Layering Schemes

Filling the Zone with Layers

Once the zones are defined, each is subdivided into thin layers that become the vertical cells. How those layers follow the bounding horizons is a real choice, not a formality, because it sets the geometry along which properties are correlated. The widget fills a zone three ways; switch between them and watch the layer geometry change against a thickening zone.

Three Schemes, Three Assumptions

Each scheme encodes a depositional story. Proportional layering splits the zone into a fixed number of layers of equal proportional thickness, parallel to neither surface; it suits a conformable zone that filled gradually. Follow-top layering keeps the layers parallel to the top horizon and lets them truncate against the base; it suits a unit that built downward from a flooding surface. Follow-base layering parallels the base and truncates against the top; it suits a prograding unit built upward from the base.

Why the Choice Matters

The layering geometry decides how a high-permeability streak or a shale baffle in one well correlates to the next. Choose follow-top when the flow units really do parallel the top, and a thief zone will connect correctly between wells; choose wrongly and the model will connect rocks that are not continuous, or break ones that are. The scheme is therefore a flow decision dressed as a geometry decision.