INT E-P1: Attribute Applications @ SEG 2017 3D curvature analysis of seismic waveform & its interpretational implications Haibin Di, Motaz Alfarraj, and Ghassan AlRegib Center for Energy & Geo Processing (CeGP) Georgia Institute of Technology {hdi7, motaz, alregib}@ece.gatech.edu September 25, 2017
Outline Motivation Waveform curvature vs. geometric curvature Three implications Application to horizon modeling Conclusions 2
Motivation Curvature analysis is useful for measuring the reflector geometry to depict the surface morphology and highlight the potential faults and fractures caused by anticlinal bending (e.g., Roberts, 2001); The reflector geometry is only partial information offered in a seismic cube, and the reflection waveform is also of significant importance for interpreting the seismic signals; What if applying the curvature analysis to the reflection waveforms? 3
Curvature kk 2DD (x, z) = zz 1 + zz 2 3 2 kk mmmmmm φφ 3DD xx, yy, zz = MAX(kk 3DD xx, yy, zz, φφ=[0o, 360 o )) kk mmiiii φφ 3DD xx, yy, zz = MIN(kk 3DD xx, yy, zz, φφ=[0o, 360 o )) where kk 3DD φφ xx, yy, zz = 1 1+AA 1 2 +AA 2 2 1 2 BB 1 +BB 2 tan 2 φφ+2bb 3 tttttttt 1+AA 1 2 + 1+AA 2 2 tttttt 2 φφ+2aa 1 AA 2 tttttttt 4
Waveform Curvature: 1D trace kk 2DD (z, w) = ww 1 + ww 2 3 2 where z: vertical coordinate w: waveform amplitude 2 nd -order derivative resolution enhancement 5
Waveform Curvature: 2D section Crossline No. Take inline section for example: Sample No. kk mmmmmm φφ 3333 xx, zz, ww = MAX(kk 3333 kk mmmmmm φφ 3333 xx, zz, ww = MIN(kk 3333 xx, zz, ww, φφ=[0o, 360 o )) (in blue) xx, zz, ww, φφ=[0o, 360 o )) (in red) where x: crossline coordinate z: vertical coordinate w: waveform amplitude 6
Waveform Curvature Table: Geometric curvature vs. waveform curvature Object Information for analysis Computation direction Implications Geometric curvature Waveform curvature Curvature analysis of seismic signals a. Structural depth/time b. Reflection amplitude Reflection waveform Horizontal Vertical (the xx-yy plane) (the xx-zz and/or yy-zz plane) Structure analysis: Waveform analysis: a. Fault detection a. Resolution enhancement b. Fracture characterization b. Dip estimation c. Reflector morphology c. Reflector decomposition delineation 7
Implication #1: Resolution enhancement a. Curvature: 2 nd -order derivative better resolution b. Maximum curvature: Normal to the reflection more reliable analysis Original amplitude section Maximum waveform curvature 8
Implication #2: Dip estimation Minimum curvature: Parallel to the reflection reflector dip More in my next presentation at 3:05 pm Orientation of Minimum waveform curvature Dip-guided horizon tracking 9
Implication #3: Reflector decomposition Peaks Troughs S-crossings Z-crossings 10
Application to horizon modeling Seismic image Peak decomposition Thinning Horizon model Seeded horizon tracking Seed picking and sorting 11
Limitations Sensitivity to high-frequency components Sensitivity to vertical window size Sensitivity to seismic noises 12
Limitation #1: Sensitivity to high-frequency components Take Ricker wavelet for example ww tt = AA 1 2ππ 2 ff MM 2 tt 2 ee ππ2 ff MM 2 tt 2 Original amplitude Waveform curvature: kk 0, ww = 6 AA ππ 2 ff MM 2 Linear to amplitude A quadratic to frequency f Maximum waveform curvature -15000 +15000-0.5 +0.5 13
Limitation #2: Sensitivity to vertical window size Window size = 3 Window size = 5 Z Window size = 7 Window size = 9 Window size no larger than half of the waveform period -0.5 +0.5 14
Limitation #3: Sensitivity to seismic noise From original seismic For resolution enhancement: use original amplitude For dip estimation : Apply smoothing first From smoothed seismic For horizon interpretation: Apply smoothing first -0.5 +0.5 15
Conclusions Curvature analysis is extended to seismic waveforms; Several implications: Resolution enhancement along the direction normal to seismic reflectors Dip estimation Reflector decomposition to peaks, troughs, and z/s-crossings; Potentials for horizon interpretation and modelling 16
More information (e.g., recent research, publications, tools, and codes) is available by: Visit our booth: #2109 Visit our center: http://www.ghassanalregib.com Visit my webpage: https://sites.google.com/site/dihaibin/ 17