How to display vertical thickness lithology using a Block Model: an Isopach Alternative – Origin & Beyond Quick Articles

Typically, when displaying the thickness of a rock unit in 2D, we use isopach contours. This works well in 2D and can take custom colours, but there is another way to show unit thickness that works in 3D. The method is simple and involves creation of a block model with a single row of tall blocks, then using trimming methods to limit the blocks to the desired unit.

In this example, we have a hypothetical lithology model based on surface and structural information.

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We want a way to display the vertical thickness of one of the orange "Cpi" unit in 3D.

First, we need to create a new Block Model that encompasses the XYZ extents of the "Cpi" unit. Using Block Model > Create Block Model and the Detailed Block Definitions > Edit Extents tool, we will carefully choose XY extents that cover the plan area of the data.

Gif 1 XY Extents.gif

Then, we switch the Vizex orientation to a vertical view so we can ensure the extents cover the vertical range of the data. Once we know the vertical range, we can select a block height that gives us a single row of very tall blocks.

Gif2 Z Extents.gif

This is an example of our end result, filtered to allow the data to peek through. We can clearly see the model contains very tall blocks.

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Now that our block model is prepped, we need to use the desired lithology unit to trim the blocks. This is done using the Stratigraphic > Seam Block Model > Intersect with Solid tool.

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We'll use a setup like the one below, where the Input file is our recently created block model, the Solid input is our lithology solid, and we choose to Trim and Modify input file:

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On the Trim tab, we choose to Trim to Solid. This is how we get the tall vertical blocks to accurately display the thickness of the rock unit.

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