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Biomarkers as tools for determining the origin of oil emanations: The seepage oil of the La Libertad, Ecuador, August 2016

Abstract:

The Peninsula of Santa Elena (Ecuador) is known since colonial times for the presence of seepage oils. At the end of August 2016, a seepage oil appeared on a beach on the La Libertad Coastal Boulevard, near a fuel station. The field relationships, as well as the physicochemical characteristics of the oil emanation did not allow clarifying its probable anthropic nature. The aim of this work is to establish the origin of the seepage oil through the study of the distribution of biomarkers, for which representative samples were taken, fractionated by column chromatography, and analyzed the biomarkers distribution (n-and iso-alkanes, steranes and hopanes). The distribution of isoprenoids and the pristane / phytane relationship are pointing towards a genetic correlation with crude oils from nearby Ancon oilfield. On the other hand, the presence of tri-, tetra-and pentacyclic steranes and terpanes are incoherent with an anthropic origin, since their high molecular weight would prevent them from being found in the light fractions of a refined product of anthropic origin.