Paper world pipeline v9

WORLD PIPELINE MAGAZINE

PEMEX GAS PIPELINE ROW AND DATABASE UPDATE WITH STATE OF THE ART PIPELINE DETECTION AND DIFFERENTIAL GPS Authors.

Víctor Domínguez and José Luis Mora Mendoza, PEMEX Gas y Petroquímica Básica, México City.

Arturo Godoy Simon, Jorge Canto Ibáñez, Lorenzo M. Martinez de La Escalera, Leonardo de Silva Muñoz and Lorenzo Martinez Gómez, Corrosión y Protección Ingeniería, Cuernavaca, México.

Running under Mexican ground, there are more than 60,000 Km of pipelines whose documented routes were to be updated. Before the present study, the geographical information, in many cases, was more than a decade old where differences between the actual position and the documented coordinates of some pipeline sections were greater than 1000 meters 1.

PEMEX Gas y Petroquímica Básica (PGPB), the main gas processing and transmission company of Mexico, has made efforts to update its pipeline maps using state of the art detection equipment coupled with differential global positioning systems (DGPS) which are integrated into a geographic information system (GIS). This results in accurate digitized pipeline maps that are interactively linked to different databases storing photographs, pipeline ROW cross sectional diagrams, corrosion risk parameters, and more, providing a powerful tool to risk and process engineers, cathodic protection system designers and general pipeline integrity managers.

ACCURATE PIPELINE LOCALIZATION AND TRACING IS BASIC FOR EMERGENCY RESPONSE, SAFETY, AND INTEGRITY MANAGEMENT Knowing the exact localization of pipelines is critical for many tasks associated with Internal and External Corrosion Direct Assessments (ICDA and ECDA) and general pipeline integrity management2,3,4,5. For example, in the case of maintenance works where a pipeline section must be substituted, before excavating, engineers must know exactly where and how deep the pipeline of interest goes as well as where does the rest of the pipelines lie if there are others that share the same ROW6,7,8. This is also true for third party excavation works like water, communication and power lines installation9. Without accurate location data, the risk of accident occurrence is considerable. Reliable pipeline maps are also crucial for emergency response to acts of terrorism, vandalism, accidental damage or any other incident that could compromise the integrity of a pipeline and its service installations10.

DIFFERENTIAL GPS AND OMNIDIRECTIONAL MAGNETOMETRIC PIPE LOCALIZATION EQUIPMENT PROVIDE SUBMETRIC COORDINATE AND DEPTH PRECISION.

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WORLD PIPELINE MAGAZINE PGPB has already traced more than 8200 km of pipelines, with state of the art localization systems that allow high accuracy position and depth determination of underground pipelines and cables (figure 1). The equipment consists in an adjustable frequency electromagnetic signal transmitter, an omnidirectional magnetic field sensor (OMFS), a personal digital assistant (PDA), a DGPS and a central processing unit that merges them all into a full system (figure 2).

Figure 1.

PGPB owns over 13066 Km of gas transmission pipelines as shown in the map of Mexico 1. Currently PGPB has upgraded the location and tracing of approximately 63 % represented by the pink lines. This project will continue in 2009 performing about 1,000 Km in the north of Mexico (orange lines). The rest, about 30 % of PGPB pipelines, is to be worked in the following years.

Figure 2.

A team led by a certified pipeline location and tracing engineer employed top of the line omni-directional magnetometers, differential GPS of sub-metric precision and portable data management devices.

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WORLD PIPELINE MAGAZINE Pipeline tracing campaigns usually require one or more teams of 4 technicians each supported by a GIS processing team at the cabinet. Each team has its own set of detection equipment and is responsible for mapping a certain pipeline section. The detection procedure begins by placing the signal transmitter on the ground and then emitting an electromagnetic signal towards the buried pipeline or cable. The electromagnetic signal induces an electrical current that flows along the pipeline generating a magnetic field that can be detected by the omnidirectional magnetic field sensor (figure 3.a). The sensor, which is operated at least 20 meters ahead of the transmitter, can accurately detect the magnetic field intensity variation as the operator moves around the pipeline ROW. By measuring the magnetic field intensity, the device can accurately detect the pipeline depth and position in the ROW in real time, as well as pipeline branches, direction changes and electrical bonds.

Every 500m the pipe detection procedure is performed along a path perpendicular to the direction of the pipelines until every pipeline and cables inside the ROW are localized. Then, the team moves along the ROW to continue with the pipeline tracing. Besides characterizing the ROW at regular length intervals, each time the team encounters pipeline service installations like rectifier stations and cathodic protection system components, the ROW is characterized, coordinates and installation data are registered, and photographs are taken. This is also made when there is an invasion of the right of way (ROW) by walls, fences, and houses, and each time the ROW crosses rivers, roads, railroads, and canyons. Thus, the campaign not only corrects pipeline maps, but also updates the pipeline asset inventory, particularly the real pipeline network length, and generates valuable risk management data.

