Abstract

ESCOBAR, Marcos et al. Differential biodegradation of Sierra de Perijá foothill marine and thermally mature oil seeps, Venezuela. Rev. Téc. Ing. Univ. Zulia [online]. 2007, vol.30, n.Especial, pp.360-369. ISSN 0254-0770.

A geochemical study on 11 oil seeps samples collected in the Cachirí sector, Geologic Leaf Tulé, associated to the Tiger fault was performed, analyzing hopanes, steranes, n-alkanes, acyclic isoprenoids and aromatic steroids. These organic fluids have undergone contrasting biodegradation (partial loss of n-alkanes -level 2- but simultaneous bacterial affectation on isoprenoids, steranes and hopanes -level 6-). The oil seeps have been generated by a calcareous source rock deposited in a marine palaeoenvironment of reducing character. Their source rock, possibly the La Luna Formation of the Cretaceous from the Lake of Maracaibo Basin, reached a thermal maturity level close to the maximum of the oil window. All this evidence, plus the published models of petroleum generation for this unit in the study area, supports to the proposal of an event of generation and hydrocarbon migration in recent times, and aims towards the necessity to review possibly adjacent petroleum traps.

Keywords : iodegradation; biomarkers; La Luna Formation; Maracaibo Lake Basin.