PIPELINE REMOTE SENSING FOR SAFETY AND ENVIRONMENT THE PROJECTS CHARM AND PRESENSE

Transcription

1 1 3 rd European Forum Gas September 2005, Warsaw, Poland Block 4 New and Future Technologies PIPELINE REMOTE SENSING FOR SAFETY AND ENVIRONMENT THE PROJECTS CHARM AND PRESENSE Werner Zirnig, E.ON Ruhrgas AG, Dorsten, Germany Background E.ON Ruhrgas is Germany's leading gas company and the largest natural gas importer in Europe. It has a total gas send out of 640 billion kilowatt hours and operates a high-pressure gas transmission system totalling some 11,200 km of pipeline. This pipeline system covers the whole of Germany, providing the central link in the integrated European natural gas grid. Being the owner of such pipeline system, E.ON Ruhrgas is also responsible for monitoring the system as required by law. This is done by way of walking or mobile surveys or aerial inspections of the pipeline corridors by helicopters. While surveillance by air is the best way of preventing thirdparty interference and detecting gas-induced discolouring of the vegetation in the open country, pipelines below sealed surfaces in built-up areas can, with conventional technology, only be inspected by walking surveys involving the use of mobile gas detectors. While these inspections ensure a high level of safety for pipeline operation, they are also very expensive. Innovative technologies provide the key to making pipeline operations more efficient. This is why E.ON Ruhrgas teamed up with other European gas companies and technology experts to develop novel remote monitoring systems which can be employed to check natural gas pipelines. The format of this paper is to provide results of the two major projects CHARM (CH 4 Airborne Remote Monitoring) and PRESENSE (Pipeline REmote SENsing for Safety and the Environment). Operator requirements for pipeline monitoring Most pipelines in the E.ON Ruhrgas high pressure gas transmission network are under a soil cover of about 1 m and depending on pipeline diameter, a 4 m to 10 m wide ROW (Right-of- Way) is specified above the pipeline route. Buildings and large trees with deep roots are not admissible in these pipeline corridors. Work in the ROW is not admissible unless prior approval has been obtained from the pipeline operator. The monitoring tasks for these pipelines break down into object and situation detection to prevent third party interference, monitoring of soil movement and early detection of gas emissions. These monitoring tasks have to be carried out throughout the year at regular intervals, largely regardless of weather conditions. Although the areas monitored differ quite significantly in terms of soil characteristics, vegetation and building density, it is important for the monitoring methods employed to be usable in almost all types of terrain. The increasing availability of geographic information systems, whose digital map files contain exact information on pipeline routes, in combination with recent improvements in the positioning accuracy of satellite surveying systems like GPS offers new and efficient ways of pipeline monitoring: the joint use of digital maps and modern satellite surveying for the

2 2 navigation of helicopters in pipeline monitoring and gas leak detection allows automatic, unambiguous geographic allocation of the reported locations [1]. Ground vehicles using similar navigation equipment can then be directed to the locations recognised from the air without requiring much local geographic knowledge. This will enable the design of new highly flexible and efficient ways of looking after gas pipeline networks, allowing a swift and well-targeted response to any threats to gas transmission pipeline safety. However, the technological challenge is, that in terms of their price/performance ratio such new monitoring systems must at least correspond to the systems presently in use, or be better. CHARM - The E.ON Ruhrgas helicopter-borne gas detection system E.ON Ruhrgas teamed up with the German laser systems developer Adlares and the German Aerospace Centre DLR, an application-oriented research institution, to develop a novel, infrared laser light-based remote sensing system which when installed onboard helicopters used for routine aerial surveys can be employed to check natural gas pipelines for tightness, particularly in built-up areas. In combination with satellite positioning services and geographic information systems with digital maps containing detailed data on pipeline routes, this gas detection system, which is known as CHARM (CH 4 Airborne Remote Monitoring), stands a good chance of replacing the troublesome manual gas detection methods presently in use [2]. Figure 1. CHARM measurement system installed onboard a helicopter The measurement principle behind remote gas sensing The Differential Absorption Lidar (DIAL) principle employed for the development of CHARM is a laser light-based, active optical detection method used successfully worldwide for analysing trace gases in the earth s atmosphere. The Lidar (Light detecting and ranging) technique involves sending a laser light in the ultraviolet, visible or infrared spectral range and detecting and analysing the back-scattered light. Trace gas concentrations can be determined by tuning the laser wavelength to the spectral signature and the absorption characteristics of the gas to be measured. In order to eliminate atmospheric effects and backscatter onto the measurement signal, the DIAL method uses two wavelengths for transmission. The first wavelength (λ on ) is absorbed by the gas while the second (λ off ) is not absorbed and serves as a reference. The

