RockWare Support Forum

# Reserve

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Hi all

I study rw15(demo) we are calculating reserve in sedimentary bedded area,my question is about reserve calculating methods

1-I have a model(studying area)enclosed with polygon clip,does RW extend last edge boreholes's thickness up to polygon border?

2-if I dont create a polygon, where does RW extend edge boreholes's thickness up to( from last edge boreholes to outside)??

Thanks...

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The Utilities Volume / 2D (Grid-Based) program creates a grid model with regularly-spaced points or "nodes" (X,Y), within the west-to-east, south-to-north extents of the project dimensions. It interpolates the Z (in this case, thickness) value for each node based on your control points using the selected gridding method. It is this grid model, representing thickness, which is the basis for the area and volume computations.

To compute area, RockWorks simply adds together the individual grid cell areas [sum (X * Y)]; a "cell" is the zone around each node, with a node at the cell center. Because the grid cells overlay the nodes, the total area of the model will extend half a grid node spacing outward along all axes.

To compute volume, it adds together each grid cell volume [sum (X * Y * thickness)].

You might refer to the Help messages for more information about the difference between grid nodes, grid cells, map areas, and grid areas. (Help / Contents / Reference / Gridding Reference / Grid Nodes versus Grid Cells)

If you apply a clipping polygon, any cells whose nodes lie inside the polygon will be included in the volume computation, IN THEIR ENTIRETY, even if the polygon is clipping the cell. Any cells whose nodes lie outside the polygon will NOT be included. It is the location of the grid node inside or outside the polygon which determines whether the cell is included in the calculations.

It can be helpful to use the Labeled Cells map layer to visualize the thickness values that are being computed. A zoomed-in screenshot is attached, showing computed grid node thickness values listed inside the grid cells, control point locations, and a clipping polygon.

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The Utilities Volume / EZ Volume does not utilize a grid model for volume computation. It simply connects the control points into a network of triangles, computes the volume of each triangle, and adds them together. The computations extend only to the edge of the control points. This method tends to be very conservative in its calculations.

Molly Mayfield

RockWare Inc

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