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Towards an Enhanced Telluric Compensation Methodology Chijioke Ukiwe & Shamus M c Donnell Hunter M c Donnell Pipelines Services Inc. Presented at AUCSC.

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Presentation on theme: "Towards an Enhanced Telluric Compensation Methodology Chijioke Ukiwe & Shamus M c Donnell Hunter M c Donnell Pipelines Services Inc. Presented at AUCSC."— Presentation transcript:

1 Towards an Enhanced Telluric Compensation Methodology Chijioke Ukiwe & Shamus M c Donnell Hunter M c Donnell Pipelines Services Inc. Presented at AUCSC 2011 by Gord Parker, C.E.T., CP2 Edmonton, Alberta, Canada

2 CONGRESO SOBRE INTEGRIDAD EN INSTALACION DE GAS Y PETROLEO This Work This paper is a progress report of an ongoing R&D project to develop an enhanced Telluric and AC interference compensation methodology.This paper is a progress report of an ongoing R&D project to develop an enhanced Telluric and AC interference compensation methodology. –Research commissioned by Spectrum XLI –Partial funding from the Government of Canada This presentation was previously delivered at the NACE Northern Area Western Conference.This presentation was previously delivered at the NACE Northern Area Western Conference.

3 CONGRESO SOBRE INTEGRIDAD EN INSTALACION DE GAS Y PETROLEO Telluric Current A telluric current (from Latin tellūs, "earth") is an electric current which moves underground or through the sea. The currents are extremely low frequency and travel over large areas at or near the surface of Earth. Telluric currents are also observed in the Earth's crust and mantle.

4 CONGRESO SOBRE INTEGRIDAD EN INSTALACION DE GAS Y PETROLEO Telluric currents are primarily induced by changes in the outer part of the Earth's magnetic field, usually caused by interactions between the solar wind and the magnetosphere or solar radiation effects on the ionosphere.

5 CONGRESO SOBRE INTEGRIDAD EN INSTALACION DE GAS Y PETROLEO Some Telluric Current Facts The magnitude varies, but can be in the order of 100's to 1000's of Amperes. Local variations in the conductivity of the Earth's crust affect the density of these currents as they follow the path of least resistance. –This effect can be used to detect the presence of low-conductivity ore bodies beneath the crust in geological surveys. Along with the currents induced in the Earth's crust, any man-made conducting objects on or beneath the Earth's surface will also have large currents induced in them. –This can cause power grid systems to trip from the overload. High sun-spot activities can buffet the Earth's magnetic field, causing fluctuations which in turn induces telluric currents on earth conductors, increasing the likelihood of such interruptions.

6 CONGRESO SOBRE INTEGRIDAD EN INSTALACION DE GAS Y PETROLEO How do telluric currents affect pipelines?How do telluric currents affect pipelines? The sun emits energy & Particles Earths geo- magnetic field Voltage swings in CP systems during close interval survey CIS Magnetic field Induced electric currents on pipelines Induced electric field Source: space weather Canada

7 CONGRESO SOBRE INTEGRIDAD EN INSTALACION DE GAS Y PETROLEO Telluric currents: economic importance Test Post CSE Pipeline V Voltage Time Pipe-to-soil potential measurement = Possibility of Corrosion Difficulty to pipeline integrity assessment – if uncorrected could result in incorrect interpretation and improper adjustment of CP system

8 CONGRESO SOBRE INTEGRIDAD EN INSTALACION DE GAS Y PETROLEO Telluric on pipe-to-soil potentials: practical exampleTelluric on pipe-to-soil potentials: practical example 5 Seconds grid 2 Seconds CP Interruption Cycle 40 Second Telluric Current Cycle Low frequency Temporal Voltage swing = V at t for any pipeline location Telluric current frequency varies; cycle times of a few seconds to minutes.

