Figure 1

Figure 2

From DGInsider, Q2 2000

With the upcoming release of EarthVision 6, you will be able to introduce domes, diapirs, and data for other types of intrusions and overturned geologic features directly into the WorkFlow Manager (Figure 1). Although this type of modeling is currently possible in the Geologic Structure Builder, the WorkFlow Manager will make the process of creating and editing these structures much easier. These geologic structures can be initially in the form of calculated 3D grids or, better still, scattered data points, where the points represent the rough shape of the dome or other structure you are going to model.

The WorkFlow Manager (Figure 2) provides an easy-to-use iterative work process allowing such structures to be quickly refined and updated. In the following example, we will create an initial salt dome model, examine the model for errors, correct the errors, then recalculate to produce the final result.

This process is very simple, and is performed entirely in the WorkFlow Manager. As always, the burden of bookkeeping for all of the underlying processes is taken care of by the WorkFlow Manager.

To generate our “first pass” model, we supply the ASCII scattered data representing the dome shape. The data are in the form X,Y,Z,P where P is the field or value to be gridded. Shown in Figure 3 are the scattered data for the salt dome displayed in the 3D Viewer. Points are queried by clicking on them (shown in white).

Structures like this dome are modeled by performing 3D minimum tension gridding on the scattered data representing the structure surface. The data are assigned a common value of “0” and a few control points with positive values (in this case, 100) are placed outside the space occupied by the dome. Alternatively, or in addition to the positive control, a few negative values (e.g., –10) could be placed “inside” the dome.

Figure 3

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Figure 7

If you were to examine the subsequently calculated grid node values for the dome, every node “outside” the dome surface would be positive and every node “inside” the dome would be negative. The dome shape is the 0 contour or “isosurface” in the rendering of the 3D minimum tension grid. After calculating the “first pass” of the 3D model, we select the 3D Viewer icon and turn off all structures except the dome (Figure 4).

Most parts of the dome have sufficient data to produce a geologically plausible surface. As we examine the model, however, we see a “saw tooth” effect in the upper part of the dome shape (Figure 5). This effect results from a lack of data to control the surface calculation in this area. We will attempt to correct the surface along this edge by quickly adding a few control points in the 3D Viewer and recalculating the model in the WorkFlow Manager. This process is analogous to fault validation, correction, and recalculation. The WorkFlow Manager makes these steps very simple to perform.

Using the 3D Viewer Edit Data menu, we set the 3D cursor to a point in the “saw tooth”

region, then click on the horizontal axes of the 3D cursor to a location where we want to “pull out” the salt surface (Figure 6). It can be helpful to look at the model from a couple of different angles to get this location where we want it.

When we are satisfied with the control point location, the new point is saved with a value of “0” (Figure 7). In this case, one or two more points along the “saw tooth” edge can be defined in a similar manner.

After saving the changes to the property data file and exiting the 3D Viewer, upon calculating the model, the WorkFlow Manager detects the change in the salt dome property data file and rebuilds the model based on those changes. The new, updated model is quickly calculated and can be examined in the 3D Viewer. Note the changes in the edited area (Figure 8). If the salt dome surface is not satisfactory, another iteration should be enough to provide satisfactory results.

In conclusion, the combination of the WorkFlow Manager and 3D Viewer will allow you to perform edits and recalculation of more structurally complicated models than before. Multiple iterations and model refinements provide the ability to test alternate interpretations and scenarios in previously difficult modeling situations.

Figure 8

 
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Last updated: March 22, 2007