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

Abstract

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.

Technological avenues and market mechanisms to accelerate methane and nitrous oxide emissions reductions

“…30 The amount of emissions reported from this sector can vary widely because of different measurement or estimation techniques and geographical variations. 31 However, important identified sources include storage tanks, equipment leaks, pneumatic controllers, liquids unloading, associated gas flaring and venting, completions and workovers, and methane slip. 32 Additionally, large amounts of CH 4 emissions are attributed to low production well sites, requiring particular attention for further mitigation efforts.…”

“…Additional alternatives currently under development consider monitoring networks capable of capturing the characteristic temporal and spatial variabilities of oil and gas CH 4 emissions for detailed emission inventories. 31 In addition, abatement technologies limit loss of valuable, salable natural gas, rendering it a cost-effective mitigation technology. 44…”

“…This enforces a methane charge of $900/t-CH 4 (increasing to $1500/t-CH 4 after two years) for specific petroleum and natural gas facilities. 31 This provision accounts for CH 4 emissions directly without converting them to a CO 2 -equivalent basis. Such an approach will directly constrain emissions below the preselected threshold.…”

Impact of the High-Emission Event Duration and Sampling Frequency on the Uncertainty in Emission Estimates

“…Cusworth et al, sampling a larger number of sites, found that short-lived (<1 month) and long-lived (>1 year) sources were both significant contributors to overall emissions across multimonth and multiyear campaigns. Wang et al also found that for some oil and gas basins, the most common emission duration was <1 h . The variability in emission magnitude and duration requires that a large number of observations be taken to accurately measure and represent these high-emission events.…”

Methane emission detection, localization, and quantification using continuous point-sensors on oil and gas facilities

“…9,12,13 Bottom-up inventories have been found to underestimate total emissions and are poorly suited to accommodate these complicated emission characteristics. [14][15][16][17][18][19] Therefore, direct measurements are needed to better understand and mitigate emissions. In fact, the Inflation Reduction Act will soon require that all reported methane emissions from the United States oil and gas sector are derived from empirical data rather than conventional bottom-up inventories.…”