Geochemical approach to evaluate a prospect in the Eastern Maracaibo Basin, Venezuela

Martínez, Alejandro¹, Elias Kassabji², Marcias González¹, Jacqueline Grobas² (1) PDVSA Intevep, Los Teques, Venezuela (2) PDVSA EP, Puerto La Cruz, Venezuela

To reevaluate all elements of the petroleum system (source rock, reservoirs, seals and overburden rocks) and their processes (trap formation, generation, migration and accumulation), in the Eastern Maracaibo Basin, a classic geochemical characterization of 24 crude oils (SARA; GC; GC-MS) and 348 rock samples (Rock eval 6 Pyrolisis and Organic petrography) was done. The results allowed to determine that the potential of petroleum generation of Cretaceous in the present is gone. However, recent studies display new structurals features at the North of the area, favorable for the formation of traps and migration pathways for the hydrocarbons accumulation. According with the results of this work, this accumulation was generated and expelled between 0.95 and 1.1% Ro.

The results of the biomarkers analysis showed that the crude oils comes from different lithologicals facies associate from different organic facies corresponding to the same source rock (La Luna Formation). At North they are associated mainly with a carbonatic contribution, whereas to the South they came from a more siliciclastic contribution. Futhermore different levels of biodegradation were observed from postcumulative alteration processes inside the reservoirs, caused possibly by the lack of seals structures or the low effectiveness of seals during the accumulation. The presences of these biodegraded crude oils mixed with crude oils that exhibits part of their original molecular characteristics, was interpreted as two possible sources of drainage associated from two phases of deformation in the study area, this allows to infer the presence of possible important accumulations in an area barely explored within a mature basin.