitting multiple-bit information.

At the beginning of the method, a transfer function of a flow circuit in a pipe system in which the data is transmitted, for example a transfer function of the drill string 110 filled with the transmission medium, for example the drilling fluid 112, is usually determined (block 1002) as part of a "calibration phase". In this sub-process, it is clearly determined which frequencies are particularly suitable for data transmission of the specific system; in other words, which frequencies' signals are sufficiently attenuated during the pressure wave signal transmission in the drill string 110 so that the pressure wave signals can still be received above ground by the receiver 114 in sufficient quality.

The determination and subsequent determination of the frequencies that are sufficiently suitable for data transmission must be carried out individually for each application and for each pipe system, i.e. for each drill string 110. Since the transfer function changes with each new drill rod screwed on, the transfer function must be determined again and again during operation. Due to reflections and Due to interference in the drill string 110, some frequencies are amplified and others are attenuated or even completely eliminated. Depending on the dimensions of the drill string 110, the position of the receiver 114 (i.e. the position of one or more sensors, e.g. pressure sensors), for example on the riser pipe, and the nature of the drilling fluid 112, different individual pass frequency bands and stop frequency bands result for the transmission channel, and thus frequencies (i.e. signals with such frequencies) that can be transmitted and detected between the underground transmitter and the above-ground receiver 114 and such frequencies (i.e. signals with such frequencies) that are attenuated too much and can therefore no longer be detected by the receiver. If the amplitude of the signal arriving at the receiver 114 is related to the amplitude(s) of the signal generated by the mud siren, the so-called transfer function of the channel is obtained, in various embodiments the transfer function of the drill string 110 filled with the drilling fluid 112.

In various embodiments, a transfer function 1200 (see 12 ) is determined experimentally. For this purpose, for example, a so-called sweep is generated at the transmitter (i.e. at the mud siren(s)) (i.e. signals are generated with all frequencies and constant amplitude, in other words, all frequencies are scanned with constant amplitude), and the signal (i.e. the pressure wave signal) that arrives at the receiver 114 is measured in each case. The signals with the frequencies that arrive at the receiver 114 with the largest amplitudes indicate the frequencies that are best suited for data transmission in the specific pipe system, for example the specific drill string 110.

12 shows an experimentally determined transfer function 1200. Signals with frequencies in a frequency range of 10 Hz to 70 Hz were set at the transmitter and the signal strength (amplitude) was measured at a receiver of a pipe system. The result was, as shown in 12 shown, several frequency ranges in which the signals arrive at the receiver (for example at the receiver 114) with a large amplitude, or in other words, are received. These frequency ranges are, for example, in the frequency ranges from approximately 10 Hz to approximately 18 Hz (first frequency range 1202), from approximately 35 Hz to approximately 46 Hz (second frequency range 1204), and from approximately 55 Hz to approximately 65 Hz (third frequency range 1206). It should be noted that the transfer function 1200 is very dependent on the specific pipe system or drill string and the drilling fluid. Thus, such a transfer function 1200 is only ever valid for a specific pipeline or pipe system being examined and cannot simply be applied to other pipe systems or other drill strings with sufficient accuracy. Any change in the pipe system or drill string and/or the drilling fluid, generally the transmission medium) or even a different positioning of the receiver (for example of the one or more pressure sensors) in the system changes the transmission behavior and thus also the resulting transfer function.

After the frequency bands have been determined (i.e., after the transfer function has been determined) in which signal transmission with sufficiently low attenuation is possible, at least three frequencies are determined that are to be used for transmitting data in the pipe system, for example in the drill string 110 (block 1004).

As will be explained in more detail below, the determination of the transfer function and also the determination of the at least three frequencies can be carried out by a surface computer (for example, the computer 112).

Subsequently, in 1006, at least two of the three determined frequencies can be transmitted to the coding device 506 in the drill string 102. The transmitted frequencies indicate to the coding device 506 the operating frequencies of the at least two mud sirens 502, 504. The transmission in the downlink of the at least two frequencies can be carried out by transmitting the absolute value or by an index or by any other type of direct or indirect (referenced) transmission of the frequency values.

After the coding device 506 has now received the control information, in other words the control instruction is now available, i.e. clearly the information on which frequencies the two mud sirens (for example the at least two mud sirens 502, 504) are to be operated with, the coding device 506 begins the transmission of data (from underground to above ground) by encoding the data to be transmitted in characters (symbols) each of at least two bits in length, as described above, and transmits this multiple-bit information per time slot (in other words, one character or symbol per time slot) to the receiver 114 by means of the corresponding control of the two mud sirens 502, 504. Thus, in 1008, information comprising multiple bits is encoded and transmitted by operating at least two mud sirens 502, 504 with the two transmitted frequencies in accordance with the respective predetermined encoding rule, as shown and described, for example, in Table 3 above.

11 shows a flowchart illustrating a method 1100 for receiving and decoding a mud siren signal.

The pressure waves generated by the mud sirens 502, 504 in the pipe system, for example in the drilling fluid 112 of the drill string 110, are received above ground by means of a receiver which has, for example, one or more pressure sensors, for example by means of the receiver 114. In other words, a mud siren signal is received (block 1102).

As part of the reception of the mud siren signal 1102 and/or after the reception of the mud siren signal 1102, the at least one signal frequency of the received mud siren signal is determined, in other words, the one or more frequency components of the received mud siren signal are determined (block 1104).

• - Das empfangene Mud-Sirenen-Signal kann zu einem ersten Mehr-Bit-Signal decodiert werden, wenn die ermittelte Frequenz des empfangenen Mud-Sirenen-Signals in einem ersten Frequenzbereich liegt; so kann beispielsweise das empfangene Mud-Sirene-Signal gemäß der oben dargestellten Tabelle 3 zu der Bitsequenz „1 0“ für einen jeweiligen Zeitschlitz decodiert werden, wenn das empfangene Mud-Sirenen-Signal in einem jeweiligen Zeitschlitz im Wesentlichen eine Frequenz aufweist, die der Betriebsfrequenz der ersten Mud-Sirene entspricht, also beispielsweise eine Frequenz von ungefähr 15 Hz aufweist.
• - Das empfangene Mud-Sirenen-Signal kann zu einem zweiten Mehr-Bit-Signal decodiert werden, wenn die ermittelte Frequenz des empfangenen Mud-Sirenen-Signals in einem zweiten Frequenzbereich liegt; so kann beispielsweise das empfangene Mud-Sirene-Signal gemäß der oben dargestellten Tabelle 3 zu der Bitsequenz „0 1“ für einen jeweiligen Zeitschlitz decodiert werden, wenn das empfangene Mud-Sirenen-Signal in einem jeweiligen Zeitschlitz im Wesentlichen eine Frequenz aufweist, die der Betriebsfrequenz der zweiten Mud-Sirene entspricht, also beispielsweise eine Frequenz von ungefähr 39 Hz aufweist.
• - Das empfangene Mud-Sirenen-Signal kann zu einem dritten Mehr-Bit-Signal decodiert werden, wenn die ermittelte Frequenz des empfangenen Mud-Sirenen-Signals in einem dritten Frequenzbereich liegt; so kann beispielsweise das empfangene Mud-Sirene-Signal gemäß der oben dargestellten Tabelle 3 zu der Bitsequenz „1 1“ für einen jeweiligen Zeitschlitz decodiert werden, wenn das empfangene Mud-Sirenen-Signal in einem jeweiligen Zeitschlitz im Wesentlichen eine Frequenzkomponente aufweist, die beispielsweise der Differenzfrequenz der Betriebsfrequenzen der zweiten Mud-Sirene und der Betriebsfrequenzen der ersten Mud-Sirene entspricht, also beispielsweise eine Frequenzkomponente von ungefähr 24 Hz aufweist.
• - Das empfangene Mud-Sirenen-Signal kann zu einem vierten Mehr-Bit-Signal decodiert werden, wenn beispielsweise das empfangene Signal keine Frequenzkomponente aufweist, deren Amplitude größer ist als ein vorgegebener Schwellenwert; so kann beispielsweise das empfangene Mud-Sirene-Signal gemäß der oben dargestellten Tabelle 3 zu der Bitsequenz „0 0“ für einen jeweiligen Zeitschlitz decodiert werden, wenn das empfangene Mud-Sirenen-Signal in einem jeweiligen Zeitschlitz im Wesentlichen keine Frequenzkomponente mit ausreichender Amplitude aufweist.

In 1106, the received mud siren signal is decoded to form information having multiple bits depending on the determined at least one frequency of the received mud siren signal. This can be done, for example, in the following way.

