OA20844A - Electro-acoustic transducer. - Google Patents

Abstract

Electro-acoustic transducer (10) adapted to be in contact with a fluid under pressure comprising: a tubular body (20) that extends in length along a longitudinal direction X, the tubular body (20) comprising a first end portion (21) and a second end portion (22), opposite to each other longitudinally, the tubular body (20) internally having a first chamber (23), which ends with the first end portion (21 ) and a second chamber (24), on one side adjacent to and in fluidic communication with the first chamber (23) and on the other side ending with the second end portion (22), the first end portion (21) being closed towards the outside by means of a membrane (26) applied to the tubular body (20). the second end portion (22) having one or more openings (27) that put it in fluidic communication to the outside of the tubular body (20). the first chamber (23) containing in its walls a plurality of electrical windings (25) arranged in succession to each other in the longitudinal direction X, the second chamber (24) being filled with a liquid; a movable.

Description

ELECTRO-ACOUSTIC TRANSDUCER

The présent invention relates to an electro-acoustic transducer particularly but not exclusiveiy usable in the oil sector.

Drilling of oil wells increasingly requires control of operations to minimize costs, times and risks. This has translated into an increase in the number of instrumentations présent on the head of the drilling battery (drillpipes and drillbit), the so-called bottom hole assembly, so as to accommodate, in addition to the typical instrumentation for monitoring the drilling parameters (Measure While Drilling - MWD), also instrumentations for the formation assessment, which operation was carrîed ont in the past when the drilling was stopped with dedicated instruments lowered into the well with a cable (tool wireline).

In order to monîtor the drilling progress and the State of the well in production, the use of geophysical analysis techniques based on the interprétation of the signal deriving from the reflection of acoustic waves and of techniques for the transmission of measurement data to the surface through the drilling mud has long been known in the oil industry. For geophysical analysis, the numerous technical solutions for the émission of seismic waves include hydraulic actuators that move a piston through hydraulic fines controlled by servo-valves. An example of a transducer device according to the prîor art is provided in US4702343 which describes a device for generating seismic waves for geological investigations.

For telemetry applications, the émission of acoustic waves provides for voice coil type actuators. Such devices are generally capable of generating pressure waves by modulating the flow of the drilling mud through servo-valves.

US20160146001 Al describes a so-called voice coil device for operating a movable element which détermines the opening and closing of a valve.

US20170167252A1 illustrâtes an actuator for a telemetry device of the mud puiser type which comprises a solenoid servo-valve.

For both applications, these devices are characterized by relatively large dimensions and the frequency band in which they operate is limited by the response times of the présent servovalves. Furthermore, these devices generally hâve sufficiently high energy consomption that requires the connection to an electrical power supply system which increases the installation complexity at high depths; finally, the above devices are not designed to operate at the high pressures that are typical of the working area at the well bottom.

US5247490A describes an acoustic-optical sensor which is pressure compensated to operate in high pressure environments such as the seabed.

In any case, the increase in instrumentations and the rate of pénétration leads to an increase în the demand for the amount of data transferred (monodirectional transmission from the well bottom to the surface) or exchanged (bidirectional transmission between the well bottom and surface) in the unit of time to monitor the drilling progress.

Various Systems are currently known for the bidirectional transmission to and from the well bottom, more particularly from and to the equipment of the well bottom, hereinafter called downhole tools. Current Systems are mainly based on the transmission of acoustic or elastic signais or of electrical or electromagnetic signais.

As far as the transmission of acoustic signais is concerned, the mud-pulser technology is known, which is based on the transmission of pressure puises through the drilling fluid présent in the well during ail drilling operations.

The use of the propagation of elastic waves in the métal of the drillpipes that make up the drilling battery is also known.

As far as the transmission of electromagnetic signais is concerned, a so~called wired pipe technology is known, în which the signais are transmitted through electrical conductors inserted in the drillpipes.

A wireless telemetry technology is also known in which electromagnetic signais are transmitted through the drilling fluid by using repeaters along the drilling battery to transport the signal to/from the surface or through the soil involved in the drilling.

Each of these technologies has some drawbacks.

The mud-pulser technology, in fact, has frequency, thus transmission speed, and reliability lîmits since it may be necessary to transmit the same signal several times before receiving it correctly. The transmission capacity of this technology dépends on the characteristics of the drilling fluid and the flow rate of this fluid.

The wiredpipe technology involves very high costs as the wired drillpipes are very expensive; moreover, lîke in the mud puiser technology, whenever it is necessary to add a drillpîpe to the drilling string, the wired connection is interrupted thus impedîng communication to and from the well bottom during these operations.

