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Seismic Thickness Estimation: Three Approaches, Pros and Cons

Seismic Thickness Estimation: Three Approaches, Pros and Cons. Gregory A. Partyka bp. Outline. Introduction Three Approaches Examples Pros and Cons. Outline. Introduction Three Approaches Examples Pros and Cons. 40. 0. 10. 20. 30. 50. Blocky Wedge Model. REFLECTIVITY. 366.

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Seismic Thickness Estimation: Three Approaches, Pros and Cons

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  1. Seismic Thickness Estimation: Three Approaches, Pros and Cons Gregory A. Partyka bp

  2. Outline • Introduction • Three Approaches • Examples • Pros and Cons

  3. Outline • Introduction • Three Approaches • Examples • Pros and Cons

  4. 40 0 10 20 30 50 Blocky Wedge Model REFLECTIVITY 366 400 Travel Time (ms) 432 466 Temporal Thickness (ms)

  5. 366 400 Travel Time (ms) 432 466 40 40 0 0 10 10 20 20 30 30 50 50 Amplitude +0.025 -0.025 Blocky Wedge Model REFLECTIVITY 366 400 Travel Time (ms) 432 466 Temporal Thickness (ms) BANDLIMITED REFLECTIVITY (8-10-40-50hz) Temporal Thickness (ms)

  6. 366 400 Travel Time (ms) 432 466 40 40 0 0 10 10 20 20 30 30 50 50 Amplitude +0.025 -0.025 Blocky Wedge Model REFLECTIVITY 366 400 Travel Time (ms) 432 466 Temporal Thickness (ms) BANDLIMITED REFLECTIVITY (8-10-40-50hz) Temporal Thickness (ms)

  7. Outline • Introduction • Three Approaches • Examples • Pros and Cons

  8. Three Approaches to Thickness Estimation • Conventional • peak-trough time separation • amplitude • Spectral Decomposition • 1st dominant frequency and amplitude • Spectral Decomposition • discrete frequency components

  9. Three Approaches to Thickness Estimation • Conventional • peak-trough time separation • amplitude • Spectral Decomposition • 1st dominant frequency and amplitude • Spectral Decomposition • discrete frequency components

  10. 366 400 Travel Time (ms) 432 466 40 40 0 0 10 10 20 20 30 30 50 50 Amplitude +0.025 -0.025 Conventional Thickness Estimation REFLECTIVITY 366 400 Travel Time (ms) 432 466 Temporal Thickness (ms) BANDLIMITED REFLECTIVITY (8-10-40-50hz) Temporal Thickness (ms)

  11. 366 400 Travel Time (ms) 432 466 40 40 0 0 10 10 20 20 30 30 50 50 Amplitude +0.025 -0.025 Conventional Thickness Estimation REFLECTIVITY 366 400 Travel Time (ms) 432 466 Temporal Thickness (ms) BANDLIMITED REFLECTIVITY (8-10-40-50hz) tuning thickness Temporal Thickness (ms) Widess, M.B., 1973, How Thin is a Thin Bed?, Geophysics, vol. 38, pg 1176-1180. Kallweitt, R.S. and Wood, L.C, 1982, The Limits of Resolution of Zero-Phase Wavelets, Geophysics, vol.47, pg 1035-1046.

  12. 366 400 Travel Time (ms) 432 466 40 40 40 0 0 0 10 10 10 20 20 20 30 30 30 50 50 50 Amplitude +0.025 -0.025 Conventional Thickness Estimation REFLECTIVITY 1 1.4 * frequency 366 tuning thickness = upper 400 Travel Time (ms) 432 50 -0.0000 45 466 40 -0.0050 35 Temporal Thickness (ms) BANDLIMITED REFLECTIVITY (8-10-40-50hz) -0.0100 30 Largest Negative Amplitude Peak-Trough Time Separation (ms) 25 20 -0.0150 15 -0.0200 10 5 tuning thickness tuning thickness -0.0250 0 Temporal Thickness (ms) Temporal Thickness (ms) Widess, M.B., 1973, How Thin is a Thin Bed?, Geophysics, vol. 38, pg 1176-1180. Kallweitt, R.S. and Wood, L.C, 1982, The Limits of Resolution of Zero-Phase Wavelets, Geophysics, vol.47, pg 1035-1046.

  13. Three Approaches to Thickness Estimation • Conventional • peak-trough time separation • amplitude • Spectral Decomposition • 1st dominant frequency and amplitude • Spectral Decomposition • discrete frequency components

  14. Spectral Decomposition • uses the discrete Fourier transform to: • quantify thin-bed interference, and • detect subtle discontinuities.