• - The received mud siren signal can be decoded to a first multi-bit signal if the determined frequency of the received mud siren signal is in a first frequency range; for example, the received mud siren signal can be decoded to the bit sequence "1 0" for a respective time slot according to Table 3 shown above if the received mud siren signal in a respective time slot essentially has a frequency that corresponds to the operating frequency of the first mud siren, for example has a frequency of approximately 15 Hz.
• - The received mud siren signal can be decoded to a second multi-bit signal if the determined frequency of the received mud siren signal is in a second frequency range; for example, the received mud siren signal can be decoded to the bit sequence "0 1" for a respective time slot according to Table 3 shown above if the received mud siren signal in a respective time slot essentially has a frequency that corresponds to the operating frequency of the second mud siren, for example has a frequency of approximately 39 Hz.
• - The received mud siren signal can be decoded to a third multi-bit signal if the determined frequency of the received mud siren signal is in a third frequency range; for example, the received mud siren signal can be decoded to the bit sequence “1 1” for a respective time slot according to Table 3 shown above if the received mud siren signal in a respective time slot essentially has a frequency component which corresponds, for example, to the difference frequency of the operating frequencies of the second mud siren and the operating frequencies of the first mud siren, that is to say, for example, has a frequency component of approximately 24 Hz.
• - The received mud siren signal may be decoded into a fourth multi-bit signal if, for example, the received signal does not have a frequency component whose amplitude is greater than a predetermined threshold; for example, the received mud siren signal may be decoded into the bit sequence "0 0" for a respective time slot according to Table 3 shown above if the received mud siren signal in a respective time slot substantially does not have a frequency component with sufficient amplitude.

After the multi-bit bit sequence has been decoded for a respective time slot, the information comprising the multi-bit coded in this way is output (block 1108).

The procedure is then repeated for the next time slot, generally for a subsequent time period. It should be noted that the procedure can of course also be carried out for several time slots essentially in parallel or a mud siren signal can be used for a large number of time slots and decoding is only carried out after receiving a “longer” mud siren signal.

13 shows a representation 1300 of the determination of a transfer function and the transfer of the control parameters between the surface and underground. As in 13 As shown, in the "calibration phase" described above, a transmitter 1302 (for example, a mud siren) performs a sweep 1304 in which a large number of different pressure wave signals 1306 of different frequencies but always the same amplitude are generated and detected by the receiver 114 (for example, by means of one or more pressure sensors) (block 1308). In this way, as explained in detail above, the transfer function 1310, which determines the transfer behavior of the transmission channel 1312, for example formed by the drill string 110 and the drilling fluid 112, is determined and an evaluation 1314 is carried out with regard to frequencies suitable for data transmission. This determined frequency information 1316 is transmitted from above ground (for example, from the computer 112) to below ground, for example to the coding device 506.

Alternatively, in various embodiments, it can be provided that the sweep is sent from above ground to underground and the underground computer evaluates the result directly underground and determines the corresponding frequencies itself.

In summary, data is transmitted using pressure waves at specific frequencies. The pressure waves are generated underground using a multi-frequency pulser (transmitter) that has several mud sirens and received again above ground using pressure sensors (receivers). Some frequencies are amplified by reflections and interference in the drill string 110 and other frequencies are attenuated or even completely eliminated. Therefore, the frequency response of the transmission channel (formed by the drilling fluid, among other things) has pass frequency ranges and blocking frequency ranges. An adaptive or frequency-selective technique is used to identify the pass frequency bands. The transmitter performs a so-called sweep (running through all frequencies with a constant amplitude) while the signal is measured at the receiver. The frequencies that arrive at the receiver with the largest amplitudes are the ones that can be best used for data transmission. Usually only a relatively small number of frequencies are considered for data transmission, for example because high frequencies above approximately 20 Hz experience very strong signal attenuation and are therefore generally less suitable for data transmission in deep boreholes. Furthermore, the frequencies used for data transmission should not be integer multiples of each other; the combination of 5 Hz and 20 Hz, for example, should be avoided. The selected frequencies should also differ from each other to such an extent that a simple, clear and error-proof distinction is possible using an evaluation algorithm.

The frequencies considered most suitable for data transmission above ground are initially determined using the mathematical model described in more detail below.

The mathematical model explained in more detail below makes it possible to calculate which speeds (or oscillation rates), in other words which operating frequencies, should be set on the underground mud sirens so that the desired frequencies are induced in the mud channel. These speeds (or oscillation rates) are transmitted via a "downlink" communication channel (transmission of data from the surface to the underground to a mud siren or a coder located in the borehole) to the transmitter unit, which then sets the corresponding speeds or oscillation rates on the mud sirens.

For example, two mud sirens are used in series to transmit 2 bits per time slot. In this context, three frequencies (f1, f2 and f3) should be selected, where: $$\text{<figure-callout id="3" label="e" filenames="DE102015017138B4\_0041.png,DE102015017138B4\_0048.png" state="{{state}}">e</figure-callout>}3=\text{<figure-callout id="2" label="e" filenames="DE102015017138B4\_0038.png,DE102015017138B4\_0039.png" state="{{state}}">e</figure-callout>}2\text{minus <figure-callout id="1" label="f" filenames="DE102015017138B4\_0037.png,DE102015017138B4\_0039.png" state="{{state}}">f</figure-callout>}1.$$

A first mud siren generates the first frequency f1 and a second mud siren generates the second frequency f2; however, all three frequencies (f1, f2 and f3) are used for data transmission, as described above. It should be noted that the frequencies of the mud sirens can be adjusted not only by adjusting the speed, but (alternatively or additionally) also by changing the number of blades of the rotor and stator, in other words by changing or increasing the number of blades. Setting an appropriate number of rotor blades and/or stator blades of the respective Mud Siren(s).

In the following, a parallel connection of several mud sirens, for example two mud sirens, is explained in more detail.

It should be noted that when using a parallel connection of two Mud sirens, only the two operating frequencies of the Mud sirens (f1 and f2) are used for data transmission, which are set on the two Mud sirens (for example on the two Mud sirens 502, 504).

The so-called sweep described above can also be sent in this case from the above-ground unit (for example from the computer 112) to the below-ground unit (for example to the coding unit 506), whereby manual evaluation of the frequencies is no longer provided in this case. The above-ground unit can be automated in various embodiments in that it can receive the sweep signal and automatically evaluate the frequencies and can also inform the transmitter about the most suitable frequencies for data transmission.

14 shows a mud siren arrangement 1400 according to various embodiments. The mud siren arrangement 1400 clearly has several mud sirens, which in these examples are connected in parallel to one another (in other words, they form a parallel connection of several, for example two mud sirens), ie are arranged next to one another, for example within the drilling assembly 102 (with respect to a flow direction of the mud siren arrangement) and not one behind the other, as in the examples described above.

Thus, in various embodiments, the mud siren arrangement 1400 has a stator that has at least a first partial stator 1402 and at least a second partial stator 1404. The mud siren arrangement 1400 also has a first mud siren with a first rotor 1406 and a second mud siren with a second rotor 1408.

The first mud siren has a first open cross-sectional area when the first partial stator 1402 and the first rotor 1406 at least partially overlap. The second mud siren has a second open cross-sectional area when the second partial stator 1404 and the second rotor 1408 at least partially overlap. If only a part of the first open cross-sectional area and/or the second open cross-sectional area is not covered by the respective rotor 1406, 1408, the medium, for example a liquid, for example water, for example the drilling fluid 112, can flow through this opening. By changing the size of the total open cross-sectional area, i.e. the sum of the first open cross-sectional area not covered by the first rotor 1406 at a given time and the second open cross-sectional area not covered by the second rotor 1408 at that time, pressure waves are generated in the medium and a mud siren signal is encoded and transmitted, as already explained in detail above in connection with a series connection of several mud sirens. In various embodiments, the second partial stator 1404 partially surrounds the first partial stator 1402. Furthermore, the second rotor 1408 partially surrounds the first rotor 1406. The second open cross-sectional area partially surrounds the first open cross-sectional area. The first open cross-sectional area is changed by rotating the first rotor 1406 relative to the first partial stator 1402 about a rotation axis. By rotating the second rotor 1408 relative to the second partial stator 1404 about a rotation axis (where a common rotation axis can form the two rotation axes), the second open cross-sectional area is changed. The first rotor 1406 and the second rotor 1408 are rotated, i.e. driven, at different frequencies.

Clearly, the first partial stator 1402 and the first rotor 1406 form a first mud siren and the second partial stator 1404 and the second rotor 1408 form a second mud siren.

In various embodiments, the first partial stator and the second partial stator can be formed in one piece, or alternatively separately from one another. Furthermore, the stators and rotors can each be formed from one or more stator blades and/or rotor blades.

With a suitable selection of the two operating frequencies for the first rotor 1406 and the second rotor 1408, it is also possible to encode information comprising several bits, i.e. to encode a character or symbol comprising several bits for each time slot.