DETECTION SYSTEM OPERATOR EXPERTISE IS A MUST. UNDETECTED PIPELINE CHANGE OF SIDES INSIDE THE ROW HAVE CAUSED SEVERE ACCIDENTS DURING MAINTENANCE AND REPAIRS Using state of the art equipment mentioned above helps determining accurate pipeline paths in a fast and reliable way; however, operator expertise is a must since some detection problems may arise with pipelines that are electrically connected to each other, pipelines that change positions inside the ROW crossing each other, or pipelines that run too close together 6. In such cases, an inexperienced operator may find himself with fewer pipelines than expected or with inconsistent readings. The basic problem that arises in these cases is that the magnetic field emitted by the pipeline gets distorted, making it difficult to determine the real depth and position of the pipeline (figure 3.b). Nevertheless, these particular difficulties can be overcome by connecting directly to the pipelines by the test stations that are periodically positioned along the ROW (figure 3.c) or by making additional localization procedures between the current position and the last correct characterization, until the cause of the magnetic field distortion is elucidated.

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a)

b)

c)

Figure 3. a) Equipped with an omnidirectional precision magnetometer the detection team sweeps the ROW perpendicularly to detect all the pipelines in the ROW. b) Skilled operators avoid usual errors caused by magnetic distortion in shortly separated pipelines, pipeline crossings, and other. c) Connecting directly to the pipeline using installed test stations can usually avoid magnetic distortions

Each time a pipeline position and depth are obtained, the data is stored in a database along with the coordinates obtained from the DGPS that the magnetic field sensor operator carries on his back. It is worth noting that the DGPS used, can determine global coordinates (latitude and longitude) in real time and with sub-meter precision, which contrasts with ordinary GPS where localization errors are usually greater than 10 meters 11,12.

Studies were made to determine the measurement error of the DGPS that was employed during the localization campaigns. Accuracy of GPS technologies has improved significantly along the present decade. The precision of differential GPS was improved to the sub-metric range and was used in the PGPB projects. A soccer stadium was marked to set a grid of 10mX10m separated points over a green area of 60mX100m. The GPS differential equipment was used to locate each

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WORLD PIPELINE MAGAZINE point of the grid, and the distances between points were calculated from the measured GPS coordinates. The relative distances between points were compared to the actual distances measured directly, and the absolute differences were registered, finally the difference distribution was plotted as shown in Figure 4. As shown, 97.6 % of the points had an error below 1m; meanwhile, data from the literature produced in 2005 11 shows a much wider distribution having 98.2 % of the data with a localization error below 40m.

Figure 4.

With the accuracy of the DGPS employed, the probability of finding a pipeline inside a 1 meter radius around the measuring point is about 98 %. In comparison, the GPS data obtained from (1), presented a 98 % probability of localizing the GPS device inside a 40 meter radius around the measuring point.

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THIRD PARTY RELATED INCIDENTS HAVE BEEN COMMONLY CAUSED BY THE INACCURATE PIPELINE LOCATION INFORMATION

Figure 5.

The upgraded pipeline tracing was helpful in correction of errors of the positioning of a pipeline of over 1000 m.

Pipeline tracing impact on a pipeline map can be quite important. An example of this is shown in figure 5 where the difference between the old and the updated paths is far from negligible.

THE INFORMATION OBTAINED DURING THE PIPELINE LOCALIZATION CAMPAIGNS WAS UPLOADED TO PGPB’S ASSET MANAGEMENT SYSTEM: THE SIIA Besides the obvious benefits of having accurate pipeline maps, the work done in this project has given some key additional advantages for PGPB pipeline administrators. Basically there has been an integration of the pipeline paths with a GIS and with file databases in a system known as SIIA (Installation and asset identification system) that allows rapid and intuitive access to thousands of photographs, videos, maintenance reports, corrosion risk parameters, and any other information related to particular pipeline sections, rectifying stations, cathodic protection systems, road, river and railroad crossings, and the like (figure 6). These tools allow swift access to key information for emergency responders in case of accidents, vandalism and acts of terrorism, allowing them to take quick decisions in order to prevent further damage to the pipelines and installations involved and to guarantee the safety of the local population. They are also very useful for project engineers and maintenance teams that need to know certain characteristics of the pipeline network on which they pretend to work, letting them do better planning, cost estimation and risk identification.

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Figure 6.

The SIIA integrates pipeline maps with documents like cross sectional diagrams of the ROW and interactive 360º photographic compositions of surface assets (distance units are meters).

