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<< Click to Display Table of Contents >> Navigation: Best Practice Flows > Velocity model workflow > Setting up the velocity model > Constant layered |
The Constant layered method builds a velocity cube composed of piecewise-constant layers. Each layer is bounded by a user-selected surface (horizon, time map, constant time, or topography) and carries its own interval velocity. Useful when the geology is naturally divided into zones with distinct, near-uniform velocities.
•Datum — elevation reference for the model.
•Layer table — one row per layer. Each row specifies the bottom of layer (a horizon, time map, constant time, or topography) and the velocity to apply inside that layer.
•Polygon (optional) — restricts the model to the area enclosed by the polygon.
All parameters of this method are defined through the layer table. No additional smoothing or interpolation options are exposed — the velocity stays strictly constant within each layer.
1.Open Setting up the velocity model and select Constant layered.
2.Set the Datum and, if needed, select a polygon to bound the model area.
3.Populate the layer table. Use Add Row to add a layer, choose its bottom surface from the project, and enter the interval velocity.
4.Repeat for every velocity zone from top to bottom of the section.
5.Run the model. The wizard creates depth, interval velocity, average velocity, and time maps per layer.
A layered velocity cube with interval velocity, average velocity, time and depth maps. Layer boundaries follow the selected surfaces exactly; velocity is discontinuous across boundaries and constant within each layer.
•Geologies with distinct velocity provinces separated by mapped horizons (for example salt/sediment, basalt/sediment).
•Quick time-to-depth conversion in layered basins when well control is sparse but structure is known.
•Initial model that will be refined later with checkshot- or marker-based methods.
Not suitable when velocity varies strongly inside a layer — use Checkshot extrapolation or a marker-based method instead.