Measuring methane emissions from oil and gas platforms in the North Sea

Abstract. Recent studies suggest oil and natural gas production facilities in North America may be underestimating methane (CH4) emissions during extraction. This, coupled with unusually high CH4 mole fractions observed at coastal sites during onshore winds in the UK, suggests CH4 emissions from oil and gas extraction activities in the North Sea could be higher than previously reported. To investigate if these coastal CH4 enhancements could have come from oil and gas production platforms, we use near-source measurement techniques to estimate CH4 emissions from eight oil and gas production platforms in the North Sea. We estimate the mean CH4 emission from the eight platforms to be 10.1 g CH4 s−1, with a range of 1.1 to 25.0 g CH4 s−1. When matched to production records, individual platforms lose between 0.01 % and 1.58 % of gas production with an average loss of 0.61 % of gas production. However, when the measured platforms are considered collectively, i.e. when the total measured emission is compared to total production of the platforms measured, the CH4 loss is estimated at 0.27 % of gas production. These calculated ranges are at least double the most recently reported loss rates for these platforms, which are currently estimated at 0.13 % of gas production. In fact, the vast majority of reported emissions are due to gas flaring and offshore oil loading, neither of which was taking place at the time of these measurements. If emissions measured here resulted from leakage during normal operation, they represent significant additional emissions (at least 0.27 % of production) above previous estimates of CH4 leakage from off-shore oil and gas production platforms. These emissions are not explicitly included in UK emission inventories. Further research to determine CH4 leakage from all operations occurring at off-shore oil and gas platforms, and how to include them in national emission inventories, is needed.