Real-time monitoring of pipeline integrity is a key factor for the environmental sustainability and for the reduction of production downtime in oil & gas industry.
FIELD DEPLOYMENT OF ENI VIBROACOUSTIC PIPELINE MONITORING SYSTEM (e-vpms™): LONG TERM PERFORMANCE ANALYSIS G. Giunta, P. Timossi, G.P. Borghi, eni S.p.A.,R. Schiavon, tecnomare S.p.A G. Bernasconi, Politecnico di Milano, F. Chiappa, SolAres (Solgeo & Aresys JV) This paper was presented at the 13th Offshore Mediterranean Conference and Exhibition in Ravenna, Italy, March 20-22, 2015. It was selected for presentation by OMC 2015 Programme Committee following review of information contained in the abstract submitted by the author(s). The Paper as presented at OMC 2015 has not been reviewed by the Programme Committee.
ABSTRACT Real-time monitoring of pipeline integrity is a key factor for the environmental sustainability and for the reduction of production downtime in oil & gas industry. In 2009 eni promoted an R&D project for developing a novel real-time technology, based upon vibroacoustic pipeline sensing. In fact, any interaction with a pipe filled with gas or liquid generates pressure waves that are guided within the fluid for long distances, carrying information on the source event. Among these events, leaks (due to corrosion, third party interference, theft, incidents, etc.) are the ones where real-time monitoring has a paramount value. Starting from 2010, experimental campaigns in controlled scenarios were carried out and validation of the mathematical models of pressure wave’s propagation in fluid filled pipes was performed. The field experience has been used to upgrade the prototypal version of the system to an industrial version (e-vpms™). Today the system is operative, or in an advanced installation phase, on several pipelines in Italy and in Nigeria, and it has detected tens of bunkering activities with a localization accuracy of about 25 m, from a distance up to 30-35 km from the sensing point. Moreover, the utilization of original environmental noise removal procedures has brought to an increased system sensitivity and performance, in terms of a reduction of detectable leak holes and of a decrease of false alarms rate. The paper describes the performance, reliability and flexibility of the system, analyzing the operation of several successful field deployments over a long time period.
DESCRIPTION OF THE PIPELINE MONITORING SYSTEM In 2009 eni started a research project (DIONISIO) in order to study and to design a proprietary vibroacoustic system for remote real-time monitoring of pipelines (e-vpms™), exploiting negative pressure waves and statistical analysis principles. In practice a discrete network of pressure and vibration sensors are installed on the pipeline, at relative distances of tens of kilometers (Fig. 1). The acoustic and elastic waves produced by third party interference (TPI) and by flow variations (leaks, spills, valve regulations, pig operations, etc.) propagate along the pipeline, and they are recorded at the monitoring stations. Multichannel processing of the collected signals enables the detection, localization and classification of the triggering event. The system has been extensively tested in single phase and multiphase transportation lines during several field campaigns, in order to obtain: experimental sound propagation parameters within the fluid, in different conditions; environmental noise produced by flow generation/regulation equipment; pressure noise level produced by TPI and leak events; vibroacoustic transients generated by travelling pigs, in low pressure and high pressure scenarios. 1
The experimental data has then been used to: derive and validate mathematical models of sound propagation within pipes; define and tune technical specification of vibroacoustic recording equipment; design advanced vibroacoustic data procedures for leak/TPI detection and localization; design vibroacoustic data procedures for remote tracking of travelling pigs. Detailed description of the system and of the field campaigns can be found in Giunta et al. (2011a, 2011b, 2013, 2014), Bernasconi et al. (2012, 2013a, 2013b) and Schiavon et al. (2014). The system has been industrialized for leak/spill/impact detection: fully operational installations are working on the lines Chivasso-Aosta (Italy, stabilized crude oil), Gaeta-Pomezia (Italy, refined products), Costa Molina 2 (Italy, injection water), Kwale-Akri (Nigeria, crude oil/water mixture). Key point of the monitoring system is the real time transmission to the central unit of synchronized vibroacoustic data from the remote stations located along the conduit, thus allowing full multichannel processing capabilities, with advanced noise removal procedures and adaptive estimation of pressure propagation parameters. In fact, pressure noise produced by pump/flow variations is used to estimate and update continuously an equivalent acoustic transmission channel between adjacent monitoring stations. Moreover, exploiting direction of arrival techniques, the same pump/flow noise is removed from the recorded data, in order to increase the sensitivity versus anomalous events. Finally, the information collected by the system during standard operation for leak/impact detection (pressure, sound velocity and absorption, etc.), can be analyzed, in real time as well as on a long term basis, in order to detect the development of anomalies in the fluid transportation system, such as: pipe deformations (buckles); pipe occlusions; variations of fluid properties; pump anomalies; valve anomalies. Examples of this “long term monitoring” results are presented in Bernasconi et al. (2013b, 2014).
