Tech Talk - The latest Canadian oil spill

Time was that I used to write, on Sundays usually, a Tech Talk over at The Oil Drum where I would try and explain some of the technical issues involved in oil recovery from the ground. Now that the site has effectively gone away, and I have had my couple of moments of frustration trying to explain why it isn’t because of the end of the Peak Oil story (here and here), the need for the occasional technical explanation still exists, and I still enjoy the chance to explain something. So as time permits and the need arises I will continue the practice.

On this occasion the post is seeded by a note from Luis de Sousa (h/t Luis) who noted a story in Mother Jones. That story, in turn, fed from one in the Toronto Star and is about surface contamination of oil, coming from the underlying tar sands and emerging as a watery bitumen mixture over at least four areas in the Cold Lake region of Alberta. The story is difficult to report, since the contamination is centered within the Cold Lake Air Missile Range, where the Canadian military fires and tests live weapons. Unfortunately, as written, it seems to have some technical inconsistencies.

The oil migration was apparently started by underground extraction wells that are being used to extract the oil from the oil sand, without having to dig it up first. There are two main ways of injecting steam through wells down into the oil sands that can produce the oil. The one that is most commonly discussed is the Steam Assisted Gravity Drainage (SAGD) process, but the more commonly one used in the past is often known as “Huff and Puff.” I have described both of these in some detail in an earlier post. In this case the process would appear to be the older one, and as a refresher, here is what I wrote about it a couple of years ago.

Surface mining of oil sand can only progress so far before the gradually deepening seams of the sand become too deep to continue to economically mine them. At the same time the viscosity of the oil is such that it does not flow easily to a conventional type of a well. This is not a new problem for the oil industry, which has had to address issues with the quality of the oil that it finds coming out of a well more than once over the past decades. One of the more easily applicable methods for improving the flow characteristics of the oil is through heating it. (And a quick caveat, the quantities of heat that I am talking about at the moment are significantly different from those that are needed in treating oil shale, and I will come to that topic in a couple or three weeks).

The example of the effect that temperature makes on the ease with which a fluid flows that always first comes to my mind is of a visit to the Nurse’s cabin north of Montreal one winter, a long time ago, when after struggling through waist-high snow, we sat and poured whisky from a bottle left there, as we waited for the wood stove to heat the cabin. When we started the Scotch poured as though it was a heavy syrup.

Viscocity of an oil is something that we usually only think about when we buy the engine oil that we put into the car on odd occasion. Buying the right oil means either looking for the little label that has the right description or reading the manual to get the number. But the oil that we buy for the engine is rated in part on how it behaves at different temperatures. We want the oil in the engine to easily circulate around the parts, and lubricate them from the time that we switch the engine on. But if the engine starts cold, and the oil is too thick, then it may not move easily around the parts, which may run dry for a while and wear more rapidly – which is not good. However if the oil becomes too thin once the engine reaches operating temperature then it doesn’t act as a good lubricant, and again engine wear is increased. And so manufacturers of the oil will adjust the contents, depending where in the country they plan on selling the oil, and what the temperature variations the oil can expect to operate under there. (And this is why oil is sometimes bought with two numbers – as in 10W-30 – the first number relates to the cold start, and the latter the performance at the engine operating temperature. And the higher the number the more viscose the oil is under those conditions.)

A typical oil found up in the oil sands of Alberta is much thicker, and more difficult to flow under normal operating conditions than that used in a car. For the areas of the province that are too deep for surface mining the temperature is not affected much by the changes in surface temperature, but the ground temperature is still low enough that the oil is very viscose, and production from a normal vertical well is usually too slow to justify the expense of putting in a well.

So how can the viscocity be reduced? For a simple example, take an apple, which has fallen in the butter, and you want to clean it off. If you take the apple and put it under a cold stream of water the butter sticks to the apple, but if you raise the water temperature, suddenly the butter melts and runs off the apple. This happens best at about 185 degF, and if you were to turn a pressure washer onto a greasy surface you would find that it works better if the water is also heated above that temperature. (Some pressure washers are sold that way).

Think now, if you will, of little Johnnie (helped of course by Jessica) having raided the orchard and spread butter onto all the apples, gluing them together and filling the kitchen full, right to the ceiling. How do we clean the butter off and get it back without taking all the apples out and cleaning them one by one (which is sort of what they do with the surface mined oil sand up in Canada).

