data conditioning and reprocessing
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Data Conditioning
and Reprocessing
Sometimes it isnecessary to consider
reprocessing of the
seismic dataset in
order to improve thesignal-to noise ratio.
Sometimes a complete
new reshoot of a
whole 3D survey can
be a valid option.
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Processing parametersshould be chosen in sucha way that they optimisethe end results. For thispurpose first the rawand processed CDPgathers are compared.The mute function canbe changed, whichmeans that the CDPgather is only usedbetween a certain offsetand time range.
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Vector filtering is an option when multi-
component data is involved in full wave
acquisition and processing. It uses vertical andradial trace pairs.
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Fourier and Radon Transform
Shot-generated noise and multiples are oftendrastically suppressed by FK filtering. This techniquedoes incorporate a Fourier Transform that brings the datawith the normal T X reference axis into the FK domain.
Amplitude and phase spectra describe the datacharacteristics in the FK domain.
The sine waveform for a frequencyfx is described by:
Sine function =Axcos ( 2fxt- x)
Ax = maximum amplitude of fx function,
x= phase.
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F-K Filter
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Sometimes it is handy to apply a Radon
transform to bring the data to the TauP
domain. The Tau stands for intercept time and P
for the slowness parameter of the ray. In the
TauP domain sometimes the noise can be
removed more easily.
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Dip Move Out
A Dip-corrected Move Out or DMO step is
useful in areas with rather steep dips.
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Deconvolution
Wavelet deconvolution is often done to focus (orsharpen) the seismic data and it change minimum-phase data into a zero-phase response. This
deconvolution step tends to shorten seismicresponse from a reflector and tries to re-positionthe maximum energy of the wavelet on thevelocity/density interface.
1. Wiener or Least Squares Filter
2. Predictive Deconvolution
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Enhancement in the
Seismic ReflectionTechniques
Seismic interpretation
has improved a lot
during the last
decade. It is illustrated
by the shapes of the
contours on various
depth maps from thesame investigation
area in time
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The use of micro-electronic mechanicalsystem sensors
(MEMS) help toimprove thesensitivity, thedynamic range andreduce the noise.Imaging software and3D visualisation (e.g.GoCadTM andVoxelgeoTM) providesa better feel for themapped surfaces.
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Ray tracing and map migration (e.g.
PetrocaemTM and GeomigTM) results in more
reliable depth contour maps. Depth migration
(e.g. GeovistaTM) puts depth maps directly at
the interpreters disposal. It uses a better
defined velocity model of the subsurface andalso allows the processing algorithms to work
more efficiently. Geostatistical methods (e.g.
SigmaviewTM) allow to quantify uncertainties inthe interpretational method.
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Important new techniques are 3Dvisualisation and classification of seismic
attributes. VoxelgeoTM and ER MapperTMprovides sophisticated methods to do 3D pixeldisplays of seismic data. SRCattributeTM lets theinterpreter calculate loads of seismic attributes.Many of these attributes are not verycomplementary to the conventional ones; butthey provide a new view on the same data. They
are sometimes difficult to interpret and theiradditional value to the prospect evaluationefforts is rather subjective.
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1. Teknik Fuzzy Logic
2. Multi Attribute Mapping
3. Time-Lapse Seismic Data
4. Multi Component Acquisition and Processing
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