The Oily Episodes from 2014

My friend Larry Smith, a geology professor at Montana Tech here in Butte, Montana, suggested that I assemble the podcasts from 2014 into thematic packages as well as the month by month packages, which is ongoing. I thought that was a good enough idea to buy Larry a beer, and here’s the first of these packages.

This group contains all the 2014 episodes tagged with oil or oil shale keywords. There are 15 of them, including two that are mostly about oil shale deposits. Running time is about an hour and twenty minutes.

Thanks very much for your interest.

—Richard I. Gibson

December 9. Green River Formation

During Eocene time, about 50 million years ago, large lakes developed in the basins between the Laramide uplifts in the Central Rocky Mountains, in what are now Wyoming, Utah, and Colorado. The adjacent mountains, including what are now the Uinta and Wind River ranges, shed sediment into the lakes. No surprises there. 

The sedimentary layers in the Green River Formation that accumulated in these lakes are thin, mostly fine-grained materials, mostly silts and muds, but there were some sands and limy sediments too. The climate was sharply seasonal, with a wet growing season and an arid season, and this is reflected in the sediments that show annual deposits, very much analogous to tree rings. These thin layers are called varves, and they average about two-tenths of a millimeter in thickness. Pretty thin. But they add up to an almost continuous record of time spanning 6 million years, from about 53 to 47 million years ago.

While the lakes were accumulating sediment, there was an extensive volcanic area not too far away. The Absaroka Volcanics were erupting in what is now northwestern Wyoming. Although the Absaroka Volcanics extend into much of Yellowstone National Park, they have nothing directly to do with the Yellowstone geysers and supervolcano. 50 million years ago, when the Absaroka Volcanics were erupting, the Yellowstone Hot Spot probably did not even exist. Eruptions related to subduction went on for millions of years, adding up to a pile more than 10,000 feet thick in places. The fine ash from those volcanoes settled into the lakes where the Green River Formation was accumulating, and they give us minerals that provide accurate age dates on the sedimentation in the Eocene lakes. 

Stingray fossil photo by Didier Descouens,
used under Creative Commons license. 

The Green River Formation has a couple zones that are lagerstatten, outstanding assemblages of well-preserved fossils. The formation is famous for its fish fossils, and there are also delicately preserved fossils of stingrays, insects, leaves, and even birds, the oldest known bats, reptiles, and mammals. It’s really a remarkable place. Some of the fossil zones contain so many contemporaneous animals that it may be that they represent widespread, nearly instantaneous deaths as a result of a major volcanic event.

Besides the fossils, the Green River Formation contains a couple other economic resources. It is one of the world’s most voluminous oil shales. At times, the lakes became anoxic – another possible cause for some of the animal deaths – and the organic matter washing into the sediment did not decompose, but became entrapped in the rock. Oil shale is solid rock – no liquid at all, in contrast to a shale oil, like the Bakken formation, where there is liquid oil, but it is trapped in tiny tiny pores that are poorly interconnected if at all. Oil shale is like the tar sands we talked about last month, but even more solid rock. It’s very energy-intensive to get oil out of oil shale. Techniques are always improving, but I think the energy return on energy invested for oil shale is something like 2 or 3 to 1 – meaning, you spend one unit of energy to get back 2 or 3. For conventional oil resources, that return is 20 to 40. So, while there might be 3 trillion barrels of oil equivalent in place in the Green River Formation, it will be very expensive to get it out. There are no current plans that I know of to exploit this resource, although there is of course research going on.

The other economic resource in the Green River Formation is trona – the world’s largest deposit of trona, by far. What is trona? Sodium carbonate. So what? You make use of trona every day – it is a critical additive to glass, which makes the melting point of silica lower and more manageable, as well as cheaper in terms of the energy cost to produce glass. Virtually all common glass today uses sodium carbonate in its manufacture. About 80% of all the trona in the world is produced from mines in southwest Wyoming. It accumulated in one of the Eocene lakes during a time of extensive evaporation when the chemical conditions were right for its crystallization.

Trona is called soda ash in the industry, and the U.S. produces about 12 million tons of it a year, more than half of which is exported. It’s one of the few mineral products for which the United States is a net exporter, and it’s a $1.8-billion-dollar business. Turkey is a distant second in terms of world production, at about 12% of the total. I have a bit more about trona in my other book, What Things Are Made Of.

