How to apply SSIS on 2D Seismic G. de Bruin

Sequence stratigraphic interpretations The sequence stratigraphic analysis comprises of 3 steps: Setup and data preparation Calculate the chronostratigraphy Interpretation Required Software: OpendTect Base v3.1.4, SSIS plugin, dip-steering plugin

Workflow Setup project I & Load Seismic Data II Filtered Seismic Data 3 Create SteeringCube1 Create SteeringCube Filter SteeringCube2 (Optional) Track bounding surfaces III Create SteeringCube 1 Filter SteeringCube 2 (Optional) Calculate Chronostratigraphy 5 Filter SteeringCube (Optional) /rel/html/dgb/index.html /rel/html/index.html Consult dGB User Documentation 1: Chapter : Chapter : Chapter 5.2 5: Chapter 3.3 Consult OpendTect User Documentation I: Chapter 3.1 II: Chapter III: Chapter 3.2 Sequence stratigraphic analysis

Please consult the user documentation on how to setup a survey and to load seismic data Setup and data preparation

Select a key line & calculate a SteeringCube. Processing > Steering > Create (BG-fast steering with a median filter is recommended) Setup and data preparation

Apply dip-steered median filter to the seismic data Processing > Attributes… Setup and data preparation Dip steered median filtered original Filtered Note: 2D seismic requires a larger step-out than 3D seismic. Test step-out for optimal results Chapter 5.3

Create a seismic output of your dip- steered median filtered seismic Processing > Create seismic output Calculate a steering cube for the Filtered Data-set (Processing > Steering > Create : Dip steered median filtered seismic FFT standard or Event-steering are recommended) Setup and data preparation

Track bounding surfaces (unconformities) Start with two horizons For unconformities use “Draw between seeds” Chapter 3.2 (tracked horizons)

There are 2 modes to calculate the chronostratigraphy Calculate the Chronostratigraphy *Requires: dip-steering plugin Model Driven: in-between each pair of horizons the chronostratigraphy is calculated based on models Data driven: in-between each pair of horizons the chronostratigraphy is auto- tracked by making use of a SteeringCube*

Calculate the Chronostratigraphy Click on SSIS > Chrono stratigraphy > New Select your key line Read horizons Assign diachronous or isochronous to horizons Select the SteeringCube or sampling rate Give a name to the chronostratigraphy Isochronous Linear interpolation IsochronousDiachronousParallel to upper DiachronousIsochronousParallel to lower Diachronous Data-driven Top Base Mode

Display the Chronostratigraphy 1) Select the Chronostratigraphy (SSIS > Chrono stratigraphy > select) 2) Right click on the line in tree> add chronostratigraphy display Display Chronostratigraphy Add Chronostratigraphy Display (tree) (Chronostratigraphy display) Chapter 3.3

Evaluate Chronostratigraphy Use the Chronostratigraphy-slider to QC result (right click Chronostratigraphy in the tree > options) (Chronostratigraphy-slider)

Improve Chronostratigraphy To improve chronostratigraphy: Improve SteeringCube: –Test Event Steering, FFT Standard or BG-Fast algorithms and vary parameters (see next 2 slides) –Test median filtering the steering cube (see next 2 slides) –Test dip-steered median filtering the seismic before calculating chrono-stratigraphy –Iterate if necessary (SC -> filter SC -> filter seismic -> new SC etc.) Add or improve bounding surfaces Model-driven chronostratigraphy: –Use model driven Chronostratigraphy for noisy sections

Improve Chronostratigraphy Chronostratigraphy too erratic Improve SteeringCube > Larger step-out > Apply (more) Median filtering

Improve Chronostratigraphy Chronostratigraphy too smooth Improve SteeringCube > Smaller step-out > Less Median filtering

Interpretation Add a Wheeler Scene SSIS> Add Wheeler Scene Add the 2D line in the Wheeler scene Tree scene 2 Display Seismic data

Interpretation Make a Systems tracts interpretation SSIS >interpretations > new

Interpretation Assign a systems tract Sub-divide into systems tracts –Highlight the interval –Click Insert –Provide a geotime / index –Provide a name TIP: Use the chronostratigraphy slider to get the exact geotime values

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