Colorado Ongoing Basin Emissions: Combining Aerial Survey Data with Distributions from the Literature to Estimate a State-Wide Methane Emission Inventory

Accurate quantification of methane emissions from oil and gas operations is essential for guiding mitigation strategies and informing regulatory policy. In the Colorado Ongoing Basin Emissions (COBE) project, we develop a modeling framework to estimate state‑wide annual methane emissions from the upstream oil and gas sector in Colorado by combining instantaneous emission rate measurements from three aerial vendors with emissions distributions from the literature. Aerial surveys conducted throughout 2024 and 2025 by Bridger Photonics, GHGSat, and Insight M captured snapshot measurements of methane emissions across a representative sample of production sites in Colorado. We construct empirical distributions of instantaneous emission rates using these aerial observations, and supplement them with state-of-the art distributions from the literature (Williams et al., 2024 and Sherwin et al., 2025) to capture the small emissions potentially missed by aerial surveys. These distributions are repeatedly sampled from within a Monte Carlo framework to propagate uncertainty, yielding probabilistic estimates of annual emissions at the state level. Aggregation across all production oil and gas sites in Colorado produces a state‑wide annual methane emissions estimate of approximately 90,000 metric tons, varying slightly depending on the literature distribution used, over three times the bottom-up estimate of state-wide emissions. We have also employed continuous monitoring data from point-in-space networks to inform the low emission rate distribution, but do not include those results due to the limited number of sites encompassed. Future work will involve collecting continuous monitoring data at many more sites across Colorado, allowing us to estimate an entirely measurement-derived inventory.