WO2016097276A1

WO2016097276A1 - Data transfer system and downhole tool for transmitting data signals in a wellbore

Info

Publication number: WO2016097276A1
Application number: PCT/EP2015/080459
Authority: WO
Inventors: Willem Hubertus Paulus Maria HEIJNEN; Thomas Hahn-Jose
Original assignee: Maersk Olie og Gas AS
Current assignee: Total E&P Danmark AS
Priority date: 2014-12-18
Filing date: 2015-12-18
Publication date: 2016-06-23
Anticipated expiration: 2017-06-18

Abstract

A downhole data transfer system for transmitting data through fluid in a well bore is presented, wherein the well bore is filled with said fluid. It comprises a first transducer device being adapted to be positioned down the well bore, comprising a first transducer (30), a first housing (28) having an opening, first communication electronics for providing a data signal to the first transducer, a first membrane (40) positioned at the opening of the first housing having a peripheral portion, wherein the first membrane is attached with its peripheral portion to the first housing, wherein the first transducer is attached to a backside of the first membrane, wherein the first transducer excites the first membrane in response to the data signal generated by the first communication electronics to generate at least one sound wave to propagate through said fluid. It further comprises a second transducer device being adapted to be installed at or near an access of the well bore comprising a second housing having an opening, a second transducer, a second membrane positioned at the opening of the second housing and having a peripheral portion, second communication electronics connected to the second transducer for obtaining the data signal from the second transducer, wherein the second transducer is attached to a backside of the second membrane, wherein a fluid column coupling is established between the first membrane and the second membrane.

Description

Data Transfer System and Downhole Tool for Transmitting Data Signals in a Wellbore

Specification

Field of the invention

The invention is related to a data transfer system and a downhole tool for transmitting data signals through a fluid in a wellbore using sound waves. Background and Summary of the invention

Well bores are used in the petroleum and natural gas industry to produce hydrocarbons (production well) or to inject fluids, for example water, CO₂ and/or Nitrogen

(injection well) . Typically, such fluids are injected to stimulate, i.e. to enhance the hydrocarbon recovery.

Lately, CO₂ injection has been introduced to this to reduce the C0₂-concentration in the atmosphere in order to defeat global warming. Typically, a well bore is lined with a steel pipe or steel tubing, generally referred to as casing or liner, and cemented in the overburden section to reduce the risk of unwanted evacuation of fluids from the overburden and/or the reservoir into the surface environment. For completion of the reservoir section at present several options are typically used, namely open hole completion, or using a liner with several formation packers for sealing off sections of the annulus around the steel liner, or using a steel liner which is cemented in place and access to the reservoir is gained by perforating the liner and cement in a later stage of the completion, or completion of the well with a liner in open hole which has predrilled holes in the liner to gain access to the reservoir. It should be noted that the later holes can also be made in a later stage of the well life. During the production or injection of fluids from a well bore in an earth formation the well bore can enlarge due to chemical reactions and/or an instability of the borehole. This may occur due to injection or production pressure changes and/or erosion which can take place e.g. in case of production from unstable geological formations such as turbidites known for their unpredictable sand face failure resulting in massive sand production leading to well failure. Furthermore, when injection processes are being used fractures can be generated resulting in undesired direct communication between the injection and production wells. On the other hand the well can collapse, for example caused by compaction, a process which happens when the pressure in the reservoir reduces, or by the use of

chemicals used to improve injectivity or productivity. The latter can cause a collapse of the annulus and therewith possibly block the access to the reservoir and, therewith, preventing injection or production. Another important aspect is a phenomenon which is called cross flow in the annulus. Cross flow in the annulus is the result of

pressure differences along the liner of the production or injection well in an un-cemented completion. The latter can lead to loss of production and/or loss of economic

reserves . The well bore and/or the casing or liner and/or the

reservoir section may be subject to inspection e.g. in order to verify physical properties such as pressure or temperature, more general to collect information about the status, or in order to observe defects or anomalies, in particular in order to prevent collapses of all kind of the well .

As the total length from the reservoir to an access at the top end of the well bore may sum up to several hundred or even several thousand meters retrieving such data, e.g. to an extraction facility at said access, is difficult and subject to continued development.

It is particularly desirable to deliver the data related to the afore-mentioned phenomena, which is, however, difficult because of the environmental conditions, e.g within a steel pipe or steel tubing extending between the reservoir and the access.

Therefore, it is an object of the invention to provide a tooling equipment for transmitting data from and/or to data sources in the well bore, e.g. a downhole tool in the well bore .

A further aspect of the object of the invention is to provide communication between the surface, e.g. the

extraction facility, and a downhole tool in the well bore.

The object of the invention is achieved by subject matter of the independent claims. Preferred embodiments of the invention are subject of the dependent claims.

A downhole data transfer system for transmitting data through fluid in a well bore, wherein the well bore is filled with said fluid, comprises a first transducer device being adapted to be positioned down the well bore. The first transducer device therefore is built e.g. to sustain environmental conditions occurring at a depth in the well bore. The downhole data transfer system is able to transmit data through fluid, which typically contains hydrocarbon, and along the well bore, e.g. through the casing or liner or through open hole. The fluid in the casing or liner and in an annulus around the casing or liner comprises

particularly oil, natural gas and/or water of specific pressure and temperature, so that e.g. the propagation speed of the sound signals depends on these fluid

properties . The first transducer device comprises a first transducer. The first transducer converts the data signal between one type of energy, e.g. an electrical data signal, and one other type of energy, e.g. a sound signal. The first transducer may work in one direction, e.g. converting from the electrical data signal to the sound signal.

The first transducer device further comprises a first housing having an opening. The opening preferably has a round shape, e.g. is circular, but may also be e.g. of quadratic or rectangular form.

