Methane Emission from Upstream Storage Tanks: Measurement and Quantification

Abstract Climate change has emerged as one of the most severe challenges in the world. Greenhouse gas (GHG) emission was assumed to be the root cause. Carbon dioxide and methane are the most important GHG, while methane has a shorter atmospheric lifetime and higher global warming potential. Methane abatement was regarded as one of the most important measures to limit near-term global warming. Oil and gas (OG) production processes are key methane emissions sources, with storage tanks making significant contribution. Methane emission from upstream storage tanks in an OG field was confirmed using a portable flame ionization detector (FID) and measured with a full range sampler in China. The component and facility based emission characteristics were studied and compared. More than 70 storage tanks, including fixed roof tanks (FRT), internal floating roof tanks (IFRT) and external floating roof tanks (EFRT) distributed in production wells and processing plants, were measured. The leak detection results suggested nearly all tanks were suffering from methane emission problem and 147 leaking or emission points were identified with emission rate ranging from 0.0086×10-3 kg/h to 3.08 kg/h. The EFRT has higher facility-level emission rate than IFRT. In terms of FRT, the facility-level emission rate has a skewed distribution, ranging from 0.015 kg/h to 4.48 kg/h for working loss process. It was observed that 10 % tanks contribute 44.6 % of the total rate during working loss process and 13.3 % tanks making a 58.8 % share. The standing loss process follows similar law, with emission rate ranging from 0.042×10-3 kg/h to 0.088 kg/h. The total standing loss emission rate reaches 0.44 kg/h, with 22.6% tank having 64.5% contribution. The estimated average value of emission rate was 1.13 kg/h (EFRT), 0.05 kg/h (IFRT), 0.72 kg/h (FRT, working loss) and 0.014 kg/h (FRT, standing loss) respectively. The annual emission amount was estimated.