Can I create a solid model of only one layer

[chris]

Hello

How can I create a 3D model or profile, section, fence diagram of only one formation.

I would like to make a model of porosity distribution within only one layer without displaying formations that lie above it. Is it possible to have also the surface of formation top within the same model. If possible how can I do that?

Chris

[Molly]

If you are creating a solid model of porosity values and wish to limit this within a specific stratigraphic unit, use the Stratabound filters to constrain the model within the unit's upper and lower surface. You can set the nodes outside the surfaces to zero and/or limit the modeling to porosity points that lie within the surfaces. This is most easily done by first creating a stratigraphic model (Stratigraphy / Model) and then choosing the appropriate unit_top.grd and unit_base.grd models as the stratabound surfaces for the porosity model.

Once you have the filtered porosity model generated, it can be displayed in Rockplot3d as a voxel or isosurface display, and you can append the stratigraphic model display and click specific units on/off. The filtered model can also be displayed as a profile, section, and fence (choose Use Existing Model), and the upper stratigraphic surface can be displayed as a line by activating Plot Surface Profile and selecting the upper stratabound grid model.

The 2d and 3d surface profiles can also be generated separately using the Geol Utils Grid / Grid -> Profile and Grid -> Fence tools.

Molly

[chris]

Thanks for some tips. I how additional quetions:

1. Should I have porosity data in P-Data column (I work with lab data) and create porosity model for one layer in P-Data column?

2. When choosing startabound for porosity model I am supposed to use those unit_top. grid and unit_bottom. grid that were created while making stratigraphy model?I tried to do that in this way but only part of formation for which I want to make porosity model appeared (as if data from not all wellbores were included)-does it matter that for different wellbores I have different number of data points and they are from different depths in these wells. If not how to do that. Is it possible to choose as bottom model boundary depth of water level?

3. While making stratigraphy model when I choose kriging metod error occurs (Kriging error #1023 (unable to start simplex)). Why is that?

4. Which modeling metod would you recomend for porosity modeling and for stratigraphy modeling?

[Mitch]

1. Yes

2. The spacing of your data shouldn't matter but you need to make sure that your top and base units are represented in all your wells and that they represent a non-zero thickness.

As long as the grid dimensions match the XY dimensions of your model you can use any grids that you want for the top and bottom surfaces.

3. This usually occurs when there isn't enough data points for Kriging to create the variograms.

4. Inverse Distance/Isotropic or Anisotropic or even Directional Weighting if you're aware of a strong directional trend to your data.

[chris]

Thanks for your advices. They helped me a lot. Although I have some more questions.

Apart from 3D porosity model I tried to do fence diagrams and sections of porosity model (only for one formation) in P-data column. I chose stratabound (top and base of formation) in the same way like for 3D model but at the resulting drawing I have upper part of fence as if it is 0 porosity area - is it possible not to have it at all (only one formation). Beside I think that upper 0 porosity area has an impact on interpolated porosity values within formation for which I want do do a fence/section/profile.

How can I obtain a fence/section of modeled P-data for only one formation (without displaying upper formation).

How to modify legend settings?

As far as P-data model is concern, is it possible after creating a model get a slice of it (if so, how?) or should it be done by creating a profile or fence using model file?

Thanx a lot

[Mitch]

Apart from 3D porosity model I  tried to do fence diagrams and sections of porosity model (only for one formation) in P-data column. I chose stratabound (top and base of formation) in  the same way like for 3D model but  at the resulting drawing I have upper part of fence as if it is 0 porosity area - is it possible not to have it at all (only one formation). Beside I think that upper 0 porosity area has an impact on interpolated porosity values within formation for which I want do do a fence/section/profile.

How can I obtain a fence/section of modeled P-data for only one formation (without displaying upper formation).

Instead of using 0's as the replacement value use our NULL value -1E27. You'll have to make sure that you have the latest version of RockWorks since we've been gradually phasing the NULL capability in. There are still some places where using the NULL value will cause some problems. The good news is that we;ve made a thorough search to eliminate NULL conflicts in 2006.

Make sure thst "Ignore Data Outside Unit" is checked. Its a simple grid filter that will insure that only the relevant data is used in your model.

How to modify legend settings?

You can modify the Legend once the diagram is displayed in RockPlot3D. Double click or right click on the Legend icon under Legends in the Scene Tree.

As far as P-data model is concern, is it possible after creating a model get a slice of it (if so, how?) or should it be done by creating a profile or fence using model file?

Lots of options here. Take a look at the items in the Solid menu in the Geological Utilities. There are many options for extracting, smoothing, filtering, etc. You can also add vertical or horizontal slices slices to a model displayed in RockPlot3D.