Predictions of maximum ground-level H2S concentrations resulting from two sour gas well blowouts

Alberta has recently experienced two sour gas well blowouts: Lodgepole and Claresholm. Sulphur emissions associated with the blowouts were about 1400 and 2 tonnes per day, respectively. The Lodgepole blowout was not only of much greater magnitude but also lasted significantly longer than the Claresholm blowout (67 vs. 4 days). Special air quality monitoring with respect to H2S was conducted to assess impacts of the blowouts. Monitoring was especially extensive for the Lodgepole incident. Maximum observed ground-level H2S concentrations were compared to predictions obtained using a Gaussian model which makes allowance for the effects of sonic exit velocity on plume spread and the effects of wind shear on plume transport. There was appreciable agreement between predicted and observed values.