5.D.1. Non-Conventional Hydrocarbons: Tar Sands and Oil Shale

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來自 University of Illinois at Urbana-Champaign 的課程

Planet Earth...and You!

25 個評分

University of Illinois at Urbana-Champaign

Planet Earth...and You!

25 個評分

Earthquakes, volcanoes, mountain building, ice ages, landslides, floods, life evolution, plate motions—all of these phenomena have interacted over the vast expanses of deep time to sculpt the dynamic planet that we live on today. Planet Earth presents an overview of several aspects of our home, from a geological perspective. We begin with earthquakes—what they are, what causes them, what effects they have, and what we can do about them. We will emphasize that plate tectonics—the grand unifying theory of geology—explains how the map of our planet's surface has changed radically over geologic time, and why present-day geologic activity—including a variety of devastating natural disasters such as earthquakes—occur where they do. We consider volcanoes, types of eruptions, and typical rocks found there. Finally, we will delve into the processes that produce the energy and mineral resources that modern society depends on, to help understand the context of the environment and sustainability challenges that we will face in the future.

從本節課中

Week 5: Energy Resources

The video lectures for this week cover various aspects of energy usage by modern civilization, especially our utilization of fossil fuels. The Week 5 Lab sends you on a Google Earth tour of energy-producing sites around the world, places where both conventional and alternative forms of energy are being generated. The Week 5 Assignment gives you a chance to survey your own personal use of energy – where does it come from and how much do you use – and then to share the information with others in the class. During the Week 5 Discussion, you will consider the implications of how society uses the energy of fossil fuels and the implications for the local environment and global climate.

5.D.1. Non-Conventional Hydrocarbons: Tar Sands and Oil Shale5:12

5.D.2. Natural Gas6:40

5.D.3. Obtaining Shale Gas: Hydrofracturing7:19

5.D.4. Challenges Associated with Obtaining Shale Gas11:10

與講師見面

Dr. Stephen Marshak
Professor and Director of the School of Earth, Society, and Environment
Department of Geology
Dr. Eileen Herrstrom
Lecturer
Geology

[MUSIC]

Everything we've been talking about so

far pertains to conventional hydrocarbon reserves.

That means the kinds of reserves in which an oil company can drill a hole and

pump the fluid out of the ground.

That's because the fluid has relatively low viscosity and

because the rock in which it's stored has relatively high permeability.

But there are vast amounts of hydrocarbons on this planet that are not

in conventional reserves, that are either in rocks that lack permeability,

so they can't be pumped easily.

Or occur in a form that is so viscous that it's not possible for

the oil to flow, even if the rock had permeability.

These kinds of hydrocarbons are called nonconventional reserves.

And in this section, we're going to focus on recent efforts

to try to extract hydrocarbons from nonconventional reserves.

And I'll say from the start that it's clear that this is a controversial

process.

There are many people that think it's the future of energy use in the near term.

There are many people that think that it's extremely damaging to the environment and

should be avoided at all costs.

I'm going to try to avoid the issue for better or worse.

I simply want to try to convey what these are and

how the process of extraction works.

Hopefully to provide you with enough understanding so

that you'll be able to make your own decision whether it's good or bad.

Let's start with the three main kinds of non conventional reserves.

They are tar sand, oil shale and shale gas.

Now I'm going to look at each of these in sequence, but

we're only going to talk very briefly about the first two.

It's the third one that's been the subject of so

much excitement in the exploration industry of the past five to ten years,

and so we'll focus more of our time on that.

So what is tar sand?

Well basically, there are certain places in the world,

where large amounts of oil migrated into a reservoir rock.

But once in the reservoir rock, which is very shallow in the crust,

they were attacked by microorganisms and degraded.

In this process,

they underwent reactions that lead to the production of very long molecules.

In other words, tar like molecules.

As a consequence, these hydrocarbons cannot flow very easily.

And even though they occur in a highly permeable host rock, sand or

sandstone, they can't be extracted simply by drilling into them and pumping.

So there are basically two ways the tar sands are extracted.

One is by strip mining them.

Basically, some of the deposits occur so close to the surface,

that it's possible to dig them up with a shovel, load it into giant trucks, and

carry it out of the ground to where they can be processed.

Now the processing requires a lot of energy.

Specifically, they're put into a furnace, where they are warmed up to a high enough

temperature that they become low enough in viscosity that they can flow.

And at that point, they are extracted and separated from the sand

where they can then be cracked to form more conventional types of fuels.

Another way of getting tar sands out of the ground,

is by lowering the viscosity in situ, in other words, in place.

To do that, the oil companies can sink steam pipes into the ground,

inject steam, warm up the hydrocarbons, and then pump them out of another well.

In either case, you can imagine that it takes a huge amount of energy

to get energy out of tar sands,

which is one reason why they remain somewhat controversial.

That said, there are vast reserves of tar sands in places like western Canada and

in Venezuela.

One other point about tar sands is that to refine them

leaves behind a residue called pet coke,

which is a very carbon-rich material which itself can be burned.

But, it is a very high carbon footprint substance to use.

Oil shale is simply a source rock from which the hydrocarbons have not yet

migrated.

Therefore, oil shale contains a lot of hydrocarbons.

Most of it still in the form of kerogen.

In some cases oil shale has such a high percentage of organic material,

that you can actually set it on fire, and it will burn all on it's own.

The problem with oil shale, is that even though the hydrocarbons in it might be

able to flow, if there were free, they are locked into a clay rich rock,

which has such low permeability, that they cannot be pumped from out of ground.

So the challenge in extracting hydrocarbons from oil shale

is similar to the challenge of extracting hydrocarbons from tar sand.

Namely, that the oil shale has to be mined and processed,

or it has to be heated by steam before pumping can take place.

Thus, as is the case with tar sand,

it can take quite a bit of energy to extract energy from oil shale.

[MUSIC]

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