The hydrofracking of horizontal wells in shale gas formations presents a threat to aquifers that is qualitatively and quantitatively different than the threats posed by vertically fracked oil wells. The rapid development of this technology has outstripped the ability of most regulatory agencies to effectively deal with the environmental threat to aquifers and surface drinking water over wide areas of the United States where shale gas deposits are found.
1. The horizontal hydrofracking (HHF) of shale strata is not dissimilar from exploding a bomb underground.
The pressures involved and the amount of fluid moved would qualify the hydrofrack as a large, powerful explosion, which has shown to be capable of producing earthquakes in natural faults, such as the tremor measuring 2.8 on the Richter scale on June 2, 2009 at Cleburne, Texas in the epicenter of shale gas production. Previously, no earthquakes had ever been recorded there. The pressures, volumes, and horizontal configuration of the well make it more likely that chemicals and natural gas will pollute aquifers than would a conventional vertical well.
2. Frack Pressures
The fracking pressure in a shale gas well has to be extreme in order to break up the rock – as much as 15,000 pounds per square inch (psi).1 That is equivalent to the water pressure six miles deep in the ocean. By comparison, a thermobaric “air bomb” used in Afghanistan has an explosive pressure of about 500 psi, and it can be heard up to 100 hundred miles away.2 Shale is notoriously hard to frack. And bombs, including at least one nuclear bomb tested in Colorado, have been used in attempts to break it up.3 From a pressure standpoint, the horizontal hydrofracturing of shale is effectively the explosion of a massive pipe bomb underground.
3. Volume of Fracking Fluids
Since the fracked area itself can be quite extensive, the amount of fracking fluids in a shale gas well can exceed a million gallons. That is equivalent to about fifty (50) residential swimming pools; or by weight, approximately 2,500 automobiles. Based on the volume of fluids moved, the fracking of a shale formation amounts to a massive water bomb. Since the lighter fracking chemicals separate out of the frack water, they are more likely to show up as pollutants in aquifers and ground water. This explains their presence in water wells near active shale gas wells.
4. Migration of Gas into Aquifers
The fact that the fracked area of a well is horizontal and of a considerable length simply increases the odds that some vertically and inclined faulting or localized faulting will be encountered (Figure 1). Since shale has relatively low permeability, the well has to be fracked repeatedly in
order for it to continue to produce. Such multiple fracks simply increase the odds that the gas will either go out of zone via faulting, or out of the well bore via faulty casing. In either case, area ground water and aquifers are vulnerable to be polluted, first, by escaped natural gas, and subsequently, by fracking fluids, including toxic chemicals such as benzene, which will separate out of the frack water over time.
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