That's a surprise to me. Two years ago I researched this formation as a "shale unit, very low porosity and microscopic permeability", and everything I read about the hydrocarbons in it said a consistency more like tar. Hydro-fracturing simply would not work on a near-solid resource like that. It would have to be mined, like coal.
What I read now says the Bakken comprises a dolomite layer around 100-140 feet thick, bounded above and below by shale layers. Typically, the shale is the “original” source for the hydrocarbons. The dolomite is listed as 5% porosity and microscopic permeability (1-10 microdarcy's, just almost impermeable). It is in the dolomite layer (not the shale) that they are horizontal-drilling and hydro-fracturing. Estimates vary about how much of the total resource they might possibly recover this way, by over an order of magnitude, depending upon who made the estimate and what agenda they have.
For the Burgess Shale natural gas hydro-fracturing here in Texas, the estimate is that about 3% of the gas down there is actually recoverable. For the liquid in the Bakken dolomite layer, I'd simply guess that factor as 3% or less, which is nearer the 1% end of the estimate range of 1% to 50% that I saw on-line yesterday. Almost-nil permeability just has that effect, hydro-fracturing notwithstanding.
I suspect that there are residual tars left behind in both of the shale units in the Bakken formation, and that the source for the light fractions in the sandwiched dolomite layer is the lower shale member. Somehow, I don't see light fractions migrating downward from the upper shale member, so its lighter fractions are most likely now lost to us.
So, how much recoverable light oil might there be, and how much good might it do, if we can recover around 2% of it?
Oil in the Dolomite Layer:
If you guess that there's something like 500 x 500 statute miles of this formation, averaging 100 ft thick, at 5% porosity, then there might be as many as 6 trillion barrels of light oil down there.
500 mile dimension x 5280 ft per mile = 2.64E6 ft. 500 mi x 500 mi is then 6.97E12 sq ft. Multiply by 100 ft thick to obtain 6.97E14 cu.ft of dolomite rock. The hydrocarbon volume equals the pore space volume at 5% of rock volume, assuming the pores are 100% full. That's 3.48E13 cu.ft of hydrocarbons. Cu.ft volume of hydrocarbons x 7.48 gal per cu.ft is 2.61E14 gal hydrocarbons; divide that by 42 gal/barrel. That's 6.2E12 (about 6 trillion) barrels of hydrocarbon volume down there in the pores of the dolomite layer, supposedly all hydro-fracturable, very light crude.
Assume we can recover 2% of it. That's about 1.24E11 barrels of light oil that could be recovered, or about 124 billion barrels in ordinary terms. That's quite significant. I could be off by a factor of 2-3 in rock volume assumptions, more likely toward the smaller than the larger, so these figures are rather optimistic.
At our 7-8 billion barrels / year consumption in the USA, then potentially, this could power us for about 16-17 years. That really is significant, even if it is optimistic by a factor of 2-3. If it is all light oil. If we really can recover 2% of it. If the rock pores are really full. Lots of "ifs".
Let's say this oil boom lasts 20-30 years (typical for a very large field). The average production rate from the mature field (which takes several years to achieve) might be as much as around 4-6 billion barrels a year, again possibly optimistic by factor of 2-3. That's still a lot, optimistic or otherwise.
Replacing Foreign Imports:
About 1/3 of our consumption is domestic production, about 1/3 comes from Mexico and Canada, and about 1/3 comes from OPEC (which includes Venezuela, along with that idiot running it; and our “friend” Iran, with that insane group of religious fanatics running it). That's about 2.5 billion barrels per year from each source. We might very well be able to replace much of the OPEC oil with domestic from the Bakken dolomite layer, even as the other sources decline. For a little while.
But, no matter how politically expedient, it is still clearly not at all wise to count on it “ending” our dependence on foreign oil. Although, you can bet more than one GOP/Tea Party candidate will run on "why not save ourselves from oil dependence with the Bakken, if the environmentalists and Democrats would just get out of the way?" They did exactly that in '08: remember “drill, baby, drill?”
