[yesplease]

Energy (though that has grown as I've shown, and as the Japanese example has shown) is just one (or a few) of the resources that we use to keep the economic wheel turning and growing. So it's pointless showing graphs of one or two resource consumption curves.

It's fine if you want to include other resources, but how are you going to relate them? Energy sources are easy to relate to but how are you going to compare increases or decreases in other commodities over some time period consistently?

On a finite planet, economic growth is unsustainable. If resource consumption ever flat lines (as you put it) that is the end of economic growth.

First things first, in a finite solar system, sustainable resources are unsustainable. Sustainability is only defined over some time period and depends on many things, IMO it's use is abused.

Yes, per capita usage may be showing a plateau or even a decline but that translates to higher energy usage (with the growth of developing nations, the per capita use may even be increasing, judging by the big increases in recent years). But you say that energy can just be increased from some source or another, without regard for the fact that energy takes other resources to harness it (and the harnessing takes energy).

Considering that population growth can't go on forever, I would think that a increase in world GDP per capita while energy use, more or less, flat lines per capita, indicates that GDP can go up while resource consumption stays the same. I'm not saying it can go on forever, just that it can happen contrary to what you stated earlier. On a worldwide scale, energy consumption reflects resource appropriation since we can't acquire or recycle resources w/o energy, this would imply that the resource acquisition is reflected in energy consumption. Not that this can go on forever, just that it can happen, which was my initial response to you statement that economic activity cannot increase with resources increasing.

[yesplease]

Oil shale with an EROEI of 3:1 could still be worth the effort if we need the chemicals.

Considering the EROEI of oil's energetic products is currently about 3:1, that seems reasonable...

[TonyPrep]

Considering that population growth can't go on forever, I would think that a increase in world GDP per capita while energy use, more or less, flat lines per capita, indicates that GDP can go up while resource consumption stays the same. I'm not saying it can go on forever, just that it can happen contrary to what you stated earlier. On a worldwide scale, energy consumption reflects resource appropriation since we can't acquire or recycle resources w/o energy, this would imply that the resource acquisition is reflected in energy consumption. Not that this can go on forever, just that it can happen, which was my initial response to you statement that economic activity cannot increase with resources increasing.

I agree that for some arbitrary short period, it might be possible to show economic growth whilst consumption of some resource is flat, perhaps demonstrating improved efficiency in using that resource, or a move to some substitute resource. I agree that energy is needed to extract and make use of other resources but a flat line would indicate, again, better efficiency at extracting and using those resources. Efficiencies have limits. Energy, however, has not flatlined (as the figures I gave above show), even if some regions have stalled their per capita use.

If we can ever see population growth cease, without it being through starvation or habitat destruction, it would be interesting to see how the use of resources grows, though I still can't see how economic growth can continue without using more resources, even if that growth in resource use slows markedly.

I agree that the word "sustainable" has been misused. Of course, nothing can be sustained for ever, except, possibly, the universe. However, as we start to see critical limits being reached within a generation or two, the point is moot. If I can see trouble for my kids or their kids (if they have any), then that is too short a time, to my mind. And I'd have to block out what the reaction of generations would be beyond that, if we continued to push the limits.

But this is getting away from the topic of this discussion; I just wanted to put it out that economic growth can't go on indefinitely (and probably not for much longer), so there is little reason to get too excited about a trickle of oil from shale.

[yesplease]

I think stating it can't go on infinitely is a bit trivial don't you? I might as well state I can't have an infinite number of tuna sandwiches.

That being said, I think my initial response to your statement was reasonable given the magnitude of waste present in our society, considering you or I never stated an interval wrt the statement.

Economic growth requires increasing resources.

Since when? Unless of course you're referring to the growth of those selling said resources.

Economic growth does not always require increasing resources, which your figures for per capita energy consumption, compared to per capita GDP have shown.

[TonyPrep]

I think stating it can't go on infinitely is a bit trivial don't you? I might as well state I can't have an infinite number of tuna sandwiches.

