Downhole sampling tool

Abstract

The present invention relates to a downhole sampling tool for taking out fluid samples of a fluid present in a casing having an internal cross-sectional casing area. The downhole sampling tool comprises a first tool part and a second tool part, a sampling inlet arranged in the first part, and an actuation unit arranged in the second part adapted to move the sampling inlet into contact with the fluid in a first part of the casing area for taking out a fluid sample of the fluid present in that part of the casing area.

Claims

1 . A downhole sampling tool ( 1 ) for taking out fluid samples of a fluid ( 2 ) present in a casing ( 3 ) having an internal cross-sectional casing area, the downhole sampling tool comprising a first tool part ( 4 ) and a second tool part ( 5 ), a sampling inlet ( 6 ) arranged in the first part, a pump unit for sucking the fluid in through the sample inlet, and an actuation unit ( 7 ) arranged in the second part, adapted to move the sampling inlet into contact with the fluid in a first part of the casing area for taking out a fluid sample of the fluid present in that part of the casing area. 2 . A downhole sampling tool according to claim 1 , wherein the actuation unit is adapted to move the sample inlet between a retracted and a projected position. 3 . A downhole sampling tool according to claim 1 , wherein the second tool part comprises a through-going recess ( 18 ) in which the arm member is arranged and projects from. 4 . A downhole sampling tool according to claim 1 , wherein the actuation unit comprises a hydraulic cylinder for moving the sampling inlet between the retracted and the projected position. 5 . A downhole sampling tool according to claim 1 , wherein the actuation unit comprises an electrical motor for moving the sampling inlet between the retracted and the projected position. 6 . A downhole sampling tool according to claim 1 , wherein the sampling inlet is arranged in an outer surface of the first tool part. 7 . A downhole tool according to claim 2 , wherein the first tool part comprises a plurality of sampling inlets. 8 . A downhole sampling tool according to claim 1 , wherein the first tool part is an arm member ( 8 ) movably connected with the second tool part. 9 . A downhole sampling tool according to claim 4 , wherein the arm member comprises the sampling inlet. 10 . A downhole sampling tool according to claim 5 , wherein the arm member comprises a fluid channel ( 10 ) extending between the sampling inlet and an opening ( 30 ) arranged in an opposite end ( 31 ) of the arm member in relation to the sampling inlet. 11 . A downhole sampling tool according to claim 1 , wherein the actuation unit is adapted to rotate the first tool part. 12 . A downhole sampling tool according to claim 4 , wherein the second tool part comprises a recess ( 18 ) in which the arm member is arranged and projects from. 13 . A downhole sampling tool according to claim 1 , wherein the actuation unit comprises an anchor unit ( 52 ) adapted to move the second tool part in a radial direction of the sampling tool. 14 . A downhole sampling tool according to claim 1 , wherein the first tool part comprises a first arm part ( 41 ) and a second arm part ( 42 ) rotatably connected at one end, the first arm part being securely rotatably connected to the second tool part at the opposite end, and the second arm part being axially movably arranged in the second tool part at the opposite end. 15 . A downhole sampling tool according to claim 10 , wherein the sampling inlet is arranged at the one end where the first and second arm parts are rotatably connected. 16 . A downhole sampling tool according to claim 1 , further comprising a pump ( 9 ) being in fluid communication with the sampling inlet. 17 . A downhole sampling tool according to claim 1 , further comprising a sample chamber ( 19 ) being in fluid communication with the sampling inlet. 18 . A downhole sampling tool according to claim 1 , further comprising sample testing equipment ( 11 ) being in fluid communication with the sampling inlet for performing a sample test on the fluid sample. 19 . A downhole sampling tool according to claim 1 , wherein the sampling tool comprises a capacitance measuring unit ( 50 ) for identifying the phase of the fluid, such as gas ( 21 ) and water ( 23 ).
FIELD OF THE INVENTION [0001] The present invention relates to a downhole sampling tool for taking out fluid samples of a fluid present in a casing having an internal cross-sectional casing area. BACKGROUND ART [0002] When a well producing oil or gas is producing too much water, the water may be water occurring naturally in the reservoir, or it may come from a displacement fluid, such as sea water, injected to displace the zone of oil or gas. Since natural reservoir water has another content of minerals than the injected water, an examination of the water can determine where the water comes from. However, by measuring the water at the top of the well, the naturally occurring water may be mixed with the displacement, making the measurements misleading. It is therefore necessary to obtain measurements downhole in order to determine which water source the water comes from. SUMMARY OF THE INVENTION [0003] It is an object of the present invention to wholly or partly overcome the above disadvantages and drawbacks of the prior art. More specifically, it is an object to provide an improved sampling tool for taking out samples of the fluid in a casing downhole. [0004] The above objects, together with numerous other objects, advantages, and features, which will become evident from the below description, are accomplished by a solution in accordance with the present invention by a downhole sampling tool for taking out fluid samples of a fluid present in a casing having an internal cross-sectional casing area, the downhole sampling tool comprising a first tool part and a second tool part, a sampling inlet arranged in the first part, and an actuation unit arranged in the second part, adapted to move the sampling inlet into contact with the fluid in a first part of the casing area for taking out a fluid sample of the fluid present in that part of the casing area. [0008] In an embodiment, the downhole sampling tool may further comprise a pump unit for sucking the fluid in through the sample outlet. [0009] Furthermore, the actuation unit may be adapted to move the sample inlet between a retracted and a projected position. [0010] Moreover, the second tool part may comprise a through-going recess in which the arm member is arranged and projects from. [0011] Additionally, the actuation unit may comprise a hydraulic cylinder for moving the sampling inlet between the retracted and the projected position. [0012] Also, the actuation unit may comprise an electrical motor for moving the sampling inlet between the retracted and the projected position. [0013] Further, the pump unit may be arranged in the first tool part. [0014] In addition, the pump may be in fluid connection with the sampling inlet. [0015] In an embodiment, the sampling inlet may be arranged in an outer surface of the first tool part. [0016] Said first tool part may comprise a plurality of sampling inlets. [0017] The sampling inlets may be angularly displaced around the outer surface of the first tool part. [0018] Moreover, the sampling inlets may be arranged with a mutual angle which is equal to or less than 180°, preferably equal to or less than 90°, more preferably equal to or less than 45°, and even more preferably equal to or less than 30°. [0019] Also, the first tool part may comprise a first element and a second element. [0020] Further, the second element may extend or be adapted to extend in a radial direction in relation to the first element. [0021] Additionally, the sampling inlet may be arranged on the second element. [0022] Furthermore, the second element may be radially displaceable in relation to the first element. [0023] In addition, the actuation unit may rotate the first element of the first tool part in relation to the second tool part. [0024] Said first tool part may comprise a plurality of second elements. [0025] Also, the first tool part may be an arm member movably connected with the second tool part. [0026] Moreover, the arm member may comprise the sampling inlet. [0027] Further, the sampling inlet may be arranged in one end part of the arm member, and the arm member may be connected with the second tool part in another opposing end part. [0028] Additionally, the arm member may comprise a fluid channel extending between the sampling inlet and an opening arranged in an opposite end of the arm member in relation to the sampling inlet. [0029] The opening may be in fluid communication with a fluid channel in the second tool part. [0030] In an embodiment, a tube may extend along the arm and the sampling inlet may be arranged in one end of the tube. [0031] In addition, the actuation unit may be adapted to rotate the first tool part. [0032] Also, the actuation unit may be adapted to rotate the arm member. [0033] In an embodiment, the second tool part may comprise a recess in which the arm member is arranged and projects from. [0034] Moreover, the arm member may be moveable between a retracted