1. Geol 755: Basin Analysis Geophysics Week 6
John N. Louie, Presenter
Tuning Phenomena in Reservoirs
Effect of Tuning on Stratigraphic Interpretation
Deterministic Tuning Curves
Statistical Tuning Curves
Understanding the Magnitude of Tuning Effects
Taken From: Alistair R. Brown, AAPG Memoir 42, Interpretation of Three-Dimensional Seismic Data, 4th & 6th Editions

2. Effect of Tuning on Stratigraphic Interpretation
When bed thickness ≥ , top and base reflections are separate.
When bed thickness < , reflections interfere and resonate- tuning
Taken From: Alistair R. Brown, AAPG Memoir 42, Interpretation of Three-Dimensional Seismic Data, 4th & 6th Editions

3. Effect of Tuning on Stratigraphic Interpretation
Where reflections merge, amplitude increases
Taken From: Alistair R. Brown, AAPG Memoir 42, Interpretation of Three-Dimensional Seismic Data, 4th & 6th Editions

4. Effect of Tuning on Stratigraphic Interpretation
In vertical and horizon section, amplitudes are highest where bed is thin- at the the tuning thickness.
Merged downdip reflections average the dip of the reservoir top & base.
Taken From: Alistair R. Brown, AAPG Memoir 42, Interpretation of Three-Dimensional Seismic Data, 4th & 6th Editions

5. Effect of Tuning on Stratigraphic Interpretation
The limit of visibility depends on thickness as well as impedance contrast, and noise level
Taken From: Alistair R. Brown, AAPG Memoir 42, Interpretation of Three-Dimensional Seismic Data, 4th & 6th Editions

6. Deterministic Tuning Curves
Have to differentiate tuning effects from variations in properties (like porosity and fluid content)
Tuning is a purely geometric effect
The ideal tuning thickness is /4
Taken From: Alistair R. Brown, AAPG Memoir 42, Interpretation of Three-Dimensional Seismic Data, 4th & 6th Editions

7. Deterministic Tuning Curves
Sidelobes of wavelets also tune for thicker intervals
Taken From: Alistair R. Brown, AAPG Memoir 42, Interpretation of Three-Dimensional Seismic Data, 4th & 6th Editions

8. Deterministic Tuning Curves
Different wavelets will tune to different degrees
May be multiple maxima on the tuning curve
Taken From: Alistair R. Brown, AAPG Memoir 42, Interpretation of Three-Dimensional Seismic Data, 4th & 6th Editions

9. Statistical Tuning Curves
Can cross-plot amplitudes from related locations to examine correlations
Linearity here suggests changes within reservoir, not outside
Taken From: Alistair R. Brown, AAPG Memoir 42, Interpretation of Three-Dimensional Seismic Data, 4th & 6th Editions

10. Statistical Tuning Curves
Reflection amplitude against interpreted thickness
Taken From: Alistair R. Brown, AAPG Memoir 42, Interpretation of Three-Dimensional Seismic Data, 4th & 6th Editions

11. Statistical Tuning Curves
Reflection amplitude against interpreted thickness
The envelope is a statistical tuning curve
Taken From: Alistair R. Brown, AAPG Memoir 42, Interpretation of Three-Dimensional Seismic Data, 4th & 6th Editions

12. Statistical Tuning Curves
Reflection amplitude against interpreted thickness
The envelope here follows a percentile of amplitudes
Taken From: Alistair R. Brown, AAPG Memoir 42, Interpretation of Three-Dimensional Seismic Data, 4th & 6th Editions

13. Statistical Tuning Curves
Reflection amplitude against interpreted thickness
The envelope here is compared with a deter-ministic curve
Taken From: Alistair R. Brown, AAPG Memoir 42, Interpretation of Three-Dimensional Seismic Data, 4th & 6th Editions

14. Understanding the Magnitude of Tuning Effects
Wavelet shape is critical to knowing where tuning is occurring.
Taken From: Alistair R. Brown, AAPG Memoir 42, Interpretation of Three-Dimensional Seismic Data, 4th & 6th Editions

15. Understanding the Magnitude of Tuning Effects
Wavelet shape is critical to knowing where tuning is occurring.
Taken From: Alistair R. Brown, AAPG Memoir 42, Interpretation of Three-Dimensional Seismic Data, 4th & 6th Editions

16. Understanding the Magnitude of Tuning Effects
“The first side lobe as a fraction of the center lobe of a zero-phase wavelet is the reciprocal of the octave bandwidth.”
Good seismic data has 2.5 octaves, for a side lobe level of 40% relative to the center.
This “40% rule” means that 40% is a common increase in amplitude at tuning for zero phase wavelets, reflected from the top and base of a reservoir layer.
Greater increases in amplitude must be explained otherwise.
Taken From: Alistair R. Brown, AAPG Memoir 42, Interpretation of Three-Dimensional Seismic Data, 4th & 6th Editions