Oil and
Gashttp://upload.wikimedia.org/wikipedia/commons/c/ce/Oil_well.jpghttp://en.wikipedia.org/wiki/Image:Moscow_traffic_congestion.JPGNASAen.wikipedia.org/wiki/Image:Oil_platform.jpgen.wikipedia.org/wiki/Image:Ceratium_hirundinella.jpg
*Presenter notes: Oil and Gas are natural resources of enormous
economic importance. Together they provide about 60% of all the
energy used by society today. They provide fuel for transport and
are vital for heating, lighting and cooking. In addition they are
used in the manufacture of synthetic fabrics, plastics,
fertilizers, detergent as well as for many other purposes. In
short, it is hard to imagine how our society could function without
oil and gas.
Additional background notes for the presenter: It would be
useful if the presenter brought along some rock samples as props.
These could include an organic rich mudstone (black shale) to
illustrate a source rock such as the Kimmeridge Clay (see slide
11), an impermeable rock to illustrate the cap such as halite (see
slide 13) and a porous sandstone to illustrate a reservoir rock
such as the Penrith Sandstone (see slide 13-14).*Presenter notes:
In this talk we will examine oil and gas from three angles.
In the first part we will think about the biological and
geological processes responsible for the formation of oil and gas.
In Practical Exercise 1 we investigate the rate at which oil and
gas deposits form and consider the meaning of non-renewable versus
renewable energy.
In the second part, we will look at the way geologists explore
for new oil and gas deposits and consider the how oil and gas get
from the well to the marketplace. In Practical Exercise 2, we will
have a chance to explore for oil and gas fields ourselves in the
Prospector Game.
In the third part, we will examine the political importance of
oil and gas. Specifically we will look at which countries control
production, consider global supply and demand, and think about the
likely future of oil and gas in our society.*Questions for
discussion: What is oil and gas? Where does it come from?
Presenter notes: As we begin to think about the origin of oil
and gas, a basic question we need to answer is what exactly are oil
and gas? Oil and gas are complicated mixtures of different
hydrocarbons. A hydrocarbon is a large organic molecule. As the
name suggests it is composed of hydrogen atoms attached to a
backbone, or chain, of carbon atoms. Short chain hydrocarbons like
methane are gases. Medium chain hydrocarbons like paraffin are
liquids. Long chain hydrocarbons like bitumen are solids. When
crude oil is extracted from the earth it may be a mixture of
hydrocarbons in solid, liquid and gas states.*
Presenter notes: It may come as a surprise but most of the
worlds oil and gas is made up of the fossil remains of microscopic
marine plants and animals. Thats why oil and gas are often referred
to as a fossil fuel. One of the most important group of plankton
involved in the formation of oil and gas are single-celled marine
plants called dinoflagellates, though many types of animal plankton
are also important. Some oil and gas may have also originated from
the remains of land plants, but we will not discuss these types of
deposits in this talk.*Presenter notes: In certain parts of the
worlds oceans, plankton occurs in enormous quantities, or blooms.
Exactly where those plankton blooms occur is controlled by ocean
currents. The richest sites are where cold, nutrient rich waters
rise to the surface from the deepest parts of the ocean. The
nutrients found in these upwelling zones feed plankton and allow
them to reproduce quickly. A single litre of seawater may contain
several million dinoflagellates. Where these plankton occurs in
high numbers they may turn the water red. This phenomenon is known
as red tide.*Presenter notes: When plankton dies it slowly settles
to the sea bed where it forms an organic mush. Usually there are
lots of animals living on the sea floor that feed on this material.
One important group is the polychaete worms. These are
detritivores, which means they eat the dead and decay remains of
other organisms*Presenter notes: However, under certain conditions
there may be very little oxygen on the sea floor. This may be
because the ocean is deep and stagnant and oxygen has not been
mixed down from the surface waters. No animal life can survive
where the sea bed is completely lacking oxygen. Without animals to
eat the dead plankton, the organic mush builds up on the sea bed.
Where ocean sediment contains more than 5% organic mush it
eventually forms a rock known as a Black Shale. The black colour
comes from the dark organic matter that it contains. As we will
see, Black Shale is what makes oil and gas.*Presenter notes: As
more sediment accumulates on top, layers of Black Shale become
buried more and more deeply in the Earths crust. As they do so,
they slowly heat up because of the geothermal gradient. With
progressive heating the organic material in the plankton undergoes
chemical and physical changes. It gradually breaks down into
smaller and smaller hydrocarbons. At temperatures of around 30C, a
solid, sticky bitumen is produced. Around 90C liquid oil is formed.
As temperatures reach 150C, natural gases like methane are given
off. A Black Shale that is heated and gives off oil and gas is
known in the oil industry as a Source Rock.
Background notes: This is natural chemical cracking of the
hydrocarbons where the initially large molecules are broken into
progressively smaller molecules by the increase in temperature much
the same as long chain hydrocarbons can be cracked commercially.
*Presenter notes: The hot oil and gas does not stay in the Source
Rock for long. As the hydrocarbons are less dense than the water in
the source rocks that surround them, they gradually migrate upwards
through the rock in much the same way that the less dense air
bubbles of an underwater diver will rise through water. The
migrating oil and gas may travel up through the spaces between the
sand grains that make up the rock (called pores) or they may find
their way up through cracks, fissures, and faults in the overlying
rocks. As we will see when we look at oil exploration, eventually
oil and gas get trapped in pockets of rock known as
reservoirs.*Presenter notes: Most of the Source Rocks that gave
rise to our present day oil and gas fields were formed in the
middle of the Mesozoic Era about 150 million years ago. At that
time conditions were just right to build up huge thicknesses of
Black Shale. On the one hand, the oceans were unusually warm,
promoting vast plankton blooms. On the other hand, oxygen was
mostly absent on the ocean floors so most of the plankton that
settled on the bottom accumulated. There were no animals around to
eat it up. The map on the left hand side shows what the Earth
looked like 150 million years ago. The red circles show where the
worlds main oil deposits were formed in warm, shallow, deoxygenated
seas.*Presenter notes: A real example of a Black Shale that has
formed a major oil deposit is the Jurassic Kimmeridge Clay. This is
a 150 million year old shale that contains up to 50% organic
matter. It stretches from Dorset in southern England right across
to Norway. It was this Black Shale which was the main Source Rock
for the North Sea oil and gas province. *Presenter notes: The
Kimmeridge Clay of Dorset took an enormous amount of geological
time to form (perhaps as long as 5-10 million years). After that it
took still many more million years before it was sufficiently
cooked to start producing oil and gas. In the first Practical
Exercise we will try and calculate exactly how much time it takes
to form a watt of energy from oil and gas by biological and
geological processes. We will compare our figures with other energy
sources like solar power and think about the meaning of
Non-renewable and Renewable Energy.
*Presenter notes: In the first practical we thought about the
immense amount of time it takes to form oil and gas. Consequently,
it is an extremely valuable resource and huge amounts of money are
poured into trying to locate new oil and gas fields. In this
section, we will investigate how reservoirs of oil and gas are
discovered and how it eventually reaches the marketplace.
As we have already seen, once produced, oil and gas migrates out
of its Source Rock and accumulates in overlying rocks. Some rocks
like sandstone or limestone are permeable to oil and gas, which
means that they can pass freely through them. Other rocks like clay
or salt are impermeable, which means they block the upward passage
of hydrocarbons.
One of the most common ways that oil and gas becomes trapped in
pockets in the rock is where it is rises into a structural dome
capped by impermeable rocks. The cap rocks prevent the oil and gas
escaping upwards. The buoyancy of the less dense hydrocarbons in
the pore waters prevent them from sinking back down. This is an
example of an Oil Trap.
Optional exercise: An excellent additional exercise to get
students thinking further about how Oil Traps form go to
http://earthlearningidea.com, click on Earth-related Activities,
and look under the Resource and Environment section.*Presenter
notes: The permeable rocks than contain oil and gas within the oil
trap are known as the Reservoir Rock. Reservoir rocks have lots of
interconnected holes called pores. These allow them to absorb the
oil and gas like a sponge. The picture on the left shows a good
reservoir rock with lots of pore spaces filled with water shown in
blue. As we advance the slide, we see the pores gradually fill with
oil. This rock can soak up a large amount of oil.*Presenter notes:
Weve just established what kind of structures tend to trap oil and
gas in the Earths crust, but how do we locate potential traps
underground? One technique is to use seismic surveys. In this
technique, a Vibrator Truck fires shock waves into the ground. The
shock waves pass through some rock layers and bounce off others. By
recording how long it takes for the shock waves to arrive back at
the surface allows geologist to build a picture of the internal
structure of the rocks beneath their feet. An example of a seismic
survey is shown in the diagram on the right. It reveals a large
underground dome in the rocks. As we have seen domes often trap oil
and gas so this may be a potential site to drill.
Background notes: The term seismic is derived from the Greek for
shake (think earthquakes!)*Presenter notes: A potential oil trap is
called a Prospect. Once a prospect has been identified, the next
stage is to drill a hole into the top of the trap to see if it
contains oil and gas. It is incredibly expensive to a drill hole.
