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Shale gas and fracking: methane extracted from rocks
Something is changing in the world’s energy market: shale gas, gas extracted from porous rocks through fracking, plays now the lead role.
The world energy market is in turmoil, or maybe we should say bubbling with energy, and shale gas did break this balance. Break is the fitting word because shale gas is the natural gas extracted through hydraulic fracturing or fracking.
Shale gas is the natural gas – mainly methane – trapped within shale and porous rocks and clays. American engineers realised first the potentialities of this resource. In 2000 shale gas represented 2% of United States natural gas production. By the end of 2012, it topped 40%. Through horizontal drilling and multi-stage hydraulic fracturing techniques, natural gas can be extracted at a low price. Those methods are used both in new wells (at an even lower cost) and in older ones. In a few years, the development of these unconventional resources will increase U.S. energy independence, with consequences in world energy markets due to a drop in energy costs and a change in imports and exports.
Few days ago Obama authorised the export of natural gas extracted through fracking to foreign countries, in particular to Asia. It is considered an unconventional gas because it is trapped within impermeable rocks that must be fractured in order for it to be extracted.
Hydraulic fracturing includes the injection of a pressurised liquid into wellbores. During this process, new artificial micro-fractures are created which are connected to preexisting ones, thus allowing natural gas to escape to the well. In many countries this technique is accused of causing environmental damages including aquifers’ pollution. According to the US Department of Energy’s estimates, shale gas, tight gas and coal-bed methane amount to 60% of the world’s technically recoverable reserves through these new techniques adopted in the United States. Shale gas reserves are estimated to meet the American demand for the next 30 years.
The largest shale gas reserves in the United States are four: Barnett Shale in Texas, where 50% of the total output is produced, Haynesville Shale in Louisiana and Texas, Fayetteville Shale in Arkansas and Macellus Shale in Pennsylvania and in some other nearby States.
Shale gas production in Europe was not as dramatic as in the US for many reasons, including its high population density and greater application of the precautionary principle. Poland and Ukraine are taking affirmative action to use this natural gas, but even France and the UK are developing exploitation plans of this resource. In Germany there is an ongoing heated debate. Yet, the shale gas development is not without negative aspects.
There are four major concerns about hydraulic fracturing: aquifers’ pollution, environmental and landscape impact, earthquake risk, greenhouse effect.
For what concerns water, according to fracking supporters, shale gas reservoirs usually lie well below freshwater aquifers and, the risk that the fluid leaks from the near-surface portion of the well is reduced thanks to the layer of cement protecting aquifers.
As for the environmental and landscape impact, fracking areas are destroyed and devastated: in America those areas are also subject to desertification.
The increase of low-magnitude earthquake activity (less than 3) in many areas of the US, according to many geologists, is probably caused by the 35,000 active fracking wells and the American Senate initiated an investigation on potential seismicity of energy technologies.
Finally, a debate about the shale gas contribution to the greenhouse effect developed because, during the initial phases of the production, part of the extracted gas is released in the atmosphere and methane has a six times greater effect on climate change than CO2. Currently, specific technologies are being developed to limit these emissions, unfortunately, of only 1% of a well’s total production.
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