Downhole Tool

Specification

Field of the invention

The invention is related to a downhole production logging tool for use in well bores especially for the Oil and Natural Gas Industry.

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 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. Also of importance may be 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, for example, 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. In particular, said total length keeps increasing over the past decades.

Production Logging Tools (PLT) are known per se. Several suppliers of such tools exist on the market. However, these tools suffer from drawbacks. One issue is, that most of the Tools on the market can only be operated in vertical or low deviated wells comprising only a deviation of e.g. not more than 40 degrees from vertical. However, more and more well bores have highly deviated and even horizontal portions. In such conditions, the fluid in the well bore may separate to layers. Additionally or alternatively, the failure rate of such tools resulting regularly in the complete loss and/or abandonment of the tool in the well is quite high. As the costs of one tool are significant, reduction of tool losses would be greatly appreciated. It is an object of the invention to provide a Production Logging Tool which is easily serviceable, thus reducing down times or service times and increasing availability of the downhole tool. It is another object of the invention to allow for

measurement in difficult well environments such as highly deviated wells and/or at least partly open hole wells. Another object of the invention is to provide a robust and reliable PLT which despite its robustness and reliability allows for complex measurements in the well.

Still another object of the invention is to provide an integrated multi-measurement PLT, wherein in one

measurement run (downhole mission) several or even all desired measurement data can be retrieved.

Yet another aspect of the object of the invention is to improve the limitations mentioned above.

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 tool is presented herein being adapted to operate in a well bore. For example, well bores can comprise difficult environmental conditions such as a pressure up to 35 MPa or a temperature which could rise up to 400 K, or, as development of well bore exploitation continues rapidly, even more. Such a well bore can have open hole sections and/or cased hole sections, and it can comprise an angle with respect to a vector towards the centre of the earth and/or gravity. In other words, the well bore or at least sections of the well bore can have any orientation in an earth formation, including for example horizontal portions which are even preferred and drilled intentionally depending on the type of well bore. The orientation may, as a matter of fact, partly even be oriented upwards. Such an upwards oriented well bore may e.g. be the case, when a selected layer is drilled

alongside - where the layer comprises natural resources, in particular containing carbon such as oil or gas - and the selected layer is not oriented perfectly horizontally, but deviates e.g. upwards or downwards for a certain distance.

The well bore fluid can consist of different portions or "phases" of fluid such as mainly water, oil and/or gas, but also other fluid portions (phases) and also particulate matter, e.g. sand particles, can be phases of the well bore fluid. It is particularly desired to determine the

fractions of these phases in the well bore fluid and in the following, a downhole tool is descripted being able to determine said phases and in preferred embodiments may even achieve further tasks in a single, combined downhole tool.

The downhole tool comprises an elongated housing divided into several sections. Each section comprises a tube portion to be coupled to a coupling.

Each tube portion comprises a central portion inside the tube portion which allows for installation of downhole tool equipment. The housing as a whole and/or the tube portion of the downhole tool can thus be advantageously designed in an essentially circumferentially closed manner, which is, like a tube. In a particularly preferred embodiment, the tube portion consists of an essentially circumferentially closed tube-like casing with an open frontside and an open back end encompassing the inner channel portion, wherein in the inner channel portion a hollow space is situated. In a specifically advanced embodiment, the tube portion is designed as a carrier for installation of downhole tool equipment inside the tube portion. However, a tube portion does not necessarily need to have such downhole tool equipment installed inside, as it may also have the purpose to define a spacing between installed downhole tool equipment. An example for this are sensors, which could disturb each other if installed too close to each other.

Even more preferred, the tube portions are exchangeable to each other, e.g. are identical to each other and/or only distinguish with respect to a length of the tube portion.

A Downhole tool (20) being adapted to operate in a well bore (2), comprises a segmented housing. The segmented housing has at least a first and a second tube segment forming part of the segmented housing. Thus, the first and the second tube segment forms part of the outer surface of the segmented housing.

The downhole tool further comprises a first coupling arranged between the first and the second tube segment. The first coupling is designed for coupling the first tube segment with the second tube segment. The coupling at least partly forms part of the segmented housing. Thus, part of the outer surface of the segmented housing is formed by the coupling arranged between the first and the second tube segment .