3 3 radiation emitted by the laser is reflected by a topographic target and picked up by the measurement system s optical devices. The trace gas concentration determined is the value integrated over the measurement path, which is given in ppm m. Results Extensive laboratory tests were conducted to adapt the DIAL measuring method to the light scatter on the ground, to the use of the movable helicopter platform and to the main hydrocarbon in the natural gas, i.e. methane. This was followed by field tests under near-practical conditions to assess the performance range of that remote gas detection system. The tests showed that with an appropriately tuned DIAL system and measurement distances of around 150 m, the small gas flows of 0.05 m³/hr specified for this application can be detected. This makes the new method generally suitable for routine pipeline inspections by helicopter to check for tightness, allowing the mobile gas detectors used for walking surveys in built-up areas to be gradually replaced. Particular care was taken to ensure largely shock-free mounting of the special laser system and sufficient tempering of all electronic components. In addition, for measurement beam positioning onto the pipeline route, a series of control devices have been added to ensure that the measurement beam hits the pipeline corridor and that the effects of helicopter movement are compensated. Helicopter test flights proved that the new laser system is capable of detecting even small simulated natural gas escapes at standard altitudes ( m) and standard travelling speeds ( km/hr). If the pipeline co-ordinates are available as digital data, automatic beam positioning onto the pipeline corridor is possible. Otherwise, an operator on board uses a video image of the pipeline corridor at the computer screen to manually direct the scanning field of the laser beam onto the pipeline corridor. Facts and figures at a glance: CHARM offers remote natural gas detection during aerial survey by a small helicopter, particularly in built-up areas. Inspection altitude: 80 to 150 m Travelling speed: km/hr. Width of pipeline corridor covered: 18 m Automatic measurement beam positioning onto the pipeline route Entry of leak position into reporting system PRESENSE - The way of using satellite imagery for pipeline monitoring The co-funded European PRESENSE (Pipeline REmote SENsing for Safety and the Environment) project was a collaborative project of 17 partners that aimed to assess the potential benefits of remote monitoring techniques compared with conventional techniques [3]. PRESENSE, which started in January 2002 and was completed by September 2004, has advanced the potential of an automated remote monitoring system for pipelines from a concept to a demonstrated capability. Based upon remote satellite surveillance, and advanced information systems it is capable of alerting pipeline operators to potential pipeline damage. However, further improvements in image processing change detection software are still necessary to achieve this goal.

4 4 Optical and radar sensor technology for the monitoring of natural gas pipelines Today, both optical and radar systems are operated on airborne as well as space-borne platforms. Space-borne systems presently provide a geometric resolution on the ground of up to 0.6 m x 0.6 m for optical and 10 m x 10 m for radar systems, allowing imaging of strips with a width of 11 km and 50 km, respectively. Optical sensors are hindered by cloud cover, which, from an operational point of view, constitutes a substantial limitation of their use in pipeline monitoring. Conversely, radar sensors can be operated regardless of weather and light conditions and therefore have a much higher rate of availability, particularly in Northern Europe, which is frequently covered with clouds. Experimental optical and radar data The suitability of optical and radar sensors for the inspection of gas pipelines has been shown in demonstration flight campaigns in the PRESENSE project. Different objects (e.g. excavators) were placed on sites typical for gas pipeline surroundings, and three aircraft carrying respectively, multi-spectral optical, radar and Lidar sensors, each flew the test sites. After the observation of these scenarios with the airborne sensors, the objects were moved to different places, and data were taken for these changed scenarios. The excavators and their different appearance in the respective data sets can well be seen by eye inspection (Figure 2). All the data Figure 2. Pipeline scenario with excavator in operation on pipeline test site. In each image the position of the excavator is indicated by a white circle. Top: photo image (E.ON Ruhrgas) Upper left: airborne optical image (German Aerospace Centre DLR) Upper right: airborne infrared image (German Aerospace Centre DLR) Lower left: airborne radar image (Intermap Technologies) Lower right: airborne Lidar image (NPA Nigel Press Associates)

