GEOCHEMICAL EVALUATION OF OIL SEEPS FROM FALCON BASIN, WESTERN VENEZUELA, 2001

This study includes an evaluation of ten oil seeps samples from Falcon Basin, Western Venezuela,  in order to establish possible correlation between them, and to deduce the possible type of kerogen that originate them. We determine the thermal maturity grade, migration, water washing and biodegradation principally. We used compounds analysis from the aromatic fraction, and nitrogen compounds, by which we can obtain original information about their geochemistry evolution.

The samples collected were fractionated in Saturates, Aromatic, Resins and Asphaltens, by liquid chromatography.

The nitrogen basic fraction was isolated from the whole oil, and were analysed by GC/MS-MS.

According with the biomarkers analysis, we could evidence the partial or total absent of some compounds in the oil seeps, with that we could infer that the seeps Ventura, Mauroa, Grande, Quirós and Mina (Western Falcon) present high biodegradation levels, while the Seeps Acosta, Riecito, Cosme and Cumarebo (Eastern Falcon) were less affected by the biodegradation or another process, product of weathered surface process.

Through nitrogen compounds, according the relation benzocarbazoles a and c, we could deduce tha possibility that Mauroa Seep had the biggest relative migration distance, while Quirs seep had the smallest migration distance, from the source rock.

According to the distribution of aromativ compuonds we could evidence that the samples Cosme and Acosta had the biggest contribution of terrestial organic matter, next there were the samples Cumarebo, Hombre Pintado and Riecito.

Through the aromatic compouns analised, all the oil seeps studied were found in the maximum peak of oil generation, and it reflects high maturity level, indicating that they were generated by a source rock in ahigh maturity stage.

According the naphtalenes distribution we could deduce that the samples Acosta, Riecito and Cosme, were associated possibly to Kerogen II.

The oil seeps samples studied come from various source rocks. And had the followings correlationxs between oil seeps-oil seps, using the differences and similarities between the samples: The seeps Grande, Quiros and Mauroa, Ventura and Mauroa; Cosme, Acosta and Riecito; Hombre Pintado, Cumarebo and Riecito. Those correlations were obtained by convencional method and with the application of multivariate statistic.