Towards an Enhanced Towards an Enhanced Telluric Compensation Telluric Compensation Methodology Methodology Chijioke Ukiwe & Shamus M Chijioke Ukiwe & Shamus M c c Donnell Donnell Hunter M Hunter M c c Donnell Pipelines Services Inc. Donnell Pipelines Services Inc. Presented at AUCSC 2011 by Gord Parker, Presented at AUCSC 2011 by Gord Parker, C.E.T., CP2 C.E.T., CP2 Edmonton, Alberta, Canada Edmonton, Alberta, Canada
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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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Towards an Enhanced Telluric Towards an Enhanced Telluric Compensation MethodologyCompensation Methodology
Presented at AUCSC 2011 by Gord Parker, C.E.T., CP2Presented at AUCSC 2011 by Gord Parker, C.E.T., CP2Edmonton, Alberta, CanadaEdmonton, Alberta, Canada
CONGRESO SOBRE INTEGRIDAD EN INSTALACION DE GAS Y PETROLEO
This WorkThis Work• This paper is a progress report of an ongoing R&D This paper is a progress report of an ongoing R&D
project to develop an enhanced Telluric and AC project to develop an enhanced Telluric and AC interference compensation methodology.interference compensation methodology.– Research commissioned by Spectrum XLIResearch commissioned by Spectrum XLI– Partial funding from the Government of CanadaPartial funding from the Government of Canada
• This presentation was previously delivered at the This presentation was previously delivered at the NACE Northern AreaNACE Northern Area Western Conference.Western Conference.
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.
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.
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.
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
Earth’s geo-
magnetic field
Voltage swings in CP systemsduring close interval survey CIS
Magnetic field
Induced electric currents on pipelines
Induced electric field
Source: space weather Canada
CONGRESO SOBRE INTEGRIDAD EN INSTALACION DE GAS Y PETROLEO
At a given locationalong the pipeline,PSP changes with time
2. Space weather effects
20+ mV/sec
> 100mV / cycle telluric effect has been recorded!
CONGRESO SOBRE INTEGRIDAD EN INSTALACION DE GAS Y PETROLEO
What is “Telluric Compensation”?What is “Telluric Compensation”?
Voltage
Time
Time
VoltageExclusion of“Noise” on PSPData during CIS
CONGRESO SOBRE INTEGRIDAD EN INSTALACION DE GAS Y PETROLEO
Basis for Telluric CompensationBasis for Telluric Compensation
• Stationary PSP data (from stationaryStationary PSP data (from stationarydata logger (SDL)) summed over data logger (SDL)) summed over time yields “stable” time yields “stable” average PSPaverage PSP
• Comparable regional effects of Comparable regional effects of telluric on PSP within several kmstelluric on PSP within several kms
• SDL PSP data can be used to correctSDL PSP data can be used to correctfor any PSP variation in closefor any PSP variation in closeproximity proximity
PSP
PSP
CONGRESO SOBRE INTEGRIDAD EN INSTALACION DE GAS Y PETROLEO
Average PSP?Average PSP?
• Use statistics carefully, considering Use statistics carefully, considering duration of temporal effects, and size of duration of temporal effects, and size of data pool.data pool.
• Using data from a short time period, other Using data from a short time period, other than the actual survey period can result in than the actual survey period can result in error.error.
There are three kinds of lies: lies, damned lies, and statistics.