On an offshore rig is may cost $10,000 for every metre drilled. So
if you are going to drill a hole 5000 metres underground its going
to cost you 20 million pounds/ 25 million dollars! Consequently
geologists have to be pretty confident that they going to hit oil.
If they drill too many dry holes they will soon lose their
jobs!*Presenter: If the geologist is lucky, he or she will strike
oil and gas. A hole which contains oil and gas is called a well.
The oil and gas is under considerable pressure in the Earths crust
so once a well is drilled into the reservoir rock, the oil and gas
rapidly rises to the surface. However, as more and more oil and gas
comes out of the well, eventually the pressure drops and flow slows
down.
To get the remainder of the oil and gas out of the reservoir
rock, a second hole is drilled adjacent to the first. Hot water or
steam are pumped down the hole and this forces the oil and gas
still trapped in the rock up the original well. This technique is
known as enhanced recovery.*Presenter notes: Once the oil and gas
has been extracted from the ground, it must be safely transported
from the well to the refinery where it will be processed. Oil is
usually transported from the well to the refinery using pipelines.
These may stretch over land or be laid over the sea bed. A
spectacular example of an oil pipeline is the Trans-Alaskan
pipeline which carries oil and gas for 1300 kilometres across
Arctic permafrost. Another way that oil and gas are transported is
by means of massive oil tankers. These gigantic vessels can carry
up to half a million tonnes of oil. *Presenter notes: At the
refinery, the crude oil, which also contains a lot of gas, is
processed. This involves separating out all the different
hydrocarbons in the crude oil. To do this, the crude oil is heated
in a furnace and then passed through a cooling tower. The method
relies on the fact that different hydrocarbons have different
boiling points. Consequently the heavy hydrocarbons like bitumen
with high boiling points accumulate at the bottom of the cooling
tower. Light hydrocarbons like paraffin with low boiling points
accumulate near the top of the top. This process is known as
fractional distillation. The different hydrocarbons have different
uses. For example, bitumen is used to surface roads while paraffin
is mostly used as aviation fuel. *Presenter notes: People have been
using oil and gas for four thousand years. However, the modern era
of oil and gas exploration and production didnt begin until 1846.
That year, Abraham Gesner, a geologist based in New Brunswick,
Canada figured out how to distill paraffin from crude oil. This
made crude oil far more useful and triggered a global boom is
exploration and production. California became an early centre of
oil prospecting and was famous for its gushers. These were
pressurized oil reservoirs, which when drilled, spurted massive
fountains of oil into the air!*Presenter notes: Following a hundred
and fifty years of oil and gas exploration, most geologists think
that we have now found most of the oil that lies in the Earths
crust. The map shows the major oil and gas provinces of the world.
Dark green provinces are the biggest field and the light green
provinces are smaller. Only two regions of the planet have not yet
been fully explored for oil and gas. These are the Arctic and
Antarctica. These cold inhospitable environments make oil
exploration and production too costly. However, as the climate of
these regions changes with global warming and as technology
advances, it may be only matter of time before these fields become
ripe for exploitation. At present exploration in Antarctica is
prohibited by the political Antarctic Treaty. Note: an oil province
is the assemblage of numerous fields within a region; an oil field
is a single accumulation.
Question: Can you think of any reasons, why we should not
exploit oil provinces in the Arctic and Antarctica (even if the
technology were to make it possible and cost-effective)?*Presenter
notes: Now you know about the geological factors that control the
distribution of oil and gas in the Earth, you should be able to
locate oil and gas fields yourself! In Practical Exercise 2, you
will try your hand as an exploration geologist as you play the
Prospector Game. Will you make your fortune or will you get the
sack?
*Presenter notes: So far we have thought about how oil and gas
forms, how geologists find it, and how it is brought to the
marketplace. However, this talk would not be complete without a
look at the politics of oil and why it is so significant. That will
be the topic of the final part of this presentation.
As we mentioned at the start, its hard to imagine how modern
society could function without oil and gas. The biggest single use
of oil and gas is a fuel source. Fuel accounts for about 84% of all
oil and gas consumed. Without oil and gas there would be no cars or
planes and we would be more limited in the way we heat and light
our homes, or cook meals. We cant simply turn to electricity
instead because much of our electricity is produced by power
stations that burn oil and gas!
Question for discussion: Apart from a fuel source, what other
uses does oil and gas have?*Presenter notes: Less well known is the
fact that many household items are also made from oil and/or gas.
