If drilling for shale gas in the Karoo gets the go-ahead, the industry will become a “serious competitor” for water, one of SA’s leading earth scientists has warned.
According to a media release sent out on behalf of his consultancy, Dr Chris Hartnady told the Shale Southern Africa conference in Cape Town on Monday that shale gas production would require as much as four times the current annual groundwater use in all three of the Karoo areas that have been allocated to Shell for exploration.
Hartnady, an expert in structural geology and tectonics, said players needed to be aware of the environmental impacts and geophysical risks of shale gas production, and should evaluate the full energy cost and other economic considerations of the proposed gas exploitation in the Karoo.
Hartnady quoted estimates that the gas exploration phase in three areas of the Karoo would require between 48 000m3 and 216 000m3 of water, using 24 exploratory wells.
But should these test wells prove that the gas deposits were viable, actual production would require about 10 000 wells, he said, pointing out that the Marcellus and Barnett shale gas areas in the US, with similar reserves, required 12 000 and 14 000 wells.
This meant the gas production phase in the Karoo would require an additional 5 000m3 to 20 000m3 of water per well, with overall water demand in the range of 50-200 million cubic metres.
He pointed out that groundwater contamination was possible.
Hartnady also warned of the dangers of seismic events like earthquakes.
Referring to a 5.6 magnitude earthquake measured in Oklahoma last year, he said this US shale gas-producing state had previously had about 30 small earthquakes a year but since 2010/11, this had soared to more than 1 000 annually.
He believed this was because of the “dramatic increase” in the disposal of waste-water brines from unconventional oil and shale-gas production.
“The 2011 ‘hydroseismic’ events in Oklahoma and Ohio bear important lessons for the Karoo, especially since significant earthquake activity is present.
The earthquake catalogue of SA shows many epicentres within and around the Karoo,” Hartnady warned. - Cape Argus