The protection of oil, gas and refined product pipelines against sabotage, illegal tapping and terrorist action, combined with the detection of leaks and in-line equipment failure, is a high priority in all countries, but has been notoriously difficult to achieve.
Oil and gas installations are critical infrastructure of high importance and value. If a pipeline is damaged, significant revenues will be lost, harm may be caused to the environment, and the leakage could be a potential danger to the local population. More importantly, a terrorist attack on an unprotected pipeline could have catastrophic consequences.
This article describes how the latest developments in pipeline monitoring and security technology meet the challenges of today’s demanding environment. New sensing solutions provide greater visibility into the pipeline network and buy operators additional time before an event occurs, allowing for repairs, evacuations or a security response to reduce potential damage or losses.
A Vulnerable Network Of Strategic Assets
It has never been more important to ensure the safety and reliability of production and distribution assets for the oil and gas industry. In a fragile economy, threats to pipeline infrastructure can have a significant effect on both industries and communities, whether they are intentional disruptions or inadvertent damage caused by excavation equipment, land movement or pipeline leaks.
For pipeline operators, the three main types of third-party damage are theft, terrorism and construction work. Pipeline tampering and pilferage are common problems in developing countries. Pipelines are also an easy “soft target” for terrorist organizations whose declared aim is to damage Western economic and political interests.
A typical transportation and distribution system for natural gas or liquid hydrocarbons can extend hundreds of miles and comprise thousands of sensors, valves, pumps and controllers. In the United States, the national pipeline system is an extensive mode of transportation with unique infrastructure security characteristics and requirements. Virtually all the critical pipeline infrastructure is owned or operated by private entities. There are:
- 161,189 miles of hazardous liquid pipelines
- 309,503 miles of natural gas transmission pipelines
- 1.9 million miles of natural gas distribution pipelines
According to the U.S. Department of Transportation’s Office of Pipeline Safety (OPS), the majority of pipeline incidents are caused by “damage by outside force.” Property damages alone for more than 300,000 miles of transmission pipe can cost operators millions of dollars annually.
Limitations Of Existing Technologies
Most petroleum producers recognize the importance of deploying an effective pipeline monitoring and surveillance solution, which includes a round-the-clock vigil on key operational parameters in the distribution network, as well as monitoring leakages, electronic surveillance and physical patrolling of the right-of-way.
In a continuing effort to remove the guesswork from pipeline operations and reduce costs, many techniques have been developed to address risks and maintenance needs in a strategic fashion. Common pipeline security measures include aerial surveillance, ground patrolling, installation of pipeline warning boards/markers, deployment of security personnel, and conducting awareness campaigns to educate habitants along the pipeline route. Advanced telecommunication systems and leak detection systems are also widely used to improve the monitoring and remote control of pipelines.
However, armed security guards cannot be everywhere at the same time. Closed-circuit television (CCTV) security cameras are effective for surveillance, but are less useful if not incorporated into a complete security system. Plus, their infrastructure costs are not economically viable. Radar is proven as a long-range water and surface-based solution, but again, is not economically viable due to the need for power and network connectivity.
Most conventional pipeline security systems rely upon point-sensing technologies to estimate locations of events. Positioning these systems in the correct and most relevant locations can be a challenge. They can also be affected by a single large and often harmless event blinding the system to specific activities that can affect the process.
Overall, the majority of existing detection technologies only provide notice that a damaging event has occurred, allowing an operator to put into place reactive countermeasures to stop the associated costs from escalating.
Latest Pipeline Monitoring Solution
In recent years, innovative technologies for pipeline surveillance against third-party damage or intrusion have become increasingly available. With advances in miniaturized sensors, standardized data processing and reliable communications, oil and gas companies now have access to robust tools for the monitoring of extended and complex pipeline systems.
One of the most effective solutions for pipeline monitoring involves a technique known as Distributed Acoustic Sensing (DAS), which can convert a fiber optic cable into a listening device. A DAS system is designed to prevent pipeline damage from occurring in the first place by providing advance warning of the events leading up to an incident.
Attaching DAS equipment to one end of a standard fiber optic cable, such as those used for telecommunication, creates an acoustic array of virtual microphones every 10 meters along the fiber. Using sonar-processing techniques, the sounds received from the virtual microphones are analyzed and converted into a simple graphical display showing the operator what is happening along individual lengths of the fiber. For example, the sensor system can detect the difference between mechanical digging and a person walking. It can also pick up the sound of leaks from gas pipelines.
DAS systems are comprised of two key elements: an optical interrogator unit and an acoustical processing unit. The interrogator unit sends a pulse of light down the fiber optic line with most of the light reaching the other end. However, a small percentage of light returns to the source — this effect is called “backscatter.”
Sound or vibration near the fiber changes the backscattered light, and these changes are analyzed by the interrogator unit to re-create the sound or vibration that caused them. The sounds are sent to the acoustical processing unit, which analyzes the sounds using sonar processing algorithms to create specific alarms for a given event or sequence of events.
The passive nature and inherent long-term reliability of fiber optics, together with the ability to string together thousands of individual sensing elements in individual optical fibers, make DAS a compelling technology for meeting demanding pipeline monitoring and security requirements.
The most advanced DAS-based solutions are designed to perform acoustic sensing for pipeline condition monitoring and leak detection on the same strand of fiber, making them ideal for retrofit projects with existing cable installations. These systems can also cover up to 60 miles of cable between power and network connections.
Better Accuracy, Fewer False Alarms
As demonstrated at oil and gas pipeline facilities worldwide, DAS technology provides around-the-clock distributed acoustic monitoring over very long distances. Operators can monitor the entire length of the fiber optic cable continuously and detect, classify and locate any number of simultaneous disturbances anywhere along the fiber with excellent resolution. Most importantly, the signal extracted from each section of fiber is unaffected by the vibration on any other section.
DAS-based pipeline monitoring employs a processing architecture for analyzing acoustic activity that draws upon decades of military sonar research. This tells the operator what the threat is and eradicates false or nuisance alarms. The system interrogation unit automatically learns the normal background level of vibration along each section of fiber and then sets appropriate amplitude thresholds for each location. This enables the operator to locate any threat with a high degree of accuracy.
Detection ranges from the pipeline itself depend on the type of soil surrounding the fiber, but DAS can typically detect a person walking when they are 5-10 meters away from the buried fiber with manual digging 5-15 meters away. The technology can detect vehicles 5-15 meters away from the fiber and identify mechanical digging or other larger machinery at a distance of 20-50 meters.
Some systems even present real-time event data in a manner where classified alerts are shown on a map display with location coordinates. For long-distance applications, this capability is particularly beneficial for threat response and can be used to cue other security platforms such as CCTV or unmanned aerial vehicles (UAVs).
Integration of DAS technology with process automation systems, fire and gas safety equipment, plant security systems, and gas metering and regulation stations allows operators at different facilities to see alarms in parallel — in the same format — to provide additional time for evacuations or to avert a potentially life-threatening event.
Typical Industry Applications
DAS technology can be cost-effectively deployed on various types of pipeline systems to provide around-the-clock monitoring for threatening activity and abnormal operating incidents within the vicinity of the line and surrounding assets. Typical applications include:
With a DAS-based monitoring system, operators have a reliable means of locating potentially hazardous movement within the pipeline corridor. Human movement can be detected within a few feet of the sensing cable, and mechanical digging identified up to much longer distances. In many cases, this allows intrusion to be detected and alarmed before contact with the pipe is made.
The DAS solution can utilize the fiber optic network around remote facilities to detect any unwanted intrusion and protect assets such as block valves and compressor stations. In addition, it can be integrated with existing security systems to activate cameras and personnel. This can be monitored at a central control center overseeing a number of diverse locations.
A key feature of DAS is to provide alerts for real threats only. This technique not only picks out the acoustic fingerprint of an event, but also monitors its activity over a short period of time to build up an exact picture of what the event is. In this way, nuisance alarms are effectively minimized.
The use of “smart zones” allows for flexible alert settings to protect different regions (i.e., varying terrains such as roads and rivers) at different times of the day. For example, traffic on a road during the day may be no issue, but a vehicle arriving late at night, stopping, and unloading several people is quite different.
DAS technology is able to detect the low frequencies associated with a gas pipeline burst. Where gas leaks cause a change in the temperature around the fiber, the technology can provide early warning and avoid dangerous and costly delays in detection. The possibility of combining this capability with the detection of leaks that cause an acoustic impact around the fiber enhances the security function.
Pig tracking and profiling
DAS can follow the progress of a pig throughout the pipe network by tracking the acoustic signature. When a pig passes through a girth weld inline, the resulting pressure pulses propagate through the pipe, which can be picked up a considerable distance away. This allows the use of cleaning pigs to gain valuable data that help in constructing a picture of the pipeline’s condition over time and will also identify the location of a stalled pig.
Various pieces of pipeline equipment (especially those with rotating parts such as pumps, valves or generators) produce strong acoustic fingerprints. DAS technology can detect changes in the underlying acoustic signature of equipment and machinery. As such, it can be employed to monitor previously unmonitored assets at remote locations and produce an alert when equipment fails. An example would be the failure on an air conditioning unit cooling essential electronics; the alarm will allow the operator to prevent heat damage to critical or high-value equipment.
Reporting and forensic analysis
By recording all activity in the vicinity of a pipeline, before and after analysis of particular activities and events such as earthquakes can be undertaken to make sure the integrity of critical assets has not been compromised. This data also allows engineers to develop further in-depth analysis of activity if required.
Challenges to the safety and security of pipeline systems are diverse and ever changing. This situation calls for a well-designed, reliable and intelligent pipeline monitoring system. Advanced solutions such as DAS technology provide operators with detailed, real-time information about incidents or accidents on the line, thus significantly reducing response time in the event of a natural disaster, equipment failure, third-party interference or attack.