Advances in technology appear to have made the extraction of shale gas commercially viable in the UK. Shale gas is seen by some as a way of bridging the gap between fossil fuels and low carbon energy.
The gas held within shale beds is accessed through a technique called hydraulic fracturing or "fracking". This process involves drilling a borehole vertically for about 2km which is lined with a steel and concrete casing. Horizontal drilling then stretches the well along the gas baring shale layer and explosive charges are used to perforate the casing here. A mixture of water, sand and chemicals is pumped down through the borehole at high pressure. This mixture is forced through the perforations in the casing, causing the shale outside to fracture and so release the gas.
What does the process involve?
A commercial scale shale gas operation will require a number of well-pads, each around 2 hectares in size, where the pipes are brought to the surface. Each well-pad can contain up to 10 wells and well-pads may be spaced about 1 km apart. Estimates of the likely number of wells in Sussex vary widely. The typical lifespan of a well is 20 years, but fracking may need to be repeated at intervals to maintain production levels.
Estimates of the amount of fresh water needed per frack vary widely, but the average seems to be approximately 8 million litres. About a third of the 'waste' water, containing treatments, sands and other chemicals is returned to the surface and requires safe disposal. The remainder stays underground within the rock. Naturally occurring pollutants such as NORMS (Naturally Occurring Radioactive Materials) are likely to be displaced during the process.
Many concerns have been raised about environmental risks associated with the fracking process. The Trust considers that the most significant local issues for biodiversity are:
- The impact of the footprint of the physical development e.g. buildings, parking areas, waste water storage tanks and well-heads
- The impact from flaring off of gasses and light pollution
- The impact of the transport footprint on the landscape, wildlife sites and noteworthy habitats and species
- The safe disposal of waste
- The use and management of water resources
- The climate change implications
For more information on the potential environmental risks of fracking please read the Trust's position statement and find out more here: