A quick guide to fracking
A quick guide to fracking
What is fracking?
The dramatic
increase in shale
gas production in
the USA between
2007 and 2011
9000
8000
• Fracking is an extraction technique
• Technically the process is called
hydraulic fracturing, but it is
commonly known as ‘fracking’
• The process dates from the late
1940s, but has only been widely
used in the last 10 years or so.
• Fracking is used when gas and oil
are locked tightly in rocks below
the ground, and conventional
techniques cannot extract them.
Billion cubic feet of gas
for crude oil and natural gas.
7000
6000
5000
4000
3000
2000
1000
0
2007
2008
2009
2010
2011
USA
Arkansas
Louisiana
Oklahoma
Pennsylvania
Texas
A quick guide to fracking
Oil and gas geology:
conventional oil
• Conventional oil extraction
involves drilling a well (borehole)
into a reservoir rock (see the
diagram, left).
• Oil and gas are held within the
pore spaces of reservoir rocks
e.g. sandstone.
• Because the pore spaces are
connected, oil and gas will flow
freely up the well under pressure, or
can be pumped out.
A quick guide to fracking
Oil and gas geology: tight oil
• Some oil and gas are found in rocks
(especially shale) in which the pores
are not connected.
• They arereferred to as tight gas (or
shale gas) and tight oil.
• To release them the rock must be
fractured.
• The fracturing creates small cracks
and fissures, allowing the oil and gas
to escape.
• The fracturing process involves high
pressure, forcing the rock to shatter.
A quick guide to fracking
The fracking process differs in two main
ways from conventional oil and gas
drilling:
•
Boreholes are drilled vertically, but
turn horizontally (see diagram) to
follow shale strata (directional
drilling).
•
Water, sand and chemicals are
forced at high pressure down the
borehole and into the shale rock, to
assist the fracturing process.
The chemicals vary, but include
methanol, guar gum, ethylene glycol,
acids and dissolved salts.
Drilling
A quick guide to fracking
Costs and benefits
Fracking is viewed in very different ways
around the world.
• In the USA, fracking has dramatically
increased both oil and gas production
already.
• In the UK, commercial production has
not started but exploration is taking place.
• In France, the process has been banned
due to environmental concerns.
• As is often the case in geography, the
debate boils down to whether the
economic benefits of fracking outweigh
the environmental and social costs.
Oil production in the US
Bakken oilfield 2007–13.
The huge increase is due to
the widespread use of
fracking in North Dakota
A quick guide to fracking
Key concerns
• Fracking has been blamed for creating small earthquakes.
• There are concerns that natural gas (methane) could escape from
wells, increasing air pollution and contributing to global warming.
• A key concern is that fracking liquids could pollute groundwater
supplies, and even release gas into groundwater.
• These environmental issues could have a negative impact on
human health.
• The oil industry claims these impacts are minor, and can be
monitored and minimised.
• Environmental groups contend they are serious and genuine
worries.