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Noise Reduction in Vibroseis Source

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Presentation on theme: "Noise Reduction in Vibroseis Source"— Presentation transcript:

1 Noise Reduction in Vibroseis Source
Kaelig Castor, Thomas Bianchi, Olivier Winter, Thierry Klein

2 Noise Reduction in Vibroseis Ground Force : Outline
Harmonic Noise in Ground Force delivered by a Vibrator Noise Cancellation Adaptive Algorithm Acquisition Quality and Productivity Benefits Examples of Real Seismic Data Based on the interference principle, the noise can be removed directly at the emission by an effect which is called phase cancellation SEG Denver 2014 – Noise Reduction in Vibroseis Source

3 Noise Reduction in Vibroseis Ground Force : Outline
Harmonic Noise in Ground Force delivered by a Vibrator Noise Cancellation Adaptive Algorithm Acquisition Quality and Productivity Benefits Examples of Real Seismic Data Based on the interference principle, the noise can be removed directly at the emission by an effect which is called phase cancellation SEG Denver 2014 – Noise Reduction in Vibroseis Source

4 Seismic Vibrator: A Nonlinear Source
Intrinsical nonlinear behaviour of hydraulic actuator Baseplate/ground nonlinearities both due to soil plasticity and intermittent contact Geometrical nonlinear effects composed by nonlinear vibrating mode coupling Reference Pilot (Input) Ground Force (Output) Actuator Baseplate SEG Denver 2014 – Noise Reduction in Vibroseis Source

5 Harmonic Distortion Before Correlation After Correlation t

6 Harmonic Distortion Before Correlation After Correlation Time (s)

7 Classic Ground Force Quality Control
dB AC(Ref) Input (reference pilot) dB dB CC(GF,Ref) Output (ground force) 3rd Harmo 2nd Harmo local_140112_ _dsd06.segd 20s Hz crosscorrelation wavelet in dB scale It is used to analyse the ground force versus reference input signal Good QC can be to make sure the distortion is low enough in negative time like here at -40dB or far enough in negative time. Fundamental SEG Denver 2014 – Noise Reduction in Vibroseis Source Time (s) Time (s) Time (s)

8 Classic Ground Force Quality Control
dB AC(Ref) Input (reference pilot) dB dB CC(GF,Ref) Output (ground force) 3rd Harmo 2nd Harmo local_140112_ _dsd06.segd 20s Hz crosscorrelation wavelet in dB scale It is used to analyse the ground force versus reference input signal Good QC can be to make sure the distortion is low enough in negative time like here at -40dB or far enough in negative time. Fundamental SEG Denver 2014 – Noise Reduction in Vibroseis Source Time (s) Time (s) Time (s)

9 Classic Ground Force Quality Control
SEG Denver 2014 – Noise Reduction in Vibroseis Source

10 Distortion Effect on Seismic Flip-Flop
Record Record Somehow harmonic distortion has often been considered as an inherent vibrator constraint. SlipTime is taken sufficiently high to prevent any noise contamination so even if it does not impact directly the quality control in a standard acquisition, It is important to remind that harmonic noise contamination has a cost. Decreasing the harmonic noise not only improve the data quality but trends to increase acquisition productivity.

11 Distortion Effect on Seismic Flip-Flop
Record Record Somehow harmonic distortion has often been considered as an inherent vibrator constraint. SlipTime is taken sufficiently high to prevent any noise contamination so even if it does not impact directly the quality control in a standard acquisition, It is important to remind that harmonic noise contamination has a cost. Decreasing the harmonic noise not only improve the data quality but trends to increase acquisition productivity.

12 Distortion Effect on Seismic Flip-Flop
Record Record Somehow harmonic distortion has often been considered as an inherent vibrator constraint. SlipTime is taken to prevent any noise contamination so even if it does not impact directly the quality control in a standard acquisition, It is important to remind that harmonic noise contamination has a cost. Decreasing the harmonic noise not only improve the data quality but trends to increase acquisition productivity.

13 Distortion Effect on Seismic Slip-Sweep, Slip-Time = 18s
Record Record Somehow harmonic distortion has often been considered as an inherent vibrator constraint. SlipTime is taken to prevent any noise contamination so even if it does not impact directly the quality control in a standard acquisition, It is important to remind that harmonic noise contamination has a cost. Decreasing the harmonic noise not only improve the data quality but trends to increase acquisition productivity.

14 Distortion Effect on Seismic Slip-Sweep, Slip-Time = 12s
Record Record Somehow harmonic distortion has often been considered as an inherent vibrator constraint. SlipTime is taken to prevent any noise contamination so even if it does not impact directly the quality control in a standard acquisition, It is important to remind that harmonic noise contamination has a cost. Decreasing the harmonic noise not only improve the data quality but trends to increase acquisition productivity.

