Pipeline Hazard Identification by Enhanced Use of Existing Data Communication Cables
a report by
Norman Sanderson1 and Andrew Strong2 1. BP Exploration; 2. Schlumberger
The use of fibre optic cables for control and data communication is now a common feature of many onshore pipelines. Often, these cables are only partially utilised and contain a number of spare optic fibres. This article describes how spare fibres could be used to monitor the pipeline for threats from external activities, whether malicious or accidental in nature, and to provide a means of monitoring a gas pipeline for leaks below the threshold of flow-based leak detection systems.
Background
Loss of integrity of onshore pipelines tends to be due to either external interference or corrosion. The development of in-line inspection tools has substantially reduced the likelihood of corrosion-related failures by identifying corrosion growth early and allowing timely mitigation.
External interference is managed in various ways, such as with public awareness activities, one-call arrangements to notify the operator of pending ground works and regular surveillance from aerial and ground patrols. However, none of these provisions provides continual coverage to identify the external threats to a pipeline. Because of this, considerable attention has been given to the development and use of leak detection systems based on either process monitoring or external detection of the leaked fluid.
The premise for this article is the need to be able to identify external threats and intervene before they cause contact with the pipeline and loss of integrity.
Fibre Optic System
Over the last six years, BP and Schlumberger have collaborated on the development of a fibre-optic-based system to simultaneously monitor the external threats to onshore pipelines and provide leak detection in gas pipelines. Marketed by Schlumberger, the Integriti Platinum system simultaneously measures temperature, strain and ground-borne vibration in a distributed manner along a fibre optic cable. This combination of measurments enables the operator to detect, locate and identify the following scenarios up to 100km from the interrogating instrument that is continuously monitoring the cable:
•
• •
multiple activities close to the pipeline, such as a person walking or digging, a car moving or an excavator idling, moving or digging; gas leaks by both acoustic and thermal effects; and ground movements using a purpose-designed cable.
The cable is buried in the ground above the pipeline. If an event is detected, it is recognised and located to within 10m.
Conventional fibre optic systems tend to have a limiting range of up to 40km. The Integriti Platinum fibre optic system has a novel optic
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A feature of the system is the development of a fibre optic cable without metallic content, capable of stretching to follow the shape of the ground, straining the fibre and thereby identifying potential hazards due to ground movement.
The final Integriti Platinum system is a toolbox of components that can be selected to meet the surveillance needs for a given application. In a new pipeline project, the full capability of the fibre optic system can be implemented. However, in the case of existing pipelines this may be difficult to accomplish because of the risk of damage to existing facilities from the installation of a fibre optic cable above the original pipeline. In many cases, retrofitting a fibre optic cable may be limited to installation of a relatively short length of cable in a high-consequence area to monitor encroachment (permanent) or civil earthworks (temporary) in the vicinity of the pipeline.
However, there is a further option available to operators of existing pipelines where, during construction, a fibre optic cable was installed in the pipeline trench for control and data communication.
© TOUCH BRIEFINGS 2010
• man walking or digging; • horse patrol; • passing vehicles; •
• fence-post installation; •
• gas leaks.
As ground conditions and threats are unique to any given pipeline section, the commissioning of the fibre optic system in a new installation will involve simulations of events to tailor the recognition routine for the application.
The development of the fibre optic system was subject to comprehensive field trials in the UK by BP during 2007 and 2008. Reference 1 provides a detailed description of the field trials. This work was followed by comparative trials against other fibre optic systems in European Gas Research Group (GERG) joint industry projects.
amplification system that increases the range to 100km. The system uses laser power transmitted through optic fibres to power optic amplifiers deployed along the route to be monitored, thereby avoiding the need for external electrical equipment in the field.
A major capability of Integriti Platinum’s data processing is the ability to recognise events and the level of threat involved. During field trials and subsequent operations, a comprehensive library of events has been compiled, including:
excavator idling, travelling or digging; pig travelling through the pipeline; and
Subsea & Pipelines
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