Role of Intermittency on the Effectiveness of Methane Emissions Detection at Oil and Gas Facilities: Comparative Assessment of Optical Gas Imaging and Site-wide Surveys

Abstract

Intermittent emission events are a significant source of methane emissions from oil and gas operations. New technologies such as site-wide aerial surveys promise more effective detection of intermittent emission events compared to conventional optical gas imaging (OGI) surveys. In this work, we present case studies to assess role of intermittent emission events on the emissions reduction equivalence between conventional OGI-based surveys and site-wide screening surveys with new technologies. We find that the equivalence condition between OGI-based surveys and site-wide screening is robust against different assumptions about the duration of large emitters. As duration of large emitters decrease, monthly site-wide screening surveys are more effective at detecting large emitters compared to quarterly OGI monitoring. However, the contribution of large emitters to total emissions also decreases, which reduces the impact of the higher detection effectiveness of site-wide surveys. In addition, annual OGI survey as part of site-wide screening strategy is more critical when the detection threshold of the screening technology is greater than 10 kg/h or higher as the screening survey does not detect below detection threshold emissions.

The Role of Emission Size Distribution on the Efficacy of New Technologies to Reduce Methane Emissions from the Oil and Gas Sector

“…The presence of high-volume intermittent emission sources, which could or could not be detected by the certain times of surveys, could significantly alter the conditions under which equivalence with quarterly OGI-based LDAR surveys are achieved. Recent work demonstrates the impact of intermittency on equivalency using different modeling approaches. , Besides, in this study, we assume the leak generation rates for the general, tank, and large emitters were 0.5%, 2.5%, and 1.5%, respectively, while in reality, the leak generation rate and the number of different types of emitters across different basins may not be the same. Therefore, future work should focus on evaluating the coupled uncertainties associated with multiple realistic modeling parameters across different US oil and gas basins.…”

“…In its proposed regulations, the EPA allowed the use of alternative, site-wide screening technologies in LDAR programs by determining the equivalence with OGI-based LDAR surveys. Equivalence was determined using the fugitive emissions abatement simulation toolkit or FEAST model that helps compare emissions reduction associated with different LDAR programs. − The EPA adopted a matrix approach to determine the combination of technology (using the detection threshold as a proxy) and survey frequency that would achieve emissions reductions equivalent to that of an OGI-based LDAR program. In undertaking this modeling effort, the EPA used two separate emissions distributions: one for general fugitives and tank emissions and another for large emitters.…”

Point Sensor Networks Struggle to Detect and Quantify Short Controlled Releases at Oil and Gas Sites

“…NR data were utilized to compare site-level emission rate estimates with/without active ChRs. Note that the field campaign did not measure a background site methane emission baseline from leak screening (e.g., optical gas imaging [ 33 , 34 ]) or measurement by a downwind method (such as OTM33 [ 35 , 36 ]). The mean of NR site-level emission rate estimates from each solution was used to represent what the solution would report in the absence of a ChR at a given site, hereafter referred to as ‘baseline (BL)’.…”

Large-Scale Controlled Experiment Demonstrates Effectiveness of Methane Leak Detection and Repair Programs at Oil and Gas Facilities

“…Most field studies of methane emissions from oil and gas facilities using new technologies, such as aircrafts and satellites, provide snapshot measurement data; while they are detailed in spatial extent, they do not track the variation of individual component-level emissions. , This is critical because measurements have revealed significant differences in emissions across seasons, time of day, and other temporal variables. − Furthermore, recent studies have found that emission intermittency impacts the effectiveness of LDAR surveys as well as emission estimates. , Currently, only one study has empirically demonstrated emission reductions from regulatory LDAR programs with data from a small number of facilities …”

“…33−36 Furthermore, recent studies have found that emission intermittency impacts the effectiveness of LDAR surveys as well as emission estimates. 37,38 Currently, only one study has empirically demonstrated emission reductions from regulatory LDAR programs with data from a small number of facilities. 39 In this work, we present results from a large-scale, randomized controlled trial of the effectiveness of LDAR surveys in reducing methane emissions using component-level repeat surveys from approximately 200 oil and gas sites across 18 operators in Alberta, Canada.…”