9 CONGRESO SOBRE INTEGRIDAD EN INSTALACION DE GAS Y PETROLEO AC Interference on pipe-to-soil potentialsAC Interference on pipe-to-soil potentials Multiple Voltage swings superimposed on the pipe-to-soil Potential: High frequency AC 50/60 Hz Low Frequency telluric 1/40 th Hz 4 second grid 2 second CP Interruption Cycle

10 CONGRESO SOBRE INTEGRIDAD EN INSTALACION DE GAS Y PETROLEO PIPELINE DISTANCE A B CD Telluric Magnitude Regional Effects on pipeline structures on telluric variation: Valves, bends, rectifiers, anodes, insulating flanges Telluric Potential Variation up to ~100 mV/Km at same moment Telluric characteristics: Temporal AND Regional effects At the same moment in time 300mV 100mV 500mV 400mV

11 CONGRESO SOBRE INTEGRIDAD EN INSTALACION DE GAS Y PETROLEO Telluric characteristics: Temporal effects At a given location along the pipeline, PSP changes with time 2. Space weather effects 20+ mV/sec > 100mV / cycle telluric effect has been recorded!

12 CONGRESO SOBRE INTEGRIDAD EN INSTALACION DE GAS Y PETROLEO What is Telluric Compensation? Voltage Time Voltage Exclusion of Noise on PSP Data during CIS

13 CONGRESO SOBRE INTEGRIDAD EN INSTALACION DE GAS Y PETROLEO Basis for Telluric Compensation Stationary PSP data (from stationaryStationary PSP data (from stationary data logger (SDL)) summed over time yields stable average PSP Comparable regional effects ofComparable regional effects of telluric on PSP within several kms SDL PSP data can be used to correctSDL PSP data can be used to correct for any PSP variation in close proximity PSP

14 CONGRESO SOBRE INTEGRIDAD EN INSTALACION DE GAS Y PETROLEO Average PSP? Use statistics carefully, considering duration of temporal effects, and size of data pool.Use statistics carefully, considering duration of temporal effects, and size of data pool. Using data from a short time period, other than the actual survey period can result in error.Using data from a short time period, other than the actual survey period can result in error. There are three kinds of lies: lies, damned lies, and statistics. Benjamin Disraeli ( )

15 CONGRESO SOBRE INTEGRIDAD EN INSTALACION DE GAS Y PETROLEO Current Field Practices for Telluric Compensation 1.Real-time telluric compensation; based on stationary reference electrode placed at start of survey. V + - V Telluric Pipe-to-soil potential variations are corrected real-time SRE Data Logger

16 CONGRESO SOBRE INTEGRIDAD EN INSTALACION DE GAS Y PETROLEO Current Field Practices for Telluric Compensation 1. Real-Time Compensation: pit-falls -Unreliable representative average PSP -Difference in regional telluric effects on pipe can render correction useless Error in compensation increases away from Stationary electrode AB SRE Suppressed Telluric magnitude at B High Telluric magnitude at A X

17 CONGRESO SOBRE INTEGRIDAD EN INSTALACION DE GAS Y PETROLEO Current Field Practices for Telluric Compensation 2.Single Stationary Data Logger Compensation Post Processing For Compensation -Reliable representative average PSP during survey -Difference in regional telluric effects on pipe can render correction useless Differences in regional telluric currents at A & B affect correction method A B SRE + SDL Suppression of Telluric magnitude at B X

18 CONGRESO SOBRE INTEGRIDAD EN INSTALACION DE GAS Y PETROLEO AB 3.Multiple SDL Telluric Correction C Approximately linear telluric profile at any Given time, t within pipe section, AB Current Field Practices for Telluric Compensation

19 CONGRESO SOBRE INTEGRIDAD EN INSTALACION DE GAS Y PETROLEO Multiple SDL Telluric Correction: Underlying Assumptions Based on Distributed Source Transmission Line (DSTL) Theory SDL placement spacing ~ 6 – 8 km Electrical continuity of telluric currents = uniformity of soil and pipeline characteristics Statistical average PSP is calculated from pool of readings that span entire survey period.

