@farmerman,
or, how about doing a K(v/z) analyses of a typical shale basin. Look at all the old available reports on say, the Bakken, por the Marcellus and you can see how the early state and USGS geo reports claimed that"Although significant shows of gas nd oil occur in these units, they cannot be put into production (under technology available at that time, 1940-70)due to their impermeable nature and the massive sedimentary habit . ...These units therefore serve as migration conduits" (that was said about the Marcellus Fm. in the Geostratigraphy for Oil and gas reserves of the Devonian system of Pa). Im sure that this one is on line