Sub - Two ways to quantify "uniqueness" of the two dominant oil shale plays...the Eagle Ford and Bakken (I know: taking a bit of liberty calling the Bakken a shale). A) the number of different shale formations (formation or geological formation is the fundamental unit of lithostratigraphy. A formation consists of a certain number of rock strata that have a comparable lithology, facies or other similar properties). And B) the thickness of each formation.
As far as A goes there are several dozen shale formation that contain various amounts of hydrocarbons. Not bothering to count the various different shale formation in the 10+ major US geologic basins I estimate the EFS and B represent 5% at most of the US shale formations. Globally? Way under 1%
And B by thickness? Let's keep it easy and just look at the Eagle Ford Shale. And I'll limit the depth to 16,000' which is easily reachable by the drill bit. In some areas of the Gulf Coast Basin the thickness of the sedimentary section is 60,000'+.
So the oil productive Eagle Ford Shale is a max of 300' thick. In the same area as the EFS play the total thickness of the shale formations is at least 12,000'. That doesn't include the shale intervals that exist with in the sandstone and limestone formations. So that's about 2.5%. About the same for the Bakken in the Williston Basin.
But now the combined thickness of the EFS and B compared to the thickness of all the US. Again I won't take the time to count them all so I'll toss out a minimum thickness: 600,000'. So let's over estimate EFS + B at 1,000'. So about 0.2% but certainly less.
And globallly? Crap, just making up a realistic number IMHO: less the 0.02%. Almost no one here has ever looked at a 16,000' well log and seeing how the entire stratigraphic section is totally dominated by rocks made of shale.
Of course none of those numbers are exactly correct. But it should give some sense how unique those two formations are. But that's not the only uniqueness to those plays: there is no country on earth that can match our drilling/frac'ng infrastructure AND the number of public oil companies so desperate to add proven oil reserves to their book AND the capital availability to fund such operations. There may be 10 foreign shale formation with the same or even better productivity then the EFS: and IMHO a ZERO probability of seeing the magnitude of production increases seen in Texas or N Dakota.
Thinking there might be is the equivalent of expecting some new tech that will produce more energy then the world will ever need at almost no cost.
IOW y'all ain't f*cking petroleum geologists. LOL.