Methane Emissions

"Controlling methane emissions is an effective way to slow global warming. Because methane is very effective at trapping heat and has a relatively short lifetime of about a decade before it oxidizes to carbon dioxide, controlling its emissions is an effective way of reducing the heat trapped in the atmosphere now. It is very influential in determining how rapidly the planet warms." - Prof. Denise Mauzerall, Q&A on Methane Emissions

Methane (CH4) is a potent greenhouse gas, and since 1850 the concentration of atmospheric methane has more than doubled. We have found that emission inventories may be missing sources and underestimating emissions, including leakage from offshore oil and gas rigs and abandoned and active gas and oil wells.

Methane emissions from oil and gas platforms in the North Sea

To investigate whether offshore oil and gas platforms leak methane (CH4) during normal operation, our researchers measured CH4 around eight oil and gas production platforms in the North Sea which were neither flaring gas nor offloading oil. They used measurements from summer 2017, along with meteorological data, to estimate CH4 emissions from each platform. When matched to production records, during their measurements individual platforms lost between 0.04 % and 1.4 % of gas produced with a median loss of 0.23 %. When the measured platforms are considered collectively, our researchers estimate the CH4 loss to be 0.19 % of gas production.

These estimates are substantially higher than the emissions most recently reported to the National Atmospheric Emission Inventory (NAEI) for total CH4 loss from United Kingdom platforms in the North Sea. The NAEI reports CH4 losses from the offshore oil and gas platforms our researchers measured to be 0.13 % of gas production, with most of these platforms' emissions coming from gas flaring and offshore oil loading, neither of which was taking place at the time of our researchers' measurements. All oil and gas platforms we observed were found to leak CH4 during normal operation, and much of this leakage has not been included in UK emission inventories. Further research is required to accurately determine total CH4 leakage from all offshore oil and gas operations and to properly include the leakage in national and international emission inventories.

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Measuring methane emissions from abandoned and active oil and gas wells in the U.S.

Methane emissions from abandoned oil and gas wells can be significant, and our researchers have found evidence to suggest that estimates of methane emissions by the EPA and states has been under-counted. Taking direct measurements of emissions at a variety of wells at different times of year in Pennsylvania and West Virginia, our researchers estimate the number of existing oil and gas wells, rates of methane emissions, and potential variability.

Some wells emit significantly higher amounts of methane than others (“high emitters”). We use models to define the typical characteristics of these high emitters and estimate the methane emissions that could result from these wells if steps are not taken to mitigate them. Our researchers conclude that high emitters are best predicted as unplugged gas wells and plugged/vented gas wells in coal areas. These high emitters appear to be unrelated to the presence of underground natural gas storage areas or unconventional oil/gas production. There also does not appear to be a pattern related to age or operator of the wells, and emissions rates can also vary within the same geologic formations. We observed that the flow rate of high emitters did not decline over a 2-year period, making this an important area for mitigation efforts.

In a recent study, our researchers consider opportunities for addressing emissions of oil and gas wells, analyzing five different options and their costs. In addition to a cost analysis, we considered the “social cost” of methane leakage to consider its impact on air quality, climate, and human/ecosystem impacts as well. Since the cost to mitigate emissions at a single well can cost ~$37,000, our researchers consider the role of policy to help prioritize cost-effective mitigation strategies.

Related Research: