taken from: alistair r. brown, aapg memoir 42, interpretation of three- dimensional seismic data,...

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

John N. Louie, Presenter

Tuning Phenomena in ReservoirsEffect of Tuning on Stratigraphic Interpretation



Understanding the Magnitude of Tuning Effects

Geol 755: Basin AnalysisGeol 755: Basin AnalysisGeophysics Week 6Geophysics Week 6

Geol 755: Basin AnalysisGeol 755: Basin AnalysisGeophysics Week 6Geophysics Week 6


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

QuickTime™ and a decompressor

are needed to see this picture.


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


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

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






Effect of Tuning on Stratigraphic Interpretation

The The limit of limit of visibilityvisibility depends on depends on thickness as thickness as well as well as impedance impedance contrast, and contrast, and noise levelnoise level




Deterministic Tuning Curves Have to Have to

differentiate differentiate tuning effects tuning effects from variations from variations in propertiesin properties (like porosity (like porosity and fluid and fluid content)content)

Tuning is a Tuning is a purelypurely geometricgeometric effect effect

The ideal tuning The ideal tuning thickness is thickness is /4/4




Deterministic Tuning Curves Sidelobes of wavelets also tune for thicker intervalsSidelobes of wavelets also tune for thicker intervals





Different wavelets will Different wavelets will tune to different degreestune to different degrees

May be multiple maxima May be multiple maxima on the tuning curveon the tuning curve QuickTime™ and a

decompressorare needed to see this picture.



Can Can cross-plotcross-plot amplitudes amplitudes from related from related locations to locations to examine examine correlationscorrelations

Linearity here Linearity here suggests suggests changes changes withinwithin reservoir, not reservoir, not outsideoutside





Reflection Reflection amplitude amplitude against against interpreted interpreted thicknessthickness






The The envelopeenvelope is is a statistical a statistical tuning curvetuning curve






The The envelopeenvelope here follows here follows a percentile a percentile of of amplitudesamplitudes






The The envelopeenvelope here is here is compared compared with a deter-with a deter-ministic ministic curvecurve




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.




Understanding the Magnitudeof Tuning Effects

““The first side lobe as a fraction of the center lobe of a The first side lobe as a fraction of the center lobe of a zero-phase wavelet is the reciprocal of the octave zero-phase wavelet is the reciprocal of the octave bandwidthbandwidth.”.”

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

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

Greater increases in amplitude must be explained Greater increases in amplitude must be explained otherwise.otherwise.

taken from: alistair r. brown, aapg memoir 42, interpretation of three- dimensional seismic data,...

Documents

reservoirs effect of

editions effect of tuning

presenter tuning phenomena

bed thickness

editions john

dimensional seismic

base reflections

aapg memoir