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Fig. 1: e-vpms™ multipoint vibroacoustic sensing system
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CALIBRATION FIELD CAMPAIGNS TRANSMED natural gas offshore pipeline DIONISIO research project started in July 2009 with the installation of a prototypal vibroacoustic monitoring system on two lines (20” diameter and 155 km length) of the TRANSMED pipeline, at Mazara del Vallo terminal. During the data acquisition pipe maintenance and pig operations have been carried out on both lines, in different operational conditions. We show here an example of pig tracking, by processing the sound it produces while crossing the pipe internal welding dents. Fig. 2 is the pressure signal when a magnetic pig is approaching Mazara del Vallo station (October 8th 2009). The pipeline is in standard operation, at around 90-100 bar. The sound produced by the travelling pig increases almost exponentially as it approaches the receiving station: we have validated this propagation model with the rigid pipe - wide tube approximation (Blackstock, 2000). In the zoomed windows it is possible to distinguish the wavelets generated by the pig crossing the welding dents, around 12 m apart one from the other. We count 12-14 events per minute, corresponding to a pig velocity of 9-10 km/h. The velocity is very stable, at least when this events become visible, some hours before the pig arrival. In order to quantify the maximum detection distance, we performed a Short Time Average to Long Time Average (STA-LTA) data processing. Fig. 3 shows the result: every peak corresponds to the pig moving across a weld. By using a threshold criterion, we label the reliability of the events with a colour scheme: green indicates correct detection, yellow is uncertain, red is missed. Fig. 3 indicates that the pig becomes “visible” more than 30 km from the arrival.
Fig. 2: Pressure signal during pig operation. Windows with increasing zoom factor. Horizontal axis is time of October 8th 2009 (UTC).
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Fig. 3: Pig detection with STA-LTA data processing on pressure signal (horizontal axis 200s). Messina channel offshore pipelines e-vpms™ stations have been installed on two offshore natural gas transportation pipelines (Line 1: 20” diameter and 15.9 km length; Line 4: 26” diameter and 31.3 km length) crossing the Messina channel (Italy) and managed by SNAM RETE GAS (Fig. 4). The objectives of the test campaign were the following: measure and analyze the environmental noise in service conditions; acquire vibroacoustic data during controlled spill/leak test; design and test data processing routines for remote pig tracking; verify pipeline characterization with an equivalent acoustic transmission channel. We show here an example of pipe characterization as an equivalent acoustic transmission line.
Fig. 4: Line 1 (15.9 km length) and Line 4 (31.3 km length) offshore natural gas transportation. e-vpms™ system showing the map of Messina channel. Pressure noise is continuously generated by gas compressors, flow regulation equipment, local turbulence (“environmental” noise). In standard operation, absolute pressure is around 60-70 bar at the pumping station (Messina) and 50-60 bar at the receiving stations (Favazzina and Palmi). 4
Low pass (0.5-10 Hz) dynamic pressure noise is around 800-1800 Pa (8-18 mbar). Pressure noise has comparable amplitude on all stations meaning that local turbulence and flow regulations are the main sources of environmental noise. This noise is also comparable to measurements collected on the TRANSMED pipeline. We compute the correlation between the dynamic pressure signals recorded at both terminals of Line 1 (Messina - Favazzina). Pressure signal are low pass filtered below 10 Hz. Fig. 5 shows the result: there is a correlation peak at around -40 s, consistent with sound propagation from Messina to Favazzina at 386 m/s. Long term analysis of the propagation parameters (sound speed, attenuation coefficient) permits the detection of variations in the transmission channel, such as partial occlusions and/or pipe deformations.
