Seismic sequence stratigraphic interpretation contains two primary goals: (1) unraveling the depositional environment and (2) predicting potential stratigraphic traps. The OpendTect SSIS plugin offers unique interpretation capabilities in this domain. In SSIS all possible horizons are tracked (data-driven mode) or modeled (interpolated between mapped horizons, or shifted parallel to upper or lower bounding surface). Each horizon is a chrono-stratigraphic event that can be used to reconstruct the depositional history (chrono-strat slider), to flatten seismic data and attributes (Wheeler transform), and to interpret system tracts (relating units to the relative sea level curve).
Purpose: Track or model all possible horizons within a given interval. Theory: Map the major bounding surfaces (horizons) in a conventional way (minimum is two horizons: top and bottom). Specify per interval how SSIS should create chrono-stratigaphic horizons (data-driven or model-driven). In data-driven mode the seismic events are followed. This mode requires a Steering cube (dip- azimuth information at every sample position computed with the Dip-Steering plugin). In model-driven mode, you can choose to interpolate between horizons (a.k.a. stratal slicing, or proportional slicing), or shift parallel to the upper horizon (emulating onlap situations), or shifting parallel to the lower horizon (emulating unconformable settings). All modes work for 2D and 3D seismic data. In practice, the data-driven mode is used for 2D (or on 2D sections from a 3D cube) while the model-driven mode is used for 3D seismic data. Software: OpendTect + Dip-Steering + SSIS
Workflow:
Use Data Preparation to prepare the horizons: horizons cannot cross and they should be continuous.
For the data-driven mode ensure that you have a Steering Cube (Processing - Steering). Filter the steering cube if you observe that the tracked chrono-stratigraphic horizons do not follow the seismic events correctly (Data Preparation - Filter Steering Cube).
Create a New Chrono-stratigraphy. Read the horizons and specify per interval and per horizon whether the horizon is isochronous (parallel layering) or diachronous (on- / off-lapping settings). For data-driven mode (both horizons are diachronous) select the steering cube and the minimum spacing (when to stop) and maximum spacing (when to insert a new chrono-stratigrahic horizon).
Proceed to calculate the chrono-stratigraphy. When the batch processing is finished: Select the chrono-stratigraphy.
Display the chrono-stratigraphy (right-click on the element in the tree).
To study the depositional history use the chrono-strat slider (right-click on chrono-stratigraphy) and add / remove geologic time from the sequence.
Add a Wheeler scene and use the chrono-stratigraphy to flatten the seismic (or attribute).
Tips:
To highlight unconformities with 2D (data-driven) chrono-stratigraphy use the Fill between lines option (Options menu) and play with colors.
To improve results add more horizons (map unconformities)
