How do fossil fuels form and how are they extracted?

How do fossil fuels form and how are they extracted?

Oil‘Black Gold’

• 1. What is oil? •2. How does it form?

• 3. What rocksand structures is itfound in?

• 5. What are the problems with itsextraction and use?

• 4. How can geologists find it?

Crude Oil

Hydrocarbon

• 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 carbonmolecules.

H

C

C

C

C

C CC C1. What is oil?

Petroleum

Petra = Rock Oleum = Oil

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)?

en.wikipedia.org/wiki/Image:Ceratium_hirundinella.jpg

• Most oil and gas starts life as microscopic organisms called plankton that live in the ocean.

Plant plankton Animal plankton

10,

000

of t

hese

bug

sw

ould

fit

on a

pin

head

!

2. How does it form (Oil Formation)

• Remains of microscopic plankton in ocean (Float on surface)

• When die sink in water column and accumulate on sea bed

• 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)

Petroleum

PlanktonDie,Sink &Accumulateon SF

Low energy& anoxicenvironment

Anaerobicbacteriaformsaropel

Burial toform finegrained shales.

Further burial = compaction & inc. T.

Maturationto formkerogen

Further maturation

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

Add labels to a sketch to explain whysandstone is such a good reservoir?

Porous: Large pores and higher porosity means more storage space

Highly Permeable: pores must be interconnected to allow migration and then extraction of oil and gas

Well rounded increases porosity

Poorly cemented: Allows interconnectivity of grainsWell sorted: > Porosity

3. What rocks is it found in?Cap Rocks

‘’Need to be impermeable to stop the further migration of theoil 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 ofhydrocarbons’

• 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:

Explanation of why oil collected:

Explanation of why oil collected:

A) Anticline B) Fault

C) Salt Dome D) Unconformity

Task:1. Label the source rock, cap rock and reservoir rock of each.2. Shade in colour the oil and gas3. Explain why the oil has collected in this type of trap

Explanation of why oil collected:

Task:1. Label the source rock, cap rock and reservoir rocks2. 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

Drill here!

Salt dome Found

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

Coal

• 1. What is coal? •2. How does it form?

• 3. What rocksand structures is itfound associated with?

• 5. What are the problems with itsextraction and use?

• 4. How can geologists find it?

How is coal formed?1. Plant matter accumulates at the bottom of a body of water in a swamp.

How is coal formed?

http://www.minepermits.ky.gov/NR/rdonlyres/06BC5AA8-EF18-4762-8585-C517CD57E71B/0/Ed_coal_formation.jpg

2. The plant matter is protected from oxidisation and biodegradation by mud or acidic water (anoxic conditions)

How is coal formed?

http://www.minepermits.ky.gov/NR/rdonlyres/06BC5AA8-EF18-4762-8585-C517CD57E71B/0/Ed_coal_formation.jpg

3. Over time, the plant matter is changed by heat and pressure to create a solid material.

How is coal formed?

http://www.minepermits.ky.gov/NR/rdonlyres/06BC5AA8-EF18-4762-8585-C517CD57E71B/0/Ed_coal_formation.jpg

4. The coal grade increases from peat to lignite to bituminous coal to anthracite with time, increased pressure and temperature.

Coal Rank ComparisonIncreasing 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)

Features of the formation of fossil fuels that make exploitation difficult

Slow processes of fm.

Deep burrial

Young oil is viscous Young lignite has low energy density.

Widely dispersed and often inaccessible areas e.g. coal in

Antarctica.

Explanation of why oil collected:

Explanation of why oil collected:

Explanation of why oil collected:

A) Anticline B) Fault

C) Salt Dome D) Unconformity

Task:1. Label the source rock, cap rock and reservoir rock of each.2. Shade in / colour in the oil and gas3. Explain why the oil has collected in this type of trap

Explanation of why oil collected:

Task:1. Label the source rock, cap rock and reservoir rocks2. Shade in colour 3 locations where may accumulate oil and gas

Petroleum

• Remains of microscopic plankton in ocean (Float on surface)

• When die sink in water column and accumulate on sea bed

• 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)

Options

Oil Formation