"DIAGNOSTIC 3-D SEISMIC PROCESS”
D3DSP* DATA PROCESSING GUIDE
L. Willhoit 4/12/2002 * Patent #5,671,136
GOM EXAMPLE DESCRIPTION (To be modified, as needed):
1. INITIAL PRE-PROCESSING
Processing begins with Field Recorded Seismic Data tapes. The data usually has no geometry assigned
to the trace headers. Data traces will be converted to 2ms sample interval, using an “intelligent” sample
interpolating algorithm. Obviously bad traces should be identified and deleted here.
2. COMPENSATION FOR INSTRUMENT IMPULSE RESPONSE & GEOMETRIC SPREADING
To remove the effects of the recording instrument an inverse filter will be constructed to convert the
instrument response to a zero-lag spike. This filter will be applied through convolution with the seismic
data. As a correction for spherical divergence, a time-variant geometric spreading scale function will be
applied to the entire volume. Shot records will be displayed before and after application of the
geometric-spreading function for QC purposes.
3. TIME VARYING (TIME-DOMAIN) SPECTRAL BALANCING (TVSB)
Time-varying spectral balancing will be applied to the volume to whiten the spectrum in the (GOM)
6-125 Hz. frequency range. Minimum-phase bandpass filters are recommended for spectral
decomposition. Shot records and amplitude spectra will be displayed pre- and post-TVSB.
4. TOMOGRAPHIC / REFRACTION STATICS
Apply if available. Not available (or required?) in many offshore areas.
5. SURFACE-CONSISTENT DECONVOLUTION
Usually a three-step process involving spectral analysis, surface-consistent frequency decomposition, and
operator design/application. The data may be scaled with a 500 ms AGC gain to balance amplitudes
prior to spectral analysis. The AGC gain is not applied to the actual data to which the decon operators
are to be applied. Multiple hyperbolic windows may be used for spectral analysis, having varying time
extents at zero offset.
The prediction distance will be one sample long. The operator length is to be determined from test
Autocorrelograms using lengths of 40, 64, 128, and 256 ms, with 0.1% white noise. The spectra will be
decomposed into source and detector terms prior to operator design and application.
6. AMPLITUDE ANOMALY PROCESSING (AAP)
Attenuates anomalous amplitudes in a surface consistent manner. RMS amplitudes can be measured over
500 ms. windows of all data. Amplitude statistics can be decomposed into source, detector, offset and
CMP terms. The decomposed amplitudes can then be compared to the RMS amplitudes of the individual
traces and anomalous amplitudes on each trace can be attenuated. Amplitude analysis should be
performed on a swath-by-swath basis, but amplitude decomposition should be run on all data
7. SURFACE-CONSISTENT AMPLITUDE COMPENSATION
Need to produce surface-consistent shot and detector multipliers for the entire survey, analogous to
Residual Static corrections.
8. RESIDUAL AMPLITUDE COMPENSATION (OFFSET ONLY)
An offset-consistent scaling routine will be used, which compensates for the higher amplitudes
associated with the near-offset traces. Time-variant amplitude analysis should be performed on a subset
of shots from the entire survey. These shots will have Amplitude Anomaly Processing and Surface
D3DSP Processing Guide Page 2 of 3 4/11/2002
Consistent Amplitude Compensation applied, as well as the time-variant filter used in SCAC picking.
This scaling routine should separate the amplitude statistics into offset groupings (roughly twice the
receiver spacing) and derive a set of time-variant offset-dependent multipliers for each group. These
scalars should then be applied to the Anomaly/SC Amplitude corrected, unfiltered volume according to
the offset of each trace.
9. AMPLITUDE ANOMALY PROCESSING (CMP ONLY)
A final pass of AAP (Par. 6), above, should be run decomposing the CMP term only. With shot,
detector and offset balancing complete, any remaining amplitude anomalies should reside in the CMP
domain. The same windowing parameters used in the earlier AAP run will be incorporated in this pass.
10. PRELIMINARY VELOCITY ANALYSIS
Velocity analyses will be derived at roughly a 5000' interval in the inline direction and a 4000' interval in
the crossline direction. At each location along an inline, five-to-seven CMP's will be summed for the
velocity spectra. Multi-velocity function stacks and gathers will also be used as velocity interpretation
tools. Velocity picking will be performed in an interactive velocity processing system, in which the
velocity picks are used to interactively NMO-correct the associated CMP gather. By doing this, the
accuracy of the moveout correction can be seen immediately. The picks will also be overlaid on the
corresponding multi-function stack, so that the stack response can be observed. Preliminary velocity
analysis should be performed on deconvolved data with the refraction or tomographic refraction solution
(if any) applied. The data input to velocity analysis can also be filtered with a 10-45 Hz, zero-phase
filter, and scaled with an RMS gain.
