A cautionary tale: A study of a methane enhancement over the North Sea

Cain, Michelle; Warwick, N. J.; Fisher, Rebecca E.; Lowry, David; Lanoisellé, M.; Nisbet, E. G.; Pitt, Joseph; O’Shea, Sebastian; Bower, Keith; Allen, Grant; Illingworth, Sam; Manning, A. J.; Bauguitte, Stéphane; Pisso, Ignacio; Pyle, J. A.

doi:10.1002/2017jd026626

Cited by 24 publications

(19 citation statements)

References 55 publications

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“…An alternate explanation would assign a broad elevated baseline concentration to the offshore source(s) plus an additional unknown local emission event at closer range. This mixed source hypothesis parallels recent studies of a North Sea offshore plume, much bigger in both spatial extent and measured flux, where methane isotope ratios suggested a mixture of oil and gas and other sources (Cain et al, 2017). With the current information currently available no robust conclusions can be drawn.…”

Section: Offshore Emissionssupporting

confidence: 80%

Methane emissions in the Netherlands: The Groningen field

Yacovitch

Neininger²,

Herndon

et al. 2018

Elementa: Science of the Anthropocene

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The Groningen natural gas field in the Netherlands – one of Europe’s major gas fields – deploys a “production cluster” infrastructure with extraction, some processing and storage in a single facility. This region is also the site of intensive agriculture and cattle operations. We present results from a multi-scale measurement campaign of methane emissions, including ground and airborne-based estimates. Results are compared with inventory at both the facility and regional level.Investigation of production cluster emissions in the Groningen gas field shows that production volume alone is not a good indicator of whether, and how much, a site is emitting methane. Sites that are nominally shut down may still be emitting, and vice-versa. As a result, the inventory emission factors applied to these sites (i.e. weighted by production) do a poor job of reproducing individual site emissions. Additional facility-level case studies are presented, including a plume at 150 ± 50 kg CH4 hr–1 with an unidentified off-shore emission source, a natural gas storage facility and landfills.Methane emissions in a study region covering 6000 km2 and including the majority of the Groningen field are dominated by biogenic sources (e.g. agriculture, wetlands, cattle). Total methane emissions (8 ± 2 Mg hr–1) are lower than inventory predictions (14 Mg hr–1) but the proportion of fossil fuel sources is higher than indicated by the inventory. Apportionment of methane emissions between thermogenic and biogenic source types used ethane/methane ratios in aircraft flasks and ground-based source characterization. We find that emissions from the oil and gas sector account for 20% of regional methane, with 95% confidence limits of (0%, 51%). The experimental uncertainties bound the inventory apportionment of 1.9%, though the central estimate of 20% exceeds this result by nearly 10 times. This study’s uncertainties demonstrate the need for additional research focusing on emissions apportionment, inventory refinement and offshore platforms.

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Section: Offshore Emissionssupporting

confidence: 80%

Methane emissions in the Netherlands: The Groningen field

Yacovitch

Neininger²,

Herndon

et al. 2018

Elementa: Science of the Anthropocene

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“…Methane emitted by organic waste is enriched as a result of methane oxidation after its production in the anoxic layer. Here, a value of −52 ‰ was used, in agreement with Chanton et al (1999) (−58 ‰ to −49 ‰) and close to what was found by Bergamaschi et al (1998) (−55 ‰). The emissions of those two sources are an order of magnitude lower than anthropogenic emissions from fossil fuel production; thus, their isotopic signature does not significantly impact the isotopic signal at observation sites.…”