position and a projected position. [0035] Furthermore, the actuation unit may comprise an anchor unit adapted to move the second tool part in a radial direction of the sampling tool. [0036] Additionally, the first tool part may be adapted to be displaced radially in relation to the second tool part. [0037] Also, the second tool part may have an end facing the first tool part, the end comprising a groove having a predetermined pattern enabling movement of a corresponding projection arranged on the first tool part in the groove. [0038] In an embodiment, the first tool part may comprise a first arm part and a second arm part rotatably connected at one end, the first arm part being securely rotatably connected to the second tool part at the opposite end, and the second arm part being axially movably arranged in the second tool part at the opposite end. [0039] Said first arm part and second arm part constitute the second element of the first tool part, and the second element is connected to the first element of the first tool part. [0040] Moreover, the actuation unit may rotate the first element of the first tool part and thereby the first and second arm parts. [0041] Further, the sampling inlet may be arranged at the one end where the first and second arm parts are rotatably connected. [0042] In addition, the axial movement of the second arm part at the opposite end may provide a radial displacement of the sampling inlet. [0043] The first tool part may comprise a plurality of first and second arm part sets. [0044] Also, the sampling tool may comprise a driving unit. [0045] In an embodiment, the driving unit may comprise retractable wheels. [0046] Furthermore, the wheels may be adapted to move the second tool part in a radial direction of the sampling tool by projecting the wheels in a radial direction of the sampling tool. [0047] In another embodiment, the driving unit may comprise caterpillar tracks, etc. [0048] The downhole sampling tool as described above may further comprise a pump being in fluid communication with the sampling inlet. [0049] Moreover, the sampling tool may comprise a motor for driving the pump. [0050] Also, the downhole sampling tool as described above may comprise a sample chamber being in fluid communication with the sampling inlet. [0051] Further, the downhole sampling tool as described above may comprise sample testing equipment being in fluid communication with the sampling inlet for performing a sample test on the fluid sample. [0052] Said sample testing equipment may first identify the phase of the fluid sample and second the content of the fluid sample. [0053] Additionally, the sample testing equipment may comprise elect odes for identifying a salinity content of the fluid sample. [0054] A communication device may be arranged in connection with sample testing equipment for communicating sample test data to an operator or a processing device. [0055] Furthermore, the sampling tool may comprise a storing device for storing sample test data. [0056] Also, the sample testing equipment may comprise a fibre-optic sensor based on surface-plasmon resonance for determining the refractive index and used for measuring the degree of salinity of the fluid sample. [0057] In addition, the sample testing equipment may comprise microwave radiometry for determining the dielectric constant of the fluid sample. [0058] In an embodiment, a sensor may be arranged in connection with the sampling inlet, the sensor detecting the phase of the fluid present in the casing area. [0059] Moreover, the sample testing equipment may comprise a gas sensor, such as an infrared point sensor, an ultrasonic gas detector, an electrochemical gas detector or a semiconductor sensor. [0060] Additionally, the sample testing equipment may comprise a capacitance measuring unit for identifying the phase of the fluid sample. [0061] Further, the sampling tool may comprise a capacitance measuring unit for identifying the phase of the fluid, such as gas and water. [0062] The sampling tool may further comprise a radioactive source emitting gamma rays for identifying the phase of the fluid, such as gas and water. [0063] Said fluid may be gas or water. [0064] In an embodiment, the sample testing equipment may comprise an indication unit adapted to indicate the presence of a predetermined tracer in the fluid sample. [0065] The tracer may be radioactive source or a chemical. [0066] Also, the tracer may be a gas or a fluid. [0067] Moreover, the sampling tool may be tubular extending in an axial direction. BRIEF DESCRIPTION OF THE DRAWINGS [0068] The invention and its many advantages will be described in more detail below with reference to the accompanying schematic drawings, which for the purpose of illustration show some non-limiting embodiments and in which [0069] FIG. 1 shows a downhole sampling tool according to the present invention, [0070] FIG. 2 shows a cross-sectional internal area of