Fig. 5: Normalized cross-correlation between pressure variations at Messina and Favazzina, from 12:00 Feb 5th 2013 (bottom). Average cross-correlation (top). Chivasso Aosta crude oil pipeline In December 2010 the prototypal vibroacoustic monitoring system was installed on the oil transportation pipeline in service in the North of Italy, managed by eni S.p.A., connecting Chivasso to Pollein (Aosta), ~100 km long (Fig. 6). Pipe diameter is 16”, oil pressure varies between 70 bars at the pumping station (Chivasso) down to 4 bars at the receiving terminal (Pollein). Flow rate is about 400 m3/h. Two vibroacoustic monitoring stations are located at the pipe ends (Chivasso and Pollein), three along the pipeline (VM21, VM28 and VM35), at an intermediate distance of around 30 km, two temporary stations have been mounted at V19 and V20, few kilometers from Chivasso station (Fig. 6, zoom). Recorded signals are vibrations of the pipe shell, and pressure variations within the fluid. In order to study vibroacoustic wave propagation along the pipeline, a complete set of threat actions have been designed and executed in controlled conditions (Tab .1).
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Fig. 6: Satellite map showing oil pipeline route (red line) and measurement stations (blue circles) on the Chivasso-Pollein (Aosta) pipeline section.
Tab. 1: TPI and spill tests of the filed campaign Action Man/truck/excavator movement near the infrastructure Man/excavator digging near the infrastructure Impacts on pipe shell Drilling/grinder pipe shell Spill from 0.1” to 0.5” valve
Data analysis and validation with mathematical models lead to summary Tab. 2, with the signal characterization for each threat action and the estimated detection distance. An innovative noise removal procedure has been successfully tested, in order to reduce the influence of pump pressure transients and to increase the system detection sensitivity. In November 2012 a spill test campaign has been performed to tune detection parameters (thresholds, time window analysis). From that time the installation is fully operative and it can detect within 2-3 minutes spill/leak events from holes > 0.2”. The calibrated system shows excellent performances in terms of false alarms (reduced to 0% in the monitored period at the expense of possible missing detection for spills minor of 0.2” diameters) and localization accuracy (around 25 m). Noise removal procedure is effective in reducing pump and flow regulation transients and to improve system sensitivity.
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Tab. 2: Field campaign: signal analysis and detection results. Observed detection distance
Estimated detection distance
Measured pressure at source
2 km
2-4 km
30mbar
50-1000Hz
+/-
2 km
5-10 km
200mbar
50-1000Hz
+/-
Drilling / grinder
No
No
No
Moving excavator (24 tons, 160HP)
2 km
2 km
5 mbar
50-1000Hz
+/-
Moving person
No
No
No
Manual digging
No
No
No
Excavator digging
2 km
4 km
5 mbar
50-500Hz
+/-
Spilling transient (0.3 l/s)
20 km
50-80 km
20 mbar
0-20Hz
++
Test type Low energy impacts (< 100J) Medium energy impact (< 300J)
Signal Environmental bandwidth noise removal at source
PILOT INSTALLATIONS Gaeta-Pomezia refined products pipeline Seven e-vpms™ monitoring stations have been deployed along the Gaeta-Pomezia refined products pipeline in July 2013. Pipe diameter is 16” and total length is 112 km (Fig. 7). In one year of operative campaign more than 15 illegal bunkering activities have been detected by e-vpms™ system in less than 4 minutes and localized within 25 m, thus avoiding dangerous environmental contaminations. Fig. 8 shows a spillage-theft localization occurred in September 2013. The detected events have a spill hole of 0.25”. As a side product, long term analysis of acoustic propagation parameters in the line provides both pumping status and transported fluid (Fig. 9).
Fig. 7: Gaeta-Pomezia pipeline track and e-vpms™ recording points.
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Localization of theft-spills with accuracy of 25 m
Fig. 8: Example of detection and localization of a fuel theft on Gaeta-Pomezia pipeline.
Fig. 9: Three month data analysis of Gaeta-Pomezia pipeline status derived from acoustic parameters. Kwale Akri oil-water pipeline The e-vpms™ system has been installed on the Kwale-Akri crude oil/water pipeline in the Delta Niger region, managed by Nigerian Agip Oil Company (NAOC), the local eni S.p.A. subsidiary, in order to detect and monitor spill events. Pipe diameter is 10” and total length is 17.3 km. Full customization, calibration and hand-over to NAOC operation dept have been concluded in May 2014.
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The e-vpms™ acquisition units are located at the two terminals of the line, Akri and Kwale (Fig. 10). The central unit is in the control room of Kwale station: it receives in real time the signals of the monitoring stations, supervising the whole system, running the leak detection codes and triggering the alarm procedures. In the first 6 months of operation, two events (including a 2” valve sabotage) has been detected and localized with no positive or negative false alarm. Again, long term analysis of acoustic propagation parameters provides also the pipeline status (Fig. 11). More details on this installation are in Schiavon et al. (2014).
