Satellite determination of API gravity and SARA components of offshore petroleum seeps

Abstract

Crude oils can be classified based on their API gravity or their SARA components (i.e. saturated, aromatics, resins, and asphaltenes). This work evaluates the possibility to infer such oil's characteristics by means of reflectance spectroscopy and multispectral and hyperspectral imagery. Reflectance spectra (0.35-2.5μm) of oils and films of oil on water were measured under laboratory conditions using a high-resolution spectroradiometer. Multivariate statistics (i.e. principal component and partial least square analysis) were used to evaluate these spectra, taking into consideration both the spectral resolution at laboratory measurements (2150 bands) and the spectral resolution offered by orbital sensors (i.e. Hyperion (220 bands) and ASTER (9 bands)). The statistical approach yielded predictive models based on the correlation of oil composition and its spectral response, allowing remote assessment of the oil quality of a particular seepage from the Campos Basin (Brazil). This oil has a known API gravity ranging between 19-22, 40-49% mass/mass of saturated, 33-25 of aromatics, 20-28 of resins and 3-1.5 of asphaltenes. The remotely retrieved values based on the spectral response of the seep are within the actual range and are remarkably similar: API gravity of 19.6 and 45.38% mass/mass of saturated, 26.91 of aromatics, 24.61 of resins and 2.14 of asphaltenes. This result indicates the potential of this methodology, first proposed in this work, for the indirect inference of API gravity and SARA composition based on remote sensing data and techniques. © 2012 Sociedade Brasileira de Geofísica.