In the mud siren arrangement 1400, two rotors can be operated independently of one another with respect to two partial stators. The mud siren arrangement 1400 according to various embodiments can generate several frequencies, for example two frequencies, simultaneously and independently of one another. The advantage of such a parallel connection of several mud sirens compared to a series connection of several mud sirens as described above is that no interference frequencies are generated. If both mud sirens of the mud siren arrangement 1400 are activated at the same time, in contrast to the series connection, a multi-tone is generated that corresponds exactly to the speeds (ie the frequencies) of the individual rotors 1406, 1408.

15A until 15E shows the mud siren arrangement 1400 according to 14 in different transmission states.

In the 15A until 15E different rotor positions of the first rotor 1406 and the second rotor 1408 are shown. For easier illustration, both the rotor blade of the first rotor 1406 and the stator blade of the first partial stator 1402 are assumed to be semicircles. Both the rotor blade of the second rotor 1408 and the stator blade of the second partial stator 1404 are also assumed to be semicircles. This means that the maximum possible TFA, also referred to below as TFA _max , is also half a circle. When the mud siren arrangement 1400 is put into operation, the rotor position of the two rotors 1406 and 1408 and thus the TFA changes over time. The TFA change over time (in other words, the time course 1602 of the TFA) is shown in 16A shown in a TFA diagram 1600 for the mud siren arrangement 1400 when both mud sirens of the mud siren arrangement 1400 are activated and rotating. If both the stator surfaces (i.e., for example, essentially the surfaces of the stator blades) and the rotor surfaces (i.e., for example, essentially the surfaces of the rotor blades) (referred to as A1 and A2) are the same size, the maximum possible TFA _max of the two mud sirens of the mud siren arrangement 1400 is also the same. With this mud siren arrangement 1400, the resulting signal is no longer dependent on the smallest common TFA, but on the sum of the TFA of both mud sirens of the mud siren arrangement 1400. Thus, only the two targeted frequencies are generated. For example, 16B the resulting frequency signal 1612 to the time course 1602 from 16A in a frequency diagram 1610, whereby in this specific example the two frequencies 15 Hz and 39 Hz are generated by means of the two mud sirens. The frequency signal 1612 also essentially only has the two frequencies 15 Hz (designated with reference numeral 1614) and 39 Hz (designated with reference numeral 1616).

15A shows a pass-through state in which the angle of rotation α ₁ of the first rotor 1406 relative to the first partial stator 1402 and the angle of rotation α ₂ of the second rotor 1408 relative to the second partial stator 1404 are 0° or 360°. In this case, the rotor blades of the rotors 1406, 1408 essentially completely close the entire free cross-sectional area of both mud sirens and thus no medium, for example no liquid, for example no water (and thus possibly no drilling fluid) can flow through the mud siren arrangement 1400. In this case, the TFA is the minimum TFA _min . It should be noted, however, that in practice the fluid flow should never be completely closed because otherwise a so-called strong "water hammer effect" occurs. In a practical implementation of various embodiments, a small gap will therefore usually remain open between the mud sirens.

If the angle of rotation α ₁ of the first rotor 1406 relative to the first partial stator 1402 is 135° and the angle of rotation α ₂ of the second rotor 1408 relative to the second partial stator 1404 is 45°, parts of the rotor blades of the rotors 1406, 1408 cover part of the respective open cross-sectional areas and a TFA ₁ is obtained which lies between TFA _max and TFA _min (see 15B) .

If the angle of rotation α ₁ of the first rotor 1406 relative to the first partial stator 1402 is 180° and the angle of rotation α ₂ of the second rotor 1408 relative to the second partial stator 1404 is 180°, the rotor blades of the rotors 1406, 1408 are essentially completely behind the stator blades of the partial stators 1402, 1404 and expose the entire semicircular cross-section, in other words the entire open cross-sectional area 1502 (cf. 15C ). In this case the TFA is the maximum TFAmax.

If the angle of rotation α ₁ of the first rotor 1406 relative to the first partial stator 1402 is 270° and the angle of rotation α ₂ of the second rotor 1408 relative to the second partial stator 1404 is 90°, parts of the rotor blades of the rotors 1406, 1408 again cover part of the respective open cross-sectional areas and this results in a TFA ₂ that is also between TFA _max and TFA _min (see 15D ). In this specific In the example case, the rotor blade of the first rotor 1406 covers half of the first open cross-sectional area and the rotor blade of the second rotor 1408 covers half of the second open cross-sectional area.

If the angle of rotation α ₁ of the first rotor 1406 relative to the first partial stator 1402 is 90° and the angle of rotation α ₂ of the second rotor 1408 relative to the second partial stator 1404 is 315°, parts of the rotor blades of the rotors 1406, 1408 again cover part of the respective open cross-sectional areas and a TFA ₃ is obtained which is also between TFA _max and TFA _min (see 15D ). In this specific example, the rotor blade of the first rotor 1406 again covers half of the first open cross-sectional area (although compared to the state from 15D the other half) and the rotor blade of the second rotor 1408 covers approximately two-thirds of the second open cross-sectional area.

17 shows a mud siren arrangement 1700 according to various embodiments with two mud sirens in parallel circuits. 18 shows a cross-sectional view of the mud siren arrangement according to 17 .

The mud siren arrangement 1700 is arranged in a drill rod 1702 and has a stationary stator 1704, an inner semicircular (first) rotor 1706 and an outer semicircular (second) rotor 1708 partially surrounding it. The mud siren arrangement 1700 also has a first drive 1710 for the first rotor 1706 and a second drive 1712 for the second rotor 1708. It should be noted that the first drive 1710 and the second drive 1712 can also be implemented as a common combined drive. The two rotors 1706, 1708 can be connected to one another and to the drives 1710, 1712 by means of a shaft-hollow shaft combination 1714, for example mechanically coupled.

A part of the stator 1704, the first rotor 1706, the first drive 1710 and the drive shaft for driving the first rotor 1706 by means of the first drive 1710, which is part of the shaft-hollow shaft combination 1714, forms a first mud siren in the mud siren arrangement 1700.

A portion of the stator 1704, the second rotor 1708, the second drive 1712 and the drive shaft for driving the second rotor 1708 by means of the second drive 1712, which is part of the shaft-hollow shaft combination 1714, forms a second mud siren in the mud siren arrangement 1700.

The operation of the mud siren arrangement 1700 for encoding information comprising a plurality of bits at a respective encoding time, for example at a respective time slot, is substantially the same as the operation of the mud siren arrangement 1400 according to 14 , which is why we will repeat the description of the coding and transmission of multiple bit data. In this regard, we refer to the above description of, for example, the 14 until 16B referred to.

In the 19 until 25 various methods are shown for determining a signal spectrum which describes the transfer function, for example the transfer function 1200, from which the induced frequency components result, from which the respective operating frequencies for the mud sirens of a series connection in a mud siren arrangement can be determined or selected.

• - TFA₁(t) bezeichnet die so genannte Total Flow Area-Funktion über die Zeit einer ersten Mud-Sirene von zwei oder mehr als zwei in Reihe oder parallel angeordneten Mud-Sirenen einer Mud-Sirenen-Anordnung;
• - n bezeichnet einen Berechnungsschritt-Index und ist eine ganze natürliche Zahl, die von 0 bis (B-1) läuft (n = 0, 1, 2, 3, ..., (B-1)) (er wird nur verwendet, wenn der jeweilige Rotor mehrere Rotorblätter aufweist, wobei B die Anzahl der Rotorblätter angibt);
• - B₁ bezeichnet die Anzahl der Rotorblätter des Rotors der ersten Mud-Sirene;
• - α₁(t) bezeichnet eine Funktion der Veränderung des Drehwinkel α₁ des Rotors relativ zu dem Stator der ersten Mud-Sirene;
• - r₁ bezeichnet den Radius der Öffnungsfläche der ersten Mud-Sirene;
• - TFA₂(t) bezeichnet die so genannte Total Flow Area-Funktion über die Zeit einer zweiten Mud-Sirene von zwei oder mehr als zwei in Reihe oder parallel angeordneten Mud-Sirenen einer Mud-Sirenen-Anordnung;
• - B₂ bezeichnet die Anzahl der Rotorblätter des Rotors der zweiten Mud-Sirene;
• - α₂(t) bezeichnet eine Funktion der Veränderung des Drehwinkel α₂ des Rotors relativ zu dem Stator der zweiten Mud-Sirene; und
• - r₂ bezeichnet bei einer Reihenschaltung mehrerer Mud-Sirenen den Radius der Öffnungsfläche der zweiten Mud-Sirene, und bei einer Parallelschaltung mehrerer Mud-Sirenen den Radius ausgehend von der Rotationsachse der zweiten Mud-Sirene bis zum Außenumfang der zweiten Mud-Sirene (der „Radius“ der Öffnungsfläche der zweiten Mud-Sirene ergibt sich in dem Fall einer Parallelschaltung zu (r₂ - r₁)).