20 CONGRESO SOBRE INTEGRIDAD EN INSTALACION DE GAS Y PETROLEO Multiple SDL Telluric Correction SDL-A SDL-B

21 CONGRESO SOBRE INTEGRIDAD EN INSTALACION DE GAS Y PETROLEO Multiple SDL Telluric Correction Enhancements Field work Enhancements Easier and faster Data Post-processing 3-4 SDLs Waveform Log = Strategic SDL Positioning And more reliable results!

22 CONGRESO SOBRE INTEGRIDAD EN INSTALACION DE GAS Y PETROLEO Pipeline ABCD Telluric Magnitude Enhanced Telluric Compensation: unique advantage ~ capturing FULL telluric variation trend along pipeline

23 CONGRESO SOBRE INTEGRIDAD EN INSTALACION DE GAS Y PETROLEO 4 SDL Telluric Compensation Method: example

24 CONGRESO SOBRE INTEGRIDAD EN INSTALACION DE GAS Y PETROLEO PSP Variation (mV) SDL Placement (miles) 4 SDL Telluric Compensation Method: Practical safeguard against error!

25 CONGRESO SOBRE INTEGRIDAD EN INSTALACION DE GAS Y PETROLEO Enhanced Telluric Compensation: Fast Interruption cycle Use of Fast Interruption Cycle of about ~1 second = ON:OFF (~3:1) = <50mV per cycle (simple 1 potential / cycle correction) Longer cycle makes it necessary for independent Telluric correction for ON and Instant Off PSP; different magnitude at start of cycle and end of cycle! Telluric Variation can exceed 50 mV per second times cycle length = significant!

26 CONGRESO SOBRE INTEGRIDAD EN INSTALACION DE GAS Y PETROLEO Multiple SDL Telluric Correction Enhancements: (2) Post-processing (a) Continuous waveform logging of the PSP Need to ensure the same readings are selected from both survey data and SDL – if different technologies used, errors can result

27 CONGRESO SOBRE INTEGRIDAD EN INSTALACION DE GAS Y PETROLEO Multiple SDL Telluric Correction Enhancements: (2) Post-processing (b)Simple moving average system on SDL data before telluric compensation Careful and thorough Choice of each ON and OFF PSP data before Telluric correction using Simple moving averages Of telluric and high Frequency AC interferences

28 CONGRESO SOBRE INTEGRIDAD EN INSTALACION DE GAS Y PETROLEO Multiple SDL Telluric Correction Enhancements: Final Post-processed data

29 CONGRESO SOBRE INTEGRIDAD EN INSTALACION DE GAS Y PETROLEO … Even further telluric enhancements Recent advances in research holds promise for the use of telluric trends to forecast telluric magnitude over longer sections of pipelines = more strategic SDL placements and time of survey.Recent advances in research holds promise for the use of telluric trends to forecast telluric magnitude over longer sections of pipelines = more strategic SDL placements and time of survey. Ability to compensate for high frequency interference; 50/60 Hz AC using high frequency stationary data loggers.Ability to compensate for high frequency interference; 50/60 Hz AC using high frequency stationary data loggers.

30 CONGRESO SOBRE INTEGRIDAD EN INSTALACION DE GAS Y PETROLEO Conclusions The use of 3 ~ 4 Stationary data loggers to track telluric pattern and ensure accurate compensation Fast cycles are preferred to avoid under/over-compensation to either ON or OFF pipe-to-soil potential data Continuous waveform logging can enhance data accuracy Advanced statistical approaches can enhance post-processing and hence, overall pipeline integrity

31 CONGRESO SOBRE INTEGRIDAD EN INSTALACION DE GAS Y PETROLEO Acknowledgement The Authors are grateful to the National Research Council of Canada for financial support through an Industrial Research Assistantship fund

32 CONGRESO SOBRE INTEGRIDAD EN INSTALACION DE GAS Y PETROLEO Questions?


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