|
<< Click to Display Table of Contents >> Navigation: FK > Foot print remove 3D |
Removing footprints from the 3D data set(s)
Footprints are most commonly observed in the 3D seismic volumes. There are various reason for the footprints in the data set. Footprints can be produced either by acquisition or during the seismic data processing. But majority of the footprints are related to Acquisition rather seismic processing. Presence of footprints on the time slices/depth slices or on the stack section masks the resolution that leads to poor interpretation.
So what causes this acquisition footprints?
There are 3 factors which need to be considered during the acquisition survey design. Offset, Fold and Azimuth. Based on the designing of the survey fold is already preset and we can achieve the desired fold but we don't have control on the Offset and Azimuth since we have logistical issues in the acquisition especially in the onshore. There might be a canal or a village where we can't lay our receiver spread which creates a void and we miss the Offset and Azimuth information here. The distribution of Offset and Azimuth can be uniform within the bins or it can be vary from one bin to another. It may be uniform in inline direction but not the same case in cross line direction. This results in footprints visible on the time/depth slices. The linear spatial gird pattern seen on the 3D seismic slices are nothing but footprints. In case of the marine data acquisition it might be due to the cable feathering. The other factor which we mentioned due to the seismic data processing but the chances of generating acquisition footprints by means of processing is very minimal. During the acquisition, if we acquired the data in sparse grid we may create some artifacts during the processing. In another scenario if we have a coarse grid then we have the problem of aliasing created by steeply dipping noise events which eventually results in footprints pattern.
The Foot Print Remove 3D module suppresses acquisition-related footprint noise in 3D seismic volumes using an FK (frequency-wavenumber) domain filtering approach. The algorithm works time-slice by time-slice: it transforms each time slice into the 2D FK domain, identifies and attenuates the low-wavenumber periodic energy characteristic of footprints, and transforms the result back to the spatial domain. Two independent depth zones (Time 1 and Time 2) allow the filter to adapt its footprint removal strength to the changing character of footprints with depth. An optional adaptive subtraction step provides additional control to prevent over-subtraction of geologically meaningful signal.
Use this module on post-stack 3D seismic volumes before interpretation when acquisition footprints are visible as regular linear or grid-like patterns on time slices or depth slices. The module includes an interactive preview panel that lets you inspect the original slice, the cleaned output slice, and the extracted footprint on a slice-by-slice basis before committing to full-volume processing.
The input data item that references the 3D seismic dataset to be processed. This must be a fully stacked 3D volume (post-stack data) organized as a regular inline/crossline grid.
The input gather containing the 3D seismic traces to process. The module reads the full volume from this gather, assembles it into a 3D cube, applies footprint removal time-slice by time-slice, and writes the result to the output gather. The input gather must represent the complete 3D volume for the FK spatial analysis to work correctly.
The time slice number to display in the interactive preview panel. Changing this value updates the preview windows showing the original slice (In), the filtered output slice (Out), the extracted footprint (Footprint), and the FK spectra. Use this parameter to navigate through the volume and visually verify that the filter is correctly identifying and removing the footprint pattern at representative depths before running the full-volume processing.
The length of the temporal analysis window (in seconds) used during the FK transform. The module processes the volume in overlapping vertical windows of this length, computing a separate FK spectrum for each window. Default: 0.02 s (20 ms). A shorter window provides better temporal resolution for footprint detection but may reduce the quality of the wavenumber estimation. A longer window improves wavenumber resolution but reduces the ability to track rapid vertical changes in the footprint character. For typical 3D datasets sampled at 2–4 ms, a value of 20–50 ms is recommended as a starting point.
This parameter group defines the footprint filter settings for the shallow zone of the volume, from the start of the data up to the Time 2 boundary. Footprint character often changes with depth because the acquisition sampling pattern interacts differently with the changing wavefield. Defining separate parameters for two depth zones lets you apply a stronger or weaker removal in each zone independently.
The reference time (in seconds) for the first parameter zone. Default: 0.00 s. The filter parameters defined in the Parameters for Time1 group apply from the top of the data through the transition to the Time 2 zone. Set this to the top of the interval where footprints are first visible, typically the beginning of the processed section.
The width of the taper zone (in wavenumber samples) applied to the footprint mute in the inline direction in the FK domain. Default: 10. A taper prevents abrupt edges in the FK mute function, which would otherwise introduce spatial ringing artefacts in the output. Larger values produce a smoother transition between the muted and preserved regions of the FK spectrum, which reduces ringing but also reduces the sharpness of the footprint suppression. Values between 5 and 20 are typical for most datasets.
