This study evaluated multiple commercially available continuous monitoring (CM) point sensor network (PSN) solutions under single-blind controlled release testing conducted at operational upstream and midstream oil and natural gas (O&G) sites. During releases, PSNs reported site-level emission rate estimates of 0 kg/h between 38 and 86% of the time. When non-zero site-level emission rate estimates were provided, no linear correlation between the release rate and the reported emission rate estimate was observed. The average, aggregated across all PSN solutions during releases, shows 5% of the mixing ratio readings at downwind sensors were greater than the site’s baseline plus two standard deviations. Four of seven total PSN solutions tested during this field campaign provided site-level emission rate estimates with the site average relative error ranging from −100% to 24% for solution D, −100% to −43% for solution E, −25% for solution F (solution F was only at one site), and −99% to 430% for solution G, with an overall average of −29% across all sites and solutions. Of all the individual site-level emission rate estimates, only 11% were within ±2.5 kg/h of the study team’s best estimate of site-level emissions at the time of the releases.

Recent regulatory spotlight on continuous monitoring (CM) solutions and the rapid development of CM solutions has demanded the characterization of solutions performance through regular, rigorous testing using consensus test protocols. This study is the second known implementation of such protocol involving single-blind controlled testing of 9 CM solutions. Controlled releases of rates (6 to 7100) g CH4/h over durations (0.4 to 10.2) hours under wind speed range of (0.7 to 9.9) m/s were conducted for 11 weeks. Results showed that 4 solutions achieved method detection limits (DL90s) within tested emission rate range with all 4 solutions having both the lowest DL90s (3.9 [3.0, 5.5] kg CH4/h to 6.2 [3.7, 16.7] kg CH4/h) and false positive rates (6.9% to 13.2%) indicating efforts at balancing low sensitivity with low false positive rate. Quantification results showed wide individual estimate uncertainties with emissions underestimation and overestimation by factors up to > 14 and 42 respectively. Three solutions had > 80% of their estimates within a quantification factor of 3 for controlled releases in the ranges of (0.1 – 1] kg CH4/h and >1 kg CH4/h. Relative to the study by Bell et al., current solutions performance, as a group, generally improved primarily due to solutions from the study by Bell et al. that retested. This result highlights the importance of regular, quality testing to the advancement of CM solutions for effective emissions mitigation.

This study evaluated multiple commercially available continuous monitoring (CM) point sensor network (PSN) solutions under single-blind controlled release testing conducted at operational upstream and midstream oil and natural gas (O&G) sites. During releases, PSNs reported site-level emission rate estimates of 0 kg/h between 38-86% of the time. When non-zero site-level emission rate estimates were provided, no linear correlation between release rate and reported emission rate estimate was observed. The average, aggregated across all PSN solutions during releases, shows 5% of mixing ratio readings at downwind sensors were greater than the site's baseline plus two standard deviations. Four of six total PSN solutions tested during this field campaign provided site-level emission rate estimates with the site average relative error ranging from -100% to 24% for solution D, -100% to -43% for solution E, -25% for solution F (solution F was only at one site), and -99% to 430% for solution G, with an overall average of -29% across all sites and solutions. Of all the individual site-level emission rate estimates, only 11% were within +/- 2.5 kg/h of the study team's best estimate of site-level emissions at the time of the releases.

Continuous emission monitoring (CM) solutions promise to detect large fugitive methane emissions in natural gas infrastructure sooner than traditional leak surveys, and quantification by CM solutions has been proposed as the foundation of measurement-based inventories. This study performed single-blind testing at a controlled release facility (release from 0.4 to 6400 g CH4/h) replicating conditions that were challenging but less complex than typical field conditions. Eleven solutions were tested, including point sensor networks and scanning/imaging solutions. Results indicated 90% probability of detection (POD) of 3-30 kg CH4/h; 6 of 11 solutions achieved POD >50%. False positive rates ranged from 0 to 79%. Six solutions estimated emission rates. For release rate of 0.1-1 kg/h, the solutions' mean relative errors ranged from -44% to +586% with single estimates between -97% and +2077%, with 4 solutions' upper uncertainty exceeding +900%. Above 1 kg/h, mean relative error was -40% to +93%, with two solutions within 20%, and single-estimate relative errors from -82% to +448%. The large variability in performance between CM solutions, coupled with highly uncertain detection, detection limit, and quantification results, indicate that the performance of individual CM solutions should be well understood before relying on results for internal emissions mitigation programs or regulatory reporting.