the fluid in the casing, [0071] FIG. 3 shows a partial cross-sectional view of the sampling tool of FIG. 1 , [0072] FIG. 4 shows a partial view of the inside of the sampling tool of FIG. 1 , [0073] FIG. 5 shows a partial cross-sectional view of another embodiment of the sampling tool, [0074] FIG. 6 shows another embodiment of the sampling tool, [0075] FIGS. 7 a and 7 b show a front view of the sampling tool of FIG. 6 , [0076] FIG. 8 shows yet another embodiment of the sampling tool, [0077] FIG. 9 shows yet another embodiment of the sampling tool, and [0078] FIG. 10 shows yet another embodiment of the sampling tool. [0079] All the figures are highly schematic and not necessarily to scale, and they show only those parts which are necessary in order to elucidate the invention, other parts being omitted or merely suggested. DETAILED DESCRIPTION OF THE INVENTION [0080] FIG. 1 shows a downhole sampling tool 1 for taking out fluid samples of a fluid 2 present in a casing 3 downhole or a casing 3 in a borehole. The sampling tool 1 comprises a first tool part 4 , a second tool part 5 and a sampling inlet 6 arranged in the first part. In order to sample fluid from all areas of the casing, the sampling tool 1 comprises an actuation unit 7 arranged in the second part, adapted to move the sampling inlet into contact with the fluid in a first part of the casing area for taking out a fluid sample of the fluid present in that part of the casing area. The first part 4 is in FIG. 1 an arm member 8 , and the sampling inlet 6 is arranged in the end of the arm member 8 . The arm member 8 is rotated by the actuation unit 7 between a retracted position in the sampling tool 1 and a projected position, as shown in FIG. 1 . The sampling tool 1 comprises a pump unit for sucking the fluid in through the sample inlet in order to measure fluid samples in the sampling tool and/or store samples of borehole fluid in the sampling tool for further investigation. It is essential to the tool that the tool comprises a pump for sucking fluid samples into the sampling tool. [0081] The sampling tool 1 comprises a through-going recess 18 through which the arm member can pass to project on opposite sides of the recess of the sampling tool 1 , as indicated by the arrow in FIG. 1 . By having a through-going recess 18 , the versatility of the tool is drastically increased since the actuation unit may project in two directions for each stationary position of the tool. This enables close to a doubling of the sampling speed, since the arm member may be projected to both sides of the sampling tool without rearranging the sampling tool. Furthermore the through-going recess 18 enables the user to avoid problems projecting the arm member in situations where the arm member has been blocked or jammed in one direction. The user may in these situations unblock or unjam the arm member by projecting the arm member in the opposite direction. Jamming is a serious and very cost-intensive problem during downhole operations. [0082] Due to the spatial limitations downhole, the actuation unit 7 may be capable of moving the sample inlet 6 between a retracted and a projected position to save space during movement of the downhole tool in a retracted position and to reach into the borehole fluid in the projected position. One tool is furthermore capable of fitting a broader range of well sizes in that the width of the tool can be changed. [0083] When a well producing oil 22 or gas 21 is producing too much water, the water 23 may be water occurring naturally in the reservoir, or it may be displacement fluid, such as sea water, injected to displace the zone of oil or gas. The natural reservoir water has another content of minerals than the injected water, and by taking out samples and measuring the fluid flowing in the casing 3 , it can be determined which water source the water comes from. When producing oil, the displacement fluid may also be injected gas or steam. In deviated or horizontal wells, the fluid divides into fluid phases so that the water 23 is located in the bottom part of the casing, as illustrated in the cross-sectional internal area of the casing shown in FIG. 2 . In order to take a sample of the water, the first tool part 4 needs to be moved so that the sampling inlet 6 is arranged in the water phase of the fluid and thus in the bottom to be able to take out a sample of water, as shown in FIG. 2 . The sampling tool 1 has an actuation unit to be able to move the first part of the sampling tool 1 into a certain area of interest of the casing. In the event that the fluid phase to be investigated is the gas phase 21 , the actuation unit 7 needs to move the first tool part 4 so that the sampling inlet is located in the area of the cross-sectional internal area of the casing comprising gas, which in FIG. 2 is the top part of the casing. [0084] As shown in FIGS. 1 and 3 , the sampling inlet is arranged in one