15 Distortion Effect on Seismic
Flip-flop (slight issue solved by doing upsweep) Slip-sweep (method post acquisition during processing to remove the harmonic noise) Broadband low frequency sweep (distortion is low-frequency noise in positive time and low and high frequency noise in negative time) Noise reduction at the emission The only way to handle the harmonic noise contamination is to have a high time between successive shots. In order not to record any distortion noise, we have to use flip-flop. In case we want to increase productivity, slip-sweep acquisition can be done. It consists in decreasing the slip-time. SEG Denver 2014 – Noise Reduction in Vibroseis Source

16 Noise Reduction in Vibroseis Ground Force : Outline
Harmonic Noise in Ground Force delivered by a Vibrator Noise Cancellation Adaptive Algorithm Acquisition Quality and Productivity Benefits Example of Real Seismic Data Based on the interference principle, the noise can be removed directly at the emission by an effect which is called phase cancellation SEG Denver 2014 – Noise Reduction in Vibroseis Source

17 Source Noise Reduction Method: Adaptative Algorithm
Learning process: Iterative computation of a new input pilot signal Input New Reference Pilot Signal = Fundamental + Anti-Noise Output Ground Force = Fundamental + Noise Vibrator electronics Learning process that tunes adequately each vibrator at a specific drive level to reach an ideal anti-noise pilot signal SEG Denver 2014 – Noise Reduction in Vibroseis Source

18 Convergence of an Anti-Noise Reference Pilot on a Static Location

19 Convergence of an Anti-Noise Reference Pilot on a Static Location

20 Convergence of an Anti-Noise Reference Pilot on a Static Location

21 Convergence of an Anti-Noise Reference Pilot on a Static Location

22 Convergence of an Anti-Noise Reference Pilot on a Static Location

23 Time-Frequency plot of the Averaged Ground Force
CLASSIC NOISE REDUCTION Noiseless zone Strong reduction 60% reduction 2 zones 1 no noise (40dB ie less than 1% noise) during 8s clean (only fundamental is emitted below 10Hz- 15Hz) Whit Dash line is the noiseless zone For one single dsd in various locations 40% reduction

24 Time Signal of the Averaged Ground Force
Between triangular and The "Shark fin" waveform SEG Denver 2014 – Noise Reduction in Vibroseis Source

25 Enveloppe of the Averaged Ground Force
Noiseless zone SEG Denver 2014 – Noise Reduction in Vibroseis Source

26 Noise Reduction in Vibroseis Ground Force : Outline
Harmonic Noise in Ground Force delivered by a Vibrator Noise Cancellation Adaptative Algorithm Acquisition Quality and Productivity Benefits Examples of Real Seismic Data Based on the interference principle, the noise can be removed directly at the emission by an effect which is called phase cancellation SEG Denver 2014 – Noise Reduction in Vibroseis Source

27 Comparison of a Low-Dwell Sweep and its Equivalent Linear Sweep (same sweep rate)
Example of comparison beween a low-dwell sweep and its equivalent linear sweep with the same sweep rate. Fig. 5a shows the instantaneous frequency. Time-frequency repartition of harmonic-noise are shown before correlation for the single low-dwell sweep including its noiseless zone from our method (Fig. 5b) SEG Denver 2014 – Noise Reduction in Vibroseis Source

28 Distortion Effect on Seismic Classic Sweep, Flip-Flop
Record Record Somehow harmonic distortion has often been considered as an inherent vibrator constraint. SlipTime is taken to prevent any noise contamination so even if it does not impact directly the quality control in a standard acquisition, It is important to remind that harmonic noise contamination has a cost. Decreasing the harmonic noise not only improve the data quality but trends to increase acquisition productivity.

29 Distortion Effect on Seismic Clean Sweep, Flip-Flop
Record Record Somehow harmonic distortion has often been considered as an inherent vibrator constraint. SlipTime is taken to prevent any noise contamination so even if it does not impact directly the quality control in a standard acquisition, It is important to remind that harmonic noise contamination has a cost. Decreasing the harmonic noise not only improve the data quality but trends to increase acquisition productivity.

30 Distortion Effect on Seismic Classic Sweep, Slip-Sweep, Slip-Time = 12s
Record Record Somehow harmonic distortion has often been considered as an inherent vibrator constraint. SlipTime is taken to prevent any noise contamination so even if it does not impact directly the quality control in a standard acquisition, It is important to remind that harmonic noise contamination has a cost. Decreasing the harmonic noise not only improve the data quality but trends to increase acquisition productivity.

31 Distortion Effect on Seismic Clean Sweep, Slip-Sweep, Slip-Time = 12s
Record Record Somehow harmonic distortion has often been considered as an inherent vibrator constraint. SlipTime is taken to prevent any noise contamination so even if it does not impact directly the quality control in a standard acquisition, It is important to remind that harmonic noise contamination has a cost. Decreasing the harmonic noise not only improve the data quality but trends to increase acquisition productivity.

32 Harmonic Noise Self-Contamination Flip-Flop, Classic

33 Harmonic Noise Self-Contamination Flip-Flop, Noise Reduction

34 Noise Reduction in Vibroseis Ground Force : Outline
Harmonic Noise in Ground Force delivered by a Vibrator Noise Cancellation Adaptive Algorithm Acquisition Quality and Productivity Benefits Examples of Real Seismic Data Based on the interference principle, the noise can be removed directly at the emission by an effect which is called phase cancellation SEG Denver 2014 – Noise Reduction in Vibroseis Source

35 Classic Sweep Harmonic distortion from current shot (in slip-sweep or flip-flop) Harmonic distortion from next shot (only in slip-sweep)

36 Clean Sweep Harmonic distortion from next shot (only in slip-sweep) Harmonic distortion from current shot (in slip-sweep or flip-flop)

37 Slip-Sweep Shot-point for Classic Sweep (Low Pass Filter 15Hz)

38 Slip-Sweep Shot-point for Clean Sweep (Low Pass Filter 15Hz)

39 Conclusion Harmonic Noise is one of the VibroSeis source contraints in term of data quality and productivity. The proposed method works on the full bandwidth and is totally efficient at low frequency. Reduction of harmonic distortion at the emission gives : Improved delivered data (« self-harmonic noise » pollution for low-dwell sweeps not even emitted) easier to process, especially clean first arrivals eases Full-Waveform Inversion Increased productivity in slip-sweep acquisition : slip-time can be decreased

40 Thank you

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