I agree, which is why I never said that.

That being said, I think my initial response to your statement was reasonable given the magnitude of waste present in our society, considering you or I never stated an interval wrt the statement.

A lot of economic activity is dependent on wasteful expenditure.

Economic growth does not always require increasing resources, which your figures for per capita energy consumption, compared to per capita GDP have shown.

They didn't show that, they showed that per capita energy consumption has been, and possibly could be, more efficient. Remember that resources are not just energy and nor is per capita energy consumption indicative of total energy reduction (or even stabilisation). All you've shown is that GDP growth can be made less resource intensive (or, in your example, less energy intensive). And I have never argued that that couldn't happen. Economic growth requires more resources.

However, remember that even a stable economy that uses finite resources, cannot use those resources sustainably (since they are finite). If one is only interested in sustaining society, more or less as it is now, over a few decades, then that might be possible, though I don't think it is likely.

[yesplease]

I think stating it can't go on infinitely is a bit trivial don't you? I might as well state I can't have an infinite number of tuna sandwiches.

I agree, which is why I never said that.

Or indefinitely if you want to be specific. In this context they mean the same thing AFAIK, but there's nothing wrong with minding P's and Q's.

I just wanted to put it out that economic growth can't go on indefinitely

That being said, I think my initial response to your statement was reasonable given the magnitude of waste present in our society, considering you or I never stated an interval wrt the statement.

A lot of economic activity is dependent on wasteful expenditure.

Sure thing. But that economic activity can result in a much smaller growth in GDP compared to alternative applications if externalities are not considered.

Economic growth does not always require increasing resources, which your figures for per capita energy consumption, compared to per capita GDP have shown.

They didn't show that, they showed that per capita energy consumption has been, and possibly could be, more efficient. Remember that resources are not just energy and nor is per capita energy consumption indicative of total energy reduction (or even stabilisation)

Resources are included in net energy use since w/o that energy, we would have no other resources. We have to expend energy, and the energy we expended to acquire resources is indicative of the cost of those resources. Like I said before, if you have some other reasonable metric to relate resource consumption besides energy, as well as consumption figures, feel free to bring it to the table. But, w/o convincing info that a comparison like that is possible, I will stick to comparing resource acquisition via the energy required to acquire, process, and use said resources.

Economic growth requires more resources.

This is not true in all cases. Since resource acquisition, processing, and use requires energy, the cost of those resources is illustrated in energy use. If you can provide proof otherwise as well as a metric for comparison, please do, but resource use necessitates energy use, and because of this energy use reflects resource use. Like I said before, energy use strongly correlates with GDP, however, we have no had any significant environmental restrictions of energy use that would illustrate a disconnect. We have however had social incidents that limited energy use, and by proxy, resource use, and during the years after, GDP per capita[1] climbed while energy use per capita[2][3] remained more or less the same.

Economic growth does not always require more resources, be them energy based or not.

However, remember that even a stable economy that uses finite resources, cannot use those resources sustainably (since they are finite). If one is only interested in sustaining society, more or less as it is now, over a few decades, then that might be possible, though I don't think it is likely.

I agree that our society will change. We can't waste oil at the rate we are now forever.

[1]http://econ161.berkeley.edu/TCEH/1998_Draft/World_GDP/Estimating_World_GDP.html
[2]http://en.wikipedia.org/wiki/World_population
[3]http://www.allcountries.org/uscensus/1388_world_primary_energy_consumption_by_region.html

[TonyPrep]

I think stating it can't go on infinitely is a bit trivial don't you? I might as well state I can't have an infinite number of tuna sandwiches.

I agree, which is why I never said that.

Or indefinitely if you want to be specific. In this context they mean the same thing AFAIK

That's fine, but you stated that I said infinitely, when I didn't. That would be absurd. Indefinitely certainly implies a very long time and certainly many generations.

Resources are included in net energy use since w/o that energy, we would have no other resources.

