as a fuel and the development of new technology, it may now be economically viable to extract the gas from the Northwest Carboniferous Basin. Natural gas is composed mainly of methane, CH4. It is a clean-burning fuel and is more environmentally friendly than coal or oil. It can be used both for domestic heating and cooking and for electricity generation. It would be beneficial for Ireland to develop natural gas as an indigenous energy source. Unfortunately, there are technical problems, as this gas will not be easy to extract. Natural gas was formed, millions of years ago, in a marine environment. It arose from the decomposition of the remains of millions of tiny plants and animals that died and sank to the sea bed and became trapped in sediments of clay or sand. In conventional gas fields, natural gas may accumulate in pockets, when it is trapped under a dome shaped layer of impermeable rock. Vertical drilling through the overlying rock will readily release the gas. The Lough Allen Natural Gas Field is an unconventional carboniferous gas basin, formed 350 million years ago. At that time, Ireland was part of a greater land mass, see Science Spin 37, and the Lough Allen field was once contiguous with the Appalachian Basin in the USA, where natural gas is being extracted at present. It consists of tight gas sandstone reservoirs, which are less porous and permeable than in conventional fields, making it difficult to extract the gas. However, in recent years, a new method has been developed to extract natural gas from tight gas and shale gas reservoirs. This method uses horizontal drilling, combined with hydraulic fracturing, colloqually known as ‘fracking’. A vertical bore is first drilled to the required depth, then several horizontal drills are
made. Then liquid is pumped in to force apart the layers of rock strata, making it easier to release the gas. Already, concerns have been expressed about the use of this method of extraction in Ireland and local activists in the Sligo/Leitrim region are opposing the exploration. It is feared that disturbing the geological strata in this way could cause seismic tremors. There are also fears that substances in the fracking fluids could leach into the ground water and cause contamination. There is even a mobile cinema travelling through the region, showing a documentary film, made in America, called ‘Gaslands’, which aims to show the risks associated with hydraulic fracturing. The plot of a recent episode of CSI dealt with the same theme and showed dramatic images of water from a tap apparently catching fire and a huge explosion erupting from a well, because there was so much flammable gas entrained in it. No doubt this makes for good TV and cinema viewing, but it also serves to scare people and make them worried about any attempt to extract natural gas from such unconventional fields. If it turns out that there is a commercially viable gas prospect. in the Northwest of `Ireland, both the companies and the licencing authorities would do well to take time to explain to the public, in precise detail, exactly how it will be extracted. Modern fracking fluids consist mainly of water, but they usually contain certain additives, most of which are substances already in common use and should pose no great risk to the environment. In any case, it is likely that the gas reservoirs would be at a much lower level than the water table and there would be a natural impermeable barrier above the gas field, preventing contamination of ground water. But the public need to be reassured about this.
Additives in use at present in fracking fluids in the USA include the following: potassium chloride to reduce friction, hydrochloric acid to remove drilling mud damage, gluteraldehyde to prevent microorganisms from fouling the fractures and dimethyl formamide (DMF) which is an oxygen scavenger, to prevent corrosion of the pipes. These substances are all in common use. Potassium chloride is a component of argicultural fertilizers, and is present in our own body fluids, hydrochloric acid is produced with the gastric juices in the human stomach, glutaralhedyde is used in the healthcare industry for sterilization and DMF is used in the pharmaceutical industry. However, to reassure the public, Tamboran has recently announced that it will not use any additives in the fracking water, other than sand, which helps to keep the gas-bearing strata apart after the water has seeped away, thus facilitating the escape of the natural gas. Without the usual additives, the extraction of the gas will be more costly, because higher pressures will have to be used. This is a price the company is willing to pay, in order to reassure the public. Whatever decisions are made with regard to developing our natural resorces, they should be based on sound scientific findings, not on uninformed scaremongering. Having said that, there should certainly be a public debate on the issue, because, left to themselves, planning authorities don’t always get it right. Margaret Franklin is a chemist and former Senior Lecturer at Athlone Institute of Technology. Margaret is co-author of the book, Colour, what we see and the science of sight.
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