Climate and Space Sciences and Engineering, University of Michigan, 2549 Space Research Building, 2455 Hayward Street, Ann Arbor, Michigan 48109, United States.
Carbon Mapper Inc., Pasadena, California 91105, United States.
Environ Sci Technol. 2024 Mar 19;58(11):4948-4956. doi: 10.1021/acs.est.3c08066. Epub 2024 Mar 6.
Methane emissions from the oil and gas supply chain can be intermittent, posing challenges for monitoring and mitigation efforts. This study examines shallow water facilities in the US Gulf of Mexico with repeat atmospheric observations to evaluate temporal variation in site-specific methane emissions. We combine new and previous observations to develop a longitudinal study, spanning from days to months to almost five years, evaluating the emissions behavior of sites over time. We also define and determine the chance of subsequent detection (CSD): the likelihood that an emitting site will be observed emitting again. The average emitting central hub in the Gulf has a 74% CSD at any time interval. Eight facilities contribute 50% of total emissions and are over 80% persistent with a 96% CSD above 100 kg/h and 46% persistent with a 42% CSD above 1000 kg/h, indicating that large emissions are persistent at certain sites. Forward-looking infrared (FLIR) footage shows many of these sites exhibiting cold venting. This suggests that for offshore, a low sampling frequency over large spatial coverage can capture typical site emissions behavior and identify targets for mitigation. We further demonstrate the preliminary use of space-based observations to monitor offshore emissions over time.
油气供应链中的甲烷排放可能是间歇性的，这给监测和减排工作带来了挑战。本研究通过对美国墨西哥湾浅水资源的重复大气观测，考察了特定地点甲烷排放的时间变化。我们结合新的和以前的观测结果，开展了一项纵向研究，时间跨度从几天到几个月，再到近五年，评估了随着时间推移各地点的排放行为。我们还定义并确定了后续检测的机会（CSD）：排放点再次被观测到排放的可能性。墨西哥湾内排放中心的平均 CSD 在任何时间间隔都为 74%。有 8 个设施贡献了 50%的总排放量，并且具有 80%以上的持续性，在 100kg/h 以上时的 CSD 为 96%，在 1000kg/h 以上时的 CSD 为 46%，这表明某些地点的大量排放是持续的。前视红外（FLIR）镜头显示，其中许多站点都有冷排放。这表明，对于海上作业，在较大的空间覆盖范围内进行低频采样可以捕获典型的站点排放行为，并确定减排目标。我们还进一步展示了使用天基观测来监测海上排放随时间的变化的初步应用。
