Weigh in, cranial heavyweights and featherweights! To frack or not to frack, that is the question...
Heh heh heh...you said "taint". :biggrin2:
You are correct. Fracking is here to stay. There's just no doubt about that. It's also clear that there are right ways and wrong ways to go about it. Enforcing the concrete standards is going to be a word that the filters would take out before it hits the page...
I'm very familiar with groundwater here, but not so in Pennsylvania. I looked at a groundwater map for Pennsylvania and everything there looks like rock, sandstone, and some glacial till. The rock and sandstone is going be naturally fractured, so its really not that surprising there was gas intrusion into the groundwater. Out here, in the Eagle Ford, the overlying groundwater aquifer is the Carrizo Wilcox group. Between where they are drilling for oil/gas and the groundwater there is several thousand feet with several confining layers, so its a different situation. My first concern about the fracking here is the sheer volume of water they are using, especially in area that are stressed for water already. But I have seen a couple articles recently where the big guys are really working on recycling water.
GW is correct. In many parts of the country, it's not just been the factors you've mentioned, which are also important, it's also been the concrete (it's not cement; it actually has aggregate and sand in it). In some parts of PA, cameras dropped into the well have shown linings which, for practical purposes, have totally deteriorated. Of course, the cheapest ingredient in the mix is the sand. On the water, in the West, in particular, the industry is going to have to start recycling water, even though it's the cheapest part of the cost equation. The problem is that, if you can drill and tap it for no cost beyond the initial drilling, companies are not going to volunteer a hit on the bottom line, so it'll have to be regulated, even those who oppose regulation just for regulation's sake mostly agree. There's only so much flaming tap water the country will accept before there's pressure on Congress from constituents across the spectrum...I'm very familiar with groundwater here, but not so in Pennsylvania. I looked at a groundwater map for Pennsylvania and everything there looks like rock, sandstone, and some glacial till. The rock and sandstone is going be naturally fractured, so its really not that surprising there was gas intrusion into the groundwater. Out here, in the Eagle Ford, the overlying groundwater aquifer is the Carrizo Wilcox group. Between where they are drilling for oil/gas and the groundwater there is several thousand feet with several confining layers, so its a different situation. My first concern about the fracking here is the sheer volume of water they are using, especially in area that are stressed for water already. But I have seen a couple articles recently where the big guys are really working on recycling water.
On the cementing, its not specifically the cement that would be the problem, its the installation of the well and the placement of the cement. Here, the Texas Railroad Commision is the government body that oversees oil/gas drilling. The Texas Commision on Environmental Quality (our EPA) does not directly police the oil/gas guys. I know the TCEQ specs for water wells by rote, but I don't know the requirements for oil/gas wells. Still, main things that can affect the cementing are reamed hole diameter (which will determine the cement thickness) and straightness of the well and centering of the casing (which will faciliate - or not - the cement placement). I do not know what cement mix they use, but probably Class H, which is mixed for corrosion resistance. If you have a decent cement guy, it should be ok. I did glance at the TRRC website and they have a lists of approved cementers. When you see an approved cementer named Freddy's Well Service, you do kind of wonder, though.
No energy source is 100% safe......
You are correct. Most of the reading I have done is not in technical journals and the terms "cement" and "concrete" are thrown around carelessly. I see from technical reading that the cementing is very complex, so far as additives,etc. are used. Here's a treatment by an engineering firm, with a caution about the length and complexity - LINK. They seem to confirm that the cementing is a tempting shortcut and is the main item, along with the steel casing protecting the water table...
The deep wells usually have to use staged cementing, where the cement is inserted in more than one step. A single continous cementing is easier, where the cement is pumped into the bottom and you know you have finished when the cement appears at grade on the outside of the casing. In either case, once you have cemented, you drill out the cement in the bottom to install the screens (or more casing). The "Halliburton method" is pretty much the genesis of what everyone does today.
I think the engineering report said that, where convenient, they use sea water, NaCl, because the salinity is pretty uniform around most of the world...
