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The Shift Depth CIGs module applies a depth-domain correction to Common Image Gathers (CIGs). It reads a user-defined table that maps each depth level to a corresponding depth shift value, interpolates the shift at every sample position in the gather, and moves each sample by the interpolated amount. The correction is applied only to traces whose absolute offset falls within the specified offset range; all other traces are passed through unchanged.
Use this module to remove residual moveout from depth-migrated CIGs when the depth shift varies with depth but not significantly with offset — for example, to correct a systematic depth bias introduced by an inaccurate velocity model or datum shift. The shift table can also be inverted to undo a previously applied correction. Multi-threaded execution is supported for efficient processing of large 3D datasets.
The input seismic data stream providing the depth-migrated CIG gathers to be shifted. Each gather should be sorted by offset so that the offset-range filter works correctly. Connect the output of your depth migration or previous CIG processing step here.
The individual depth-domain CIG gather on which the depth shift is applied. The module reads each trace from this gather, checks its offset against the configured offset range, and applies the interpolated depth shift from the table to qualifying traces. Traces outside the offset range are copied to the output without modification.
The minimum absolute offset (in metres) of traces that will receive the depth shift correction. Traces with an absolute offset below this value are not shifted. Together with Offset to, this defines a window in offset space within which the correction is active. Set to 0 to start the correction from zero offset.
Default: 0 m.
The maximum absolute offset (in metres) of traces that will receive the depth shift correction. Traces with an absolute offset greater than this value are not shifted. Set this to the maximum useful offset in your CIG data, or to a value that limits the correction to near-offset traces if the shift is only reliable at short offsets.
Default: 650 m.
When enabled, all depth shift values from the table are negated before being applied. This allows you to reverse a previously applied correction without editing the shift table. Enable this option when you need to undo a shift that was applied in an earlier processing step and wish to reuse the same table.
Default: Disabled.
The collection of depth–shift pairs that define the correction curve. Add one row for each depth control point at which you have a known shift value. The module linearly interpolates between rows to compute the shift at every depth sample in the gather. At depths outside the range covered by the table, the shift from the nearest table endpoint is applied (flat extrapolation). You must define at least two rows for the interpolation to be meaningful.
The label for the row collection within the depth table. Each row entry contains a Depth value and a Shift value that together define one point on the depth-correction curve.
The depth position (in metres) of this control point in the shift table. Enter depths as positive values increasing downward, consistent with the depth axis of the input CIG gathers.
Default: 0 m.
The depth correction to apply at the corresponding Depth value, in metres. A positive shift moves events downward; a negative shift moves them upward. Determine these values from residual moveout analysis of the CIG gathers or from a comparison between the migrated depth image and well picks.
Default: 0 m.