The first coupling may comprise longitudinal extensions for receiving the first and the second tube segment. Thus, said longitudinal extensions are situated on a first and a second side of the coupling. The longitudinal extensions access, when mounted, into the first tube segment on the first side of the first coupling and into the second tube segment on the second side of the first coupling,

respectively. Therefore, on each side of the coupling a radial surface of the longitudinal extensions is in contact with an inner surface of the first or second tube segment, respectively. Such that, for example, when assembling the downhole tool, one of the tube sections is slidably mounted over - which is around - the longitudinal extension of the coupling, so that the longitudinal extension slides into to the inner part of the tube section. Thereafter, the tube section can be fixedly mounted to the coupling via radial mounting elements - such as screws - inserted from a radial direction through the tube section - which is e.g. through openings such as bore holes - and into the longitudinal extension of the coupling.

The first coupling may therefore comprise radial mounting members on a radial surface of the longitudinal extensions for receiving mounting elements and thus for fixation of the tube section at the coupling. Such mounting members can be adapted for receiving a screw, for example.

The first coupling may further comprise a respective sealing member situated on the radial surface of the longitudinal extensions and outwardly with respect to the radial mounting members. In other words, on each

longitudinal extension, this is on two sides of the

coupling, the sealing member can be installed, e.g. in a groove for receiving the sealing member, wherein the inner channel portion of the tube element is sealed against the surrounding by use of the sealing member of the coupling. The first coupling comprises an outer diameter. The outer diameter of the first coupling advantageously equals an outer diameter of the adjacent tube segment. Herein, equal means comprising more or less the same diameter. To equal can include manufacturing tolerances.

In a particularly preferred embodiment the first coupling comprises a sensor device for detection of a fluid property of the well bore fluid. The sensor device can, by way of example, comprise at least one sound wave generator, such as an ultrasound sound wave generator. The sound wave generator can be arranged at an outer side of the coupling, such that the sound wave generator is directed outwardly with respect to the downhole tool. In other words, at the outer side of the coupling, e.g. in a sensor device hutch or sensor device recession of the coupling, the sensor device is arranged and oriented to direct outwards.

Particularly preferred, the sensor device has a preferred measurement direction which is radially outwards, or even perpendicular to a downhole tool main elongation axis.

In case an ultrasound wave generator is used, for example, the ultrasound sensor can emit ultrasound waves into the well bore fluid when flowing along the downhole tool, which is into the sideflow. In other words, the ultrasound wave generator couples waves into the sideflow well bore fluid. Particularly preferred, the ultrasound sensor is arranged at the external side of the housing and at the outer side of the coupling, wherein the ultrasound sensor is directed radially away from the central part of the downhole tool.

In other words, said waves - ultrasound waves - are coupled into the well bore fluid and propagate through the well bore fluid in a direction transverse to the flow direction of the sideflow fluid alongside the downhole tool.

Particularly preferred, several sensors are grouped as the sensor device. Thus, e.g. several sound wave generators can be arranged around the circumference of the coupling in order to improve measurement results with respect to the circular angle around the downhole tool. By way of example, a property to be measured by the sensor device can be fluid velocity, downhole tool velocity, fluid compounding, amount of particles in the wellbore fluid and/or crossflows, which may for example occur when cracks in the casing or liner or tubing are present.

With the ultrasound sensor "scanning" the well bore fluid transversely - e.g. from the wellbore tool to the

surrounding casing or liner or production tubing and reflected by that back to the ultrasound sensor - a

propagation time for the sound wave(s) can be determined and thus the density of the well bore fluid can be

determined. As, for example, water, oil and gas comprise different densities, a total amount of the portion of water, oil and/or gas can be obtained.

The downhole tool advantageously is very reliable and robust as the proposed measurement sensors are minimally or not at all invasive in the well bore fluid and also can tolerate a high amount of suspended solid (particulate matter), which is often present in well bores. In a particularly preferred embodiment, the downhole tool comprises only static components (i.e. which do not move or have moving parts) . The downhole tool can, in another embodiment, comprise a second coupling for fixedly connecting the second tube segment with a third tube segment. The second coupling can be identical to the first coupling. The second coupling can comprise a second sensor device for detection of the same fluid property and/or a second fluid property of the well bore fluid. For this, the second sensor device can for example comprise one or several resistive sensor (s). In case of several resistive sensors the sensors can be arranged around the circumference of the coupling directing outwards in direction of the wellbore fluid around the downhole tool, which is, the sideflow.

In a particularly preferred embodiment, the tube segments are interchangeable to each other. By way of example, thus an installation of the sensor couplings is possible at any position between two tube segments. For some measurement systems, such as for the gamma ray sensor - which is described later - also installations for sensor and/or sensor related electronics are to be placed inside the tube elements. In this case, the particular coupling is to be installed with a selected tube element. However, it is preferred, that each tube segment comprises an open front side and an open rear end, resulting in a tube-like shape.

