1. SEISMIC INTERPRETATION
JIM KELLOGG
UNIVERSITY OF SOUTH CAROLINA

2. Instructor http://www.AndeanGeophysical.com
Dr. James Kellogg has 30 years experience in regional tectonics, satellite geodesy, structural modeling, and potential field studies. He is a Professor in the Department of Earth and Ocean Sciences and Director of the Andean Geophysical Laboratory, at the University of South Carolina, President of Kellogg International Associates, and Editor-In-Chief of the Journal of South American Earth Sciences. He obtained his M.A. (1978) and Ph.D. (1981) in geology and geophysics at Princeton University. In 1987 he joined the faculty of the University of South Carolina as professor of applied geophysics. He has coordinated regional geophysical basin studies for petroleum exploration using seismic, well, gravity, and magnetic data. He has published over 60 papers and taught short courses in volume balanced structural and seismic reflection interpretation, potential field modeling, 3-Dimensional modeling, and regional tectonics.

3. SEISMIC INTERPRETATION
Seismic Data Acquisition and Processing
Pitfalls
Volume Balanced Solutions and Kink Method of Seismic Interpretation
Extensional Tectonics
Salt Tectonics
Seismic Attributes for Reservoir Characterization
3D Seismic Data

4. SEISMIC DATA ACQUISITION AND PROCESSING

5. SEISMIC DATA ACQUISITION AND PROCESSING
Acquisition – Shot, Wavelet, Trace
Acoustic Impedence, Polarity
Acoustic Well Logging
Synthetic Seismic Traces
Common Depth Point (CDP) Stack
Processing and Migration

6. DATA ACQUISITION Shot – initial bang Shotpoint – geographical location
Source pulse or wavelet – resulting sound
Reflections – echoes
Trace – stream of reflections recorded by geophone

8. SEISMIC ACQUISITION

9. SEISMIC ACQUISITION

10. Land Seismic Data Acquisition Transition Zone Arctic Highlands Jungle
Heliportable
Specialists
Desert

12. Geophone Team

13. Marine Seismic Acquisition

14. Marine Seismic Acquisition

15. Ocean-Bottom Cables
For some applications, it is desirable to put the receivers directly on the seafloor using ocean-bottom cables (OBC). The acquisition of shear wave seismic data is one such use. Shear waves do not travel through water, and so conventional marine sources do not generate them and hydrophones will not record them.

16. DATA ACQUISITION
Seismic reflector or acoustic-impedence boundary – boundary across which the hardness changes.
Reflection coefficient – type and size of acoustic impedence change.

17. DATA ACQUISITION
Seismic reflector or acoustic-impedence boundary – boundary across which the hardness changes.
Reflection coefficient – type and size of acoustic impedence change.
Acoustic impedence (Z) = density (r) x velocity (V)
Z = r V

18. TRACE ANALYSIS
Positive reflection – overlying layer is softer than underlying layer
Negative – upper layer is harder
Polarity – peak or trough for positive reflection

19. TRACE ANALYSIS
Positive reflection – overlying layer is softer than underlying layer
Negative – upper layer is harder
Polarity – peak or trough for positive reflection

20. TRACE ANALYSIS Two-way time – time from bang to recording
Amplitude – reflection strength
Wavelet shape

21. REFLECTION COEFFICIENT LOG AND NORMAL POLARITY WAVELET

22. Acoustic Well Logging Operation
The main instrument used is called the sonde.
A basic sonde consists of a source and two receivers one-foot apart.
The sonde is lowered down the borehole and waves are generated and recorded continuously.
The sonde is usually positioned in the borehole center using centralizing springs.
Frequencies used are in the range of kHz.
Typical investigation radius is 0.2 – 1.2 m.

23. Acoustic Well Logging Sonde types

24. Acoustic Well Logging Transit time

25. Acoustic Well Logging Example

26. Note high resolution of sonic log vs the seismic trace

27. Synthetic Seismic Trace
Reflection coefficients and velocity log used with a zero phase wavelet to produce a synthetic seismic trace

28. Wavelet
minimum phase wavelet = front loaded energy i.e. at time zero minimum energy and elsewhere maximum.
zero phase wavelet has maximum energy at time zero.
Most seismic sources do not generate a zero phase pulse, because that implies output before time zero. For instance an air gun source generates a minimum phase pulse. We can use minimum phase wavelet for acquisition and during processing convert to zero phase.

29. EFFECT OF WAVELET FREQUENCY ON SEISMIC RESPONSE

30. Which display do you prefer?

31. Are the faults clearer in this display?

32. Or in this display?

33. CDP RECORDING METHOD TO INCREASE SIGNAL TO NOISE RATIO
Common-depth-point (CDP) or Common-mid-point (CMP) – reflections recorded from the same subsurface point with different offsets.
Fold – number of traces
2 fold – 2 traces
96 fold – 96 traces

34. SEISMIC ACQUISITION

35. CDP-CMP METHOD

36. SEISMIC ACQUISITION

37. MIGRATION
Migrated – restore dipping reflector to correct subsurface position.