Appalachian Basin

Duke Rebuke: Study Finds Methane in Pa. Water Wells Prior to Drilling

In Pennsylvania, there are currently no standards in place to ensure properly drilled water wells for residents without access to public water systems. This means that any person can drill a water well to any depth without any restrictions for proper casing, which would protect not only that well, but other wells in the vicinity. Because of this, water wells in Pennsylvania tend to have a multitude of problems, mostly with bacteria. But a new study shows that methane is also an issue – even where no natural gas development is occurring.

Researchers Fred Baldassare from Echelon Applied Geochemistry Consulting, Mark McCaffrey of Weatherford Laboratories, and John Harper from the U.S. Geological Survey recently conducted an analysis of groundwater in northeastern Pennsylvania. They looked at more than 2,300 samples from 234 natural gas wells during mud gas logging, and 67 private groundwater supplies prior to natural gas development occurring nearby in a five county area.

We have talked about historic methane in Pennsylvania’s water supplies many times (here and here), including stories from residents in Franklin Township that recall family parlor tricks like lighting the kitchen faucet on fire and toilets blowing up from methane in the 1980s. Even without a study, it’s no secret that water wells have had issues with methane for a long time. In the case of Franklin Township, the issue goes all of the way back to the 1700s.

In recent years, the debate over the type of methane found in water wells has focused on two categories of the gas: biogenic and thermogenic.  This generic description has confused many Pennsylvania residents about the source of the methane in their water, as well as some Duke University researchers.

The common misconception is that of the two types of gas found in water wells, biogenic gas (or microbial gas from shallow formations) is typically pre-existing, whereas thermogenic gas (or gas from deeper depths like the Marcellus) is the result of natural gas development.

However, as this new study shows, fingerprinting and isotopic signatures show that much of the thermogenic gas may have been there for long periods of time — prior to any natural gas development. As the Harrisburg Patriot-News reports:

The study says: “When future isotope data show a stray gas in this area to be thermogenic, that finding cannot be the sole basis for alleging that the stray gas was caused by oil or gas-well drilling.”

As expected, many of the wells tested in the study had biogenic gas in their chemical makeup, but an astounding number had thermogenic gas as well.  In fact, 88 percent of the 67 water wells tested had some presence of thermogenic gas, and none of those sampled showed the presence of Marcellus gas. More from the Patriot-News:

“Alleged incidents of stray gas migration require investigations at the site-specific level and evaluation and synthesis of multiple data types to determine the source of the stray gas.”

“The real revelation,” said Fred Baldassare, one of the study’s authors, “is that gases that look just like the Marcellus also occur in formations above the Marcellus – in the Hamilton group, Tully limestone and the Geneseo shale.”

However, the testing at the drilling sites indicated that a component of that older Marcellus type gas – “a little bit of that gas mixed with early thermogenic gas” – is present in the stratigraphy associated with the aquifer system.

“In some areas,” the study says, “deeper thermogenic gases have migrated over geologic time and mixed with shallower thermogenic gases in the shallower strata.”

Baldassare said, “We were surprised by seeing post-mature gas up in the shallow system – I was almost in disbelief, thought we were getting noise when the first results came in – but we kept seeing it over and over again.”

Methane migration is not a new issue, but our understanding of why or how it occurs in private water supplies in rural Pennsylvania is something residents and researchers continue to gain more insight on.

Researchers from Duke University last year found thermogenic methane in northeastern Pennsylvania water wells, and used that to suggest Marcellus Shale development was the culprit. Despite findings from the U.S. Geological Survey that suggested the situation was much more complex, the media had a field day with the Duke team’s findings.

But as Fred Baldassare told the Patriot-News, with respect to automatically linking thermogenic methane to gas drilling problems, “our data shows that’s not the case at all.”

Check out the following video from the Marcellus Shale Coalition to learn even more about methane in Pennsylvania.


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