Regulators and companies must update their tools for assessing methane emissions in order to capture the wide swings in releases of planet-warming gas from upstream oil and gas facilities, according to a study based on months of observations at oil and gas drilling locations.

A key takeaway of the study was that the effectiveness of mitigation strategies will depend on more accurate monitoring than existing approaches to account for emissions that can vary significantly even within a day. Researchers found that snapshot measurements of methane emissions can vary by more than three orders of magnitude over a span of just days — from less than 50 cubic feet per hour to more than 10,000 cubic feet per hour.

Better tracking of large releases, or "super-emitting events," could help close the gap between estimated and observed emissions, according to the study. And it could prove critical to the credibility of the emerging trade in natural gas certified as low in greenhouse emissions, researchers said. Certified gas — sometimes called differentiated gas or responsibly sourced gas — meets certain intensity thresholds for planet-warming emissions and other environmental, social and governance standards.

But "no empirical measurement protocol has yet been demonstrated that can provide reasonably accurate supply chain-specific methane emission estimates necessary to assess such claims," the study authors said.

"Given that these technologies are advancing at a rapid pace, companies have a vested interest in demonstrating that their specific supply chains have lower emissions across the supply chain than other companies," said co-author Arvind Ravikumar, an engineer in the petroleum and geosystems engineering department at the University of Texas, in an interview. "But no one has actually shown what kind of measurements you need to do and what those measurements tell us."

The study, which is undergoing peer review, used an array of monitoring technologies at 38 oil and gas sites across the Marcellus, Haynesville and Permian Basin production regions over six months. Five natural gas producers participated. Using cameras, drones, planes, satellites and continuous emissions-monitoring systems, researchers observed methane emissions that exceeded government inventories in some cases and fell short in others.

Scrutiny on methane

The research was funded by Cheniere Energy Inc. as part of the LNG producer's efforts to develop a better process for certifying emissions along the natural gas supply chain in response to increasing pressure from customers and policymakers to curb emissions. Emissions of methane have faced particular scrutiny.

Methane has a global warming potential over a 20-year period that is more than 80 times greater than carbon dioxide. But methane also remains in the atmosphere for a much shorter period than carbon dioxide, making reductions in methane emissions a key target for mitigating climate change. Atmospheric methane hit a record high in 2021.

A recent staff report by congressional Democrats criticized efforts by oil and gas companies to detect and monitor methane leaks as insufficient. The report came at a time when the White House is preparing new regulations for the industry.

"Oil and gas companies are failing to use quantification data to mitigate methane leak emissions," the Democratic staff report said.

The Cheniere-backed researchers' findings were consistent with a series of other academic studies that have shown that measurements of U.S. oil and gas supply chain emissions were greater on average than U.S. Environmental Protection Agency figures. One reason for the gap was that official estimates missed emissions during unplanned events such as equipment malfunctions that bottom-up engineering estimates fail to capture in reports to the regulator, studies have found.

Researchers in the recent study also observed that, in some cases, continuous monitoring of site-level emissions could show a more favorable emissions footprint than what the EPA framework would suggest. Periodic surveys of a large enough sample size can provide a "reasonably accurate estimate" of baseline methane emissions for an oil and gas basin, Ravikumar said.

"But that is a different question than asking: 'What is a supply chain's specific methane emissions?'" Ravikumar said. "Or, if there is one company: 'Can I certify my assets to have methane emissions below a target number?' Because now you are not talking about basin-level stuff."

Quarterly measurements, for example, would not be sufficient for certifying gas supplies from a small number of facilities, even if the gas volume is significant, Ravikumar said.

"Emissions vary quite a lot — even between whether you measure in the morning versus the afternoon, or versus measuring today or measuring Friday," Ravikumar said. "So if your goal is to use an emissions number in contracts and in trades, then you need to make sure there that your emissions have some level of accuracy."

Recommendations for upstream producers

The study recommended four guidelines for developing protocols to accurately estimate methane emissions and inform mitigation strategies. First, researchers recommended using snapshot measurements to quantify methane sources at specific sites or pieces of equipment to close the gap with inventory estimates. Next, the researchers advised using technologies that sample emissions at a high rate to account for the frequency and duration of unexpected methane releases. Third, the authors encouraged detailed recordkeeping on one-time releases, maintenance and upset conditions.

Finally, the scientists noted that "independent verification of measurements and quantified emissions, along with operational data, using transparent, peer-reviewed approaches can enable trust-building with the broader public," adding that verification should go beyond a checklist of best practices.

Additional Cheniere-funded studies by Ravikumar and other researchers will look at other parts of the LNG supply chain, including the U.S. midstream sector.

"As these technologies improve, there is going to be a lot of interest from buyers of U.S. LNG to understand what methane emissions are associated with the supply chain," Ravikumar said. "And the only way to do that is by direct measurements."

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