The following nomenclature is used in the respective calculation rules:

• - TFA ₁ (t) means the so-called total flow area function over time of a first mud siren of two or more than two mud sirens arranged in series or parallel in a mud siren arrangement;
• - n denotes a calculation step index and is an integer running from 0 to (B-1) (n = 0, 1, 2, 3, ..., (B-1)) (it is only used if the respective rotor has several rotor blades, where B indicates the number of rotor blades);
• - B ₁ denotes the number of blades of the rotor of the first Mud Siren;
• - α ₁ (t) denotes a function of the change in the angle of rotation α ₁ of the rotor relative to the stator of the first mud siren;
• - r ₁ denotes the radius of the opening area of the first mud siren;
• - TFA ₂ (t) means the so-called total flow area function over time of a second mud siren of two or more than two mud sirens arranged in series or parallel in a mud siren arrangement;
• - B ₂ denotes the number of blades of the rotor of the second Mud Siren;
• - α ₂ (t) denotes a function of the change in the angle of rotation α ₂ of the rotor relative to the stator of the second mud siren; and
• - r ₂ denotes the radius of the opening area of the second mud siren in the case of a series connection of several mud sirens, and in the case of a parallel connection of several mud sirens, the radius starting from the axis of rotation of the second mud siren to the outer circumference of the second mud siren (the "radius" of the opening area of the second mud siren in the case of a parallel connection is (r ₂ - r ₁ )).

19 shows a flow chart in which a method 1900 for determining a signal spectrum is shown according to various comparative examples. The method 1900 can be used for a series connection 1902 of two mud sirens (a first mud siren 1904 and a second mud siren 1906) in a mud siren arrangement, wherein the rotor of a respective mud siren can have any number of rotor blades (B ₁ and B ₂ ) and wherein the stator of a respective mud siren can also have any number of stator blades (equal to B ₁ and B ₂ ).

In 1908, TFA ₁ (t) is determined for a respective value of the running index n. This is done by checking in 1910 for the respective value of n whether the following rule is fulfilled for the temporal course of the angle of rotation α ₁ (t): $$2\text{n}\frac{360°}{2{\text{<figure-callout id="1" label="B" filenames="DE102015017138B4\_0037.png,DE102015017138B4\_0039.png" state="{{state}}">B</figure-callout>}}_1}<{\mathrm{\alpha }}_1\left(\text{t}\right)\le \left(2\text{n}+1\right)\frac{360°}{2{\text{<figure-callout id="1" label="B" filenames="DE102015017138B4\_0037.png,DE102015017138B4\_0039.png" state="{{state}}">B</figure-callout>}}_1}.$$

If this is the case (block 1912), then for this value of n the TFA ₁ (t) results according to the following rule (block 1914): $${\text{TFA}}_1\left(\text{t}\right)={\text{B}}_1\left(\mathrm{\pi }{\text{<figure-callout id="1" label="r" filenames="DE102015017138B4\_0037.png,DE102015017138B4\_0039.png" state="{{state}}">r</figure-callout>}}_1^2\frac{{\mathrm{\alpha }}_1\left(\text{t}\right)}{360°}\right).$$

However, if this is not the case (block 1918), then for this value of n the TFA ₁ (t) results according to the following rule (block 1920): $${\text{TFA}}_1\left(\text{t}\right)=\left(\frac{1}{2}\mathrm{<figure-callout\; id="1"\; label="\pi \; r"\; filenames="DE102015017138B4\_0037.png,DE102015017138B4\_0039.png"\; state="\{\{state\}\}">\pi </figure-callout>}{\text{r}}_{}^{}{}_1^2\right)-{\text{B}}_1\left(\mathrm{\pi }{\text{<figure-callout id="1" label="r" filenames="DE102015017138B4\_0037.png,DE102015017138B4\_0039.png" state="{{state}}">r</figure-callout>}}_1^2\frac{{\mathrm{\alpha }}_1\left(\text{t}\right)-\left(\left(2\text{n}+1\right)\frac{360°}{2{\text{B}}_1}\right)}{360°}\right).$$

Thus, TFA ₁ (t) is determined and thus known for all angles of rotation (block 1916).

Furthermore, in 1922 TFA ₂ (t) is determined for the value of the index n. This is done by checking in 1924 for the value of n whether the following rule is fulfilled for the temporal course of the angle of rotation α ₂ (t): $$2\text{n}\frac{360°}{2{\text{<figure-callout id="2" label="B" filenames="DE102015017138B4\_0038.png,DE102015017138B4\_0039.png" state="{{state}}">B</figure-callout>}}_2}<{\mathrm{\alpha }}_2\left(\text{t}\right)\le \left(2\text{n}+1\right)\frac{360°}{2{\text{<figure-callout id="2" label="B" filenames="DE102015017138B4\_0038.png,DE102015017138B4\_0039.png" state="{{state}}">B</figure-callout>}}_2}.$$

If this is the case (block 1926), then for this value of n the TFA ₂ (t) results according to the following rule (block 1928): $${\text{TFA}}_2\left(\text{t}\right)={\text{B}}_2\left(\mathrm{\pi }{\text{<figure-callout id="2" label="r" filenames="DE102015017138B4\_0038.png,DE102015017138B4\_0039.png" state="{{state}}">r</figure-callout>}}_2^2\frac{{\mathrm{\alpha }}_2\left(\text{t}\right)}{360°}\right).$$

However, if this is not the case (block 1930), then for this value of n the TFA ₂ (t) results according to the following rule (block 1932): $${\text{TFA}}_2\left(\text{t}\right)=\left(\frac{1}{2}\mathrm{<figure-callout\; id="2"\; label="\pi \; r"\; filenames="DE102015017138B4\_0038.png,DE102015017138B4\_0039.png"\; state="\{\{state\}\}">\pi </figure-callout>}{\text{r}}_{}^{}{}_2^2\right)-{\text{B}}_2\left(\mathrm{\pi }{\text{<figure-callout id="2" label="r" filenames="DE102015017138B4\_0038.png,DE102015017138B4\_0039.png" state="{{state}}">r</figure-callout>}}_2^2\frac{{\mathrm{\alpha }}_2\left(\text{t}\right)-\left(\left(2\text{n}+1\right)\frac{360°}{2{\text{B}}_2}\right)}{360°}\right).$$

Thus, TFA ₂ (t) is determined and thus known for all angles of rotation (block 1934).

Now it is checked whether TFA ₁ (t) is smaller than TFA ₂ (t) (block 1936).

If this is the case (Block 1938), the following allocation applies (Block 1940): $$\text{TFA}\left(\text{t}\right)={\text{TFA}}_1\left(\text{t}\right).$$

However, if this is not the case (Block 1942), the following allocation applies (Block 1944): $$\text{TFA}\left(\text{t}\right)={\text{TFA}}_2\left(\text{t}\right).$$

Thus, TFA(t) is known (block 1946).

A spectral transformation, such as a Fourier transformation, such as a fast Fourier transformation, can be applied to the now known function TFA(t) in the time domain in 1948, resulting in a signal spectrum (block 1950). From this, the induced frequency components and the resulting drive frequencies for the two mud sirens 1904, 1906 can be determined, as described above.

20 shows a flow chart in which a method 2000 for determining a signal spectrum is shown according to various comparative examples. The method 2000 can be used for a series connection 2002 of two mud sirens (a first mud siren 2004 and a second mud siren 2006) in a mud siren arrangement, wherein the rotor of a respective mud siren has exactly one rotor blade (without restricting the generality, a semicircular rotor blade is assumed) and wherein the stator of a respective mud siren also has exactly one stator blade (without restricting the generality, a semicircular stator blade is assumed). Furthermore, without restricting the generality, the following is assumed: r ₁ = r ₂ = r.

In 2008, TFA ₁ (t) is determined. This is done by checking in 2010 whether the following rule is fulfilled for the temporal progression of the angle of rotation α ₁ (t): $${\mathrm{\alpha }}_1\left(\text{t}\right)\le 180°.$$

If this is the case (Block 2012), then TFA ₁ (t) is calculated according to the following rule (Block 2014): $${\text{TFA}}_1\left(\text{t}\right)=\mathrm{<figure-callout\; id="2"\; label="\pi \; r"\; filenames="DE102015017138B4\_0038.png,DE102015017138B4\_0039.png"\; state="\{\{state\}\}">\pi </figure-callout>}{\text{r}}^{}{}^2\frac{{\mathrm{\alpha }}_1\left(\text{t}\right)}{360°}.$$

However, if this is not the case (Block 2016), then TFA ₁ (t) results according to the following rule (Block 2018): $${\text{TFA}}_1\left(\text{t}\right)=\left(\frac{1}{2}\mathrm{\pi }{\text{r}}^2\right)-\left(\mathrm{<figure-callout\; id="2"\; label="\pi \; r"\; filenames="DE102015017138B4\_0038.png,DE102015017138B4\_0039.png"\; state="\{\{state\}\}">\pi </figure-callout>}{\text{r}}^{}{}^2\frac{{\mathrm{\alpha }}_1\left(\text{t}\right)-180°}{360°}\right)$$

Thus, TFA ₁ (t) is determined and thus known (Block 2020).

