Analysis of water-in-oil emulsion hyperspectral signature: contribution of pool experiment

摘要

Going on toward the objectives of NAOMI (New Advanced Observation Method Integration) research project, Total and ONERA are working on hyperspectral imagery to detect, characterize and quantify spills at sea. An important part of this work consists in building a database of oil and water-in-oil emulsion reflectance. This database of spectral signatures will be used to analyze the properties of a slick thanks to hyperspectral imagery in the VNIR+SWIR domain and spectral matching techniques. The characterization of the hydrocarbons performed first in laboratory has been completed with a pool experiment. The aim of such an experiment is to measure more realistic spectral signatures in term of background and thickness than in laboratory. Starting from the sample of the emulsion released at sea during NOFO 2015 experiment, emulsion has been remixed once for laboratory measurements and second for the pool experiment. Indeed, its reflectance was measured in the laboratory but for a quite large thickness and it was difficult to predict how the thickness would be once the emulsion freely spread at the water surface. Moreover, depending on the thickness, a signature mixing emulsion and water background could be obtained. In such case, the signatures measured in the lab and in the pool may differ significantly. As a consequence, the use of spectral signature measured in laboratory may give poor spectral matching results. In order to get the answers, a pool experiment, piloted by ONERA in the frame of the NAOMI collaboration with TOTAL, was organized at CEDRE in Brest (France). CEDRE's pool is usually used for oil recovery equipment testing or people operating such equipment training. Thus, the pool is large (1900 m~2), fairly deep (3 m) and filled with ocean water. Known volumes of several products, including the NOFO 2015 emulsion, were successively poured into a delimited area within the pool. Two hyperspectral cameras put on board a cherry picker located on the pool quay we