The SIIA is also a vast source of information for PGPB’s Integrity Management Program (IMP) which is a Pipeline Integrity Management System (PIMS) that makes risk assessments taking into account an enormous amount of factors including length of the pipelines, number of valves, in-line inspection, corrosion potentials, maintenance status of every asset of the pipeline networks, operating temperatures and pressures, etc. The more information available, the more reliable the risk assessment, which in turn, becomes an invaluable tool for Pipeline Integrity Managers.

Yet another example of the impact that SIIA has on PGPB’s Pipeline Integrity Management, is the ability of cathodic protection system (CPS) designers to obtain data from the SIIA in order to use it

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WORLD PIPELINE MAGAZINE in CPS design software where they can construct color coded maps of corrosion potentials along a particular pipeline network (figure 7), and develop models that can predict the behavior of the system13,14.

Figure 7.

Cathodic protection system engineers can benefit from the information available through SIIA for visualizing corrosion potential maps and for CPS modeling.

CUSTOM MADE DATABASES AND SOFTWARE WERE EMPLOYED TO UPDATE THE PGPB ASSET MANAGEMENT SYSTEM In a pipeline map update campaign, the amounts of information obtained from the field tasks team can become quite overwhelming. To organize and classify that information along with the creation of standardized documents that include some information elements like photographs, numbers and codes, is not a small feat. Fortunately for PGPB, all this is done automatically thanks to smart document templates, cleverly designed databases, and home-developed subroutines.

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WORLD PIPELINE MAGAZINE This way, information remains well organized and man-hour requirements are minimized (figure 8).

Figure 8.

Costumed made databases and automatic document generation allowed to document the assets of PGPB pipeline surface facilities and to upload the information into SIIA in a fast and reliable way.

PGPB’S MIDSTREAM PIPELINE MAP AND ASSET INVENTORY UPDATE HAS MANY ADVANTAGES THAT INVOLVE BETTER OVERALL PIPELINE INTEGRITY MANAGEMENT With pipeline maps updating campaigns using state of the art detection systems coupled with the SIIA, PGPB can be sure of having accurate pipeline maps that will help avoid future maintenance and third party accidents, and a modern, reliable, and cost-effective set of tools that allow quick and intuitive data availability for overall Pipeline Integrity Management, fast emergency response, better maintenance and cathodic protection system design, and a more complete asset inventory.

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References

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1

Pemex Gas y Petroquímica Básica (PGPB), Sistema de Identificación de Instalaciones y Activos (SIIA), unpublished data.

2

Jawhar I., Mohamed N., Shuaib K., “A framework for pipeline infrastructure monitoring using wireless sensor networks”, Wireless Telecommunications Symposium, 2007, pp 1-7.

3

McKay J.S., Biagiotti Jr., Hendren E.S., The Challenges of Implementing the Internal Corrosion Direct Assessment”, Corrosion 2003, NACE International, Paper 03185.

4

Peter Nicholson, “External Corrosion Assessment”, Pipeline Rehabilitation and Maintenance, Sept. 2006, Istanbul, Turkey.

5

Clever Pig Roots Through Pipes, The Institute of Petroleum, Petroleum Review Nov. 1989, p. 557.

6

Lukowski T.I., Power D., Yue B., Randall C.J., Youden J., Howell C. “Pipeline encroachment monitoring using polatimetric SAR imagery” Geoscience and Remote Sensing Symposium, 2004, IEEE International Vol. 1, p. 68.

7

Keifner J.F. et al. A review of In-line Inspection Capabilities”, Pipeline Safety and Leak Detection, PD-vol. 19, The American Society of Mechanical Engineers, 1988, pp. 29-40.

8

Defect Location and Sizing in a Transmission Pipeline is No Easy Task, vol. 88, May 7, 1990.

9

Stancliffe J., “Third party damage to Major Accident Hazard pipelines” http://www.hse.gov.uk/pipelines/ukopa.htm 10

Shelley Craig H., “Response to Pipeline Incidents” Fire Engineering vol. 160, Issue 11, Nov. 2007, pp 89-96.

11

Jesús Cea Avión, “Precisión del sistema GPS”, http://www.jcea.es/artic/gps-precision.htm

12

Adrados Christophe, “Global positioning System location accuracy improvement due to Selective Availability Removal”, Compte Rendus Biologies, Vol 325, Issue 2, Feb. 2002, p 165.

13

Adey R.A., Niku S.M., Brebbia C.A.,“Computer aided design of cathodic protection systems”, Applied Ocean Research, vol. 8, Issue 4, Oct. 1986, pp 209-222.

14

Kasatkin V.E., Gelman A.V., Zarepov A.I., Kasatkina I.V., “Computer Simulation of Cathodic Protection Systems for Branched Pipelines”, Protection of Metals Vol. 39, No. 3, 2003, pp. 268-273