5.C.3. Exploring and Drilling for Oil

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University of Illinois at Urbana-Champaign

Planet Earth...and You!

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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.

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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.C.1. Formation of Hydrocarbons: Oil and Gas7:44

5.C.2. Conventional vs. Non-Conventional Hydrocarbons: Conventional Reserves9:57

5.C.3. Exploring and Drilling for Oil9:02

5.C.4. Transporting and Refining Oil4:52

5.C.5. Where Does Oil Occur, and Why?6:33

Conheça os instrutores

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

So the search for conventional oil

is really a search for these special oil traps

and special conditions.

Now, when did this start happening?

Well, oil has been known for a long time.

In more recent times,

oil was used during the 19th century,

primarily as a lubricant for wagon wheels,

but it was not used as an energy source

because it was very limited in supply.

The only place that people knew where they could get oil from

were what-were localities called natural oil seeps.

These are places where cracks or fractures

tap into an oil reserve underground

so the oil is able to migrate up and bubble out

at the surface of the earth.

You can actually see

some of these natural oil seeps today,

for example, the La Brea Tar Bits

that occur in a park in California

near the city of Los Angeles.

You can go there, look at the ground,

and watch oil actually bubbling out at the surface.

But that was not enough of a supply,

so in the mid 19th century

a group of investors from the eastern United States

decided to see if they could figure out how to drill a well,

like a water well,

only into an oil reserve,

and collect oil in sufficient quantities

to economically produce it and use it

as a-as a heating source or as a lighting source.

One of the reasons there was a lot of demand

and a lot of interest in this

was that the predominant lighting source

at the time was whale oil,

and whales were being hunted to extinction,

so the supply of whale oil was pretty much being overused.

Well, to make a long story short,

in 1859 these investors hired a guy named Edwin Drake,

he drilled a well in Pennsylvania, it struck oil,

and so to speak, the rest is history.

Basically, beginning in 1859

the world began to utilize oil

in vast quantities, and the oil age began.

These days, finding oil reserves

is a much more complicated and expensive process.

All the easy oil has been found.

To find oil reserves today

requires primarily the use of a technique

called seismic reflection profiling.

Specifically, geologists generate a source of energy

that sends artificial earthquakes,

basically vibrations, into the earth.

Those vibrations bounce off the layers of strata underground

come back up to the surface

where they are recorded by small seismographs.

A computer is able to take the data,

and by measuring the travel time

for the energy to go down and come back up,

can produce an artificial image of what's underground.

In effect, it's like an x-ray of the interior of the earth.

This method can be used on land,

typically by using big trucks that have a metal plate

that presses against the surface

and transmit a low-frequency vibration into the earth,

or it can be done out in the ocean

where a boat tows what's called an air gun

that sends a pulse of high-pressure air

into the water

that generates a vibration that passes through the water

into the sediment below

and down into the rock beneath that

and then gets-gets, uh, returns to the surface

and is recorded by seismographs that are towed behind the ship.

The technique is very sophisticated, very complicated.

Now it can be done in three dimensions,

so you can create cubes of information underground.

But basically, as you can see in this simple reflection profile,

the layers of strata show up as different bands,

and-and you can see their shapes

and recognize potential traps underground,

because the process of drilling is so expensive these days,

millions and millions of dollars to drill a single hole,

that oil companies do not want to drill

without being pretty sure

that they're going to strike a significant reserve underground.

What about the process of drilling itself?

Well simplistically it's done as follows.

You put a drill head,

which is composed of metal barbs

or sometimes diamond-studded barbs,

in-onto the surface of the ground,

connect it to a pipe,

and then start rotating that pipe.

The drill head will revolve

and gradually grind its way into the rock below.

Now, you can imagine that this process of grinding rock

generates an awful lot of heat,

so the drill head would melt if it weren't constantly cooled.

And the cooling is done by sending,

what's called drilling mud, a fluid,

down the pipe and out through holes in the drill head.

Not only does that fluid cool the drill head,

but it also flushes the-the cuttings,

the ground-up rock, out of the hole,

and as a consequence

you keep adding new pipe at the top,

revolving it, and it keeps drilling and drilling

deeper and deeper down into the earth.

The drilling mud serves another purpose as well.

You can imagine

that the hydrocarbons that are filling the pore space

in rocks deep down underground are under a lot of pressure.

They're feeling the weight of rock over the top

pushing down on them,

and the weight of all the overlying fluids

in the pore spaces, in the rock above pushing down on them,

so if you were to just drill an open hole

down into those rocks,

they would be under so much pressure

that they would rush out of the hole

and gusher, or vent, out at the earth surface.

We'll see that's- that's not good,

because that's not only losing the hy-hydrocarbons,

but it's contaminating the environment,

and if those hydrocarbons should spark and ignite,

it can create a disastrous fire.

So the advantage of having drilling mud

ins-is that it provides a weight

to hold those pressurized fluids underground.

So drilling mud, which is actually not pure water

it's a mixture of water and clay and iron filings

and other kinds of chemicals and so forth to add weight,

it serves three purposes.

It cools the bit,

it flushes out the cuttings,

and it counters the natural subsurface pressure

of the hydrocarbon reserves.

Once an oil well isf- been drilled,

it's not just an open hole in the ground.

The drillers have to finish or complete the hole,

and what that usually involves is sending down a casing pipe,

steel pipe,

that-that will be the main conduit for the hydrocarbons

to come back up out of the ground.

Typically that pipe is cemented into place

with concrete

so that it's-it's-it's straight and also there's no opening

between the-the rock surrounding it

and the pipe itself,

so that you can't have materials seeping out around the pipe

and coming back out to the surface.

Then at the bottom of the hole,

special charges cause perforations in the pipe

and in the-in the-in the cement and into the surrounding rock

and provide an avenue for the hydrocarbons

at the specific horizon to come into the h-into the casing

and then up the casing pipe

and then out the well at the surface.

This is what casing pipe looks like.

Once the-the process of pipe has been established,

a pump is installed at the surface

and the pump starts just going up and down

and pulling the oil out of the subsurface,

storing it in tanks or putting it into pipelines

or putting it into trucks

where it can be carried to where it's utilized.

Now, in a conventional field,

many wells had to be drilled,

because an individual well can only suck the oil or gas

out of a relatively limited area around it.

So from the air, an oil field may look like a pin cushion

with lots and lots of little platforms.

Now, each of these is not

where the drilling's taking place anymore.

These are simply the platforms where the pumps are installed.

But you can see,

as in this example that we're looking at in Texas,

there are oil wells all over the place.

These days, the search for oil has taken geologists and

taken oil companies off-shore

because the sedimentary rocks that contain oil

are not limited to the land.

Some of the major reserves are in strata

that are now underneath the continental shelf,

submerged beneath the ocean.

To get at this oil,

it's necessary to have an offshore platform.

The shallower water platforms are actually built on towers

that are anchored

in the sediment below the sea surface.

Some of these can go down 1500 feet or so.

But in really deep water,

oil companies now utilize floating platforms

that are sometimes tethered to the ground

or sometimes kept in place by precise controls.

Platforms are immensely expensive.

They may be co-they may cost in excess of a billion dollars

because of the technology involved to build them

and the amount of materials to build them.

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