Very true. I doubt that all resources require energy that is accounted for in official statistics but I'd agree that resource use cannot increase without an increase in energy, though the equation is unknown in total.

Economic growth requires more resources.

This is not true in all cases. Since resource acquisition, processing, and use requires energy, the cost of those resources is illustrated in energy use. If you can provide proof otherwise as well as a metric for comparison, please do, but resource use necessitates energy use, and because of this energy use reflects resource use.

Energy use has been growing, as has GDP. Correlation is not causation but you've suggested that energy use gives an indication of resource use so you must agree that economic growth over the last 25 years (see the EIA figures I posted above) has been accompanied by energy growth (your proxy for resource growth).

Economic growth does not always require more resources, be them energy based or not.

I'll acknowledge that there may be periods when efficiency drives can decrease the resource intensity. Efficiencies, however, have limits. Growth in populations, and larger markets, can increase efficiencies of scale, which I'm sure is one reason why resource use may not have increase proportionately to GDP growth (though it has still increased).

However, remember that even a stable economy that uses finite resources, cannot use those resources sustainably (since they are finite). If one is only interested in sustaining society, more or less as it is now, over a few decades, then that might be possible, though I don't think it is likely.

I agree that our society will change. We can't waste oil at the rate we are now forever.

Agreed. We can't use oil for any purpose at the rate we are now. We must reduce rates of resource consumption towards their renewal rates. If we don't do it willingly and in a managed fashion, nature will do it for us.

[yesplease]

That's fine, but you stated that I said infinitely, when I didn't. That would be absurd. Indefinitely certainly implies a very long time and certainly many generations.

Yup, seems like another case of vague language since on one hand it refers to unlimited, and on the other, an indefinite quantity. Like ya said you meant a long time, but not an unlimited time or indefinite time, kinda like some combo of both meanings?

in·def·i·nite
–adjective
1. not definite; without fixed or specified limit; unlimited: an indefinite number.
2. not clearly defined or determined; not precise or exact: an indefinite

Very true. I doubt that all resources require energy that is accounted for in official statistics but I'd agree that resource use cannot increase without an increase in energy, though the equation is unknown in total.

I bet, or at least hope, an estimate is included in the total, but they may not try to account for all sources. As for whether resource use can increase w/o an increase in energy, I suppose it could if efficiency increased.

Energy use has been growing, as has GDP. Correlation is not causation but you've suggested that energy use gives an indication of resource use so you must agree that economic growth over the last 25 years (see the EIA figures I posted above) has been accompanied by energy growth (your proxy for resource growth).

Sure thing, but w/o energy growth dropping it's hard to see how GDP can diverge from it, aside from the occasional shortage due to social reasons. Like I said before, given the magnitude of inefficiency, I think we could grow the economy while maintaining or even reducing energy usage, it's just that there haven't been consistent incentives/conditions to do so.

]I'll acknowledge that there may be periods when efficiency drives can decrease the resource intensity. Efficiencies, however, have limits. Growth in populations, and larger markets, can increase efficiencies of scale, which I'm sure is one reason why resource use may not have increase proportionately to GDP growth (though it has still increased).

The worst part about the limits of efficiency tends to be how we define it IMO. Take well to wheels efficiency. According to this a large SUV is more efficient than a sub-compact hybrid because on average it's engine operates more efficiently. Even though it may need about six times more fuel to do what both of them do 95+% of the time, transport one or two people with minimal cargo. It seems like a lot of efficiency improvements (deliberately?) miss the bigger picture.

[TonyPrep]

Like I said before, given the magnitude of inefficiency, I think we could grow the economy while maintaining or even reducing energy usage, it's just that there haven't been consistent incentives/conditions to do so.