Section: Source Isotopic Signaturessupporting

confidence: 84%

Assessment of the theoretical limit in instrumental detectability of northern high-latitude methane sources using δ13CCH4 atmospheric signals

et al. 2019

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Abstract. Recent efforts have brought together bottom-up quantification approaches (inventories and process-based models) and top-down approaches using regional observations of methane atmospheric concentrations through inverse modelling to better estimate the northern high-latitude methane sources. Nevertheless, for both approaches, the relatively small number of available observations in northern high-latitude regions leaves gaps in our understanding of the drivers and distributions of the different types of regional methane sources. Observations of methane isotope ratios, performed with instruments that are becoming increasingly affordable and accurate, could bring new insights on the contributions of methane sources and sinks. Here, we present the source signal that could be observed from methane isotopic 13CH4 measurements if high-resolution observations were available and thus what requirements should be fulfilled in future instrument deployments in terms of accuracy in order to constrain different emission categories. This theoretical study uses the regional chemistry-transport model CHIMERE driven by different scenarios of isotopic signatures for each regional methane source mix. It is found that if the current network of methane monitoring sites were equipped with instruments measuring the isotopic signal continuously, only sites that are significantly influenced by emission sources could differentiate regional emissions with a reasonable level of confidence. For example, wetland emissions require daily accuracies lower than 0.2 ‰ for most of the sites. Detecting East Siberian Arctic Shelf (ESAS) emissions requires accuracies lower than 0.05 ‰ at coastal Russian sites (even lower for other sites). Freshwater emissions would be detectable with an uncertainty lower than 0.1 ‰ for most continental sites. Except Yakutsk, Siberian sites require stringent uncertainty (lower than 0.05 ‰) to detect anthropogenic emissions from oil and gas or coal production. Remote sites such as Zeppelin, Summit, or Alert require a daily uncertainty below 0.05 ‰ to detect any regional sources. These limits vary with the hypothesis on isotopic signatures assigned to the different sources.

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“…This increase is largely driven by anthropogenic activities though uncertainties exist in the magnitude of individual source sectors and sinks (Turner et al, 2019). Observatories have been set up around the world to track trends in CH 4 concentrations (de Coninck et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

Methane emissions from oil and gas platforms in the North Sea

et al. 2019

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Abstract. Since 1850 the concentration of atmospheric methane (CH4), a potent greenhouse gas, has more than doubled. Recent studies suggest that emission inventories may be missing sources and underestimating emissions. To investigate whether offshore oil and gas platforms leak CH4 during normal operation, we measured CH4 mole fractions around eight oil and gas production platforms in the North Sea which were neither flaring gas nor offloading oil. We use the measurements from summer 2017, along with meteorological data, in a Gaussian plume model to estimate CH4 emissions from each platform. We find CH4 mole fractions of between 11 and 370 ppb above background concentrations downwind of the platforms measured, corresponding to a median CH4 emission of 6.8 g CH4 s−1 for each platform, with a range of 2.9 to 22.3 g CH4 s−1. When matched to production records, during our 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 (i.e. the sum of platforms' emission fluxes weighted by the sum of the platforms' production), we 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 we measured to be 0.13 % of gas production, with most of their emissions coming from gas flaring and offshore oil loading, neither of which was taking place at the time of our 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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A cautionary tale: A study of a methane enhancement over the North Sea

Cited by 24 publications

References 55 publications

Methane emissions in the Netherlands: The Groningen field

Methane emissions in the Netherlands: The Groningen field

Assessment of the theoretical limit in instrumental detectability of northern high-latitude methane sources using <i>δ</i><sup>13</sup>C<sub>CH4</sub> atmospheric signals

Methane emissions from oil and gas platforms in the North Sea

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A cautionary tale: A study of a methane enhancement over the North Sea

Cited by 24 publications

References 55 publications

Methane emissions in the Netherlands: The Groningen field

Methane emissions in the Netherlands: The Groningen field

Assessment of the theoretical limit in instrumental detectability of northern high-latitude methane sources using &lt;i&gt;δ&lt;/i&gt;&lt;sup&gt;13&lt;/sup&gt;C&lt;sub&gt;CH4&lt;/sub&gt; atmospheric signals

Methane emissions from oil and gas platforms in the North Sea

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Assessment of the theoretical limit in instrumental detectability of northern high-latitude methane sources using <i>δ</i><sup>13</sup>C<sub>CH4</sub> atmospheric signals