NOx Emissions from Oil and Gas Production in the North Sea

Abstract:

North Sea oil is a mixture of hydrocarbons, comprising liquid petroleum and natural gas, produced from petroleum reservoirs beneath the North Sea. As of January 2015, the North Sea is the world's most active offshore drilling region with 173 rigs drilling. During the summer of 2015, a series of survey flights took place on the UKs FAAM BAe 146 research aircraft with the primary aim to assess background methane (and other hydrocarbons) levels in the drilling areas of the North Sea. Also measured were Nitrogen Oxides (NO and NO₂), which are emitted from almost all combustion processes and are a key air pollutant, both directly and as a precursor to ozone (O₃). The oil and gas platforms in the North Sea are often manned and require significant power generation and support vessels for their continued operation, processes that potentially emit significant amounts of NO_x into an otherwise relative clean environment. During these flights we were able to measure the NO­­­_x (and any subsequently produced O₃) emitted from specific rigs, as well as the NO_x levels in the wider North Sea oil and gas production region (see figure for example). NO_x mixing ratios of <10 ppbv were frequently observed in plumes, with significant perturbation to the wider North Sea background levels. NO_x emissions from the rigs are point sources within the UKs National Atmospheric Emission Inventory (NAEI) and the measurements taken in plumes from individual rigs are used to assess the accuracy of these estimates.