Downhole Tool for Detecting Pipe Leaks

Abstract

A tool for detecting leaks in downhole pipe comprises wave generator devices (30, 40) for coupling ultrasound waves into the surrounding fluid. The waves are scattered, e.g. reflected, at inhomogeneities (60) in the fluid, for example particles, scatterers and/or water in oil, thereby generating reflections (70) which are measured with a receiver device (25) and evaluated for determining the positions of the inhomogeneities in the fluid in order to detect e.g. crossflows (15) generated by leakage (65).

Claims

1. Downhole tool (20) for investigating an outside fluid flow being adapted to operate in a well bore (2), comprising: a housing (28) surrounded by an outside fluid (16, 17, 18), at least a first wave generator device (30), preferably comprising a directional sound generator, for coupling waves (32) into the surrounding outside fluid (16, 17, 18), wherein the waves (32) are scattered, e.g. reflected, at inhomogeneities (60) in the outside fluid (16, 17, 18), for example particles, scatterers and/or water in oil, thereby generating reflections (70), a receiver device (25) for receiving said reflections (70), an evaluation device (27) for determining first positions of said inhomogeneities (60) in the outside fluid (16, 17, 18) by evaluating said reflections (70), wherein the evaluation device (27) is adapted to determine the outside fluid flow.

2. Downhole tool (20) according to the preceding claim, wherein the evaluation device (27) comprises a trigger for capturing an event in time of coupling said waves (32) into said outside fluid (16, 17, 18).

3. Downhole tool (20) according to any of the preceding claims, wherein the evaluation device (27) determines the first positions of said inhomogeneities (60) by measuring an elapsed time between coupling said waves (32) into the surrounding outside fluid (16, 17, 18) using said wave generator device (30) and receiving said reflections (70) using said receiver device (25).

4. Downhole tool (20) according to the preceding claim, wherein the evaluation device further determines second positions of said inhomogeneities (60) by again measuring an elapsed time between coupling second waves (32) into the surrounding outside fluid (16, 17, 18) and receiving second reflections (70), wherein the evaluation device (27) further evaluates position changes of said inhomogeneities (60), preferably evaluates a position and/or velocity pattern (62) of the inhomogeneities (60), by comparing said first positions with said second positions.

5. Downhole tool (20) according to any of the preceding claims, wherein the evaluation device is further designed to calculate an outside fluid flow velocity (14, 15) and/or a crossflow in the outside fluid (15) and/or a fluid amount entering the well bore (2) or escaping out of the well bore (2) through an undesired opening or crack (65) in the well bore (2).

6. Downhole tool (20) according to any of the preceding claims, wherein the evaluation device (27) is designed to detect a variation of the position and/or velocity pattern (62) thereby identifying translationally movement of the outside fluid (16, 17, 18) and/or alterations of the structure of the well bore (2) and/or a direction depending fluid flow (14, 15).

7. Downhole tool (20) according to any of the preceding claims, wherein a correlation coefficient between the first position and the second position is determined, e.g. a cross autocorrelation function.

8. Downhole tool (20) according to any of the preceding claims, wherein the first wave generator device (30) comprises a directional sound generator, further comprising a second wave generator device (40) having a directional sound generator, the second wave generator device (40) comprising a beam angle with respect to the first wave generator device (30).

9. Downhole tool (20) according to the preceding claim, wherein the receiver device (25) is also adapted to receive reflections (70) from waves (42) from the second wave generator device (40), wherein the evaluation device (27) is adapted to also evaluate a second velocity and position pattern (62) derived from the second positions and/or a difference between the first and the second positions.

10. Downhole tool (20) according to any of the preceding claims, further comprising a third wave generator device (50) having a directional sound generator for coupling waves into the outside fluid (16, 17, 18), the third wave generator device (50) comprising a predefined beam angle with respect to the first wave generator device (30) and a predefined beam angle to the second wave generator device (40).

11. Downhole tool (20) according to claim 9 or 10, wherein the beam direction of the wave generator device (30) and/or of the second wave generator device (40) and/or of the third wave generator device (50) is adjustable thereby allowing to adjust the beam angle in between the wave generator devices (30, 40, 50).

12. Downhole tool (20) according to one of the claim 9, 10 or 11, wherein the wave generator devices (30, 40, 50) are arranged in a common plane at one side of the downhole tool (20).

13. Downhole tool (20) according to any of the preceding claims, wherein the directional sound generator is a transducer.

14. Downhole tool (20) according to any of the preceding claims, wherein the downhole tool (20) is suitable for being deployed in a production well or is suitable for being deployed in an injection well.

15. Downhole tool (20) according to any of the preceding claims, wherein the wave generator device (30) and/or the second wave generator device (40) and/or the third wave generator device (50) is/are designed to couple ultrasonic sound waves (32, 42) into the outside fluid (16, 17, 18).

