Description

Engine - 3D ZO-MF Constrain (v2) runs the zero-offset multifocusing (MF) search across a 3D survey (or along an arbitrary 2D line), computing the optimal focusing parameters bin by bin and writing the results into an on-disk multifocusing storage database for later velocity analysis, imaging, or stacking. Supplying a picking file (or a connected picking object) lets the search be constrained to time corridors around expected reflectors, which is faster and more stable than a fully unconstrained search over every possible focusing parameter. You control exactly which bins are computed - a regularly stepped subgrid, or a sparser set of bins chosen to guarantee a minimum offset coverage - so you can trade calculation time against spatial detail. Use the module's "Update calculation area" command to preview on the map exactly which bins will be processed with the current settings before committing to the full run.

Input data

SEG-Y data handle

Link to the prestack SEG-Y seismic dataset that the engine reads traces from for every calculation bin.

Input trace headers (of seismic data)

Header index (source/receiver positions, offsets, and other geometry) for the same seismic dataset, used to determine which traces fall inside each bin's aperture.

Input Binning

The survey's binning grid (inline/crossline numbering, bin size, azimuth) used as the geometric reference for locating bins and their apertures, and for the "Selection by min offset" bin-selection mode.

GMFPickingItem

An existing 3D picking object (horizon time corridors), typically produced by an earlier picking or interpretation step, used together with (or instead of) the File with picking parameter to constrain the multifocusing search.

MF Tables Parametrization

The multifocusing parametrization tables that define the velocity, angle, and time sampling scheme used by the search engine. These are normally produced by an earlier MF table-building step and are required for the search to run.

FZFactorMatrix

A spatial correction map (F/Z factor) applied while extracting trace geometry for the multifocusing search, typically derived from near-surface or velocity information for the survey area.

V0 Map

A map of the near-surface reference velocity (V0) across the survey area, used as the starting/reference velocity for the multifocusing search at each bin.

Parameters

File with picking

Path to an existing picking/correlation file (.corr) that defines horizon time corridors used to guide (constrain) the multifocusing search at each bin. Supplying this file focuses the search near the expected reflector times, making the computation faster and more reliable than an unconstrained full search.

Default: none (optional).

3D

Storage file 3D

Path where the 3D multifocusing results database (.kdb) will be created or updated. Set this when calculating over a full 3D grid (defined by Output Binning below) and leave the 2D fields empty, since exactly one of the 3D or 2D storage targets must be used per run. If a database already exists at the given path with matching parameters, the engine resumes it and skips bins already calculated; if the existing file's parameters do not match, you are prompted whether to overwrite it.

Default: none. Required when running in 3D.

Output Binning

The bin grid (defined elsewhere in the project) that specifies the geometry - inline/crossline numbering, bin size, and orientation - of the 3D volume over which the MF search is run and stored. This determines the physical layout of the resulting multifocusing database.

Default: none. Required when running in 3D.

2D

Storage file 2D

Path where the 2D multifocusing results database (.kdb) will be created or updated. Use this instead of the 3D fields when running the calculation along an arbitrary line rather than a full 3D grid.

Default: none. Required when running in 2D.

Arbitrary line (2D)

The sequence of bin positions along an arbitrary line (rather than a regular 3D grid) over which the MF search is run when working in 2D mode.

Default: none. Required when running in 2D.

Storage Velocity analize

Each inLine

Controls how densely, along the inline direction, additional intermediate velocity-analysis data is stored alongside the main MF results (every Nth inline). Lower values store more detail for thorough interactive quality control of the focusing search but increase database size; higher values reduce storage and overhead.

Default: 5. Minimum: 1.

Each xLine

Same as Each inLine but controls the storage density of intermediate velocity-analysis data along the crossline direction (every Nth crossline).

Default: 5. Minimum: 1.

Calculation area

First inline number(-1 no limit)

Restricts the calculation to inlines at or after this number, letting you focus the run on a sub-area of the Output Binning grid (for example, to test settings on a small area first). Use -1 to start from the first inline of the grid with no restriction.

Default: -1 (no limit).

Last inline number(-1 no limit)

Restricts the calculation to inlines at or before this number. Use -1 for no restriction (calculate through the last inline of the grid).

Default: -1 (no limit).

First crossline number(-1 no limit)

Restricts the calculation to crosslines at or after this number. Use -1 for no restriction.

Default: -1 (no limit).

Last crossline number(-1 no limit)

Restricts the calculation to crosslines at or before this number. Use -1 for no restriction.

Default: -1 (no limit).

Selection type

Chooses how bins within the calculation area are selected for computation. "Constant grid" calculates on a regular subgrid defined by the Step along inLine/xLine settings and the Calculation rule. "Selection by min offset" instead picks a sparser, irregular set of bins chosen to guarantee a minimum source-receiver offset coverage (using Min offset calculation, Merge distance for min offset calculation, and Desired min distance), which can substantially cut the number of bins to compute in areas of dense fold.

Default: "Constant grid".

Min offset calculation

Minimum source-receiver offset that a bin must be able to supply for it to anchor the sparse bin selection. Only used when Selection type is "Selection by min offset".

Default: 100000.

Merge distance for min offset calculation

Distance within which nearby candidate bins from the min-offset selection are merged into a single calculation point, avoiding redundant, closely spaced calculations. Only used with "Selection by min offset".

Default: 0. Minimum: 0.

Desired min distance

Target minimum spacing between the sparse set of bins chosen by the min-offset selection, used to keep the selected calculation points reasonably evenly distributed across the area. Only used with "Selection by min offset".

Default: 1000. Minimum: 0.

Calculation rule

When Selection type is "Constant grid", determines how the inline and crossline step settings combine to pick bins. "Logical AND" calculates only bins that fall on both an inline step and a crossline step, giving a sparser, regularly spaced subgrid. "Logical OR" calculates bins that fall on either step, giving a denser pattern.

Default: "Logical AND".

Step along inLine number

Calculates every Nth inline within the selected range when Selection type is "Constant grid". Set to 1 to compute every inline; increase it to thin out the calculation for a quicker preview or a coarser output grid.

Default: 1. Minimum: 1.

Step along xLine number

Calculates every Nth crossline within the selected range when Selection type is "Constant grid". Same behavior as Step along inLine number, applied to crosslines.

Default: 1. Minimum: 1.

First Time

Start of the time window, within each bin's data, over which the multifocusing search is performed. Raise this value to skip searching the shallow part of the record if it is not of interest.

Default: 0 ms. Minimum: 0.

Last Time

End of the time window over which the multifocusing search is performed. Set this to cover the full time range of interest for your target reflectors; a shorter window reduces computation time but produces no results below this time.

Default: 6000 ms (6 s).

Sparse factor

Read-only value reported after a run using "Selection by min offset": indicates how much sparser the selected bin set is compared to a full grid, giving a measure of the calculation savings achieved. It is computed automatically and is not user-editable.

Number of calculation bins

Read-only value reported after a run using "Selection by min offset": the actual number of bins that were selected for calculation. It is computed automatically and is not user-editable.

GPU alter loop

Advanced option affecting the GPU-accelerated calculation path of this engine. Leave it unchecked for normal operation; only enable it if advised, for example to work around a GPU calculation issue on a particular hardware or driver configuration.

Default: off (unchecked).

References

Gelchinsky, B., Berkovitch, A. and Keydar, S., 1999, Multifocusing homeomorphic imaging - Part 1: Basic concepts and formulas: Journal of Applied Geophysics, 42, 229-242.