In this case, it is preferred that a front end coupling is used in the downhole tool to be coupled to the first tube segment. The front end coupling can on the one side be identical to the other couplings, thus having a

longitudinal extension to extend into the first tube element when mounted thereto. However, it is advantageously to also use the front side of the front end coupling, e.g. for installation of a further sensor device.

Using the further sensor device of the front end coupling detection of the same fluid property and/or a further fluid property of the well bore fluid is possible.

Preferably, the further sensor device comprises at least two sound wave generators. The at least two sensor devices may have a measurement orientation, wherein the measurement orientation is essentially along the downhole tool main elongation direction, which is the longitudinal axis of the downhole tool. However, it has proven to be advantageously, if the at least two sensor devices are inclined with respect to the longitudinal axis of the downhole tool.

At least one of the sensor device of the first coupling, the second sensor device of the second coupling or the further sensor device of the front end coupling can

comprise at least one sound wave generator, such as an ultrasound sound wave generator.

The sensor device can comprise several sensors, such as ultrasound wave generators, being at least partly

distributed over the outer surface of the first coupling along the longitudinal axis of the downhole tool. By distributing the sensors over the outer surface and along the longitudinal axis of the downhole tool it is e.g. possible to measure the same amount of fluid at least twice. This can allow for measurement of fluid velocity. On the other hand, this can also be used for redundant

measurement of the fluid phases for increasing measurement accuracy.

The at least one sound wave generator is advantageously situated at the outside of the housing. In other words, the at least one sound wave generator being installed at the outer side of the coupling is also - when the downhole tool is assembled - installed at the outside of the housing, so that it is in direct contact with the sideflow around the well bore tool when deployed in a well bore. The at least one sound wave generator device can preferably be designed as a transceiving ultrasound sensor being able to transmit and receive ultrasound sonic waves for

releasing ultrasound sonic waves into the well bore

surrounding the downhole tool for registering said property of the well bore fluid.

In a further preferred embodiment, the first coupling comprises at least six ultrasound sound wave generators. The first coupling may comprise, for example also up to twelve ultrasound sound wave generators. For reasons of radial distribution of acquisition coverage, usage of twelve ultrasound sound wave generators distributed

radially around the outer side - e.g. in sensor recessions - is particularly preferred. In other words, the ultrasound sound wave generators are being distributed around a circumference of the housing of the downhole tool. Thus, spatial measurement of the fluid phases is improved and/or measurement accuracy is increased, e.g. for measurement of the sideflow fluid velocity or property.

The ultrasound sensors distributed at least partly over the longitudinal extension of the downhole tool can

advantageously be interlinked with a measurement timing system. If such a measurement timing system is utilized, a fluid flow velocity of the well bore fluid flow relative to the downhole tool can be taken into account so that, for example, the same amount of well bore fluid can be measured with the distributed ultrasound sensors.

An electronics compartment can preferably be accommodated in one of the tube sections of the downhole tool.

Further, also an electromagnetic communication transceiver for transmitting gathered measurement data to a secondary communication unit can be housed in the downhole tool. Additionally, a gamma ray tube segment, wherein a gamma ray sensor and/or a resistive sensor are accommodated in the gamma ray tube segment, can be comprised.

It is particularly preferred, that also a temperature sensor coupling for coupling two tube segments is installed in the downhole tool. For example, the temperature sensor coupling can be used to couple the third tube segment and a fourth tube segment. The temperature sensor coupling comprises advantageously a temperature sensor arranged at the outer side of the temperature sensor coupling. Also, a pressure sensor is advantageously comprised in the downhole tool.

Preferably, a tool velocity sensor for determining the velocity of the downhole tool in the well bore is comprised in the downhole tool.

Further preferably, the downhole tool can be designed as an autonomous downhole tool. Such an autonomous downhole tool can comprise a power tube, wherein a power storage for providing energy to the downhole tool equipment and/or to sensors is housed in the power tube.

The power tube can be made linkable to the adjacent tube segment by way of a further coupling.

Additionally, a versatile tube segment for arranging measurement devices inside the housing or for further purposes can be linked or coupled to the other segments by way of the further coupling. In other words, the downhole tool is variable and/or interchangeable with respect to its segments and/or can be enlarged by linkage of further tube segments and further couplings. Thus, also a supply housing segment for arranging

electronics and/or supply fluids and/or an energy storage inside the downhole tool can be linked to the other

segments and thus be made part of the downhole tool. It is particularly preferred, that each coupling and each tube segment forms part of the housing of the downhole tool, so that in the end, the total housing of the downhole tool is made up by the tube segments and the couplings.

