FRACKING and Shale gas are going to be increasingly in the News from now on. Shale is already present in the Oxford dictionary, but FRACKING is yet to gain reputation to be admitted into the elite club. In any case Fracking has gained popularity and assumed global importance because that is how we mine natural gas from shale deposits. Obama has already declared that for the next 100 years America doesn't have to worry because "we have an abundance of natural gas". It is estimated that by 2040, about 50% of America's natural gas will be from Shale.
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| Shale Gas Mining- Courtsey Wikipedia |
Naturally then one asks what is Shale? It is a slate-like mineral deposit of limestone rich in sulfides and carbonates of iron. Geologists call it Marcellus shale (Utica or Upper Devonian shale also belong to this family). These mineral deposits hold large quantities of natural gas,in their pores and crevices. in other words, natural gas is entrapped in shale rock. It is not easy to pump out the gas. One needs to dig more than a kilometer to reach the shale structure, and then the structure tends to crack horizontally into layers making drilling difficult. Hydraulic fracturing is a specialized technique which uses a pressurized liquid to crack open the rock horizontally. A variety of fracturing liquids and gels to suit the chemistry of the rock type are used. Fracking is an easier and more popular term for hydraulic fracturing. Shale gas mining involves two steps: first step is to drill straight down to reach the shale structure and then drill horizontally, to take advantage of the layered structure of shale. One end of the well is sealed off and water (or any other fluid) is pumped under very high pressure to fracture the rock. This allows the interconnection of crevices spread over a large area. The gas is then mined out.
In the US West Virginia, Pennsylvania, New York, Texas, Arkansas have already highly developed shale plays, (Plays mean fields). These plays collectively " now supplies 385 million cubic metres of gas per day, more than enough to supply half of the gas currently burned in US power plants. And the US Energy Information Administration appears very confident in its Annual Energy Outlook 2014. The dream of cheap and abundant energy could soon come true. But as always there are skeptics. In a recent article in Nature says this could be just a wishful thinking. However US dept. of Energy was quick to respond and allay the misgivings.
Will shale gas remain a pipe dream? Let us wait and watch.
References:
2. The Gas Surge : Science 27 June 2014 (vo.344, Issue 6191, page 1464-1475
3. The Fracking Fallacy - M.Inman, Nature 4 Dec. 2014 (Vol.516, page 28-30)
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