doing some reading on the Bakken areaIt appears from the news releases todate the porposity and permeability are in favour with this article. Does this mean we are in a sweet spot or not the full article link https://www.theoildrum.com/node/3868
Two key properties of reservoir rock are porosity and permeability. Porosity is a measure of how much "empty" volume the rock has space available to store hydrocarbons, water, or gas. Really good formations can have porosities of 20% to 30% or more. Permeability is a measure of how easily fluid can flow through the rock. The best reservoirs have permeabilities of 1 to 5 darcies or more. (1 Darcy = 1000 millidarcies: better reservoirs are usually measured in darcies, and poorer reservoirs in millidarcies.) These high porosities and permeabilities can be found in many world class prolific oil and gas fields, such as the offshore Gulf of Mexico, the North Sea, and Saudi Arabia.
The majority of currently producing reservoirs in the onshore US are by contrast much "tighter." A pretty good reservoir might have porosities of 10% to 15% and permeabilities of 1 to 100 millidarcies (0.001 to 0.1 darcy). Reservoirs with those properties by and large would be considered very desirable reservoir in most of the onshore US and Canada. Moving downward on the scale of reservoir quality, many thousands of wells in the US are now being drilled in so-called "resource plays." These are thick, laterally extensive reservoirs usually covering thousands of square miles, and filled with hydrocarbons, but they are difficult to exploit. The Bakken Shale, along with formations like the Barnett, Fayetteville, and Woodford shales fall into this category. Permeabilities can be in the range of .00001 to .01 millidarcies, with porosities in the range of near zero to maybe 10% or a bit higher.