Delta Model

Description Build a layered delta model from well curves and a velocity model.
Module(s) Image Gather Processing
Requirements 3D Survey, Window Model, Wells (optional)
Related Synthetics, Velocity Conversion, Velocity Model (From Wells)
Works with Velocity Volume

The Delta Model process builds a delta model from well curves. It requires a windowing model (see Creating a Windowing Model) and at least one well with a delta curve.

Use Synthetics in Insight to generate delta curves for your wells (see Displaying the Delta Curve). Valid delta curve results must be in the range from -0.25 to 0.35.

Window model layers are automatically divided by ghost horizons using the conformability specified in the windowing model. Delta values are selected for the model at the intersection between each well and the ghost layer. These  values are combined according to the specified per-layer settings.

Create a Delta Model process

Create a Delta Model process
  1. In the Control Panel, open the Process tab.
  2. At the tab header, click the Add icon and select New Process.
  3. Double-click Delta Model.
  4. Type a name for the process and click OK.

Define settings for delta model

Define settings for delta model
  1. Select the windowing model to be used in the process at Layer horizons - select a windowing model (see Creating a Windowing Model).
  2. In the Output Extents section, select a survey to be used in the delta modeling process at Survey.
  3. Type the range of Inline extent, Crossline extent and time/depth extent (TWT/TVDSS) for the delta model and the respective sample intervals.
  4. In the Wells section, click the Add Row icon to add the wells used in the delta modeling.
  5. Select the delta curve for each well to be used in the delta modeling. You can use Synthetics in Insight to generate the delta curve for your wells (see Displaying the Delta Curve).
    Delta values are required to be in the range of -0.25 to 0.35. See
    "Limiting the vertical extents" section below to include only valid intervals.

Limiting the vertical extent

Limiting the vertical extent

Enable Specify well curve vertical extents (ms) to set intervals to include in the calculation for each well. You can use this to avoid intervals where the calculated delta value is outside the valid range (-0.25 to 0.35).

Configuring per-layer settings

Configuring per-layer settings

In the Per-Layer Settings section, select the calculation type used to distribute delta in each layer in the windowing model. Available options include:

  • Inverse Distance — The resultant model will then tie each well.
  • Average of well values — Calculate delta values based on the average delta values at the wells for each layer within the window model. This generates a model that is constant along XY, for each Z value.
  • User-specified constant — Allows you to type a constant value for the delta model in that layer (this is useful to define sensible delta values outside of the well control depth range; either at depth and/or shallow in the model).

As a result of this process, a new delta volume is added in the Volume tab. You can further smooth the delta model using the Volume Smoothing process.

Tip: To quickly open the output volume, right-click the process item in the Process tab and click Open Child Volume. Vice versa, you can also open the process from the Volume tab directly. To do this, right-click the volume which was created from a process (indicated in italics) and click Open Parent Process.