I think that's possible, but I don't think the periods in which that would occur would be very long - and couldn't be described as indefinite

The worst part about the limits of efficiency tends to be how we define it IMO. Take well to wheels efficiency. According to this a large SUV is more efficient than a sub-compact hybrid because on average it's engine operates more efficiently. Even though it may need about six times more fuel to do what both of them do 95+% of the time, transport one or two people with minimal cargo. It seems like a lot of efficiency improvements (deliberately?) miss the bigger picture.

Isn't this something like Jevon's Paradox? Efficiencies could reduce resource intensity but may not reduce resource growth because we do more with each unit of resource than the efficiency gives us. But there is no doubt that efficiencies must have limits because nothing can be even 100% efficient. Some imagine a perfect world in which efficiency is increased by some percent each year. If that were ever possible, we'd soon end up with almost no room to increase efficiency, leaving us needing to increase resource use by exactly the same percentage as GDP growth.

[yesplease]

I think that's possible, but I don't think the periods in which that would occur would be very long - and couldn't be described as indefinite

I think the size of the indefinite, if that even makes sense, is what would be particularly interesting.

The worst part about the limits of efficiency tends to be how we define it IMO. Take well to wheels efficiency. According to this a large SUV is more efficient than a sub-compact hybrid because on average it's engine operates more efficiently. Even though it may need about six times more fuel to do what both of them do 95+% of the time, transport one or two people with minimal cargo. It seems like a lot of efficiency improvements (deliberately?) miss the bigger picture.

Isn't this something like Jevon's Paradox? Efficiencies could reduce resource intensity but may not reduce resource growth because we do more with each unit of resource than the efficiency gives us. But there is no doubt that efficiencies must have limits because nothing can be even 100% efficient. Some imagine a perfect world in which efficiency is increased by some percent each year. If that were ever possible, we'd soon end up with almost no room to increase efficiency, leaving us needing to increase resource use by exactly the same percentage as GDP growth.

IMO what I was referring to was just an example of constructing statistics to be deliberately misleading. Jevon's paradox, or specifically the related idea that wasn't about coal in the UK, the rebound effect/waste homeostasis is what I think you're referring to. In terms of efficiency gains, what generally happens is that people will do slightly more because of the lower cost, but generally not enough to wipe out any advantage from the efficiency gain. It's something to remind us that efficiency won't always perform precisely as advertised because consumption tends to go up a bit.

That there is an increase in consumption associated with increases in efficiency is well-supported by economic theory and studies in specific sectors looking for the effect, but debates remain over how important the effect is in different circumstances. In developed countries, the rebound effect is small to moderate, ranging from roughly 5% to 40%, depending on the type of energy used.

That being said, I see no reason why consumption can't go down and efficiency can go up over some time period with the proper conditions. I think this would be seen if the land export model came to be, since a lot of manufacturers have cars projected to come out that use very little oil right around when the land export model is projected to start destroying supply for countries that don't produce oil. Coincidence? Maybe... But based on what I've seen, eg insurance companies on the east coast, it's best to look at what companies do and not what they say to get a glimpse at what they're thinking.

[TonyPrep]

That being said, I see no reason why consumption can't go down and efficiency can go up over some time period with the proper conditions. I think this would be seen if the land export model came to be, since a lot of manufacturers have cars projected to come out that use very little oil right around when the land export model is projected to start destroying supply for countries that don't produce oil. Coincidence? Maybe...

It could happen but I doubt it would enable growth to continue, or not for very long. In the case of more efficient cars, it takes 15 years to turn around the car fleet. That's not to say efficiency gains won't be seen before that, but the turnaround time might be slowed by any recession at the time. If you can't afford to get a different car (or someone can't afford to buy yours) then you're stuck with what you have and will have to make do a best you can, as the supply dwindles.

[yesplease]

It could happen but I doubt it would enable growth to continue, or not for very long. In the case of more efficient cars, it takes 15 years to turn around the car fleet. That's not to say efficiency gains won't be seen before that, but the turnaround time might be slowed by any recession at the time. If you can't afford to get a different car (or someone can't afford to buy yours) then you're stuck with what you have and will have to make do a best you can, as the supply dwindles.

