WO2010052126A1

WO2010052126A1 - Method for measuring temperature and/or pressure at a pipeline, particularly in the offshore area of oil and gas extraction plants

Info

Publication number: WO2010052126A1
Application number: PCT/EP2009/063773
Authority: WO
Inventors: Thomas Bosselmann
Original assignee: Siemens Aktiengesellschaft
Priority date: 2008-11-06
Filing date: 2009-10-21
Publication date: 2010-05-14
Also published as: DE102008056087A1

Abstract

The invention relates to a method for measuring temperature and/or pressure at a pipeline, particularly in the offshore area of oil and gas extraction plants, and an associated device. If the pipeline is electrically heated, electrical energy must be transmitted to the extraction line. Optical fibers are guided on the pipeline for the purpose of measuring temperature and/or pressure. The optical fibers comprise individual sensors on the pipeline in a decentralized manner and can be supplied by an external Bragg unit (110). The measurement signals are centrally evaluated.

Description

description

Method for measuring temperature and / or pressure on a pipeline, in particular in the offshore area of oil and gas production facilities

The invention relates to a method for measuring temperature and / or pressure on a pipeline, in particular in the offshore area of oil and gas production facilities. In addition, the invention also relates to the associated apparatus for carrying out the method.

Offshore platforms are constantly expanding their radius towards so-called satellite oil fields, which are up to several tens of kilometers, currently about 10 to 15 km, from the platform and tap holes. The oil production pipes to these remote production sites run along the borehole on the seabed. The pumped medium, crude oil in the form of normal viscosities 40 API or heavy oils to API20 or mixtures of the above-mentioned crude oils with mitgefördertem

Water or gas is pumped into metal piping with a typical diameter of 6 "(about 152 mm) to 12" (about 305 mm) to the platform. Over the length of the pipeline, the medium cools down and, under the prevailing pressure and temperature conditions, the pipes become covered by deposits of paraffins or for the formation of methane hydrates, which hinders the flow.

The promotion distinguishes between typical oil qualities such as Brent or WTI (West Texas Intermediate)

- Normal operation: At the borehole temperatures up to 150 ⁰ C are found. Through the pipeline transport cools the medium to z. B. 5 ⁰ C from, which almost corresponds to the surrounding seawater temperature. - Restart after delivery stop: The entire length of the pipeline is filled with the pumped medium and is at seawater temperature level. As a rule, no more than 48 hours should elapse in order to warm the medium to 20 ... 25 ° C, so that a sufficient flow again comes about.

For heavy oils are higher transport temperatures than 25 ° C, z. B. 50 ... 70 ⁰ C, desirable. The pipes are therefore either heated or chemicals are metered in at the delivery point. The temperature and pressure should be recorded along the length of the pipeline, preferably independent of cables.

For long pipes under water, with z. B. electrical cables to be heated, the electrical protection of the cable or the pipe is not solved. In seawater, wireless data communication with high frequency is out of the question, and locally applicable ultrasound is too time-consuming. The sensor should work independently.

In most cases, a thermal image of the pipeline is calculated in the computer calculated. This is based on a temperature at the borehole (eg 150 ⁰ C) and the incoming flow on the platform is quite easy to measure.

It is possible to distribute wired sensors along the pipeline. It must be ensured in particular for auxiliary power. Furthermore, the temperature signal must return to the platform in a suitable manner. With conventional methods of cabling and over the distance of several kilometers under water, this can not be achieved with known technologies.

On this basis, it is an object of the invention to provide a method by which the temperature and / or pressure of an extended over longer areas pipeline can be detected. For this purpose, an associated device is to be created. The object is achieved by the measures of claim 1. An associated device is specified in claim 15. Further developments of the method and the associated device are the subject of the dependent claims.

The invention relates to the use of a fiber optic system (DTS, FBG), which has a protective sheath and rests against the metallic pipe. There are cases, for example when the pipe is inductively heated, that the protective sheath of the optical fiber must be non-metallic. In the case of the offshore version, a system is advantageous which has its light source and evaluation unit on the platform.

The system can be a so-called distributed temperature measuring system - DTS -, which is based on Raman spectroscopy. A further advantageous variant uses multiplexed fiber Bragg gratings (FBG). A fiber Bragg grating can be placed on the track and measure with pinpoint accuracy. Furthermore, FBG can measure both temperature and strain. From the literature arrangements are known which with the aid of z. B. Barometer cans measure pressure as strain.

