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This module reads a well sonic log file and converts the recorded interval transit times into an interval velocity profile, then writes the derived velocities into a depth-velocity gather at the traces closest to the well location. Use this module to populate or constrain a depth-velocity model with hard well data before or after tomographic updates.
The sonic log is provided as a plain text file containing two columns: measured depth (MD) and interval transit time (DT, in microseconds per foot). The module interpolates the DT values onto vertical depth using a user-supplied MD-to-VD conversion table, applies optional smoothing, and converts transit time to velocity in m/s. The resulting velocity column is written into a band of traces centred on the trace nearest to the well head position.
After execution, a velocity-vs-depth curve is displayed in the 2D depth image view, allowing immediate visual quality control of the imported well velocities against the surrounding velocity field.
The existing depth-velocity gather into which the well-derived velocities will be written. This gather defines the spatial and depth sampling grid used for the output. The gather axes are expected to be in the depth domain (vertical axis in metres).
A container grouping the horizontal coordinates of the well head. The module uses these coordinates to identify which trace in the input gather is closest to the well, and then populates that trace and its immediate neighbours with the derived velocity profile.
The easting (X) coordinate of the well head in the same coordinate system used by the seismic data, in metres. Default value: 0 m. Set this to match the actual well location so that the module selects the correct traces to update.
The northing (Y) coordinate of the well head in the same coordinate system used by the seismic data, in metres. Default value: 0 m. Use together with X to uniquely locate the well within the seismic survey grid.
A table of paired depth values used to convert measured depth (MD, along the wellbore) to true vertical depth (VD). Each row contains one MD value (in metres) and the corresponding VD value (in metres). This conversion is required for deviated or horizontal wells where the along-hole depth differs significantly from the vertical depth. For vertical wells, MD and VD are equal and the table can contain just two points (0, 0) and the total depth. This table must be populated before running the module; an empty table will prevent execution.
Path to the plain-text sonic log file. The file must contain two whitespace-separated columns: measured depth (in feet) and interval transit time DT (in microseconds per foot, µs/ft), one sample per line. This is commonly exported from petrophysical software or extracted from a LAS file. The module reads the file sequentially from top to bottom; no header lines are expected. Ensure the file covers the full depth range of interest, as velocities outside the log coverage will fall back to the V0 default value.
A constant depth offset, in metres, added to the starting depth of the well sonic log when mapping it onto the seismic depth axis. Default value: 0 m. Use a non-zero shift to compensate for a datum difference between the well reference elevation and the seismic processing datum. Positive values shift the log deeper; negative values shift it shallower.
The half-width of the zone, in number of traces, around the trace nearest to the well head into which the derived velocity column is written. Default value: 5 traces. For example, a value of 5 means that traces within ±5 traces of the nearest trace will all receive the well velocity. Increase this value to propagate the well constraint laterally across a wider region of the velocity model; decrease it to keep the well influence tightly localised.
The length of the running-average smoothing window, in number of DT log samples, applied to the interval transit time values before converting them to velocity. Default value: 20 samples. Sonic logs frequently contain high-frequency cycle-skipping spikes and thin-bed oscillations that are not resolvable at seismic scale. Smoothing suppresses these artefacts and produces a velocity profile that is more representative of the macro-velocity structure seen by seismic waves. Use larger values (e.g., 50–100) for noisy logs or when a smooth, blocky velocity model is desired; use smaller values to preserve more stratigraphic detail.
The fallback velocity, in m/s, assigned to depth samples where the sonic log provides no valid data (either because the DT value is zero or negative, or because the depth falls outside the range covered by the log file). Default value: 2000 m/s. Set this to the expected near-surface or water-column velocity appropriate for your survey. This value is used only where the log has gaps; it does not affect depth ranges that are covered by valid sonic measurements.