The technology based on the transmission of elastic waves in the métal of the drillstring involves potential errors in the transmission due to the operating noise of the chisel or to the déviation of the wells from vertîcality.

The technology based on the electromagnetic transmission through the soil, due to the low frequencies used to cover transmission distances in the order of kilometers, involves a very low transmission speed (équivalent to that of mud puiser” technology) and problems of reliability due to the Crossing of several formation layers with different electromagnetic propagation characteristics.

The object of the present invention is to provide an electro-acoustic transducer with reduced dimensions and capable of operating in a wider frequency range than the prior art.

Another object of the present invention is to provide a bidirect!onal data transmission System in a well for the extraction of formation fluids which is simple, reliable and inexpensive.

This and other objects according to the present invention are achieved by realising an electroacoustic transducer as described in claim 1 and by a bidirectional data transmission System as shown in claim 7.

Further characteristics of the electro-acoustic transducer and of the bidirectional data transmission System are the subject of the dépendent daims.

The features and advantages of an electro-acoustic transducer and of a bidirectional data transmission System according to the present invention will be more apparent from the following description, which is to be understood as exemplifying and not limiting, with reference to the schematic attached drawings, wherein:

- figure la is a section view of an electro-acoustic transducer according to the present invention;

- figure 1b is a view of a detail of the transducer of figure la;

- figure 2 is a schematic perspective view of an electrical winding present in the electro-acoustic transducer of figure 1;

- figure 3 îs a schematic view of a drilling rig for the extraction of hydrocarbons comprising a bidirectional data transmission System according to the present invention;

- figure 4a is a schematic top view of a first embodiment of a drillpipe of the rig of figure 3 which is part of the bidirectional data transmission System;

- figure 4b is a schematic section view along the line IV-IV of the drillpipe of figure 4a;

- figure 5a is a schematic top view of a second embodiment of a drillpipe of the rig of figure 3 which is part of the bidirectional data transmission System;

- figure 5b is a schematic section view along the line V-V of the drillpipe of figure 5a.

With reference to the figures, an electro-acoustic transducer is shown, îndicated overall with number 10. This electro-acoustic transducer 10 is in particular intended to be in contact with a pressurized fluid through which acoustic signais are received or transmitted. Furthermore, the electro-acoustic transducer 10 îs desîgned to operate as a transmitter or receiver of acoustic waves in the 450-5000Hz frequency range, preferably in the 5OO-3OOOHz frequency range.

The electro-acoustic transclucer 10 is axial-symmetrical and comprises a main tubular body 20 preferably of a cylindrical shape and preferably of ferromagnctic material which extends in length along a longitudinal direction X; this main tubular body 20 comprises a first end portion 21 and a second end portion 22 opposite to each other iongitudinally.

Furthermore, the main tubular body 20 internally has a first chamber 23 which ends with the first end portion 21 and a second chamber 24 on one side adjacent to and in fluidic communication with the first chamber 23 and on the other side ending with the second portion end 22.

The compartiment defined internally by the chambers 23, 24 can be of any preferably cylindrical shape.

The first end portion 21 is closed towards the outside by means of a membrane 26 applied to the main tubular body 20.

Said membrane 26 is preferably made of harmonie steel.

The second end portion 22 has one or more openings 27 which put it în fluidic communication to the outside of the main tubular body 20.

The first chamber 23 contains in its walls a plurality of electric windings 25 arranged in succession to each other in the longitudinal direction X.

The electric windings 25 are preferably made by means of metallic rings, preferably of copper séparaied by an insulatîng layer, for example an insulating film. This embodiment of the electric windings 25 is particularly advantageous for using the electro-acoustic transducer as an acoustic signal transmitter.

The electro-acoustic transducer 10 also comprises a movable element 30 housed in the first chamber 23; this movable element 30 advantageously comprises a plurality of permanent magnets 31, preferably but not necessarily cylindrical, packaged one above the other. In particular, the permanent magnets 31 are arranged with the magnétisation alternating in the longitudinal direction X, are stacked and separated from one another by dises 32 of ferromagnetic material and held together by a pin 33 which crosses them for example centrally as shown in figure 1.

The permanent magnets 31 are preferably made of Samarium-Cobalt.

The movable element 31 is supported at the longitudinal ends by springs 40, preferably by a pair of preloaded dise springs 40 as îllustrated in figure 1. Each of these springs 40 is constrained on one side to the movable element 31 and on the other side to the internai walls of the first chamber 23.

