“Fracking” error

June 6th, 2011
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In the interest of honest science I need to correct what I wrote last about the propagation of fractures in deep rock formations resulting from hydraulic fracturing. Thanks to friend of the blog Dan P. for this data.

According to Dan’s work and study of the literature, which I find compelling enough to quote, “all things being equal” there is a “natural tendency … for fracs to go upwards (rather) than downwards.” This happens – and now I’m getting technical – because the lateral confining pressure is greater and there is also “a deficiency in driving pressure at the bottom”.  The result is that fractures tend to rise. Got that? Depending on the local stress field, fractures can also propagate downward.

Dan points out that fractures also very commonly are confined to one fairly thin lithologic bed or beds. The reason for this is that fractures will follow the path of least resistance and, when beds above and below are more competent, it is easier for fractures to grow within a bed rather than from bed to bed.

All this said, the over-arching point of my original post should be repeated – hydraulically-induced fractures in deep formations (hundreds to thousands of metres deep) only extend tens of metres form the well-bore. This is the evidence from micro-seismic imaging of the fracture network. The rest of my description also remains unchanged – all evidence points to bad drilling practices by some companies, in the shallow portion of wells, is the cause of the increased methane in groundwater. It has nothing to do with hydraulic fracturing.

So I repeat my conclusion that the anti-hydraulic fracturing crusade is misguided and counter-factual. Countries, like France, who are setting aside a reasonable energy alternative like shale gas due to misplaced fear that their groundwater might be imperilled, are being irresponsible. Governments should be using regulatory “best practices” rather than banning shale gas exploitation.

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By John Weissenberger
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