Casing cracks, not fracking, blamed for gas in water wells

A new analysis of stray methane in water wells identifies nearby gas wells as the likely culprit, but not the hydraulic fracturing of shale deep in the ground below.

The study of water supplies in high-gas areas near drilling in Pennsylvania and Texas points to problems in the cement casings and spaces around pipes as the probable cause in the rare cases that gas gets into water supplies.

“We see this as good news for the long term,” said lead author Tom Darrah, an Ohio State University scientist whose research was published Monday in the Proceedings of the Academy of Natural Sciences. “If we can improve well-integrity that can eliminate most of the environmental concerns.”

A separate study released by the Department of Energy's National Energy Technology Laboratory found no evidence of “upward migration” of gas or fluids from the Marcellus shale beneath Greene County.

Watchdogs, regulators and an industry group said the discovery of gas in water wells and its source does not surprise them. Methane naturally occurs in water wells and the state has no standards for their construction. In most of the 113 water wells examined in Pennsylvania and 20 in Texas, Darrah's team determined natural sources of gas.

Using a novel analysis of noble gases such as helium and neon in that gas — combined with traditional isotopic analysis — the researchers determined in eight cases the gas likely came from faulty well walls.

“We've been saying that for many years. If we do have a well incident, it is typically an issue of having good cement integrity,” said Fred Baldassare, the owner of Echelon Applied Geoscience Consulting in Murrysville who spent 25 years with the state Department of Environmental Protection.

The DEP last month released details of cases in which it confirmed that gas drilling had a negative impact on well water. The drilling of 20,000 wells over the past decade resulted in 243 cases, a little more than 100 of which involved gas migration.

Darrah said he wants to see more emphasis on better well casing construction. Drillers and regulators said they're working on that.

“We recognized early on that migration was the No. 1 safety concern,” said Scott Perry, deputy secretary for the DEP's Office of Oil and Gas Management

DEP in 2011 instituted new rules for well construction that resulted in drillers sinking three cement casings — instead of just two — more deeply along the well. Perry said that resulted in a decrease in gas-migration complaints.

DEP is looking at new rules to cover more inspections of the casings and the spaces between them during drilling. Meanwhile, drillers are improving their techniques as they find that each well differs greatly, depending on the geology below, according to Seth Pelepko, section chief for subsurface activities at DEP.

“It's a well-known fact that Pennsylvania has longstanding private water well-related challenges, a function of our region's unique geology – where stray methane gas is frequently present in and around shallow aquifers — along with the reality that we are one of only two states without uniform private water well construction standards,” said Dave Spigelmyer, president of the Marcellus Shale Coalition. “Given these clear facts, our industry has worked collaboratively with state officials to modernize and dramatically strengthen shale development-related regulations — from overall well construction practices, including enhanced casing and cementing requirements, to expanded pre-drill testing, among others — aimed at protecting groundwater.”

Finding the source of gas in water wells above shale formations has been a focus of research for several years.

Baldassare said he doubts Darrah's team's use of noble gases to mark gas from drilling is the ultimate key to identification, but said it's worth further study.

The research was funded by the National Science Foundation, Duke University and an environmental foundation. Darrah owns a company that uses noble gas testing in other geologic fields, but he said it would not benefit from the study's findings.

David Conti is a staff writer for Trib Total Media. He can be reached at 412-388-5802 or dconti@tribweb.com.