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Taken From: Alistair R. Brown, AAPG Memoir 42, Interpretation of Three-Dimensional Seismic Data, 4th & 6th Editions

John N. Louie, Presenter

Tuning Phenomena in ReservoirsEffect of Tuning on Stratigraphic Interpretation

Deterministic Tuning Curves Statistical Tuning Curves

Understanding the Magnitude of Tuning Effects

Geol 755: Basin AnalysisGeol 755: Basin AnalysisGeophysics Week 5Geophysics Week 5

Taken From: Alistair R. Brown, AAPG Memoir 42, Interpretation of Three-Dimensional Seismic Data, 4th & 6th Editions

Effect of Tuning on Stratigraphic Interpretation When bed thickness When bed thickness ≥≥ λλ, top and base reflections are separate., top and base reflections are separate. When bed thickness < When bed thickness < λλ, reflections interfere and resonate- , reflections interfere and resonate- tuningtuning

Taken From: Alistair R. Brown, AAPG Memoir 42, Interpretation of Three-Dimensional Seismic Data, 4th & 6th Editions

Effect of Tuning on Stratigraphic Interpretation Where reflections merge, amplitude increasesWhere reflections merge, amplitude increasesWhere reflections merge, amplitude increases

Taken From: Alistair R. Brown, AAPG Memoir 42, Interpretation of Three-Dimensional Seismic Data, 4th & 6th Editions

Effect of Tuning on Stratigraphic Interpretation In vertical andIn vertical and horizon section, amplitudes are highest where bed is thin- athorizon section, amplitudes are highest where bed is thin- at

the the tuning thickness.the the tuning thickness. Merged Merged downdip downdip reflections average the dip of the reservoir top & base.reflections average the dip of the reservoir top & base.

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Taken From: Alistair R. Brown, AAPG Memoir 42, Interpretation of Three-Dimensional Seismic Data, 4th & 6th Editions

Effect of Tuning on Stratigraphic Interpretation

The The limit oflimit ofvisibilityvisibilitydepends ondepends onthickness asthickness aswell aswell asimpedanceimpedancecontrast, andcontrast, andnoise levelnoise level

Taken From: Alistair R. Brown, AAPG Memoir 42, Interpretation of Three-Dimensional Seismic Data, 4th & 6th Editions

Deterministic Tuning Curves Have toHave to

differentiatedifferentiatetuning effectstuning effectsfrom variationsfrom variationsinin propertiesproperties(like porosity(like porosityand fluidand fluidcontent)content)

Tuning is aTuning is apurelypurelygeometricgeometric effecteffect

The ideal tuningThe ideal tuningthickness is thickness is λλ/4/4

Taken From: Alistair R. Brown, AAPG Memoir 42, Interpretation of Three-Dimensional Seismic Data, 4th & 6th Editions

Deterministic Tuning Curves Sidelobes Sidelobes of wavelets also tuneof wavelets also tune for thicker intervalsfor thicker intervals

Taken From: Alistair R. Brown, AAPG Memoir 42, Interpretation of Three-Dimensional Seismic Data, 4th & 6th Editions

Deterministic TuningCurves

Different wavelets willDifferent wavelets willtune to different degreestune to different degrees

May be multiple maximaMay be multiple maximaon the tuning curveon the tuning curve

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Taken From: Alistair R. Brown, AAPG Memoir 42, Interpretation of Three-Dimensional Seismic Data, 4th & 6th Editions

Statistical Tuning Curves

Can Can cross-plotcross-plotamplitudesamplitudesfrom relatedfrom relatedlocations tolocations toexamineexaminecorrelationscorrelations

Linearity hereLinearity heresuggestssuggestschangeschangeswithinwithinreservoir, notreservoir, notoutsideoutside

Taken From: Alistair R. Brown, AAPG Memoir 42, Interpretation of Three-Dimensional Seismic Data, 4th & 6th Editions

Statistical Tuning Curves

ReflectionReflectionamplitudeamplitudeagainstagainstinterpretedinterpretedthicknessthickness

Taken From: Alistair R. Brown, AAPG Memoir 42, Interpretation of Three-Dimensional Seismic Data, 4th & 6th Editions

Statistical Tuning Curves

ReflectionReflectionamplitudeamplitudeagainstagainstinterpretedinterpretedthicknessthickness

TheTheenvelopeenvelope is isa statisticala statisticaltuning curvetuning curve

Taken From: Alistair R. Brown, AAPG Memoir 42, Interpretation of Three-Dimensional Seismic Data, 4th & 6th Editions

Statistical Tuning Curves

ReflectionReflectionamplitudeamplitudeagainstagainstinterpretedinterpretedthicknessthickness

TheTheenvelopeenvelopehere followshere followsa percentilea percentileofofamplitudesamplitudes

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Taken From: Alistair R. Brown, AAPG Memoir 42, Interpretation of Three-Dimensional Seismic Data, 4th & 6th Editions

Statistical Tuning Curves

ReflectionReflectionamplitudeamplitudeagainstagainstinterpretedinterpretedthicknessthickness

TheTheenvelopeenvelopehere ishere iscomparedcomparedwith a with a deter-deter-ministicministiccurvecurve

Taken From: Alistair R. Brown, AAPG Memoir 42, Interpretation of Three-Dimensional Seismic Data, 4th & 6th Editions

Understanding the Magnitude of Tuning Effects Wavelet shape is critical to knowing where tuning is occurring.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

Understanding the Magnitude of Tuning Effects Wavelet shape is critical to knowing where tuning is occurring.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

Understanding the Magnitudeof Tuning Effects

““The first side lobe as a fraction of the center lobe of aThe first side lobe as a fraction of the center lobe of azero-phase wavelet is the reciprocal of the octavezero-phase wavelet is the reciprocal of the octavebandwidthbandwidth..””

Good seismic data has 2.5 octaves, for a side lobe level ofGood seismic data has 2.5 octaves, for a side lobe level of40% relative to the center.40% relative to the center.

This This ““40% rule40% rule”” means that 40% is a common increase in means that 40% is a common increase inamplitude at tuning for zero phase wavelets, reflected fromamplitude at tuning for zero phase wavelets, reflected fromthe top and base of a reservoir layer.the top and base of a reservoir layer.

Greater increases in amplitude must be explainedGreater increases in amplitude must be explainedotherwise.otherwise.