8 - 2D Interpretation

Import Basic Horizons

To Save time we will now import our basic horizons for line 103 using (Horizon), (Import Horizons). Highlight line 103, Select the file name"horizons.asc" in the directory "asc", and (Preview) the file. We will read in four horizons. Three horizons are picked as a Peak and one as a trough. Note the different colors for the horizons.

Select the western third of line 103 with the icon. Use the left mouse button to start the selection and the right button to complete, press (Display Seismic). Ensure that the Scaled Display is 100,000, map window 800 to 2600 and a time scale of 5.0 inches per second.

Be sure to update the system parameters for the seismic display windows that will be created from now on. Slide the mouse over the horizons for identification and look at the amplitude values to determine what horizon is a peak or a trough. Here the peaks are blue, and the troughs are red. Notice the obvious reef build up between the Wabmun (orange) and Watt Mountain (Gold). Can you tell where the Leduc reef builds up into the Nisku? Note the overlying drape over the crest of this reef. Might there be some shallower potential?

Synthetic Well Ties

Now insert Well-F into line 103. Select sonic-gamma.template and display use (ctrl) left mouse button to match up the synthetic to the data.

Stretch Squeeze

Use the Stretch Squeeze option to tie the well and use the correlation

Click the left mouse button to connect peaks together from the seismic to the well tie and then press apply on the Correlation Mode window. Select the (TD Calibration mode) and verify that the drift is less than 10ms (we did not stretch squeeze very much).


Save this new time depth curve in the next step.


Update Time Depth Curve

Select Time-Depth, Define Active Time Depth Curve by clicking on the well from the base map. This will automatically select the well.

Select (Active), select TDPairs (our stretch squeeze) and save

Select (Dismiss), (Dismiss). Test the well tie by bringing up another seismic line through the well. The tops and deviation curve (if we have the data) should be in the correct position.


You will now see that the Total Depth of the Well and the tops will be displayed anytime a well is within the Section attribute display distance for a well.

Horizon Interpretion

Select (Horizon),(Pick Horizon), DNVG. This horizon turns to the color yellow (active)

Change the search gate to 15 and make sure the Stop at Joints is off Press the left mouse button to interpret in Auto to the right. The middle mouse button interprets in both directions and the right mouse button interprets to the right. Options exist to stop at line intersections and to stop at faults


Hot Keys

Hot Keys are located in the Quick Reference Guide in Appendices 4-4. Here are the ones I like to use for horizon interpretation.

Watch the options change on the Picking Options panel.

Map Ribbons

Select the Map Attribute icon, select the DNVG Active Horizon, Select the Horizon Ribbon Display and make the width 0.2 in, apply.

For a reasonable map color display, select Color, Adjust VD and Map Ribbon Color display, Load... rainbow.spl, Apply Here. If you are on a NT machine you are limited to only one color scheme. What I like to do is select seismic Display Attributes, Set the Trace Display Type to and the Scale Mode display to . Here is what our seismic line display looks like. Be sure to Update System Display Attributes so these changes will be reflected on all future windows.

Here is what our map ribbon looks like with the DNVG picked on all the 2D lines:

Complete the picking of the major horizons. If you are short of time, you can load the asc/horizons.asc file to use my interpretation. Let us examine check our amplitudes. Select the Map attribute button, and set the Active Horizon to and press apply. Notice that some of our lines are displaying the value zero. To extract all the amplitudes, select Horizon, Snap/Extract Amplitudes, select the DNVG horizon and all seismic lines, press the . The map should automatically be updated.

The DNVG pick should be uniform in amplitude. Verify and correct significant amplitude variations at the seismic line intersections. Notice the areas of low amplitude on lines 106 and 107. Are the picks correct?

Extract the amplitudes for the rest of the horizons and use them as a quality control tool.

Stratigraphic Amplitude Analyses

SeisX comes equipped with a basic set of analysis tools. They can be applied over an interval above and below a horizon or applied between two horizons. It is generally a good idea to test various statistics on a single line before you run the analyses on multiple lines or 3d surveys. Basic tools are:

Horizon Amplitudes

As an initial step we will display the amplitude values for a given horizon. Display the and set the Minimum and Maximum Ribbon values to user specified with the following values:


Display a color bar beside the map and examine the areas where the amplitudes are dim. Could this dimming be related to porosity development at the top of the Nordegg?

Display line 107 at a map scale of 1:50,000, time scale of 7.5 inches, VD/VA Wiggle, Excursion of 10 and wiggle Overlay Decimation of 10.

Load the default color scale (red-blue). This combined plot is useful for evaluating subtle, stratigraphic plays. Be sure to Update System Display attributes.

Measure Tool

Display line 103 through well-J. use the measure tool to measure the time interval from the Wabamun to the top of the "Possible Base of Porosity". I measure about 40 ms. The measure tool is also useful to measure map distance, azimuth or area.

Horizon Snap & Extract

We will now create a new horizon snapped to peak 45 ms below the WBMN. Select all lines and button to snap a new horizon 40 ms below the WBMN with search gate of 15 ms. This will bracket the porosity event. Our next step is to analyze this interval.


Press the Redraw Horizon only icon to see this newly created horizon.

Notice that SeisX does not have to re raster the seismic in the window when only the horizons are updated!

Select the Stratigraphic Amplitude Analysis tool. Extract the Average Absolute Value between the two Wabmun horizons.

Map this horizon aav and notice the high amplitude values updip from Well-J on line 103. Might this be a measure of Wabmun Porosity?

Markers -- Symbols

Markers are interpreted just like horizons. Create a marker called Amplitude, be sure to press enter! Press options and select the triangle symbol.

Highlight both sides of the bright amplitude just below the Nordegg event. This observed decrease in apmplitude may be due to porosity development near the normally tight Top of the Nordegg. Below is the section with the markers displayed.


Markers appear in both map view and section view. To get the markers to appear on the map, press the Map Attribute button, Select the marker with the Add Before button

Set the marker size to .2 inch and press apply.

If you zoom up the map you can see the markers you just created.


Note: click on any screen picture and you will have the full size image. Press (Alt) and the left arrow and you will return to the document.

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Copyright © Eric Keyser --Last Modified: July 2, 1999