Configuring Zones

A zone is a closed polygon with the physical dimensions of depth vs. offset between two correlated wells. The impedance characteristics of the zone depend on whether that zone intersects a well bore. If it does, the impedance characteristics are the interpolated velocity and density logs. If it doesn't, such as an inter-well channel, the impedance characteristics are a static (blocked) velocity and density value. The boundaries of zones are highlighted yellow when you hover the mouse over one in the main interface. The sub-zones are highlighted blue.

When GeoSyn is first launched you see a blank page. A minimum of one correlation, running from one side of the model to the other is required to create the minimum two zones necessary to create a valid model. A model can be comprised of any number of complete zones and sub-zones.

Within the zone (the polygon that runs the entire length of multiple correlated wells) are sub-zones, which exist between each well. While the boundaries of zones are highlighted yellow when the mouse is hovered over them, the boundaries of sub-zones are highlighted blue. The interpolation of zones and sub-zones can be configured separately. Sub-zones allow for more granular interpretation.

To configure zones:

1. After creating a correlation (for details, see Related Topics below), from the Edit menu, select Zones ()
OR
Right-click a zone and select either Zone Interpolation or Sub-zone Interpolation from the context menu.

The Edit Zone Parameters dialog box appears.

2. In the zone list, select the zone with which to work. As you select a number, the corresponding zone is highlighted on the depth page.

Overlapping zones can corrupt your GeoSyn model. A quick way to locate corrupt zones is to display the Edit Zone Parameters dialog box and select each zone number in the zone list (or click each zone on the depth page) to verify it is highlighted on both the depth page and in the zone list. Any zones that aren't highlighted can be deleted on the depth page.

3. For zones that intersect a well bore, select whether the zone impedance should be interpolated from the bottom of the zone upwards (to simulate offlap), from the top of the zone downwards (to simulate onlap), or by stretching and squeezing (to simulate compaction). Note that onlap and offlap are loosely applied stratigraphic definitions which won't hold true in situations where there are over-turned beds.

You can apply the same impedance characteristics to all zones in the model by clicking one of the buttons in the Set all pane.

4. Select whether to fill the zone with a specific lithology and whether to display that lithology on the depth page. To change the display color of any lithology throughout this and future models, click Edit to display the Edit Lithology dialog box.

5. Select whether arrows appear on the depth page indicating the direction of interpolation and whether to use interpolation algorithm 1 (recommended) or 2 (thinning zone with a large horizontal impedance gradient). Click Interpolation Method for a sample of how the two methods interpolate zones differently.