Benjamin Disraeli (1804 - 1881)
CONGRESO SOBRE INTEGRIDAD EN INSTALACION DE GAS Y PETROLEO
Current Field Practices for Telluric CompensationCurrent Field Practices for Telluric Compensation
1.1. Real-time telluric compensation; Real-time telluric compensation; based on stationary reference electrode placed at start of survey.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
CONGRESO SOBRE INTEGRIDAD EN INSTALACION DE GAS Y PETROLEO
Current Field Practices for Telluric CompensationCurrent Field Practices for Telluric Compensation
- Unreliable representative average PSPUnreliable representative average PSP- Difference in Difference in regional telluric effectsregional telluric effects on pipe can render correction useless on pipe can render correction useless
Error in compensation increases away from Stationary electrode
A B
SRE Suppressed Telluric magnitude at B
High Telluric magnitude
at AX
CONGRESO SOBRE INTEGRIDAD EN INSTALACION DE GAS Y PETROLEO
Current Field Practices for Telluric CompensationCurrent Field Practices for Telluric Compensation
2.2. Single Stationary Data Logger CompensationSingle Stationary Data Logger CompensationPost Processing For CompensationPost Processing For Compensation
- Reliable representative Reliable representative average PSP average PSP during surveyduring survey- Difference in Difference in regional telluric effectsregional telluric effects on pipe can on pipe can
render correction uselessrender correction uselessDifferences in regionaltelluric currents at A & Baffect correction method
A B
SRE + SDL
Suppression of Telluric magnitude at BX
CONGRESO SOBRE INTEGRIDAD EN INSTALACION DE GAS Y PETROLEO
A B
3. Multiple SDL Telluric Correction
C
Approximately linear telluric profile at anyGiven time, “t” within pipe section, AB
Current Field Practices for Telluric CompensationCurrent Field Practices for Telluric Compensation
CONGRESO SOBRE INTEGRIDAD EN INSTALACION DE GAS Y PETROLEO
capturing FULL telluric variation trend along pipelinecapturing FULL telluric variation trend along pipeline
CONGRESO SOBRE INTEGRIDAD EN INSTALACION DE GAS Y PETROLEO
4 SDL Telluric Compensation Method: example
Telluric PSP Variation
-50
0
50
100
150
200
250
300
56440 56540 56640 56740 56840 56940 57040
Time (Sec.)
Te
llu
ric
Ma
gn
itu
de
(m
V)
MP: 496.1 MP: 500.0 MP: 502.3 MP: 503.5
CONGRESO SOBRE INTEGRIDAD EN INSTALACION DE GAS Y PETROLEO
PSPVariation(mV)
500.0 502.3496.1 503.5
SDL Placement (miles)
4 SDL Telluric Compensation Method:Practical safeguard against error!
CONGRESO SOBRE INTEGRIDAD EN INSTALACION DE GAS Y PETROLEO
Enhanced Telluric Compensation: Fast Interruption cycle Enhanced Telluric Compensation: Fast Interruption cycle
•Use of Fast InterruptionCycle 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 exceed50 mV per secondtimes cycle length = significant!
CONGRESO SOBRE INTEGRIDAD EN INSTALACION DE GAS Y PETROLEO
Multiple SDL Telluric Correction Enhancements:
(2) Post-processing
(a) Continuous waveform logging of the PSP (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
CONGRESO SOBRE INTEGRIDAD EN INSTALACION DE GAS Y PETROLEO
Multiple SDL Telluric Correction Enhancements:
(2) Post-processing
(b)(b) Simple moving average system on SDL data before telluricSimple moving average system on SDL data before telluric
compensationcompensation
Careful and thoroughChoice of each ON andOFF PSP data beforeTelluric correction usingSimple moving averagesOf telluric and highFrequency AC interferences
CONGRESO SOBRE INTEGRIDAD EN INSTALACION DE GAS Y PETROLEO
Multiple SDL Telluric Correction Enhancements: Final Post-processed data
CONGRESO SOBRE INTEGRIDAD EN INSTALACION DE GAS Y PETROLEO
… … Even further telluric enhancementsEven further telluric enhancements
• Recent advances in research holds promise for the use Recent advances in research holds promise for the use of telluric trends to forecast telluric magnitude over of telluric trends to forecast telluric magnitude over longer sections of pipelines = more strategic SDL longer sections of pipelines = more strategic SDL placements and time of survey.placements and time of survey.
• Ability to compensate for high frequency interference; Ability to compensate for high frequency interference; 50/60 Hz AC using high frequency stationary data 50/60 Hz AC using high frequency stationary data loggers.loggers.
CONGRESO SOBRE INTEGRIDAD EN INSTALACION DE GAS Y PETROLEO
ConclusionsConclusions
• The use of 3 ~ 4 Stationary data loggers to track telluric patternand ensure accurate compensation
• Fast cycles are preferred to avoid under/over-compensationto either ON or OFF pipe-to-soil potential data
• Continuous waveform logging can enhance data accuracy