Shale gas

The exploration for shale gas is imminent in the Karoo basin of South Africa. There are concerns that the exploration and production of gas might lead to groundwater contamination in a sensitive area where many communities rely on groundwater. This case study presents data from an abandoned gas exploration bore that was plugged many years ago and from where both gas and water has been observed to be leaking recently.

The possibility of large reserves of shale gas underlying the Karoo and their exploitation has focused attention on the groundwater resources and aquifers of this region. Much is known about the relatively shallow aquifers (<300 m) which supply many local municipalities and farmers with water for domestic, stock and irrigation use (mostly from boreholes <150 m in depth).

The anticipated exploration and exploitation of Shale Gas in the Eastern Cape Karoo through hydraulic fracturing has raised considerable debate regarding the benefits and risks associated with this process for both the Karoo, and the country as a whole. Major concerns include the potential impact of hydraulic fracturing on ecological, environmental and especially scarce water resources. The Eastern Cape Karoo region is a water stressed area and with further climate change it will become increasingly so.

Shale gas in South Africa can be a game changer for the Karoo and South Africa economy but it may have a devastating effect on the environment. The Karoo communities is highly reliable on groundwater for their stock, irrigation and also for domestic use. Knowing the process and the potential impacts of gas-well drilling and fracturing on shallow groundwater systems beforehand different appropriate studies can be done before any hydraulic fracturing can took place in South Africa.

The improvement in hydraulic fracturing techniques resulted in the exploitation of natural gas associated with low-permeability organic-rich shale formations in the United States. South Africa has prospective shale gas resources linked with the marine black shales of the Whitehill Formation found in the Karoo Basin. Plans exist to develop the Karoo shale gas resources to diversify the primary energy mix. However, concerns among stakeholders about groundwater contamination and source of water for hydraulic fracturing remain unresolved.

Groundwater in the South Western Karoo is of critical importance in the overall freshwater supply. However groundwater sustainability is vulnerable to natural as well as anthropogenic influence. Groundwater monitoring scheme are employed to provide the necessary information during decision making situations. Groundwater monitoring thus performs in important role in groundwater management and protection.

Anticipated Shale Gas Development could intensify possible natural hydraulic connectivity between deep groundwater reservoirs and shallow aquifers in the Karoo. This project attempts to test geochemical evidence of natural mixing between old groundwater from deep aquifers and young groundwater from shallow aquifers using selected isotopic signatures in conjunction with borehole yields. Borehole yields were determined using slug tests. All isotopes (δ18O, δ2H, δ13C, 3H and 14C) were analysed in the laboratory of Environmental Isotope Group of iThemba Laboratories in Gauteng.