The Oil Drum

PG here; this is a post from HO's Tech Talk series. This one was originally posted 5 FEB 2006. We encourage you, if you're interested, to look back at the entire extensive series under the tech talk tab up top under the banner.

Often when we talk about different fuels, the fuel itself is considered to be something that can easily be defined. However this is really not always the case, and today I would like to talk a little about types of coal, its content and the product size, and why this can make it a bit difficult to assess EROEI.

For those who wonder what is going on, this is a weekend tech talk, where some underlying aspect of fossil fuel energy is discussed. References to earlier posts are given at the end of this one, and the subjects are usually simplified to get across the basic ideas, within a reasonable amount of space.

Back when my grandfather was mining coal, with a pick and a shovel, he would very carefully separate rock from the coal as he picked lumps out from the solid. The reason for this relates to how he was paid. Before he began to fill a tub with coal, he would place a holder and a token with his mark on it at the bottom of the tub. Thus when it got to the surface, the teller would check that the tub only contained coal, and then would give him credit for the tub. But if the tub contained much stone, from the roof, or from layers of rock within the coal, then the tub would not be counted and my grandfather got no credit for it.

A couple of weeks ago I pointed out that the crude oil that comes out of the ground is not made up of a single hydrocarbon, but rather is a mix of different hydrocarbons that have to be separated. And oils from different parts of the world are formed as different combinations of these. Today I would like to go a little further and talk about distillation curves, and because the world supply is changing to heavier crudes then go on to explain a little bit about cracking.

For those new to the site this is where, on weekends, I often post a small technical talk, explaining some of the aspects of the fossil fuel business, so as to help understanding of some of the topics on the site. There are now two main topic themes developed, those relating to oil, and those to coal. Since this talk relates to oil, at the end I will post the list of topics that relate. It is a very simple explanation, because of space, and those who wish to ask or expound a bit more are invited to do so through the comments.

Some recent posts have dealt with coal production, so for a change I thought I would return to oil, for a couple of techie talks. It seems particularly relevant since the discussion has returned to the Canadian Oil Sands again, and the oil that is coming from them. But before getting there what I wanted to talk about was the differences that exist in what to some folk is just "crude oil," with the assumption that it is all the same, In writing about coal, it was fairly simple to show that the different stages of coal as it changes from peat to anthracite, mean that you get different amounts of energy from it, and it can be extracted with differing amounts of energy. The fact that there is a fair bit of difference in crude oils is not always as easily understood.

This then will be a relatively simplistic look at the different potential hydrocarbons that might make up a crude oil, and how we can get them apart. I'll post next time on how we can break the separated flows into other products. This, then, is a short techie talk in the oil production series, earlier posts in which are given at the end of the post.

Crude oil is made up of a mixture of hydro-carbons, which are the different ways in which carbon and hydrogen can combine, starting with such simple compounds as methane (CH4) and progressing to more complex ones with greater numbers of carbon atoms. Oils from different places have different combinations of the major constituents, for example, this is from Kuwait. Because they are fluids mixed together, it is not very easy to separate out the different valuable parts (known as fractions) by a mechanical means. However if you heat up the crude oil blend, then it will vaporize.

Grin - well Yankee has suggested that we need more information on coal gasification and so, after threatening to do this a couple of times, today, having talked a little about surface gasification I thought I would move to the subject of in-situ gasification of coal. That would allow, if successful, that we would burn the coal in place, underground. This might have the advantages of not requiring the surface plant and impacts that a conventional coal mine would need, and it might also provide some useful way of getting to otherwise unavailable deposits such as those under the North Sea. Most particularly it would remove the need for all the grimy gas works that were dotted over Europe and North America until natural gas came along to clear the air. It is a subject that the Chinese are looking into

The Chinese government has authorized an underground coal-gasification project in Lineng of Shandong Province recently. This is a model project combining in-sit-coal gasification and gas-fired power generation.

, as well as being of interest to the British, the Australians and ourselves, to name but a few.

This is another in the weekend technical talks that pop-up at frequent intervals on this site, It fits in with a series on coal technology that is listed at the end of the post, and more particularly is related to other ways of generating fuel from coal other than just burning it in a boiler to generate steam. As with a number of ideas that are getting more discussion (such as the injection of carbon dioxide back into the ground, and the use of pulverized coal in diesel engines) it is not particularly new, but since it is now getting more attention, the post will attempt, in a relatively simple manner, to explain what it is all about. For those more knowledgeable please do comment, as should those who find the explanation not totally clear.

Part of the problem with coal is that, when it was first grown (as in the peat bogs back when) the region was occasionally inundated with floods, and, as the Hurricanes showed last year, this carried mud and sand into the bog. Over the passage of time, as the bog turned from peat to brown coal, and then into coal itself, these dirt bands turned into sandstone, mudstones and other rocks. The layers are often found inter-layered within a coal seam, either as very thin stringers, or as partings that can separate a single seam into layers that end up several feet apart. The bedding planes and vertical joints (referred to as cleat) provide the permeable paths through the coal, and are often partially filled with additional minerals that deposit out of the water that percolated through the coal at one time. This can also introduce lenses of pyrite and calcite, so that coal is not the simple carbon lump that people often anticipate.

This is another in the short technical posts that show up at weekends, dealing with one aspect or another of fossil fuel production. Given that, as Super G noted the Governor of Montana was on 60 minutes tonight, it seemed like a good time to return to a coal-related theme. A list of related posts will be appended at the end of this one, and relate to the mining of coal, either on the surface or from underground, though it is the surface mining of coal, that currently entices the Montana Governor. It should be noted that the adjacent state of Wyoming produces around 400 million short tons a year of coal, about ten times the current production from Montana.