  15. Source Wavelet Amplitude Spectrum Source Wavelet Reflected Wavelets Thin Bed Reflection Thin Bed Reflection Amplitude Spectrum 1 Amplitude Amplitude Temporal Thickness Frequency Frequency Fourier Transform Fourier Transform Acoustic Impedance Reflectivity Thin Bed Temporal Thickness Spectral Interference • The spectral interference pattern is imposed by the distribution of acoustic properties within the short analysis window. Paryka, Gridley and Lopez, The Leading Edge, vol 18, no 3, 1999

  16. 40 0 10 20 30 50 Blocky Wedge Model REFLECTIVITY 366 400 Travel Time (ms) 432 466 Temporal Thickness (ms)

  17. 366 400 Travel Time (ms) 432 466 40 40 0 0 10 10 20 20 30 30 50 50 0 Amplitude 0.0014 50 100 0 Frequency (Hz) 150 200 250 Spectral Interference REFLECTIVITY Temporal Thickness (ms) SPECTRALAMPLITUDE Temporal Thickness (ms)

  18. 366 400 Travel Time (ms) 432 466 40 40 0 0 10 10 20 20 30 30 50 50 0 Amplitude 0.0014 50 100 0 Frequency (Hz) 150 200 250 Spectral Interference and Frequency REFLECTIVITY Temporal Thickness The temporal thickness of the wedge (t), determines the period of notching in the amplitude spectrum (Pf) with respect to frequency. Temporal Thickness (ms) SPECTRALAMPLITUDE Pf = 1/t 1 Temporal Thickness Temporal Thickness (ms)

  19. 366 400 Travel Time (ms) 432 466 40 40 0 0 10 10 20 20 30 30 50 50 0 Amplitude 0.0014 50 100 0 Frequency (Hz) 150 200 250 Spectral Interference and Thickness REFLECTIVITY The value of the frequency component (f), determines the period of notching in the amplitude spectrum (Pt) with respect to bed thickness. Temporal Thickness (ms) SPECTRALAMPLITUDE Pt = 1/ f 1 Frequency Temporal Thickness (ms)

  20. 366 366 400 400 Travel Time (ms) Travel Time (ms) 432 432 466 466 40 40 40 40 0 0 0 0 10 10 10 10 20 20 20 20 30 30 30 30 50 50 50 50 0 0 Amplitude Amplitude Amplitude 0.0014 0.0014 +0.025 50 50 100 100 -0.025 0 0 Frequency (Hz) Frequency (Hz) 150 150 200 200 250 250 Spectral Interference REFLECTIVITY BANDLIMITED REFLECTIVITY (8-10-40-50hz) Temporal Thickness (ms) Temporal Thickness (ms) SPECTRALAMPLITUDE BANDLIMITED SPECTRALAMPLITUDE Bandwidth 8-10-40-50 Temporal Thickness (ms) Temporal Thickness (ms)

  21. 366 400 Travel Time (ms) 432 466 40 40 0 0 10 10 20 20 30 30 50 50 Amplitude Amplitude +0.025 0.0014 0 -0.025 Spectral Interference BANDLIMITED REFLECTIVITY (8-10-40-50hz) Temporal Thickness (ms) BANDLIMITED SPECTRALAMPLITUDE 0 Bandwidth 8-10-40-50 25 50 Frequency (Hz) 75 100 125 Temporal Thickness (ms)

  22. 366 400 Travel Time (ms) 432 466 40 40 0 0 10 10 20 20 30 30 50 50 Amplitude Amplitude +0.025 0.0014 -0.025 0 Thickness via 1st Dominant Frequency and Amplitude BANDLIMITED REFLECTIVITY (8-10-40-50hz) Temporal Thickness (ms) BANDLIMITED SPECTRALAMPLITUDE 0 Bandwidth 8-10-40-50 25 50 Frequency (Hz) 75 1st Dominant Frequency 100 125 Temporal Thickness (ms)

  23. Frequencyupper and Frequency1st-dominant 1 1.4 * frequency 1 2 * frequency = tuning thickness = upper 1st-dominant

  24. 366 400 Travel Time (ms) 432 466 40 40 40 0 0 0 10 10 10 20 20 20 30 30 30 50 50 50 Amplitude Amplitude +0.025 0.0014 -0.025 0 Thickness via 1st Dominant Frequency and Amplitude BANDLIMITED REFLECTIVITY (8-10-40-50hz) 1 2 * frequency tuning thickness = 1st-dominant 1 2 * 36hz 0.014sec = 0.0014 40 Temporal Thickness (ms) 35 0.0012 BANDLIMITED SPECTRALAMPLITUDE 30 0 25 0.0008 Bandwidth 8-10-40-50 25 1st Dominant Frequency 1st Dominant Amplitude 20 50 0.0006 15 Frequency (Hz) 75 1st Dominant Frequency 10 0.0002 100 5 tuning thickness tuning thickness 0.0000 0 125 Temporal Thickness (ms) Temporal Thickness (ms)

