Inspection of an electrically conductive object using eddy currents
A device and method for inspecting an inspection object of in the vicinity of a further object, both of electrically conductive material, the device comprising a transmitter/receiver arrangement for generating an electromagnetic field in the inspection object, and for measuring a signal indicative of a transient eddy current which is generated in the inspection object by the electromagnetic field, wherein the device further comprises a magnetic shield means, providing at least a partial magnetic shield for the transmitter/receiver arrangement in a direction other than a measurement direction; use of the device from inside an annulus between an inner and an outer tubular, and a method of operating a hydrocarbon well having a well completion, and inspecting the well completion from inside an annulus.
1. A device for inspecting an inner tubular of electrically conductive material in the vicinity of an outer tubular of electrically conductive material, wherein the inner tubular is located within the outer tubular, further comprising an annular space between the inner tubular and the outer tubular, the device located within the annular space, the device comprising:
a transmitter/receiver arrangement for generating a transient electromagnetic field in the inner tubular, and for measuring a signal indicative of a transient eddy current which is generated in the inner tubular by the transient electromagnetic field, wherein the transmitter/receiver arrangement has a measurement direction towards the inner tubular, and wherein the device further comprises a magnetic shield means, providing at least a partial magnetic shield for the transmitter/receiver arrangement in a direction towards the outer tubular.
2. The device according to claim 1 , wherein the magnetic shield means comprises a piece of ferromagnetic material, selected from the group consisting of a ferromagnetic alloy, a ceramic, and a mu-metal.
3. The device according to claim 1 , wherein the magnetic shield means comprises a sheet or plate having a cross-sectional area that is at least 50% of a cross-section cross-sectional area of the transmitter/receiver arrangement facing the outer tubular during normal operation, when both are cross-sectioned on a plane containing the direction of measurement.
4. The device according to claim 1 , wherein the transmitter/receiver arrangement has a measurement side, and wherein at least part of the magnetic shield means is arranged at a side opposite to the measurement side with respect to the transmitter/receiver arrangement.
5. The device according to claim 1 , wherein the magnetic shield means comprises an electromagnetic shielding transmitter that is arranged to produce a magnetic field that at least partly compensates the magnetic field generated by the transmitter/receiver arrangement at a side different from a measurement side of the transmitter/receiver arrangement.
6. The device according to claim 1 , wherein the device further comprises a fixation means which is arranged to fix the transmitter/receiver arrangement at a measurement position with respect to the inner tubular.
7. The device according to claim 6 , wherein the fixation means comprises a resilient member arranged to press the transmitter/receiver arrangement against the inner tubular and away from the outer tubular.
8. The device according to claim 7 , wherein the resilient member moves from a retracted position to an expanded position.
9. The device according to claim 6 , wherein the fixation means comprises a magnet.
10. The device according to claim 1 , further comprising: at least one orientation sensor arranged on the device to provide at least one output value; wherein the at least one output value allows to detect whether the device is arranged in a preferred orientation.
11. The device of claim 10 , wherein the at least one orientation sensor comprises an orientation receiver coil arrangement comprising at least one orientation receiver coil.
12. The device according to claim 11 , wherein the device has a device axis perpendicular to the measurement direction, wherein the orientation receiver coil arrangement defines an axis perpendicular to the device axis and to the measurement direction.
13. A method for inspecting an outer tubular of electrically conductive material in the vicinity of an inner tubular of electrically conductive material, wherein the method comprises the steps of
providing a device comprising a transmitter/receiver arrangement for generating a transient electromagnetic field in the outer tubular, and for measuring a signal indicative of a transient eddy current which is generated in the outer tubular by the transient electromagnetic field;
providing a magnetic shield means;
arranging the device in a measurement position with regard to the outer tubular and the magnetic shield means between the transmitter/receiver arrangement and the inner tubular; and
inspecting the outer tubular.
14. The method according to claim 13 , wherein the inner tubular and the outer tubular have substantially parallel axes.
15. The method according to claim 13 , further comprising: using at least one orientation sensor arranged on the device to provide at least one output value that is indicative of a deviation from a preferred orientation of the device with respect to the outer tubular.
16. The method according to claim 15 , wherein the at least one orientation sensor comprises an orientation receiver coil arrangement comprising at least one orientation receiver coil in which an orientation signal is induced in response to transient eddy currents generated in the outer tubular.
17. The method of claim 16 , wherein in the preferred orientation the measurement direction is perpendicular to the surface of the outer tubular, wherein the device has a device axis perpendicular to the measurement direction, wherein the orientation receiver coil arrangement defines an axis perpendicular to the device axis and to the measurement direction, and wherein the orientation signal is used to detect a deviation from the preferred orientation by rotation about the device axis.
18. The method of claim 17 further comprising adjusting the orientation of the device in response to the output value.
19. A method of operating a hydrocarbon well having a well completion comprising an inner and an outer tubular forming an annulus between them, the method comprising selecting the inner or outer tubular as an inspection object, wherein the non-selected inner or outer tubular comprises a further object, and inspecting the well completion from inside the annulus by using a device for inspecting the inspection object of electrically conductive material in the vicinity of the further object of electrically conductive material, by pointing the device towards the inspection object and providing a magnetic shield means between the device and the further object.
20. The method according to claim 19 , wherein hydrocarbons are produced from the well during or after the inspection.