In a preferred embodiment of the downhole tool a fluid flow blocker device arranged at the outer side of the downhole tool is comprised in one of the tubing elements for

blocking the well bore fluid. The fluid flow blocker device can be designed e.g. as a bellow or an expandable sealing element which can be expanded or extended e.g. by pumping a liquid or gaseous bellow fluid beneath it. However, a mechanical expansion or extension mechanism can also be implemented. The fluid flow blocker device seals at least a section of the well bore surrounding the downhole tool, thereby preventing well bore fluid from bypassing the downhole tool.

The multifunctional downhole tool, for example, collects data in the well bore and/or the reservoir or which

operates other functions particularly for sustaining the well bore. The downhole tool can also comprise the

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

For determining the velocity of the downhole tool in the well bore the downhole tool can comprise a tool velocity sensor. The tool velocity sensor e.g. can scan the inner surface of the well bore and/or of the liner/casing. In another embodiment the downhole tool is driven by a driving unit, e.g. by a tractor, whereas the tool velocity sensor can determine the speed of the driving unit. The downhole tool is advantageously designed as an

autonomous downhole tool. As such, the downhole tool has a communication device - e.g. installed in a communication tube section or an electronics tube section - for

exchanging information with a secondary communication unit, such as a surface platform or station. The communication device of the downhole tool can comprise an electromagnetic communication transceiver for transmitting gathered

measurement data to the secondary communication unit.

A further idea of the present invention is a coupling unit suited for coupling tube segments of a downhole tool. The coupling unit comprises longitudinal extensions. The longitudinal extensions are situated on a first and a second side of the coupling. The longitudinal extensions are designed for receiving a first and a second tube segment, in particular for sealingly receiving the first and the second tube segment . The longitudinal extensions of the coupling unit access, when mounted or being mounted, into the first tube segment on the first side of the coupling unit and into the second tube segment on the second side of the coupling unit, respectively. In other words, so that a radial surface of the longitudinal extensions is in contact with an inner surface of the first and second tube segment.

The coupling unit is designed to partly form part of a segmented housing of a downhole tool when mounted thereto.

Preferably, the coupling unit comprises a sensor device for detection of a fluid property of the well bore fluid. The proposed downhole tool thus allows for a comprehensive analysis of the production and/or injection well which may include well and near well bore characteristics in flowing and static well conditions.

The proposed downhole tool further lacks moving parts, but is able to measure flow rate, tool velocity, can have an obstacle identification and/or fluid type. It can measure its position as well as the fluid position, including fluid bubble, slug and segregated flow, and this even as a function of the geological position in open hole condition and/or its position in the cased or lined well. The proposed downhole tool further comprises sensors to be used to investigate the down-hole tool equipment such as valves, pipe, perforated pipe, pipe connections, in situ sensors, packers, side pocket mandrels and its components. The proposed downhole tool can be permanently installed in the well for long term well continuous or intermittent data collection. The tool can also be run on wire or pipe.

The proposed downhole tool is able to combine the sensor information and, if applicable, performs calculations allowing for real time analysis in the tool and/or at surface .

Particularly preferred, the proposed downhole tool thus comprises at least one of the following sensors:

- a pressure sensor reading fluid pressure,

- a temperature sensor reading fluid temperature, - a sound wave or mic sensor which is able to ^listen' to the well noise, which can be used for flow and/or leak detection

- a gamma ray sensor used to read gamma radiation

allowing for formation type identification as well as for scale identification when the scale is radioactive

- a magnetic flux sensor used to locate pipe connections

- a radial impedance sensor which distinguishes between water and hydrocarbons and its position in radial direction

- a radial ultrasound sensor which provides hole

dimension, acoustic energy loss indicating the fluid type and its radial distribution, as well as the tool velocity

- forward sensors, measuring obstacles, hole diameter reduction or increase, fluid velocity and/or tool velocity

However, it is particularly preferred, that most or even all of the before mentioned sensors are installed in the downhole tool.

