Título: Applying Uncertainly to Modelling- A Maracaibo Basin Example

Autor: Titus, M. W.; R. J. Coskey; J. E. Leonard

Fuente: 8th Latin American Congress on Organic Geochemestry CD-ROM Memorias

Año: 2002

País de publicación: Colombia

Tipo de documento: CD-ROM Memorias

Resumen

The La Luna Formation (Turonian) has been considered the main hydrocarbon source the Colombia in northwestern South America, due to its organic richness (TOC ranging from 2 to 6%), high hydrocarbon source yields (S2 reaching up to 80 mg HC/g Rock) and the prevalence of type II kerogen. Particularly in the Colombian basins with commercial hydrocarbon production (Putumayo-PUT, Upper Magdalena Valley- UMV, Middle Magdalena Valley-MMV and Llanos Orientales-LLAO), most of petroleum geologist assumes that most of the petroleum was and expelled in the last 3 my. (During the Andean paroxysm) from the La Luna Formation buried in synclines adjacent to the main accumulations.

Based on this simple hydrocarbon charge model, reserves of about 8 BBO have been discovered up to now in Colombia. Nevertheless a refined assessment of the geochemical information acquired during the last 10 years suggests that the charge model is more complex. Such idea is mostly support by the following evidences: (a) a number of oils display biomarker characteristics that markedly contrast with the typical La Luna facies; (b) oil and gas characterization confirm mixture of hydrocarbon associated with different organic facies and/or different processes and (b) thermal maturity data and basin modeling results suggest that oil accumulations are surrounded by immature La Luna source rocks, which might indicate the prevalence of middle to long-distance (between 30 and 150 km) migration. The integration of rock and fluid data led to the proposition of an alternative HC charge model in which the Albian source rocks play a key role. Such model is supported by (a) the excellent hydrocarbon source rock potential displayed by such intervals in the PUT, UMV, MMV and Eastern Cordillera (EC) basins, (b) the high maturity level of the Albian deposits in some basins (e.g. EC and MMV;) in opposition to the low maturity level of the La Luna Formation in most of the areas with petroleum accumulations, and (c) positive correlation between oils from PUT, UMV and MMV and the Albian source facies. Application of this alternative model can significantly impact the evaluation of Colombian Petroleum Systems.