Department of Geology, University of Cincinnati , Cincinnati, OH, USA.
J Air Waste Manag Assoc. 2020 Oct;70(10):1030-1042. doi: 10.1080/10962247.2020.1808115. Epub 2020 Sep 3.
Oil and natural gas wells are a prominent source of the greenhouse gas methane (CH), but most measurements are from newer, high producing wells. There are nearly 700,000 marginal "stripper" wells in the US, which produce less than 15 barrels of oil equivalent (BOE) d. We made direct measurements of CH and volatile organic carbon (VOC) emissions from marginal oil and gas wells in the Appalachian Basin of southeastern Ohio, all producing < 1 BOE d. Methane and VOC emissions followed a skewed distribution, with many wells having zero or low emissions and a few wells responsible for the majority of emissions. The average CH emission rate from marginal wells was 128 g h (median: 18 g h; range: 0- 907 g h). Follow-up measurements at five wells indicated high emissions were not episodic. Some wells were emitting all or more of the reported gas produced at each well, or venting gas from wells with no reported gas production. Measurements were made from wellheads only, not tanks, so our estimates may be conservative. Stochastic processes such as maintenance may be the main driver of emissions. Marginal wells are a disproportionate source of CH and VOCs relative to oil and gas production. We estimate that oil and gas wells in this lowest production category emit approximately 11% of total annual CH from oil and gas production in the EPA greenhouse gas inventory, although they produce about 0.2% of oil and 0.4% of gas in the US per year. : Low producing marginal wells are the most abundant type of oil and gas well in the United States, and a surprising number of them are venting all or more of their reported produced gas to the atmosphere. This makes marginal wells a disproportionate greenhouse gas emissions source compared to their energy return, and a good target for environmental mitigation.
油井和天然气井是温室气体甲烷（CH）的主要排放源，但大多数测量结果都来自较新的、高产量的油井。美国有近 70 万口边际“开采井”，这些井的石油当量产量（BOE）不足 15 桶/天。我们直接测量了俄亥俄州东南部阿巴拉契亚盆地边际油井和天然气井的 CH 和挥发性有机碳（VOC）排放，这些井的产量均低于 1 BOE/d。CH 和 VOC 的排放量呈偏态分布，许多井的排放量为零或低，而少数井的排放量则占了大部分。边际油井的 CH 排放量平均值为 128 g/h（中位数：18 g/h；范围：0-907 g/h）。对五口井的后续测量表明，高排放量并非偶发事件。一些井排放的气体等于或超过了每口井报告的产量，或者从没有报告产量的井中排放气体。测量仅在井口进行，而不在气罐处进行，因此我们的估计可能较为保守。维护等随机过程可能是排放的主要驱动因素。与油气产量相比，边际油井是 CH 和 VOC 的不成比例的排放源。我们估计，在 EPA 温室气体清单中，此类最低产量油井和天然气井每年排放的 CH 约占油气总产量的 11%，尽管它们每年在美国仅生产约 0.2%的石油和 0.4%的天然气。：低产边际井是美国最普遍的油气井类型，令人惊讶的是，许多井都将其报告的全部或大部分产量排放到大气中。与它们的能源回报相比，这使得边际井成为温室气体排放的不成比例的来源，也是环境缓解的一个很好的目标。