Following Yankee's story about carbon dioxide injection, it appears that not everyone understands one of the ways in which carbon dioxide will help enhance oil recovery (EOR). I am therefore going to just list some of the previous posts that include carbon dioxide, which was discussed here, and here, not to mention here and here.

Below the fold, however, I am going to repeat, with a little update, the post where I described what carbon dioxide injection can do to an existing oil well, and that itself followed an earlier post. These were pre-cursors to what later became the weekend techie talks, and these really relate to those, and from now on I will include this post in that listing. Since the topic largely relates to oilwell production, the listing this week will be for those sites. For those new to the site, on most weekends (though not next week) I will post a simplified explanation of one aspect of fossil energy extraction. So far we have been covering coal this year, after covering aspects of oil and gas production last year.

Carbon dioxide injection is a current DOE program for enhancing oil recovery from an older oil reservoir that has already produced the bulk of the primary oil that it will yield. Just recently Glencoe have started injection in central Alberta, and though the OGJ article on this is behind their wall, a short quote:

Glencoe Resources Ltd., private Calgary independent, is using the gas to improve recovery of primarily light oil from multiple formations in several depleted oil fields about 100 miles north-northeast of Calgary.

The company hopes to boost the recovery factor to as high as 40% from 10-20%. All of the formations are deeper than 1,300 m.

Glencoe has long-term agreements to purchase CO2 from two industrial plants. It operates about 50 miles of CO2 pipelines and has begun injecting gas from the MEGlobal Canada Inc. plant at Prentiss. A second CO2 separation facility being built near the NOVA Chemicals Corp. petrochemical plant is to go into service in early 2006.

The original post related to cleaning up after elephants*, and was written during the time when I frequently compared Saudi Arabia to a sandwich shop (sorry but no-one every noticed the pun!)

Often when we talk about different fuels, the fuel itself is considered to be something that can easily be defined. However this is really not always the case, and today I would like to talk a little about types of coal, it's content and the product size, and why this can make it a bit difficult to assess EROEI.

For those who wonder what is going on, this is a weekend tech talk, where some underlying aspect of fossil fuel energy is discussed. References to earlier posts are given at the end of this one, and the subjects are usually simplified to get across the basic ideas, within a reasonable amount of space.

Back when my grandfather was mining coal, with a pick and a shovel, he would very carefully separate rock from the coal as he picked lumps out from the solid. The reason for this relates to how he was paid. Before he began to fill a tub with coal, he would place a holder and a token with his mark on it at the bottom of the tub. Thus when it got to the surface, the teller would check that the tub only contained coal, and then would give him credit for the tub. But if the tub contained much stone, from the roof, or from layers of rock within the coal, then the tub would not be counted and my grandfather got no credit for it.

Today I would like to describe the events that take place when a company chooses to surface mine coal from under the earth. Of all aspects of mining this is, perhaps, the most controversial, in part because of the large surface disruption that often occurs during the time that it is happening. This post will try, however, to just describe the process, without using any of the emotive words that usually surround this topic.

For those wondering what this is, on many weekends I post a small technical talk, which tries in a relatively simple way to explain some aspect of fossil energy extraction. I will direct you to earlier talks at the bottom end of this one. For those that are more knowledgeable I recognize that I am often simplifying considerably, however, by knowing some of the basics it may be possible to achieve a better understanding.

This becomes particularly true when one talks about coal mining, since there is often discussion on these pages about the relative investments in energy in a process, relative to the amount of energy recovered. Part of that evaluation involves the nature and structure of coal as it is mined and treated, and I will go into more depth on that subject next time.

It is relevant here, since it is one of the bases of judgment as to how a seam of coal is mined. If you remember, I had suggested that you might think that coal is found as being similar to a layer of cream in a cake. Separated by the layer of rock above, and more rock below, the coal itself is a relatively even thickness of material that can stretch for miles. However you should note the word "relatively" in that description, and look at the rock layers in a road cut the next time that you drive through one. You will see variations in the layer at the top and bottom all along the length. Also the layers do not have to be flat, geological movements may have tilted the seams until they are at angles all the way up to vertical. (The coal is the Urals is often highly angled, as are some of the seams in Washington State).

A week ago I wrote about coal mining, using what is known as "Room and Pillar" techniques, which is the most common method of getting the coal from underground mines in the Untied States. However it can leave rather a large percentage of the coal in the ground, after mining is over. How do we get more of it out?

The answer is known as "Longwall Mining" and that will be the subject of the post today. It is the method that is most commonly used in other countries to mine the coal, but to give you an understanding of how it can work, it might be useful to explain, as I did last week, a little history. This, for those of you who are new to the site, is a Weekend technical talk, where some of the underlying ways in which fossil energy is recovered are described. Earlier posts dealt with oilwell operations, and you can find where to find them at the bottom of this post. We're probably going to wander, via surface mining, in-situ combustion and CTL towards refining as the next few weeks roll by.

This is the start of a new semester and so it is time to begin the weekend Techie talks again. However this time I am going to try creating the occasional picture, rather than just referring to other sites, in the hope that this might be more useful. Some of these will come from 3-D models that I am building to make the illustrations, so if there are some questions or other views that might help, ask and I may be able to generate a different picture.

For the first couple of talks I want to go back and revisit coal mining. Both the Washington Post and the NYT have stories recently about coal mining and the people who work there. I remember once being in a class that was discussing D.H. Lawrence's "Sons and Lovers" and the portrait of mining that it presented. It did not correlate well with my memories of being in a mine, which was often much warmer and drier than it has been described.

And so I thought that, today, I would try and create some simple illustrations of some aspects of what coal mining is all about. I am going to do this in two parts, because there are two distinct ways of mining the coal. One is called Room and Pillar, and that is this week, and the other is Longwall and that will be the next topic.