It was only a couple of years ago. The price was above $75 or $80 at the time.
I agree with your remark that the $50 is a moving target. But, again, if it can never be commercially viable, no need to shut it down legally. I notice driving through the area a lot of drilling rigs. I assume they are exploring, to nail down exactly where the deposits are. In the current political climate, its a dead issue. But someone is doing a lot of exploring.
There are other conventional oil and gas producing formations in the area and that is probably the explaination for most of the drilling activity you are seeing although some may be wells just to tie down the exact dimensions of the Green River Formation.
I am not familiar with the geology of the area, but as in all oil producing areas there are layers of different types of sedimentary rock on top of each other, some containing commercial quanities of oil and gas and some not. The Green River formation is just one of the layers.