Even with the new oil boom that I did not expect to see, it’s still a comic-opera puppet-theater issue intended to distract the public from the real truths that threaten us. It’s still just a fake electioneering issue for a bunch of comic-opera buffoon candidates. Beware! I warned you!
About the Tar Shale Layers:
I saw no thickness figures on the two shale units, in the new data that I found this year. I bet they're quite thick, though. You'd have to deep strip mine it, and what I saw said it averages 2 miles down. Figure shale at 0.5% or less porosity, for maybe another handful of trillions of barrels of potentially-recoverable hydrocarbon. This tar shale stuff would be very hard to extract and process, though, and so it would be a supremely expensive product.
And, we would get it for the environmental cost of a permanent crater some 500x500x2 miles in size, which is bigger by far than the volume of Lake Superior. That shale tar is what I was thinking about when I posted what I did about "the Bakken" last year (the 3-14-10 article). That’s still true, oil boom notwithstanding.
Yep, we need to go get the hydro-fracturable light oil.
Yep, it’ll surely help with imports.
Nope, it will not “save” us.
There is no permanent answer among depletable (fossil) fuels, and never will be.
Update 6-5-2016: here is an updated curve of US oil production versus time obtained from the US EIA website. I have sketched upon it the Hubbert curve for conventional oil production. It is clear the fracking technology is a new effect. How tall this could go, and how wide this will be over time, are things that are completely unclear as of yet.
The recent explosion of US “fracking” technology (hydraulic fracturing plus horizontal-turn drilling) has modified the picture of oil prices versus recessions. Unexpectedly, the US has become a leading producer of crude oils for the world market. Plus, there has been an associated massive production increase and price drop in natural gas.
OPEC has chosen to take the income “hit” and not cut back their production in response. Their reasoning is twofold: (1) fear of loss of market share, and (2) hope that low oil prices will curtail US “fracking” recoveries. We will see how that plays-out.
Oil prices are now such (at around $55/barrel) that US regular gasoline prices are nearing $2.00/gal for the first time in a very long time. This is very close to the price one would expect for a truly competitive commodity, based on 1958 gasoline prices in the US, and the inflation factor since then.
It is no coincidence that the exceedingly-weak US “Great Recession” recovery has suddenly picked up steam. The timing of the acceleration in our economic recovery versus the precipitous drop in oil prices is quite damning. There can be no doubt that higher-than-competitive-commodity oil prices damage economies. Oil prices are a superposition of the competitive commodity price, overlain by an erratic increase from speculation, and further overlain quite often by punitive price levels when OPEC is politically unhappy with the west. That’s been the history.
This economic improvement we are experiencing will persist as long as oil, gas, and fuel prices remain low. (Government policies have almost nothing to do with this, from either party.) How long that improvement continues depends in part upon US “fracking” and in part upon OPEC. Continued US “fracking” in the short term may depend upon adequate prices. In the long term, we need some solutions to some rather intractable problems to continue our big-time “fracking” activities.
The long-term problems with “fracking” have to do with (1) contamination of groundwater with combustible natural gas, (2) induced earthquake activity, (3) lack of suitable freshwater supply to support the demand for “fracking”, and (4) safety problems with the transport of the volatile crude that “fracking” inherently produces.
Groundwater contamination is geology-dependent. In Texas, the rock layers lie relatively flat, and are relatively undistorted and unfractured. This is because the rocks are largely old sea bottom that was never subjected to mountain-building. We Texans haven’t seen any significant contamination of ground water by methane freed from shale. The exceptions trace to improperly-built wells whose casings leak.
This isn’t true in the shales being tapped in the Appalachians, or in the shales being tapped in the eastern Rockies. There the freed gas has multiple paths to reach the surface besides the well, no matter how well-built it might have been. Those paths are the vast multitudes of fractures in the highly-contorted rocks that subject to mountain-building in eons past. That mountain-building may have ceased long ago, but those cracks last forever.
