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**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

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**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

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**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

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**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

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**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

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**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

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**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

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**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

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**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

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**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

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**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

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**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

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**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

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**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

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**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

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**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

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