Karoo fracking… on our watch?
by J le Roux, Treasure Karoo Action Group
Electricity+Control, September 2014 – pages 48 - 50
Enquiries: Visit www.treasurethekaroo.co.za
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Fracking, shortened for ‘hydraulic fracturing’, is a well stimulation technique that is used to enhance oil and gas recovery rates. It was pioneered during the mid 1900s where it was used in vertical oil and gas wells. The technique involves pumping fluids and sand under pressure into rocks to create fractures. The sand (proppant) keeps the fractures open and allows the gas to flow.
As conventional oil and gas reserves in South Africa started to decline, the oil industry had to target deeper source rocks and formations bearing unconventional oil and gas reserves in South Africa. In order to successfully extract these resources, technology had to be developed. The combination of directional drilling (a technology that allows the drill bit to turn sideways to drill horizontally) and hydraulic fracturing gave rise to High Volume Slick Water Horizontal Hydraulic Fracturing (HVSHF), or modern day ‘fracking’.
This novel fracking technique generally requires more water, chemicals and proppant due to the much greater depth and length of the well than conventional wells. HVSHF is also more resource intensive and has a lower energy return on energy investment (EROEI) ratio. The intensity of pressure involved is also different to conventional fracking operations. Due to the nature and geology of unconventional gas resources along with sharp production declines of gas well yields, typically many more wells would need to be drilled to produce the same amount of gas over the same time period than in the case of a conventional gas resource.
The anticipated average statistics for shale gas extraction in South Africa are based on operator statistics and the fact that the target formation is deeper than in the USA. Around 20 000 m3 of water is expected to be used per well per stimulation/frack. There could be up to 32 wells on a well pad. Each well pad is around two hectares in size and pads are spaced 4 000 m – 5 000 m apart. Per well, around 2 000 trucks are expected to be required to transport fluids and equipment onto the drilling location. The wells are expected to be 2 000 m – 5 000 m deep. Each well could be refractured multiple times.
- Fracking involves pumping fluids and sand under pressure into rocks to create fractures.
- The existence of shale gas in South Africa has yet to be proved.
- Several factors must be considered when exploring the possibilities of exploiting potential shale gas reserves.