The movable element 30 is also advantageously connected to the membrane 26, preferably by means of an extension element 27 coupled on one side to an end of the movable element 30 and on the other side, to the membrane 26.

The electro-acoustîc transducer 10 further comprises a movable piston 45 posîtioned in the second end portion 22.

The second end portion 22 is preferably coupled to a bushing 28 that extends toward the interior of the second chamber 24 for a section of its length in such a way that it restricts the inner passage. In this case the movable piston 45 is posîtioned in the narrow inner passage.

The second chamber 24 is fi lied with a liquid, preferably oil.

When the electric windings 25 are electrically powered with a signal to be transmitted, the interaction between the variable magnetic field generated by the electric windings 25 and the permanent magnets 31 of the movable element 30 induces an oscillating translation of the movable element 30 which acts on the membrane 26 causing it to vibrate and thus causîng acoustic waves in the fluid surrounding the electro-acoustic transducer 10 in contact with the membrane 26 itself. The displacements of the movable element 31 cause a pressure variation inside the second chamber 24. These pressure variations are compensated by the movement of the movable piston 45 which is free to move according to the pressure différence that can temporarily occur between the environment oulside the electro-acoustic transducer and the second chamber 24. The movable piston 45 in fact reduces or increases the volume of the second chamber 24 in which oil is contained, thus obtaining the static pressure compensation.

This pressure compensation achieved by the piston advantageously allows usîng the electroacoustic transducer 10 in critical environments at high pressures up to about 700 bar.

The movable piston 45 and the second chamber 24 are sized to allow pressure compensation when acoustic signais are transmîtted and received in the entire frequency range specified above, i.e. 450-5000 Hz, preferably 500-3000 Hz.

In particular, the second chamber 24 is sized in such a way that the System composed of the movable element 30, the liquid contained inside the second chamber 24 and the movable piston 45, has an overall dynamic behaviour such as to guarantee the balance of the internai and extemal pressure, keeping the différence between the two pressure values close to zéro outside the entire 450-5000 Hz frequency range against a peak-to-peak displacement of the movable element 30 by a few tens of micrometers.

This behaviour is determined by the transfer function which is determined between the displacement of the movable element 30 and the pressure différence between the inside and outside of the electro-acoustic transducer 10. The transfer function dépends on the volume of the second chamber 24, on the section of the same chamber, on the mass and diameter of the movable piston 45 and on the elastic modulus of the liquid that fïlls the second chamber 24, normally referred to as the bulk module.

The length of the second chamber 24 is determined as a function of the internai section of the electro-acoustic transducer 10 i.e. the internai section of the first chamber 23, as a function of the mass, of the diameter ofthe movable piston 45 and of the bulk module of the liquid that fills the second chamber 24.

Since this latter parameter varies as a resuit of the type of liquid used, the pressure and the température, the sizing must be developed considering the most critical expected conditions. The sîzing is carried out on the basis of a dynamîc niodel of the System described by the following équations:

tilpX 4- β_ρΧ + β^Χ + ~ F + »1151 + βιϊι + + dl)'i — = -r H x v_t _ β&ι 7_τίρ λ rfr ~ K en / where F is the force generated by the transducer, x is the displacement of the movable element 30, yl is the displacement ofthe movable piston 45, PI is the pressure of the second chamber 24, Pest is the external pressure, Ap is the area of the cross section of the movable element 30, Al is the area of the cross section of the movable piston 45, Am is the area of the cross section of the membrane 26, VI-VI0 is the volume variation of the second chamber 24 due to the displacement of the fitting and movable piston βοϊ is the oil compressibility modulus, pm, βΐ and βρ are the damping coefficients of the membrane 26, of the movable piston 45 and of the movable element 30, respectively, mp and ml are the masses ofthe movable element 30 and ofthe movable piston 45, respectively, km, kp and kl are the stiffnesses of the membrane 26, the movable element 30 and the movable piston 45, respectively.

By way of example, in order to work at a température of 200°C and a pressure of 700 bar, the following configuration has been identified:

• membrane diameter 26 = 9.6 mm;

• diameter of the second chamber 24 = 8 mm;

• length of the second chamber 24 = 25.5 mm;

• section of the movable piston 45 = 6 mm;

• mass of the movable piston 45 = 0.9 g;

• oil elasticity modulus 1 < β < 2.5 GPa.

Furthermore, again by way of example, in order to maximize the transmitted power and sensitivity of the electro-acoustic transducer 10 in the 500-3000 Hz band, the équivalent stiffnesses ofthe pairs ofdise springs must be:

• 3.5 kN/mm for an electro-acoustic transducer intended to be used as a transmitter;

• 0.4 kN/mm for an electro-acoustic transducer intended for use as a receiver.

