Center for Energy and Environmental Resources, University of Texas at Austin, 10100 Burnett Road, Austin, Texas 78758, United States.
ExxonMobil Upstream Integrated Solutions, Spring, Texas 77389, United States.
Environ Sci Technol. 2021 Mar 2;55(5):2811-2819. doi: 10.1021/acs.est.0c04224. Epub 2021 Feb 15.
The methane emission intensity (methane emitted/gas produced or methane emitted/methane produced) of individual unconventional oil and gas production sites in the United States has a characteristic temporal behavior, exhibiting a brief period of decrease followed by a steady increase, with intensities after 10 years of production reaching levels that are 2-10 times the 10 year production-weighted average. Temporal patterns for methane emission intensity for entire production regions are more complex. Historical production data and facility data were used with a detailed basin-wide methane emission model to simulate the collective behavior of tens of thousands of wells and associated midstream facilities. For production regions with few to no new wells being brought to production, and existing wells having reached a mature stage, as in the Barnett Shale production region in north central Texas, the methane emission intensity gradually increases, as natural gas production decreases faster than emissions decrease, following the general pattern exhibited by individual wells. In production regions that are rapidly evolving, either with large numbers of new wells being put into production or with the introduction of source-specific regulations, the behavior is more complex. In the Eagle Ford Shale, which has had both a large number of new wells and the introduction of source-specific regulations, the methane emission intensity stays within relatively narrow bounds but the distribution of sources varies. As source distributions vary, basin-wide propane-to-methane and ethane-to-methane emission ratios vary, impacting methods used in source attribution.
美国个别非常规油气生产场地的甲烷排放强度（排放的甲烷量/产生的气体量或排放的甲烷量/产生的甲烷量）具有特征性的时间行为，表现为短暂的下降期，随后是稳定的上升期，生产 10 年后的强度达到 10 年生产加权平均值的 2-10 倍。整个生产区域的甲烷排放强度的时间模式更加复杂。利用历史生产数据和设施数据，并结合详细的盆地范围甲烷排放模型，模拟了成千上万口井和相关中游设施的集体行为。对于新井数量较少或没有新井投入生产，且现有井已达到成熟阶段的生产区域，例如德克萨斯州中北部的 Barnett Shale 生产区域，随着天然气产量的下降速度快于排放量的下降速度，甲烷排放强度逐渐增加，这与个别井表现出的一般模式一致。在快速发展的生产区域，无论是有大量新井投入生产还是引入了针对特定来源的法规，情况都更加复杂。在 Eagle Ford Shale，该地区有大量新井和引入了针对特定来源的法规，甲烷排放强度保持在相对狭窄的范围内，但源的分布有所不同。由于源的分布不同，整个盆地丙烷与甲烷和乙烷与甲烷的排放比也有所不同，从而影响了源归属方法的使用。