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 tool 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 sideview of a part of a downhole tool with a coupling;

Fig. 4 a sectional drawing of a part of a downhole tool with a coupling;

Fig. 5 detailed sectional drawing of a coupling with

part of a tube element;

Fig. 6 sectional drawing through a coupling;

Fig. 7 sectional drawing of another coupling for a

downhole tool;

Fig. 8 sideview of another embodiment of a downhole tool showing two tube elements and two couplings;

Fig. 9 sectional drawing of a downhole tool with two

couplings ;

Fig. 10 sectional drawing of a further embodiment of a coupling;

Fig. 11 sectional drawing of another part of a downhole tool having couplings;

Fig. 12 sideview of a part of a downhole tool with a

front end coupling;

Fig. 13 sectional drawing of a part of the downhole tool with front end coupling;

Fig. 14 sectional drawing of the front end coupling;

Fig. 15 sectional drawing of another embodiment of a

coupling for a downhole tool;

Fig. 16 sectional drawing of yet another downhole tool with couplings;

Fig. 17 section drawing of another tube element for a

downhole tool with a coupling; Fig. 18 sideview of a downhole tool;

Fig. 19 sideview of a rear part of a downhole tool to be continued in Fig. 20;

Fig. 20 sideview of a front part of a downhole tool

continued in Fig. 19;

Fig. 21 sectional drawing of a rear part of a downhole tool to be continued in Fig. 22;

Fig. 22 sectional drawing of a front part of a downhole tool continued in Fig. 21;

Fig. 23 front perspective view on the front end coupling; Fig. 24 sectional drawing D-D;

Fig. 25 sectional drawing F-F;

Fig. 26 sectional drawing G-G;

Fig. 27 sectional drawing H-H.

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 elongated 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 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, CO2 or nitrogen in case of an injection well. A downhole tool 20 is located within the casing or liner 12. Advantageously, the downhole tool 20 operates

autonomously having internal power storage 92 (see e.g. Fig. 2) and thus needs not be powered or wired externally. To sum up, the downhole tool 20 can be operated quite freely in the well bore 2 and particularly needs not to be cable linked to the surface. The downhole tool 20 may additionally be a movable downhole tool 20 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. Fig. 2 shows another earth formation with a down-hole tool 20 positioned in a horizontal portion of the casing/liner 12. The liner 12 in this embodiment only partly covers the well bore 2. The down-hole tool 20 comprises a power supply 92.

Fig. 3 shows a first tube element or tube segment 110 together with a first coupling 30 of an elongated housing 28 of the downhole tool 20. The outside of the first tube segment 110 together with a part of the outside of the first coupling 30 forms part of the housing 28 of the downhole tool 20.

Recesses 41 for accommodation of sensors 50 (see e.g. Fig. 4) are provided in said first coupling 30. In the depicted embodiment of Fig. 3, a total of 24 recesses 41 are

provided in the first coupling 30 for installation of sensors 50 such as ultrasound sensors 52 or resistive sensors 54. Thus, in the depicted embodiment, a sensor double ring 51 is provided.

The first coupling 30 further provides two sealing elements 43 which circumfere an inner diameter of the first coupling 30. In other words, the radial surface 44 of the

longitudinal extension 46 comprises said two sealing elements 43. The first coupling 30 further comprises an electric section connector 48 for providing power and/or data link with the respective second 120 or further tube segment 130.

A flange 49 for the electric connector 48 is provided at the top end of the longitudinal extension 46.

The diameter of the housing 28 can be chosen e.g. with respect to the well bore diameter the downhole tool shall be used for, and may comprise in an example an outer diameter of 73mm and an inner diameter of 55 mm, resulting in a housing thickness of about 18 mm. However, the outer diameter of the housing 28 lies preferably in a range in between 50 mm to 90 mm.

The housing 28 - comprising for example the tube segments 110, 120, 130 and the intermediary couplings 30, 31 - comprises a circumferentially closed - or at least

essentially circumferentially closed - tube-like shape, where the ultrasound sensors 50 are arranged at the very surface, which is the outer side 112 of the coupling, for measuring the property of the wellbore fluid 16, 17, 18. The first tube segment 110 provides connection means 114 for connecting the first tube segment 110 with the first coupling 30. The connection means 114 may be holes or recesses 114 for receiving a fixation means 116 such as a screw or a bolt or the like. The fixation means 116 can then be fixated at or in the first coupling 30. For this purpose, the first coupling 30 also provides connection means 36 for receiving fixation means 116 for fixedly connecting one of the tube elements 110, 120, 130 to the first coupling 30.

The first tube element 110 provides, on its other end 118, further connection means 115 for connection of a second coupling 31.

Fig. 4 depicts a sectional drawing of the first tube segment 110 together with the first coupling 30 along the line depicted with A-A in Fig. 3. Same features are

depicted with same reference signs. The first tube element 110 has an inner channel portion 34 surrounded by the internal side 32 of said housing 28. The first tube segment 110 is coupled with the fixation means 116 to the first coupling 30. The first coupling 30 comprises sensor elements 50, such as ultrasound sensors 52.