—Richard I. Gibson

Absaroka Volcanics
See also Roadside Geology of the Yellowstone Country, by William J. Fritz and Robert C. Thomas (Mountain Press, 2011)

Stingray fossil photo by Didier Descouens, used under Creative Commons license. 

March 27. Kukersite

Yesterday we talked about some common rock types, granite and basalt and some others. Today, let’s talk about a very special rock type, but one that’s specific to the Ordovician.

Kukersite is oil shale – one of the richest oil shales in the world, with as much as 40% organic material in it. It’s found in Estonia.

First, let’s distinguish between oil shale and shale oil. Shale is a very fine grained rock, solidified from mud. Oil shale is a rock – not liquid – in which a lot of organic material, called kerogen, has been incorporated with the sediment. Shale oil, like the famous Bakken in North Dakota, is entirely different – it’s liquid oil, trapped in very tiny, very poorly interconnected spaces, in contrast to a good oil reservoir like a sandstone with lots of open pore space and plenty of interconnectedness to allow the oil to flow. Some of the Bakken isn’t even in shale, but it in dolomite. The main difference is that oil shale is a rock that does not contain ANY liquid oil. To get the organic matter out, you have to mine the rock, then cook it. The organic stuff might burn directly, like it does in peat or coal, or you can use a distillation system to convert the solid kerogen to liquid oil. See also this post.

The geology of the Ordovician kukersite in Estonia suggests that there were episodic periods when the waters there were anoxic – lacking in oxygen. The alternation with periods of more oxygenated water resulted in maybe 50 separate beds of kukersite, separated from each other by layers of limestone and other rock. The individual kukersite layers are typically around 20-30 centimeters thick, but some are a couple meters thick.

The setting was probably something like a low, flat tidal zone along the sea coast that was periodically cut off from circulation, so that stagnant, swampy conditions developed. What was in those swamps? This was the Ordovician, so don’t visualize the Okeefenokee Swamp, with big trees, lily pads, and such. The life that put its organic matter into these sediments was algae. In fact, algae and other microbial plants are the greatest contributors to the source rocks that make all oil and natural gas. The volume of dead animals was usually far too small to add significantly to the stuff that would become oil – so forget that attractive idea of dinosaurs in your gas tank. It was algae.

The Estonian kukersite – a rock that burns – was known as long ago as 1700, or even earlier, but its commercial development began in 1918 in the face of fuel shortages resulting from World War I and the Russian Revolution. Production has continued pretty much up to this day, with both open-pit mines and underground mines. It’s an important energy resource for Estonia. In 2011, Estonia manufactured about 11,000 barrels of oil per day from its oil shale – a bit less than half of its needs. 90% of Estonia’s electricity comes from plants fueled with oil derived from oil shale.

It’s important as a local resource, but producing oil from oil shale is expensive, given that you have to mine it, like you mine coal, then you have to input a lot of energy to heat it up to distill the oil out of it. We know how to do this technologically; the issue is the cost. Building a high-volume oil shale reduction plant might cost something comparable to an oil refinery – maybe several billion dollars or more, with many, many years before you get a real return on your investment. Conventional crude oil’s energy return on investment is 20 to 40 to one, while oil shale’s return is more like 2 to 1. You don’t make much money, and it takes a lot longer to make it. For an oil shale plant to be economic, I’ve read figures all over the map for a sustained price of oil, from $80 per barrel to $150 per barrel. I think something like a cost to produce of $90 to $100 per barrel for oil shale is reasonable. If that’s the production cost, then you have to add taxes, royalties, and so on, plus a reasonable 10% profit margin – and you end up with oil from oil shale being worth it when the price of oil is something like $130 per barrel.

So, yes, there is a LOT of oil tied up in oil shale – estimates of as much as a trillion barrels are common.  But it will be expensive to produce it.

* * *

March 27 is the anniversary of the earthquake in Alaska in 1964 that killed 139 people. Here's a link to a couple good videos.

—Richard I. Gibson

Map from USGS

Further reading:

http://www.kirj.ee/public/oilshale/3_lille_2003_3.pdf
http://pubs.usgs.gov/sir/2005/5294/pdf/sir5294_508.pdf
http://www.kirj.ee/public/oilshale/oil-2006-3-2.pdf