Performance of continuous emission monitoring systems at operating oil and gas facilities
Date
2024
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Abstract
Globally, demand to reduce methane (CH4) emissions has become paramount and the oil and natural gas (O&G) sector is highlighted as one of the main contributors, being the largest industrial emission source at ≈30%. In efforts to follow legislation of CH4 emission reductions, O&G operators, emission measurement solution companies, and researchers have been testing various techniques and technologies to accurately measure and quantify CH4 emissions. As recent changes to U.S. legislative policies in the Greenhouse Gas Reporting Program (GHGRP) and Inflation Reduction Act (IRA) are imposing a methane waste emission charge beginning in 2024, O&G operators are looking for more continuous and efficient methods to effectively measure emissions at their facilities. Prior to these policy updates, bottom-up measurement methods were the main technique used for reporting yearly emissions to the GHGRP, which involves emission factors and emission source activity data. Top-down measurement methods such as fly-overs with airplanes, drones, or satellites, can provide snap in time surveys of the overall site emissions. With prior research showing the variance between top-down and bottom-up emission estimates, O&G operators have become interested in continuous emissions monitoring systems (CEMs) for their sites to see emission activity continually overtime. A type of CEM, a continuous monitoring (CM) point sensor network (PSN), monitors methane emissions continuously with sensors mounted at the perimeter of O&G sites. CM PSN solutions have become appealing, as they could potentially offer a relatively cost effective and autonomous method of identifying sporadic and fugitive leaks. This study evaluated multiple commercially available CM PSN solutions under single-blind controlled release testing conducted at operational upstream and midstream 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.
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Embargo expires: 05/20/2025.