5 5 sets were subsequently geo-referenced and made available to the PRESENSE partners involved in developing the data processing chain. Promising results demonstrated that using an automatically operating feature extraction system, such as described below, this type of data can be processed to produce the correct alarms for cases of real threats to pipelines. Automatic feature recognition using object-oriented image analysis technology The combination of object identification and a semantic knowledge network appeared to be an image processing procedure which is especially well suited for pipeline monitoring. The commercial analysis system ecognition allows data from different sensors (i.e. optical and radar) to be merged for object identification [4, 5]. The ecognition method includes the identification and generation of objects from the original pixel-based files and the establishment of semantic links between these objects and known features, for example in the form of a feature database. Image features such as vehicles or pits are classified on the basis of radiometric, geometric and other links between the image objects and placed in relation to neighbouring objects and known information from geographic information systems (GIS). Any new objects detected near to the coordinates of a pipeline route could therefore be identified as potential hazards (Figure 3). By assessing the area concerned, assumptions can be made concerning a possible distinction between agricultural vehicles and construction equipment. Figure 3. Changes in radar and optical/infrared with added GIS information for location of change (e.g. on-road or off-road). Again the circle indicates the position of the excavator shown in Figure 2. Monitoring ground movement along pipeline corridors with interferometric radar Interferometric processing of satellite radar data is the analysis of phase differences between two or more images recorded from slightly different orbital positions. With the effects due to terrain elevation and atmosphere removed, these phase differences take the form of interference fringes. These correspond to the component of relative displacement of the ground surface along the satellite s line-of-sight and allow measurement of displacements to sub-centimetre or millimetre accuracy, according to the technique employed. The great benefit of these techniques is they can reveal slowly developing problem areas such as landslides or subsidence, which can only be detected with very great difficulty and expense by existing means.

6 6 Interferometric radar analysis (InSAR = Interferometric Synthetic Aperture Radar) currently can take three major forms: 1) Standard InSAR: Processing of the phase differences between individual image pairs for all image backscattered signal data. Consequently, standard InSAR can be used to provide relatively low-cost snapshots for scanning large areas for rapidly occurring, wide area ground subsidence, for example such as movements resulting from large area mining subsidence (Figure 4). 2) Persistent Scatterer Interferometry (PSI): Particularly in urban, developed and rocky environments, man-made and some natural features form strong reflectors of the satellite radar signal. By stacking many radar images (e.g. 15 or more), it is possible to identify and remove from analysis all features reflecting temporarily (vehicles etc) and retain naturally occurring reflector points which can be up to between 50 and 400 points per square km. A limitation of PSI is that very rapid movements (more than about 1 cm every 35 days) cannot be reliably measured. 3) Corner Reflector InSAR (CRInSAR): Radar reflectors (corner reflectors, or active transponders) can be used to provide a very strong return of the satellite s signal from a single point. This enables processing displacements between two or more images only at that specially constructed signal reflectors. However, a limitation of this technique is that reflectors need to be spaced within a few hundred metres of each other to differentiate ground movement from atmospheric effects, and need to have at least one reference reflector at a stable location. Figure 4. View of an area with mining induced ground movement: Radar interferogram overlain on satellite imagery shows three areas of rapid subsidence, up to 10 cm over 35 days (based on standard interferogrammetric processing by Tele- Rilevamento Europa TRE). Conclusions CHARM, an innovative remote methane detection system is now available for use on helicopters to allow routine inspections of natural gas pipelines even in built-up areas. The new technique

