Caracterización geoquímica del petróleo de los resevorios de la Fm Napo del Cretácico (Ecuador) y su relació con las lutitas intercaladas como roca generadora de hidrocarburos.

• Autores: Jenny Estupiñan letamendi, Albert Permanyer Bastardas
• Localización: Geogaceta, ISSN 0213-683X, Nº. 46, 2009, págs. 155-158
• Idioma: español
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• Resumen

  • The Napo Formation from the Cretaceous age is located in the Oriente basin in Ecuador and is composed of limestones, shales, and sandstones, the «U» and «T sandstones», which are the most important reservoirs in the basin. The formation was deposited in fluvial, transitional and marine environments, and their correlation with the sequence stratigraphy may be associated with the fluctuation of the eustatic sea level. This work presents the analyses of the organic composition and the thermal maturity of the shales interbedded in the sandstones reservoir. Furthermore, the geochemical characterization of oils from the «U» and «T» reservoirs was preformed. The analyses were performed to establish the contribution of the shale as a source rock in the generation of the hydrocarbons. The spatial trend of the TOC in the shales varies from 1,78% in the Eden-10 well, located in the eastern part of the basin to 0,56% in Jivino-1 well located in the center of the basin. The hydrogen index (IH) varies from 116 to 414 mg/g, and the thermal maturity expressed as Tmax shows values of 445ºC. Oil studies show the relationship between tricyclic terpanes (C20/C23) and trisnorhopane/trisnoneohopane (Ts/Tm) among others biomarkers. These data suggest a marine origin and the thermal maturity is compatible with foundin thats the shale shows (reflectance equivalent of 0,6% - 0,9%, deduced from the analyses of the regular steranes isomerization). The interpretation of all the analyses suggests that the interbedded shales in the «U» and «T» sandstones could have contributed to the source of the hydrocarbon oil in the Oriente basin.