A first membrane is positioned at the opening of the first housing. The first membrane may e.g. rest against the opening of the first housing or it may grip into the opening. Preferably the first membrane is adapted to be an opening-spanning membrane, thus the membrane spans the opening and, as a result, functions as a closure for the opening of the first housing to separate an inside of the first housing from an outside of the first housing. A frontside of the membrane is directed towards the outside, e.g. towards said fluid in the well bore. A backside of the membrane is directed towards the inside of the first housing. In other words, the first membrane can be seen as a part of an outer, e.g. watertight, overall hull of the first housing. The first membrane has a peripheral portion, wherein the first membrane is attached with its peripheral portion to the first housing.

The first transducer device has first communication

electronics for providing a data signal to the first transducer. The first communication electronics thus generates the data signal, e.g. an electric data signal, wherein the data may be refined such, that the first transducer is able to excite the first membrane being fed by said data signal. The data signal thus not only contains the information to be transmitted but may also provide enough electric power to operate the first transducer, e.g. by adjusting the voltage level of the data signal to achieve a satisfying excitation level of the membrane being excited by the first transducer.

The first transducer is attached to the backside of the first membrane, so that it can act directly on the

membrane. The first transducer is preferably glued to the backside of the first membrane but it may also be screwed or welded. The first transducer excites the first membrane in response to the data signal generated by the first communication electronics to generate at least one sound wave to

propagate through said fluid. Thus, in an example the data signal is processed by the communication electronics in a way that it is capable of driving the first transducer in order act on the first membrane to make it release at least one sound wave, or in other words to excite the first membrane. Excitation of the first membrane releases said at least one sound wave, wherein the data to be transmitted is contained in the sound waves, e.g. by employment of a modulated carrier frequency.

The downhole data transfer system comprises a second transducer device being adapted to be installed at or near a top end of the well bore. The second transducer device receives the sound waves released by the first transducer device. The second transducer device my e.g. be installed at or near the access or the extraction facility, where the casing or liner ends. The second transducer device can also be installed anywhere in the well bore, e.g. acting as a signal repeater, or being connected to a wire, glass fiber or other well component. The second transducer device comprises a second housing having an opening, a second transducer and a second

membrane positioned at the opening of the second housing having a peripheral portion. The second transducer device further comprises second communication electronics

connected to the second transducer for obtaining the data signal from the second transducer, wherein the second transducer is attached to a backside of the second

membrane .

Between the first membrane of the first transducer device and the second membrane of the second transducer device a fluid column coupling is established. Fluid column coupling is achieved e.g. when the first membrane and the second membrane both have direct contact with said fluid and the sound waves propagate through the fluid from one membrane to the other.

As an option, the first membrane is adapted to sustain a pressure difference between the frontside and the backside of the first membrane resulting from a fluid column lasting on the first membrane of 10 bar or more, of 50 bar or more, but the first membrane may even sustain such a pressure difference resulting from a fluid column lasting on the first membrane of 100 bar or more. However, if there is a pressure difference between the frontside of the membrane and the backside of the membrane, exiting the membrane will require higher energy levels for sending and/or receiving. Thus by equalization of the pressure at the backside of the membrane to the pressure level present in the fluid, the energy needed for

excitation of said membrane is greatly reduced. Due to the fact, that the amount of energy stored in or generateable by the downhole tool limits the lifetime of the downhole tool, reduction of the excitation energy thus extends its lifetime. An example for such pressure equalization is depicted in short below and is subject of a parallel patent application . The downhole tool may for that purpose comprise a

specialized pressure compensation system which is capable of balancing the inside pressure of the downhole tool to the outside pressure in the dedicated pressure range, e.g. up to 1000 bar.

The housing comprises a fluid inlet at one side, which may in a simple embodiment just be an opening through which the outside fluid may stream in and/or stream out. The fluid inlet may include a channel portion inside the housing, wherein the channel portion of the fluid inlet may connect the outside of the housing with a first chamber inside the housing. The housing is surrounded by an outside fluid, the fluid inlet thus is open to said outside fluid. In case the downhole tool is being deployed into the well bore, the outside fluid is the well bore fluid.

Inside the housing a first chamber gives room for

installation of downhole equipment such as the first membrane or the first transducer or the like. The

installation spot for installation of downhole equipment is referred to as a frontside of the first chamber. The term frontside is not related to the orientation of the first chamber with respect to the housing. The term frontside shall only name a side of the first chamber, wherein the frontside of the first chamber could also be situated at a back end of the housing. In other words, a region or a subchamber of the first chamber may be used for

installation of downhole equipment. The first chamber is filled with a chamber fluid. It is preferred, that the chamber fluid is a gas, particularly air. By way of example, the first chamber is filled with surface air, which is air having the pressure present at the surface. In this example, the installations inside the downhole tool may be installed under simple environmental conditions, e.g. in a laboratory or a downhole tool

manufacturing facility, e.g. in any air pressure condition in the range of the standard atmosphere pressure of 1013.25 mbar.

The frontside of the first chamber may be separated from the remaining part of the first chamber e.g. by a

constriction or by a separating wall having an opening or the like.

A flexible divider is arranged inside the first chamber. The flexible divider sealingly engages the inner side of the fluid inlet. The flexible divider defines an expandable second chamber at an inner side of the flexible divider, so that the expandable second chamber is fillable with the outside fluid through the fluid inlet. In other words, the flexible divider emcompasses the fluid inlet and thus seals the fluid inlet against the first chamber, wherein the fluid inlet opens out into the inner side of the flexible divider, which is the expandable second chamber.

The flexible divider might, for ease of understanding, in a simple embodiment be described as a balloon which could be put over an inner flunge of the fluid inlet. When the pressure present at the fluid inlet is higher than the pressure inside the first chamber, the balloon will expand and thus compress the chamber fluid. However, it is to be understood, that the flexible divider may also be of other shape. By way of example, the flexible divider may be a movable wall inside the downhole tool, e.g. between the expandable second chamber and the first chamber. Or in case the first chamber is of cylindrical shape, the flexible divider may have the shape of a piston moving inside the first chamber and by its movement defining the size of the expandable second chamber. However, the balloon-like shape has some advantages for this purpose, as the space inside the first chamber may be used e.g. for cable installations along the first chamber which would be difficult to realize in case of e.g. a piston, as the first chamber is

preferably sealed against the expandable second chamber.

