There has been much research to measure methane emissions from natural gas operations using ‘top-down’ aircraft measurements and on the ground ‘bottom-up’ analysis of methane leakage. Aerial research often reflect estimates of up to six times the amount of leakage than ground-based assessments. Research led by the Colorado State University has found that the two methods of measurement largely line up when episodic releases of methane that occur mainly during day-time only maintenance operations are taken into consideration.
A routine manual well-clearing maintenance operation that occurs in the daytime can cause short periods of high natural gas emissions. These were often picked up by aircraft involved in measurements, flying during these ideal daily meteorological periods. Bottom-up measurements would be measuring on a daily, monthly or annual average and not be isolating these instances.
“The key to our efforts was having everyone out in the same field, at the same time,” said Gabrielle Petron, a research scientist from the Cooperative Institute for Research in Environmental Sciences (CIRES) at Colorado University in Boulder and the National Oceanic and Atmospheric Administration (NOAA). Petron was the principal investigator for the top-down measurement team. “By comparing the merits and pitfalls of multiple methods of measurement, we were able to paint a much more comprehensive, and we believe accurate, picture of the methane emissions landscape for natural gas infrastructure.”
More than 60 researchers were involved in the Basin Methane Reconciliation Study, including representatives from Colorado State University; the Colorado School of Mines; the National Renewable Energy Laboratory; NOAA; and the University of Colorado, Boulder. Industry support for site access and operational access were provided by multiple companies in the Fayetteville shale basin, where the study took place.
A study by the Environmental Defense Fund (EDF) released in June 2018 titled, “Assessment of methane emissions from the U.S. oil and gas supply chain”, indicated U.S. oil and gas methane emissions were 60% higher than EPA reports. David Lyon, an EDF scientist who worked on the study indicated similar strategies were used, but the recent CU report had better synchronization of data due to more participation from industry. The data from the CU report looked at only the Fayetteville basin, thus Lyon cautioned it may be useful for comparing emissions data from the same basin but should not be considered representative of other basins. Garvin Heath, with NREL stated the methods used in this study can be adapted and applied to other regions to improve understanding of methane sources and find ways to reduce losses and improve efficiency of industrial practices.
The study was published in the October 20th issue of the National Academy of Sciences. Additional papers regarding the study can be found on the Colorado State University website.