Fracking facts: pros, cons and issues

It has long been known that shales contain oil and gas but it is only within the last decade that the development of two technologies has made the extraction of gas from shale an economic proposition:


•The first of these is the ability to drill horizontally from an initial deep vertical bore.
•The second is the development of a process called ‘hydraulic fracturing’ .

Hydraulic fracturing is the use of a fluid made up of around 90% water carrying a load of sands, chemicals and sometimes diesel oil and forcing it into shales under high pressure, causing them to fracture and release the gas they contain.

This is the process from whose name the brute industrial tag of ‘fracking’ has been hacked.

To extract shale gas, you drill one or two miles down into the shale band, and then turn the drill head to bore horizontally for up to the same distance. This obviously increases the exposure of available shale to the well. A series of explosive charges in a perforated pipe are then detonated in the stretch designated for fracking, starting the fissuring of the rock for the hydrofracturing that then follows – directed into the new cracks, forcing them more widely apart and extending them.

Shale is hard and pretty impermeable so breaking it up in this way is the only means of releasing the gas it contains.

The gas then flows along the bore and escapes upwards to the well head.

The chemicals that are part of the water borne material injected into the rock include benzene – a known carcinogen that destroys bacteria that might otherwise clog up the fissures created in the rock.

Areas of gas carrying shales are known in the industry as ‘shale plays’ – as opposed to ‘shale explorations’. The difference between the two is that the risk of ‘shale plays’ not containing extractable gas is lower.

CONTINUED:  http://forargyll.com/2011/09/fracking-facts-pros-cons-and-issues/