November 28, 2011

Asking the wrong questions about groundwater and gas

Unlike other more plausible sections of the geology chapter of the draft SGEIS on shale gas drilling (4.2MB PDF), I knew that the last section - 4.7, Naturally-Occurring Methane in NYS - was broken from the first time I read it.

What made that so clear, when I'm not a geologist?

They go way, way, way out of their way to avoid asking the basic question this section of the SGEIS needs to answer:

Does gas drilling increase the risk of contaminating groundwater supplies with methane?

The draft SGEIS refuses to go anywhere near that question. The one time it gets kind of sort of close, it cherrypicks data to paint a bright smiley face on a study that concludes the opposite of what the SGEIS claims.

What we do get is four pages of excuses for other possible reasons methane might appear in groundwater. "Methane in groundwater? Quick, look over there!"

The presence of naturally-occurring methane in ground seeps and water wells is well documented throughout New York State. Naturally-occurring methane can be attributed to swampy areas or where bedrock and unconsolidated aquifers overlie Devonian-age shales or other gas-bearing formations....

Often landowners are not aware of the presence of methane in their well. Methane is a colorless, odorless gas, and is generally considered non-toxic but there could be an explosive hazard if gas is present in significant volumes and the water well is not properly vented....

[Examples of non-drilling-related methane...] (4-37)

My favorite section is what I call the "Excuses" paragraph:

Methane contamination of groundwater is often mistakenly attributed to or blamed on natural gas well drilling and hydraulic fracturing. There are a number of other, more common, reasons that well water can display sudden changes in quality and quantity. Seasonal variations in recharge, stress on the aquifer from usage demand, and mechanical failures are some factors that could lead to degradation of well water. (4-37)

Yes, all of those things can happen. There was a fire during well-drilling in Freeville last year, and I knew people in Lansing who were frustrated by several methane strikes - not enough to heat the house - while trying to put in a new water well. It doesn't seem like anyone figured out what happened to wells near the intersection of Ellis Hollow, Turkey Hill, and Quarry roads, a few years ago, either.

The hard question, though, isn't whether there's gas in the ground. We know that there is. The question is whether that gas can move because of drilling, and not just when the drillers can't be bothered to cement their well casings properly.

There's one sentence that gave me a brief moment of hope:

Drilling and construction activities may have an adverse impact on groundwater resources. (4-38)

The rest of that paragraph, though, wanders away into things the DEC might be able to control, avoiding questions about what they might not be able to control.

The migration of methane can contaminate well water supplies if well construction practices designed to prevent gas migration are not adhered to. (4-38)

Chapter 6 talks about the importance of well casing construction - which is important but only part of the story. It concludes with language ("perceived to be related") that dismisses other kinds of concerns:

Section 4.7 of this document explains how the natural occurrence of shallow methane in New York can affect water wells, which needs to be considered when evaluating complaints of methane migration that are perceived to be related to natural gas development. (6-42)

Chapter 7 at least requires "Baseline water quality testing of private wells within a specified distance of the proposed well" (7-42), and the distance turns out to 1,000 feet, or 2,000 feet if there are no wells closer. That's a small start, though given that the SGEIS has put so much effort into claiming methane contamination is natural and unrelated, I can't help wondering how much data it would take for the state to consider taking a second look.

Returning to section 4.7, the SGEIS notes that:

In April 2011 researchers from Duke University (Duke) released a report on the occurrence of methane contamination of drinking water associated with Marcellus and Utica Shale gas development. (4-38)

Rather than discuss the actual conclusions of that study of wells in New York and Pennsylvania, the DEC homes in on one tiny piece of potential good news in the study. If you look at only the nine wells they tested in Otsego County, there were minimal amounts of methane. Of course, only one of those wells was within a kilometer of a gas well, and that one well had less methane than the rest of the wells. Never mind that the main criticism of the Duke study seems to be its limited sample size, and that a sample size of one doesn't offer anything statistically.

So what did that study really find? The headline Methane Levels 17 Times Higher in Water Wells Near Hydrofracking Sites gives the story away, but the paper itself makes clear that this isn't just pockets of methane near the surface. Some of it clearly comes from deep down, and bad well casings alone aren't enough of an explanation:

Methane concentrations were detected generally in 51 of 60 drinking-water wells (85%) across the region, regardless of gas industry operations, but concentrations were substantially higher closer to natural-gas wells (Fig. 3). Methane concentrations were 17-times higher on average (19.2 mg CH4 L−1) in shallow wells from active drilling and extraction areas than in wells from nonactive areas... The average methane concentration in shallow groundwater in active drilling areas fell within the defined action level ... for hazard mitigation recommended by the US Office of the Interior (13), and our maximum observed value of 64 mg L−1 is well above this hazard level (Fig. 3). Understanding the origin of this methane, whether it is shallower biogenic or deeper thermogenic gas, is therefore important for identifying the source of contamination in shallow groundwater systems.

