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Creating stratigraphic model from grids

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I am trying to create a fairly simple stratigraphic model (4 units) from grids that represent the tops and bottoms of each of the 4 units (superface and subface). This is a basin with 3 basin-filling units, surrounded and underlain by a 4th unit representing older bedrock.

I am able to create the "eggcrate" stratigraphic fence from the grids and can create a solid model (see attached PDF of strat fences; 4_layer model_strat fences.pdf). However,when I try to use the grids to create a stratigraphic model, all of the bedrock uplands in the model are hidden (white, not transparent) and the basin-fill units are only partly visible. I give each of the basin-filling units a polygon extent within which the unit elevation is controlled by well data, outside the polygon the unit's elevation = land surface. So, in the areas of bedrock outcrop, all basin-filling units have their strat tops at land surface and thickness = zero, execpt bedrock which extends to model base. I have been careful to filter all grids using high stop/low pass such that grids stack normally without crossing. I am using cutoff values for my units that are 50 m, which is the size of my Z-cell size.

In the resultant strat model, when I turn the units on one-by-one, each unit is colored and gridded correctly inside of its unit extent, but outside of that where I have set the unit to land surface, the unit is colored white (not transparent as advertised in the help screen for "Manually Building 3D Stratigraphic Diagrams". See attached PDF of Strat model, 4_layer model_strat model.pdf, bedrock and one basin unit are shown; I did a screen capture while I was rotating the model so that the white grid outlines are visible (this is where the blue unit elevation is at land surface), otherwise the model is white outside blue unit.

I am wondering if I am doing something wrong or if this is a Rockworks problem

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Hi Don,

In this specific program (I'm assuming you are using the Grids|Grids -> Stratigraphy Model menu item), you have to list the units in the spreadsheet from lowest to highest, rather than highest to lowest (which is the reverse of what most poeple would probably do). Please check to see if this is causing the problem.



Alison Alcott

RockWare, Inc.

[email protected]

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Thank you -- yes of course that fixed it and was the problem. I even knew this little fact at one point in my life. And you folks have helpfully stated this on the instructions page for Grid / Grids -> Stratigraphic Model Program .... thanks again.

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