Actually, most of the cuts would probably be to current driving habits in a situation like the land export model. Manufacturers would have to offer 50-250mpg cars for people to buy new if oil was at $300+/bbl assuming the dollar doesn't drop farther, which it just might do. Given the sales of new autos in the past during high prices/a recession, I doubt sales of any new efficient offerings would taper off. Not that new cars are need to cut demand, plenty of used cars are capable of 40-50mpg stock, or with a few mods, and are still plentiful.

I've often wondered what the "peak" in oil price would be in the developed world given how much/willing people can/are to cut back, use alternate forms, carpool, and/or drive more efficient cars more efficiently. I bet ya, dollars to doughnuts, the oil and auto industries among others, insofar as they are distinct, have already modeled the consumer response to any increase in price just as much as they have modeled the oil depletion curve in order to maximize profitability and minimize risk. It would be fiscally irresponsible not to...

[Tanada]

Question for ROCKMAN, Rockdoc123 and any other petroleum geologists who happen to be hanging around here. I have seen it said many times that the Green River Shale formation never matured into liquid oil and is still kerogen in a rocky matrix because it was never buried deep enough to cook all the way. A) Is that true? B) what about the deeper parts of the formation on the bottom? C) Does anyone produce liquid oil from the formation at all, or is it still a pipe dream? D) Back in the early 1980's it was predicted to be the Next Big Thing with 3 TRILLION barrels of OOIP, is it a forever dream?

[ROCKMAN]

From: http://canaryusa.com/oil-production-in- ... -fracking/

Fracking Isn’t the Answer in the Green River

While the recent boom in oil production across other states has been driven by the advanced technique of hydraulic fracturing (“fracking”) – a method that involves blasting a mixture of water, sand, and chemicals at a high pressure to release trapped oil and gas from shale formations – engineers in Colorado are discovering that the nearly 2 trillion barrels of Green River oil can’t be recovered this way. The “simple” explanation for this is that these other plays, such as the Bakken in North Dakota and Eagle Ford in Texas, are not at all similar to the Green River formation and the oil shale rock in Colorado’s Western Slope.

The differences between oil extracted from shale formations (like the oil in Bakken and Eagle Ford) and oil shale (like the Green River Formation and Western Slope) are vast and have been a great source of confusion. The oil recovered in the Bakken and Eagle Ford is actual oil that doesn’t flow properly because it’s trapped in the shale formation. This “tight oil” can be released thanks to advances in fracking technology. On the other hand, oil shale is a much different prospect than this tight oil. Oil shale is an inorganic rock containing kerogen, a precursor in the production of petroleum. In order to produce oil, the oil shale and its kerogen need to be heated. When superheated to 5,000 degrees Fahrenheit, kerogen undergoes various chemical reactions, resulting in a vapor containing a mixture of hydrocarbons and other organic compounds. When this vapor condenses, it becomes oil that can be refined to produce liquid fuels and lubricants.

Producing oil from oil shale has been done in one of two ways: a.) The oil shale is brought to the surface and cooked; or b.) An electric heater is placed deep beneath the surface at the base of the rocks to heat the shale, convert it into liquid oil and gas, and then bring it to the surface. {Shell Oil shut down its one demonstration project a couple of years ago}

Unfortunately, neither method has proven economically viable to this point. In recent years, both Shell and Chevron have abandoned their respective oil shale efforts in Colorado, after investing tens of millions of dollars into finding profitable extraction methods. And so, for now, the alluring deposits of oil in this fine-grained sedimentary rock in the Green River – that could put an end to America’s dependence on foreign oil – remains out of reach.

[rockdoc123]

I have seen it said many times that the Green River Shale formation never matured into liquid oil and is still kerogen in a rocky matrix because it was never buried deep enough to cook all the way. A) Is that true? B) what about the deeper parts of the formation on the bottom? C) Does anyone produce liquid oil from the formation at all, or is it still a pipe dream? D) Back in the early 1980's it was predicted to be the Next Big Thing with 3 TRILLION barrels of OOIP, is it a forever dream?

