Evaluation of GHG Emissions from Crude Oil and Condensate Storage Tanks

Dave Picard, Clearstone Engineering

The need for improvements to the methods used to estimate evaporation losses from storage tanks has been identified by both industry and regulators, and is seen as particularly important in Alberta given the predicted rapid expansion of the oil production sector and downstream oil transportation system in the coming decades. If successful, such methodological improvements are expected to ultimately lead to new verifiable, practical and implementable strategies for managing tank emissions, which would directly and indirectly benefit a broad range of stakeholders, domestically and internationally, including federal, provincial or regional air quality administrators and operators of storage tank farms throughout the upstream oil and gas industry and downstream refined products distribution sector. Moreover, federal and provincial regulators, as well as industry operators, would be equipped with more representative data concerning the quantification of fugitive inorganic compound (IOC), volatile organic compound (VOC), odour, and greenhouse gas (GHG) emissions from liquid storage tanks.

The focus herein is evaporation losses from fixed-roof storage tanks. A review of the existing American Petroleum Institute (API) algorithms for estimating evaporation losses from this type of tank has been conducted and specific unaccounted for effects have been identified. To help evaluate the significance of the emission contributions from these unaccounted for effects, a detailed monitoring program has been conducted on an underground gasoline storage tank at a retail gasoline station. The preliminary monitoring results and initial recommendations for enhancement of the existing evaporation loss algorithm for fixed-roof tanks are presented.