Methane Emissions from Offshore Oil and Gas Platforms in the Gulf of Mexico

Abstract

Shipboard measurements of offshore oil and gas facilities were conducted in the Gulf of Mexico in February 2018. Species measured at 1 s include methane, ethane, carbon-13 ( 13 C) and deuterium (D) isotopes of methane, and several combustion tracers. Significant variability in the emission composition is observed between individual sites, with typical ethane/methane ratios around 5.3% and 13 C and D methane isotopic compositions around −40 and −240‰, respectively. Offshore plumes were spatially narrower than expectations of the plume width based on terrestrial atmospheric stability classes; a modified Gaussian dispersion methodology using empirically measured horizontal plume widths was used to estimate the emission rates. A total of 103 sites were studied, including shallow and deepwater offshore platforms and drillships. Methane emission rates range from 0 to 190 kg/h with 95% confidence limits estimated at a factor of 10. The observed distribution is skewed with the top two emitters accounting for 20% of the total methane emissions of all sampled sites. Despite the greater throughput of the deepwater facilities, they had moderate emission rates compared to shallow-water sites. Analysis of background ethane enhancements also suggests a source region in shallow waters. A complete 1 s measurement database is published for use in future studies of offshore dispersion.

Remote sensing of methane leakage from natural gas and petroleum systems revisited

“…combined energy production of 2456 kBOE d −1 . Due to its shape with almost linearly arranged sources and the proximity to significant offshore sources in the Gulf of Mexico (Yacovitch et al, 2020), the introduced approach is challenging in the case of Eagle Ford. To avoid that the background is impacted by the offshore sources, wind directions blowing towards the northwest (between North and West) were additionally excluded.…”

Global geographic variability in freshwater methane hydrogen isotope ratios and its implications for emissions source apportionment and microbial biogeochemistry

“…However, based on the analysis above, we argue that the large variability in atmospheric δ 2 H-CH 4 is an important constraint on global CH 4 budgets that has been under-utilized, but that has strong potential to complement δ 13 C-CH 4 measurements and modeling. This is especially true now that advances in measurement technology are making an expansion of both atmospheric and source δ 2 H-CH 4 measurements increasingly practical (Chen et al, 2016;Röckmann et al, 2016;Yacovitch et al, 2020). Based on our dataset and analysis, atmospheric δ 2 H-CH 4 measurements could be especially valuable in identifying increasing high-latitude freshwater CH 4 emissions resulting from permafrost thaw (Koven et al, 2011).…”

“…Applying additional isotopic tracers to atmospheric CH 4 monitoring has the potential to greatly improve our understanding of CH 4 sources and sinks (Turner et al, 2019;Saunois et al, 2019). In particular, recent technological developments have the potential to make atmospheric δ 2 H-CH 4 measurements more practical at higher spatial and temporal resolution (Yacovitch et al, 2020;Chen et al, 2016;Röckmann et al, 2016;Townsend-Small et al, 2016). δ 2 H-CH 4 measurements have proven useful in understanding past CH 4 sources in ice-core records (Bock et al, 2010;Whiticar and Schaefer, 2007;Bock et al, 2017;Mischler et al, 2009), but have seen only limited use in modern atmospheric CH 4 budgets (Rice et al, 2016;Kai et al, 2011), in part because of loosely constrained source terms, as well as relatively sparse atmospheric measurements.…”

Mobile atmospheric measurements and local-scale inverse estimation of the location and rates of brief CH<sub>4</sub> and CO<sub>2</sub> releases from point sources

“…Some major improvements can be foreseen to strengthen the measurement and inversion framework. The general tendency of the transport and inversion framework to underestimate the release rates (compensated by its tendency to overestimate the distance between the source and the plume crosssections when using a logarithmic cost function) can actually be related to the source height (Yacovitch et al, 2020). In the inversion computations, this height is fixed to the actual source height for the controlled releases.…”