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<< Click to Display Table of Contents >> Navigation: Migration > PSTM imaging selector 3D (velocity) |
The PSTM imaging selector 3D (velocity) is an interactive velocity analysis tool for 3D pre-stack time migration. It reads a pre-computed migration database produced by the Velocity Selector 3D - Kirchhoff PreSTM Engine and displays stacked and semblance panels for inline and crossline directions, allowing the interpreter to pick an optimum RMS velocity model interactively.
The module shows migrated stacks computed at multiple velocity percentages of a reference RMS model. By selecting the velocity percentage that produces the flattest common image gathers or the best-focused stacked image, the interpreter builds a corrected migration velocity field. Picked horizons, mute functions, and velocity corrections can be saved and reloaded between sessions. The final velocity output is written as a full-cube GSD file for use in subsequent depth migration or residual velocity analysis.
Path to the migration database (.kdb) file created by the Velocity Selector 3D - Kirchhoff PreSTM Engine module. This file stores the migrated image gathers at multiple velocity percentages and is required before the selector can display any data.
Link to an optional mute picking item. When connected, the defined mute is applied to the common image gathers before computing semblance and stacks, suppressing noisy near- or far-offset zones.
Link to a vertical velocity picking item used to store and transfer the picked RMS velocity corrections (delta VRMS) relative to the base model. This item holds the time-velocity picks made interactively in the vertical semblance panel.
Link to a corridor picking item that constrains the velocity picking range in the semblance panel. The corridor defines a permitted velocity band around the current pick, preventing the autopicker from wandering into noise zones.
Path to the output GSD file where the final picked RMS velocity volume will be written. This file can then be connected to a Kirchhoff PreSTM migration module to produce the final migrated image.
Selects which velocity percentage (relative to the reference model) is currently displayed in the stacked image panels. Corresponds to one of the velocity factor values used when the migration database was computed.
Selects the angle gather class currently shown in the display. Use this to inspect specific angle ranges when the database contains angle-domain common image gathers.
Selects the offset class currently shown in the display when the database contains offset-domain common image gathers.
Time window (in seconds) used when converting horizontal velocity picks (made on the horizontal semblance panel) to vertical velocity picks. Default: 0.2 s.
Lateral search distance (m) used when converting horizontal velocity picks to vertical velocity picks. Default: 100 m.
When enabled, the module spatially interpolates the picked horizon surfaces to fill gaps between picked locations. Disable this option to use the raw picked points only.
Datum elevation (m) to which the displayed stacks are shifted for visualization. Setting this to the survey datum helps align the displayed image with the correct depth reference. Default: 0 m.
Index of the currently active horizon layer for interactive picking. Set this to select which horizon layer receives new picks when clicking in the display.
Container group holding all velocity analysis parameters that control the semblance computation and the automatic velocity picking algorithm.
Minimum RMS velocity (m/s) displayed in the vertical semblance panel. Default: 1000 m/s. Set this to the minimum expected RMS velocity in your survey area.
Maximum RMS velocity (m/s) displayed in the vertical semblance panel. Default: 10000 m/s. Set this to the maximum expected RMS velocity in your survey area.
Velocity increment (m/s) between adjacent velocity traces in the semblance panel. Default: 100 m/s. Smaller steps give finer velocity resolution but produce a wider semblance display.
Time interval (s) between successive auto-picked velocity points. Default: 0.1 s. A smaller step produces denser picks that track rapid velocity variation; a larger step gives a smoother velocity function.
Spatial step (number of bins) between bins where auto-picking is applied when running auto-pick on the full cube. Default: 20 bins. Larger values speed up the auto-pick but produce a coarser spatial sampling of the velocity field.
When enabled, the automatic picker is restricted to searching within a velocity corridor (defined by the Corridor width on click parameter) centred on the most recently picked velocity value. This prevents the autopicker from jumping to spurious semblance maxima far from the expected velocity trend.
Half-width of the velocity corridor (m/s) used for constrained auto-picking. Default: 500 m/s. The picker will only consider semblance peaks within this velocity range on either side of the current pick. Increase for rapidly varying velocities.
When enabled, the auto-picked velocity function is smoothed with a running-average filter of length defined by Smooth window for auto picking before the picks are accepted.
Time half-window (s) for the smoothing filter applied to auto-picked velocities. Default: 0.05 s. A longer window produces a smoother velocity function at the cost of some vertical resolution.
Container group with parameters for extracting the base RMS velocity model into the picking item at regular spatial intervals.
Spatial step (bins) between extracted base velocity picks when populating the picking item from the base model. Default: 50 bins.
When enabled, picks are placed only at the turning points (local extrema) of the base velocity function rather than at every time step. This produces a compact set of control points that represents the velocity trend efficiently.
Time interval (s) between successive extraction points when populating the picking item from the base model. Default: 0.3 s.
