METHODS AND LOCATING SYSTEMS FOR DETERMINING AN INSULATION FAULT LOCATION ON AN ELECTRIC CONDUCTOR OF A SUBSEA SUPPLY LINE

Abstract

Methods and locating systems for determining an insulation fault location on an electric conductor of a subsea supply line are provided. By applying electric voltage on the electric conductor, an electrochemical reaction takes place at an insulation fault location between the metallic conductor material and the seawater, said electrochemical reaction forming gas, which in turn is connected to developing noise. Sonic sensors capture the sonic waves produced thereby within and without of the subsea supply line and evaluate the measuring signals in order to determine the insulation fault location. Alternatively or additionally to capturing noise, the gas-bubble image patterns occurring at the insulation fault location are optically captured and consulted in order to determine the insulation fault location.

Claims

1. A method for determining an insulation fault location (40) on an electric conductor (11) of a subsea supply line (10), which can be filled with seawater (5), comprising the method steps: applying electric voltage to ground at the electric conductor (11), an electrochemical reaction taking place at the insulation fault location between a metallic conductor material of the electric conductor (11) and the seawater (5), said electrochemical reaction forming gas, and said electric voltage being formed by a modulated voltage impulse sequence, capturing sonic waves (20, 20c) of a noise made by formed gas bubbles (28), sonic waves (20, 20c) of the noise propagating within the subsea supply line (10) in the seawater filling (7) being captured using sonic sensors (18), which are installed at predetermined locations along the subsea supply line (10), evaluating measuring-signal impulse sequences supplied by the sonic sensors (18) in order to determine the insulation fault location (40).

2. The method according to claim 1, characterized in that the measuring-signal impulse sequences are evaluated by calculating a correlation of the applied voltage impulse sequence with the measured measuring-signal impulse sequences.

3. A method for determining an insulation fault location (40) on an electric conductor (11) of a subsea supply line (10), which can be filled with seawater (5), comprising the method steps: applying electric voltage to ground at the electric conductor (11), an electrochemical reaction taking place at the insulation fault location (40) between a metallic conductor material of the electric conductor (11) and the seawater (5), said electrochemical reaction forming gas, and said electric voltage being formed by a modulated voltage impulse sequence, capturing sonic waves (20, 20a, 20b) of a noise made by formed gas bubbles (28), sonic waves (20, 20a, 20b) of the noise being captured outside of the subsea supply line (10) using sonic sensors (18), which are installed at predetermined location in the seawater (5), evaluating measuring-signal impulse sequences supplied by the sonic sensors (18) in order to determine the insulation fault location (40).

4. The method according to claim 3, characterized in that the measuring signal impulse sequences are evaluated by calculating a correlation of the applied voltage impulse sequence with the measured measuring-signal impulse sequences.

5. A method for determining an insulation fault location (40) on an electric conductor (11) of a subsea supply line (10), which comprises an outer casing (9) having through bores (30), comprising the method steps: applying electric voltage to ground at the electric conductor (11), an electrochemical reaction taking place at the insulation fault location (40) between a metallic conductor material of the electric conductor (11) and the seawater (5), said electrochemical reaction forming gas, said electric voltage being formed by a modulated voltage impulse sequence, capturing gas bubbles (28) exiting from the through bores (30) of the outer casing (9) by optically sampling immediate surroundings along the subsea supply line (10) using an image capturing system (38), evaluating image patterns for identifying a gas-bubble image pattern and for determining the insulation fault location (40).

6. The method according to claim 5, characterized in that the image patterns are evaluated and the gas-bubble image patterns are identified by calculating a correlation of the applied voltage impulse sequence with a captured gas-bubble image pattern.

7. A locating system for determining an insulation fault location (40) on an electric conductor (11) of a subsea supply line (10), which can be filled with seawater (5), comprising a voltage generator (14) for generating a modulated voltage impulse sequence, which is grounded to the electric conductor (11); comprising sonic sensors (18), which are installed at predetermined locations along the subsea supply line (10) in order to capture sonic waves (20, 20c) propagating within the subsea supply line (10) in the seawater filling (7); and comprising an evaluation device (16) for evaluating measuring-signal impulse sequences supplied by the sonic sensors (18) for determining the insulation fault location (40).

8. A locating system for determining an insulation fault location (40) on an electric conductor (11) of a subsea supply line (10), which can be filled with seawater (5), comprising a voltage generator (14) for generating a modulated voltage impulse sequence, which is grounded to the electric conductor (11); comprising sonic sensors (18), which are installed at predetermined locations in the seawater (5) surrounding the subsea supply line (10) in order to capture sonic waves (20, 20a, 20b) emitted from the subsea supply line (10) outside of the subsea supply line (10); and comprising an evaluation device (16) for evaluating measuring-signal impulse sequences supplied by the sonic sensors (18) for determining the insulation fault location (40).

9. A tracking device for determining an insulation fault location (40) on an electric conductor (11) of a subsea supply line (10), which comprises an outer casing (9) having through bores (30), comprising a voltage generator (14) for generating a modulated voltage impulse sequence, which is grounded to the electric conductor (11); comprising an image capturing system (38), which captures gas bubbles (28) being formed at the insulation fault location (40) and exiting from the through bores (30) by optically sampling immediate surroundings of the subsea supply line (10); and comprising an image evaluation device (36) for evaluating image patterns in order to identify gas-bubble image patterns and to determine the insulation fault location (40).