The average δ13C-CH4 value in shallow groundwater in active drilling areas was −37 ± 7‰, consistent with a deeper thermogenic methane source. In contrast, groundwater from nonactive areas in the same aquifers had much lower methane concentrations and significantly lower δ13C-CH4 values (average of −54± 11‰; P < 0.0001; Fig. 4 and Table 1). Both our δ13C-CH4 data and δ2H-CH4 data (see Fig. S2) are consistent with a deeper thermogenic methane source at the active sites and a more biogenic or mixed methane source for the lower-concentration samples from nonactive sites).

Because ethane and propane are generally not coproduced during microbial methanogenesis, the presence of higher-chain hydrocarbons at relatively low methane-to-ethane ratios (less than approximately 100) is often used as another indicator of deeper thermogenic gas (14, 15). Ethane and other higher-chain hydrocarbons were detected in only 3 of 34 drinking-water wells from nonactive drilling sites. In contrast, ethane was detected in 21 of 26 drinking-water wells in active drilling sites. Additionally, propane and butane were detected (>0.001 mol %) in eight and two well samples, respectively, from active drilling areas but in no wells from nonactive areas. (page 2)

So how does that deeper gas climb through the formations?

There are at least three possible mechanisms for fluid migration into the shallow drinking-water aquifers that could help explain the increased methane concentrations we observed near gas wells (Fig. 3). The first is physical displacement of gas-rich deep solutions from the target formation. Given the lithostatic and hydrostatic pressures for 1-2 km of overlying geological strata, and our results that appear to rule out the rapid movement of deep brines to near the surface, we believe that this mechanism is unlikely.

A second mechanism is leaky gas-well casings (e.g., refs. 27 and 28). Such leaks could occur at hundreds of meters underground, with methane passing laterally and vertically through fracture systems.

The third mechanism is that the process of hydraulic fracturing generates new fractures or enlarges existing ones above the target shale formation, increasing the connectivity of the fracture system. The reduced pressure following the fracturing activities could release methane in solution, leading to methane exsolving rapidly from solution (29), allowing methane gas to potentially migrate upward through the fracture system.

Methane migration through the 1- to 2-km-thick geological formations that overlie the Marcellus and Utica shales is less likely as a mechanism for methane contamination than leaky well casings, but might be possible due to both the extensive fracture systems reported for these formations and the many older, uncased wells drilled and abandoned over the last century and a half in Pennsylvania and New York....

Several models have been developed to explain the relatively common phenomenon of rapid vertical transport of gases (Rn, CH4, and CO2) from depth to the surface (e.g., ref. 31), including pressure-driven continuous gas-phase flow through dry or water-saturated fractures and density-driven buoyancy of gas microbubbles in aquifers and water-filled fractures (31). More research is needed across this and other regions to determine the mechanism(s) controlling the higher methane concentrations we observed. (page 4, paragraph breaks added)

The good news in the study is that fracking fluids, brine, or other liquids are unlikely to climb up from the Marcellus depths. The bad news is that gases, once freed, may be able to find their way up through a series of fractures I described here earlier.

The Duke researchers seem to recognize that this isn't the end of the story - the article concludes, even beyond the quote above, with a call for more study. Unlike the DEC's draft SGEIS, though they've found something that looks painfully significant, they don't argue that the science here is settled. Their final call to arms is a political one - a call for open data:

We believe that systematic and independent data on groundwater quality, including dissolved-gas concentrations and isotopic compositions, should be collected before drilling operations begin in a region, as is already done in some states. Ideally, these data should be made available for public analysis, recognizing the privacy concerns that accompany this issue. Such baseline data would improve environmental safety, scientific knowledge, and public confidence. Similarly, long-term monitoring of groundwater and surface methane emissions during and after extraction would clarify the extent of problems and help identify the mechanisms behind them. (page 5)

Right now, it looks to me like the DEC's main purpose in this section of the report is to protect drillers. At least in theory, that doesn't resemble the DEC's mission. Whoever wrote this section misread the DEC's assignment, or worse.

Update: This discussion of back and forth between industry supporters and the Duke researchers is interesting, but has no effect on the DEC's grotesque misuse of the data.

Posted by simon at November 28, 2011 6:10 PM in , ,
Note on photos


Rachel Dickinson said:

Well done, Simon!