end part of the arm member 8 , and the arm member is connected with the second tool part 5 in another opposing end part. The arm member 8 comprises a fluid channel 10 extending between the sampling inlet and an opening 30 arranged in an opposite end 31 of the arm member in relation to the sampling inlet. The opening 30 is in fluid communication with a fluid channel 32 in the second tool part 5 . The sampling tool 1 further comprises a pump 9 intended to pump fluid in through the sampling inlet through a fluid channel 10 in the arm member and further past the pump 9 to sample testing equipment 11 in order to test the sample of fluid before ejecting the fluid back into the casing through an outlet 12 . [0085] The arm member 8 is moved between a projected and a retracted position by the actuation unit 7 , which is shown in FIG. 4 . The arm member is rotatably connected to the second tool part 5 by means of a shaft 14 connected with a gear wheel 15 driven by a toothed shaft 16 which is axially displaced by a second gear wheel 17 driven by an electrical motor 38 . In this way, the electrical motor drives the arm member 8 between the retracted position and the projected position. [0086] As shown in FIG. 5 , the sampling tool 1 comprises sample chambers 19 fluidly connected with a control device 20 controlling the fluid from the sample testing equipment 11 . When the fluid has been tested in the sample testing equipment, the control device receives a signal from the sample testing equipment 11 to either let the tested fluid out through outlet 12 or to lead the fluid into the sample chambers 19 to collect a sample in one of the chambers 19 . The inlets of the sample chambers 19 comprise a one-way valve so that when the first sample chamber is filled, the fluid cannot escape the chamber again. The valve of the second sample chamber may then be activated by the control device when a new sample needs to be collected. The sample chambers comprise a movable piston dividing the chamber into a first chamber part 24 and a second chamber part 25 . The first chamber part 24 comprises gas so that when the fluid is let into the chamber, the piston is moved towards the bottom 26 of the chamber opposite the inlet valve 27 compressing the gas. [0087] The fluid let into the sample chambers may also be controlled by a hydraulic block so that the fluid is let from the control device to one hydraulic block instead of having one valve at the inlet of every sample chamber 19 . [0088] In FIG. 6 , the sampling tool comprises a plurality of sampling inlets arranged in an outer surface 28 of the first tool part 4 . The first tool part 4 is moved so that a sampling inlet 6 is brought into a section of the cross-sectional area of the casing 3 , e.g. a top section, as shown in FIG. 7 a , in order to take out a sample of the fluid in that section. In FIG. 7 b , the first tool part is moved sideways to take out a sample near an opening 29 in the casing wall, e.g. a perforation or a leak caused by erosion. As illustrated, water 23 enters through the opening 29 and is mixed with oil and/or gas on the opposite side of the tool, and it is therefore important to take a sample just outside the opening to determine the content of the fluid entering the opening. The fluid entering the opening may also be oil as intended, and then it can be established that the water does not enter through that perforation. [0089] Thus, the first tool part 4 of the sampling tool of FIGS. 6-7 b is adapted to be displaced radially in relation to the second tool part 5 . In order to do so, the second tool part has an end facing the first tool part 4 , the end comprising a groove having a predetermined pattern enabling movement of a corresponding projection arranged on the first tool part in the groove. In this way, the projection of the first tool part 4 slides back and forth or up and down in the groove of the second tool part 5 to displace the first tool part in relation to the second tool part to bring the sampling inlet into contact with fluid in a certain area of the casing. [0090] In FIGS. 6-7 b, the sampling inlets are angularly displaced around the outer surface of the first tool part. Thus, the sampling inlets are arranged with a mutual angle which is equal to or less than 45°. In another embodiment, the sampling inlets are arranged with a mutual angle which is equal to or less than 180°, preferably equal to or less than 90°, and even more preferably equal to or less than 30°. As shown in FIGS. 7 a and 7 b , the sampling tool has only three inlets angularly displaced at an angle of 45°. [0091] In FIG. 8 , the first tool part of the downhole sampling tool comprises a first arm part 41 and a second arm part 42 rotatably connected a first end 41 a, 42 a, the first arm part being securely rotatably connected inside the tool housing at the opposite end of the arm part, and the second arm part being axially movably