  25. Three Approaches to Thickness Estimation • Conventional • peak-trough time separation • amplitude • Spectral Decomposition • 1st dominant frequency and amplitude • Spectral Decomposition • discrete frequency components

  26. 366 400 Travel Time (ms) 432 466 40 40 0 0 10 10 20 20 30 30 50 50 Amplitude Amplitude +0.025 0.0014 0 -0.025 Spectral Interference BANDLIMITED REFLECTIVITY (8-10-40-50hz) Temporal Thickness (ms) BANDLIMITED SPECTRALAMPLITUDE 0 Bandwidth 8-10-40-50 25 50 Frequency (Hz) 75 100 125 Temporal Thickness (ms)

  27. 0.0014 366 0.0012 400 0.0010 Travel Time (ms) 432 0.0008 Amplitude 466 0.0006 0.0004 40 40 40 0 0 0 10 10 10 20 20 20 30 30 30 50 50 50 0.0002 Amplitude Amplitude +0.025 0.0014 0.0000 Temporal Thickness (ms) 0 -0.025 Thickness via Discrete Frequency Components BANDLIMITED REFLECTIVITY (8-10-40-50hz) 1 2 * frequency tuning thickness = 1st-dominant 1 2 * 10hz 0.050sec = 10hz amp Temporal Thickness (ms) BANDLIMITED SPECTRALAMPLITUDE 0 10hz 25 50 Frequency (Hz) 75 10hz tuning thickness 10hz tuning thickness 100 125 Temporal Thickness (ms)

  28. 0.0014 366 0.0012 400 0.0010 Travel Time (ms) 432 0.0008 Amplitude 466 0.0006 0.0004 40 40 40 0 0 0 10 10 10 20 20 20 30 30 30 50 50 50 0.0002 Amplitude Amplitude +0.025 0.0014 0.0000 Temporal Thickness (ms) 0 -0.025 Thickness via Discrete Frequency Components BANDLIMITED REFLECTIVITY (8-10-40-50hz) 1 2 * frequency tuning thickness = 1st-dominant 1 2 * 20hz 0.025sec = 20hz amp Temporal Thickness (ms) BANDLIMITED SPECTRALAMPLITUDE 0 20hz 25 50 Frequency (Hz) 75 20hz tuning thickness 20hz tuning thickness 100 125 Temporal Thickness (ms)

  29. 0.0014 366 0.0012 400 0.0010 Travel Time (ms) 432 0.0008 Amplitude 466 0.0006 0.0004 40 40 40 0 0 0 10 10 10 20 20 20 30 30 30 50 50 50 0.0002 Amplitude Amplitude +0.025 0.0014 0.0000 Temporal Thickness (ms) 0 -0.025 Thickness via Discrete Frequency Components BANDLIMITED REFLECTIVITY (8-10-40-50hz) 1 2 * frequency tuning thickness = 1st-dominant 1 2 * 30hz 0.017sec = 30hz amp Temporal Thickness (ms) BANDLIMITED SPECTRALAMPLITUDE 0 25 30hz 50 Frequency (Hz) 75 30hz tuning thickness 30hz tuning thickness 100 125 Temporal Thickness (ms)

  30. 0.0014 366 0.0012 400 0.0010 Travel Time (ms) 432 0.0008 Amplitude 466 0.0006 0.0004 40 40 40 0 0 0 10 10 10 20 20 20 30 30 30 50 50 50 0.0002 Amplitude Amplitude +0.025 0.0014 0.0000 Temporal Thickness (ms) 0 -0.025 Thickness via Discrete Frequency Components BANDLIMITED REFLECTIVITY (8-10-40-50hz) 1 2 * frequency tuning thickness = 1st-dominant 10hz amp 20hz amp Temporal Thickness (ms) 30hz amp BANDLIMITED SPECTRALAMPLITUDE 0 10hz 20hz 25 30hz 50 Frequency (Hz) 75 30hz tuning thickness 20hz tuning thickness 10hz tuning thickness 30hz tuning thickness 20hz tuning thickness 10hz tuning thickness 100 125 Temporal Thickness (ms)

  31. 0.0014 366 0.0012 400 0.0010 Travel Time (ms) 432 0.0008 Amplitude 466 0.0006 0.0004 40 40 40 0 0 0 10 10 10 20 20 20 30 30 30 50 50 50 0.0002 Amplitude Amplitude 0.0014 +0.025 0.0000 Temporal Thickness (ms) 0 -0.025 Thickness via Discrete Frequency Components BANDLIMITED REFLECTIVITY (8-10-40-50hz) By choosing an appropriately-low frequency component, the entire range of possible thickness is forced below the tuning thickness, and therefore can be quantified using amplitude variability alone. 10hz amp 20hz amp Temporal Thickness (ms) 30hz amp BANDLIMITED SPECTRALAMPLITUDE 0 10hz 20hz 25 30hz 50 Frequency (Hz) 75 30hz tuning thickness 20hz tuning thickness 10hz tuning thickness 30hz tuning thickness 20hz tuning thickness 10hz tuning thickness 100 125 Temporal Thickness (ms)

