Center for Energy and Environmental Resources, University of Texas at Austin , 10100 Burnet Road, Building 133, M.S. R7100, Austin, Texas 78758, United States.
Environ Sci Technol. 2015 Jan 6;49(1):641-8. doi: 10.1021/es504016r. Epub 2014 Dec 9.
Methane emissions from liquid unloadings were measured at 107 wells in natural gas production regions throughout the United States. Liquid unloadings clear wells of accumulated liquids to increase production, employing a variety of liquid lifting mechanisms. In this work, wells with and without plunger lifts were sampled. Most wells without plunger lifts unload less than 10 times per year with emissions averaging 21,000-35,000 scf methane (0.4-0.7 Mg) per event (95% confidence limits of 10,000-50,000 scf/event). For wells with plunger lifts, emissions averaged 1000-10,000 scf methane (0.02-0.2 Mg) per event (95% confidence limits of 500-12,000 scf/event). Some wells with plunger lifts are automatically triggered and unload thousands of times per year and these wells account for the majority of the emissions from all wells with liquid unloadings. If the data collected in this work are assumed to be representative of national populations, the data suggest that the central estimate of emissions from unloadings (270 Gg/yr, 95% confidence range of 190-400 Gg) are within a few percent of the emissions estimated in the EPA 2012 Greenhouse Gas National Emission Inventory (released in 2014), with emissions dominated by wells with high frequencies of unloadings.
在美国各地的天然气生产区，对 107 口井的液体卸载过程中的甲烷排放进行了测量。液体卸载可清除井内积聚的液体，从而提高产量，并采用各种液体提升机制。在这项工作中，对有和没有柱塞提升的井进行了采样。大多数没有柱塞提升的井每年卸载次数少于 10 次，每次排放的甲烷平均值为 21,000-35,000 立方英尺（0.4-0.7 公吨）（95%置信区间为 10,000-50,000 立方英尺/事件）。对于有柱塞提升的井，甲烷排放量平均为每次 1000-10,000 立方英尺（0.02-0.2 公吨）（95%置信区间为 500-12,000 立方英尺/事件）。一些带有柱塞提升的井会自动触发并每年卸载数千次，这些井占所有进行液体卸载的井排放的大部分。如果假设本工作中收集的数据具有全国代表性，则数据表明，卸载排放的中心估计值（270 吉克/年，95%置信范围为 190-400 吉克）与 EPA 2012 年温室气体国家排放清单（于 2014 年发布）中估计的排放值相差几个百分点，排放主要由卸载频率高的井主导。
