What is fracking?

As we exhaust more easily accessible natural gas reserves,
countries across the globe are increasingly turning to shale
gas. But how do you release gas that’s imprisoned in millions
of tiny pores inside shale rock, deep beneath Earth’s surface? The
answer is hydraulic fracturing, or fracking.
Fracking involves drilling deep into rock and pumping a highly
pressured jet of water, sand and chemicals down the wellbore. This
forces a network of tiny cracks to open up and spread through the
impermeable rock, allowing pockets of gas within the rock to seep out.
The main ingredient that makes up fracking fluid is water. Since
water is incompressible, it can pass on the extreme pressures needed
from the pump to the shale rock over 2,000 metres (6,560 feet) below.
Sand or ceramic beads act as ‘proppants’, holding the cracks open after
the pressure drops and while the gas is collected.
Finally, a cocktail of different chemicals is added. Their uses range
from averting micro-organism growth to preventing corrosion
of metal pipes, maintaining fluid viscosity and reducing
friction during extraction.
Hydraulic fracturing was first used in the 1940s,
but is far more efficient today. The advent of
horizontal drilling in the Nineties, for instance,
made wells far more productive, making the
operation economically viable.
While fracking has allowed governments to
unlock previously unreachable and abundant
shale gas resources, it has sparked concerns
among some geologists and conservationists. A
fracking well uses millions of litres of water per frack, putting pressure on local water resources. Around half of the
fracking fluid remains in the rock and, although much deeper than
groundwater, some fear it could, over time, contaminate drinking
supplies. The fluid recovered at the surface also needs to be disposed
of safely. Finally, geologists must ensure fracking sites are far away
from fault lines since they can increase the likelihood of earthquakes
and tremors in at-risk areas.