It is generally true that for most of the Uinta basin the Green River formation wasn't buried deep enough. That being said the deepest parts of the basin suggests that the base of the Green River reached the onset of early maturation. Having seen a few of the reconstructed burial curves for the basin I suspect that the Green River Fm never spent enough time at the depths where elevated temperature would have started to drive maturation it is after all both time and temperature that are important. Interestingly enough everyone calls it a shale but in fact it isn't in that it lacks fissility that is common in all shales. Instead the oil bearing portion is better described as a marl with a mixture of limestone and dolostone. As you mention a large part of the "shale" is comprised of kerogen but there is also some free hydrocarbon (not a lot) as well as some inert material. Pyrolysis at extreme temperatures (up to 800 C) can convert as much as 70% of the kerogen to hydrocarbon and other products. The problem has been the extreme cost of such heating versus the yield. Back in the mid-eighties the gap between cost and hydrocarbon price was somewhere around $45. In terms of 2016 dollars that would be a little over $100 suggesting there was a huge gap that would need to be closed in terms of costs dropping and prices rising in order for the shale oil or kerogen to be profitable. Obviously it requires some new technology that is cheaper than standard pyrolysis methods and can deal with large volumes.

[Tanada]

I have seen it said many times that the Green River Shale formation never matured into liquid oil and is still kerogen in a rocky matrix because it was never buried deep enough to cook all the way. A) Is that true? B) what about the deeper parts of the formation on the bottom? C) Does anyone produce liquid oil from the formation at all, or is it still a pipe dream? D) Back in the early 1980's it was predicted to be the Next Big Thing with 3 TRILLION barrels of OOIP, is it a forever dream?

It is generally true that for most of the Uinta basin the Green River formation wasn't buried deep enough. That being said the deepest parts of the basin suggests that the base of the Green River reached the onset of early maturation. Having seen a few of the reconstructed burial curves for the basin I suspect that the Green River Fm never spent enough time at the depths where elevated temperature would have started to drive maturation it is after all both time and temperature that are important. Interestingly enough everyone calls it a shale but in fact it isn't in that it lacks fissility that is common in all shales. Instead the oil bearing portion is better described as a marl with a mixture of limestone and dolostone. As you mention a large part of the "shale" is comprised of kerogen but there is also some free hydrocarbon (not a lot) as well as some inert material. Pyrolysis at extreme temperatures (up to 800 C) can convert as much as 70% of the kerogen to hydrocarbon and other products. The problem has been the extreme cost of such heating versus the yield. Back in the mid-eighties the gap between cost and hydrocarbon price was somewhere around $45. In terms of 2016 dollars that would be a little over $100 suggesting there was a huge gap that would need to be closed in terms of costs dropping and prices rising in order for the shale oil or kerogen to be profitable. Obviously it requires some new technology that is cheaper than standard pyrolysis methods and can deal with large volumes.

Thanx for the detailed answer. So if I understand you correctly only a very small fraction of the Green River formation was deep/hot enough for sufficient time to break the Kerogen down into liquids and gasses. The other main point is the heating requirement for the Kerogen is 200-800 C which makes it a much more difficult prospect than say the steam mobilization of deep bitumen sands oil because just heating the 'tar sands' up to 100 C is enough to mobilize the bitumen and permit it to flow to the recovery well via gravity where it can be pumped to the surface.

I suspect that also mean something like the THAI subsurface fire flooding wouldn't work on the 'kerogen marlstone' because first you would have to break up the rock into gravel or fist size rock before the flame front and the gasses being pumped in to feed it could move through the formation.

