Department of Physics, Ateneo de Manila University , Loyola Heights, Quezon City 1108, Philippines.
Department of Land, Air and Water Resources, University of California , Davis, California 95616, United States.
Environ Sci Technol. 2017 Jul 18;51(14):8001-8009. doi: 10.1021/acs.est.7b00814. Epub 2017 Jul 5.
Methane emissions from oil and gas facilities can exhibit operation-dependent temporal variability; however, this variability has yet to be fully characterized. A field campaign was conducted in June 2014 in the Eagle Ford basin, Texas, to examine spatiotemporal variability of methane emissions using four methods. Clusters of methane-emitting sources were estimated from 14 aerial surveys of two ("East" or "West") 35 × 35 km grids, two aircraft-based mass balance methods measured emissions repeatedly at five gathering facilities and three flares, and emitting equipment source-types were identified via helicopter-based infrared camera at 13 production and gathering facilities. Significant daily variability was observed in the location, number (East: 44 ± 20% relative standard deviation (RSD), N = 7; West: 37 ± 30% RSD, N = 7), and emission rates (36% of repeat measurements deviate from mean emissions by at least ±50%) of clusters of emitting sources. Emission rates of high emitters varied from 150-250 to 880-1470 kg/h and regional aggregate emissions of large sources (>15 kg/h) varied up to a factor of ∼3 between surveys. The aircraft-based mass balance results revealed comparable variability. Equipment source-type changed between surveys and alterations in operational-mode significantly influenced emissions. Results indicate that understanding temporal emission variability will promote improved mitigation strategies and additional analysis is needed to fully characterize its causes.
油气设施的甲烷排放具有依赖于操作的时间变化性，但这种变化性尚未得到充分描述。2014 年 6 月，在德克萨斯州的鹰福特盆地进行了一项现场活动，使用四种方法研究甲烷排放的时空变化。从对两个（“东”或“西”）35×35km 网格的 14 次航空调查中估算了甲烷排放源群，两个基于飞机的质量平衡方法在五个集气设施和三个火炬中重复测量了排放，通过在 13 个生产和集气设施的直升机上的红外摄像机确定了排放设备源类型。在位置、数量（东：7 次测量的 44 ± 20%相对标准偏差（RSD）；西：7 次测量的 37 ± 30% RSD）和排放率（36%的重复测量结果与平均排放值相差至少±50%）方面，排放源群存在显著的日变化。高排放源的排放率从 150-250kg/h 变化到 880-1470kg/h，大源（>15kg/h）的区域总排放量在两次调查之间变化了约 3 倍。基于飞机的质量平衡结果显示出类似的可变性。设备源类型在调查之间发生了变化，操作模式的改变对排放有显著影响。结果表明，了解时间排放变化性将促进改进缓解策略，并且需要进一步分析来充分描述其原因。
