1. Seismic Attribute Sensitivity to Energy, Bandwidth, Phase, and Thickness Greg A. Partyka BPAmoco

2. Two Goals 1Review common attributes. 2Summarize attribute sensitivity –to energy, bandwidth, and phase; via simple half- space models. –to thickness; via simple wedge models.

3. Model Descriptions 7 half-space models –Laterally consistent reflectivity –Laterally variable wavelet properties Statics, variable source & receiver coupling, and attenuation are three main causes for laterally variable wavelet properties. 3 wedge models –Laterally consistent wavelet properties. –Laterally variable reflectivity. Lithology, fluid, and thickness are three main causes for laterally variable reflectivity.

4. 0 100 travel-time (ms) energy phase bandwidth 1.0 1.2 1.4 1.6 1.8 energy (amplitude) Energy Model

5. 0 100 travel-time (ms) energy phase bandwidth 8-10-20-30 8-10-26-36 8-10-32-42 8-10-38-48 8-10-44-54 bandwidth (Hz) Bandwidth Model

6. 0 100 travel-time (ms) energy phase bandwidth 0 60 120 180 240 phase (degrees) Phase Model

7. 0 100 travel-time (ms) energy phase bandwidth 8-10-20-30 8-10-26-36 8-10-32-42 8-10-38-48 8-10-44-54 1.0 1.2 1.4 1.6 1.8 bandwidth (Hz) energy (amplitude) Energy-Bandwidth Model

8. 0 100 travel-time (ms) energy phase bandwidth 0 60 120 180 240 phase (degrees) 1.0 1.2 1.4 1.6 1.8 energy (amplitude) Energy-Phase Model

9. 0 100 travel-time (ms) energy phase bandwidth 0 60 120 180 240 phase (degrees) 8-10-20-30 8-10-26-36 8-10-32-42 8-10-38-48 8-10-44-54 bandwidth (Hz) Bandwidth-Phase Model

10. 0 100 travel-time (ms) energy phase bandwidth 0 60 120 180 240 phase (degrees) 8-10-20-30 8-10-26-36 8-10-32-42 8-10-38-48 8-10-44-54 1.0 1.2 1.4 1.6 1.8 bandwidth (Hz) energy (amplitude) Energy-Bandwidth-Phase Model

11. 0 100 0 0 0 0 0 0 travel-time (ms) Real Amplitude - Sensitivity energy phase bandwidth

12. 0 100 travel-time (ms) 200 0 100 travel-time (ms) 200 0 100 travel-time (ms) 200 Blocky Wedge Blocky/Gradational Wedge Gradational Wedge 1.0 reflection coefficients 0.1 Reflectivity Wedge Models

13. 0 100 travel-time (ms) 200 0 100 travel-time (ms) 200 0 100 travel-time (ms) 200 Blocky Wedge Blocky/Gradational Wedge Gradational Wedge 8-10-40-50hz Ormsby filter Real Amplitude RESOLVEDUNRESOLVED

14. Two Classes of Attributes Instantaneous Attributes Response Attributes

15. Instantaneous Attributes Characterize sample-by-sample variability. Include: –real amplitude, –quadrature amplitude, –reflection strength, –instantaneous phase, –cosine of the instantaneous phase, –instantaneous frequency.

16. Real Amplitude Quadrature Amplitude 90 degree phase rotation (or Hilbert transform). Zero-Crossings Peaks & Troughs. Also called “the imaginery part of the seismic trace”.

17. 0 100 0 0 0 0 0 0 travel-time (ms) Quadrature Amplitude - Sensitivity energy phase bandwidth sensitive to: energy bandwidth phase

18. 0 100 travel-time (ms) 200 0 100 travel-time (ms) 200 0 100 travel-time (ms) 200 Blocky Wedge Blocky/Gradational Wedge Gradational Wedge Quadrature Amplitude...zero-crossings can represent bed boundaries, much like bandlimited acoustic impedance. If input data is zero-phase...

19. Real Amplitude Quadrature Amplitude Reflection Strength Phase independent. Always greater-than or equal-to zero. Also referred to as “energy envelope”.

20. 0 100 0 0 0 0 0 0 travel-time (ms) Reflection Strength - Sensitivity energy phase bandwidth 2 0 energy sensitive to: energy bandwidth

21. 0 100 travel-time (ms) 200 0 100 travel-time (ms) 200 0 100 travel-time (ms) 200 Blocky Wedge Blocky/Gradational Wedge Gradational Wedge 2 0 energy 2 0 0.7 0 Reflection Strength Exposes classic tuning behaviour. Lateral variations indicate changes in acoustic contrast and bed thickness.

22. Real Amplitude Quadrature Amplitude Instantaneous Phase Strong and weak events exhibit equal strength. Discontinuous at trough locations (+/-180 degrees). Commonly displayed with a wrapped color bar. 180 -180 0

23. 0 100 0 0 0 0 0 0 travel-time (ms) Instantaneous Phase - Sensitivity energy phase bandwidth sensitive to: bandwidth phase 180 -180 phase (degrees) 0

24. 0 100 travel-time (ms) 200 0 100 travel-time (ms) 200 0 100 travel-time (ms) 200 Blocky Wedge Blocky/Gradational Wedge Gradational Wedge 180 -180 phase (degrees) 0 Instantaneous Phase Emphasizes reflection continuity/discontinuity. highlights: faults pinch-outs angularities boundaries onlap/offlap Strong and weak events exhibit equal strength.