An electro-acoustic transducer 10 intended to be used as a transmitter is designed to operate for example in a steady State in the bands specified above, guaranteeing an acoustic power of approximately effective 20 mW.

An electro-acoustic transducer 10 intended to be used as a receiver is preferably designed to guarantee a transduction sensitivity of 20 Vs/m.

The bidirectional data transmission system 100 according to the présent invention will be described below.

This bidirectional data transmission system is particular]y usable in a well for the extraction of formation fluids, for example an oil well.

Furthermore, the bidirectional data transmission System can be used both in the drilling phase and in the production phase; therefore, the bidirectional data transmission System can be associated both with a drilling rig 100 and with a completion rig.

For simplicity of discussion, reference wj]l be made below to the application of the bidirectional data transmission system to a drilling rig 100 such as that illustrated in Figure 3. Said drilling rig 100 comprises a drilling string 110 comprising in turn a pîurality of drilling pipes 111 connected in succession to each other so as to form a drillstring of drillpipes and an excavation tool connected to the free termination of one of the end drillpipes of the string of drillpipes.

The drillpipes 111 hâve an internai through-duct 112 to allow the passage of a drilling fluid towards the bottom hole. This drilling fluid, as is known, goes up through the interspace between the string of drillpipes and the borehole walls, that is, through the so-called annulus.

In the case in which the borehole walls are covered by a casing, the annulus corresponds to the interspace between the string of drillpipes and the walls of the casing covering the borehole walls.

In the case of a completîon assembly, it comprises a completion tubing formed by pipes adapted to transport the fonnation fluid, for example oil. towards the surface.

In any case, the bidirectional data transmission System comprises a plurality of communication modules 120 arranged along the drilling or completion string and configured to transmit and/or receive information or command signais to and from the bottom hoie.

Hereinafter in the présent discussion, the considérations made for the drillpipesl 11 can be similarly applied to the completion tubing.

Each of these communication modules 120 comprises:

- at least one electro-acoustic transducer 10;

- a processing and control unit 50, for example comprising a microprocessor, associated with the at least one electro-acoustic transducer 10, configured to process signais to be transmitted and/or received by the at least one electro-acoustic transducer 10;

- a source of electric power supply 60, 70 electrically connected to the at least one electroacoustic transducer 10 and to the processing and control unit 50.

The communication modules 120, therefore, may comprise a single electro-acoustic transducer 10 configured as a transmitter, or a single electro-acoustic transducer 10 configured as a receiver, or a single electro-acoustic transducer 10 configured as a transceiver, or a pair of electro-acoustic transducers. one configured as a transmitter and the other as a receiver.

In any case, the at least one electro-acoustic transducer 10 of each communication module 120 is connected to the walls of a drillpipe or a completion tubing intemally or externally but in any case in contact with the drilling fluid.

The processing and control unit 50 is contained in a body applied to the drillpipe or to the completion tubing or in a compartment obtained in the drillpipe or tubing.

The source of electric power supply 60, 70 can comprise one or more batteries 60 contained in a body applied to the drillpipe or to the completion tubing or in a compartment obtained in the drillpipe or tubing. Alternatively, or in addition to the batteries 60, the source of electric power supply 60, 70 can comprise at least one generating device 70 configured to generate electric energy from the flow of the drilling fluid. For example, this generating device 70 can be, for example, a turbine located on the passage of the drilling fluid, configured to collect the energy from the flow of the drilling fluid and generate electrical energy so as to supply the electroacoustic transducer and/or to charge the batteries 60 in such a way as to guarantee the operation of the electro-acoustic transducer 10 even in the event of temporary interruptions of drilling fluid flow.

In the embodiments illustrated in figures 4a and 5a the drillpipe provided with the communication module 110 has a narrowing ofthe ducf for the drilling fluid.

Jn the embodiment of figure 4a the walls of the drillpipe hâve, at this narrowing, channels facing the duct in which the généraiing devices 70 are positioned, in particular some turbines.

In the embodiment of figure 5a the generating device 70, in particular a turbine, is positioned in the central duct.

The transmission and réception of signais carried out by means of the electro-acoustic transducers 10 allows covering considérable distances at the frequencies indicated above.

In a particular embodiment, the bidirectional data transmission System comprises two communication modules 120 each comprising a respective pair of electro-acoustic transducers configured as a transmitter and receiver.

