Hydraulic fracturing is used to increase the rate at which substances such as petroleum or natural gas can be recovered from subterranean natural reservoirs.- Wikipedia.
From 1940s a parallel activity with less environmental impact is being carried out to extract mainly natural gases ( Methane) from these fragmented and separated gas and oil wells called shale gas and oil reserves.
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Though the discovery of shale gas and drilling of shale wells has brought immediate prosperity to the local communities by way of increased taxes and revenues for infrastructure development and so on, the damages it causes in the long run also needs to be studied. The main concerns raised by the public against fracking are
1. use of water to fracture the rocks, 70 to 140 billion gallons every year (500-600 billion litres of water) . This could lead to water being converted for non-human activities.
2. Contamination of ground water resources, leading to future generations taking the brunt of the health issues
3. while oil reservoirs are concentrated, the shale wells are small, shallow and more distributed resulting in large areas getting polluted and made barren
4. the possibility of tectonic activities that can result after the crust has been fractured at many places leading to instability.
5. The presence of proppants in the shale wells drilled, can be a lasting environmental threat over many years due to the chemicals and surfactants in the proppants
Most of the shale wells produce gases and some oil too, the gross impact on the environment is lot less than created by oil wells. In the short run the impact on the environment may not be severe but we are yet to fully understand its impact of the environment in the long run.
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