Caracterización geoquímica de rocas en una secuencia cretácica de la cuenca del lago de maracaibo

The Maracaibo basin has been catalogued as one of the most important basins worldwide, the La Luna Formation (FLL) being the main source rock. Nonetheless, other formations have been defined as source rocks of secondary importance. This is the case of some of the formations included in the Cogollo group (Apon and Maraca formations). The purpose of this study was to determine and compare geochemical parameters in order to characterize the Cretaceous sequence represented in the well core 26D-2. In order to do that, first a physical description of the samples was made, together with mineralogical analyses and the determination of the total carbon, inorganic (carbonate) and total organic carbon (TOC). Rock-Eval pyrolysis analyses were also made to determine the type of kerogen and the maturity range of the samples. The bitumen was extracted and separated into maltenes and asphaltenes. The maltene fraction was then separated in saturate and aromatic hydrocarbons and resins. To obtain both biomarkers and aromatic markers, a gas chromatography coupled with mass spectrometry (GC/MS) analysis was done. Lastly the asphaltene fraction was analyzed using gel permeation chromatography to determine the molecular weight in number (Mw) and in weight (Mw). Considering the results obtained through pyrolysis, biomarkers and aromatic markers, the Cretaceous sequence analyzed presented a mixed organic matter input, the sedimentary facies were marine, carbonatic and siliciclastic and the samples show an early to intermediate maturity range.