Description

BRIEF DESCRIPTION OF THE FIGURES

[0041] It is shown in

[0042] FIG. 1 a schematic cross-sectional view of an earth formation with a downhole tool in a well bore;

[0043] 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;

[0044] FIG. 3 a cross-sectional schematic of a downhole tool in a well bore with particles in the outside fluid;

[0045] FIG. 4 another cross-sectional schematic of a downhole tool with particles having moved in comparison to FIG. 3;

[0046] FIG. 5 a downhole tool in a well bore having a leak;

[0047] FIG. 6 an experimental setup of an experimental downhole tool;

[0048] FIG. 7 detail view of the experimental downhole tool;

[0049] FIG. 8 a schematic of a downhole tool in a liner;

[0050] FIG. 9 example of a signal result;

[0051] FIG. 10 example of a measurement result using an evaluation unit;

[0052] FIG. 11 another example of a measurement result using an evaluation unit.

DETAILED DESCRIPTION OF THE INVENTION

[0053] 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.

[0054] 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, CO.sub.2 or nitrogen in case of an injection well.

[0055] 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.

[0056] 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 or even in the reservoir 8.

[0057] The downhole tool 20 is equipped with a first wave generator device 30 which couples a wave 32 into the outside fluid to detect and/or track a particle 60 in the outside fluid.

[0058] 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. The downhole tool 20 comprises a power supply 92.

[0059] FIG. 3 depicts a sideview of a downhole tool 20 in a well bore 2, the downhole tool 20 having a first wave generator device 30 at a side of the downhole tool 20. The first wave generator device couples waves 32 into the outside fluid 18. While propagating through the outside fluid 18 the waves 32 can hit inhomogeinities 60, such as particles of any kind which are worn by the outside fluid 18. In other words, the particles 60 are used as markers indicating the movement of the outside fluid 18, e.g. the velocity in the case of one-dimensional analysis, which happens to be an easy way of measurement when one wave generator device 30 is used.

[0060] The waves 32, e.g. ultrasound waves 32, are reflected or more generally scattered, at said inhomogeneities 60 thereby generating new waves at said inhomogeneities 60. These new waves are referred to as reflections 70.

[0061] As can be seen in FIG. 3 at several inhomogeneities 60 reflections 70 are indicated. These particles 60 together form a group of particles 72 or a pattern 72. The downhole tool 20 is capable of observing whether the pattern 72 keeps its structure or whether the inhomogeneities 60 show a movement in relation to each other, thereby altering the pattern 72.

[0062] FIG. 4 indicates at most the same system as described with respect to FIG. 3, but the inhomogeneities 60 have moved in the longitudinal fluid flow. So to say, the inhomogeneities 60 have moved towards the downhole tool 20. However, as the downhole tool 20 also detects the pattern 72, it is capable of observing, that, in this case, no intra-pattern-movement is present, as the pattern 72 is unamended and only translationally moved with respect to the downhole tool 20 and/or with respect to the well bore 2. In other words, the downhole tool 20 is able to measure the flow of the outside fluid 18 with a single transducer, which is the first wave generator device 30, by monitoring the particle induced reflections.

[0063] FIG. 5 shows another embodiment of the downhole tool 20 deployed in a well bore 2 having a leakage 65. A longitudinal fluid flow direction 14 is indicated depicting the main flow in the well bore 2, or in other words, the wanted flow. Another fluid flow direction 15 at the leakage 65 indicates a fluid flow not pointing towards the same direction as the longitudinal fluid flow direction 14. In other words, the other fluid flow direction 15 shows a transverse component of translation with respect to the longitudinal fluid flow direction 14. As the case may be, the other fluid flow direction 15 to the leakage 65 may be a cross flow 15.

[0064] The downhole tool 20 in the embodiment of FIG. 5 comprises two wave generators 30, 40, where the first wave generator 30 couples waves 32 into the outside fluid 18 and the second wave generator 40 couples waves 42 into the outside fluid 18. The waves 32, 43 can have identical properties, but it is preferred to e.g. allow identification of specific wave by using a different tune or pulse width or the like.

[0065] The waves 32, 42 hit inhomogeneities 60, wherein reflections 70 are generated. The downhole tool can detect these reflections 70 with a receiver device 25. In this embodiment, the first and the second wave generator devices 30, 40 are designed such, that they are able to both couple waves into the outside fluid 18 and also detect waves, such as reflections 70, from the outside fluid 18. In other words, each wave generator device 30, 40 is a combined wave generator and detection device 25, 30, 40.

[0066] As is shown in FIG. 5, by obtaining reflection information data from the first and the second wave generator device 30, 40 the downhole tool 20 is capable of determining vectoriel velocity components for each of the inhomogeneities 60.