11. REFLECTION RESIDUAL STATICS (1ST PASS)
A static-time-correction routine is required that resolves observed reflection times into surface-consistent
residual source and detector static corrections. Using a Gauss-Seidel-type method, a least-squares error
solution for the reflection statics problem should be abtained. For the first pass, static time deviations
should be picked against a stacked model dataset in a “good data” window, with a reasonable (24ms?)
time shift limit. The data input to picking should be nmo-corrected decon data with the tomographic
statics (if any) applied. The decomposed solution will be derived from picks from the entire recorded
volume over the restricted “good data” time window.
12. RESIDUAL REFLECTION STATICS VELOCITY ANALYSIS
With tomographic (or refraction) statics and residual reflection statics applied, velocity analyses should
be derived from the deconvolved data at roughly a half-mile interval in the inline direction and a quarter-
mile interval in the crossline direction, utilizing the same interactive QC tools used in the picking of
preliminary velocities. Filter tests may be performed on the data input to velocity analysis to determine
the bandpass filter that produces the highest resolution semblances for velocity picking. That filter, along
with an RMS gain, should be applied to the input data, but NOT used on the final stacked volume.
13. REFLECTION RESIDUAL STATICS (2ND PASS)
With tomographic (or refraction) statics, 1st-pass reflection statics and post-statics velocities applied, a
second pass of reflection statics should be performed. For 2nd-pass statics, time deviations will be picked
against a stacked model in the same “good data” time window, with a reasonable (24ms?) shift limit. For
pick decomposition, the near Shot-Receiver (e.g., 8000’ for targets below 8000’ depth) data should be
used. Both the input data and the model should be RMS gained, but neither should be bandpass filtered.
14. COMMON MIDPOINT FINAL STACK
With all statics and normal moveout applied, the CMP Amplitude Adjusted volume in Step (9) should
be stacked using client-approved outside mute parameters. An example follows:
D3DSP Processing Guide Page 3 of 3 4/11/2002
700’ 70 ms
15. POST-STACK TIME MIGRATION
Migrate with a suitable one-pass 3D time migration program, or apply a cascaded series of migrations
using a minimum function for the one-pass migration and residual laterally varying velocities for two
passes (Inline and Crossline) of time-domain migration, and again balance the wavelet's spectrum. Using
Time-Depth or Time-Velocity information provided by the client, a 3-D migration velocity T’ube should
be created, from which, a single minimum velocity function can be extracted which can be used in the
one-pass time-domain migration. The full, laterally varying, migration velocity field and the minimum
velocity function can then be used to generate the residual velocity field. Using this client-approved
velocity T’ube, 2-D finite-difference residual migration may be run on the one-pass-migrated data, in the
inline direction. This volume can then be sorted into the crossline direction, and a second pass of finite-
difference migration should be performed.
16. D3D-REFLECTIVITY VOLUME - (2nd PASS TVSB)
A second pass of time-varying spectral balancing will be applied post-migration. The amplitude
spectrum should be whitened using the same partameters as in Step (3), above. Zero-phase bandpass
filters are recommended for spectral decomposition. This is referred to as the D3D-reflectivity Volume.
17. D3D-IMPEDANCE VOLUME (RUNNING-SUM-INTEGRATION or INVERSION)
A final impedance volume should be generated through trace integration of the D3D-migrated TVSB
data. This trace-by-trace operation is a simple running sum (accumulation) of samples down a tracel,
and is to be followed by a (~3 Hz?) low-cut filter to remove any DC component that might be generated
by the first few (high amplitude?) samples on each trace. A filter test panel is recommended
to allow the client to select the low-cut parameters. This (or the next step) is called the D3D-impedance
18. PHASE ROTATION
At the client's request, for polarity convention purposes, both the reflectivity and the impedance volumes
may be phase shifted 180-degrees prior to output and delivery.
19. DELIVERABLES (Inline & Crossline Numbering Consistant with Original-processed Data)
SEG-Y - 8mm cartridge of Final, Unfiltered (D3D-Migrated) Reflectivity Volume
SEG-Y - 8mm cartridge of Final, Low-cut Filtered (D3D-Migrated) Impedance Volume
SEG-Y – NMO- and Static-corrected, Unmuted, Prestack CMP Gather Traces
SEG-Y - Final, Unfiltered D3D-Stack (Relative Amplitude)
ASCII - 3D Stacking Velocity Field
ASCII - 3D Time-Depth Field (client supplied)
ASCII - 3D Total Shot and Receiver Statics Field
Paper - Contoured Stacking Velocity Cross-sections and Time Slices, at sparsely selected intervals.
Paper - Final, Fully-corrected CMP Gather Plots (ev 5th CMP on ev 20th Inline, at 2 IPS & 40 TPI)
Paper and Electronic (MS Word) - Processing Report
* Diagnostic 3D Seismic Process – Patent # 5,671,136, issued 9/27/97,
Licensed to EPL (NOLA) by VTV, Inc. (Denver, CO)