Ultimate Guide to Oil and Gas Pipeline Leakage Monitoring, 2025

Fiber optic temperature sensor, Intelligent monitoring system, Distributed fiber optic manufacturer in China

Direct monitoring scheme for oil and gas pipelines and related technical applications

1、 Introduction to Direct Leak Detection Method for Oil and Gas Pipelines
The characteristic of oil and gas pipelines is that they have multiple points and long lines, and most of them are buried pipelines. They are used in harsh environments and are prone to leakage. The direct leak detection method uses a detector to directly detect leaks outside the pipeline to determine leaks, which is different from the indirect leak detection method that estimates leaks by monitoring pipeline operating parameters.

2、 Main direct monitoring schemes
（1） Leak detection cable method
The leak detection cable method is a coaxial cable made of non permeable but oil permeable materials laid along pipelines. Pulse is emitted from one end of the cable. When the pipeline leaks, the oil will penetrate the cable. Since the cable soaked in oil can reflect the pulse, detecting the reflected pulse signal can determine whether the pipeline is leaking and locate the leak location. This method can provide direct response detection for oil leakage situations, and the principle is relatively clear and intuitive. However, factors such as the material and process of the cable itself may affect the accuracy and reliability of the detection, and if the cable is damaged, it may lead to misjudgment or inability to detect.

（2） Sensing fiber optic cable method (application of distributed fiber optic sensors)

The working principle of distributed fiber optic sensors: Distributed fiber optic sensors are a type of sensing fiber optic sensor that has the ability to simultaneously obtain the measured distribution information that changes over time and space within the sensing fiber area. When light waves propagate in optical fibers, their characteristic parameters (such as amplitude, phase, wavelength, etc.) change under the influence of external factors (such as changes in the environment around the pipeline due to leakage). After laying a sensing optical cable along the oil pipeline, the leakage points of the pipeline can be discovered and located through signal analysis and processing of these parameter changes.

Types and functions of distributed fiber optic sensors

Raman DTS (Distributed Temperature Sensing): It can measure accurate temperature values without interference between temperature and strain, and can use single-mode (SM) or multi-mode (MM) optical fibers. MM fiber can provide stronger scattering signals and is more sensitive to temperature changes. When oil and gas pipelines leak, if the leakage causes changes in the surrounding temperature, Raman DTS can detect the leak based on this temperature change, which is one of the important technical means of distributed fiber optic sensing for pipeline leak detection.
Brillouin DTS: It can measure strain and temperature values in situations where there may be interference between temperature and strain, and its backscatter signal is stronger than that of Raman. Usually used in loop configurations that require halving the monitoring range and using single-mode fiber. This technology can comprehensively judge the status of pipelines from changes in strain and temperature when detecting pipeline leaks, and has good adaptability in some specific pipeline layouts and monitoring requirements.
Distributed Temperature Gradient Sensing (DTGS): It is a part of Quantitative DAS (Distributed Acoustic Sensing) or Distributed Fiber Bragg Grating (DFBG). It can quickly measure temperature gradients with very high resolution (0.001K) within a limited time span without the need to measure absolute temperature. In pipeline leak detection, if the leaked material (gas or liquid) escapes into the external environment of the pipeline and causes a change in temperature gradient, DTGS can effectively capture this change for leak detection. When used as part of DFBG, special treated FBG fibers are used, and when used as part of quantitative DAS, single-mode fibers are used.

Non quantitative DAS (amplitude based) and quantitative DAS (phase based): Non quantitative DAS is mainly used for perimeter protection and does not provide DTGS (distributed temperature gradient sensing) in leak detection related applications, making acoustic classification difficult; Quantitative DAS is suitable for applications that require DAS-DTGS and can provide high-quality acoustic signals (low fading, quantifiable, high repeatability) required for event classification. Quantitative DAS provides the true signal amplitude or phase of acoustic signals, in addition to multi LDS (leak detection system) detection methods, it also includes other functions such as PIG tracking and third-party interference monitoring. Both use single-mode fiber, and quantitative DAS is of great significance for accurately detecting and locating leakage points in many cases, which can improve the accuracy and effectiveness of detection.

（3） Infrared method

In oil and gas pipeline transportation, in order to reduce the viscosity of crude oil, it is usually heated before pipeline transportation. Once a pipeline leaks, the surrounding surface will be covered and soaked by the leaked crude oil, causing the temperature to rise and resulting in changes in surface infrared radiation. At this point, using an infrared detection device can detect smaller leakage points. This method fully utilizes the pre heating condition of oil and gas pipelines during the transportation of crude oil, and is sensitive to surface temperature changes caused by leaks. However, if there are other interfering heat sources in the surrounding area or in complex environments with low external temperatures such as winter, it may affect the detection effect and result in misjudgment or missed judgment.

（4） Ground penetrating radar method
The ground penetrating radar method uses one antenna to emit carrier free electromagnetic pulses into the underground medium, while the other antenna receives echoes reflected from different interfaces of the underground medium. Because the propagation of electromagnetic waves in a medium is related to the electrical properties and geometric shape of the medium, when an oil pipeline leaks, the electrical properties of the surrounding surface change, and the time-domain waveform of the reflected signal also changes accordingly. By analyzing the time-domain waveform characteristics of the reflected signal, it is possible to determine whether there is a leak in the pipeline. This method has unique advantages in detecting changes in the electrical characteristics of the surrounding medium of underground pipelines to determine pipeline leaks. However, for pipelines buried deep, with complex geological structures or many interference sources in the surrounding area, waveform analysis becomes complex and difficult, leading to a decrease in detection accuracy.

（5） Application of Distributed Fiber Optic Temperature Monitoring in Oil and Gas Pipeline Leakage Monitoring

The principle of distributed fiber optic temperature monitoring uses the fiber itself as a sensor to monitor temperature changes along the line. For example, the distributed fiber temperature sensing technology based on Raman scattering generates Raman scattering light when the laser transmitted in the fiber interacts with the fiber molecules. The intensity of Raman scattering light is related to temperature, and measuring the intensity of Raman light can obtain temperature distribution information along the fiber. When a leak occurs in an oil and gas pipeline, if the substance inside the pipeline has a certain temperature (such as heated crude oil), the leakage into the surrounding environment will cause a change in environmental temperature, which can be sensed by optical fibers to determine the possible location of the leak.

advantage

High accuracy: It can accurately measure small temperature changes along the fiber optic cable, detect subtle temperature changes in the early stages of leakage, and help detect smaller leakage points in a timely manner.
Distributed measurement: It can achieve continuous and distributed temperature monitoring along the pipeline. Compared to traditional point temperature sensors such as thermocouples and thermal resistors, distributed fiber optic temperature monitoring can obtain a wide range of temperature information without the need for a large number of sensors to be arranged at intervals, greatly improving the coverage of monitoring.
Strong anti-interference ability: Fiber optic transmission signals are not easily affected by electromagnetic interference, and can operate stably in some complex electromagnetic environment oil and gas pipeline laying scenarios (such as near power equipment or high-voltage lines), ensuring the reliability of temperature detection.
Intrinsic safety: Optical fibers themselves do not generate electrical sparks and are suitable for use in flammable and explosive environments such as oil and gas, with high safety..
Application examples include deploying distributed fiber optic temperature monitoring systems near oil storage and transportation pipelines in some large oil depots or refineries, which can monitor the temperature situation around the pipelines in real time. If a pipeline leaks, the surrounding temperature will quickly change. Whether it is oil leaking into a low-temperature environment to heat the surrounding soil, or high-temperature oil leaking causing local temperature abnormalities, the system can respond quickly, prompt leak information in a timely manner, buy time for repair, and prevent serious accidents such as explosions and fires caused by leaks.

（6） Advantages of Fiber Optic Perimeter Security Vibration Monitoring in Oil and Gas Pipeline Leakage Monitoring

The basic principle of fiber optic perimeter security vibration monitoring is based on the sensing characteristics of fiber optic. When external vibrations act on the fiber optic, the phase, polarization state and other characteristic parameters of the light transmitted in the fiber optic will change. By detecting changes in this light signal, we can perceive potential vibration events around the pipeline, such as third-party construction excavations, human theft and damage, or the impact of natural disasters such as earthquakes on the pipeline. These vibration events that may cause pipeline rupture or damage, leading to leakage, can be captured and alerted in a timely manner.
advantage
High sensitivity: Fiber optic perimeter security vibration monitoring uses fiber optic sensors as sensors, which have high sensitivity and can quickly sense small vibration changes in the surrounding environment. It can effectively detect abnormal vibrations related to pipeline leaks, such as weak vibrations generated by people excavating soil near the pipeline (which may cause early leakage behavior), and can provide early warning of leakage events.

Strong anti-interference ability: Fiber optic sensors have excellent anti-interference ability and can still work stably in complex electromagnetic environments (such as around oil and gas pipelines near power facilities). In addition, the optical fiber sensor is not vulnerable to weather, temperature and other climatic factors. For example, in severe weather such as rainstorm and lightning strike, it can still accurately monitor vibration, effectively avoid interference from external factors, accurately judge pipeline conditions, and reduce the false alarm rate of 14.

Long transmission distance: Fiber optics have low signal attenuation characteristics and can achieve long-distance signal transmission. For long-distance oil and gas pipelines, a single optical fiber can cover a long pipeline route for perimeter security and vibration monitoring of the entire line. This makes the monitoring range more extensive, reduces the number and cost of monitoring equipment deployment, and is suitable for the monitoring needs of facilities such as oil and gas pipelines that sometimes stretch for long distances.

Strong real-time capability: By utilizing advanced fiber optic sensing technology, real-time monitoring and alarm can be achieved. Once there is a vibration situation around the pipeline that may cause leakage, the system can sense and issue an alarm signal in the first time, detect abnormal situations in a timely manner, and notify relevant personnel to take corresponding measures to prevent further damage and leakage accidents.

High reliability: Fiber optic sensors have high stability and can work reliably for a long time, which helps reduce maintenance costs and time. During the long-term operation of oil and gas pipelines, there is no need to frequently replace sensors or perform large-scale maintenance, which reduces the workload and cost of operation and maintenance, while ensuring uninterrupted monitoring, ensuring the safe operation of pipelines, and avoiding huge economic and environmental losses caused by leaks.

Good concealment: Fiber optic cables can be easily buried or concealed without affecting the aesthetics and safety of the surrounding environment. For the monitoring of oil and gas pipelines, it is not easy for illegal elements to detect and maliciously damage them, ensuring the integrity and effectiveness of the monitoring effect, and the concealed laying will not affect the normal production, life or other work activities around the pipeline. At the same time, it also has the advantage of accurate positioning, which can accurately point out the location of abnormal vibrations, making it convenient to quickly locate and dispose of potential sources of leakage hazards.

（7） The Effect of Distributed Fiber Optic Sensing in Oil and Gas Pipeline Leakage Monitoring
The effectiveness of distributed fiber optic sensing in oil and gas pipeline leakage monitoring mainly benefits from its various working principles and technical means. For example, taking distributed optical fiber acoustic sensing (DAS) technology as an example, it is based on a phase sensitive optical time domain reflectometer (Φ – OTDR) to detect the backward Rayleigh scattering signal generated by coherent pulsed light propagating in the fiber, and based on this, detect and reconstruct leakage events. It mainly consists of optical fibers, optical signal amplifiers/decoders, high coherence pulse laser sources, and data processing analyzers. This technical means can detect and analyze acoustic signals in the surrounding environment of pipelines with high sensitivity, so that even small acoustic changes caused by leaks (such as flow sound generated by fluid leaks, sound generated by the interaction between leaks and surrounding media, etc.) can be captured, thereby determining whether leaks have occurred and achieving accurate positioning.

Distributed fiber optic sensing can achieve comprehensive monitoring of pipelines, detecting temperature changes caused by leaks. As mentioned earlier, distributed fiber optic temperature sensing technology plays a role in temperature monitoring. It can also detect vibrations caused by leaks (including mechanical energy release generated at the moment of leakage, as well as continuous vibrations caused by the impact of leaked substances on the surrounding environment). In addition, when the pipeline is disturbed by external forces (such as changes in mechanical construction stress, human damage, and other early behaviors that may lead to pipeline leaks), it can also be reflected in the changes of various characteristic parameters of optical signals in the optical fiber (such as strain, phase, intensity, etc.). Equivalent to monitoring the status of pipelines from multiple dimensions, greatly improving the comprehensiveness of pipeline leak monitoring.

Distributed fiber optic sensing has high accuracy in locating leakage points. For example, some distributed fiber optic vibration detection systems based on coherent detection technology can achieve accurate positioning through techniques such as PDC – φ – OTDR optical time-domain reflection demodulation algorithm. The positioning accuracy can reach the meter level, such as ± 10m. This precise positioning capability helps to quickly determine the location of leaks, carry out repair work in a timely manner, and reduce a series of hazards such as oil and gas losses, environmental pollution, and safety risks caused by leaks.

The advantages of long-distance and distributed coverage are suitable for monitoring long-distance oil and gas pipelines. It utilizes the feature that optical fibers can be laid along the pipeline for a long distance to achieve large-scale distributed coverage monitoring of pipeline routes. A single fiber optic cable can monitor the status of pipelines that are several kilometers or even tens of kilometers long, reducing the problem of data connection and mismatch between different devices in the monitoring system, ensuring that coherent and complete pipeline health status information can be obtained, and ensuring the healthy operation of the entire oil and gas pipeline.

3、 Comparative analysis of the best solution

（1） Comparison of detection principles
Leak detection cable method: mainly relying on the permeability of the cable to oil and the principle of pulse reflection, the detection is more direct, but it is greatly affected by the performance and service life of the cable.
Sensing fiber optic cable method: Based on the characteristic parameter changes of light waves in distributed fiber optic sensors, leaks can be detected, and the pipeline status can be monitored from multiple aspects (such as temperature, strain, etc.), with rich monitoring dimensions. Moreover, different types of distributed fiber optic sensing technologies (such as Raman DTS, Brillouin DTS, etc. mentioned above) can be flexibly used to adjust strategies according to specific pipeline scenarios and monitoring needs, which may have better adaptability in the event of complex pipeline leaks and changes in the surrounding environment.
Infrared method: detects the impact of surface temperature changes caused by crude oil spills on infrared radiation, provided that the oil and gas transported through pipelines have a certain temperature and are easily affected by external environmental temperature interference.
Ground penetrating radar method: It is based on the impact of pipeline leaks on the electrical properties of underground media, thereby changing the electromagnetic pulse reflection waveform for detection. It has poor adaptability to environments with complex underground media structures or multiple interference sources.
Distributed fiber optic temperature monitoring: Focusing on temperature changes, the principle is clear and direct, but relatively simple, and there may be a certain risk of misjudgment in some very slow and insignificant temperature changes in leakage situations or normal pipeline operation temperature fluctuations. However, for some hot crude oil transportation pipelines or high-temperature long-distance pipelines, temperature monitoring is an important signal for leak indication, which can effectively detect leaks caused by abnormal temperature.
Fiber optic perimeter security vibration monitoring: By detecting the environmental vibration around the pipeline to determine whether there is a potential threat of leakage, it can issue warnings in the early stages of abnormal actions (such as excavation actions before damaging the pipeline, suspicious movements of personnel near the pipeline, etc.) before the leakage event occurs. However, the detection capability for small slow leaks that have already occurred (if no obvious vibration is caused) may be insufficient.
Distributed fiber optic sensing: integrates multiple monitoring capabilities (temperature, vibration, strain, etc.), with more diverse and comprehensive principles. It can detect and judge pipeline leaks from different characteristic perspectives, so its applicability may be wider, but the system composition is relatively more complex and the technical requirements are higher.

（2） Sensitivity comparison
Leak detection cable method: The sensitivity is average, and there may be a risk of missed detection in situations where the cable is not fully immersed in oil or the pulse signal is weak.
Sensing fiber optic cable method: Due to the diverse types of distributed fiber optic sensing technology and the ability to accurately set sensitivity thresholds for optical signal detection, it generally has high sensitivity and can detect weak changes in light wave parameters along the fiber optic cable to detect pipeline leaks. Especially, temperature sensors such as Raman DTS and some distributed fiber optic sensors based on sound waves can detect very small temperature and acoustic changes.
Infrared method: Under ideal conditions without other interfering heat sources, it has high sensitivity to temperature. But in actual complex environments, it may cause significant noise in the received signal, thereby reducing sensitivity.
Ground penetrating radar method: The sensitivity to changes in reflected signals caused by changes in the characteristics of underground media is relatively low. It requires significant changes in electrical characteristics caused by leaks to accurately detect leaks, which may reduce the sensitivity of detection in complex geological conditions.
Distributed fiber optic temperature monitoring: If the system is set up properly and the fiber quality is good, it can have high sensitivity to temperature and quickly detect small temperature fluctuations caused by leaks. The detection effect is good without being disturbed by external factors.
Fiber optic perimeter security vibration monitoring: High sensitivity is one of the advantages, which can detect very microscopic vibration changes and timely warn of possible leaks caused by pipeline surrounding vibrations. However, it is powerless for leakage causes that do not generate vibrations (such as natural corrosion perforation of pipelines gradually developing into leaks).
Distributed fiber optic sensing: It combines the sensitivity advantages corresponding to multiple detection principles. For example, high sensitivity in acoustics can be reflected through DAS (Distributed Acoustic Sensing), while in temperature, it is similar to the principle of distributed fiber optic temperature monitoring with high sensitivity, which can detect leakage from multiple aspects earlier.

（3） Comparison of positioning accuracy
Leak detection cable method: It can achieve certain positioning, but the positioning accuracy is relatively low due to the physical properties and laying method of the cable itself.
Sensing fiber optic cable method: Especially based on advanced distributed fiber optic sensing technology, such as quantitative DAS, precise signal analysis can be achieved with specific algorithms to achieve high-precision positioning, some of which can reach meter level positioning accuracy. Distributed fiber optic acoustic sensing technology can accurately locate leakage points.
Infrared method: mainly determines a range, with poor positioning accuracy, and can only roughly determine that a leak has occurred in a certain area on the surface, making it difficult to accurately locate the specific location of the pipeline leak point.
Ground penetrating radar method: The positioning of leakage points relies on complex analysis of electromagnetic pulse reflection waveforms, and the positioning accuracy is generally not as accurate as some high-precision distributed fiber optic sensing technologies.
Distributed fiber optic temperature monitoring: If a system with high-resolution temperature measurement and positioning algorithms is used, such as distributed temperature gradient sensing (DTGS), it can accurately locate temperature change points to determine the possible leakage area. However, there may be some gap in positioning accuracy compared to other distributed fiber optic sensing technologies.
Fiber optic perimeter security vibration monitoring: It can accurately locate the location of the vibration source, with a maximum accuracy of about plus or minus 2 meters, and can timely capture the local vibration location that causes pipeline leakage hazards.
Distributed fiber optic sensing: It has significant advantages in positioning and can integrate multiple positioning techniques, such as combining vibration monitoring and temperature change positioning, to achieve more accurate and reliable leak point positioning. It dynamically adjusts positioning strategies in different scenarios and leak types.

（4） Cost comparison
Leak detection cable method: The cost includes the manufacturing cost and laying cost of the cable. Relatively speaking, the cost of the cable is not low, and if the cable length is long, the cost is high. Moreover, maintaining the cable in the future requires a certain amount of manpower and material resources.
Sensing fiber optic cable method: Although the cost of the sensing fiber optic cable itself and the initial cost of supporting distributed fiber optic sensing equipment, signal processing equipment, etc. in the later stage are relatively high. But once built and put into operation, the overall system has a long service life and high stability, which may have good cost-effectiveness in the long run. And with the development of technology, the price of distributed fiber optic sensing equipment is gradually decreasing.
Infrared method: The cost of infrared detection devices is not very high, but for large-scale long-distance oil and gas pipeline monitoring, it is necessary to arrange a large number of infrared equipment reasonably to ensure effective coverage, which may increase the overall cost of equipment layout.
Ground penetrating radar method: Ground penetrating radar equipment is relatively expensive, and the technical operation requirements during use are high, which may increase labor costs. In addition, more equipment debugging and optimization are required in some complex geological conditions, further increasing costs.
Distributed fiber optic temperature monitoring: In the initial stage, a complete fiber optic system needs to be laid for temperature detection, and a signal processing unit for temperature sensing is required, which is costly. However, the same system can be used for large-scale and long-distance monitoring to reduce cost sharing, and the stable and durable fiber optic reduces the cost of frequent replacement.
Fiber optic perimeter security vibration monitoring: The equipment cost includes fiber optic and vibration monitoring related host equipment, signal acquisition and processing devices, etc., and the cost is relatively high. However, due to the ability to perform perimeter security monitoring on long-distance pipelines, it has a good cost-effectiveness when the added value of safety is high and the pipeline is long.
Distributed fiber optic sensing: Due to its strong technical comprehensiveness and complex system composition, the procurement, installation, debugging, and fiber optic laying costs of hardware equipment (various sensors, modems, etc.), software (software systems corresponding to various signal processing and analysis algorithms) in the early stage are relatively high. However, it has a wide coverage and diverse functions, can replace multiple single monitoring methods, and has high reliability and long service life, which can reflect cost-effectiveness in long-term operation and maintenance processes.

（5） Comparison of applicable scenarios
Leak detection cable method: It is suitable for some above ground or shallow buried pipeline scenarios where oil is the main transport medium and the cable working environment is relatively friendly without damaging the cable structure. However, it is not suitable for multiphase flow (mixed transportation of oil, gas, water, etc.) pipelines, corrosive environments, etc.
Sensing optical cable method: It can be widely applied to oil and gas pipelines of different types (oil, gas, etc.), different transportation states, and different geographical environments, as long as the optical fiber can be laid and operated normally. In some scenarios that require high integrity and accuracy of monitoring data, early warning, and long-distance, large-scale pipeline monitoring, it can play a good role. For example, the long-distance oil and gas pipelines from offshore oil and gas platforms to land have better effects in complex environments and pose greater risks in case of leaks.
Infrared method: It is more suitable for application in crude oil transportation, and in the surface environment around pipelines with relatively stable ambient temperature, no excessive heat source interference, and relatively simple open terrain. It may be more suitable for leak detection of heated crude oil pipelines in cold high latitude regions or deserts with less interference from heat sources.
Ground penetrating radar method: suitable for oil and gas pipelines in areas with relatively simple soil structures and relatively single underground medium components. Short term detection can also be carried out in new pipeline laying areas to preliminarily determine whether there is leakage in the pipeline.
Distributed fiber optic temperature monitoring: It has good applicability in oil and gas pipeline scenarios that are sensitive to temperature changes, such as the transportation process of hot oil pipelines, or the use of temperature differences to determine pipeline operation status (such as monitoring the relationship between soil temperature around the pipeline and medium temperature inside the pipeline).
Fiber optic perimeter security vibration monitoring: Oil and gas pipelines with frequent human activities along the pipeline (such as pipelines near residential areas or industrial construction areas), or natural disasters such as earthquakes, can prevent leakage caused by external damage in a timely manner and play a good protective monitoring role in pipeline safety.
Distributed fiber optic sensing: Due to its multiple functions, it can be applied to different types of oil and gas pipelines (whether above or below ground, long-distance or short distance, single medium or multi medium transportation, etc.). And it has strong adaptability in multiple scenarios with high safety requirements and the need for comprehensive monitoring of pipeline status (temperature, vibration, strain, and other physical quantities) to prevent leakage risks.
Overall, each scheme has its advantages and disadvantages. In actual oil and gas pipeline leak monitoring, one or more schemes are often selected based on specific pipeline conditions (such as pipeline type, laying environment, safety requirements level, etc.), budget, and economic feasibility to achieve the best leak monitoring effect. For example, distributed fiber optic sensing can be combined with fiber optic perimeter security vibration monitoring to achieve accurate leak detection and positioning while effectively preventing external forces from damaging pipelines and causing leaks, thereby improving the overall safety and operational efficiency of oil and gas pipelines.