An echoing Shhh, or more on mining of oil shale

So, there we have all this oil, sitting in these nice thick oil shale beds out West and just waiting to turn some local in Colorado into the next "world's richest person". All they have to do is to figure out how to get the oil out of the ground cheaply enough to make money from it. (And if you remember from the last post there are over 2,000 patents on ways to do this - if it were that simple there would not be nearly that many). Congress thinks so too, since the Energy Policy Act of 2005 called oil shale a strategically important domestic resource (pdf file).

What's the big deal? Drill a hole down there and it flows it - isn't that how it works? Well not in this case. As I said the oil is really a waxy kerogen that does not want to flow at all. And there is also a problem with the rock. About 40 years ago a guy called Brace (Ref 1) found that the cracks in a rock are related to the size of the grains of the material that make up the rock. A rock with large grains has large cracks, and this gives it a permeability which is the joining of these cracks to give a path through which oil (or water or gas) can flow through the rock. It also gives the rock its porosity which are the holes in the rock into which the oil can collect. Unfortunately the grain size of the average particle in oil shale is around 5.8 microns. This is about a tenth of the thickness of a human hair, medium human hair being about 60 - 90 microns wide. As a result the typical oil shale has very poor porosity, and it is only when it has a high oil content (above 50 gallons/ton) that permeability can be easily measured (Ref 2) , below 20 gal/ton it becomes very difficult, because it is so small. The average grade is around 25 gal/ton.

The simple message from those numbers is that oil will not normally flow into any holes that are drilled into oil shale. So where do we go from here? Well it you won't go to the mountain, then the mountain must come to you. In other words, let's mine the oil shale and get it out that way. As it happens the layers are thick enough so that they can be mined by a number of different ways, including surface mining, what we call room and pillar mining and then by a third method that I will, for now, call sub-level stoping. Remember that we need to break the rock down into pieces no bigger than 3-inches in size for the retorts. Union Oil (now Unocal) used the room and pillar method for their mine at Parachute Creek, where mining interest is growing again . Room and pillar mining was also used for the Colony Mine, which was the largest project in hand back in the 1980's. Since there have been a number of reasons suggested for the closing of that project, it might be appropriate to ask you to remember the words I quoted from Harold Carver. And then read on:
Tosco's interest in the Colony project was sold in 1979, and again in 1980, to Exxon Company for the Colony II development. Exxon planned to invest up to $5 billion in a planned 47,000 bpd plant using a Tosco retort design. After spending more than $1 billion, Exxon announced on May 2, 1982, that it was closing the project and laying off 2,200 workers. . . . . . The economic incentive for producing oil shale has long been tied to the price of crude oil. The highest price that crude oil ever reached -- $87/bbl (2005 dollars) -- occurred in January 1981. Exxon's decision to cancel its Colony oil shale project came a year and half later, after prices began to decline and newly discovered, less-costly-to-produce reserves came online. . . . . oil had become plentiful, with about 8 to 10 million barrels per day in excess worldwide capacity, and the trend in rising oil prices had reversed after early 1981.
The failure, in short, at that time became one due to economics, rather than technology.

Using a machine to mine the oil shale poses some problems, since it is much stronger than, for example, the tar sands of Alberta, that can be scooped up with a shovel. Rather the rock has a strength that decreases with oil content down to about 13,000 psi with an oil grade of 30 gal/ton, at which point it stabilizes even as the grade increases. This means that the openings for mining can be quite large, as they need to be to achieve the tonnages planned. Rooms mined with the rock were some 55-ft wide, with 58-ft pillars. It also means that the machines to grind the rock from the solid will need, either to be jet-assisted, or of relatively large size. One of the first proposed (for you EROI fans) was designed to produce 17,500 tons per 2-shift day, with an oil content of 40 gal/ton, and with 6.5 operating hours in a shift. Machine power requirements would be 37,500 kwh per working day (Ref. 3).

The advantage of the large mining machines, over drill and blast methods, which remain the most common practice, is that the operation is continuous, with rock being carried away by conveyors, and production need not stop to ventilate away the products from the use of explosives. On the other hand the use of explosives to fragment the rock does provide a relatively effective way to fracture it (though with less size control). One of the questions that I have always had, though, in doing EROI on explosive use is whether to count the energy input as that required to make the explosive, or that liberated when it is set off.

