Abstract

PORTILLO, Edgar et al. Origin, thermal maturity and alteration level of oil seeps in the Perija range foothills, Venezuela  . Rev. Téc. Ing. Univ. Zulia [online]. 2008, vol.31, n.Especial, pp.97-106. ISSN 0254-0770.

In order to establish source rock, physicochemical sedimentary environment conditions and alteration processes of oil seeps located at the Alturitas oilfield of the Machiques Municipality, Zulia State, Venezuela, located at the foothills of the Sierra de Perijá, two oil seep samples were collected and analyzed including soxhlet extraction, SARA isolation, gas chromatography coupled to mass spectrometry (GC-MS) analysis of saturated and aromatic hydrocarbons fractions, and biomarkers distribution evaluation. Results indicate that oil seeps under study were generated from carbonatic source rock; organic precursor material was a Kerogen Type II deposited in a marine environment under strong anoxic conditions. These oil seeps have been affected by moderate biodegradation process. The integration of both, obtained results and literature reviewing, allow to infer that these organic fluids have been generated by the Cretaceous La Luna Formation from the Maracaibo Lake Basin. Geochemical parameters of C15+ biomarkers indicate that the source rock of these oil seeps had reached an oil window thermal maturity stage [1]. 

Keywords : Oil seeps; Maracaibo Lake Basin; Alturitas; biomarker; La Luna Formation.