The flexible divider may equal the chamber fluid pressure to the outside fluid pressure. The equalization of the pressure levels may be achieved by movement of the flexible divider, or, in other words, by way of changing the size of the expandable second chamber.

A chamber fluid collector is installed for providing the chamber fluid to the frontside of the first chamber in case the expandable second chamber expands . The chamber fluid collector extends along the flexible divider. By way of example, the chamber fluid collector can be realized with installing a twisted pair cable, which may be also used for electrical signal or current transport through the downhole tool, e.g. for signal transport between the first

transducer and the first communication electronics. The chamber fluid collector can be mounted at an outer wall of the first chamber. The function of the chamber fluid collector shall be explained by way of example: With rising outside pressure level, the flexible divider starts to expand due to influx of outside fluid into the expandable second chamber. Particularly preferred the flexible divider thereby balances outside pressure level and inside pressure level of the chamber fluid (chamber fluid pressure) . With continued expansion of the flexible divider, the flexible divider begins to come in contact with the outer wall of the first chamber. The flexible divider continues to press against the outer wall of the first chamber possibly isolating regions containing chamber fluid between the flexible divider and the outer wall of the first chamber. However, the chamber fluid advantageously should be

collected at the frontside of the first chamber, so that the flexible divider, when continuing to expand, does not come in contact with the downhole equipment at the

frontside. The chamber fluid forms a cushion at the

frontside, e.g. around the downhole equipment, when further compressed. In order to collect all chamber fluid and to guide it to the frontside of the first chamber, the chamber fluid collector is installed along which the chamber fluid may reach the frontside. In the embodiment depicted above with a twisted wire, the flexible divider presses on the twisted wire, but between the wires channels remain through which the chamber fluid may evacuate from the isolated regions between the flexible divider and the outer wall of the first chamber.

The outside fluid comprises an outside fluid pressure, which is mainly depending on the type of fluid, e.g. oil or water, the temperature of the fluid and/or the position of the downhole tool, e.g. the diving depth of the downhole tool in the wellbore. The chamber fluid comprises an initial chamber fluid pressure, which by way of example may be adjusted before deployment of the wellbore tool. It is particularly preferred, if the flexible divider equals the chamber fluid pressure to the outside fluid pressure by means of expansion or shrinkage of the

expandable second chamber. In order to allow the flexible divider to tolerate volume increase of the expandable second chamber by e.g. a factor of up to 1000, the flexible divider may be made of

stretchable material. The flexible divider may

particularly be made of rubber. However, the material of the flexible divider should, at least at its inner side, withstand the composition of the wellbore fluid, which may be acid or anyhow chemically aggressive.

In an embodiment, the second chamber comprises a smallest volume and a maximum volume, wherein the flexible divider has a relaxed state thereby defining the smallest volume of the second chamber. In other words, the smallest volume of the second chamber is defined by the volume which is circumfered by the flexible divider in its relaxed state.

The volume of the second chamber may vary in a wide range due to adaptation to the outside fluid pressure. A volume ratio of the maximum volume of the second chamber to the smallest volume of the second chamber may reach 100 or more, e.g. 1000 or more. The flexible divider may, in an embodiment, be realized as an elongated tube. The elongated tube may be arranged along the centre of an elongated first chamber, e.g. held in place in its relaxed state using a wire grid or the like.

It is thus preferred to install the described pressure compensation system also to the downhole tool described herein .

The first membrane may have a thickness of at least

1 millimeter and the material of the membrane is chosen to withstand the pressure differences which may result down the well bore but should also produce high quality and/or high intensity sound waves. Preferably, the first membrane is therefore a metal membrane, in particular made of

Aluminum, Stainless Steel, Titanium and/or A1203.

The first membrane may, by way of example, have a thickness of above or equal to 5 millimeter or even above or equal to 10 millimeter. A further increase of material thickness decreases the intensity of the sound waves.

Particularly preferred the first transducer and the second transducer are transceivers, thereby establishing

bidirectional data transmission in the well bore. In other words, the first communication electronics, the first transducer and the first membrane correspond respectively to the second communication electronics, the second

transducer and the second membrane such that both

transducer devices are capable of both receiving and transmitting data.

In an embodiment of the invention the first and/or the second transducer is a piezo driver. The first and/or the second transducer can also be a magneto restrictive, magnetic, electric, capacity and/or thermal driver.

Further preferred is an embodiment wherein the first and/or the second transducer comprises at least two piezo- electrically active layers. The piezo-electrically active layers are arranged on top of each other, so that a first piezo-electrically active layer is in contact with the corresponding membrane and a second piezo-electrically layer is on top of and in contact with the first piezo- electrically active layer.

The first transducer may be arranged inside the first housing. In other words, the backside of the first membrane is directed towards the inside of the first housing, the first membrane lies at the opening of the first housing and the first transducer, which is attached to the backside of the membrane, is situated in the opening of the first housing, which is inside the first housing, when the first membrane is seen as a part of the overall hull of the first housing. The second transducer may also be arranged inside the second housing.

The invention also provides a downhole tool being adapted to be positioned down in a well bore for transmitting data through a fluid in the well bore. The downhole tool comprises a transducer, a housing having an opening, a first membrane positioned at the opening of the first housing having a peripheral portion, wherein the first membrane is attached with its peripheral portion to the first housing and wherein the first transducer is attached to a backside of the first membrane. The downhole tool may further comprise communication electronics connected to the transducer. With the communication electronics the data signal may be generated to feed the first transducer and/or the signal from the first transducer corresponding to an excitation of the membrane due to a signal in the well bore may be analysed and/or processed. Such signal in the well bore is e.g. a data signal sent from another downhole tool or from the extraction facility, so that it can be received by the downhole tool. In other words, the first membrane is designed such that it is excitable by the signal in the well bore. The membrane thus may have a certain thickness and/or a certain material being capable of resisting environmental conditions as well as being sensitive for the signal in the well bore. Preferably, the first transducer excites the first membrane in response to a data signal generated by the communication electronics to generate at least one sound wave to

propagate through said fluid in the well bore. In an especially preferred configuration the first transducer is a transceiver capable of both sending and receiving data signals via the first membrane through the fluid in the well bore.