Electronics 119, such as sensor electronics, can be housed inside the first tube section 110 and be sealed inside. The electrical connector 48 is connectable with a second electrical connector 48a, so that the tube sections of the downhole tool 20 advantageously can be interchangeable. An electronics compartment 80, 119 provides storage room for installation of electronics e.g. to determine said phases of the wellbore fluid 16, 17, 18 out of the

measurement data of the sensors 50, 51, 52, 54, 56, 58 installed. In other words, all necessary data processing and handling can preferably be done with the downhole tool 20 itself. If the downhole tool 20 further provides a data transmission device, e.g. in the electronics compartment 80, 119, it is then possible to transmit measurement results to the surface, wherein no raw data needs to be transmitted and thus bandwidth of transmission can be spared. This is even more important, as data transmission rates from an elongated wellbore 2 having a length of several kilometres may be limited.

Fig. 5 depicts a further sectional drawing of the first coupling 30 along with a part of the first tube segment 110. The orientation of the sectional drawing is depicted by the line B-B in Fig. 4. Same features comprise the same reference numerals.

By a test channel 113 the sealing elements 43 can be tested during assembly of the downhole tool 20. For example, the test channel 113 can be supplied with pressure during assembling of the first tube section 110 to the first coupling, thereby revealing malfunction of one of the sealing elements 43. The two sealing elements 43 are provided on each side for sake of redundant provision of sealing capability, thereby securing, that the inner portion of the tube sections 110, 120, 130 are sealed against the well bore fluid 16, 17, 18. Fig. 6 shows another sectional drawing of a downhole tool 20, wherein, for example, the sectional drawing is taken along the line depicted as E-E in Fig. 22. Several

ultrasound wave sensors 52 are oriented circular to measure the property or properties of the well bore fluid 16, 17, 18. Electrical lines from the connector 48 are depicted in the center part of the downhole tool 20. It is preferred to have each two sensors 50 in a right angle (90°) to each other for improvement of measurement results.

Additional sensors provide further informations out of the wellbore 2. The outer ultrasound sensors 52 being installed at the outside of the housing situated in the first

coupling 30 to measure e.g. the tools' movement velocity in the wellbore 2 in relation to the casing/liner 12 or the open hole wall. In the present embodiment, a total of 24 ultrasound sensors 52 are used arranged in two measurement rings 51. Fig. 7 shows a second coupling 31, which can also be coupled to the to-be-assembled downhole tool 20 depending on the mission profile of the downhole mission. A

temperature sensor 56 is provided in the second coupling 31, which is connected via a cable 56a to a central cable pack 48b. Thus, the signal from the temperature sensor 56 - or of any sensor element 50 - can be evaluated within the downhole tool 20 but, if applicable, apart from the sensor location . Fig. 8 depicts two tube sections 130, 140 of the downhole tool 20 being coupled by the third coupling 33. The third tube section 130 and the fourth tube section 140 may comprise the same dimensions, however a differing length may be preferred depending on the type of tube sections to be installed in the downhole tool 20. Fig. 9 shows another cross sectional drawing of a part of the downhole tool 20, for example along the line depicted as A-A in Fig. 8. Same features are labelled with same reference numerals. A pressure sensor 55 is provided centrally. Also, a gamma ray sensor 58 is situated in the third tube section 130. The third tube section 130 can therefore be referred to as the gamma ray sensor tube 130.

Measurement of the gamma ray spectrum is possible with the gamma ray sensor 58. By implementing said gamma ray sensor 58 into one combined and/or modular downhole tool 20 parallel measurement of several characteristics of the well bore fluid 16, 17, 17 and/or the wellbore 2 and/or the earth formation 4 is possible with only a single tool. The fourth tube section 140 provides an inner space suited for installation of further electronics 149, wherefore the fourth tube section 140 can be referred to as electronics tube 140. The pressure in the wellbore fluid 16, 17, 18 of the wellbore 2 is measurable using the pressure sensor 55, which is comprised in the present embodiment of Fig. 9 as part of the second coupling 31. Also the temperature in the wellbore fluid 16, 17, 18 is measurable by way of the temperature sensor 56. In the present embodiment, the installed temperature sensor 56 is installed in the second coupling 31. Fig. 10 shows a further cross-sectional view, for example along the line B-B of Fig. 9. A gamma ray sensor 58 is installed inside the gamma ray sensor tube 130. The second coupling 31 comprises the pressure sensor 55 and the temperature sensor 56.

Fig. 11 shows a further cross-sectional view of another embodiment of the downhole tool 20. An elongated gamma ray sensor 58 is installed in this embodiment in the gamma ray sensor tube 130. The second coupling 31 comprises the pressure sensor 55. Each longitudinal extension 46 of the second coupling 31 and the third coupling 33 can be tested by the test channel 113 of the third or fourth tube section 130, 140.