In the days when the industry was last planned, the throughput for single plants was considered to be on the order of 100,000 tons/day. A ton occupies 16 cubic feet (Ref 4) and so if the mine is 30 ft high, a cubic foot of floor space would have 2 tons of rock on it. This would translate into having to mine 2.5 acres of rock per day. The point has been made, however, that underground mining of layers of rock one slice at a time down through the deposit would be inefficient and energy intensive. Further that it would be restricted only to mining the high grade layers.

The matter of mining, by undergound methods, the rich, deep oil shale beds in the center of the basin probably needs little consideration because better methods of producing the resource appear to be at hand. If our civilization has any conscience and if it has any regard for posterity it cannot give serious consideration to any method of production of shale oil from the center of the basin that does not result in substantially complete recovery. Our civilization has passed the stage in which it can kill the whole buffalo merely to consume the tongue and liver as was done in this area less than a century ago.
What he is arguing against is the intent to set up the mine to mine out the rich layers, so that when our grand-children have to mine the rest they must work in the dangerous conditions of a partially mined volume, with only the poorest grades of shale as a reward.

In contrast he argues that the area should be strip-mined since even with a 1,000 ft cover, the thickness of the oil shale would justify the process as a means of recovering the entire volume of oil from the deposit. Part of the problem comes, of course, not only from the fact that a hole a mile in diameter and 3,000 ft deep has been created, but that also all the material that has been mined, has to be stored before being returned. And this is one of the significant problems that mining the deposit either by strip mining or by underground mining generates, that of the waste volumes and condition.

For a long time mining has used some of the waste rock that has been mined to pump back into the mine and fill the holes left. By mixing a small amount of cement with the rock powder it can be made strong enough that the rest of the valuable ore can be mined, while the roof is held up by the newly placed columns. However, when you mine and mill rock it is broken into small pieces. These bulk in volume by about 60% on average, over the original volume of the rock, and so even with the use of the mine to put back some of the rock there will be about 40% of it left for disposal somewhere else. (Note that this does not include the thermal swelling that occurs when the rock is heated - I will get to that in a couple of posts).

But it should be pointed out that there is already some 50-odd years of experience in dealing with this waste in the area, and while I am not familiar with the problems and their solution, the general mining practice with waste fills is ultimately to cover and seed them so that there is a binding vegetation - unfortunately this, as with some of the other parts of the extraction process, requires considerable water, and that is an issue that we haven't reached yet. But, on the other hand, we don't seem to hear much about the piles that already exist.

Again I am going to pause here, since the post may otherwise get too long, but next time I will talk a little bit about the nuclear option, that seems to pop up in comments quite a bit.

Ref. 1 Brace W.F. "Dependence of Fracture Strength of Rocks on Grain Size," 4th Symposium on Rock Mechanics, Penn State, 1961,
Ref. 2 Thorne H.M. "Bureau of Mines Oil-Shale Research", First Symposium on Oil Shale, CSM, 1964.
Ref. 3 Hamilton W.H. "Preliminary Design and Evaluation of the Alkirk Oil Shale Miner," Proc. 2nd Annual Symposium on Oil Shale, CSM, 1965.
Ref. 4 Ertl T. "Mining Colorado Oil Shale", Proc. 2nd Annual Symposium on Oil Shale, CSM, 1965.

A very helpful post--thanks.

The numbers quickly get mind-numbing on this: they're both too large, and way too small, at the same time.

Based on your numbers, the hypothetical 100,000 ton per day operation would yield 59,500 bpd (average grade, 25 gal/ton) to 119,000 bpd (high grade, 50 gal/ton). At an arbitrary $70 per barrel, that's gross revenues of $4 to $8 million per day, or $1.5 to $3 billion per year. That's a pretty big business for most industries.

Unfortunately, for all the investment, and all the environmental damage, the output from this operation is maybe 0.3% of US daily consumption. Put this output in the context of declining US and world oil output, and it looks like a pretty small band-aid.

I think we'll need every little bit of fuel that is economically and environmentally feasible to produce--and current evidence (as RR points out) suggests that we'll produce everything regardless of environmental or economic concerns. Shale oil is probably part of that picture.

I guess there is no problem with clutching at straws as long as you know they are straws, and you work to come up with better approaches (like conservation).

Alternatively, at 25gal/ton, 1 million barrel per day production (5% of US consumption) would require mining and processing of just over 600 million tons (Mt) oil shale per year.  That is equivalent to about 60% of the tonnage of US domestic coal production (1030 Mt/y).

To achieve oil independence, oil shale would need to be mined at a rate equal to more than 8 times current US coal production.

