Resumo

QUERO, Vanessa et al. Petroleum source rock evaluation of the La Luna Formation at Táchira state sections, Venezuela. Rev. Téc. Ing. Univ. Zulia [online]. 2007, vol.30, n.Especial, pp.326-335. ISSN 0254-0770.

Biomarkers were applied to determine organic matter type, sedimentation environment and thermal maturity in the La Luna Formation, La Chiriri and La Molina sections, Táchira state, Venezuela. The maltenes of bitumen from thirteen outcrop samples were separated in saturate and aromatic hydrocarbons, and resins (SAR). The first two fractions were analyzed by gas chromatography-mass spectrometry (GC-MS). A bimodal type n-alkanes distribution was found, revealing mixed organic matter (marine and terrestrial). The pristane/phytane ratios indicate suboxic-disoxic conditions. A low resolution was obtained from analysis by GC-MS of saturate (terpanes and steranes, m/z 191, 217 and 218); and aromatic fractions (mono and triaromatic steroids, m/z 231 and 253), due to the advanced state in thermal maturity. Non-biological markers (phenanthrenes and dibenzotiophenes), CPI (Carbon Preference Index), OEP (Odd-to-Even Predominance), pristane/n-C17 and phytane/n-C18, phenanthrene analysis, and calculated vitrinite reflectance (Rc%), point to an overmature source rocks.

Palavras-chave : Biomarkers; La Luna Formation; Táchira; bitumen.