Grid Size
Horizon Gridding Project Paper 4
When setting up horizon gridding, the user is presented with Grid Spacing and Grid Size parameters. In the WorkFlow Manager, this is found on the Stratigraphic Sequence and Horizon Modeling menu under the Per Zone Parameters tab. These parameters may vary from zone to zone, so, in the upper part of this window, you must first select the zone you wish to edit:
Horizon surfaces are created by calculating regularly-spaced grids based on the input data. The minimum tension algorithm used in this calculation seeks to achieve a relatively smooth surface that passes through all the data points.
The number of output X-columns and-Yows (also known as the Grid Size) is the primary control over this calculation. Ideally you would want a single scattered data point in each cell of the grid. The program offers the user a default value but this default is only based on the number of data points, not their separation distance. The default sizes, as shown in the table below, can be changed. The overall number of grid nodes is selected based on the table below and then the X⁄Y cell size is calculated so that the cells are generally square (in other words, the default number of X-columns and Y-row is based on the aspect ratio of the X/Y ranges).
This default is ideal if the data are randomly scattered but often the spacing of your data may vary widely—for example, sparse in one area, but clustered in another; the clustered area could require a higher number of grid nodes to meet the recommended one data point per cell. In this case, the user should manually refine the grid size to suite the more closely spaced data. In this screen example shown above, the grid cell dimensions are about 42 units x 42 units. If the critical data in your horizon are, however, spaced 20 units apart, then doubling the number of X-Columns and Y-rows would be a good idea.
Just uniformly making the grid larger, however, is not a good idea because it will increase calculation time and does not ensure a better gridded surface. Also, the maximum supported number of rows and columns is 1201x1201.
A user can edit the number of X-Columns and Y-Rows either by changing those numbers directly (grid size) or by changing the dimension of the individual cells (grid spacing). If you change the grid spacing number, the program will modify it slightly to make it divide evenly into the model range.
If you want to use a certain grid size on all horizons, then go to the Utilities⁄Apply window and select Use Current Grid Size for All Horizons.
