OpendTect dGB Plugins User Documentation version 3.2
Prev	Chapter 3. Sequence Stratigraphic Interpretation System	Next

3.3. Chrono Stratigraphy

3.3.1. Create Chrono Stratigraphy

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

SSIS Menu

Chronostratigraphy Creator:
First, select the horizons (minimal 2, top and bottom) that will be used to calculate the chronostratigraphy 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.

ChronoStratigraphy Creator

There are five models available to calculate the chronostratigraphy.

SSIS Models

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

Linear Interpolation: Linear interpolation can also be used for 3D Stratal Slicing or Proportional Slicing. If this model is selected, the user can specify the spacing between two chronostrat-horizons.
Parallel to upper: This model best depicts the lapout patterns for instance onlaps. In settings the user can specify vertical spacing between chronostrat-horizons.
Parallel to lower: This model relates to upward truncation patterns. In settings the user can specify vertical spacing between chronostrat-horizons.
Data driven: This model is driven from data based upon steering information. The chronostratigraphy will follow the dip and azimuth information.

Event Driven: This model drives the chronostratigraphy by following the events. If you press settings, you can select the (event) phases to use: Max/Min Only, Zero Crossing Only, or Max/Min and Zero Crossing. The tracked chronostratigraphy will be the combination of selected phases.

Note: In the setting options, Event/Data driven dialog has a "start at" option that relates the start position of creating chronostratigraphy. The start position of creating chronostratigraphy can be either 'Maximum Thickness' or "User Defined". Maximum thickness starts the chronostratigraphy where the sequence has maximum thickness between the mapped horizons. In the setting dialog of Data driven/Event driven, the user defined option can be used as a start position of SteeringCube to create chronostratigraphy.

The data driven model uses the SteeringCube to calculate the chronostratigraphy. 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 chronostratigraphy outwards from this point. Changing the starting position can drastically alter the chronostratigraphy.

Start position for the data-driven, dip-steered tracking approach

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.

Finally, an area sub selection can be made and the the Chrono Stratigraphy needs to be given a name. Then, the Chrono Stratigraphy is calculated in batch mode (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)

Chronostratigraphy Options: Right Click at the newly inserted chronostratigraphy, and select Options, a new dialog appears as shown below:

Chronostratigraphy Display Options window

In above window, you can change the line styles (fill/ single color display), spacing between chronostratigraphy, line width. Importantly, a slider (top of bottom) is also available to slide the chrono-horizons. For instance, if you have displayed thick chronolines and you want to see that how the layers are developed, you can move the slider within same window.

A chronoslider can also pop up from SSIS toobar

directly. It will allow to slide the chrono-horizons from top to bottom or vice versa. This is a key tool of SSIS in analyzing and identifying the stratigraphic surfaces.

Chronoslider

Prev	Home	Next
Data Preparation	Up	Wheeler Transform / Wheeler Scene