From Great Bear Petro (image recovered 5/2/2013)
What is interesting in that GreatBear graphic is the progression of the permeability of the reservoirs. The permeability is going down by an order of magnitude for each new technology introduced. I don’t understand all the intricacies of geology but I do understand the mathematics and physics of diffusion. See here.
What decreasing permeability means is that the production rates of oil are now becoming completely diffusion-limited. In other words, the flow of oil is essentially a random walk from the source to the destination. All these new technologies are doing is exploiting the capabilities of diffusion-limited capture. This is the bottom-of-the-barrel stuff, kind of like driving your car off of fumes, or keeping your maple syrup bottle upside down, to make a more intuitive analogy out of it. The Bakken rates are likely all diffusion limited and I will be willing to bet this based on some of the data from Mason.
From Mason’s data, the flow of oil out of a hydraulically fractured well appears to be controlled by diffusional dynamics. This is what an average Bakken well decline looks like if one uses Mason’s charts.
The cumulative is the important part of the curve I believe because he plotted the instantaneous production incorrectly (which I tried to correct with the black dots).
But then if we look at Brackett’s analysis of Bakken (see below), I can better fit the average well to a hyperbolic decline model. A hyperbolic decline is an ensemble average of exponential declines of different rates, assuming maximum entropy in the distribution in rates (this works to describe lots of physical phenomena).
That conflicts with the diffusional model that better describes Mason’s data.
Now, I believe it’s possible that Brackett simply took the 1/e decline point on each well and then tried to extrapolate that to an average production. That’s the easy way out and is definitely wrong as this will always approximate a hyerbolic decline; of course I can check this if I can get access to the 3,694 samples that Brackett says goes into his analysis.
Mason and Brackett can’t both be right, as there are sufficient differences between diffusional flow decline and hyperbolic decline to impact projections. The former is steeper at first but has a fatter tail, whereas the latter will definitely decline more in the long term. Brackett says the average well will generate 250,000 barrels of oil while Mason shows twice that and still increasing.
There will be more data forthcoming in the next few years. We will see how it pans out.