[0067] The downhole tool 20 of FIG. 5 further comprises an evaluation device 27 for evaluating e.g. fluid flow velocity components. The evaluation device 27 further can determine the particle pattern 62.

[0068] FIG. 6 shows an experimental setup of an experimental downhole tool 20a in an experimental well bore 2a for determination of downhole tool properties. An outside fluid 18 is filled in the experimental well bore 2a, the outside fluid 18 comprising inhomogeneities 60 to be detected by the downhole tool 20a.

[0069] FIG. 7 shows a close look of the frontside of the downhole tool 20a showing three wave generator devices 30, 40, 50.

[0070] FIG. 8 shows a schematical setup of the measurement principle. The downhole tool 20 comprises the first, the second and a third wave generator device 30, 40, 50. Each wave generator device 30, 40, 50 couples waves into the outside fluid 18. Inhomogeneities 60, or particles 60, are present in the outside fluid 18. The particles 60 comprise a particle velocity, whereas the particle velocity can be divided into directional velocity components, such as the velocity v of the particle in the direction of the sensor. t.sub.i indicates the echo delay, which is the time between coupling the wave into the outside fluid 18 and receiving the reflection 70 at the downhole tool 20. For example, for one specific particle moving in time from position 60 to position 60, e.g. coming closer to the downhole tool 20 as shown in FIG. 8, a first echo delay indicated by t.sub.1 is measured at a first point in time, whereas a second echo delay indicated by t.sub.2 is measured at a second point in time which is after the first point in time. The velocity of the particle in the direction of the first wave generator device 30 is then given by the formula

[00001]$v=\frac{c*\left(t_1-t_2\right)}{T}$

[0071] wherein c is the velocity of ultrasound in water, when ultrasound is used as the wave shape, and T is the time between two measurements, which is e.g. the time between the coupling of the first wave 32 and the coupling of the second wave 32 into the outside fluid 18.

[0072] For modelling crossflow in the experimental well bore 2a of FIG. 8 an suction pump 65a is installed as a leakage 65. A crossflow 15 thereby is generated inside the (experimental) well bore 2a. The experimental cross flow generates a leakage of 700 ml/s. A rotor generates a constant longitudinal fluid flow direction 14, which is comparable to the longitudinal fluid flow 14 in a well bore 2.

[0073] FIG. 9 shows the overlay of a typical wave 32 and its corresponding reflection 70. Shown are typical puls-echo signals of two consecutive measurements with a transducer frequency of f=2 MHz, a burst length n=3 and a particle moving away from the receiver device 25 with a velocity v of about 25 mm/s.

[0074] FIG. 10 shows the result of evaluating with the evaluation device 27 fluid flow velocity components of the outside fluid with a first, a second and a third wave generator device 30, 40, 50. The downhole tool 20a is moved along the well bore 2a passing a leakage 65.

[0075] FIG. 11 shows another result of evaluating with the evaluation device 27 fluid flow velocity components of the outside fluid when passing a leakage 65 with the downhole tool 20a.

[0076] To summarize, a downhole tool 20 which is capable of identifying disturbances, leakages 65 or other losses of fluid flow in a well bore 2 is presented. The downhole tool 20 uses a direction dependent flow measurement system and implements speckle tracking. By way of example, in a well bore having an oil production of 10.000 barrel per day a typical longitudinal fluid flow of about 18 l/s is reached corresponding to a fluid position change of 400 mm/s. It is desired to keep this fluid flow as constant as possible, e.g. detecting fluid flow deviations bigger than 5%, which is bigger than 0.9 l/s. Such fluid flow measurement using speckle tracking is successfully demonstrated with the experimental setup. A direction depending flow measurement is possible. Thus, a detection of a leakage 65 in a well bore 2 is possible with the presented downhole tool 20.

[0077] 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.

[0078] 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

[0079] 2 Well bore [0080] 2a experimental well bore [0081] 4 earth formation [0082] 6 surface [0083] 8 reservoir [0084] 9 extraction facility [0085] 10 well head [0086] 12 casing/liner [0087] 14 Longitudinal fluid flow direction [0088] 15 Fluid flow direction (e.g. crossflow) [0089] 16 fluid [0090] 17 fluid [0091] 18 fluid, outside fluid [0092] 20 downhole tool [0093] 20a experimental downhole tool [0094] 21 moving means [0095] 25 receiver device [0096] 27 evaluation device [0097] 28 housing [0098] 30 first wave generator device [0099] 32 wave coupled into the outside fluid [0100] 40 second wave generator device [0101] 42 wave coupled into the outside fluid [0102] 50 third wave generator device [0103] 60 inhomogeinity (such as particles) [0104] 62 pattern (such as a pattern of particles) [0105] 65 Leakage or opening or crack [0106] 65a experimental leakage [0107] 70 Reflection [0108] 92 stand-alone power supply