Seismic attributes are used to visualize data such that relevant information becomes easier to interpret. However, calculating many attributes leads to a data explosion and confusion: which view is best and how can I combine interesting attributes into one output representing the optimal view? We have introduced the term meta-attrbute for attributes that are combined in an intelligent way. In OpendTect you can create meta-attributes using math and logic (Mathematics attribute in OpendTect), neural networks (commercial plugin), and using the fingerprint attribute (OpendTect).
Purpose: To detect subtle hydrocarbon-related seismic anomalies and to pin-point Gas-Water, Gas-Oil and Oil-Water contacts. Theory: In a structure filled with hydrocarbons, seismic traces that lie on the same (depth) contour line will have similar hydrocarbon effects because these positions sample the same column lengths. Stacking of traces along contour lines will therefore stack up hydrocarbon effects while stratigraphic effects and noise are canceled. CCB (Common Contour Binning) produces two outputs: a CCB volume that consists of traces stacked along contour lines that are re-distributed along the same contour lines and a CCB stack. This is a 2D section with stacked traces flattened along the mapped reference horizon. The ideas behind CCB originate with Jan Gabe van der Weide and Andries Wever of Wintershall, who are the IP owners. Software: OpendTect + Common Contour Binning (CCB) plugin
Workflow:
Create a new polygon over the prospect by right clicking on Pickset. Close the Polygon and Save it (right-click). In general: restrict the polygon to one fault block per analysis.
Launch the CCB plugin by clicking on the CCB icon or selecting it from the Processing menu.
Specify the horizon, the seismic and the volume sub-selection (the polygon). The horizon inside the polygon area determines the Contour Z division (you probably don't want to change this). The step determines the contour bin-size (all traces within this contour interval are stacked). Optionally change the Z range (this is the vertical slice around the horizon that will be stacked. Press Go.
The traces inside the polygon are retrieved and sorted. A histogram is shown. For QC purposes you can display traces that will be stacked at each contour bin (single Z option). To produce the CCB stack (Normal or RMS) press GO. To produce the CCB volume toggle write output to on before pressing Go.
The CCB volume can now be used for further analysis. For example: display the amplitude at the horizon (add attribute and select CCB volume from stored data), or create new attributes from the CCB volume (energy, max, min amplitude) and display these on the horizon.
Tips:
To determine the spill point you can add a Timeslice element (preferably depth) and move this down over the displayed horizon map (with CCB amplitude display) until you see the contour line that determines the spill point. A spill-point coinciding with a step-change in amplitudes can be explained by a contact and supports the hydrocarbon fill hypothesis.
To avoid stacking in traces of bad quality and to ensure that you are not stacking over multiple fault blocks (which may have different fluid-fills and/or contacts) display the similarity attribute on the horizon. Use this display to guide the polygon picking.
