(Reuters) – Scientists at South Africa’s University of Cape Town on Tuesday called for heightened monitoring of the Karoo Basin after uncovering evidence of a previously unknown fault that could trigger earthquakes in a region the government has earmarked for shale gas exploration.
Scientists at UCT’s Department of Geological Sciences said their findings suggest that geological conditions associated with induced seismicity in other shale gas regions worldwide may also exist beneath parts of the Karoo, a statement said.
Their study examined an “earthquake swarm” near Leeu Gamka, Western Cape province, that began in 2007 in an area previously considered relatively quiet seismically, but which since then has recorded at least 66 earthquakes, including one with a magnitude of 4.8 on the Richter scale.
Lead author Benjamin Whitehead said the study showed critically stressed faults are already present beneath parts of the Karoo.
Earthquakes observed in the Karoo were natural and not caused by hydraulic fracturing, he said, although global experience showed that wastewater injection and shale gas operations can reactivate pre-existing faults under certain conditions.
Whitehead said the findings should not halt shale gas development but rather inform future decisions by helping identify areas where extra precautions may be needed.
South Africa’s Petroleum Agency estimates the Karoo Basin holds around 209 trillion cubic feet (tcf) of technically recoverable shale gas resources, although a 2017 study by geologists at University of Johannesburg said this was probably 13 tcf, the lower end of estimates ranging between 13 tcf and 390 tcf.
A 2011 moratorium suspended new applications for oil and gas reconnaissance permits and exploration rights after environmental groups mounted legal challenges over concerns that fracking could damage the ecologically sensitive Karoo region.
Reporting by Wendell Roelf; editing by Bate Felix and Louise Heavens
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