In this way, a sensor cable can be realized, which depending on the application dialing and has alternating temperature and pressure measuring points.

For an FBG system, the grids must be mounted in a special arrangement: temperature sensors must be mounted stress-free, while pressure sensors need to be precisely straightened for strain. It is therefore conceivable to segment the sensor cable, transmission pieces are used for the pure transmission of optical sensor signals, in between sensor pieces are incorporated, which contain the sensor. These can be designed as splice boxes. For the Temperature sensor has the advantage that it can bring it directly to the ground and thus in good contact with the measuring object. The rest of the cable can thus a simpler structure such. B. have a conventional submarine cable.

For the latter reason, a DTS for outdoor installation is not advantageous because the sensitive optical fiber is located in a usually thick cable sheath. This is known to have a low thermal conductivity. Outside there is a gradient between the heated pipeline housing and the much cooler water. But it is necessary a good thermal contact with the pipe wall.

Preferably, the tubing has thermal insulation which includes the optical fiber of the fiber optic (FO) sensor. Thus, the temperature on the wall of the pipeline despite plastic coating of the FO sensor can be very well detected, since the plastic coating is very thin in relation to the thermal insulation pipe. A temperature gradient is then minimal.

Within the scope of the invention, certain marginal conditions for range apply: DTS have typical operative lengths of 20 km. If this length is not sufficient, the range can be doubled by introducing a system from 2 sides. FBG systems consistently have stronger signals and thus a more favorable signal-to-noise ratio. Due to the multiplexing properties, measuring systems can be implemented for transmission lengths of considerably longer lengths.

To optimize the thermal contact, an arrangement that ensures a significantly better connection to the temperature can lead the sensor cable in the pipeline. The sensor cable is inserted via an additional flange. This arrangement has the advantage that the cable can be reliably sealed via the flange. The introduction can be done above the water level, ie topside. But also directly at the heating station. The cable must be oil resistant since In addition to oil and gas and water and particles are produced, hydrogen tightness and water resistance under high pressure to define. A temperature gradient is absent. Here, therefore, a DTS could also be used advantageously, since the poor thermal conductivity of a cable construction entails only a higher time constant.

The temperature monitoring system can also be used for a protection system. An electrical shunt no longer heats the back of a pipeline. This manifests itself in a drop in temperature. By the temperature sensors, the location of this shunt can be limited.

Further details and advantages of the invention will become apparent from the following description of exemplary embodiments with reference to the drawing in conjunction with the claims.

Each show in a schematic representation

1 shows a measuring device for an underwater pipeline with a fiber optic monitoring system,

2 specific means for temperature measurement and evaluation in a system according to FIG. 1, FIG.

Figure 3 to Figure 2 alternative method for measuring temperature within the pipeline, Figure 4 shows a perspective section of a pipeline with an associated inductor as a current transformer and an optical waveguide with Bragg sensors as

Temperature measuring device and Figure 5 shows a sensor arrangement with Bragg sensors at the bottom of

Arrangement.

In the figures, the same or corresponding elements have the same reference numerals. The figures are described below in groups together. In this case, in particular to the parallel patent application of the Applicant with the same Zeitrang and the term "method and apparatus for heating of pipelines" reference is made, where specifically the inductive heating described in detail below with reference to Figures 6 and 7 is realized.

In the figures 1 to 5 10 each mean an oil pipeline as a pipeline, which - for example, but not mandatory - to be conducted under water. In particular, when laying under water, the pipeline will cool to temperatures near 4 ° C. If the medium to be transported also cools down, it can lead to problems during production.

Such a pipeline should therefore be heated, including the medium transported in the pipeline, for which purpose different electrical heating methods come into question. In particular, such a device can be realized either as a resistive heater or as an inductive heater. Specifically for the inductive heating of such a pipeline, reference is made to the patent application cited above.

In connection with devices described therein, it is proposed to monitor the temperature and / or the pressure of the pipeline 10 at predetermined time intervals. In particular, it is desirable to measure the temperature of the pipeline 10 locally. In addition to the detection of the temperature and / or pressure signals, the measurement signals are to be evaluated and transmitted as measurement data to a central evaluation unit.