Furthermore, TFA ₂ (t) will be determined in 2022. This is done by checking in 2024 whether the following rule is met for the temporal progression of the angle of rotation α ₂ (t): $${\mathrm{\alpha }}_2\left(\text{t}\right)\le 180°.$$

If this is the case (block 2026), then TFA ₂ (t) results according to the following rule (block 2028): $${\text{TFA}}_2\left(\text{t}\right)=\mathrm{<figure-callout\; id="2"\; label="\pi \; r"\; filenames="DE102015017138B4\_0038.png,DE102015017138B4\_0039.png"\; state="\{\{state\}\}">\pi </figure-callout>}{\text{r}}^{}{}^2\frac{{\mathrm{\alpha }}_2\left(\text{t}\right)}{360°}.$$

However, if this is not the case (block 2030), then TFA ₂ (t) results according to the following rule (block 2032): $${\text{TFA}}_2\left(\text{t}\right)=\left(\frac{1}{2}\mathrm{\pi }{\text{r}}^2\right)-\left(\mathrm{<figure-callout\; id="2"\; label="\pi \; r"\; filenames="DE102015017138B4\_0038.png,DE102015017138B4\_0039.png"\; state="\{\{state\}\}">\pi </figure-callout>}{\text{r}}^{}{}^2\frac{{\mathrm{\alpha }}_2\left(\text{t}\right)-180°}{360°}\right).$$

Thus, TFA ₂ (t) is determined and thus known (block 2034).

Now it is checked whether TFA ₁ (t) is smaller than TFA ₂ (t) (block 2036).

If this is the case (block 2038), the following assignment applies (block 2040): $$\text{TFA}\left(\text{t}\right)={\text{TFA}}_1\left(\text{t}\right).$$

However, if this is not the case (block 2042), the following assignment applies (block 2044): $$\text{TFA}\left(\text{t}\right)={\text{TFA}}_2\left(\text{t}\right).$$

Thus, TFA(t) is known.

A spectral transformation, such as a Fourier transformation, such as a fast Fourier transformation, can be applied to the now known function TFA(t) in the time domain in 2046, resulting in a signal spectrum (block 2048). From this, the induced frequency components and the resulting drive frequencies for the two mud sirens 2004, 2006 can be determined, as described above.

21 shows a flow chart in which a method 2100 for determining a signal spectrum is shown according to various comparative examples. The method 2100 can be used for a series connection 2102 of any number N of mud sirens (a first mud siren 2104, a second mud siren 2106, a third mud siren 2108, ..., an i-th mud siren 2110, and an N-th mud siren 2112) in a mud siren arrangement, wherein the rotor of a respective mud siren can have any number of rotor blades and wherein the stator of a respective mud siren can also have any number of stator blades.

For each of the mud sirens, the respective TFA _i (t) is determined, namely TFA ₁ (t) for the first mud siren 2104 (block 2114), TFA ₂ (t) for the second mud siren 2106 (block 2116), TFA ₃ (t) for the third mud siren 2108 (block 2118), ..., TFA _i (t) for the i-th mud siren 2110 (block 2120), and TFA _N (t) for the N-th mud siren 2112 (block 2122).

This is done, for example, using equations (2) to (4), as in relation to 19 described (Block 2124).

Thus, all TFA _i (t) are determined and thus known for all switched sirens at each angle of rotation (blocks 2126, 2128, 2130, 2132, and 2134).

Subsequently, in 2136, all calculated values of TFA _i (t) (i.e. all calculated values from TFA ₁ (t) to TFA _N (t)) are compared. The smallest TFA _i (t) is assigned as TFA(t). TFA(t) is thus known (block 2138).

A spectral transformation, for example a Fourier transformation, for example a fast Fourier transformation, can be applied to the now known function TFA(t) in the time domain in 2140, resulting in a signal spectrum (block 2142). From this, the induced frequency components and the resulting drive frequencies for the N mud sirens 2104, 2106, 2108, ..., 2110, 2112 can be determined, as described above.

22 shows a flow chart in which a method 2200 for determining a signal spectrum is shown according to various comparative examples. The method 2200 can be used for a parallel connection 2202 of two mud sirens (a first mud siren 2204 and a second mud siren 2206) in a mud siren arrangement, wherein the rotor of a respective mud siren can have any number of rotor blades and wherein the stator of a respective mud siren can also have any number of stator blades.

In 2208, TFA ₁ (t) is determined for a respective value of the running index n. This is done by checking in 2210 for the respective value of n whether the following rule is fulfilled for the temporal course of the angle of rotation α ₁ (t): $$2\text{n}\frac{360°}{2{\text{<figure-callout id="1" label="B" filenames="DE102015017138B4\_0037.png,DE102015017138B4\_0039.png" state="{{state}}">B</figure-callout>}}_1}<{\mathrm{\alpha }}_2\left(\text{t}\right)\le \left(2\text{n}+1\right)\frac{360°}{2{\text{<figure-callout id="1" label="B" filenames="DE102015017138B4\_0037.png,DE102015017138B4\_0039.png" state="{{state}}">B</figure-callout>}}_1}.$$

If this is the case (block 2212), then for this value of n the TFA ₁ (t) results according to the following rule (block 2214): $${\text{TFA}}_1\left(\text{t}\right)={\text{B}}_1\left(\mathrm{\pi }{\text{<figure-callout id="1" label="r" filenames="DE102015017138B4\_0037.png,DE102015017138B4\_0039.png" state="{{state}}">r</figure-callout>}}_1^2\frac{{\mathrm{\alpha }}_1\left(\text{t}\right)}{360°}\right).$$

However, if this is not the case (block 2218), then for this value of n the TFA ₁ (t) results according to the following rule (block 2220): $${\text{TFA}}_1\left(\text{t}\right)=\left(\frac{1}{2}\mathrm{<figure-callout\; id="1"\; label="\pi \; r"\; filenames="DE102015017138B4\_0037.png,DE102015017138B4\_0039.png"\; state="\{\{state\}\}">\pi </figure-callout>}{\text{r}}_{}^{}{}_1^2\right)-{\text{B}}_1\left(\mathrm{\pi }{\text{<figure-callout id="1" label="r" filenames="DE102015017138B4\_0037.png,DE102015017138B4\_0039.png" state="{{state}}">r</figure-callout>}}_1^2\frac{{\mathrm{\alpha }}_1\left(\text{t}\right)-\left(\left(2\text{n}+1\right)\frac{360°}{2{\text{B}}_1}\right)}{360°}\right).$$

Thus, TFA ₁ (t) is determined and thus known for all angles of rotation (block 2216).

Furthermore, in 2222 TFA ₂ (t) is determined for a respective value of the running index n. This is done by checking in 2224 for the respective value of n whether the following rule is fulfilled for the temporal course of the angle of rotation α ₂ (t): $$2\text{n}\frac{360°}{2{\text{<figure-callout id="2" label="B" filenames="DE102015017138B4\_0038.png,DE102015017138B4\_0039.png" state="{{state}}">B</figure-callout>}}_2}<{\mathrm{\alpha }}_2\left(\text{t}\right)\le \left(2\text{n}+1\right)\frac{360°}{2{\text{<figure-callout id="2" label="B" filenames="DE102015017138B4\_0038.png,DE102015017138B4\_0039.png" state="{{state}}">B</figure-callout>}}_2}.$$

If this is the case (block 2226), then for this value of n the TFA ₂ (t) results according to the following rule (block 2228): $${\text{TFA}}_2\left(\text{t}\right)={\text{B}}_2\left(\mathrm{\pi }\left({\text{<figure-callout id="2" label="r" filenames="DE102015017138B4\_0038.png,DE102015017138B4\_0039.png" state="{{state}}">r</figure-callout>}}_2^2-{\text{<figure-callout id="1" label="r" filenames="DE102015017138B4\_0037.png,DE102015017138B4\_0039.png" state="{{state}}">r</figure-callout>}}_1^2\right)\frac{{\mathrm{\alpha }}_2\left(\text{t}\right)}{360°}\right).$$

However, if this is not the case (block 2230), then for this value of n the TFA ₂ (t) results according to the following rule (block 2232): $${\text{TFA}}_2\left(\text{t}\right)=\left(\mathrm{\pi }\left({\text{<figure-callout id="2" label="r" filenames="DE102015017138B4\_0038.png,DE102015017138B4\_0039.png" state="{{state}}">r</figure-callout>}}_2^2{\text{-<figure-callout id="1" label="r" filenames="DE102015017138B4\_0037.png,DE102015017138B4\_0039.png" state="{{state}}">r</figure-callout>}}_1^2\right)\right)\left(\frac{1}{2}-\left({\text{<figure-callout id="2" label="B" filenames="DE102015017138B4\_0038.png,DE102015017138B4\_0039.png" state="{{state}}">B</figure-callout>}}_2\frac{{\mathrm{\alpha }}_2\left(\text{t}\right)-\left(\left(2\text{n}+1\right)\frac{360°}{2{\text{B}}_2}\right)}{360°}\right)\right).$$

Thus, TFA ₂ (t) is determined and thus known for all angles of rotation (block 2234).