The first transducer may be a piezo-electric driver. The piezo-electric driver, comprising e.g. a piezo-electric ceramic material, may be attached, e.g. glued or screwed or welded, directly to the backside of the membrane.

Research has shown, that for the purpose of this invention it is advantageous to use at least a first piezo- electrically active layer and a second piezo-electrically active layer. The first and second piezo-electrically active layers may then be arranged on top of each other. It is then particularly preferred to operate the piezo- electrically active layers serial in an acoustic point of view, so that driving the piezo-electrically active layers sums up to an overall first transducer signal strength. The use of at least the first and second piezo-electrically active layer reduces electric load impedance especially in a lower frequency range as compared to a single piece piezo-electric driver and thus provides high efficiency.

The at least first and second piezo-electrically active layers each comprise a respective first pole, and

preferably the at least first and second piezo-electrically active layers are arranged such, that the first

electrically active layer has the first pole directed towards the first membrane whereas the second piezo- electrically active layer has the first pole directed away from the first membrane. In other words, the piezo- electrically active layers are arranged inverse to each other, wherein each second piezo-electrically active layer is operated electrically reversed. Each piezo-electrically active layer thus contributes to the overall first

transducer signal. Advantageously, by electrically

combining several contacts of the piezo-electrically active layers, the amount of wiring can be reduced in this arrangement .

In a preferred embodiment, the first membrane and/or the second membrane is substantially planar. A substantially planar membrane on the one hand is easy to manufacture and thus cost-effective, on the other hand it has turned out, that it delivers sufficient signal strength and is capable of receiving the signal in the well bore.

The first membrane and/or the second membrane may further be substantially circular. It has been found out that with the relatively thick membranes to be used within the present invention the circular membrane provides a good behaviour for signal transmission, e.g. excitation of the membrane consumes a relatively low amount of energy and higher-order modes of oscillation may be separated.

The peripheral portion of the first membrane is

advantageously circumferentially sealingly engaged to the housing. In other words, the first membrane is in contact to the housing at an outer circumference of the membrane.

Preferably, the first housing further comprises an annular membrane sealing surface surrounding the opening of the first housing. The annular membrane sealing surface can be engaged circumferentially by the peripheral portion of the first membrane. In a particularly preferred embodiment of the invention, the first membrane has a first diameter and the opening has a second diameter wherein the first diameter exceeds the second diameter such, that the first membrane is larger than the opening. The annular membrane sealing surface is arranged around the opening at an outside of the housing. The annular membrane sealing surface may have a third diameter which matches the first diameter of the peripheral portion of the first membrane.

The first membrane can particularly engage the annular membrane sealing surface of the first housing at its peripheral portion so that the membrane is clamped at the peripheral portion and a node of an oscillation of the first membrane is established at said peripheral portion in case the first membrane oscillates. In other words, the first membrane is fixated around its first diameter and an inner portion of the first membrane is allowed to oscillate free. The inner portion of the first membrane corresponds in this embodiment to a diameter of an inner edge of the annular membrane sealing surface.

The first membrane may further comprise holes or recesses, which are situated at the peripheral portion or, in other words, along the circumference of the first membrane, for securely fixing the first membrane to the first housing. Preferably, the first membrane is fixed to the annular membrane sealing surface using screws which are inserted into the holes or recesses and which grip into screw threads of the annular membrane sealing surface. The holes or recesses may be, as an example, drilled into the first membrane .

The central portion of the first membrane preferably has a first thickness, wherein the peripheral portion of the first membrane has a second thickness, and wherein the first thickness exceeds the second thickness. In such a configuration, the central portion may also have a fourth diameter smaller than the third diameter of the annular membrane sealing surface such that the central portion engages into the opening when the peripheral portion of the membrane sealingly engages the annular membrane sealing surface. However, the second thickness of the peripheral portion can also exceed the first thickness of the central portion, which is advantageously due to the improve in signal amplitude having a thinner oscillating portion of the membrane. In other words, the membrane can be fixed to the annular membrane sealing surface at the comparatively thick peripheral portion and can oscillate with the rather thin central portion. The central portion however should be thick enough to withstand pressure levels down the well bore.

The wave motion of the frontside of the first membrane couples the data signal into the fluid of the well bore, wherefore it is especially advantageous when the frontside of the first membrane is in contact with said fluid. Thus when the downhole tool is discharged into the fluid in the well bore and the first membrane is positioned such, that it can be seen as part of the outer hull of the downhole tool, the frontside of the first membrane is in contact with said fluid.

The downhole tool employs preferably a data transfer working frequency, wherein the data signal e.g. is

modulated using known modulation techniques (e.g. amplitude modulation or frequency modulation) . The data transfer may also be undertaken by pulse modulation at the working frequency. Most preferred the data transfer working frequency is higher than the frequency of environmental sound in the wellbore.

Excitation of the membrane by the first transducer

preferably substantially only generates first order

oscillation, in particular of oscillation mode 01. It has been found out that signal strength of the data signal generated by the downhole tool can be maximized with respect to the used amount of electric power for excitation of the membrane when the membrane is excited at or near a resonance frequency, which corresponds to the lowest vibrational mode 01. However, the absolute frequency of said resonance frequency of the vibrational mode 01

depends, among other influences, from the membrane

diameter, the membrane thickness and the material chosen for the membrane .

It has been found out, that the downhole tool operating at a working frequency which is set higher than or equal to 2 kHz can deliver satisfying signal intensities. But also a working frequency of the downhole tool which is set higher than or equal to 1.5 kHz or higher than or equal to 1 kHz still results in satisfying signal intensities. On the other side, the downhole tool preferably operates at a working frequency which is set lower than or equal to 100 kHz, more preferably 40 kHz or even more preferably 20 kHz. A high working frequency, e.g. above 100 kHz, may lead to an increase of electric power to be fed to the first transducer for generating the at least one sound wave with satisfying intensity, e.g. satisfying sound pressure. The working frequency may even be set lower than 10 kHz depending on the diameter, thickness and material of the membrane. In other words, the working frequency is set such that excitation of higher-order modes of oscillation of the first membrane is found to be marginal.

Preferably, the downhole tool is designed as an autonomous downhole tool in this respect, that it can operate without external energy supply. This may be achieved by having a stand-alone power supply such as a battery pack.

Particularly preferred the stand-alone power supply

comprises a power generator for extending the lifetime of the downhole tool, e.g. by feeding said battery pack. The power generator could be implemented as an electric energy harvesting system using the transformation of sound energy, e.g. provided by the second transducer system or by

environmental noise, into electric energy.

The downhole tool for transmitting data signals through the fluid in the well bore may be part of a multifunctional downhole tool which, for example, collects data in the well bore and/or the reservoir or which operates other functions particularly for sustaining the well bore, e.g. does cementations of an outer wall of the well bore or the like. Thus the downhole tool gains the functionality of a

communication equipment in order to exchange data e.g. with a central station in the extraction facility.

In case more than one downhole tool is deployed in the well bore each downhole tool may have assigned an individual code when sharing the same working frequency, wherein assignment techniques known e.g. from digital networks, which operate at a shared working frequency, can be

implemented. Each downhole tool may also use an individual working frequency. In an embodiment, the first membrane may withstand not only high pressures such as more than 50 or 100 bar, but it may also withstand high temperatures such as 320 K or more, 370 K or more or even 470 K or more. Using a metal membrane with melting points in a range of e.g. more than 900 K provides a high reserve in that respect. The first membrane may also be adapted to withstand other environmental conditions such as acidity.

The pressure lasting on the first membrane may be obtained mainly from the fluid column pressure lasting on it in a given depth in the well bore. In the case the downhole tool or the first transducer device communicates with a second device, e.g. a second transducer device, installed at or near the access, for example at the extraction facility, this pressure level is significantly higher than the fluid column pressure lasting on the second membrane of the second transducer device. The fluid column pressure lasting on the first membrane may exceed the fluid column pressure lasting on the second membrane by a factor of 100 or more.

The first membrane or the annular membrane sealing portion may further comprise additional sealing means for sealingly closing a gap between the first membrane and the opening of the first housing, especially to seal the first housing against the fluid having high fluid column pressure. The invention is described in more detail and in view of preferred embodiments hereinafter. Reference is made to the attached drawings wherein like numerals have been applied to like or similar components.

Brief Description of the Figures

It is shown in

Fig. 1 a schematic cross-sectional view of an earth

formation with a downhole data transfer system in a well bore;

Fig. 2 another schematic cross-sectional view of an

earth formation with a downhole tool in a well bore having a horizontal section partly covered by a liner;

Fig. 3 a photographic view of a backside of a first

membrane ;

Fig. 4 a sketched side view of a first membrane;

Fig. 5 a photographic view of a backside of a second

embodiment of the first membrane having a multi- layered transducer at its backside;

Fig. 6 a schematic sideview of a multi-layered

transducer having four layers to be attached to the backside of a membrane;

Fig. 7 Circular Membrane Modes;

Fig. 8 Sideview of a Downhole Tool;

Fig. 9 frontal view of the first side of a downhole tool having an opening;

Fig. 10 Relative static displacement as a function of

thickness of the piezo driver; Fig. 11 Relative static displacement as a function of thickness of the piezo driver, the membrane being a metal membrane made of Aluminum;

Fig. 12 a photographic view of a test setup with a first and a second transducer device;

Fig. 13 Peak-to-Peak pressure as a function of excitation frequency;

Fig. 14 a sketched side view of a downhole tool having a pressure compensation system.

Detailed Description of the Invention

In Fig. 1 a well bore 2 is drilled in an earth formation 4 to exploit natural resources like oil or gas. The well bore 2 continuously extends from the extraction facility 9 at or near the surface 6 to a reservoir 8 of the well bore 2 situated distal from the wellhead 10 at the extraction facility 9. A casing/liner 12 in the form of an elongate steel pipe or steel tubing is located within the well bore 2 and

extending from the wellhead 10 to an underground section of the well bore 2. The outer part 13, the reservoir 8 and/or the casing/liner 12 are typically filled with a fluid 16, 17, 18, respectively. The fluids 16, 17, 18 are e.g. oil or gas in case of a production well or water, C0₂ or nitrogen in case of an injection well.

A first transducer device 20 is located within the casing or liner 12 for communication with a second transducer device 200 located at or near the extraction facility 9. Advantageously, the first transducer device 20 operates autonomously having internal power storage and thus needs not be powered externally.

The first transducer device 20 further can communicate with the second transducer device 200 without any wiring. To sum up, the first transducer device 20 can be operated freely in the well bore and is not cable linked to the surface.

The first transducer device 20 may additionally be a movable transducer device being moved by moving means 21, generally known to the skilled person, within the casing or liner 12 to any desired position in the casing or liner 12 or even in the reservoir 8. The first transducer device 20 includes a first transducer 30 at a backside 42 (e.g. Fig.2) of a first membrane 40, wherein the first membrane 40 is mounted at a first side 26 of a first housing 28 which faces the second transducer device 200. The first membrane 40 is in contact to the fluid 18 in the casing/liner 12.