By way of example, in FIG. 1, an alternating current source 12 with a power supply line 13 for resistive heating of the pipeline 10 is combined with a so-called Bragg unit 110 and an associated optical waveguide 11. The Bragg unit 110 is advantageously topside, ie on the oil platform outside the seawater. The optical waveguide 11 is in thermal contact with the pipe and can be used for locally distributed temperature measurement on the pipeline.

In some cases, pipelines laid at the bottom of the sea can be very long, so that a "topside" supply of the correspondingly long optical waveguide becomes problematic In such cases it may be favorable to use two optical waveguides 11, of which one optical waveguide 11 1 is connected to and supplied from the Bragg unit 110 arranged on the platform The other optical waveguide 11 'is guided under water from the borehole along the pipeline 10. The signal transmission takes place in this case by means of a known PLC (Power Line Communication ) Methods.

In FIG. 2, units 31 to 33 for power supply 1, for current measurement and for PLC modulation are given by way of example in an arrangement according to FIG. A Bragg unit 110 'is arranged to operate the sensors under water. All units 31, 32, 33 and 110 'are arranged in a watertight housing and optionally shielded against electrical influences from the power line 13.

The signals of the second optical waveguide 11 'are thus guided on the power supply line 13, decoupled via an inductive converter 51 and evaluated centrally in an external demodulation unit 50. The temperature sensors of the optical waveguide, which are distributed on the pipeline 10, are each assigned inductive transducers 31, voltage supply units 32 and modulation units 33 in a watertight housing 150. An external evaluation unit with demodulation unit 50 and inductive converter 51 is constructed in a known manner. For this purpose, reference is also made to the Applicant's co-pending patent application of the same time and entitled "Method for measuring the condition of a pipeline, in particular in the offshore area of oil and gas production plants, and associated apparatus and use of this device" (2008/21382) , The external Bragg unit 110, by which the optical waveguide 11 is driven, thus realizes temperature sensors distributed at periodic successive points of the pipeline 10.

In FIGS. 1 and 2, the energy supply unit is designed specifically in such a way that a resistive heating is realized, wherein the current or the electrical power is supplied via line 12 to the pipeline 10 and the pipeline 10 itself serves as a resistive resistor , Alternatively, an inductive heater is provided in FIG. 3, in which a line 15 as a closed current conductor loop ("loop") departs from a high-frequency generator 14 and a conductor branch runs parallel to the pipeline 10. In this case, the heating is carried out in this case necessarily made of metallic material tube formed by induced electromagnetic fields.

In the latter case it is also possible to introduce the optical waveguide of "topside" into the pipeline and to guide it within the pumped medium, provided that it is ensured that the pumped medium, for example oil, gas or multiphase mixtures with water does not damage the actual sensor Optical fiber in a, not shown in detail in the figures shown metallic or non-metallic protective cover.

3 shows a supply device 120 with a lateral "topside" flange 121 as inlet, which makes it possible to introduce the optical waveguide 11 into the pipeline, in addition to which there is a so-called splice box 130. The measuring points are in this case 111, 112, 113, .... It is advantageous in this case, in particular, that the actual measurements are not influenced by the electromagnetic fields of the induction heating. A section of the pipeline 10 with associated inductor line 14, optical waveguide 11 for temperature measurement and locally arranged housing unit 160 with evaluation means can be seen in FIG. In addition to the actual piping 10 with a predetermined cross-section and medium 8 to be transported, in particular oil or gas, and furthermore a thermal insulation 9, the inductor line 14 is indicated, which is connected via the inductive converter 31 with the evaluation unit located in the housing 160.

For optimized thermal connection to the pipeline 10, the optical waveguide 11, e.g. with Bragg sensors, guided inside the thermal insulation 9. This construction is also clear from the sectional view according to FIG. 5, in which the optical waveguide 11 is guided between components 161 of the housing 160.

Apart from a Bragg measuring unit, the temperature measurement can also be carried out by using a DTS (Distributed Temperature S_system) method based on Raman spectroscopy for the distributed temperature measurement.

Claims

claims

1. A method for measuring the temperature and / or the pressure on a pipeline, in particular in the offshore area of oil and gas production facilities,

- The pipeline is heated

- And wherein decentralized arranged on the pipeline, electrically operated measuring devices are used with sensors, characterized in that an optical waveguide is used as the sensor, which is guided parallel to the pipeline.

