44% of wells leaking at Australian gas field
By Will Cottrell
A study of a gas field in Queensland, Australia has found 44% of gas wells leaking (see p4 of this pdf). The report adds to a growing body of evidence suggesting that gas drilling inevitably leads to water contamination as gas escapes from boreholes.
The study, conducted in the Tara, Queensland field examined 56 of the field’s wells. 26 were found to have leaks.
Tara is a Coal Bed Methane (CBM) gas field (it’s called Coal Seam Gas in Australia). CBM uses horizontal hydraulic fracturing but in layers of coal, rather than shale rock which lie deeper underground. Australian CBM operator Dart Energy has just applied to drill a third well at its site near Airth, Scotland.
Australia is not the only country to suffer leaking wells. A Canadian study found more than 17600 oil and gas wells leaking nationwide. Watson and Bachu (Society of Petroleum Engineers SPE 106817 – 2009) surveyed 352,000 oil and gas wells and found 5% of wells had gas or oil outside the central borehole. (15% in the Alberta test area were leakers)
In 2003 Gas Service Company Slumberger found 60% of offshore gas wells leaking within 30 years of being drilled.
In 1992 the US EPA estimated that of 1.2 million abandoned oil and gas wells in the US, 200,000 were leaking, a 16.7% failure rate.