This is why there are persistent reports of kitchen water taps bursting into flames or exploding, from those very same regions of the country. It’s very unwise to “frack” for gas in that kind of geology.
Induced Earthquake Activity
This does not seem to trace to the original “fracking” activity. Instead it traces rather reliably to massive injections of “fracking” wastewater down disposal wells. Wherever the injection quantities are large in a given well, the frequent earthquakes cluster in that same region. Most are pretty weak, under Richter magnitude 3, some have approached magnitude 4.
There is nothing in our experience to suggest that magnitude 4 is the maximum we will see. No one can rule out large quakes. The risk is with us as long as there are massive amounts of “fracking” wastewater to dispose of, in these wells. As long as we never re-use “frack” water, we will have this massive disposal problem, and it will induce earthquakes.
Lack of Freshwater Supply to Support “Fracking”
It takes immense amounts of fresh water to “frack” a single well. None of this is ever re-used, nor it is technologically-possible to decontaminate water used in that way. The additives vary from company to company, but all use either sand or glass beads, and usually a little diesel fuel. Used “frack” water comes back at near 10 times the salinity of sea water, and is contaminated by heavy metals, and by radioactive minerals, in addition to the additives. Only the sand or glass beads get left behind: they hold the newly-fractured cracks in the rocks open, so that natural gas and volatile crudes can percolate out.
The problem is lack of enough freshwater supplies. In most areas of interest, there is not enough fresh water available to support both people and “fracking”, especially with the drought in recent years. This assessment completely excludes the demand increases due to population growth. That’s even worse.
This problem will persist as long as fresh water is used for “fracking”, and will be much, much worse as long as “frack” water is not reused. The solution is to start with sea water, not fresh water, and then to re-use it. This will require some R&D to develop a new additive package that works in salty water to carry sand or glass beads, even in brines 10 times more salty than sea water.
Nobody wants to pay for that R&D.
Transport Safety with Volatile “Frack” Crudes
What “fracking” frees best from shales is natural gas, which is inherently very mobile. Some shales (by no means all of them) contain condensed-phase hydrocarbons volatile enough to percolate out after hydraulic fracturing, albeit more slowly than natural gas. Typically, these resemble a light, runny winter diesel fuel, or even a kerosene, in physical properties. More commonly, shale contains very immobile condensed hydrocarbons resembling tar. These cannot be recovered by “fracking” at all.
The shales in south Texas, and some of the shales and adjacent dolomites in the Wyoming region actually do yield light, volatile crudes. The problem is what to transport them in. There are not enough pipelines to do that job. Pipelines are safer than rail transport, all the spills and fires notwithstanding.
The problem is that we are transporting these relatively-volatile materials in rail tank cars intended for normal (heavy) crude oils, specifically DOT 111 tank cars. Normal crudes are relatively-nonvolatile and rather hard to ignite in accidents. DOT 111 cars puncture or leak frequently in derail accidents, but this isn’t that serious a problem as long as the contents are non-volatile. These shale-“frack” light crude materials resemble nothing so much as No. 1 winter diesel, which is illegal to ship in DOT 111 cars, precisely since it is too volatile.
The problem is that no one wants to pay for expanding the fleet of tougher-rated tank cars. So, many outfits routinely mis-classify “frack” light crudes as non-volatile crudes, in order to “legally” use the abundant but inadequate DOT-111 cars. We’ve already seen the result of this kind of bottom line-only thinking, in a series of rather serious rail fire-and-explosion disasters, the most deadly (so far) in Lac Megantic, Quebec.
Volatile shale-“fracked” crudes simply should not be shipped in vulnerable DOT 111 cars, period. It is demonstrably too dangerous.
“Fracking” shales for natural gas and light crudes has had a very beneficial effect on the US economy and its export-import picture. We should continue this activity as a reliable bridge to things in the near future that are even better.
But, we must address the four problem areas I just outlined. And I also just told you what the solutions are. The problem is, as always, who pays. What is the value of a human life? What is the value of a livable environment? It’s not an either-or decision, it’s striking the appropriate balance!