arranged in the first tool part at the opposite end. The axial movement of the second arm part at the opposite end provides a radial displacement of the sampling inlet in relation to the tool. The second tool part comprises a motor for rotation of the first tool part and thus also the first and second arm part, as illustrated by the arrow 44 , to bring the inlet 6 arranged in the first end 41 a into contact with fluid in a certain area in the casing 3 . [0092] In FIG. 9 , the first tool part of the downhole sampling tool also comprises a set of arm parts 41 , 42 , i.e. a first arm part 41 and a second arm part 42 , being rotatably connected at their first ends 41 a, 42 a. In this embodiment, the first arm part is securely rotatably connected with the second tool part at the opposite end of the arm part, and the second arm part is axially movably arranged in the second tool part at the opposite end. The sampling tool 1 comprises several sets of arm parts so as to reach several fluid areas inside the casing, e.g. a top part and a bottom part of the casing, as shown in FIG. 9 . [0093] The second arm part 42 of FIGS. 8 and 9 is rotatably connected with a piston 45 which is moved by means of fluid forcing the piston towards the arm parts. In order to retract the second arm part, the piston may compress a spring (not shown) arranged inside the piston housing, or the second arm part is just retracted when retracting the sampling tool from the well, e.g. when meeting a restriction in the well, such as a landing nipple. [0094] The arm member 8 may also be a probe radially projected from the sampling tool housing, as shown in FIG. 10 . The sampling tool further comprises a motor located in the second tool part 5 for rotation of the first tool part 4 in relation to the second tool part 5 . The arm member 8 comprises a fluid channel 10 fluidly connected with the pump 9 for suction of well fluid into the tool and into the sampling testing equipment 11 and further out through an outlet 12 . [0095] As shown in FIG. 11 , the actuation unit of the downhole sampling tool may further comprise a hydraulic cylinder 71 for moving the sampling inlet between the retracted and the projected position by pushing a crank member 71 of the arm member 8 . Alternatively, the actuation unit may comprise an electrical motor (not shown) for moving the sampling inlet between the retracted and the projected position. [0096] Referring to FIG. 1 , the sampling tool 1 further comprises a (driving unit 60 comprising retractable wheel arms 61 having one end rotatably connected with the housing 62 of the driving unit 60 and a wheel 63 arranged in the other end 64 opposite the end rotatably connected with the housing. Each wheel comprises a motor adapted to move the second tool part in a radial direction of the sampling tool by projecting the wheel arms in a radial direction of the sampling tool. In another embodiment, the driving unit comprises caterpillar tracks or similar movable arrangement. The driving unit is connected to a pump for forcing the wheel arms to project and the wheels to turn and thus drive the sampling tool forward in the well. The pump 65 is driven by a motor 66 which is powered through a wireline 68 via an electrical control unit 67 . [0097] The sampling tool may further comprise a logging tool 50 e.g. arranged in front of the tool to determine the fluid phase in the casing fluid to be able to arrange the sampling inlet in the fluid phase that needs to be investigated. In the event that the logging tool has determined a presence of gas, oil and water, the sampling inlet 6 in the first tool part can be moved to the gas phase to test a sample of gas or into the water phase to test a sample of water to determine whether the gas or water comes from the displacement fluid or whether it is gas or water naturally occurring in the formation. The logging tool is capable of determining the gas, oil and water phase, as illustrated in FIG. 2 , and based on such an image, the first tool part is moved. The logging tool may comprise electrodes arranged in the periphery of the logging tool 50 , such as a capacitance measuring unit, measuring the capacitance between the electrodes. [0098] The sampling tool 1 may also comprise an anchor unit 52 , as shown in FIG. 6 , having anchors 53 radially projectable from the tool housing 54 . The anchors 53 of the downhole sampling tool may also be comprised in the actuation unit 7 so that the anchor unit is adapted to move the second tool part 5 in a radial direction of the sampling tool. [0099] The sampling tool further comprises a communication device 56 arranged in connection with sample testing equipment 11 for communicating sample test data to an operator or a processing device 55 , as shown in FIG. 6 . The data from the sample testing equipment may be stored in a storing device 57 , and before the data is communicated to an operator, the data is