3.3. Chrono Stratigraphy

3.3.1. Create Chrono Stratigraphy

In order to create the Chrono Stratigraphy click SSIS > Chrono Stratigraphy > New.

First select the horizons (minimal 2, top and bottom) that will be used to calculate the Chrono Stratigraphy by clicking 'Read horizons'. When the horizons are read, they are automatically placed in stratigraphic order and the sequence buildup is defined. Each sequence is defined by a top and bottom horizon. The calculations are stored in a temporary directory that can be selected by the user.

• Isochronous / Diachronous. Horizons are either Isochronous (time invariant) or Diachronous (time variant).

• Model. There are 4 models available to calculate the Chrono Stratigraphy. Three models are based on interpolation and one model is a data driven model:

Three models are based on interpolation and one model is a data driven approach:

• Linear interpolation

• Parallet to upper

• Parallet to lower

• Data driven

The data driven model uses the SteeringCube to calculate the Chrono Stratigraphy. The algorithm is described in the figure below. By clicking 'Settings', the SteeringCube can be selected or changed, and the start position can be set to either the maximum thickness between the horizons or by a user defined location (e.g. well). By default, the algorithm starts at the point of maximum sequence thickness and calculates the Chrono Stratigraphy outwards from this point. Changing the starting position can drastically alter the Chrono Stratigraphy.

The other options are related to the spacing between the top and bottom horizons. The user can specify the minimum spacing between horizons to stop the bottom horizon at this position and continue only with the top horizon. The maximum spacing allowed between horizons, without inserting a new chronostratigraphic tracked horizon, can be specified as well.

For each sequence there is only one model available. This depends on the isochronous/diachronous criteria assigned to the top and bottom of the sequence:

Finally, an area subselection can be made and the the Chrono Stratigraphy needs to be given a name. Then, the Chrono Stratigraphy is calculated in batchmode (see section 8.2 in the OpendTect User Documentation.)

3.3.2. Display Chrono Stratigraphy

When the Chrono Stratigraphy is calculated, it can be displayed on an element. Add an element to the tree, by right clicking on it and select Add Chronostratigraphy display. When this option is greyed out, select a Chrono Stratigraphy first (SSIS > Chrono Stratigraphy > Select)