The second transducer device 200 includes a second

transducer 202 at a backside of a second membrane 204 which is in contact to the fluid 18 in the casing/liner 12. Sound waves 27 in the fluid 18 can be generated or detected with the first transducer device or, respectively, with the second transducer device.

Fig. 2 shows another earth formation with a downhole tool 20 positioned in a horizontal portion of the casing/liner 12. The liner 12 in this embodiment only partly covers the well bore. Fig. 3 depicts a photograph of the backside 42 of the first membrane 40. The first membrane 40 of this embodiment is a metal membrane 40. The first transducer 30 is attached at the backside 42 e.g. by force-fit lamination technique, it may thus establish galvanic contact to the first membrane 40. Contact wiring 32 connects the first transducer 30 to communication electronics 60 (see Fig. 6) . The first transducer 30 is embodied as a piezo driver 30. The first membrane 40 further has holes 46 for attaching the first membrane 40 to the first housing 28 using screws or bolts or the like.

Fig. 4 shows a schematic of an excitation of the first membrane 40. The first membrane 40 is clamped at its peripheral portion 44, e.g. by fixing the membrane 40 of the embodiment of Fig. 3 to an annular membrane sealing portion 52 of the first housing 28 using screws. Excitation 48 of the membrane 40 generates at least one sound wave 27 which e.g. can propagate through the fluid 18 in the casing/liner 12.

Turning now to Fig. 5 a photograph of the backside 42 of another embodiment of the first membrane 40 is presented having a multi-layered first transducer 30. The multi- layered first transducer 30 comprises three piezo- electrically active layers 34 (see Fig. 6) . The first membrane 40 further comprises holes 46. Fig. 6 depicts a schematic of a multi-layered first

transducer 30 having four piezo-electrically active layers 34, 34a, 34b, 34c, 34d. The piezo-electrically active layers 34 are arranged on top of each other and are

connected via contact wiring 32 to e.g. communication electronics 60. Each piezo-electrically active layer 34 has a respective first pole 36, indicated with a plus-symbol, and a respective second pole 37, indicated with a minus- symbol .

The first pole 36 of the first piezo-electrically active layer 34a is directed towards the backside 42 of the first membrane 40. In other words, the side of the first piezo- electrically active layer 34a having the polarity of the first pole 36 is in contact with the backside 42 of the first membrane 40 and attached thereto, e.g. glued or by using force-fit lamination.

The second piezo-electrically active layer 34b is installed upside down, thus the second pole 37 of the layer 34b faces towards the backside 42 of the first membrane 40. The third piezo-electrically active layer 34c again has the

orientation of the first piezo-electrically active layer 34a, thus the side of the first pole 36 faces towards the backside 42 of the first membrane 40. The fourth piezo- electrically active layer 34d is oriented upside down like the second piezo-electrically active layer 34b. In general, every other piezo-electrically active layer 34, 34b, 34d is used with an upside down orientation. Upside down oriented piezo-electrically active layers 34, 34b, 34d have the advantage, that less contact wiring 32 is needed. The multi-layer piezo arrangement with two, three or more piezo-electrically active layers 34, 34a, 34b, 34c, 34d allow for a high signal intensity and a good coupling of the sound signal into the first or second membrane 40, 204 and thus into the fluid 16, 17, 18 by reducing electric load impedance of the first or second transducer 30, 202. The data signal is processed in the communication

electronics 60 such, that an excitation of the piezo driver 30 and as a consequence of the first or second membrane 40, 204 generates the at least one sound wave 27 with adequate intensity. Intensity of the sound wave 27 may be adjusted e.g. by adjusting the voltage level of the data signal or by selecting the frequency of the data signal. As an example it is advantageous, if the frequency of the data signal is set to a resonance frequency of the first or second membrane 40, 204 as will be shown.

Fig. 7 gives an overview of several vibrational modes for the first membrane 40, wherein the vibrational modes 01, 02, 11 and 21 are known per se. The first membrane 40 can be excited by the communication electronics 60 to oscillate in different vibrational modes, e.g. by excitation mode 48a, 48b, 48c, 48d. However for the purpose of having a high signal amplitude in the fluid 16, 17, 18in the well bore 2 it has been found out that using the excitation mode 48a and such vibrational mode 01 is most effective.

Fig. 8 shows a sideview of a downhole tool 100 in a

casing/liner 12 in a well bore 2 having a first membrane 40 at the first side 26 of the first housing 28. The first transducer 30 is attached to the backside 42 of the first membrane 40. The first membrane 40 is attached with its peripheral portion 44 to the annular membrane sealing portion 52 of the first housing 28. The annular membrane sealing portion 52 surrounds an opening 54 of the first housing 28, where the first transducer 30 is inserted into said opening 54. The first membrane 40 sealingly engages the annular membrane sealing portion 52 so that the fluid 16, 17, 18 is hindered to enter the opening 54 and thus to enter the first housing 28.

At a second side 29 of the downhole tool 100 a tool section 80 is scetched, wherein different downhole tools can be implemented e.g. for analysing the well bore 2 or the casing/liner 12. Generally speaking, the tool section 80 denotes usage of any kind of secondary downhole tools 110 for which communication with the extraction facility 9 is of interest. The secondary downhole tool 110 in the tool section 80 sends a data signal via data line 62 to the communication electronics 60. If applicable, the

communication electronics 60 transforms the data signal for an optimal excitation 48 of the first membrane 40 and passes the data signal via contact wiring 32 to the first transducer 30, here a multi-layered transducer 30 with four piezo-electrically active layers 34a, 34b, 34c, 34d. In this embodiment, the unit comprising the first transducer 30 and the first membrane 40 serves the purpose of

providing a communication platform for the secondary downhole tool.

Turning to Fig. 9 a first side 26 of the first housing 28 is shown in a front perspective with a round opening 54 surrounded by the annular membrane sealing portion 52. The annular membrane sealing portion 54 further has screw threads 56 for receiving screws for fixation of the first membrane 40 to the opening 54 of the first housing 28. The first membrane 40 has a diameter in a direction parallel to the surface of the first side 26 of the housing 28 which is larger than a diameter of the opening 54, so that the first membrane 40 spans the opening and engages the annular membrane sealing portion 54, thereby sealing the opening 54.