Now TFA(t) is determined according to the following rule (block 2236): $$\text{TFA}\left(\text{t}\right)={\text{TFA}}_1\left(\text{t}\right)+{\text{TFA}}_2\left(\text{t}\right)$$

A spectral transformation, for example a Fourier transformation, for example a fast Fourier transformation, can be applied to the now determined function TFA(t) in the time domain in 2238, resulting in a signal spectrum (block 2240). From this, the induced frequency components and the resulting drive frequencies for the two mud sirens 2204, 2206 can be determined, as described above.

23 shows a flow chart in which a method 2300 for determining a signal spectrum is shown according to various comparative examples. The method 2300 can be used for a parallel connection 2302 of two mud sirens (a first mud siren 2304 and a second mud siren 2306) in a mud siren arrangement, wherein the rotor of a respective mud siren has exactly one rotor blade and wherein the stator of a respective mud siren also has exactly one stator blade.

In 2308, TFA ₁ (t) is determined. This is done by checking in 2310 whether the following rule is fulfilled for the temporal progression of the angle of rotation α ₁ (t): $${\mathrm{\alpha }}_1\left(\text{t}\right)\le 180°.$$

If this is the case (block 2312), then TFA ₁ (t) results according to the following rule (block 2314): $${\text{TFA}}_1\left(\text{t}\right)=\mathrm{\pi }*{\text{<figure-callout id="1" label="r" filenames="DE102015017138B4\_0037.png,DE102015017138B4\_0039.png" state="{{state}}">r</figure-callout>}}_1^2*\frac{{\mathrm{\alpha }}_1\left(\text{t}\right)}{360°}.$$

However, if this is not the case (block 2316), then TFA ₁ (t) results according to the following rule (block 2318): $${\text{TFA}}_1\left(\text{t}\right)=\left(\frac{1}{2}\mathrm{<figure-callout\; id="1"\; label="\pi \; r"\; filenames="DE102015017138B4\_0037.png,DE102015017138B4\_0039.png"\; state="\{\{state\}\}">\pi </figure-callout>}{\text{r}}_{}^{}{}_1^2\right)-\left(\mathrm{<figure-callout\; id="1"\; label="\pi \; r"\; filenames="DE102015017138B4\_0037.png,DE102015017138B4\_0039.png"\; state="\{\{state\}\}">\pi </figure-callout>}{\text{r}}_{}^{}{}_1^2\frac{{\mathrm{\alpha }}_1\left(\text{t}\right)-180°}{360°}\right).$$

Thus, TFA ₁ (t) is determined and thus known for all angles of rotation (block 2320).

Furthermore, TFA ₂ (t) is determined in 2322. This is done by checking in 2324 whether the following rule is fulfilled for the temporal progression of the angle of rotation α ₂ (t): $${\mathrm{\alpha }}_2\left(\text{t}\right)\le 180°.$$

If this is the case (block 2326), then TFA ₂ (t) results according to the following rule (block 2328): $${\text{TFA}}_2\left(\text{t}\right)=\mathrm{\pi }\left({\text{<figure-callout id="2" label="r" filenames="DE102015017138B4\_0038.png,DE102015017138B4\_0039.png" state="{{state}}">r</figure-callout>}}_2^2-{\text{<figure-callout id="1" label="r" filenames="DE102015017138B4\_0037.png,DE102015017138B4\_0039.png" state="{{state}}">r</figure-callout>}}_1^2\right)\frac{{\mathrm{\alpha }}_2\left(\text{t}\right)}{360°}.$$

However, if this is not the case (block 2330), then TFA ₂ (t) results according to the following rule (block 2332): $${\text{TFA}}_2\left(\text{t}\right)=\mathrm{\pi }*\left({\text{<figure-callout id="2" label="r" filenames="DE102015017138B4\_0038.png,DE102015017138B4\_0039.png" state="{{state}}">r</figure-callout>}}_2^2-{\text{<figure-callout id="1" label="r" filenames="DE102015017138B4\_0037.png,DE102015017138B4\_0039.png" state="{{state}}">r</figure-callout>}}_1^2\right)*\left(\frac{1}{2}-\frac{{\mathrm{\alpha }}_2\left(\text{t}\right)-180°}{360°}\right).$$

Thus, TFA ₂ (t) is determined and thus known for all angles of rotation (block 2334).

Now TFA(t) is determined according to the following rule (block 2336): $$\text{TFA}\left(\text{t}\right)={\text{TFA}}_1\left(\text{t}\right)+{\text{TFA}}_2\left(\text{t}\right)$$

A spectral transformation, for example a Fourier transformation, for example a fast Fourier transformation, can be applied to the now known function TFA(t) in the time domain in 2338, resulting in a signal spectrum (block 2340). From this, the induced frequency components and the resulting drive frequencies for the two mud sirens 2004, 2006 can be determined, as described above.

24 shows a flow chart in which a method 2400 for determining a signal spectrum is shown according to various comparative examples. The method 2400 can be used for a parallel connection 2402 of any number N of mud sirens (a first mud siren 2404, a second mud siren 2406, a third mud siren 2408, ..., an i-th mud siren 2410, and an N-th mud siren 2412) in a mud siren arrangement, wherein the rotor of a respective mud siren can have any number of rotor blades and wherein the stator of a respective mud siren can also have any number of stator blades.

For each of the mud sirens, the respective TFA _i (t) is determined, namely TFA ₁ (t) for the first mud siren 2404 (block 2414), TFA ₂ (t) for the second mud siren 2406 (block 2416), TFA ₃ (t) for the third mud siren 2408 (block 2418), ..., TFA _i (t) for the i-th mud siren 2410 (block 2420), and TFA _N (t) for the N-th mud siren 2412 (block 2422).

This is done, for example, using equations (18) to (23), as in relation to 22 described (Block 2424).

Thus, all TFA _i (t) are determined and thus known for all rotation angles (blocks 2426, 2428, 2430, 2432, and 2434).

Now TFA(t) is determined according to the following rule (block 2436): $$\text{TFA}\left(\text{t}\right)={\text{TFA}}_1\left(\text{t}\right)+{\text{TFA}}_2\left(\text{t}\right)+{\text{TFA}}_3\left(\text{t}\right)+\dots +{\text{TFA}}_{\text{N}}\left(\text{t}\right)$$

A spectral transformation, for example a Fourier transformation, for example a fast Fourier transformation, can be applied to the now known function TFA(t) (block 2438) in the time domain in 2440, resulting in a signal spectrum (block 2442). From this, the induced frequency components and the resulting drive frequencies for the N mud sirens 2404, 2406, 2408, ..., 2410, 2412 can be determined, as described above.

25 shows a flow chart illustrating a method 2500 for determining a signal spectrum according to various comparative examples. The method 2500 can be used for a combination 2502 of a series connection 2504 of any number N of mud sirens 2506 (a first mud siren 1.MS, a second mud siren 2.MS, an i-th mud siren i.MS, and an N-th mud siren N.MS) with a parallel connection 2508 of any number N of mud sirens 2510 (a first mud siren 1.MS, a second mud siren 2.MS, an i-th mud siren i.MS, and an N-th mud siren N.MS) in a mud siren arrangement, wherein the rotor of a respective mud siren can have any number of rotor blades and wherein the stator of a respective mud siren can also have any number of stator blades. The number of mud sirens provided in the series circuit 2504 and in the parallel circuit 2508 can be equal or different from each other.

First, for each of the mud sirens in series connection 2504, the respective TFA _iRS (t) is determined, namely TFA _1RS (t) for the first mud siren, TFA _2RS (t) for the second mud siren, TFA _3RS (t) for the third mud siren, ..., TFA _iRS (t) for the i-th mud siren, and TFA _NRS (t) for the N-th mud siren.

This is done, for example, using equations (2) to (4), as in relation to 19 described (Block 2512).

Thus, all TFA _i (t) are determined and thus known for all switched sirens at each angle of rotation.

A comparison of all calculated values of the TFA _iRS (t) (i.e. all calculated values from TFA _1RS (t) to TFA _NRS (t)) is then carried out in 2514. The smallest TFA _iRS (t) is assigned as TFA _RS (t). TFA _RS (t) is thus known.

