Department of Chemical Engineering, University of Texas at Austin, Austin, Texas 78712, United States.
Center for Energy and Environmental Resources, University of Texas at Austin, Austin, Texas 78758, United States.
Environ Sci Technol. 2024 Feb 13;58(6):2739-2749. doi: 10.1021/acs.est.3c08185. Epub 2024 Feb 1.
Methane emission estimates for oil and gas facilities are typically based on estimates at a subpopulation of facilities, and these emission estimates are then extrapolated to a larger region or basin. Basin-level emission estimates are then frequently compared with basin-level observations. Methane emissions from oil and gas systems are inherently variable and intermittent, which make it difficult to determine whether a sample population is sufficiently large to be representative of a larger region. This work develops a framework for extrapolation of emission estimates using the case study of an operator in the Green River Basin. This work also identifies a new metric, the capture ratio, which quantifies the extent to which sources are represented in the sample population, based on the skewness of emissions for each source. There is a strong correlation between the capture ratio and extrapolation error, which suggests that understanding source-level emissions distributions can mitigate error when sample populations are selected and extrapolating measurements. The framework and results from this work can inform the selection and extrapolation of site measurements when developing methane emission inventories and establishing uncertainty bounds to assess whether inventory estimates are consistent with independent large spatial-scale observations.
油气设施的甲烷排放估算通常基于设施子群体的估算，然后将这些排放估算外推到更大的区域或盆地。然后，盆地层面的排放估算经常与盆地层面的观测值进行比较。油气系统的甲烷排放具有固有变异性和间歇性，这使得很难确定样本群体是否足够大，足以代表更大的区域。这项工作开发了一种使用绿河盆地运营商的案例研究来估算排放的外推框架。这项工作还确定了一个新的度量标准，即捕获比，它根据每个源的排放偏度来量化源在样本群体中的代表性程度。捕获比与外推误差之间存在很强的相关性，这表明在选择样本群体和外推测量时，了解源级排放分布可以减轻误差。这项工作的框架和结果可以为开发甲烷排放清单时选择和外推站点测量以及建立不确定性界限以评估清单估计值是否与独立的大空间尺度观测值一致提供信息。