Fig. lOFig. 10 shows the relative static displacement, which is e.g. the displacement of fluid in the well bore by activation of the transducer/membrane, as a function of the piezo thickness for the four most promising membrane materials Aluminum, Stainless Steel, Titanium and/or AI₂O₃. It can be seen, that the relative static displacement increases until a maximum relative static displacement, e.g. for Aluminum in a range of 2 millimeter of thickness of a single piezo-electrically active layer 34, and a further increase of thickness does not give a higher relative static displacement. Thus if a higher displacement of fluid is wanted it has been found out in the present invention, that a multi-layered transducer 30 as able to increase displacement and thus signal intensity.

Fig. 11 substantially shows the information of Fig. 10, wherein only an activation of a membrane 40 made of

Aluminum is shown and wherein the membrane thickness is varied showing 1mm, 2mm, 3mm and 4mm of membrane thickness.

Turning to Fig. 12 an experimental setup for testing membrane and transducer properties of a first transducer device 20 and a second transducer device 200 in a test fluid 19 is shown. The first membrane 40 couples sound waves into the test fluid 19, whereas the second membrane 204 receives said sound waves and wherein both membranes 40, 204 are in contact with said test fluid 19.

Fig. 13 exemplarily shows experimental data measured with a test setup for testing membrane and transducer properties. Membranes have been excited by 30 cycles inoson electronic signal having 175 Vpp . The peak-peak pressure producible with the membranes at a distance of 1 meter was in the region of 6.2 Pa for the first membrane and 8.5 Pa for the second membrane, each at the resonance frequency of about 2300 Hz.

Fig. 14 depicts a sketched sideview of the downhole tool first transducer device 20 (or the downhole tool 100) . The elongated housing 28 has an opening 54 at a first side 26 of the housing 28, wherein the first membrane 40 is installed. The first membrane 40 is, with a first membrane side 41, in contact with the surrounding outside fluid 18. A fluid inlet 25 is situated at a second side 29 of the housing 28. The fluid inlet 25 is open to the outside fluid 18.

The first chamber 70 is subdivided into a larger subchamber 72 and a smaller subchamber 74 suited for installations of downhole equipment 30, 40. A constriction 76 of the housing 28 is situated between the larger subchamber 72 and the smaller subchamber 74.

The fluid inlet 25 comprises a channel portion 25a and opens out in an expandable second chamber 80, which is situated inside the first chamber 70. In this embodiment, the expandable second chamber 80 is situated inside the larger subchamber 72, wherein the expandable second chamber 80 may expand due to influx of outside fluid 18 to a size matching or marginally smaller than the size of the larger subchamber 72. In other words, the expandable second chamber 80 may, in an embodiment, fill out the larger subchamber 72 thereby forcing the chamber fluid 78 out of the larger subchamber 72 and into the smaller subchamber 74. The expandable second chamber 80 is encircled by the flexible divider 82, which separates the expandable second chamber 80 from the first chamber 70. The flexible divider 82 is, in this embodiment, localized to the larger backside 72 of the first chamber 70. In other words, as depicted in the embodiment above, the flexible divider 82 may fill out the larger subchamber 72 and lay against an outer wall 71 of the first chamber 70, but the first chamber 70 is constructed such, that the downhole equipment 30, 40 installed at the frontside 74 is still separated from the flexible divider 82, e.g. due to implementation of a constriction 76.

The chamber fluid collector 75, which is installed along the outer wall 71, allows all chamber fluid 78 to flow to the frontside 74, e.g. when the flexible divider 82 is pressing against the outer wall 71. The chamber fluid collector 75 has for this purpose at least one fluid channel along which the chamber fluid 78 may flow. In a preferred embodiment, the chamber fluid collector 75 is a twisted metal wire 75, where the chamber fluid 78 may flow along the fluid channel formed by the hollow space between the flexible divider 82 and the wires of the twisted metal wire 75.

Optionally, a third chamber 90 may be present in the downhole tool 20, wherein e.g. a stand-alone power supply 92 or further electronics 94 may be installed.

It will be appreciated that the features defined herein in accordance with any aspect of the present invention or in relation to any specific embodiment of the invention may be utilized, either alone or in combination with any other feature or aspect of the invention or embodiment. In particular, the present invention is intended to cover a system for providing a downhole data transfer capability for transmitting data through fluid in a well bore and a downhole tool configured to include any feature described herein in relation to the downhole data transfer system and vice versa. It will be generally appreciated that any feature disclosed herein may be an essential feature of the invention alone, even if disclosed in combination with other features, irrespective of whether disclosed in the description, the claims and/or the drawings.

It will be further appreciated that the above-described embodiments of the invention have been set forth solely by way of example and illustration of the principles thereof and that further modifications and alterations may be made therein without thereby departing from the scope of the invention . List of reference signs:

2 Well bore

4 earth formation

6 surface

8 reservoir

9 extraction facility

10 well head

12 casing/ liner

13 outer part

16 fluid

17 fluid

18 fluid

19 test fluid

20 first transducer device

21 moving means

25 fluid inlet

25a channel portion

26 first side of first housing

27 sound wave

28 first housing

29 second side of first housing

30 first transducer

32 contact wiring

34 piezo-electrically active layer

34a-d first, second, third and fourth piezo-electrically active layer

36 first pole

37 second pole

40 first membrane

41 first membrane side

42 backside of first membrane

44 peripheral portion of the membrane 46 holes or recesses

48 excitation of the membrane

48a-d excitation mode of the membrane

52 annular membrane sealing portion

54 opening

56 screw thread

60 communication electronics

62 data line

70 first chamber

71 outer wall

72 larger subchamber

74 smaller subchamber

75 chamber fluid collector

76 constriction

78 chamber fluid

80 expandable second chamber

82 flexible divider

90 optional third chamber

92 stand-alone power supply

94 further electronics

100 downhole tool

110 secondary downhole tool

200 second transducer device

202 second transducer

204 second membrane

206 second housing

Claims

What is claimed:

1. Downhole data transfer system for transmitting data through fluid in a well bore, wherein the well bore is filled with said fluid, comprising:

^■ a first transducer device being adapted to be

positioned down the well bore comprising:

• a first transducer,

• a first housing having an opening,

• first communication electronics for providing a data signal to the first transducer,

• a first membrane positioned at the opening of the first housing having a peripheral portion, wherein the first membrane is attached with its peripheral portion to the first housing,

• wherein the first transducer is attached to a

backside of the first membrane,

• wherein the first transducer excites the first

membrane in response to the data signal generated by the first communication electronics to generate at least one sound wave to propagate through said fluid,

^■ a second transducer device being adapted to be

installed at or near an access of the well bore comprising

• a second housing having an opening,

• a second transducer,

• a second membrane positioned at the opening of the second housing and having a peripheral portion, • second communication electronics connected to the second transducer for obtaining the data signal from the second transducer,

• wherein the second transducer is attached to a backside of the second membrane.

Downhole data transfer system according to any of the preceding claims,

wherein the first transducer and the second transducer are transceivers, thereby establishing bidirectional data transmission in the well bore.

Downhole data transfer system according to one of the preceding claims,

wherein the first and/or the second transducer is a piezo driver.

Dowhole data transfer system according to one of the preceding claims,

wherein the first and/or the second transducer comprises at least two piezo-electrically active layers .

Downhole data transfer system according to any one of the preceding claims,

wherein the first transducer is arranged inside the first housing and/or

wherein the second transducer is arranged inside the second housing.

Downhole data transfer system according to any of the preceding claims, wherein the first membrane and/or the second membrane is substantially planar.

Downhole data transfer system according to any of the preceding claims,

wherein the first membrane and/or the second membrane is substantially circular.

Downhole tool being adapted to be positioned down in a well bore for transmitting data through a fluid in the well bore, comprising:

^■ a transducer,

^■ a housing having an opening,

^■ a first membrane positioned at the opening of the first housing having a peripheral portion, wherein the first membrane is attached with its peripheral portion to the first housing

^■ wherein the first transducer is attached to a

backside of the first membrane.

Downhole tool according to the preceding claim,

further comprising communication electronics

connected to the transducer. Downhole tool according to the preceding claim,

wherein the first transducer excites the first membrane in response to a data signal generated by the communication electronics to generate at least one sound wave to propagate through said fluid in the well bore .

11. Downhole tool according to any of the claims 8 to 10, wherein the first transducer is a piezo-electric driver, a magneto restrictive, magnetic, electric, capacity and/or thermal driver.

12. Downhole tool according to any of the claims 8 to 11, wherein the first transducer comprises at least a first piezo-electrically active layer and a second piezo- electrically active layer.

13. Downhole tool according to the preceding claim,

wherein the at least first and second piezo- electrically active layers are arranged on top of each other .

14. Downhole tool according to the preceding claim,

wherein the at least first and second piezo- electrically active layers each comprise a respective first pole,

wherein the at least first and second piezo- electrically active layers are arranged such, that the first electrically active layer has the first pole directed towards the first membrane whereas the second piezo-electrically active layer has the first pole directed away from the first membrane,

wherein each second piezo-electrically active layer is operated electrically reversed.

15. Downhole tool according to claim 8 to 14,

wherein the first membrane has a thickness of at least 1 millimeter.

16. Downhole tool according to the preceding claim, wherein the first membrane has a thickness of below or equal to 5 millimeter. 17. Downhole tool according to any of the claims 8 to 16, wherein the first membrane is a metal membrane, in particular made of Aluminum, Stainless Steel, Titanium and/or A1203. 18. Downhole tool according to any of the claims 8 to 17, wherein the peripheral portion of the first membrane is circumferentially sealingly engaged to the housing.

19. Downhole tool according to any of the claims 8 to 18, further comprising an annular membrane sealing surface surrounding the opening of the first housing, wherein the annular membrane sealing surface is engaged circumferentially by the peripheral portion of the first membrane.

20. Downhole tool according to any of the claims 8 to 19, wherein at the peripheral portion of the first membrane holes or recesses are comprised for securely fixing the first membrane to the first housing.

21. Downhole tool according to any of the claims 8 to 20, wherein the first membrane comprises a central portion having a first thickness,

wherein the peripheral portion of the first membrane has a second thickness, and

wherein the second thickness exceeds the first thickness .

22. Downhole tool according to claims 19 and 21,

wherein the central portion has a diameter smaller than a diameter of the annular membrane sealing surface such that the central portion engages into the opening when the peripheral portion of the membrane sealingly engages the annular membrane sealing surface. 23. Downhole tool according to any of the claims 8 to 22, wherein the downhole tool operates at a data transfer working frequency which is higher than the frequency of environmental sound in the wellbore. 24. Downhole tool according to any of the claims 8 to 23, wherein excitation of the membrane by the first transducer substantially only generates first order oscillation, in particular of oscillation mode 01. 25. Downhole tool according to any of the claims 8 to 24, wherein the downhole tool operates at a working frequency which is set higher than or equal to 2 kHz.

26. Downhole tool according to any of the claims 8 to 25, wherein the downhole tool operates at a working frequency which is set lower than or equal to 40 kHz.

27. Downhole tool according to any of the claims 8 to 26, wherein the downhole tool is an autonomous downhole tool by having a stand-alone power supply. Downhole tool according to any of the claims 8 to 27, wherein an electric energy harvesting system (30, 40, 60) is composed using the transformation of sound energy collected by said first membrane (40) into electric energy by said transducer (30) to be stored in the downhole tool.