Furthermore, the respective TFA _iPS (t) is determined for each of the mud sirens, namely TFA _1PS (t) for the first mud siren, TFA _2PS (t) for the second mud siren, TFA _3PS (t) for the third mud siren, ..., TFA _iPS (t) for the i-th mud siren, and TFA _NPS (t) for the N-th mud siren.

This is done, for example, using equations (18) to (23), as in relation to 22 described (Block 2516).

This means that all TFA _iPS (t) are determined and thus known for all switched sirens at every angle of rotation.

Now TFA _PS (t) is determined according to the following rule (Block 2518): $${\text{TFA}}_{\text{PS}}\left(\text{t}\right)={\text{<figure-callout id="1" label="TFA" filenames="DE102015017138B4\_0037.png,DE102015017138B4\_0039.png" state="{{state}}">TFA</figure-callout>}}_{1\text{PS}}\left(\text{t}\right)+{\text{<figure-callout id="2" label="TFA" filenames="DE102015017138B4\_0038.png,DE102015017138B4\_0039.png" state="{{state}}">TFA</figure-callout>}}_{2\text{PS}}\left(\text{t}\right)+{\text{<figure-callout id="3" label="TFA" filenames="DE102015017138B4\_0041.png,DE102015017138B4\_0048.png" state="{{state}}">TFA</figure-callout>}}_{3\text{PS}}\left(\text{t}\right)+\dots +{\text{TFA}}_{\text{NPS}}\left(\text{t}\right)$$

Now it is checked whether the following requirement is met: $${\text{TFA}}_{\text{RS}}\left(\text{t}\right)<{\text{TFA}}_{\text{PS}}\left(\text{t}\right).$$

If rule (34) is fulfilled (block 2522), then TFA _RS (t) is used as TFA(t) in the following (block 2524).

However, if rule (34) is not fulfilled (block 2526), then TFA _PS (t) is used as TFA(t) in the following (block 2528).

A spectral transformation, such as a Fourier transformation, such as a fast Fourier transformation, can be applied to the now determined function TFA(t) in the time domain in 2530, resulting in a signal spectrum (block 2532). From this, the induced frequency components and the resulting drive frequencies for the N+N mud sirens can be determined, as described above.

It should be noted that in a mud siren arrangement according to various embodiments, any number of mud sirens connected in series and/or in parallel can be provided and can be operated accordingly at different frequencies to achieve a correspondingly high data rate.

It should also be noted that the mud siren arrangements according to various embodiments can be used in all deep boreholes, from shallow to deep boreholes. An increased data rate between the underground sensors and the surface facilities significantly facilitates drilling operations and the targeted control of the borehole to a desired target area.

• Vergleichsbeispiel 1 Mud-Sirenen-Anordnung, aufweisend:
  • • eine Bohrgarnitur;
  • • eine in der Bohrgarnitur angeordnete erste Mud-Sirene;
  • • mindestens eine in der Bohrgarnitur angeordnete weitere Mud-Sirene;
  • • mindestens eine Codiereinrichtung, die mit der ersten Mud-Sirene und der weiteren Mud-Sirene gekoppelt ist; und
  • • wobei die erste Mud-Sirene und die mindestens eine weitere Mud-Sirene derart angeordnet sind und die Codiereinrichtung die erste Mud-Sirene und die weitere Mud-Sirene derart ansteuert, dass zu einem Codierzeitpunkt mittels der ersten Mud-Sirene und der weiteren Mud-Sirene eine mehrere Bits aufweisende Information codiert und übertragen wird.
• Vergleichsbeispiel 2. Mud-Sirenen-Anordnung gemäß Beispiel 1, wobei die erste Mud-Sirene und die mindestens eine weitere Mud-Sirene hintereinander in der Bohrgarnitur angeordnet sind.
• Vergleichsbeispiel 3. Mud-Sirenen-Anordnung gemäß Beispiel 1, ferner aufweisend:
  • wobei die erste Mud-Sirene und die mindestens eine weitere Mud-Sirene nebeneinander in der Bohrgarnitur angeordnet sind.
• Vergleichsbeispiel 4. Mud-Sirenen-Anordnung gemäß einem der Beispiele 1 bis 3,
  • wobei die Codiereinrichtung die erste Mud-Sirene und die mindestens eine weitere Mud-Sirene derart ansteuert, dass die erste Mud-Sirene und die mindestens eine weitere Mud-Sirene mit voneinander unterschiedlichen Frequenzen zum Codieren der mehrere Bits aufweisenden Information angetrieben werden.
• Vergleichsbeispiel 5. Mud-Sirenen-Anordnung gemäß einem der Beispiele 1 bis 4,
  • wobei der Codierzeitpunkt ein Beginn eines Zeitschlitzes ist. Vergleichsbeispiel 6. Mud-Sirenen-Anordnung gemäß Beispiel 4 oder 5,
  • wobei die Frequenzen kleiner oder gleich ungefähr 50 Hz sind. Vergleichsbeispiel 7. Verfahren zum Codieren und Übertragen von einer mehrere Bits aufweisenden Information, wobei das Verfahren aufweist:
    • • Betreiben einer in einer Bohrgarnitur angeordneten ersten Mud-Sirene mit einer ersten Frequenz;
    • • Betreiben mindestens einer in der Bohrgarnitur angeordneten mindestens einer weiteren Mud-Sirene mit einer weiteren Frequenz, die von der ersten Frequenz unterschiedlich ist; und
    • • Ansteuern der ersten Mud-Sirene und der mindestens einen weiteren Mud-Sirene derart, dass zu einem Codierzeitpunkt mittels der ersten Mud-Sirene und der mindestens einen weiteren Mud-Sirene die mehrere Bits aufweisende Information codiert und übertragen wird.
• Vergleichsbeispiel 8. Verfahren gemäß Beispiel 7, wobei ein im Wesentlichen inkompressibles Medium zum Übertragen der Information zur Erdoberfläche durch die erste Mud-Sirene und die mindestens eine weitere Mud-Sirene gespült wird.
• Vergleichsbeispiel 9. Verfahren gemäß Beispiel 7 oder 8, wobei die erste Mud-Sirene und die mindestens eine weitere Mud-Sirene hintereinander in der Bohrgarnitur angeordnet sind.
• Vergleichsbeispiel 10. Verfahren gemäß Beispiel 7 oder 8, wobei die erste Mud-Sirene und die mindestens eine weitere Mud-Sirene nebeneinander in der Bohrgarnitur angeordnet sind.
• Vergleichsbeispiel 11. Verfahren gemäß einem der Beispiele 7 bis 10, wobei die erste Mud-Sirene und die mindestens eine weitere Mud-Sirene mit voneinander unterschiedlichen Frequenzen zum Codieren der mehrere Bits aufweisenden Information angetrieben werden.
• Vergleichsbeispiel 12. Verfahren gemäß einem der Beispiele 7 bis 11, wobei der Codierzeitpunkt ein Beginn eines Zeitschlitzes ist.
• Vergleichsbeispiel 13. Verfahren gemäß Beispiel 11 oder 12, wobei die Frequenzen kleiner oder gleich ungefähr 50 Hz sind.
• Vergleichsbeispiel 14. Mud-Sirenen-Decodieranordnung, aufweisend:
  • einen Empfänger, eingerichtet zum Empfangen eines mittels einer Bohrspülung übertragenen Mud-Sirenen-Signals;
  • einen mit dem Empfänger gekoppelten Decoder, eingerichtet zum Decodieren des empfangenen Mud-Sirenen-Signals;
  • wobei der Decoder eingerichtet ist zum
    • • Decodieren des empfangenen Mud-Sirenen-Signals zu einem ersten Mehr-Bit-Signal, wenn die ermittelte Frequenz des empfangenen Mud-Sirenen-Signals in einem ersten Frequenzbereich ist;
    • • Decodieren des empfangenen Mud-Sirenen-Signals zu einem zweiten Mehr-Bit-Signal, wenn die ermittelte Frequenz des empfangenen Mud-Sirenen-Signals in einem zweiten Frequenzbereich ist; und
    • • Decodieren des empfangenen Mud-Sirenen-Signals zu einem dritten Mehr-Bit-Signal, wenn die ermittelte Frequenz des empfangenen Mud-Sirenen-Signals in einem dritten Frequenzbereich ist.
• Vergleichsbeispiel 15. Mud-Sirenen-Decodieranordnung gemäß Beispiel 14, wobei der Empfänger mindestens einen Drucksensor aufweist zum Empfangen des Mud-Sirenen-Signals.
• Vergleichsbeispiel 16. Mud-Sirenen-Decodieranordnung gemäß Beispiel 14 oder 15, wobei das erste Mehr-Bit-Signal, das zweite Mehr-Bit-Signal und das dritte Mehr-Bit-Signal jeweils mindestens oder genau zwei Bit aufweisen.
• Vergleichsbeispiel 17. Mud-Sirenen-Decodieranordnung gemäß einem der Beispiele 14 bis 16, wobei der erste Frequenzbereich und/oder der zweite Frequenzbereich und/oder der dritte Frequenzbereich kleiner oder gleich ungefähr 50 Hz ist.
• Vergleichsbeispiel 18. Verfahren zum Empfangen und Decodieren eines Mud-Sirenen-Signals, das mittels einer Bohrspülung, die durch mehrere
  • Mud-Sirenen und durch eine Bohrgarnitur gespült wird, übertragen wird, wobei das Verfahren aufweist:
    • • Empfangen von dem mittels der Bohrspülung übertragenen Mud-Sirenen-Signal;
    • • Ermitteln einer Frequenz des empfangenen Mud-Sirenen-Signals;
    • • Decodieren des empfangenen Mud-Sirenen-Signals zu einem ersten Mehr-Bit-Signal, wenn die ermittelte Frequenz des empfangenen Mud-Sirenen-Signals in einem ersten Frequenzbereich ist;
    • • Decodieren des empfangenen Mud-Sirenen-Signals zu einem zweiten Mehr-Bit-Signal, wenn die ermittelte Frequenz des empfangenen Mud-Sirenen-Signals in einem zweiten Frequenzbereich ist;
    • • Decodieren des empfangenen Mud-Sirenen-Signals zu einem dritten Mehr-Bit-Signal, wenn die ermittelte Frequenz des empfangenen Mud-Sirenen-Signals in einem dritten Frequenzbereich ist.
• Vergleichsbeispiel 19. Verfahren gemäß Beispiel 18, wobei das erste Mehr-Bit-Signal, das zweite Mehr-Bit-Signal und das dritte Mehr-Bit-Signal jeweils mindestens oder genau zwei Bit aufweisen.
• Vergleichsbeispiel 20. Verfahren gemäß Beispiel 18 oder 19, wobei der erste Frequenzbereich und/oder der zweite Frequenzbereich und/oder der dritte Frequenzbereich kleiner oder gleich ungefähr 50 Hz ist.