Referring to Fig. 12, the housing 28 of the downhole tool 20 comprises a frontside 38, also referred to as "nose", where a front end coupling 39 is coupled to the first tube segment 110. The frontside 38 of the front end coupling 39 can be designed so as to minimize flow resistance.

Front ultrasound wave sensors 52 are installed at the frontside 39 of the front end coupling 39 to measure the forward-directed fluid flow in the well bore.

Referring to Fig. 13, the cross-sectional view along line A-A of Fig. 12 is shown. Same features are depicted with same reference signs. Electronics 119 is installed in the first tube element 110 in communication with the front ultrasound sensors 52. Collected and/or derived data and/or power can be provided by way of the electric section connector 48a.

Referring to Fig. 14, a cross-sectional view along the line B-B of Fig. 13 is presented. Same features are depicted with same reference signs.

Referring to Fig. 15 another cross-sectional view of a first coupling 30 is presented.

Referring to Fig. 16, yet another cross-sectional view of a part of a downhole tool 20 is presented. A first coupling 30 is coupled to a first tube element 110 and fixated via fixation elements 116. Electronics 80, 119 are provided in the first tube element 110. Also, a stand-alone power supply 92, e.g. accumulators, are provided in the first tube element 110. The stand-alone power supply 92 can provide enough energy to feed the total electronics of the downhole tool 20 during its downhole mission. The stand- alone power supply 92 can be divided into several power supply chambers 94, 94a, 94b.

Turning to Fig. 17, one more cross-sectional view of a part of a downhole tool 20 is depicted. The first coupling 30 is coupled to the first tube element 110 and fixated via fixation elements 116. In the inner portion of the first tube element 110 a mounting element or mounting ring 66, sealed by a further sealing element 64, is provided for mounting the electronics 119 thereto.

Fig. 18 shows a long shot of an embodiment of the whole downhole tool 20 comprising a front end coupling 38, a first tube element 110, a first coupling 30, a second tube element 120, a second coupling 31, a third tube element 130, a third coupling 33, a fourth tube element 140, a fourth coupling 35, a fifth tube element 150, a fifth coupling 37, a sixth tube element 160, a sixth coupling 40, a seventh tube element 170 and an end coupling 42. The downhole tool 20 comprises several ultrasonic wave sensors 52, in the present embodiment five at the front end

coupling 38 as well as 24 at the first coupling 30. Further resistivity sensors 54, 24 of them, are comprised in the second coupling 31. With resistivity sensors 54 the

resistivity of the wellbore fluid 16, 17, 18 can be

measured, which also can provide information about the composition of the fluid.

The third coupling 33 comprises a temperature sensor 56 and a pressure sensor 55. Due to the vast length of the tool the drawing of Fig. 18 is compressed with respect to the length .

Fig. 19 and 20 show another embodiment of the downhole tool 20, still compressed with respect to the length but less than compared to Fig. 18. Same features are depicted with same reference signs. However, the versatility of the presented modular downhole tool 20 becomes visible most when viewing Figs. 21 and 22, which show a cross-sectional view of the whole downhole tool 20, e.g. along the line depicted as A-A in Figs. 19 and 20. All tube elements 110, 120, 130, 140, 150, 160, 170 are exchangeably

interconnected with each other by the universal couplings 30, 31, 33, 35, 37, 38, 40, 42 in combination with the universal electrical connectors 48, 48a. When applicable, the downhole tool 20 can be moved in the well bore 2 by means of a tractor, whereas a tractor connector 95 is provided in the end coupling 42. Figs. 23, 24, 25, 26 and 27 show cross-sectional views of the downhole tool 20 shown in Figs. 21 and 22 along the respective views C, D-D, F-F, G-G, H-H as given in Figs. 21 and 22. Fig. 23 is a top view on the front surface 39 of the front end coupling 38, showing the arrangement of five sensors 50, preferably ultrasound wave sensors 52. However, it would be possible to also implement resistivity sensors 54 or other sensor elements into the front end coupling.

Fig. 24 shows the cross-sectional view along line D-D and therein the fixation of electronics 119 in the downhole tool 20. Central cable pack 48b is provided in the inner space of the third tube element 130.

Turning to Fig. 25 by cross-sectional view along line F-F the fixation of the tube elements 110, 120, 130, 140, 150, 160, 170 to the couplings 30, 31, 33, 35, 37, 38, 40, 42 is made visible.