7 7 stands a good chance of replacing the troublesome manual gas detection methods presently in use. Moreover, the joint use of geographic information systems, whose digital maps contain detailed information on pipeline routes, and modern satellite navigation systems, which provide accurate position data, allow clear geographic allocation of the reported locations. Ground vehicles using similar navigation equipment can then be directed to the locations recognised from the air without requiring much local geographic knowledge. This opens up new, highly flexible and efficient ways of looking after natural gas pipeline networks. As a result of global progress in high-resolution remote sensing and image processing technology, it is now possible to design natural gas pipeline monitoring systems with remote sensors and context-oriented image processing software. PRESENSE has demonstrated the potential for utilizing such innovative remote sensing technologies and new image analysis software within the pipeline business. To gain future benefit from these advances there is now a need to develop commercially viable products. Additionally, recent developments in unmanned aerial vehicles (UAV) technology show the suitability of UAV as a platform for such monitoring systems based on remote sensing technologies [6]. Hence, in the near future UAV may provide an economic sensor platform for pipeline monitoring. Acknowledgements This summary of the CHARM and PRESENSE projects is a compilation of the papers [2] and [3], which first appeared in the IGRC 2004 conference proceedings. The author wishes to thank all the project participants, namely from the 16 PRESENSE partners Advantica (UK), British Geological Survey BGS (UK), BP Exploration Operating Company (UK), CS Systemes d Information (France), Definiens Imaging (Germany), Fluxys (Belgium), Gasunie (The Netherlands), Gaz de France (France), Intermap Technologies (Germany), Issquared (UK), NLR National Aerospace Laboratory (The Netherlands), Nigel Press Associates NPA (UK), TNO Physics and Electronics Laboratory (The Netherlands), University of Nottingham (UK) and Verbundnetz Gas VNG (Germany), as well as from the two CHARM project partners Adlares (Germany) and DLR German Aerospace Centre (Germany). The PRESENSE project has partly been funded in the 5 th EU Framework Programme for Research and Technological Development under EU-Contract No. ENK6-CT References [1] Zirnig, W.; Hausamann, D.; Schreier, G.: A concept for natural gas transmission pipeline monitoring based on new high-resolution remote sensing technologies. Proceedings 2001 International Gas Research Conference, Amsterdam, The Netherlands, November [2] Zirnig, W.; Ulbricht, M.; Fix, A.; Klingenberg, H.: Helicopter-borne laser methane detection system a new tool for efficient gas pipeline inspection. Proceedings 2004 International Gas Research Conference, Vancouver, Canada, November [3] Zirnig, W.; Pride, R.; Lingenfelder, I.; Chiles, R.; Hausamann, D.: The PRESENSE and PIPEMON projects defining the ways of using space-borne earth observation services for pipeline monitoring. Proceedings 2004 International Gas Research Conference, Vancouver, Canada, November [4] Definiens Imaging GmbH: ecognition User Guide. Munich, Germany, 2003

8 8 [5] Dekker, R.J.; Lingenfelder, I.; Brozek, B.; Benz, U.C.; Van den Broek, A.C.: Objectbased detection of hazards to the European gas pipeline network using SAR images. Proceedings of the 5th European Conference on Synthetic Aperture Radar (EUSAR), Ulm, Germany, May 2004 [6] Hausamann, D.; Brokx, W.: User Driven UAV Applications - Pipeline Monitoring and other Examples. Proceedings First European Conference on the Applied Scientific Use of UAV Systems, Kiruna, SW, June 2002 Contact Dipl.-Ing. Werner Zirnig E.ON Ruhrgas AG Safety/Fluid Dynamics Halterner Str Dorsten GERMANY Phone: Fax: werner.zirnig@eon-ruhrgas.com