Ryerson Thomas B.

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Ryerson
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Thomas B.
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  • Article
    Flow rate and source reservoir identification from airborne chemical sampling of the uncontrolled Elgin platform gas release
    (Copernicus Publications on behalf of the European Geosciences Union, 2018-03-27) Lee, James D. ; Mobbs, Stephen D. ; Wellpott, Axel ; Allen, Grant ; Bauguitte, Stephane J.-B. ; Burton, Ralph R. ; Camilli, Richard ; Coe, Hugh ; Fisher, Rebecca E. ; France, James L. ; Gallagher, Martin ; Hopkins, James R. ; Lanoiselle, Mathias ; Lewis, Alastair C. ; Lowry, David ; Nisbet, Euan G. ; Purvis, Ruth M. ; O'Shea, Sebastian ; Pyle, John A. ; Ryerson, Thomas B.
    An uncontrolled gas leak from 25 March to 16 May 2012 led to evacuation of the Total Elgin wellhead and neighbouring drilling and production platforms in the UK North Sea. Initially the atmospheric flow rate of leaking gas and condensate was very poorly known, hampering environmental assessment and well control efforts. Six flights by the UK FAAM chemically instrumented BAe-146 research aircraft were used to quantify the flow rate. The flow rate was calculated by assuming the plume may be modelled by a Gaussian distribution with two different solution methods: Gaussian fitting in the vertical and fitting with a fully mixed layer. When both solution methods were used they compared within 6 % of each other, which was within combined errors. Data from the first flight on 30 March 2012 showed the flow rate to be 1.3 ± 0.2 kg CH4 s−1, decreasing to less than half that by the second flight on 17 April 2012. δ13CCH4 in the gas was found to be −43 ‰, implying that the gas source was unlikely to be from the main high pressure, high temperature Elgin gas field at 5.5 km depth, but more probably from the overlying Hod Formation at 4.2 km depth. This was deemed to be smaller and more manageable than the high pressure Elgin field and hence the response strategy was considerably simpler. The first flight was conducted within 5 days of the blowout and allowed a flow rate estimate within 48 h of sampling, with δ13CCH4 characterization soon thereafter, demonstrating the potential for a rapid-response capability that is widely applicable to future atmospheric emissions of environmental concern. Knowledge of the Elgin flow rate helped inform subsequent decision making. This study shows that leak assessment using appropriately designed airborne plume sampling strategies is well suited for circumstances where direct access is difficult or potentially dangerous. Measurements such as this also permit unbiased regulatory assessment of potential impact, independent of the emitting party, on timescales that can inform industry decision makers and assist rapid-response planning by government.
  • Preprint
    Chemical data quantify Deepwater Horizon hydrocarbon flow rate and environmental distribution
    ( 2011-11-11) Ryerson, Thomas B. ; Camilli, Richard ; Kessler, John D. ; Kujawinski, Elizabeth B. ; Reddy, Christopher M. ; Valentine, David L. ; Atlas, Elliot ; Blake, Donald R. ; de Gouw, Joost ; Meinardi, Simone ; Parrish, David D. ; Peischl, Jeff ; Seewald, Jeffrey S. ; Warneke, Carsten
    Detailed airborne, surface, and subsurface chemical measurements, primarily obtained in May and June 2010, are used to quantify initial hydrocarbon compositions along different transport pathways – in deep subsurface plumes, in the initial surface slick, and in the atmosphere – during the Deepwater Horizon (DWH) oil spill. Atmospheric measurements are consistent with a limited area of surfacing oil, with implications for leaked hydrocarbon mass transport and oil drop size distributions. The chemical data further suggest relatively little variation in leaking hydrocarbon composition over time. While readily soluble hydrocarbons made up ~25% of the leaking mixture by mass, subsurface chemical data show these compounds made up ~69% of the deep plume mass; only ~31% of deep plume mass was initially transported in the form of trapped oil droplets. Mass flows along individual transport pathways are also derived from atmospheric and subsurface chemical data. Subsurface hydrocarbon composition, dissolved oxygen, and dispersant data are used to provide a new assessment of release of hydrocarbons from the leaking well. We use the chemical measurements to estimate that (7.8±1.9) x106 kg of hydrocarbons leaked on June 10, 2010, directly accounting for roughly three-quarters of the total leaked mass on that day. The average environmental release rate of (10.1 ± 2.0) x106 kg/day derived using atmospheric and subsurface chemical data agrees within uncertainties with the official average leak rate of (10.2 ± 1.0) x106 kg/day derived using physical and optical methods.