Energy content in 1 ton of oil shale: 2700MJ
Energy content in 1 ton of coal: 23000MJ

Compared to coal, mining the same tonnage of oil shale yields around 12% of the energy.

Hmmm, if insitu is not feasible, can't see this one flying somehow and we haven't even gotten to EROI, water usage, disposal of the waste material, GHG production...

Hi cactus, very good point indeed.

Knowing that the EPR of Coal is around 30, that 12% figure gives us some (but small) hope about Shale.

If 1 ton of coal yields 23000 MJ, the energy spent to mine it would be about 770 MJ (766,666 actually).

So using the same techniques, and assuming that mining 1 ton of Shale takes the same energy has minig 1 ton f Coal, Shale would have an EPR of 3.5. This is lower than Nuclear but higher than Onshore Wind.

Still that rock would have to be heated up, lowering even further the EPR value.

You are way off on wind power EROEI. The larger turbine recoop production energy in about 1 year. With a 20 service life minimum that's a 20:1 EROEI.
Hello Heading Out,

Well Done!  It will be interesting to compare & debate these Shale Oil Threads against AlanfromBigEasy's upcoming article on if mass-transit conversion is a better economic & ecologic investment.

Bob Shaw in Phx,AZ  Are Humans Smarter than Yeast?

Bob, to go Monty Python on you, "Would that be brewer's or baker's yeast?"
Thanks so much for the Oil Shale posts.  I was intrigued a few weeks ago when I clicked on an ad on the TOD website that turned out to be a hype for shale oil -- the next Saudi Arabia.  I am really happy that you are putting some science behind these claims.
We would need to mine nearly 40 million ton/day and use nearly 100 Gwh/day of energy to do it in order to mine enough liquid fuel at current use levels. Then we add in extraction and refining energy. At $25,000 capital investment per bbl/day capacity we are looking at maybe $10,000,000,000,000 of capital investment. Wind farms, algae farms, PVs, and batteries start looking very good at those prices.
A very informative post, HO, but depressing. Enormous environmental destruction (even if it were only the water, which it isn't), for what? Even the slightest move toward reducing our consumption of oil would produce a saving greater than any projected return from mining shale.,,1808314,00.html

It is impossible to speak of concern for grandchildren in this regard at all.

With regard blasting methods: There is another technology that is fossil fuel dependant. The most common explosives used in this work would be ANFO (ammonium nitrate + fuel oil) or UNFO (urea nitrate + fuel oil) In both cases you are talking about  N. Gas being used to produce ammonia or urea, then nitrating it with concentrated nitric acid produced by, you guessed it catalytic oxidation of ammonia from N. Gas, then milling it to a critical size, and then finally infusing the milled prills with about 6% by weight of #2 fuel oil, derived of course from OIL.

My guess though is that at the end of the day you extract a very high percentage of the potential fossil fuel energy when you actually detonate it, still it's all fossil fuel power at the end of the day

Heading Out

It is nice to see someone posting factual and referenced information on oil shale.  You describe the increase in the bulk volume due to mining and crushing accurately. I am anxiously waiting to see what you have to say about the thermal swelling that occurs when the rock is heated.

My experience is that most oil shales around the world actually shrink during heating. The one scientific source that I could find showed that 20.6 gal/ton oil shale will compact (not swell) 15 to 20% if heated to 800 F.
(Ref. Burwell, E.L. et al. "Permiability changes and compaction of broken shale during retorting," USBM Report of Investigation 7860, 1974.)

I also enjoyed the article.  This is a question for the site editors.  I teach an energy unit in one of my freshman classes and would like to use some of the excellent research posted on TOD as reading assignments (this article is a good example).  Looking over the site, I don't see an easy way to find archived material indexed by subject.  For example, Wind, Coal, (Coal to Liquid), Saudi production, Shale, Nuclear, Conservation, etc.
Have I missed a way to do this?  Would this be an impossible task?

One of the best features of TOD, IMO, is the ratio of fact/opinion ratio tends towards the high end - though I enjoy reading many of the opinions as well - making it one of the more valuable and educational blog sites.  

We link some of the posts by reference at the end  - for example those on petroleum production, and mining , and I will generate a link between the parts of this series beginning with the next post (though there will only be about 6 in the series - since I don't plan to emulate Robert Jordan).

We do try putting tags at the top of the posts, but that depends on the author and sometimes it is difficult to decide what should, and should not, be included.