August 3, 2012
Based on the previous estimates of the gas leak flow, an accurate estimate of the global quantity of hydrocarbons released is now established to 3096 tonnes of gas and 3076 tonnes of condensate. These figures have been officially reported to the HSE.
The majority of the condensate evaporated, leaving an estimated quantity of 407 tonnes on the surface of the sea, as reported to the DECC. This sheen was dispersing naturally and disappeared completely within days, making the overall environmental impact of the incident minimal.
May 10, 2012
New decline of the gas leak flow rate on Elgin G4
Observations made during the daily over-flights of the area by Oil Spill Response Limited (OSRL) confirm visual inspections on the Elgin complex itself, indicating that the leakage rate of gas continues to diminish. This is now estimated at around 0.5 kg/second* of gas, down from the initial estimates of 2.0 kg/second in the first days of the Elgin incident.
* approximately 50,000 m3/day
April 20, 2012
Elgin G4: Decrease of the gas leak flow rate
In the first days after the beginning of the leak the gas flow rate was estimated at 2kg/s* initially based on modeling. This first estimate was confirmed by the atmospheric measurements undertaken by a scientific flight by NCAS (National Centre for Atmospheric Science) on March 30. The method used during this flight was based on the measurement of methane atmospheric concentrations at various points within the gas dispersion plume; these concentrations together with wind conditions were then used to estimate the gas flow rate. Methane is considered to be a valid indicator since it is known to be the main component of the natural gas emitted by the leak. Since these initial estimates have been made, several methods have been used to re-assess regularly the gas flow rate, including additional modeling, infrared temperature measurements of the conductor pipe, visual observations by the teams during their visits on Elgin, and further NCAS scientific flights on April 3 and April 17. All these methods give converging results which indicate that the gas flow rate has decreased. To date it is estimated to be within a range between 0.5 kg/s and 1 kg/s**, around one third of the first estimate.
In addition, the measurements done during the NCAS flights show a close correlation between the known composition of the Hod formation gas and the composition of the gas plume.
Further NCAS flights are planned to continue to monitor the leak rate.
* approximately 200,000 m3/day
** approximately 50,000 – 100,000 m3/day”