Would it be possible to use a superheated gas other than steam to heat the formation underground? I know it is speculative, but there is a strict limit to how hot you can make steam before it breaks down chemically. If you heated something like inert Nitrogen gas to 800 C and then blew it through a fractured oil shale formation would that be enough to heat the kerogen and transform it into liquid oil you could extract? I know different gasses have different heat capacity and the capacity of steam is very high because it releases a heck of a lot of energy in the process of condensing back into water. Helium has about 2.6 times the heat capacity of steam, but it is hard to get ahold of in very large quantities and expensive. Hydrogen has the highest heat capacity of a gas but you have issues with it combining chemically with the kerogen and converting it all into light fractions like Methane.

[rockdoc123]

The main difference here is that when trying to extract heavy oil whether it be by THAI or SAGD what you are doing is trying to improve the viscosity of what is already oil. In the case of the "oil Shale" such as Green River you are actually having to create oil from the kerogen. The energy required is, as a consequence much higher. I suspect as long as you are able to replicate the temperature at which you drive off hydrocarbons from kerogen it doesn't matter what the source is. Doing so in-situ (i.e. without mining the shale first) would be problematic given you can't contain the heat in a given area (too many heat sinks). Note that this is a similar problem for SAGD or THAI and there you don't need anywhere near the level of heating. But I'm not an expert in this area, I did work on a number of heavy oil projects over the years but never investigated any of the kerogen shales.

[Subjectivist]

The main difference here is that when trying to extract heavy oil whether it be by THAI or SAGD what you are doing is trying to improve the viscosity of what is already oil. In the case of the "oil Shale" such as Green River you are actually having to create oil from the kerogen. The energy required is, as a consequence much higher. I suspect as long as you are able to replicate the temperature at which you drive off hydrocarbons from kerogen it doesn't matter what the source is. Doing so in-situ (i.e. without mining the shale first) would be problematic given you can't contain the heat in a given area (too many heat sinks). Note that this is a similar problem for SAGD or THAI and there you don't need anywhere near the level of heating. But I'm not an expert in this area, I did work on a number of heavy oil projects over the years but never investigated any of the kerogen shales.

How long and how high of a degree of heating are we talking about? I mean, if the heating is like steam, but you hold it for days would that work? Or does it need to be 500 C for six hours? The other thing is, those Chinese molton salt reactors are supposed to be able to hold those kind of high heats for 18 months or longer, so you could use them to heat your working gas, probably nitrogen because it is abundant and cheap. Of course by now there are a stack of if this works and this works and then this works, which seems less likely at every step up the ladder.

[rockdoc123]

How long and how high of a degree of heating are we talking about? I mean, if the heating is like steam, but you hold it for days would that work? Or does it need to be 500 C for six hours?

I wasn't very good at explaining myself. The methods they have used so far is to crush up the kerogen shale and heat it in a large contained crucible to the point at which chemical reactions occur to drive off the relevant hydrocarbons. Any source of heat would work as long as it was contained and could be maintained at the high levels. The issues with in-situ is that it is impossible to contain the heat for any real length of time without some degradation. The losses to surrounding rocks is immense and given the vagaries of permeability it is difficult to get the steam of hot fluid to go where you want it to and stay there. There have been a number of in situ pilot sites attempted, some reported at SPE conferences. There was a recent conference paper that looked at combustion as a possible in-situ means of extraction

Kar, T et al, 2016. Effective extraction of Green River Oil Shale via combustion. SPE 179610-MS

The authors here indicated that based on their laboratory experiments on relatively small samples.

Combustion can be a promising in-situ oil shale extraction technique, with the optimum amount of water (via hydraulic fracturing) and catalysts added.

But this sounds to me not unlike the early work that was done on fire flood techniques and THAI regarding heavy oil recovery neither of which ended up being viable economically

My understanding is the cost to mine the rock is not any different than coal (a calculation based on strip ratio) the issue is with the cost of fuel to create heat and the issue that a large enough amount has to be heated at any given time in order to generate a volume that would be economic (yield per BTU or some other similar calculation). The thought that nitrogen could be used is interesting as it could lower the costs I would guess. But again not an expert in this area.