ABSTRACT

Oil and natural gas wells are a prominent source of the greenhouse gas methane (CH₄), 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⁻¹. We made direct measurements of CH₄ and volatile organic carbon (VOC) emissions from marginal oil and gas wells in the Appalachian Basin of southeastern Ohio, all producing < 1 BOE d⁻¹. 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 CH₄ emission rate from marginal wells was 128 g h⁻¹ (median: 18 g h⁻¹; range: 0– 907 g h⁻¹). 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 CH₄ 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 CH₄ 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.

Implications: 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.

摘要

石油和天然气井是温室气体甲烷（CH ₄）的主要来源，但是大多数测量是从更新的高产井中进行的。在美国，有近700,000的边际“汽提塔”井，产量少于15桶油当量（BOE）d ^-1。我们直接测量了俄亥俄州东南部阿巴拉契亚盆地边缘油气井中的CH ₄和挥发性有机碳（VOC）排放，所有排放量均<1 BOE d ^-1。甲烷和VOC排放呈偏斜分布，许多井的排放为零或低，而少数井则占了大部分排放。边缘井的平均CH ₄排放速率为128 gh ^-1（中位数：18 gh ^-1；范围：0–907 gh ^-1）。在五口井的后续测量结果表明，高排放不是偶然的。一些井正在排放每个井中产生的全部或更多报告的气体，或者从没有报告的气体产生的井中排出气体。测量仅是从井口而不是坦克进行的，因此我们的估计可能是保守的。维护等随机过程可能是排放的主要驱动因素。相对于油气生产，边缘井是CH ₄和VOC的不成比例来源。我们估计，该最低产量类别的油气井排放的甲烷约占年度总CH _4的11％ 从EPA温室气体清单中的石油和天然气生产中提取，尽管在美国每年它们生产约0.2％的石油和0.4％的天然气。

含义：低产边际油井是美国油气储量最丰富的类型，其中令人惊讶的数量正在将其报告的全部或更多产气排入大气。与能量返回相比，这使得边缘井成为温室气体排放源的不成比例，并且是缓解环境的良好目标。