How are flow properties related? How is flow direction calculated?

Lateral flow requires permeability values of ~0.1D or 100mD. If they are lower, then the saturation and flow velocities are too low and a hydrocarbon column will build until migration is able to proceed vertically. If vertical migration is not possible (low permeability) then all hydrocarbons will be retained within the carrier/seal. The entry pressures (Pe parameter) control the flow directions together with the dip of the layers. Entry pressures are calculated from the permeability values (see Help/Entry Pressures description. The permeability values are calculated from the lithologies and overburden depth. For a general description of the stratigraphy-lithology and porosity-permeability see the Help/Lithologies chapter. Please note how these properties are split into relationships for layers and sublayers.