25. Cosine of Instantaneous Phase Real Amplitude Quadrature Amplitude Instantaneous Phase Cosine of Instantaneous Phase Like instantaneous phase, but Avoids the +/-180 degree discontinuity that plagues phase. Can therefore be further processed.

26. 0 100 0 0 0 0 0 0 travel-time (ms) Cosine of Instantaneous Phase - Sensitivity energy phase bandwidth sensitive to: bandwidth phase 1 amplitude 0

27. 0 100 travel-time (ms) 200 0 100 travel-time (ms) 200 0 100 travel-time (ms) 200 Blocky Wedge Blocky/Gradational Wedge Gradational Wedge 1 amplitude 0 Cosine of Instantaneous Phase Emphasizes reflection continuity/discontinuity. highlights: faults pinch-outs angularities boundaries onlap/offlap Strong and weak events exhibit equal strength. Peaks and troughs retain their positions.

28. Real Amplitude Quadrature Amplitude Instantaneous Frequency Instantaneous Phase Rate of change of instantaneous phase. A measure of time-dependent mean frequency.

29. 0 100 0 0 0 0 0 0 travel-time (ms) Instantaneous Frequency - Sensitivity energy phase bandwidth sensitive to: bandwidth 25 10 frequency (Hz)

30. 0 100 travel-time (ms) 200 0 100 travel-time (ms) 200 0 100 travel-time (ms) 200 Blocky Wedge Blocky/Gradational Wedge Gradational Wedge 30 10 frequency (Hz) Instantaneous Frequency Emphasizes tuning characteristics. Characterizes composite tuned reflections. Processing can also artificially reduce frequency.

31. Response Attributes Characterize reflection zones contained within energy envelope lobes. Include: –response energy, –response phase, –response frequency, –response length.

32. Seismic Trace Response Attribute Reflection Strength energy envelope trough positions Response Attributes One constant value per energy envelope.

33. Reflection Strength Response Energy Maximum reflection strength within the envelope lobe.

34. 0 100 0 0 0 0 0 0 travel-time (ms) Response Energy - Sensitivity energy phase bandwidth 2 0 energy sensitive to: energy

35. 0 100 travel-time (ms) 200 0 100 travel-time (ms) 200 0 100 travel-time (ms) 200 Blocky Wedge Blocky/Gradational Wedge Gradational Wedge 2 0 energy 2 0 0.7 0 Response Energy Exposes classic tuning behaviour. Lateral variations indicate changes in acoustic contrasts and bed thickness. Objectively auto-picks and characterizes the zone-of-interest.

36. Response Phase Instantaneous Phase Reflection Strength Response Phase The value of the instantaneous phase at the point at which the envelope is a maximum. A measure of the dominant phase of the waveform contained within the energy envelope lobe. 180 -180 0

37. 0 100 0 0 0 0 0 0 travel-time (ms) Response Phase - Sensitivity energy phase bandwidth sensitive to: phase 180 -180 phase (degrees) 0

38. 0 100 travel-time (ms) 200 0 100 travel-time (ms) 200 0 100 travel-time (ms) 200 Blocky Wedge Blocky/Gradational Wedge Gradational Wedge 180 -180 phase (degrees) 0 Response Phase Sharp lateral changes can indicate detection-to-resolution transitions. Lateral variations reveal changes in tuning. Objectively auto-picks and characterizes the zone-of-interest.

39. Response Frequency Instantaneous Frequency Reflection Strength Response Frequency The value of the instantaneous phase at the point at which the envelope is a maximum. A measure of the dominant frequency of the waveform contained within the energy envelope lobe.

40. 0 100 0 0 0 0 0 0 travel-time (ms) Response Frequency - Sensitivity energy phase bandwidth sensitive to: bandwidth 25 10 frequency (Hz)

41. 0 100 travel-time (ms) 200 0 100 travel-time (ms) 200 0 100 travel-time (ms) 200 Blocky Wedge Blocky/Gradational Wedge Gradational Wedge 30 10 frequency (Hz) Response Frequency Emphasizes tuning characteristics. Characterizes composite tuned reflections. Objectively auto-picks and characterizes the zone-of-interest.

42. Response Attributes As a group, response energy, response phase, and response frequency describe the complementary dominant seismic characteristics within an energy envelope. –Response energy is sensitive to maximum energy; –Response phase is sensitive to dominant phase; and –Response frequency is sensitive to dominant frequency.

43. Reflection Strength Response Length Half-length of the energy envelope lobe.

44. 0 100 0 0 0 0 0 0 travel-time (ms) Response Length - Sensitivity energy phase bandwidth sensitive to: bandwidth 51 16 duration (milliseconds)

45. 0 100 travel-time (ms) 200 0 100 travel-time (ms) 200 0 100 travel-time (ms) 200 Blocky Wedge Blocky/Gradational Wedge Gradational Wedge 40 15 duration (milliseconds) Response Length Exposes detection-to-resolution transitions. A measure of seismic waveform stability. Objectively auto-picks and characterizes the zone-of-interest.

46. FrequencyEnergyPhase Attribute Dependence Attribute real amplitude quadrature amplitude reflection strength instantaneous phase cosine of instantaneous phase instantaneous frequency response energy response phase response frequency response length

47. Summary Effective use of seismic attributes requires understanding attribute sensitivity. Simple models allow geoscientists to examine and understand attribute sensitivity.