Kwale
Akri
Fig. 10: e-vpms™ user map interface of Kwale-Akri pipeline.
Fig. 11: Sound pressure parameters of crude oil/water mixture by long term monitoring of Kwale-Akri pipeline.
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CONCLUSIONS eni has promoted and supported the design of a proprietary vibroacoustic technology for remote real-time monitoring of pipelines (e-vpms™), based upon the negative pressure waves and statistical analysis principles. Several experimental campaigns has been performed in order to tune and validate physical models of vibroacoustic data generation and propagation, to design advanced procedures of real time pipeline monitoring, to derive technical specifications for the recording equipment and sensors. The system has then been upgraded to an industrialized version and tested on different transportation pipelines in service condition. Key point of the monitoring system is the real time transmission to the central unit of synchronized vibroacoustic data from the remote stations located along the conduit, thus allowing full multichannel processing capabilities, with advanced noise removal procedures and adaptive estimation of pressure propagation parameters. Today the e-vpms® technology is operative on several pipelines in Italy and in Nigeria, and it has detected tens of illegal bunkering activities with a localization accuracy of about 25 m, from a distance up to 35 km from the sensing point. Moreover, long term analysis of the acoustic data recorded during standard operation is able to point out the development of anomalies in the fluid transportation system, such as pipe occlusions, pump failure, and fluid properties variations. The research team is working towards an integration of the e-vpms™ vibroacoustic technology with mass imbalance methods, exploiting the real time adaptive estimation of pressure propagation parameters. ACKNOWLEDGEMENTS The research project was funded and carried out by eni S.p.A. The authors are grateful to TMPC, SNAM RETE GAS and NAOC for technical assistance on pipeline test sites. REFERENCES Blackstock, D. T., Fundamentals of physical acoustics. John Wiley & Sons, Inc, 2000. Bernasconi, G., Del Giudice, S., Giunta, G., Pipeline Acoustic Monitoring, Pipeline Technology Conference, Hannover, 2012. Bernasconi, G., Del Giudice, S., Giunta, G., Dionigi, F., Schiavon, R., Zanon, F., Advanced pipeline monitoring using Multipoint Acoustic Data, 11th OMC Conference and Exhibition, Ravenna, 2013a. Bernasconi, G., Del Giudice, S., Giunta, G., Dionigi, F., Advanced pipeline vibroacoustic monitoring, Proceedings of the ASME 2013 Pressure Vessels & Piping Division Conference, Paris, PVP2013-97281, 2013b. Bernasconi, G., Del Giudice, S., Giunta, G., Advanced real time and long term monitoring of transportation pipelines, Proceedings of the ASME 2014 International Mechanical Engineering Congress & Exposition, Montreal, IMECE2014-36872, 2014. Dalmazzone, G. M., De Lorenzo, G., Giunta G., System and method for the continuous detection of impacts on pipelines for the transportation of fluids, particularly suitable for under water pipelines, Patent PCT/IB2010/002330, 2010. Giunta, G., Dionigi, F., Bernasconi, G., Del Giudice, S., Rovetta, D., 2011a, Vibroacoustic monitoring of pigging operations in subsea gas transportation pipelines, ASNT Fall Conference, Palm Springs, 2011a. Giunta, G., Dionigi, F., Bassan, A., Veneziani, M., Bernasconi, G., Del Giudice, S., Rovetta, D., Schiavon, R., Zanon, F., Third party interference and leak detection on buried pipelines for reliable transportation of fluids, 10th Offshore Mediterranean Conference, Ravenna, 2011b. Giunta G., Bernasconi G., Del Giudice S., Vibroacoustic Monitoring of Gas-Filled Pipelines, ASNT Fall Conference and quality testing show, Las Vegas, 2013. Giunta, G., Bernasconi, G., Method and system for continuous remote monitoring of the integrity of pressurized pipelines and properties of the fluids transported, Patent WO2014096019 A1, 2014. Schiavon, R., Bernasconi, G., Giunta, G., Borghi, G.P., Okere, N., Field deployment of innovative acoustic monitoring system for remote real-time pipeline asset integrity, ADIPEC 2014, Abu Dhabi, SPE 171763, 2014. 10
