How do fossil fuels form and how are
they extracted?
• 1. What is oil?
•2. How does it form?
Oil
‘Black Gold’
• 3. What rocks
• 4. How can
• 5. What are the
and structures is it geologists find it? problems with its
found in?
extraction and use?
1. What is oil?
C
C
C
C
C
C
C
C
Hydrocarbon
H
• Oil and gas are made of a mixture of
different hydrocarbons.
• As the name suggests these are
large molecules made up of hydrogen
atoms attached to a chain of carbon
molecules.
Crude Oil
Petra = Rock
Oleum = Oil
Petroleum
Contains:
• Crude Oil (Liquid)
• Natural Gas (Gas)
• Asphalt (Solid)
1. Why it classed as a non
-renewable resource?
2. Why is petroleum
sometimes called a fossil
fuel?
What is oil (origin)?
Animal plankton
10,000 of these bugs
would fit on a pinhead!
Plant plankton
en.wikipedia.org/wiki/Image:Ceratium_hirundinella.jpg
• Most oil and gas starts life as microscopic organisms called
plankton that live in the ocean.
2. How does it form (Oil Formation)
Plankton
Further
maturation
Petroleum
Die,
Sink &
Accumulate
on SF
Maturation
to form
kerogen
• Remains of microscopic plankton in
ocean (Float on surface)
• In a low energy anoxic environment
(prevent breakage and decay)
• Burial, occur to cause fine grained
organic rich source rock e.g. Shales
• Oil maturation to form kerogen then
petroleum (‘Oil Window’ 50-200oC)
Low energy
& anoxic
environment
Anaerobic
bacteria
form
saropel
Further
burial =
compaction
& inc. T.
Burial to
form fine
grained
shales.
• When die sink in water
column and accumulate on
sea bed
• Anaerobic bacteria produce
partial decay to form
organic mud called saropel
• Further burial causes compaction
and increase in temperature with
depth
Source Rocks?
E.g. Kimmeridge Clay, Dorset
• Black organic rich fine grained shales
e.g. Kimmeridge Clay, Dorset
3. What rocks is it found in?
Reservoir Rocks
‘Once formed oil migrates into reservoir rocks where it collects’
• Poorly cemented sandstones are good
reservoir rocks as is chalk and limestone
Poorly cemented: Allows
interconnectivity of grains
Add labels to a
sketch to explain why
sandstone is such a
good reservoir?
Well sorted: > Porosity
Highly Permeable:
pores must be
interconnected to
allow migration and
then extraction of
oil and gas
Well rounded
increases porosity
Porous: Large pores and
higher porosity means
more storage space
3. What rocks is it found in?
Cap Rocks
‘’Need to be impermeable to stop the further migration of the
oil and gas upwards and escaping / seeping out at surface’
Make a list of
potential cap rocks
• Fine grained sedimentary rocks e.g.
Clay, mudstone and Shale!
• Crystalline Sedimentary e.g. Evaporites (Halite)
3. What Structures is it found in?
Oil Traps
‘a trap is needed to allow the accumulation of economic quantities of
hydrocarbons’
• 4 Types:
•
•
•
•
Unconformity
Fault
Salt dome
Anticline
Oil and Gas are
always horizontal
There must always
be a:
•
•
•
•
Source rock
Reservoir rock
Cap rock
Structural
Trap
Sketch these for your notes
Explanation of why
oil collected:
A) Anticline
Explanation of why
oil collected:
C) Salt Dome
B) Fault
D) Unconformity
Task:
1. Label the source rock, cap rock and reservoir rock of each.
2. Shade in colour the oil and gas
3. Explain why the oil has collected in this type of trap
Explanation of why
oil collected:
Explanation of why
oil collected:
Task:
1. Label the source rock, cap rock and reservoir rocks
2. Shade in colour 3 locations where may accumulate oil and gas
UK Oil and Gas field Map
Oil and Gas
Gas Only
4. How can geologists find it?
Seismic Surveys
Salt dome Found
Drill here!
Gravity Surveys
Exploration Drilling
5. What are the problems with its
recovery and use?
Recovery
• Ecological impacts e.g. spills while drilling
• e.g. Gulf of Mexico 2010.
• Explosions and fires on rigs off shore
• Spills during transport
Use
• Unsustainable (finite)
• Pollution (acid rain)
• Releases CO2
• Which causes climate
change
• 1. What is coal?
•2. How does it form?
Coal
• 3. What rocks
• 4. How can
• 5. What are the
and structures is it geologists find it? problems with its
found associated
extraction and use?
with?
How is coal formed?
1. Plant matter accumulates at the bottom of a body
of water in a swamp.
How is coal formed?
2. The plant matter is protected from
oxidisation and biodegradation by mud or
acidic water (anoxic conditions)
http://www.minepermits.ky.gov/NR/rdonlyres/06BC5AA8-EF18-4762-8585-C517CD57E71B/0/Ed_coal_formation.jpg
How is coal formed?
3. Over time, the plant matter is changed by
heat and pressure to create a solid material.
http://www.minepermits.ky.gov/NR/rdonlyres/06BC5AA8-EF18-4762-8585-C517CD57E71B/0/Ed_coal_formation.jpg
How is coal formed?
4. The coal grade increases from peat to
lignite to bituminous coal to anthracite with
time, increased pressure and temperature.
http://www.minepermits.ky.gov/NR/rdonlyres/06BC5AA8-EF18-4762-8585-C517CD57E71B/0/Ed_coal_formation.jpg
Coal Rank Comparison
Increasing Rank
Type of Coal
PEAT
LIGNITE
SUB-BITUMINOUS
BITUMINOUS
ANTHRACITE
Carbon
Content %
15
25
45
56
95
Energy
Content
Mj/Kg
10
30
40
60
65
Which type of coal do you think is the most desirable to mine for the energy
Industry and why?
Which type causes the lowest pollution?
Where are
the British
Coalfields?
Why was the South Wales Coalfield
(Glamorgan) So important?
1. What type of
fold structure has
preserved the Upper
coal measures of
South Swansea?
2. Explain how this
structure allowed
important deposits to
be preserved (use a
sketch)
Deep burrial
Slow processes of fm.
Widely dispersed and
often inaccessible
areas e.g. coal in
Antarctica.
Features of the formation of fossil
fuels that make exploitation difficult
Young oil is viscous
Young lignite has low
energy density.
Explanation of why
oil collected:
A) Anticline
Explanation of why
oil collected:
C) Salt Dome
B) Fault
D) Unconformity
Task:
1. Label the source rock, cap rock and reservoir rock of each.
2. Shade in / colour in the oil and gas
3. Explain why the oil has collected in this type of trap
Explanation of why
oil collected:
Explanation of why
oil collected:
Task:
1. Label the source rock, cap rock and reservoir rocks
2. Shade in colour 3 locations where may accumulate oil and gas
Oil Formation
Petroleum
Options
•
In a low energy anoxic environment (prevent breakage and
decay)
•
Anaerobic bacteria produce partial decay
to form organic mud called saropel
•
Further burial causes compaction and increase in
temperature with depth
•
Burial, occur to cause fine grained organic rich source rock
•
e.g. Shales
•
Oil maturation to form kerogen then petroleum (‘Oil
Window’ 50-200oC)
•
When die sink in water column and
accumulate on sea bed
Remains of microscopic plankton in ocean (Float on
surface)