Geochemical correlation between oils and rocks of the petroleum system of the Santa Elena peninsula and the gulf of Guayaquil

The southeastern of the Ecuadorian coast is a traditionally oil producing region, but the petroleum system has not been defined yet. The proposed main source rocks are Seca and Socorro formations (Eocene) and Dos Bocas and Subibaja formations (Miocene). In order to contribute new elements to the knowledge of the area, both crude and rock from onshore and offshore fields were studied, using geochemical techniques that include gas chromatography and carbon isotopes. Parameters such as the Carbon Preference Index (IPC), Pri/n-C-17 and Phy/n-C-18 ratios and the isotopic distributions, indicate that onshore oils are genetically differentiated from offshore oils and are associated with a detritic source rock with mixed organic matter, deposited in a suboxic environment, consistent with the distal area of an estuarine complex. On the other hand, the rocks analyzed are thermally immature and with very low generating potential, so that they cannot be correlated with the crude analyzed, as was traditionally done.