Comparative examples are described below:

• Comparative Example 1 Mud siren arrangement, comprising:
  • • a drilling set;
  • • a first mud siren arranged in the drilling assembly;
  • • at least one additional mud siren arranged in the drilling assembly;
  • • at least one coding device coupled to the first mud siren and the further mud siren; and
  • • wherein the first mud siren and the at least one further mud siren are arranged in such a way and the coding device controls the first mud siren and the further mud siren in such a way that at a coding time, information comprising a plurality of bits is encoded and transmitted by means of the first mud siren and the further mud siren.
• Comparative Example 2. Mud siren arrangement according to Example 1, wherein the first mud siren and the at least one further mud siren are arranged one behind the other in the drilling assembly.
• Comparative Example 3. Mud siren arrangement according to Example 1, further comprising:
  • wherein the first mud siren and the at least one further mud siren are arranged next to each other in the drilling assembly.
• Comparative Example 4. Mud siren arrangement according to any one of Examples 1 to 3,
  • wherein the coding device controls the first mud siren and the at least one further mud siren such that the first mud siren and the at least one further mud siren are driven at mutually different frequencies for coding the information having a plurality of bits.
• Comparative Example 5. Mud siren arrangement according to any one of Examples 1 to 4,
  • wherein the coding time is a start of a time slot. Comparative Example 6. Mud siren arrangement according to Example 4 or 5,
  • wherein the frequencies are less than or equal to about 50 Hz. Comparative Example 7. A method for encoding and transmitting information comprising a plurality of bits, the method comprising:
    • • Operating a first mud siren arranged in a drilling assembly at a first frequency;
    • • Operating at least one additional mud siren arranged in the drilling assembly at a further frequency which is different from the first frequency; and
    • • Controlling the first mud siren and the at least one further mud siren such that at a coding time the information comprising a plurality of bits is encoded and transmitted by means of the first mud siren and the at least one further mud siren.
• Comparative Example 8. The method of Example 7, wherein a substantially incompressible medium for transmitting the information to the earth's surface is flushed through the first mud siren and the at least one further mud siren.
• Comparative Example 9. Method according to Example 7 or 8, wherein the first mud siren and the at least one further mud siren are arranged one behind the other in the drilling assembly.
• Comparative Example 10. Method according to Example 7 or 8, wherein the first mud siren and the at least one further mud siren are arranged next to each other in the drilling assembly.
• Comparative Example 11. The method according to any one of examples 7 to 10, wherein the first mud siren and the at least one further mud siren are driven at mutually different frequencies for encoding the multi-bit information.
• Comparative Example 12. The method according to any one of examples 7 to 11, wherein the coding time is a start of a time slot.
• Comparative Example 13. The method of Example 11 or 12, wherein the frequencies are less than or equal to about 50 Hz.
• Comparative Example 14. Mud siren decoding arrangement comprising:
  • a receiver configured to receive a mud siren signal transmitted by a drilling fluid;
  • a decoder coupled to the receiver, configured to decode the received mud siren signal;
  • where the decoder is set up to
    • • decoding the received mud siren signal into a first multi-bit signal if the determined frequency of the received mud siren signal is in a first frequency range;
    • • decoding the received mud siren signal to a second multi-bit signal if the determined frequency of the received mud siren signal is in a second frequency range; and
    • • Decoding the received mud siren signal to a third multi-bit signal if the determined frequency of the received mud siren signal is in a third frequency range.
• Comparative Example 15. The mud siren decoding arrangement according to example 14, wherein the receiver comprises at least one pressure sensor for receiving the mud siren signal.
• Comparative Example 16. The mud siren decoding arrangement according to example 14 or 15, wherein the first multi-bit signal, the second multi-bit signal and the third multi-bit signal each have at least or exactly two bits.
• Comparative Example 17. The mud siren decoding arrangement of any one of Examples 14 to 16, wherein the first frequency range and/or the second frequency range and/or the third frequency range is less than or equal to about 50 Hz.
• Comparative Example 18. A method for receiving and decoding a mud siren signal generated by a drilling fluid passing through a plurality of
  • Mud sirens and flushed through a drilling set, the method comprising:
    • • Receiving the mud siren signal transmitted via the drilling fluid;
    • • Determining a frequency of the received mud siren signal;
    • • decoding the received mud siren signal into a first multi-bit signal if the determined frequency of the received mud siren signal is in a first frequency range;
    • • Decoding the received mud siren signal into a second multi-bit signal if the determined frequency of the received mud siren signal is in a second frequency range;
    • • Decoding the received mud siren signal to a third multi-bit signal if the determined frequency of the received mud siren signal is in a third frequency range.
• Comparative Example 19. The method of Example 18, wherein the first multi-bit signal, the second multi-bit signal and the third multi-bit signal each have at least or exactly two bits.
• Comparative Example 20. The method of example 18 or 19, wherein the first frequency range and/or the second frequency range and/or the third frequency range is less than or equal to about 50 Hz.

Claims (10)

A mud siren assembly comprising: • a stator having at least a first sub-stator and at least a second sub-stator; • a first mud siren having a first rotor, the first mud siren having a first open cross-sectional area when the first sub-stator and the first rotor at least partially overlap; • a second mud siren having a second rotor, the second mud siren having a second open cross-sectional area when the second sub-stator and the second rotor at least partially overlap; • the second sub-stator partially surrounding the first sub-stator; • the second rotor partially surrounding the first rotor; • the second open cross-sectional area partially surrounding the first open cross-sectional area. Mud siren arrangement according to Claim 1 , wherein the first partial stator is part of the first mud siren; and wherein the second partial stator is part of the second mud siren Mud siren arrangement according to Claim 1 , wherein the first partial stator part and the second partial stator are formed in one piece. Mud siren arrangement according to one of the Claims 1 until 3 , with the first Mud Siren being surrounded by the second Mud Siren. Mud siren arrangement according to one of the Claims 1 until 4 , wherein the first mud siren and the second mud siren each have one or more open cross-sectional areas. Mud siren arrangement according to one of the Claims 1 until 4 , wherein a sum of the one or more open cross-sectional areas of the first mud siren is equal to the sum of the one or more open cross-sectional areas of the second mud siren. Mud siren arrangement according to one of the Claims 1 until 5 , wherein the first mud siren and the second mud siren are arranged one behind the other with respect to a flow direction of the mud siren arrangement. Mud siren arrangement according to one of the Claims 1 until 5 , wherein the first mud siren and the second mud siren are arranged next to each other with respect to a flow direction of the mud siren arrangement. Mud siren arrangement according to one of the Claims 1 until 8th , further comprising: an encoding device which controls the first mud siren and the second mud siren such that the first mud siren and the second mud siren are driven at frequencies different from one another for encoding information having a plurality of bits. Mud siren arrangement according to Claim 9 , where the frequencies are less than or equal to 50 Hz.

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