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Cross-sectional diagram of a vertical oil and gas well in the Greater Wattenberg Area with hypothetical fluid migration pathways through the surface casing.

When gas leaks into and contaminates a household water well near an oil and gas drilling site, there is always a question of where it came from. Is it from a failure in the drilling or was the gas migrating naturally?

by Greg Lackey (CivEngr MS’13, PhD’17), Joe Ryan, a professor and interim director of the Environmental Engineering Program, and a team of investigators at the University of Colorado Boulder, the National Energy Technology Laboratory, Johns Hopkins University, and Dalhousie University could help definitively answer that question.

“When gas leaks from an oil and gas well, its geochemical composition varies depending on the depth of the formation it came from. We’re analyzing that composition and can know if it’s from the producing formation at the bottom of the well or if it’s from somewhere closer to the surface,” Ryan said.

To prevent leaks, drilled wells comprise a series of nested pipes and cement with only the innermost pipe carrying produced oil and gas. In a properly functioning well, oil and gas never enters the space between the outer pipes. Earlier studies have shown that in the Wattenberg Field – a densely drilled area that underlays much of Weld County in northern Colorado – 26.5 percent of oil and gas wells have a buildup of gas, oil, or water in their outer pipes indicating a leak.

The Colorado Oil & Gas Conservation Commission requires operators to periodically test for leaked gas, oil, or water in the outer pipes of a well and to share the chemical composition of the leaked fluid publicly in a state database – the only state to do so. The team’s research analyzed those data for the study.

The chemical composition of the leaks in the Greater Wattenberg Area show that most are coming from failures of well pipes or cement, not natural stray gas migration.

While the study only looked at oil and gas wells, the ability to conclusively show failure in an inner pipe or cement has major implications, Ryan said.

“We don’t have to speculate anymore about sources. There are big projects going on across the country with contaminated water wells trying to tie them back to oil and gas drilling to help improve regulation. This shows that many oil and gas wells could indeed be sources for contamination,” Ryan said.

While liability is a clear concern for a homeowner with a water well, Ryan said the data is also important for drillers, as leaking oil and gas represents lost money.

“Operators have contacted us about the research because they want to know what wells are leaking so they can stop it,” Ryan said. “These wells can be repaired and there is a lot of effort going into that right now.”

This research grew out of AirWaterGas, a massive, five-year National Science Foundation-funded initiative led by CU Boulder that studied environmental, economic, and social tradeoffs of oil and gas development and their relation to public policies and regulations.

Lackey was part of the project during his PhD research at CU Boulder. While AirWaterGas ended in 2019, Ryan said its efforts led in part to Colorado expanding well leakage monitoring requirements, making it possible to study these issues in a new way.

“This research can help inform regulations and well construction so we can protect groundwater into the future,” Ryan said. “To do that, you have to prove where things comes from. This gives us a really clear look.”