Multiscale Methane Measurements at Oil and Gas Facilities Reveal Necessary Frameworks for Improved Emissions Accounting

Methane mitigation from the oil and gas (O&G) sector
represents
a key near-term global climate action opportunity. Recent legislation
in the United States requires updating current methane reporting programs
for oil and gas facilities with empirical data. While technological
advances have led to improvements in methane emissions measurements
and monitoring, the overall effectiveness of mitigation strategies
rests on quantifying spatially and temporally varying methane emissions
more accurately than the current approaches. In this work, we demonstrate
a quantification, monitoring, reporting, and verification framework
that pairs snapshot measurements with continuous emissions monitoring
systems (CEMS) to reconcile measurements with inventory estimates
and account for intermittent emission events. We find that site-level
emissions exhibit significant intraday and daily emission variations.
Snapshot measurements of methane can span over 3 orders of magnitude
and may have limited application in developing annualized inventory
estimates at the site level. Consequently, while official inventories
underestimate methane emissions on average, emissions at individual
facilities can be higher or lower than inventory estimates. Using
CEMS, we characterize distributions of frequency and duration of intermittent
emission events. Technologies that allow high sampling frequency such
as CEMS, paired with a mechanistic understanding of facility-level
events, are key to an accurate accounting of short-duration, episodic,
and high-volume events that are often missed in snapshot surveys and
to scale snapshot measurements to annualized emissions estimates.