There is a fair amount of gas associated with the oil, but the oil is the thing people are after. Gas produced from the Bakken tends to have a fairly high proportion of Propane, Butane, and other 'heavies' relative to Methane.
The rocks are Mississippian in age, older than the usual Cretaceous gas play.
Depending on where you are, there is an upper shale of up to roughly 30 feet in thickness, the Middle Bakken (carbonates with some sand/silt stringers), and depending on where you are, a lower shale.
Both shales are black to very dark brown and very carbonaceous, except where they are remanants just before pinch out. While they will not fluoresce under a black light, when bathed in solvent in a spot dish the presence of oil is obvious by the cut--oil fluorescing as it is washed out of the rock.
At no place does the Bakken actually outcrop: the entire formation is only known from subsurface data, cores and drill cuttings.
As a result, the entire kerogen load of the source rocks (the shales) is trapped in the subsurface, and while some of this remains bound in the shales, oil and gas have migrated to tight reservoirs in the Middle Bakken, the lower Lodgepole, and oil shows have been noted down to the sand/silt stringers in the top of the Three Forks Formation (which underlies the Bakken) especially where the lower shale is present.
The Shale was drilled in the 80s horizontally, but, for the most part, only those wells which intersected extensive fractures (and, perhaps--a theory of mine I have not had time to verify) or went out of the shale into reservoir in the adjacent Middle Bakken reached payout.
Current efforts concentrate on porous rock in the Middle Bakken.
Vertical Bakken production has existed for decades, both in the sand interval known as the Sannish (most notably southeast of Newtown, ND) and along the Nesson Anticline and in the area of the Billings nose, although wells considered to be economical were realtively uncommon.
As the Williston Basin contains a number of 'stacked' pay formations, the Bakken may have been produced in some of these wells as a secondary target prior to P&A after producing a deeper zone such as the Duperow or Red River Formations.
The wells in the Parshall play have some of the best IPs so far on the North Dakota side, most start out at 1/4 of that or less (before the frac job).
Still, a 300-500 BOPD IP of 35 to 42 API gravity is nothing to sneeze at, and at today's prices offers a reasonable ROI.
Prior to having problems with pipeline capacity, the Bakken oil was among the highest midcontinent oils in price, about the same as WTI.
Recovery rates may be understated in the case of the Middle Bakken, some operators have estimated 10% or better in Montana wells, and development of better fraccing/production techniques is ongoing and may show significant improvements.
There is a tendency to be somewhat cautious and not hype what a formation will do, and if anything, to understate it to prevent a situation in which operators are disappointed, especially if you are the head of a State Agency.
No one wants a reputation for BS in an industry where the numbers will tell the story later.
When did this attitude start? I am up to page 150 in 'The Prize' where they are trying to convince the Royal British Navy to convert to oil but don't yet have a secure source and people are lining up ten deep to plunk down their life savings on some oil speculation here or there and personality is everything because nobody knows anything.
If the estimates of over 400 billion barrels of oil are correct and operators can actually achieve 10% or better recovery rates this will eventually rival Alaska in terms of total production.
You the man Joe!!!!