The width of the taper zone (in wavenumber samples) applied to the footprint mute in the crossline direction in the FK domain. Default: 10. This parameter controls the smoothness of the FK mute boundary in the crossline dimension, analogous to Footprint Taper Inlines but acting perpendicular to it. Adjust this value independently of the inline taper when the survey geometry is asymmetric — for example, when inline and crossline bin spacings differ significantly, or when the footprint pattern is more pronounced in one direction than the other.
The spatial wavelength (in number of inline traces) that the filter will preserve in the inline direction. Default: 30 traces. Geologically meaningful reflectors have broad, coherent spatial wavelengths, while acquisition footprints tend to have shorter, periodic wavelengths tied to the shot or receiver line spacing. This parameter defines the boundary in the FK domain below which spatial energy is treated as geology and protected from removal, and above which it is considered footprint and suppressed. Increase this value if the footprint spacing in your survey corresponds to a short wavelength that might overlap with meaningful geology; decrease it if the footprint is at a long spatial wavelength to avoid preserving noise.
The spatial wavelength (in number of crossline traces) that the filter will preserve in the crossline direction. Default: 30 traces. This is the crossline counterpart of the Preserve wave length along Inlines parameter. In surveys with a different receiver line spacing from the shot line spacing, the footprint wavelengths in the inline and crossline directions will be different, and these two parameters should be set accordingly. Inspect the FK spectrum of representative time slices to identify the footprint wavenumber peaks and set the preserve wavelength just above those peaks.
This parameter group defines the footprint filter settings for the deeper zone of the volume, anchored at the Time 2 reference time. The filter smoothly interpolates the filter parameters between the Time 1 and Time 2 definitions, so you can taper the aggressiveness of the footprint removal with depth. This is particularly useful when footprints are strong in the shallow section but diminish at depth, or when the footprint wavelength changes because of structural velocity variations.
The reference time (in seconds) for the second parameter zone. Default: 1.00 s. The filter parameters defined in the Parameters for Time2 group are applied at this time and deeper. Set this to the time below which the footprint character changes noticeably — for example, where footprints weaken, change periodicity, or disappear. If the footprint character is consistent throughout the entire volume, set Time2 parameters identical to those in the Time1 group.
The width of the FK mute taper zone in the inline direction for the Time2 depth zone. Default: 10. Functions identically to the corresponding Time1 parameter but applies at the Time2 reference level and deeper. If footprints are weaker at depth, use a larger taper value here to produce a more gradual suppression.
The width of the FK mute taper zone in the crossline direction for the Time2 depth zone. Default: 10. Functions identically to the corresponding Time1 parameter but applies at the Time2 reference level and deeper. Adjust independently of the inline taper when crossline footprint character differs from the inline direction.
The inline spatial wavelength (in number of traces) preserved by the filter at the Time2 depth zone. Default: 30 traces. Functions identically to the corresponding Time1 parameter but controls the FK mute boundary at the Time2 reference level. If the footprint wavelength changes with depth due to migration or processing effects, set this value to match the deeper footprint period.
The crossline spatial wavelength (in number of traces) preserved by the filter at the Time2 depth zone. Default: 30 traces. Functions identically to the corresponding Time1 parameter but controls the crossline FK mute boundary at depth. Set this value to match the crossline periodicity of the footprint pattern in the deeper part of the volume.
When enabled, applies adaptive subtraction after the FK footprint estimate is computed. Instead of directly subtracting the full footprint model from the data, the adaptive subtraction step scales the footprint model locally so that it is subtracted only where and to the degree it is consistent with the noise in the input — helping to preserve signal where the footprint model may be inaccurate. Default: disabled (false). Enable this option when simple FK subtraction produces over-subtraction artefacts or when the amplitude of the footprint varies significantly across the survey area.
Controls the aggressiveness of the adaptive subtraction step. Valid range: 0.0 to 1.0. Default: 0.95. A value of 1.0 applies the full estimated footprint model (maximum subtraction); lower values reduce the subtraction strength to prevent over-removal of signal. This parameter is only active when Use Adaptive Subtraction is enabled. Start with the default of 0.95 and reduce gradually if you observe over-subtraction artefacts. Values below 0.5 typically provide insufficient footprint removal.