Headings Hydrocarbons Search Questions 
gcsescience.com 1 gcsescience.com
Coal, Oil and Natural Gas Formation - Fossil Fuels.
Just as coal has formed by the action of heat and
pressure
on the remains of trees and plants on
land over millions of years,
so oil and natural gas have formed by the action of heat and
pressure
on the remains of sea plants and animals over millions
of years.
The remains were buried
in sediments
which excluded the air (kept
out oxygen) and stopped
them decaying.
More sediment buried the remains deeper and
deeper until pressure and heat
eventually turned them into
coal, oil
and natural gas.
They are called fossil fuels because
they are buried underground
(from Latin fossilis - dug
up).
Fossil fuels are a finite resource and non-renewable.
The oil
deposits are formed in porous
rock sediments.
Porous rock has pores in it.
Pores are small
holes (see for example sandstone).
The small holes allow the oil and natural gas
to pass through the rock
and rise until they are stopped by a layer of
non-porous rock.
Non-porous rock (for
example shale)
has no holes,
and acts as a barrier to prevent the
oil and natural
gas rising.
The oil and natural gas become trapped underground.
The oil is called crude
oil (or petroleum, from
Latin - rock
oil),
and has natural gas in it or in a
pocket above it trapped by non-porous
rock.
Drilling through the rock allows the oil
and gas to escape to the
surface.
Natural
gas is mostly methane (CH4).
Crude oil is a mixture of substances
(mostly hydrocarbons).
Headings Hydrocarbons Search Questions
gcsescience.com Contents The Periodic Table Index Quizzes gcsescience.com
Copyright © 2008 Dr. Colin France. All Rights Reserved.