  32. 366 400 Travel Time (ms) 432 466 40 40 40 0 0 0 10 10 10 20 20 20 30 30 30 50 50 50 Amplitude Amplitude 0.0014 +0.025 0 -0.025 Thickness via 1st Dominant Frequency and Amplitude BANDLIMITED REFLECTIVITY (8-10-40-50hz) 1 2 * frequency tuning thickness = 1st-dominant 0.0014 40 Temporal Thickness (ms) 35 0.0012 BANDLIMITED SPECTRALAMPLITUDE 30 0 25 0.0008 Bandwidth 8-10-40-50 25 1st Dominant Frequency 1st Dominant Amplitude 20 50 0.0006 15 Frequency (Hz) 75 1st Dominant Frequency 10 30hz tuning thickness 20hz tuning thickness 10hz tuning thickness 30hz tuning thickness 20hz tuning thickness 10hz tuning thickness 0.0002 100 5 0.0000 0 125 Temporal Thickness (ms) Temporal Thickness (ms)

  33. Outline • Introduction • Three Approaches • Examples • Pros and Cons

  34. Example • Using discrete frequency components to determine relative thickening/thinning.

  35. Simple Channel Cross-Section REFLECTIVITY travel time (ms) 0 SPECTRAL AMPLITUDE frequency (Hz) 250 Animating from low to high frequency, causes amplitude contours to move from thick to thin.

  36. Example • Using discrete frequency components to calibrate reservoir thickness.

  37. 8hz Spectral Amplitude Map Zone 1 WELL #1 1 mile Deep-Water Gulf of Mexico Partyka, Thomas, Turco and Hartmann, SEG 2000

  38. Thickness Modeling Well-Log Interpretation (Zone 1) Seismic Modeling (Zone 1) 0 1 0 50 amplitude 1 100 Two-Way Traveltime (ms) 0 shale -1 150 depth (feet) Temporal Wedge Model 200 0 6hz amplitude sand oil 10 8hz 1 20 30 Frequency (hz) 40 50 0 60 Spectral Signatures 70 0 20 40 60 80 100 Thickness (ft) Partyka, Thomas, Turco and Hartmann, SEG 2000

  39. Thickness Calibration 06hz Spectral Amplitude Modeled Spectral Signatures vs Thickness 0.008 Zone 1 1 8hz amplitude 8hz 0.007 6hz amplitude 0.006 0 6hz Amplitude 0.005 WELL #1 0.004 0.003 0 1 mile 10 08hz Spectral Amplitude Frequency (hz) 20 30 40 Zone 1 10 20 30 40 50 60 70 80 90 100 Thickness (ft) Thicknessfrom 6hz and 8hz energy WELL #1 Zone 1 1 mile WELL #1 0 50 1 mile Partyka, Thomas, Turco and Hartmann, SEG 2000 100

  40. Outline • Introduction • Three Approaches • Examples • Pros and Cons

  41. Conventional Thickness Estimation • Pros: • user and time intensiveness mandates careful QC. • Cons: • two attributes are required to quantify thickness: • peak-trough time-separation for thickness greater-than the tuning thickness, and • amplitude for thickness less-than the tuning thickness. • user and time intensiveness mandates careful QC.

  42. 1st Dominant Frequency and Amplitude • Pros: • collapses the Tuning Cubeinto two maps. • does not require careful seismic event picking when the zone of interest is relatively bright. • Cons: • as in the conventional approach, two attributes are required to quantify thickness: • 1st-dominant frequency for thickness greater-than the tuning thickness, and • 1st-dominant amplitude for thickness less-than the tuning thickness.

  43. Discrete Frequency Components • Pros: • can be used qualitatively to determine relative thickening/thinning. • can be used quantitatively to calibrate reservoir thickness. • usually exhibit substantially more fidelity than full-bandwidth, conventional amplitude/attributes. Can therefore selectively analyse frequencies exhibitting highest signal fidelity. • usually provide superior rock mass (stratigraphic and structural) and fault definition. • can be integrated with other appropriate information to yield a more comprehensive understanding of the reservoir. • does not require careful seismic event picking when the zone of interest is relatively bright.

  44. Discrete Frequency Components • Cons: • complexlayer distributions require seismic modeling analysis to determine relationship between spectral response and thickness.

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