Water problem for fracking investigated
FRACKING operations at each shale gas well proposed for the Karoo will require a once-off water use of some 24 million litres.
This is the equivalent of 30 days’ supply from a borehole producing 10 litres a second, or the volume needed to irrigate three hectares of lucerne for a year, according to the report by the government’s fracking task team that was adopted by the cabinet recently.
The report notes that water security is a big concern in much of SA and is “particularly acute” in the drier western regions of the country like the Karoo.
It outlines three major problems regarding water use in shale gas exploration and production:
The overall volume of water required, relative to the region’s water resources;
The potential for contamination of these water resources; and
The disposal of “flow-back” (recovered fracking fluid) and “produced water” (salty water mixed with gas) that emerge from the well after fracking.
This will probably require a water-use licence in terms of the National Water Act, the report notes.
It states that brackish water or seawater could be used instead of fresh water, but also notes that the Railroad Commission of Texas, a US fracking regulator, told the task team “very clearly” the use of saline water had not yet been demonstrated.
Also, while seawater could reduce the burden of fracking on fresh water sources, it would introduce the risk of effective- ly sterilising soil through accidental spillages. “It is clear that further research into potential water sources is required.”
Referring to the possible contamination of fresh water, the report notes that most fresh drinking water is extracted from aquifers only a few hundred metres deep, while shale gas would typically be fracked from rock formations lying between 1 500 and 4 000 metres down.
However, intrusions (fractures) of dolerite and kimberlite in the northern part of the western karoo basin do not have uniform characteristics and could act as either conduits for fracking fluids, or as barriers to their flow.
Volumes of flow-back would probably amount to millions of litres but would be a short-term issue, while produced water was a long-term issue.
“Experience in the US suggests that treatment facilities for flow-back and produced water may need to be purpose-built.”