2. The method according to claim 1, characterized in that the heating of the pipeline is carried out electrically, for which electrical energy is transmitted to the pipeline and implemented as power for heating the pipeline.

3. The method according to claim 1, characterized in that the heating of the pipeline is made resistive.

4. The method according to claim 1, characterized in that the heating of the pipeline takes place inductively.

5. The method of claim 1, wherein the pipeline is guided under water, characterized in that the energy and / or supply lines are led to the heating under water at or near the pipeline.

6. The method according to claim 1, characterized in that are used for temperature measurement at the pipeline optical waveguide with at least one Bragg sensor.

7. The method according to claim 1, characterized in that the distributed temperature measurement over the entire pipeline length optical waveguide with periodically spaced Bragg sensors are used.

8. The method according to any one of the preceding claims, characterized in that the signals of the individual measuring devices via PLC (P _^ ower L_ine (Communication) are transmitted to the power line.

9. The method according to claim 1, characterized in that the decoupling of the supply energy from the power line and the coupling of the signals to the power line via inductive transducers.

10. The method according to claim 1, characterized in that over the entire length of the pipeline at least two measuring systems based on optical waveguides are used, each with arranged at periodic Bragg sensors.

11. The method according to any one of the preceding claims, characterized in that the measurement signals are read out as data in a memory unit.

12. The method according to any one of the preceding claims, characterized in that the measurement signals are coupled as data on the power supply line by means of PLC and are coupled to a central evaluation device.

13. The method according to any one of the preceding claims, characterized in that the optical waveguide is guided within the pipeline.

14. The method according to any one of the preceding claims, character- ized in that the Bragg sensor at the bottom of

Light guide assembly is attached.

15. Apparatus for carrying out the method according to claim 1 or one of claims 2 to 14, with a power supply unit connected to a central power line for transmitting electrical power for the purpose of electrical heating of the pipeline, characterized in that at predetermined intervals on the pipeline single - ne measuring devices with discrete sensors (11) are attached, which are assigned means (110, 31-35) for supplying energy on the one hand and for transmitting the measurement signals on the other hand.

16. The apparatus according to claim 15, characterized in that the power line is a power supply cable (13) for resistive heating of the pipeline.

17. The apparatus according to claim 15, characterized in that the power line is an inductor (14) for inductive heating of the pipeline.

18. The apparatus according to claim 15, characterized in that the inductor (14) forms a closed loop of Hinleiter and return conductor, wherein at least one of the conductors (Hinleiter or return conductor) on the wall of the pipe (10) is guided.

19. Device according to claim 15, characterized in that the energy supply unit (32) and the PLC modulation unit (33) are coupled to the return conductor of the inductor line (15).

20. The device according to claim 15, characterized in that the temperature measuring device comprises an optical waveguide with Bragg sensors (11, 110).

21. The device according to claim 15, characterized in that the Bragg sensor (11,110) contains distributed temperature measuring points

22. The apparatus of claim 15, wherein at least one Bragg sensor as optical waveguide (11) with associated evaluation unit along the pipe (10) is coupled.

23. The device according to claim 15, characterized in that the temperature measuring device forms an optical waveguide as a distributed temperature measurement (DTS).

24. The device according to claim 15, characterized in that the evaluation unit is coupled to a transducer to the power output and auxiliary power relates.

25. Device according to one of claims 15 to 24, characterized in that the evaluation unit (50) includes a data storage device for the acquired data, which are collected when the power supply cable (13) and the inductor (14) are not energized.

26. The device according to one of claims 15 to 25, characterized in that the evaluation unit includes an electrical energy storage, which supplies the supply unit for the sensors when the electrical line is not energized.

27. Device according to one of claims 15 to 26, characterized in that means for remote data reading are present.

28. The device according to one or more of claims 15 to 27, characterized in that there is at least one central evaluation device (50) having a decoupling unit with subsequent demodulation unit for the on the power supply cable (13) and the inductor line (15) transmitted PLC Contains signals.

29. The device according to claim 15, characterized in that the central evaluation device (50) in the vicinity of the power supply device (12, 14).

30. The device according to one or more of claims 15 to 29, characterized in that the optical waveguide (11) is guided in a metallic enclosure.

31. The device according to one or more of claims 15 to 30, characterized in that the optical waveguide is guided in a non-metallic envelope.