(1) Ecopetrol-ICP, Bucaramanga, Colombia
(2) Ecopetrol-AEX, Bogota, Colombia
(3) Gems Ltda, Bucaramanga, Colombia
ABSTRACT: Petroleum Generation and Thermal Regime in the Putumayo Basin, Colombia: New Insights from Basin Modeling and Geochemical Analyses in the Fold Belt
The Putumayo Basin is located in southern Colombia, representing the northern extension of the Oriente Basin (Ecuador). Part of the prolific Subandean province, the Putumayo Basin holds about 1,942MBOE in place. This paper reports how the integration of 1-D modeling results and geochemical data from the fold belt allowed a better understanding of petroleum generation and migration history in the Putumayo Basin. Molecular data of oil samples from the foothills area revealed a complex reservoir filling history, with at least two distinct migration pulses separated by a biodegradation event. A review of compositional and isotopic data of gas samples also points out to the mixing of hydrocarbon gases related to distinct migration pulses. Vitrinite reflectance data together with the results of the modeling performed with the GENEX complex tectonic module (GenTect) shows that the source rock is practically immature in the Putumayo foothills, even in the footwall of large thrust faults. The thermal and burial reconstruction of a pseudo well located in the present cordillera area suggests that the source rocks have started petroleum generation and expulsion during the Late Eocene/Oligocene. The oil and gas expelled during such period have migrated over 80km, reaching the present foreland area. The subsequent tectonic burial related to the Miocene/Pliocene Andean paroxysm probably accounts for the generation and/or remigration of thermally evolved hydrocarbons limited to the foothills.
AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado