Presenter: David Dingley Organization: Atmos International Country: United Kingdom Abstract Pipeline theft is a serious global problem and has been on the rise for the last few years. Petroleum thefts from pipelines in countries such as China, Nigeria, Mexico and Egypt are almost commonplace. Unfortunately the theft events are now found everywhere across Europe. The extent, severity and risk of such theft operations are a major concern to the industry as well as the general public. The challenge facing pipeline operators is they are dealing with a more sophisticated class of criminal. These thieves are well organised and work in multi skilled teams. They utilise a number of different tactics to remain undetected such as burying hoses and using the surrounding environment to hide their activities such as hedgerows and forested areas. In addition, the theft rate is usually well below the flow meter accuracy level, making it difficult for traditional leak detection systems to detect, and locate the criminal activity. This paper will discuss the leak detection technologies that have been adapted to detect thefts and secure accurate tapping point locations. A couple of real life theft events will be used to illustrate how oil thefts are detected and located. Introduction Canada s Financial Post in 2014 listed the five countries most plagued by oil theft: Nigeria, Mexico, Iraq, Indonesia and Russia [1]. However over the last couple of years there has been a rise in pipeline thefts globally. Countries such as Denmark, Spain, Italy and United Kingdom have seen widespread problems associated with oil theft. The thieves are well organized, their resources include commercial grade welding equipment, measuring instruments, night vision goggles, and vans with modified suspension or exit holes in the floor. These thieves are well trained with the
engineering skills and knowledge to avoid detection. The thieves employ a host of different tactics when stealing oil from pipelines: 1. Pre-install the tapping point, hose and associated valves and equipment before a pipeline is commissioned. 2. Select remote site or well- hidden location. 3. Bury and cover the hose pipe and all other device underground. 4. Open theft valves very slowly to generate small pressure change over a long time period ( the patient thieves ). 5. Maintain the theft rate below flow meter repeatability level. e.g. 0.1% of pipeline throughput. 6. Carry out the activities at night. 7. Steal often but small volumes each time. 8. Inject water into the pipeline while taking oil out. 9. Perform thefts at multiple locations along the pipeline. All these different tactics make it difficult for pipeline companies to detect and locate thefts quickly and accurately. Leak detection technologies can and have been used to detect thefts with some adaptation and development. This paper will discuss the application of the negative pressure wave and statistical volume balance methods to theft detection. The next section will discuss each of the technologies, followed by a section on results from real theft events. Theft detection technologies Avoiding detection is a key target when thieves are going to commence an operation to extract product from a pipeline. This approach differs from pipeline leaks in a number of ways: Small amount of product is stolen (ranging from 10 to 3000 liters) The theft flow rate can be less than 0.1% Theft events last for less than one hour usually although occasionally a theft continues unchecked The changes in pressure are very small when the tapping point is opened/closed With these unique characteristics the main requirements of theft detection are: 1. Sensitivity: detecting the small product withdrawal 2. Accuracy: locating the tapping point as accurately as possible.
3. Response time: detecting the product withdrawals as quickly as possible. Different leak detection technologies can be adapted to meet the above requirements [2]. This paper will discuss the following three theft detection options: Negative pressure wave Statistical volume balance and Theft Net service. Negative pressure wave This technology relies on high speed analogue pressure sensor readings to identify whether a leak/theft has occurred on the pipeline. This type of system acquires and analyzes the pressure data at a frequency much higher than the typical 5 second SCADA rate, capturing data at 60 samples a second [2]. Specialized equipment is needed to acquire data at such high frequency as shown in Figure 1. Figure 1: Overview of the Rarefaction Wave System with the AWAS units [2]. As Han and Kim [2] pointed out, the main advantage of this system are: Accurate leak location within meters of the actual location Short detection time for all leak sizes High sensitivity provided through the 60hz sample rate These are the key features in effectively detecting theft events in all operational conditions.
Figure 2 shows an example of a theft event being detected by the negative pressure wave system. Figure 2: Example of a theft event generating 0.1bar (1.45 psi) pressure drop only. Statistical volume balance This type of leak detection technology relies on the pressure and flow measurements taken from a pipeline. It uses the existing instrumentation and connects via existing SCADA, PLC or RTU systems. This system monitors the difference between the inlet and outlet flow corrected by the inventory change. This is also referred to as the Corrected Flow Difference to determine whether the pipeline is in a leak condition. The statistical hypothesis testing method known as the Sequential Probability Ratio Test (SPRT) [2] uses the Corrected Flow Difference. The main advantages of this system are: Low false alarm rate Detects leaks under steady-state, transient and shut-in conditions Accurate leak size estimate. Since the theft rate is usually below the flow meter accuracy and repeatability level, it is difficult for this technology to work under running conditions unless false alarms are accepted. The system includes an additional theft module for detecting thefts during
shut-in conditions only in order to maintain reliability for both leak and theft detection. Figure 3 shows an example of it working. Figure 3 Statistical theft detection during shut-in period (red bar at the bottom indicates theft alarm) Theft Net service As theft rates become smaller, it becomes necessary to lower the minimum leak size to be detected. However in doing this it can result in increased false alarms as the identified flow and pressure are mostly below the instrument repeatability and process noise level. Theft Net service is an offline service that is offered to pipeline companies. This offline service allows improved leak location accuracy and sensitivity without unnecessary false alarms. Theft Net combines portable and fixed hardware and software solutions with offline data analysis by an experience engineer. Through this service an engineer s ability to interpret data helps theft to be located down to meters. Theft Net uses pressure data collected at 60 Hz sample rate and sent to a central location via a cloud based service.
The data is then filtered to present only the relevant information required and the location of the illicit tapping points are reported to the pipeline operators. It is well documented that online leak/theft detection systems have to find a balance between sensitivity and false alarms [2], [3]. Most leak detection systems can detect leaks as small as 0.5% of nominal flow without the issue of false alarms. However this becomes an issue as the majority of theft events are less than 0.3% of the nominal flow. The capability to analyse the data offline has allowed the location and detection of a theft to within 5 meters for thefts as small as 0.1% of the nominal flow in static and running conditions. Combining the Theft Net service with a single or multiple online leak detection systems allows for a more reliable leak detection system with the ability to effectively deal with all types of theft events. Examples of thefts detected The technologies discussed in this paper have been applied to theft detection on a number of pipelines all over the world, including the UK, China, Turkey, Israel, South America and continental Europe. The use of the Theft Net service and leak detection systems has led to the detection and location of many illicit tapping points, such as an oil withdrawal through a 12 mm hole that was attached to a 1.5km (0.9mile) long underground hose pipe in Europe. The theft detection systems have even detected the theft of samples between 10 and 20 liters of product from some pipelines during static conditions. These small samples are usually extracted to check what fluid is in the pipeline before a full product withdrawal is commenced. A couple of examples will be presented to illustrate the difficulties and successes that come with detecting and locating tapping points. Example 1 Theft leading to a leak In November 2015 the statistical leak detection system detected a theft in the UK shortly after midnight. Theft Net service located the theft to within 5m of the actual tapping point. Unfortunately this particular tapping point went wrong and started leaking fuel into the ground. The reason for the failure of the tapping point was the
use of a plastic clamp that could not hold the pipeline pressure. Figure 4 shows the failed tapping point. Figure 4: Failed tapping point left exposed by the thieves This event highlights the damages that are caused by illicit tapping points and it could have been far worse if the pipeline had ruptured. This makes the fast and correct response to such events crucial. Example 2 Theft hard to locate This example highlights the difficulty that often faces pipeline operators when they are trying to find an illicit tapping point. The theft detection system provided a location accuracy of 20m. Figure 5 shows the aerial view of the pipeline section where the tapping point is located. Figure 5: Arial view of the buried pipeline section
The tapping point was so well hidden by the thieves that nothing was visible externally. Atmos and the pipeline operator completed a line walk together and they could not see any sign of the tapping point. A surveillance team was set up to monitor the area during the night. In the morning they located the tapping point very close to the walk pathway. This tapping point has been buried in a farmland and the hose has been trenched to keep it well hidden. Figure 6 shows the exposed tapping point. Figure 6: The hidden tap exposed
Conclusion Theft detection is different from leak detection, as such it requires existing detection technologies to be adapted to detect thefts quickly and locate them accurately. As thieves are using technologies to remain undetected with theft rates below 0.3% of the nominal flow, the leak detection systems must be more sensitive than when they were originally designed. As this paper has shown the combination of multiple systems with offline analysis (Theft Net) has allowed the detection of small theft volumes. Theft location accuracy has also dramatically improved down to a few meters. Theft detection will always remain a constant battle between new tactics used by the thieves and the further advancement of theft detection technologies. It has been shown that a combination of multiple methods will provide the best overall solution in detecting theft events under all operational conditions. NOMENCLATURE AWAS Atmos Wave Acquisition System DCS Distributed Control System PLC Programmable Logic Controller RTU Remote Terminal Unit SCADA Supervisory Control and Data Acquisition SPRT Sequential Probability Ratio Test References 1. http://business.financialpost.com/news/energy/these-are-the-5-countriesmost-plagued-by-oil-theft? lsa=906f-a9b4 2. Peter Han and Mark Kim 2014: Synergy in Leak Detection: Combining Leak Detection Technologies that use different Physical Principles, 10 th International Pipeline Conference. Calgary, Alberta, Canada, 29 th September to 3 rd October 2014. Canada: IPC2014 3. Jun Zhang, Andy Hoffman, Adrian Kane, John Lewis 2014: Development of Pipeline Leak Detection Technologies, 10th International Pipeline Conference. Calgary, Alberta, Canada, 29th September to 3rd October 2014. Canada: IPC2014