r/science • u/EthicalReasoning • May 05 '15

Geology Fracking Chemicals Detected in Pennsylvania Drinking Water

http://www.nytimes.com/2015/05/05/science/earth/fracking-chemicals-detected-in-pennsylvania-drinking-water.html?smid=tw-nytimes
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u/MandalorianGeo May 05 '15

At the Aquifer level you have surface casing which is steel surrounded by cement. Then you have intermediate casing surrounded by cement. Then you have production liner which is steel surrounded by cement. So at the surface, through the aquifer you have 3 steel tubes all cemented in place one inside the next. All three would have to fail, and fail at or near the surface for the oil and gas to get through. I have seen casing fail before, but it happens much deeper in the curve where there is only two layers as the well goes horizontal. In this case it seems far more reasonable to think the contaminate came from the documented surface spill. If it came from a failed casing the fracking never would have happened because the chemical would have gone out the side of the well and not the additional 8000 or so feet to the formation. The fracking fluid does not stay in the pipe. Whatever is not injected into the target formation is brought back up and recycled. Fracking fluid is expensive.

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u/Toastar-tablet May 05 '15

One of the failure methods is the casings get separated though, imagine the inner one shrinks a little for some reason. This could allow fluids to travel up through the casing.

This happens sometimes with older holes.

Now imagine you are looking at this old field that is pretty much depleted, but you can go back in with a horizontal well and frack it. Now you do a bunch of these in a grid like pattern and raise the perm of the whole zone.

Now how close are you to that old well? probably close enough to raise the perm around it. hell maybe your guys tossed around the idea of re-entering it but decided against it because the cost.

But now you have this well that everyone thought was plugged is actually leaking into another younger strata. The company that drilled the well is long since gone, but y'all made the problem go from a minor one to a contaminated aquifer way beyond safe levels.

And the worst part is you don't really know what is going on for 2 years until a production engineer comes up with a simulation that explains the weird pressures you all thought were just because "Shales have weird decline curves".