Best Practice Flows > Velocity model workflow > Setting up the velocity model

The Markers + horizons method derives interval velocities from well-marker depths tied to time horizons, then interpolates spatially across the survey. Each marker-horizon tie defines a depth-time pair at a well location; the method converts these ties into layer velocities and fills the grid between wells via kriging or triangulation.

Required inputs

•Datum — elevation reference.

•Marker-to-horizon tie table — each row links one Time horizon to a Marker / Group picked on one or more wells. An optional Trend column (None / Vrms / Layer width / Data map) biases the velocity field between ties.

Parameters

•Max Depth — lower bound of the output cube (default 4000 m).

•Depth Step — vertical sampling of the output (default 10 m).

•Bottom Velocity — fallback velocity applied below the deepest tie (default 5000 m/s).

Workflow

1.Open Setting up the velocity model and select Markers + horizons.

2.Set Datum, Max Depth, Depth Step and Bottom Velocity.

3.Fill the tie table: for each time horizon pick the marker (or marker group) whose depth identifies it at the wells.

4.Optionally choose a trend per row to guide lateral interpolation (Vrms, layer thickness, or a data map).

5.Run the model. Velocities are computed per tie, then kriged/triangulated across the seismic trace grid.

Output

Interval velocity and average velocity cubes sampled on the seismic trace grid, plus depth and time maps at each time horizon. Velocity tracks the structure defined by the horizons while honouring the depth picks at wells.

When to use

•Projects with consistent marker picks across several wells and reasonably dense time horizons.

•Regional or exploration studies where checkshots are scarce but markers are plentiful.

•Models that must honour geological structure between wells.

If the output must align to a regular bin grid or seismic cube geometry, use Grid velocity by markers + horizons instead.