About domain conversion

Sometimes you may need to convert your data from the time domain to the depth domain, or vice versa. You can do this using the Velocity Model and Domain Conversion tools (in the Domain Conversion group of the prepare > Seismic strip). You can also use the Property Calculator, which contains functions that support domain conversion.

With the Velocity Model form you can create velocity models from two different input sets:

  • 2-way-time horizons (2D grids) define the boundary between layers in which the velocity profile is modeled according to a number of methods ranging from constant interval velocity to time-variant instantaneous, interval or average velocity profiles. All methods can be used with constant parameters or laterally varying, in order to describe the spatial variations of velocity in the subsurface.
  • 2-way-time horizons (2D grids) and well markers in depth are used as input to automated depth conversion set-up, based on apparent interval velocities at well locations.

You can find more details on velocity functions, vertical versus horizontal velocity variations, and well marker-driven methods in Velocity types – Methods of defining velocity profiles.

A number of useful features are available in the Velocity Model tool:

  • Functions describing the velocity behavior of layers can be referenced to any overlying time surface in the velocity model. While references to project datum (project zero) may be most commonly used, the velocity profile of layers is intimately related to the compaction state which again relates to maximum burial depth. In offshore locations, compaction starts at the seabed; in uplifted structures, compaction can relate to hypothetical reference surfaces of maximum burial periods. Velocity modeling in the application supports usage of such ‘compaction reference’ surfaces.
  • For deeper marine locations, water velocity profiles from global sets of measurements are built in the application via lookup tables. You can scale the water velocity profile in your project between minimum and maximum water velocity profiles, always staying consistent with global databases.

Although the application distinguishes between velocity model definitions (a set of time horizons and velocity parameters on the Velocity Model form, used to calculate the velocity model) and ‘calculated’ velocity models (created when clicking 'Apply' on the Velocity Model form and used to convert time domain objects to depth and vice versa on the Domain Conversion form) both of them are currently stored implicitly (project-specific).

The Domain Conversion tool supports polylines, tri-meshes, 2D grids, and seismic data, the last of these only for time to depth conversion.

In addition to velocity models, a number of uniform time-depth functions are also available for time to depth conversion.