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Seismic Seismic Reflecti Reflecti on on Record Record Reflection t 2 (x) = t 2 (0) + x 2 / v 2 rms

Seismic Refleksi

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  • Seismic Reflection RecordReflection t2(x) = t2(0) + x2 / v2rms

  • Land Seismic Flow Data Proc.Field TapeDemultiplexingTrue Amplitude RecoveryMutingEditingDeconvolution before StackPre-ProcessingDigital FilteringStatic CorrectionGather

  • Land Seismic Flow Data Proc.Velocity AnalysisDynamic CorrectionCDP StackingResidual Static CorrectionDeconvolution After StackMigrationProcessingPost ProcessingTime Variant ScalingDynamic EqualizationDisplay Seismic Section

  • Processing SequenceGeometry definition??????Where are the shotsand receivers located ?The most important values for data processing and relative OFFSETS!

    These may be Source - Receiver offsets, Receiver - Receiver offsets etc

  • Processing SequenceGeometry definitionWhat if the surface elevation changes ?i.e. remove the difference in travel time caused byshots and receivers being atdifferent elevations - change our time-zero ref. point to simulate the re-positioningof shots and receiversStatic corrections

  • Processing SequenceGeometry definitionWheres all the source energy gone ?Static correctionsAmplitude recoveryGeometric spreading, absorption etc

  • Processing SequenceGeometry definitionStatic correctionsAmplitude recoveryVelocity filtering- K-filter? Bandpass filter?May leave until stacking process!What about random noise?

  • Processing SequenceGeometry definitionStatic correctionsAmplitude recoveryVelocity filteringDeconvolutionCompensate for the filtering effects of the earth etc

  • Processing SequenceGeometry definitionStatic correctionsAmplitude recoveryVelocity filteringDeconvolutionCMP gatherSome processes must be carried out in the CMP domain

    Multiple Coverage Acquisition techniques

  • Processing SequenceGeometry definitionStatic correctionsAmplitude recoveryVelocity filteringDeconvolutionCMP gatherNMO correction

  • Processing SequenceGeometry definitionStatic correctionsAmplitude recoveryVelocity filteringDeconvolutionCMP gatherNMO correctionDMO Correction

  • Processing SequenceGeometry definitionStatic correctionsAmplitude recoveryVelocity filteringDeconvolutionCMP gatherNMO correctionCMP stackDMO Correction

  • Processing SequenceGeometry definitionStatic correctionsAmplitude recoveryVelocity filteringDeconvolutionCMP gatherNMO correctionCMP stackMigrationDMO Correction

  • What things needed ?Characteristic Seismic Event

    Geological Concept

  • Characteristic Seismic EventCoherency

    Amplitude Standout

    Seismic Shape

    NMO

  • Seismic EventPrimary EventNon-Primary

    Whats That ?

  • Non-Primary EventMultipleDiffraction Ghostetc

    *Q: what if we have no co-ordinates? Can we process without? What is most important parameter? A: regular inline geometry yes relative distances (offsets)*Need datum or static corrections to reduce the effects of the near surface.

    Have the elevation correction (long wavelength) to compensate for variations in ground level plus short wavelength weathering changes which will be shot-to-shot.We correct to a flat (arbitrary ) datum. The time shifts relate to distances and vels of weathering layer *Q: what causes this? A: sph. div. , absorption Apply data independent scalingManipulate amplitudes as little as possible. Prefer true amplitude*Q: What types of velocity filter are there?A: F-K, Tau-p, etc

    Random noise also presentQ: How do we get rid of?A: BP filtering (possibly), stacking etc*Q: relationship between frequency and attenuation?A: High frequencies attenuated faster

    Q: What is decon?A: An inverse of filtering process*Q: what is a cmp?A: a collection of traces from the same sub-surface point with different source-receiver offset values (preferably)Q: Why cmp domain?A: NMO, stack, remove some structural influences from the gather*NMO corrects for arrival time differences due to source-receiver offset variationsAttempts to correct to zero-offset case*Do these zero-offset traces represent the true mid-point? No!

    When reflectors are dipping, mid point for all offsets is no longer a single point. They are scattered. DMO correction is needed.

    *Produces a zero-offset traceIt results in S/N improvement*Do these zero-offset sections represent the true structure? No! Mid-points are displayed immediately below a source/receiver pair which is not where they should be in the presence of dipping events.