In this case, a communication module 120 is arranged at the so-called bottom hole assembly and the other communication module 120 is placed in the proximity of the movement unit of the drillpipess or the so-called top drive.

From the above description the features of the electro-acoustic transducer and of the bidirectional data transmission System of the présent invention, as well as the advantages thereof, are clear.

Lastly, it is clear that the electro-acoustic transducer and of the bidirectional data transmission system thus conceived are susceptible to numerous modifications and variants, without departing from the scope of the invention; moreover, ail details can be replaced with teclinically équivalent éléments. In practice, the materials used, as well as the dimensions thereof, can be of any type according to the technical requirements.

The invention is not limited to the embodiment/s illustrated in the drawings. Accordingly it should be understood that where features mentioned in the appended claims are followed by reference signs, such signs are inciuded solely for the puipose of enhancing the intelligibility of the claims and are in no way limiting on the scope of the claims.”

Claims (10)

1) An electro-acoustic transducer (10) adapted to be în contact with a fluid under pressure comprising:

- a tubular body (20) that extends in length along a longitudinal direction X, said tubular body (20) comprising a first end portion (21) and a second end portion (22), opposite to each other longitudinally, said tubular body (20) internaily having a first chamber (23), which ends with the first end portion (21) and a second chamber (24), on one side adjacent to and in fini die communication with said first chamber (23) and on the other side ending with said second end portion (22), said first end portion (21) being closed towards the outside by means of a membrane (26) applied to said tubular body (20), said second end portion (22) having one or more openings (27) that put it in fluidic communication to the outside of said tubular body (20), said first chamber (23) containing în its walls a pluraiity of electrical windings (25) arranged in succession to each other in the longitudinal direction X, said second chamber (24) being fîlled with a liquid;

- a movable element (30) housed in said first chamber (23), said movable élément (30) comprising a pluraiity of permanent magnets (31) packaged and arranged in succession to each other în the longitudinal direction X, wdth the magnétisation alternating in the longitudinal direction X and separated from one another by dises of ferromagnetic material, said movable element (31) being supported at the longitudinal ends by springs (40), said movable element (30) being also connected to said membrane (26);

- a movable piston (45) positioned and slidable in the second end portion (22).

2) An electro-acoustic transducer (10) according to claim 1, wherein said electrical windings (25) are made by means of metallic rings separated by an insulating layer.

3) An electro-acoustic transducer (10) according to claim 1 or 2, wherein said movable element (30) is connected to said membrane (26) by means of an extension element (27) coupled on one side to an end of the movable element (30) and on the other side, to the membrane (26).

4) An electro-acoustic transducer (10) according to one of the preceding daims, wherein said springs (40) are a pair of preloaded dise springs (40).

5) An electro-acoustic transducer (10) according to any one of the preceding daims, wherein said second end portion (22) is coupled to a bushing (28) that extends toward the interior ofthe second chamber (24) for a section of its length in such a way that it restricts the inner passage, said movable piston (45) being positioned in the narrow inner passage.

6) An electro-acoustic transducer (10) according to any one of the preceding daims, wherein said movable piston (45) and said second chamber (24) are sized to allow pressure compensation when acoustic signais are transmitted or received in the 450-5000Hz frequency range.

7) An electro-acoustic transducer (10) according to any one of claims 1 to 5, wherein said movable piston (45) and said second chamber (24) are sized to allow pressure compensation when acoustic signais are transmitted or received in the 500-3000Hz frequency range

8) A bidirectional data transmission System adapted to be installed in a drilling string or completion assembly of a well for the extraction of formation fluîds comprising:

- a plurality of communication modules (120) arranged along a drilling or completion string, and configured to transmit and/or receive information or control signais to and from the well bottom, each of said communication modules (120) comprising:

- at least one electro-acoustic transducer (10) according to one or more of the preceding claims, said at least one electro-acoustic transducer (10) being connected to the walls of a drillpipe (111) or of a completion tubing internally or externally but still in contact with a drilling fluid;

- a processing and control unit (50) associated with said at least one electro-acoustic transducer (10), configured to process signais to be transmitted and/or received by said at least one electro-acoustic transducer (10);

- a source of electric power supply (60, 70) electrically connected to said at least one electro-acoustic transducer (10) and to said processing and control unit (50).

9) A bidirectional data transmission System according to claim 8, wherein said source of electric power supply (60, 70) comprises one or more batteries (60).

10) A bidirectional data transmission System according to claim 8 or 9, said source of electric power supply (60, 70) comprises at least one generating device (70) configured to generate electric energy from the flow of the drilling fluid.