Department of Energy Resources Engineering, Stanford University , 367 Panama Street, Stanford, California 94305, United States.
Environ Sci Technol. 2017 Jan 3;51(1):718-724. doi: 10.1021/acs.est.6b03906. Epub 2016 Dec 12.
Concerns over mitigating methane leakage from the natural gas system have become ever more prominent in recent years. Recently, the U.S. Environmental Protection Agency proposed regulations requiring use of optical gas imaging (OGI) technologies to identify and repair leaks. In this work, we develop an open-source predictive model to accurately simulate the most common OGI technology, passive infrared (IR) imaging. The model accurately reproduces IR images of controlled methane release field experiments as well as reported minimum detection limits. We show that imaging distance is the most important parameter affecting IR detection effectiveness. In a simulated well-site, over 80% of emissions can be detected from an imaging distance of 10 m. Also, the presence of "superemitters" greatly enhance the effectiveness of IR leak detection. The minimum detectable limits of this technology can be used to selectively target "superemitters", thereby providing a method for approximate leak-rate quantification. In addition, model results show that imaging backdrop controls IR imaging effectiveness: land-based detection against sky or low-emissivity backgrounds have higher detection efficiency compared to aerial measurements. Finally, we show that minimum IR detection thresholds can be significantly lower for gas compositions that include a significant fraction nonmethane hydrocarbons.
近年来，人们越来越关注减轻天然气系统中甲烷泄漏的问题。最近，美国环境保护署提议制定法规，要求使用光学气体成像（OGI）技术来识别和修复泄漏。在这项工作中，我们开发了一个开源的预测模型，以准确模拟最常见的 OGI 技术，即被动红外（IR）成像。该模型准确地再现了受控甲烷释放野外实验的红外图像以及报告的最低检测限。我们表明，成像距离是影响 IR 检测效果的最重要参数。在模拟的井场中，从 10 米的成像距离可以检测到超过 80%的排放物。此外，“超级排放源”的存在极大地提高了 IR 泄漏检测的效果。该技术的最低检测限可用于有选择地针对“超级排放源”，从而提供了一种近似泄漏率量化的方法。此外，模型结果表明，成像背景控制着红外成像的效果：与天空或低发射率背景相比，陆地检测具有更高的检测效率。最后，我们表明，对于包含大量非甲烷碳氢化合物的气体成分，最低红外检测阈值可以显著降低。