processed so that only data comprising new information is communicated. [0100] In one embodiment, the fluid channel 10 from the sampling inlet to the pump may be a tube extending along the arm member, and the sampling inlet may be arranged in one end of the tube. [0101] The sampling testing equipment may comprise a gas detector, such as an infrared point sensor, ultrasonic gas detectors, electrochemical gas detectors and semiconductor sensors. [0102] Also, the sample testing equipment may first identify the phase of the fluid sample, such as gas or liquid, and second the content of the fluid sample. [0103] The sample testing equipment may comprise electrodes for identifying a salinity content of the fluid sample. The electrodes are arranged on opposite sides of the chamber in the testing equipment, and when a sample is present, power is supplied to the electrodes in order to determine the salinity of the sample. This is especially expedient when the fluid sample is water. The water occurring naturally in the reservoir is expected to have a lower salinity than the salt water typically injected into the formation to displace the oil or gas to be produced. [0104] The sample testing equipment may also comprise a fibre-optic sensor based on surface-plasmon resonance for determining a refractive index, which is used for measuring the degree of salinity of the fluid sample. The sensor has a transducing element consisting of a multilayer structure deposited on a side-polished monomode optical fibre. [0105] Furthermore, the sample testing equipment may additionally comprise microwave radiometry for determining a dielectric constant of the fluid sample. For instance, measurements of the dielectric constant may be conducted at S-bond and L-band. [0106] The sample testing equipment may also comprise a capacitance measuring unit for identifying the phase of the fluid sample. By measuring the capacitance between a plurality of electrodes, the phases of the fluid can be determined. [0107] Furthermore, the sampling tool may also comprise a radioactive source emitting gamma rays for identifying the phase in the casing fluid to be able to arrange the sampling inlet in the fluid phase that needs to be investigated. In the event that the a radioactive source has determined the presence of gas, oil and water, the sampling inlet in the first tool part can be moved to the gas phase to test a sample of gas or in the water phase to test a sample of water to determine if the gas or water comes from the displacement fluid or the natural gas or water occurring in the formation. [0108] In some circumstances, a tracer may be added to the displacement fluid. The sample testing equipment may advantageously comprise an indication unit adapted to indicate the presence of the tracer in the fluid sample so that it may easily be detected that the fluid sample is part of the displacement fluid. [0109] The tracer may be a colour or another chemical tracer that is easily detected from the other chemical components present in the displacement fluid. The tracer may be radioactive source, a colour or another chemical that is easily detected from the other chemical components present in the displacement fluid, and the tracer may be a gas or a liquid. [0110] The invention also relates to a method for taking out fluid samples of a fluid present in a casing having an internal cross-sectional casing area, the method comprising arranging the sampling tool in a casing, positioning the sampling inlet of the sampling tool in a predetermined part of the cross-sectional casing area, and taking out a fluid sample of the fluid present in that part of the casing area. [0114] The method may comprise a subsequent step of testing the fluid sample for its phase. [0115] The method may also comprise the step of testing the fluid sample for content, e.g. salinity content. [0116] Furthermore, the sampling inlet may be moved, enabling taking out an additional fluid sample in that part of the casing area. [0117] Additionally, the sampling tool may comprise a plurality of sampling inlets, and several fluid samples may be taken out in that part of the casing area by the plurality of sampling inlets. [0118] Moreover, the sample inlet or plurality of inlets may be moved by radial movement, axial movement, rotation or a combination thereof. [0119] The sampling tool may comprise a capacitance measuring unit for identifying the phase of the fluid, such as gas and/or water, the positioning of the sampling tool being performed based on the phase measurements of the capacitance measuring unit. [0120] Although the invention has been described in the above in connection with preferred embodiments of the invention, it will be evident for a person skilled in the art that several modifications are conceivable without departing from the invention as defined by the following claims.

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