Did you know that CDs and DVDs, plastic containers, fertilizers,
pesticides, food additives, synthetic clothing, dyes, and
detergents, all to a large degree, contain byproducts of oil and
gas? In fact 16% of all oil and gas is used to make these and many
other products. As a society we totally rely on oil and gas in our
day-to-day lives.*Presenter notes: So, if oil and gas is of such
importance to society, its important to understand who controls its
production. Today, oil production is governed by three major groups
who together produce 75% of the global supply.
The single largest oil producer is the Organization of Petroleum
Exporting Countries, also known as OPEC. Together these 13
countries produce 36% of the worlds oil, or to put it another way,
some 32 million barrels of oil per day (based 2008 figures). The
largest producers in OPEC are four Arab states, namely Saudi
Arabia, Iran, the United Arab Emirates, and Kuwait, although
Venezuela is also a major producer.*Presenter notes: The other two
major producers are the Organization for Economic Co-operation and
Development, also known as OECD, and the states of the former
Soviet Union.
OECD produces 24% of the worlds oil supply, or 21 million
barrels per day. Within OCED, the biggest single producer is the
USA, but other major players include Mexico, Canada, and the UK.
The states of the former Soviet Union supply a further 15% of the
global production.*Presenter notes: In 2007, the global consumption
of oil was about 80 million barrels per days. Every year, this rate
of consumption is rising by about 1.2 million barrels per day. The
single largest consumers of oil is the USA, which sucks up 24% of
the total oil produced. However, the oil consumption of the USA is
slightly declining at the moment. The annual growth in global oil
consumption is mostly being driven by China, who shows big
year-on-year increases in usage.
Geologists believe that the nations of OPEC and OECD cannot
indefinitely increase the rate of oil production. At most,
production rate can only be increased by another 2.5 million
barrels per day. Consequently there may be a big squeeze in the
availability of oil in the coming decade.*Presenter notes: This
global squeeze in oil supply was predicted more than fifty years
ago by a geologist called M. K. Hubbert. In 1956, Hubbert predicted
that the world would reach peak rates of oil supply about the Year
2000. Thereafter oil would become increasingly scarce. This would
trigger an energy crisis, result in widespread power blackouts, and
see the cost of fuel rise astronomically. Hubberts idea of Peak Oil
is controversial but supported by some scientists and
politicians.*Presenter notes: One piece of evidence that suggests
that Hubbert may have been right is rising cost of oil. For the
past few years, oil prices have rapidly increased. In 1999, oil was
priced at less than $10 per barrel but since then the price has
sky-rocketed to $139 per barrel by June 2008 and will probably go
even higher. Is this due to a squeeze in availability, as Hubbert
suggested, or are other political or economic factors to
blame?*Presenter notes: Whatever the cause of the current rises in
oil prices, there is good reason to believe we have not yet reached
Hubberts era of peak oil production. One of the effects of higher
prices is that oil deposits that were once considered uneconomic to
exploit have now become viable.
The largest of the these unconventional oil deposits is the
Athabasca tar sands of Albert, Canada. Amazingly this deposit
contains over half the worlds oil reserves, equal to 1.75 trillion
barrels. The oil is mixed together with sand near the surface and
is extracted by opencast mining using giant dumper trucks! However,
it is very expensive to extract oil from tar sands, so if this
source is used extensively, prices are unlikely to fall.
Nevertheless, the Athabasca tar sands together with other
probable large oilfields in the Arctic and Antarctica will probably
stave of oil shortages for several decades to come.*Presenter
notes: Although there probably wont be an Oil Crisis in the
short-term, there are other good reasons for investing in
alternative sources of power now. The main reason is that oil and
gas are a major source of greenhouse gases like carbon dioxide and
methane. Together they contribute to global warming which is one of
the biggest headaches for modern society to deal with. Oil and gas
produce far fewer greenhouse gases than coal per watt of energy
produced. However, renewable energy sources like solar, wind and
nuclear power are far less polluting. That said, renewable energy
has not yet been sufficiently developed to replace fossil fuels as
the worlds energy source. In particular it is difficult to develop
renewable energy as a source of fuel for transportation. As a
result, we will have to live with the environmental consequences of
oil and gas for centuries to come unless we change our habits
quickly.
Question for discussion after the practical: Apart from fossil
fuels what other sources of energy are available? Why are these
sources not used more widely?
*Presenter notes: In this talk we have discussed how oil and gas
are formed, how geologists find and produce it, and why it is of
such political importance in modern society. I hope you have
learned just how much we rely on this precious non-renewable
resource and how pressing is the need to swiftly find alternative
sources of energy. Oil and gas has been fundamental for the growth
of society for the past fifty years, but in a further fifty years
we will need to have weaned ourselves off our thirst for oil and
gas.