Articles | Volume 11, issue 3
Atmos. Meas. Tech., 11, 1725–1739, 2018
Atmos. Meas. Tech., 11, 1725–1739, 2018

Research article 27 Mar 2018

Research article | 27 Mar 2018

Flow rate and source reservoir identification from airborne chemical sampling of the uncontrolled Elgin platform gas release

James D. Lee1, Stephen D. Mobbs2, Axel Wellpott3, Grant Allen4, Stephane J.-B. Bauguitte5, Ralph R. Burton2, Richard Camilli5, Hugh Coe4, Rebecca E. Fisher6, James L. France6,7, Martin Gallagher4, James R. Hopkins1, Mathias Lanoiselle6, Alastair C. Lewis1, David Lowry6, Euan G. Nisbet6, Ruth M. Purvis1, Sebastian O'Shea3, John A. Pyle8, and Thomas B. Ryerson9 James D. Lee et al.
  • 1National Centre for Atmospheric Science, University of York, York, UK
  • 2National Centre for Atmospheric Science, University of Leeds, Leeds, UK
  • 3Facility for Airborne Atmospheric Measurements, Cranfield University, Bedford, UK
  • 4School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Manchester, UK
  • 5Department of Applied Ocean Physics and Engineering, Woods Hole Oceanographic Institution, Woods Hole, MA, USA
  • 6Department of Earth Sciences, Royal Holloway University of London, Egham, TW20 0EX, UK
  • 7School of Environmental Sciences, University of East Anglia, Norwich, UK
  • 8National Centre for Atmospheric Science, Department of Chemistry, University of Cambridge, Cambridge, UK
  • 9Chemical Sciences Division, Earth System Research Laboratory, NOAA, Boulder, CO, USA

Abstract. 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.

Short summary
This work describes measurements, made from an aircraft platform, of the emission of methane and other organic gases from an uncontrolled leak from an oil platform in the North Sea (Total Elgin). The measurements made helped the platform operators to devise a strategy for repairing the leak and serve as a methodology for assessing future similar incidents.