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

Methane emissions from oil and gas operations exhibit skewed distributions. New technologies such as aerial-based leak detection surveys promise cost-effective detection of large emitters. Recent policies such as the proposed US Environmental Protection Agency methane rule that allows the use of new technologies as part of conventional leak detection and repair (LDAR) require demonstration of equivalence with existing optical gas imaging (OGI)-based LDAR programs. In this work, we illustrate the impact of emission size distribution on the equivalency between OGI-based LDAR programs and that of alternative LDAR programs that use site-wide surveys. We find that emission size distribution compiled from aerial measurements across four oil and gas basins include significantly more emitters in the 1 – 10 kg/h and an order of magnitude lower average emission rate for large emitters compared to the emissions distribution in the EPA methane rule. As a result, equivalence between OGI-based surveys and site-wide screening may be achieved at lower site-wide survey frequencies when using technologies with detection threshold below 10 kg/h, compared to the EPA methane rule. However, equivalency cannot be achieved for site-wide screening with a detection threshold of 30 kg/h at any survey frequency because most emitters across most US oil and gas basins exhibit emission rates below 30 kg/h. We find that equivalence is a complex trade-off between the choice of technologies, design of hybrid LDAR programs, and survey frequency that can have more than one unique solution set.