2. Selecting Data
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2. Selecting Data

SciQt integrates with various third party data repositories. This should be transparent to you and is dependent on how the software was launched. To use the Coloured Inversion application to design an operator it is first necessary to analyse the seismic and well data spectra. This is achieved by loading some seismic trace data and well log impedance data in time. Pop up the "Select Input Data" dialog by either clicking the Input Seismic and Well data... menu item under the Tools menu bar or by clicking the icon.

The table below shows both tabs of the Select Input Data dialog with an example of data selected for Coloured Inversion operator design. Seismic Coloured Inversion is data driven which means that the complete analysis and design of the operator (or as far as possible) is performed as soon as the data is selected/loaded or updated.

2.1. Input Seismic

With the "Select Input Data Dialog" displayed click the "Input Seismic" tab (default) to select the input seismic data to be used. The SciQt will connect with various data repositories depending on the environment in which the Coloured Inversion software is being run. It attempts to do this in such a manner that the Geoscientist need know only minimal information to be able to connect seamlessly with the seismic database. However, as data repositories from third party vendors use different techniques to store data, there will inevitably be some differences with the specific seismic selection mechanism.

Select Input Data Dialog (Input Seismic tab)List of steps to generate seismic trace spectra

  1. Selected Seismic

    This control displays the pre-selected 3D seismic data volume and is thus inactive.

    Note: if data was not pre-selected then the Selected Seismic label would be a Select Seismic... button allowing you to pop-up a seismic volume selector.

  2. 3D Survey Area

    Trace data for the spectral analysis can be selected from either the full 3D survey area or from a sub-area using the In-line/X-line Start and End input fields. By default the full area is selected.

  3. Load Seismic

    Clicking the Load Seismic button causes the random set of traces over the 3D Survey Area to be loaded for spectral analysis.

  4. Set Time Range

    The aim is to design a Coloured Inversion operator for the zone of interest (target). It is therefore desirable to time gate the selected traces prior to generating trace spectra. Ideally you should use a well defined interpreted horizon in the target zone to guide the seismic trace time gate. In this manner, the various gated traces should have sample values over a similar geology.

    Click Select Horizon... to pop up a horizon select dialog, then select horizon and then click Close button to return.

    Click Horizon in Range radio button and specify the Relative Start and Relative End values. A negative number is a relative time above the horizon (i.e. shallower) and positive number is a relative time below the horizon (i.e. deeper). The aim is to select a time gate trace which has a gate length within the range 500 - 1000 msec. The user supplied values here are accepted, with the chart area updating, when you either press the Return or Enter key, press the Tab to move to the next widget, or mouse click on a different widget.

    Note: If no horizon data is available and if seismic volume is relatively flat, then using an absolute sub range would be adequate. If it is not flat or the geology changes considerably over the 3D survey area then the selection of a smaller 3D Survey Area might be desirable.

2.2. Input Well Log

With the "Select Input Data" dialog displayed click the "Input Well Log" tab to select the well log data to use. The SciQt software supports reading acoustic impedance in time, from ASCII files or by connection to a well log data repository. Here we shall assume you will normally wish to obtain data from OpendTect well log data repository and we will describe this route. If you wish to load from ASCII files then please refer to the full User Manual.

Select Input Data Dialog (Input Well Log tab)List of steps to generate well log spectra

  1. Load Wells

    Clicking the Load Wells push button will auto select acoustic impedance log curves in the OpendTect data repository. It is assumed that acoustic impedance log will have the characters "AI" (upper or lower case) somewhere within the log curve name. If, for a given well, there are no such AI log curves or the log curve doesn't meet the assumed naming convention, then the user can still select or generate AI log curves manually. This is achieved by right clicking on the well name after first attempting to load the wells automatically. Note the Load Wells push button will change to a Reload Wells push button after the initial automatic selection.

    Right clicking will pop-up a menu with Select AI Log... and Generate AI Log... menu items. Selecting the first item will pop-up the "Select Database Logs" dialog which lists the available logs allowing you to choose an AI log curve however it's named. Selecting the second item will pop-up the "Generate AI Log" dialog which displays two lists. The left hand list allows you to select a sonic log with the right hand list allowing you to optionally select a density log. If no density is available, then you can select User for Density Source radio button and supplying a User Density Value. Here the AI log will be generated from the supplied sonic and density. In OpendTect log curves are stored in depth. SciQt requires the AI log curves to be in time.

    This transformation and resampling is done automatically for you using the Depth/Time model allocated for each well. This data in the time domain can be displayed on one or more Main Window charts. By default, the AI data (in time) is displayed on the "Log Input (time domain)" and "Log Input Detrend (time domain)" charts. As each AI log curve is loaded its amplitude spectra is also immediately calculated and displayed by default on the "Individual Wells" chart.

    The central area of the "Select Input Data" dialog (Input Well Log tab) to the right shows the available AI log curves for each well. You can deselect wells and/or log curves by clicking on the appropriate [tick box].

  2. Set Time Range

    Again our aim is to design a Coloured Inversion operator for the zone of interest (target). It is therefore desirable to time gate the selected traces prior to generating well log spectra. Ideally you should use a well defined interpreted horizon in the target zone to guide the well log trace time gate. In this manner, the various gated traces should have sample values over a similar geology.

    Click Select Horizon... to pop up a horizon select dialog, select horizon and then click Close button to return.

    Click Horizon in the Range radio button and specify the Relative Start and Relative End values. A negative number is a relative time above the horizon (i.e. shallower) and positive number is a relative time below the horizon (i.e. deeper). The aim is to select a time gate which has a gate length within the range 500 - 1000 msec. The user supplied values here are accepted, with the chart area updating, when you either press the Return or Enter key, press the Tab to move to the next widget, or mouse click on a different widget.

With the seismic and well data loaded, the SciQt application will complete all the various steps to generate a Coloured Inversion operator. However, with this data driven approach the initial derived Coloured Inversion operator may not be ideal. As such, it may be necessary for you to perturb some of the design parameters before saving the operator. Apart from controlling desired data and data ranges, all other design parameters are accessible via "Design Operator Dialog" (see section below) and the "Advanced Controls" dialog.

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1. Launching the SciQt OpendTect plug-in Home 3. Designing and Saving the Coloured Inversion Operator