| Summary: | Methane (CH4) measurements are needed to better understand emissions from oil and gas sources. While many CH4 measurement studies have been done in Canada, they have not yet targeted offshore production from which low emission intensities are reported by industry. For this study, a Twin Otter aircraft was equipped with a Picarro 2210-i gas analyzer and an Aventech wind measurement system (AIMMs_30) to measure CH4 emissions from three oil production facilities in offshore Newfoundland and Labrador. Each facility was visited three times to account for daily variability. Measured concentrations were used to estimate emission rates and production-weighted intensities using two different methods, Top-down Emission Rate Retrieval Algorithm (TERRA), a mass conservation technique developed by Environment and Climate Change Canada, and a Gaussian Dispersion method (GD). Overall, TERRA mass balance-derived emission rates from our measurements were 2,890±3,027 m3 CH4 day-1(GD=7,721 m3 CH4 day-1), 3,738 ±7,199 m3 CH4 day-1 (GD=13,131 m3 CH4 day-1) and 7,975±4,453 m3 CH4 day-1 (GD=7,242 m3 CH4 day-1), respectively for SeaRose, Hibernia and Hebron. Based on results from both TERRA and Gaussian dispersion the weighted average was (considering number of samples in each method) 5,000 m3 CH4 day-1 (3.35 tonnes CH4 day-1), which is comparable to the federally reported estimate of 8,037 m3 CH4 day-1 of federal estimates, reported in 2019. Production-weighted methane intensities calculated using measured emission rates and reported oil production show that Canadian offshore production ranges from 0.4-2.2 MJ emitted/MJ produced, making it among the least methane-intensive oil produced in Canada.
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