Container group with parameters that control how the semblance is computed from the common image gathers.
Time window (s) over which the semblance coherence measure is computed at each sample. Default: 0.020 s (20 ms). A longer window improves the signal-to-noise ratio of the semblance but reduces time resolution for picking thin beds.
When enabled, the envelope (Hilbert transform) of the common image gather is used instead of the raw trace amplitude when computing the semblance. This makes the semblance less sensitive to polarity and phase variations across gathers.
When enabled, an automatic gain control (AGC) is applied to the common image gathers before semblance computation. This balances amplitude variations with time, improving the visibility of deep semblance peaks that would otherwise be dominated by shallow strong reflectors.
Time window (ms) for the AGC applied to the CIG before semblance computation. Active only when Use AGC For CIG is enabled. Shorter windows give more aggressive amplitude equalization.
Time window (s) around each horizon pick used when computing the horizontal semblance along a picked event. Wider windows average more samples around the horizon, improving stability at the cost of vertical resolution.
When enabled, the horizontal semblance values are normalized so that the maximum value equals one. This makes the horizontal semblance easier to interpret visually when comparing results across different areas.
Number of traces in the lateral aperture used for horizontal semblance computation. Larger values improve lateral coherence detection but may smooth over laterally varying velocity features.
When enabled, each gather trace is weighted by a power of its offset before semblance computation. This increases sensitivity to far-offset amplitudes, which are most affected by velocity errors and therefore carry the most diagnostic information.
Exponent applied to the offset weighting when Use weighted semblance For CIG is active. Higher values give progressively more weight to the far offsets. A value of zero gives equal weight to all offsets.
Container group for mute parameters applied to the common image gathers.
When enabled, the mute defined in the Mute picking item input is applied to the common image gathers before semblance and stack computation.
Time taper (s) applied along the mute boundary to avoid sharp amplitude transitions. The amplitude is gradually tapered from zero to full value over this time window on the live-data side of the mute.
When enabled, the portions of the displayed inline and crossline stacks that lie outside the calculated data area (zero-amplitude wings at survey edges) are removed. This provides a cleaner image for velocity picking near survey boundaries.
Container group with parameters that define the format and coordinate system of an ASCII file from which horizon picks can be imported.
Path to the ASCII horizon file to import. The file must follow the format specified by the other parameters in the Import horizons from ASCII params group.
Reference datum (m) applied when interpreting the time or depth values in the imported ASCII horizon file.
Specifies the time unit used in the imported ASCII horizon file (milliseconds or seconds).
Container group with parameters for generating angle-domain common image gathers from the migrated data.
Lateral smoothing taper (bins) applied along the inline direction when building angle gathers.
Lateral smoothing taper (bins) applied along the crossline direction when building angle gathers.
Minimum reflection angle (degrees) included in the angle gather output.
Maximum reflection angle (degrees) included in the angle gather output.
Angular increment (degrees) between successive angle gather traces.
Container group for parameters controlling the spatial interpolation of the picked velocity map.
Output grid spacing (bins) along the inline direction for the interpolated velocity map.
Output grid spacing (bins) along the crossline direction for the interpolated velocity map.
Container group for display navigation controls including the currently selected inline, crossline, and bin.
Controls how the cursor snaps to data positions when clicking in the display. Bin snaps the cursor to the nearest bin centre. Crosses snaps to the intersection of inline and crossline lines.
Recomputes all displayed inline and crossline stacks using the current mute definition. Run this action after modifying the mute picking to refresh the stack display.
Recomputes the semblance panel for the currently selected bin using the current mute definition. Run this after changing the mute to see the updated semblance before picking.
Saves all currently picked horizon layers to a binary file for later reuse.
Loads horizon layers previously saved in binary format.
Deletes all currently picked horizon layers from the session. This action cannot be undone.
Removes the current mute picking from the session.
Saves the current mute picking to the connected mute picking item for use in subsequent processing steps.
Loads a previously saved mute picking from the connected mute picking item.
Removes all vertical RMS velocity picks from the session.
Saves the current vertical RMS velocity picks to the connected velocity picking item.
Loads vertical RMS velocity picks from the connected velocity picking item.
Runs the automatic velocity picker on the currently selected bin only, using the semblance of the current bin. Keyboard shortcut: Alt+Down.
Runs the automatic velocity picker on all bins in the survey volume at the spatial step defined by Auto picking trace step. Keyboard shortcut: Alt+Shift+Down.
Prepares the picked velocity and horizon data for use as input parameters in a subsequent NIP (Normal Incidence Point) tomography update. This action reformats the current picks into the parameter structure expected by the NIP tomography module.
Removes the current corridor eta (velocity corridor) picks from the session.
Saves the current corridor eta picks to the connected corridor picking item.
Loads corridor eta picks from the connected corridor picking item.