10. The tracking device according to claim 9, characterized in that the image capturing system (38) and the image evaluation device (36) are configured as an integrated, autonomously navigating imaging system (39).

Description

BRIEF DESCRIPTION OF THE DRAWING FIGURES

[0035] Further advantageous embodiments of the invention can be taken from the following description and the drawings, which explain preferred embodiments of the invention by way of example. In the figures,

[0036] FIG. 1 shows a schematic overview display regarding the invention's field of application,

[0037] FIG. 2 shows a schematic display of the first locating system according to the invention,

[0038] FIG. 3 shows a schematic display of the second locating system according to the invention, and

[0039] FIG. 4 shows a schematic display of the third locating system according to the invention.

DETAILED DESCRIPTION

[0040] FIG. 1 shows the invention's field of application in a schematic overview display. A unit 2 of an oil or gas field on the bottom 4 of the sea is supplied with electric energy, pressure pipelines and command information via subsea supply lines 10 originating from a central production platform 8 placed at the sea surface 6. The subsea supply line 10 comprises an electric conductor 11 for supplying current.

[0041] In the overview according to FIG. 1, an exemplary first locating system 12 resting upon the first method is shown, said locating system 12 originating from a subsea supply line 10 flooded with a seawater filling 7 and surrounded by seawater 5.

[0042] A voltage generator 14 and an evaluation device 16 of the first locating system 12 are arranged on the production platform 8. Sonic sensors 18 are connected to the evaluation device 16, said sonic sensors 18 being installed at predetermined locations along the subsea supply line 10.

[0043] These sonic sensors 18 capture sonic waves 20, which propagate directed within the subsea supply line 10 in the seawater filling 7 originating from an insulation fault location 40 on the electric conductor 11 in this display (first method and first locating system 12, respectively).

[0044] FIG. 2 is a schematic display of the first locating system 12 according to the invention.

[0045] The locating system 12 comprises the voltage generator 14 for generating electric voltage to ground, which is applied to the electric conductor 11 of the subsea supply line 10, as well as the evaluation device 16 and the sonic sensors 18 arranged outside of the production platform 8.

[0046] The subsea supply line 10 flooded with a seawater filling 7 is shown in cross section 24, the electric conductor 11 being shown in the subsea supply line 10 (along with two other conductors 26), an insulation fault 40 having occurred on the electric conductor 11.

[0047] Sonic waves 20, 20c propagate directed from the insulation fault location 40 due to gas bubbles 28 forming in the seawater filling 7 of the subsea supply line 10. These sonic waves 20, 20c are captured by sonic sensors 18, which are installed directly on an outer casing 9 of the subsea supply line 10 along the subsea supply line 10. Measuring-signal impulse sequences provided by the sonic sensors 18 are forwarded to the evaluation device 16 in order to determine the insulation fault location 40.

[0048] FIG. 3 shows a schematic view of the second locating system 22 according to the invention.

[0049] Like the first locating system 12 (FIG. 2), the second locating system 22 comprises the voltage generator 14 for generating electric voltage to ground, which is applied to the electric conductor 11 of the subsea supply line 10, as well as the evaluation device 16 and the sonic sensors 18 arranged outside of the production platform 8.

[0050] In this case, the sonic waves 20 generated in consequence of gas bubbles 28 forming in the seawater filling 7 at the insulation fault location 40 on the electric conductor 11 and propagating outside of the subsea supply line 10 are captured using sonic sensors 18. The sonic sensors 18 are thus not directly arranged on the outer casing 9 of the subsea supply line 10 but can rather be installed at some distance to the subsea supply line 10 at suitable locations. Preferred sonic sensors 18, for example, could be highly sensitive microbarometers.

[0051] Should the outer casing 9 of the subsea supply line 10 be interspersed with through bores 30 (in order to reduce buoyancy and to simplify installation), then not only would the sonic waves 20a transmitted indirectly via oscillations of the outer casing 9 be directly captured but also the sonic waves 20b emitted by the through bores 30 would be directly captured as well.

[0052] FIG. 4 shows a schematic view of the third locating system 32 according to the invention.

[0053] The third locating system 32 comprises the voltage generator 14 for generating an electric voltage to ground, which is applied to the electric conductor 11 of the subsea supply line 10, as well as an image evaluation device 36 and an image capturing system 38 arranged outside of the production platform 8.

[0054] When using this third locating system 32, a subsea supply line 10 is presumed, whose outer casing 9 comprises through bores 30 and is thus flooded with seawater 5.

[0055] In order to capture the gas bubbles 28 exiting from the through bores 30, the immediate surroundings along the subsea supply line 10 are optically sampled (scanned) using a movable image capturing system 38. The captured image patterns are evaluated in the image evaluation device 36 in regard of a congruence with typical gas-bubble image patterns impressed by the modulated voltage impulse sequence.

[0056] The image capturing system 38 and the image evaluation device 36 can be realized as an integrated and autonomously navigating image processing system 39, which samples the subsea supply line 10 and tests whether expected gas-bubble image patterns occur.

[0057] When gas-bubble image patterns have been identified, the capture location belonging to the gas-bubble image pattern can be communicated as the insulation fault location.