Fig. 26 shows a cross-sectionally view along line G-G through the power supply 92. Finally, Fig. 27 shows a cross-sectional view through the third coupling 33

comprising the temperature sensor 56 as well as the

pressure sensor 55. To summarize, a downhole tool 20 which allows for

determination of several fluid properties of the well bore fluid 16, 17, 18 in the wellbore fluid is presented. The downhole tool 20 makes use of its versatility and

modularity to determine the wellbore properties, e.g. by measuring the "time of flight" of an ultrasound wave travelling through said wellbore fluid 17 inside the downhole tool 20. It may also be lined out, that the presented downhole tool 20 measures the depicted properties of the fluid and/or the earth formation with non-moving parts. Also, in earlier attempts to measure downhole conditions, initially flow measurements are undertaken and then correlated against a reference log which contains the formation properties of the well when it was drilled and initially completed, in order to understand the condition of the well at the present time. However the measurement of only the fluid flow is not sufficient to describe the condition of the flowing well at the present time, because the properties of the exposed formations change with time, and because the condition of the installed well equipment changes with time.

The formation may change with time as a result of for example the drop-out of condensate, the formation of organic or non-organic scale, the movement of fines such as clay particles or the formation of asphaltene deposits, etc. Also the condition of installed wellbore equipment changes with time as a result of manipulation of sleeves & valves, corrosion, forming of scales or deformation of equipment under thermally or geologically induced stress.

Logging tools may exist on the market, that can measure the changed condition of the formation or the condition of the wellbore equipment, but these tools do not measure fluid flow rates or fluid properties in the wellbore at the same time, as presented with the downhole tool 20 according to the invention. Therefore, they will require both more time and expense to collect data (multiple logging runs) and also provide a less integral picture of the flowing well since conditions of particularly wellbore equipment can change between a static well and a flowing well. The present invention described above in detail addresses the shortcomings of existing production logging tools by measuring both the fluid flow rates and fluid composition, but also by measuring the condition of the

formation/wellbore interface and of the installed well equipment. By combining these measurements an integral view of the current downhole condition of the well is obtained which is far more capable of explaining the engineer the flow behaviour of the reservoir and the well. Therefore, with the present invention, for example a movement of the wellbore, of the earth formation or the like can be made visible. A response of the carrier - e.g. acoustical - can give clues about the condition of the well, e.g. revealing the stress factor in the reservoir.

Moreover, sediment can be made visible, as changes in the flow regime of the well bore fluid can be measured. Thus, a more precise determination of the exploitable amount of natural resource is possible. Even pipe leakings are detectable . As the downhole tool according to the invention can stay downhole in static well condition as well as in non-static well condition, informations from the well can be retrieved in both conditions and can be interlinked. This may even allow for a determination of information about which part of the earth formation, where the well bore is drilled through or into, is actually producing. It allows for step rate tests and for observing the influence of the drawdown pressure on the exploitable delivery rate. In other words, when the downhole tool comprises the first sensor device and further sensor devices for measuring fluid properties such as fluid velocity or fluid

composition as well as conditions of the wellbore, such as by means of pressure or temperature sensors, an interlinked information pattern can be generated. The information pattern can then be analysed e.g. by means of an evaluation system to retrieve e.g. information about the status of the wellbore as depicted above. To put it in a nutshell: By analysing the combined measurement data retrieved from the several measurement devices an integral view of the current downhole condition of the well is obtained.

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 downhole tool configured to include any feature described herein. 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

16 wellbore fluid

17 wellbore fluid, sideflow

18 fluid flow in the annulus

20 downhole tool

21 moving means

28 housing

30 first coupling

31 second coupling

32 internal side of housing

33 third coupling

34 inner channel portion

35 fourth coupling

36 connection means

37 fifth coupling

38 front end

39 front end coupling

40 sixth coupling

41 recess

42 seventh coupling / end coupling

43 sealing element

44 radial surface

46 longitudinal extension

48 electric connector

48a second electric connector 48b central cable pack

49 flange for electric connector

50 sensor

51 sensor double ring

52 ultrasound sensor

54 resistivity sensor

55 pressure sensor

56 temperature sensor

58 gamma ray sensor

62 screw

64 further sealing element

66 mounting ring, e.g. for electronics

80 Electronics

92 stand-alone power supply

95 tractor connector

110 first tube segment or element

112 outer side of coupling

113 test channel

114 connection means

115 further connection means

116 fixation means

118 other end of first tube section

119 electronics

120 second tube segment of element

130 third tube segment

140 fourth tube segment

149 further electronics

150 fifth tube segment

160 sixth tube section

170 seventh tube section