We could just stand in the hall and stick heaters up against the wall of apples, hoping that the heat would melt the butter and work its way back to the ones further into the kitchen. That sort of works, but burns the local apples and doesn't reach all that far. (They have tried setting fires inside oil wells, and we’ll get to that maybe next week). You could fill the kitchen with hot water, but while that washes out some of the butter, a lot of the heat goes into the apples and the water is cold before it reaches the back of the room. And the water doesn't have that much pressure to push the remaining butter off the apples.

What we need is something that will get through the gaps between the apples and keep its heat. So how about steam? So you go and get a steam cleaner (such as you use for carpet cleaning) and blow the steam into the apples. That works but as the butter starts to flow out it clogs the gaps and starts to re-harden except when the steam is right there. So you start to run the steam for a bit, stop and collect the butter that comes out, run the steam for a bit, etc. You can do this in an oil well and it has the exciting technical name of "Huff and Puff" (would I kid you?). To make the steam more effective it is heated to between 150 and 300 deg C. Where the rock is very permeable and the steam can, in time, work its way back through the particles (apples) this can recover a lot of our butter. But you still lose a lot of heat, which is expensive to generate, just in heating the apples.

The NETL shows how the process works, in three steps:
Huff

Soak

Puff - The 3 stages of the process as illustrated by NETL.

The problem is that this is still limited by the length of the borehole through the deposit, and because it is an intermittent process, it doesn’t give a continuous flow of oil.

In the current case at the Primrose Oil Sands project this particular leak came up under a body of water making it more difficult to control, but it was the fourth at the Primrose site, though earlier ones were in the Primrose East development. In their public statement on the issue Canadian Natural stated:

This spring bitumen emulsion was discovered on the surface and based on all the evidence gathered to date, we believe this rise to surface involves mechanical failures of wellbores in the vicinity of the impacted areas. A complete review is ongoing.

The location of the latest leak under a body of water seems a little hard to support that conclusion – though I am not that familiar with the project history.

What I do remember, however, from lectures that I have given on ground freezing when teaching ground control, was the great difficulty one can have in controlling the path of any fluid injected into the ground. I mentioned some of that in a post I wrote on permeability, some time ago. The gas used in the ground freezing is usually liquid nitrogen, and it is injected to freeze the ground around the injection point and along the path that the fluid takes. (In other words the reverse of that used in steam heating of the oil). But it has proved to be a very difficult process to control, because any small fissure in the ground can have a sufficiently lower permeability that the surrounding rock that all the fluid will flow to that channel. This is particularly a problem in the case of the oil sand, because if the steam finds an easy path to the surface (and the fact that this is the fourth instance suggests that the particular oil formation may be prone to such fissures) then as the steam migrates it heats and softens the bitumen so that it will flow with the steam, widening the channel and, over time, making the situation worse, if steam continues to be injected.

Fortunately, with the “Huff and Puff” steam is only injected for a short while, before injection stops and the oil recovery phase begins. Yet, in the latest case, that was sufficient to bring over 4,000 bbl of bitumen to the surface. It seems likely that the process will need to be modified to give better control to the steam paths, and the oil migration. This can probably be achieved by switching to the SAGD process, which is planned in later work at the project. In the interim they might want to steer away from using the technique in regions where the oil grade is higher, and there is the potential for the sand to outcrop or come close to the surface without a confining cap rock.

Conventional 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 on the subject 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). More recently, there is currently a House bill in Committee governing oil shale development.

What's the big deal? Drill a hole down there and it flows it - isn't that how you get oil out of the ground? Well not in this case. As I said last time 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 - sorry I can’t find these on the internet) 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, bring it to the surface, and then get the oil out of it.

That’s what they do in Canada with the oil sands, and these beds are thicker. In fact 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 had, for a while, been 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 last week.

What is needed is assurance that shale oil production will face a stable economic environment in which it can share in the spectrum of raw materials for our future energy needs.

. 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 goes down as oil content goes up to a value of about 13,000 psi with an oil grade of 30 gal/ton, at which point it stabilizes even as the grade continues to increase. This means that the openings for mining can be quite large, as they need to be to achieve the tonnages planned. And there are ways to make them larger.

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 underground 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, and the roof is held up by the newly placed columns. However, when you mine and mill the 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, which might otherwise be forgot.
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.