Paper world pipeline v4

WORLD PIPELINE MAGAZINE

MEXICAN PIPELINE MAPS AND DATABASE UPDATE WITH STATE OF THE ART PIPELINE DETECTION AND GLOBAL POSITIONING SYSTEMS Running under Mexican ground, there are more than 40,000 km of pipelines whose documented routes do not correspond to their real localization. In some cases, differences of up to 250 meters can be found. This has been a source of concern for Mexican pipeline integrity administrators, who can’t make reliable risk analysis without accurate information about the pipelines they are taking care of and for fast respond maintenance teams who lack trustworthy information like depth and distribution of pipelines in a Right of Way (ROW).

PEMEX Gas and Basic Petrochemistry (PGPB), a petrochemical unit of Mexico’s state-owned oil company, has made efforts to update its pipeline maps using state of the art detection equipment coupled with differential global positioning systems (DGPS) which they integrate into a geographic information system (GIS). This results in accurate digitized pipeline maps that can interactively link to different databases storing photographs, pipeline ROW cross sectional diagrams, corrosion risk parameters, and more, providing a powerful tool to risk managers, process engineers, cathodic protection system designers etc.

ACCURATE PIPELINE LOCATION AND TRACING IS BASIC FOR EMERGENCY RESPONSE, SAFETY AND INTEGRITY MANAGEMENT Knowing the exact localization of pipelines is critical for many tasks associated with pipeline management. For example, in 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 ROW. This is also true for third party excavation works like water, communication and power lines installation. Without accurate maps, 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 installations.

DIFFERENTIAL GPS AND OMNIDIRECTIONAL PIPE LOCATION EQUIPMENT PROVIDE SUBMETRIC COORDINATE AND DEPTH PRECISION. 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 pipeline 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).

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Figure 1.

PGPB owns over 13066 Km of gas transmission pipelines as shown in the map of Mexico. Currently PGPB has upgraded the location and tracing of approximately 63 % represented by the red lines. This project will continue in 2009 performing about 1,000 Km in the north of Mexico (yellow 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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Pipeline tracing campaigns usually require one or more teams of 4 technicians each. 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 a 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.

The detection procedure is performed at different points 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 the next desired detection point (usually every 500 meters) to continue with the pipeline tracing. Besides characterizing the ROW at regular length intervals, each time the team encounters pipeline service installations like rectifying stations, cathodic protection systems, etc, 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, 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. 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 voltage probes 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 corrosion potential probes 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 which can have mean errors around 30 meters1. The accuracy of the DGPS depends mainly on the number of “visible” GPS satellites. Physical obstacles between satellites and the DGPS antenna like clouds,

1

Jesús Cea Avión, http://www.jcea.es/artic/gps-precision.htm

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buildings, trees, canyon walls, etc., can block GPS signals reducing the number of satellites available. But studies made to determine the measurement error of the DGPS that was employed during the localization campaigns have shown that the probability of finding a pipeline inside a 1 meter radius around the measuring point is more than 83% in bad weather conditions and more than 98 % in a clear, sunny day. The probability distributions in figure 4 illustrate this point.

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 more than 83% in bad weather conditions and more than 98 % in a clear, sunny day. In comparison, the GPS data obtained from (1), presented a 5.3 % probability of localizing the GPS device inside a 1 meter radius around the measuring point.

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

776 m 1021 m

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 updated paths is far from negligible. It is evident that, given the inaccuracy of the old trace, without the proper localization of the pipelines, it would be quite difficult to make decisions on any action related to the pipeline ROW; would it be maintenance, urban development, emergency responding, or any other. Many decisions made based on inaccurate maps have lead to many maintenance and third party related incidents causing severe damage to one or more pipelines.

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, etc (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 make quick decisions in order to prevent further damage to the pipelines and installations

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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 make better planning, cost estimation and risk identification.

Cross section

Figure 6.

The SIIA integrates pipeline maps with documents like cross sectional diagrams of the ROW and interactive 360Âş photographic compositions of surface assets.

The SIIA is also a vast source of information for PGPB’s Integrity Management Program (IMP) which is an Integrity Management System (PIMS) that delivers risk assessments taking into account an enormous amount of factors including length of the pipelines, number of valves, 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 is 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 for cathodic protection system (CPS) designers, to obtain data from the SIIA in order to use it 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 system. If, for example, additional sacrificial anodes should be installed, a model can predict the corrosion potential profiles along the pipeline when these anodes are introduced into the model, allowing designers to determine an optimal anode distribution. This is particularly useful in areas with multiple oil and gas exploiting sites, where pipelines tend to have a lot of subdivisions and are electrically connected to other pipelines in order to share sacrificial anodes. In such situations, determining a correct anode distribution would be almost impossible without software simulations.

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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, codes, etc, is not a small feat. Fortunately for PGPB, for them, all this is done automatically thanks to smart document templates, cleverly designed databases, and quite a few home-developed subroutines. This way, information remains well organized and man-hour requirements are minimized (figure 8).

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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, 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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